200908066 九、發明說明 【發明所屬之技術領域】 本發明是關於在液晶或半導體、印刷電部板等的曝光 裝置的光源所使用的放電燈。尤其是關於，其封閉部藉由 以鉬（Mo)所構成的金屬箔所封閉的箔密封構造的放電燈。 【先前技術】 已知作爲放電燈的供電構造，電極與埋設於封閉管的 金屬箔連接，在金屬箔的另一端連接外部簧片，以達成導 通。這種具有箔密封構造的封閉部的放電燈，會因爲構成 封閉管的石英玻璃、與構成外部簧片的鉬（Mo)或鎢（W)的 膨脹係數不同，導致在封閉管與外部簧片的外周之間形成 細微的間隙。因爲該間隙的存在，大氣會進入到金屬箔或 外部簧片的表面，亮燈時會大幅促進金屬箔或外部簧片的 氧化。結果，封閉管會產生裂縫，金屬箔會熔斷，放電燈 的使用壽命會變短。 已知的在日本特開2004-3 1 9 1 77號公報所揭示的技術 ，爲解決該問題的手段。如第6圖所示，在液晶投射器所 使用的放電燈，在封閉管2與外部簧片9與金屬箔5的外 周所形成的間隙，充塡由铷氧化物（Rb20)所構成的密封物 22，在封閉管2的外端部附著有：以氧化硼與氧化鉍爲主 成分的低熔點玻璃20。藉由這種構造，能將封閉管2的外 端面的大氣的進入口封閉，而能阻隔外氣讓外部簧片9及 金屬箔5不會受到外氣的影響，而能提升封閉部的耐熱溫 -4- 200908066 度。並且，也能延長在高溫狀況下的使用壽命 〔專利文獻1〕 日本特開2004-319177公報 【發明內容】 〔發明欲解決的課題〕 可是，在曝光裝置的光源所使用的大型的放電燈’即 使是用上述構造，也就是在封閉管2與外部簧片9與金屬 箔5的外周所形成的間隙，充塡密封物22 ’而在封閉管2 的外端面附著低熔點玻璃20的構造，仍會產生無法防止 大氣進入這樣的問題。與在液晶投射器所使用的放電燈相 比，曝光裝置的光源所使用的放電燈較大’所以在外部簧 片9的外周所形成的間隙也變大。而且，曝光裝置的光源 所使用的放電燈，其封閉管2的外端面遠離電極，即使放 電燈點亮時溫度也不會變得更高。因此，低熔點玻璃20 在放電燈點亮時也維持著軟化點以下的溫度，而表面會產 生細微的裂縫。 在曝光裝置的光源所使用的大型放電燈，由於在低熔 點玻璃20的表面有細微的裂縫，所以只在封閉管2的外 端面附著低熔點玻璃20 ’無法完全將在外部簧片9的外周 所形成的間隙予以封閉，會因爲外氣流入導致金屬箱5氧 化。 本發明鑑於上述問題’要提供一種放電燈，是在曝光 -5- 200908066 裝置的光源所使用的放電燈，以低熔點玻璃封閉大氣的進 入口，能阻隔外氣避免金屬箔受到外氣影響。 〔用以解決課題的手段〕 第1發明，具有：在發光管的兩端連設有封閉管的放 電容器、在上述發光管的內部所配置的電極、在上述封閉 管的內部所配置的玻璃構件、在上述玻璃構件的外周面所 配置的金屬箔、以及與上述金屬箔電連接，插通於外部石 英管的貫穿孔的外部簧片；於上述外部石英管的貫穿孔的 內周面、與上述外部簧片的外周面之間所形成的間隙，具 有低熔點玻璃，在該貫穿孔的外端具有將該貫穿孔擴張所 設置的凹部。 第2發明，是針對第1發明，上述凹部，是藉由朝上 述貫穿孔的開口側擴張的錐狀面所形成。 第3發明，是針對第1發明，上述凹部，是藉由在上 述貫穿孔的內表面設置階段部所形成。 第4發明，是針對第1發明，上述低熔點玻璃，是環 狀的固體物，在上述外部簧片貫穿且配置於上述石英管的 外端面的狀態，藉由將其加熱熔融所形成。 第5發明，是針對第1發明，上述低熔點玻璃，是環 狀的固體物，在上述外部簧片貫穿且配置於上述凹部的內 部的狀態，藉由將其加熱熔融所形成。 第6發明，是針對第1發明，上述封閉管，藉由形成 爲從上述外部石英管的外端面朝管軸方向突出，而形成該 -6- 200908066 外部石英管的外周壁。 第7發明，是針對第1發明，在上述外部簧片的外周 面，在相當於上述間隙的部位形成捲箔。 〔發明效果〕 藉由第1發明的放電燈，藉由在貫穿孔的外端具有將 該貫穿孔擴張所設置的凹部，則能使低熔點玻璃進入到， 在外部石英管的貫穿孔的內周面與上述外部簧片的外周面 之間所形成的間隙，將大氣的進入口封閉，阻隔外氣以免 集電板以及與其焊接的部分的金屬箔受到外氣影響，能夠 防止氧化。 藉由第2或3發明的放電燈，藉由朝貫穿孔的開口側 擴張的錐狀面、或在貫穿孔的內表面所設置的階段部，來 形成凹部’則能在貫穿孔的軸方向較長地形成低熔點玻璃 ’而能確實地將大氣的進入口封閉，阻隔外氣以免集電板 以及與其焊接的部分的金屬箔受到外氣影響，能夠防止氧 化。 藉由第4發明的放電燈，外部簧片貫穿環狀的固體物 ’藉由配置在外部石英管的外端面，而能容易地定位，藉 由在該狀態將其加熱熔融，則能藉由低熔點玻璃確實地封 閉間隙的開口部。 藉由第5發明的放電燈，預先將低熔點玻璃充塡在放 電燈的凹部的內部，而將其加熱熔融，所以能確實地藉由 低熔點玻璃將間隙封閉。 -7- 200908066 藉由第6發明的放電燈，從外部石英管的外端面朝管 軸方向突出形成，藉由形成外部石英管的外周壁’則當將 低熔點玻璃加熱熔融時，不會產生朝封閉管的外側流出的 滴流情形。 藉由第7發明的放電燈，在外部簧片的外周面，藉由 在相當於間隙的部位形成捲箔，則由石英玻璃所構成的外 部石英管、與由鎢（W)所構成的外部簧片不會直接接觸。 雖然石英玻璃與外部簧片的線膨脹率不同，仍能藉由捲箔 來抑制互相的緩衝情形。 【實施方式】 針對本發明的第一實施方式加以說明。第1圖是顯示 放電燈的槪略構造的剖面圖。 放電燈，例如由石英玻璃等的光穿透性材料所構成’ 具備有放電容器1，而放電容器1具有：約球形的發光管 3、與在其兩端連續而朝外側延伸的封閉管2 ;在發光管3 的內部相對向配置著例如分別由鎢（W)所構成的陽極6及 陰極7。在放電容器1內，分別以預定的封入量封入有： 作爲發光物質的水銀、及作爲輔助啓動的緩衝氣體的例如 氙氣。水銀的封入量，例如在1〜7 0 m g / c m3的範圍內’例 如22mg/cm3，氣氣的封入量例如在0.05〜0.5MPa的範圍內 ，例如 0. IMP a。 在放電容器1內，在前端固定著陽極6或陰極7的內 部簧片8於封閉管2內沿著其管軸延伸配設。內部簧片8 200908066 的另一端部被支承於，在封閉管2內所配設的例如由石英 玻璃所構成的約圓柱狀的玻璃構件4。而朝放電容器1的 外部導出，也就是從封閉管2的外端朝外側突出延伸設置 的外部簧片9的一端部被玻璃構件4所支承。 在玻璃構件4的外周面，沿著放電燈的管軸方向互相 平行地配設有：互相在外周方向分離的複數枚例如6枚的 帶狀的金屬箔5。金屬箔5，例如由：鎢（W)、鉅（Ta)、釕 (Ru)、銶（Re)等的高熔點金屬或其合金所構成，而根據焊 接的容易度、焊接熱的傳導性優異程度等的理由，藉由以 鉬爲主成分的金屬構成較佳。各個金屬箔5，厚度例如爲 0.02~0.06mm，寬度例如是6〜15mm。而在玻璃構件4的外 部石英管1 3側的端面，設置有直徑6mm的讓外部簧片9 插入的孔部。 各金屬箔5的一端與內部簧片8電連接，另一端與外 部簧片9電連接。而放電容器1的封閉管2與玻璃構件4 隔著金屬箔5焊接而形成氣密密封構造。保持用筒體1 0， 是在插通著內部簧片8的狀態將其予以支承的例如石英玻 璃製的筒狀的內部簧片支承構件，與放電容器1的封閉管 2焊接。 針對電連接狀態具體說明，內部簧片8在插通於保持 用筒體1 0的狀態被支承，在內部簧片8的封閉部側固定 著金屬板1 1，藉由將金屬箔5焊接於金屬板1 1 ’而將內 部簧片8與金屬箔5電連接。插入到玻璃構件4的外部簧 片9在插通於外部石英管1 3的狀態被支承，設置集電板 -9- 200908066 1 2以從外部石英管1 3的發光管側的端面覆蓋外周面，藉 由將金屬箔5焊接於集電板1 2的外周面，而將外部簧片9 與金屬箔5電連接。 在該放電燈，藉由省略圖示的亮燈電源在陽極6及陰 極7的電極之間施加高電壓例如20kV，在電極間產生絕 緣破壞，接著產生放電電弧，放射出例如包含波長365nm 的i線或波長4 3 5 n m的g線的光。 第2圖是表示放電燈的封閉部的外端側的放大剖面圖 〇 在外部簧片9，朝外側開口的有底筒狀的集電板1 2， 是在外部簧片9貫穿其底部的狀態被固定著，在該集電板 1 2的外周面分別焊接著各個金屬箔5的另一端部，藉此， 隔著集電板12將外部簧片9與金屬箔5電連接。這裡作 爲構成集電板1 2的材料，例如用鉬（Mo)。在集電板1 2的 內部空間，配設有：在插通著外部簧片9的狀態將其支承 的例如石英玻璃製的筒狀的外部石英管1 3。 集電板12的外周面與金屬箔5，在各重疊的部位是藉 由點焊等方式焊接而電連接。當焊接時是將金屬箔5壓緊 ，所以有時焊接部分的金屬箔5會變薄。若焊接部分的金 屬箔5變薄，則於金屬箔5流動的電流的通路會變窄，所 以與集電板1 2焊接的部分上的金屬箔5容易溫度上升。 在溫度較高的部分金屬箔5容易氧化，而藉由氧化的進行 導致可成爲電流通路的剖面積漸漸減少，所以電阻變大而 溫度又變得更高。因爲產生這種現象，所以與集電板12 -10- 200908066 焊接的部分上的金屬箔5是最需要抑制氧化的部分。 藉由隔著金屬箔5將封閉管2與玻璃構件4焊接而封 閉，則分隔成發光空間與外氣空間。玻璃構件4的外端側 則成爲外氣空間，在外部石英管13的貫穿孔16的內周面 與外部簧片9的外周面之間所形成的間隙3 0與外部連通 。鎢（W)或鉬（Mo)等的金屬的熱膨脹率、與石英玻璃的熱 膨膜率相差約一位數’所以爲了讓金屬bS熱fei膜，需要在 金屬與石英玻璃之間設置間隙3 0。並且爲了讓由石英玻璃 所構成的外部石英管1 3與由鎢（W)所構成的外部簧片9不 直接接觸，而在外部簧片9的外周面設置由鉬（Mo)所構成 的捲箔1 5而插通於外部石英管1 3。 在外部石英管1 3的約中央所設的貫穿孔1 6，形成有 朝開口側擴張的錐狀面1 7。形成錐狀面1 7的部位，外部 石英管1 3的內周與外部簧片9的外周的距離變大，成爲 將貫穿孔1 6的外端擴張所設的環狀的凹部1 4。凹部1 4形 成在沿著外部簧片9的外周的軸方向，其最大外徑大於貫 穿孔1 6的內徑。在外部石英管1 3的貫穿孔1 6的內周面 與外部簧片9的外周面之間，形成有：朝外部簧片9的軸 方向延伸的間隙3 0，藉由將貫穿孔1 6擴張而形成凹部1 4 ，則讓貫穿孔1 6的外端的間隙3 0的空間變大。 爲了防止：因爲大氣通過間隙3 0，而讓集電板1 2與 金屬箔5及其焊接部分上的金屬箔5氧化，在外部石英管 1 3的貫穿孔1 6的內周面與外部簧片9的外周面之間所形 成的間隙3 0，充塡低熔點玻璃20讓其充滿將貫穿孔1 6外 -11 - 200908066 端擴張所設的凹部1 4。低熔點玻璃2 0其目的是要抑制 氣流入，所以在封閉管2的直徑方向切斷的剖面緊密地 設成，將在貫穿孔16的內周面與外部簧片9的外周面 間所形成的間隙3 0予以封閉。低熔點玻璃20以氧化硼 氧化鉍爲主成分，其主成分的總重量爲全體重量的70% 上。 在放電燈點亮時的外部石英管1 3的外端的溫度 150〜25〇°C。低熔點玻璃20的軟化點爲420°C，所以即 在放電燈點亮時，低熔點玻璃2 0仍不具黏性，在表面 在有細微裂縫。因爲形成於低熔點玻璃20的細微裂縫 而讓大氣流通於外部石英管1 3的外端側與間隙3 0的內 之間，必須形成爲能夠防止與集電板1 2焊接的部分上 金屬箔5暴露於外氣。因此，低熔點玻璃20，相對於形 細微裂縫的長度必須形成爲足夠的厚度’在貫穿孔1 6 軸方向需要形成爲至少涵蓋2mm。 藉由具有將貫穿孔16的外端擴張所設的凹部14 ’ 在外部石英管1 3的貫穿孔1 6的內周面與外部簧片9的 周面之間所形成的間隙3 0，在貫穿孔1 6的外端變大’ 能將低熔點玻璃2 0有效率地注入。藉由注入於該間隙 的低熔點玻璃2 0，將大氣的進入口封閉’阻隔外氣讓與 電板1 2焊接的部分的金屬箔5不會受到外氣影響’而 防止氧化。 ^玻璃構件4與外部簧片9的外周所形成的間隙3 形成有沒有設置低熔點玻璃20的空隙2 1。藉由使放1 外 配 之 與 以 是 使 存 ， 部 的 成 的 則 外 則 30 集 能 燈 -12- 200908066 的輸入電力增大、或縮短封閉部的軸方向的長度，放電燈 的亮燈條件變嚴格的話，則外部石英管1 3的外端側也容 易變得高溫。在這種條件下，低熔點玻璃20在亮燈時與 燈滅時相比上升了 40CTC以上的溫度，而會產生相當於該 溫度差的量的熱膨脹。而只要在低熔點玻璃2 0的周圍預 先設置空隙2 1的話，則低熔點玻璃20在外部簧片9的外 周，會具有因爲熱膨脹而能膨脹的裕度空間，而對玻璃構 件4或周圍的低溶點玻璃2 0不會造成負荷。 即使在這種條件讓放電燈亮燈，低熔點玻璃2 0即使 溫度升高也只是在45 0°C左右，低熔點玻璃20雖然會軟化 ，卻不會熔融。因此，低熔點玻璃2 0會保持在當初所設 的位置，空隙2 1不會被熔融的低熔點玻璃20埋住。 第3圖是顯不低溶點玻璃2 0的形成方法的在製造途 中的放電燈的封閉部的外端側的放大剖面圖。第3 .圖顯示 ，在間隙3 0沒有形成低熔點玻璃2 0的放電燈，將環狀的 固體物24插通於外部簧片9的狀態。 固體物24是將固狀的低熔點玻璃予以成形的構造。 在凹部14上配置環狀的固體物24，而將固體物24加熱熔 融的話，低熔點玻璃會注入到從外部石英管1 3的外端沿 著連通的貫穿孔1 6所形成的間隙3 0。在延伸於軸方向的 寬度狹窄的間隙3 0，在間隙3 0的直徑方向剖面將低溶點 玻璃緊密配置，很難封閉成確實地防止外氣流入。可是， 由於是將固狀的固體物24熔化配置成爲間隙3 0的蓋子， 所以容易維持低熔點玻璃的氣密性，能確實地抑制外氣的 -13- 200908066 流入。 藉由形成凹部1 4，而從外部石英管1 3的外朗 穿孔1 6通過的間隙3 0的開口部會變寬’所以谷易 點玻璃注入到寬度狹窄的間隙3 0。熔融的低溶點玻 擇性地有效率注入到，在外部石英管1 3的外端面 一階層的凹部1 4。使外部簧片9貫穿環狀的固體1 藉由將其配置在外部石英管13的外端面19 ’能容 位，藉由在該狀態將其加熱熔融，而能藉由低熔點 實地封閉間隙3 0的開口部。 也可不使用上述固體物而設置低熔點玻璃2 0 ° 也有將熔融的低熔點玻璃從封閉管2的外端面1 9 ’ 於外部石英管1 3與外部簧片9的外周所形成的間陵 方法。爲了有效率地將液體注入到很小的間隙’是 3 0中的空氣排出，同時將低熔點玻璃滴下。當注入 的低熔點玻璃而藉由自然冷卻讓其固化後，則低熔 20就充塡到在外部石英管1 3與外部簧片9的外周 的間隙3 0。 針對本發明的第二實施方式加以說明。第4圖 放電燈的封閉部的外端側的放大剖面圖。 取代在外側開口的有底筒狀的集電板1 2，使用 形成貫穿孔的集電碟1 8。在玻璃構件4與外部石] 之間配置了集電碟1 8，外部簧片9例如藉由壓入方 定在集電碟18的貫穿孔。作爲構成集電碟18的材 如鉬（T a)、鈮（N b)、鎢（W)、銦（Μ 〇)等的高熔點金 沿著貫 將低熔 璃能選 1 9變低 勿24， 易地定 玻璃確 例如， 注入到 賢30的 將間隙 足夠量 點玻璃 所形成 是顯不 在中央 廷管13 式而固 料，例 屬。集 -14- 200908066 電碟18的厚度，例如1〜5mm。 在集電碟18的外周面，在各個金屬箔5的另一端部 分別重疊的部位，是藉由點焊方式焊接而電連接。由於利 用這種方法接合，所以其特徵是焊接部分的金屬箔5容易 變薄，溫度容易上升。在溫度較高的部分金屬箔5容易氧 化，而會因爲氧化的進行而讓可成爲電流通路的剖面積漸 漸減少，所以電阻變大而溫度又變得更高。由於產生這種 現象，所以即使在要使用集電碟1 8來導通的情況，與集 電碟1 8焊接的部分上的金屬箔5會是最需要抑制氧化的 部分。 以將集電碟1 8與金屬箔5的接合部、及集電碟1 8的 外端予以覆蓋的方式，配置：有底圓筒狀的由鉬（Μ 〇)所構 成的蓋子23。藉由設置蓋子23，能防止由石英玻璃所構 成的外部石英管13、與由金屬所構成的集電碟18直接接 觸，並且防止集電碟1 8的外周端面的角部抵接於封閉管2 。由於集電碟1 8不會直接接觸於外部石英管1 3或封閉管 2，所以能防止在構成外部石英管1 3或封閉管2的石英玻 璃產生龜裂的情形。而蓋子23不是藉由焊接於集電碟18 或金屬箔5而加以固定，而是被保持爲在外部石英管13 與集電碟1 8之間不會移動的程度。 在於外部石英管1 3的約中央所設置的貫穿孔1 6 ,在 其內表面形成階段部2 5。貫穿孔1 6的直徑是較外部簧片 9的直徑大於0.5mm左右，而貫穿孔16較階段部25更外 端側的直徑，是較貫穿孔16的直徑更大於0.5 mm〜3 mm。 -15- 200908066 貫穿孔1 6的較階段部25更外端側’其外部石英管1 3的 內周與外部簧片9的外周的分離距離變大’而成爲將貫穿 孔16的外端擴張所設的環狀的凹部14。凹部14，沿著外 部簧片9的外周形成於軸方向’其外徑大於貫穿孔1 6的 內徑。藉由將貫穿孔16擴張而將凹部14形成於：形成間 隙30的外部石英管1 3的貫穿孔1 ό的內周面與外部簧片9 的外周面之間，而讓貫穿孔1 6的外端的間隙3 〇變大。 藉由具有將貫穿孔1 6的外端擴張所設置的凹部1 4， 則在外部石英管1 3的貫穿孔1 6的內周面與外部簧片9的 外周面之間所形成的間隙3 0 ’在貫穿孔1 6的外端變大’ 而能將低熔點玻璃20有效率地注入’將大氣的進入口封 閉，阻隔外氣以免與集電碟18焊接的部分的金屬箔5受 到外氣影響，而能防止氧化。 接著，顯示低熔點玻璃20的形成方法。在貫穿孔1 6 的內表面形成階段部2 5的凹部1 4 ’是能將固狀的低熔點 玻璃成型的固體物配置在凹部1 4的內部的程度’能採取 很大的內部空間。於是在間隙30沒有形成低熔點玻璃20 的放電燈，能在將環狀的固體物插通於外部簧片9的狀態 而配置於凹部1 4的內部。作爲固狀的低熔點玻璃成型的 固體物，使用外徑梢小於凹部1 4的直徑，內徑稍大於外 部簧片9的直徑的構件。當在凹部14的內部配置固體物 將其加熱熔融時，低熔點玻璃2 0會充滿其與凹部1 4的內 徑之間、以及其與外部簧片9的外徑之間，而能緊密地配 設低熔點玻璃2 0，能將其封閉而確實地防止外氣流入。 -16- 200908066 低熔點玻璃成型的固體物，只要加熱到讓其外表面熔 融的程度’就能藉由低熔點玻璃20將間隙30的開口部封 閉’能夠減低熔融的低熔點玻璃20朝其他地方流出的情 形°在使固體物在其外表面以外的部分不使其熔融的狀態 ’能利用爲低熔點玻璃20，所以能有效地防止因爲在加熱 熔融時所產生的氣孔造成大氣進入的情形。由於是將固體 物預先充塡在放電燈的凹部1 4的內部而將其加熱熔融， 所以能藉由低熔點玻璃2 0確實地將間隙3 0的開口部封閉 〇 接著針對本發明的第三實施方式來說明。第5圖是顯 示將封閉管2形成爲從外部石英管1 3的外端面1 9突出的 放電燈的封閉部的外端側的放大剖面圖。 在第一實施方式所顯示的放電燈’將封閉管2朝管軸 方向外側延伸，將其形成爲較外部石英管1 3的外端面1 9 更朝管軸方向突出，而形成外部石英管1 3的外周壁26。 外周壁2 6具有讓流動體不朝外部流出的保持緣部的功能 。因此，即使藉由第3圖所示的方法，在使固體物24配 置於外部石英管13的外端面的狀態使其加熱熔融’由 於固體物2 4配置於外周壁2 6的內側’所以熔融的低熔點 玻璃2 0不會越過外周壁2 6而漏出，不會產生低熔點玻璃 2 0流出到封閉管2的外側的滴流情形。 並且爲了確實防止金屬箔5接觸到大氣而氧化’而在 將金屬箔5的表面，尤其是在與集電板1 2焊接的部分的 金屬箔5的表面，形成藉由鉚複合氧化物（Rb2M〇〇4)所構 -17- 200908066 成的密封物22。密封物22是包含了铷（Rb)、鉬（Mo)的铷 複合氧化物（Rb2M〇04)，是在高溫也很穩定的化合物，所 以即使在放電燈亮燈時也不會與金屬箔5反應而侵蝕。除 了低熔點玻璃20之外，藉由在與集電板1 2焊接的部分的 金屬箔5的表面形成密封物22，則能有效地阻隔外氣而防 止金屬箔5氧化。密封物22，形成爲在其與低熔點玻璃 2 〇之間保留有成爲空隙2 1的空間。 由铷複合氧化物（Rb2M〇〇4)所構成的密封物22，在將 低溶點玻璃2 0形成於間隙3 0之前，能設置成如下的方式 〇 將調整過濃度的鉚硝酸鹽（RbN〇3)的水溶液，適量從 封閉管2的外端面1 9的間隙3 0滴下。將在間隙3 0充塡 有鉚硝酸鹽的水溶液的放電燈加熱到約1 5 〇 °C使其乾燥’ 讓水分蒸發而產生鉚硝酸鹽。所蒸發的水分放出到放電燈 的外部。並且以氫噴燃器加熱的話，會放出Ν Ο X氣體而產 生鉚氧化物（Rb2〇)，再利用高溫化與由鉬（Mo)所構成的金 屬箱5反應，而產生由铷複合氧化物（RhMoO4)所構成的 密封物2 2。 铷硝酸鹽（RbNo3)的水溶液’例如將純水與硝酸铷調 成濃度爲2mol/L，使硝酸铷溶解於純水所形成。將鉚硝酸 鹽的水溶液注入而得到均勻的被膜，當量不夠時’也能在 乾燥後追加注入。將注入與乾燥動作重複複數次’則能在 金屬箔5的表面作出由_複合氧化物（RhMoCU)所構成的 密封物22的厚被膜。 -18- 200908066 上述說明所用的圖面，是將實際的放電燈的封閉部予 以簡化，爲了圖示而將將金屬箔5的厚度等誇張顯示。而 第2圖所示的使用於集電板1 2的封閉形狀、與第4圖所 示的使用於集電碟1 8的封閉形狀，可相互自由地選擇。 本發明的放電燈也可使用於超過低熔點玻璃2 0的軟 化點的溫度區域。在超過軟化點的溫度區域，低熔點玻璃 2 0沒有細微裂縫，能防止外氣流入，所以低熔點玻璃2 0 能更有效地產生作用。 【圖式簡單說明】 第1圖是顯示本發明的放電燈的槪略構造的剖面圖。 第2圖是顯示本發明的放電燈的封閉部的外端側的放 大剖面圖。 第3圖是顯示本發明的放電燈的封閉部的外端側的放 大剖面圖。 第4圖是顯示本發明的放電燈的封閉部的外端側的放 大剖面圖。 第5圖是顯示本發明的放電燈的封閉部的外端側的放 大剖面圖。 第6圖是顯示習知構造的放電燈的封閉部的外端側的 放大剖面圖。 【主要元件符號說明】 1 :放電容器 -19- 200908066 2 :封閉管 3 :發光管 4 :玻璃構件 5 :金屬箔 6 :陽極 7 :陰極 8 :內部簧片 9 :外部簧片 1 〇 :保持用筒體 1 1 :金屬板 1 2 :集電板 1 3 :外部石英板 1 4 :凹部 1 5 :捲箔 1 6 ’·貫穿孔 1 7 :錐狀面 2 0 :低溶點玻璃 2 1 :空隙 2 2 :密封物BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used in a light source of an exposure apparatus such as a liquid crystal, a semiconductor, or a printed electric panel. In particular, the discharge lamp of the closed portion is sealed by a foil sealed with a metal foil made of molybdenum (Mo). [Prior Art] As a power supply structure for a discharge lamp, an electrode is connected to a metal foil embedded in a closed tube, and an external reed is connected to the other end of the metal foil to achieve conduction. Such a discharge lamp having a closed portion of a foil sealing structure may cause a closed tube and an outer reed due to a difference in expansion coefficients of quartz glass constituting the closed tube and molybdenum (Mo) or tungsten (W) constituting the outer reed. A fine gap is formed between the outer circumferences. Because of this gap, the atmosphere enters the surface of the metal foil or the outer reed, which greatly promotes the oxidation of the metal foil or the outer reed. As a result, the closed tube will be cracked, the metal foil will be blown, and the life of the discharge lamp will be shortened. The technique disclosed in Japanese Laid-Open Patent Publication No. 2004-3 1 91 77 is known as a means for solving the problem. As shown in Fig. 6, in the discharge lamp used in the liquid crystal projector, a gap formed by the tantalum oxide (Rb20) is filled in the gap formed between the closed tube 2 and the outer reed 9 and the outer periphery of the metal foil 5. In the object 22, a low-melting glass 20 mainly composed of boron oxide and cerium oxide is adhered to the outer end portion of the closed tube 2. With this configuration, the inlet opening of the outer end surface of the closed pipe 2 can be closed, and the external air can be blocked to prevent the outer reed 9 and the metal foil 5 from being affected by the external air, thereby improving the heat resistance of the closed portion. Wen-4-200908066 degrees. In addition, it is also possible to prolong the service life in a high-temperature condition [Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-319177 [Abstract] [Problems to be Solved by the Invention] However, a large-sized discharge lamp used in a light source of an exposure apparatus Even in the above configuration, that is, in the gap formed between the closed tube 2 and the outer reed 9 and the outer periphery of the metal foil 5, the seal 22' is filled, and the low-melting glass 20 is attached to the outer end surface of the closed tube 2, There are still problems that prevent the atmosphere from entering. The discharge lamp used for the light source of the exposure device is larger than that of the discharge lamp used in the liquid crystal projector. Therefore, the gap formed on the outer circumference of the outer reed 9 also becomes large. Further, the discharge lamp used in the light source of the exposure device is such that the outer end surface of the closed tube 2 is away from the electrode, and the temperature does not become higher even when the discharge lamp is turned on. Therefore, the low-melting glass 20 maintains a temperature lower than the softening point when the discharge lamp is turned on, and fine cracks are formed on the surface. In the large discharge lamp used for the light source of the exposure apparatus, since there is a fine crack on the surface of the low-melting glass 20, only the low-melting glass 20 is attached to the outer end surface of the closed tube 2, and the outer periphery of the outer reed 9 cannot be completely formed. The gap formed is closed, and the metal box 5 is oxidized due to the external air flow. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. A discharge lamp is disclosed which is used in a discharge lamp for exposing a light source of a device of -5 to 200908066. The inlet and outlet of the atmosphere are closed by a low-melting glass, and the outside air can be blocked to prevent the metal foil from being affected by the external air. [Means for Solving the Problem] The first invention includes a discharge vessel in which a closed tube is connected to both ends of the arc tube, an electrode disposed inside the arc tube, and a glass disposed inside the closed tube a member, a metal foil disposed on an outer circumferential surface of the glass member, and an outer reed that is electrically connected to the metal foil and inserted through a through hole of the outer quartz tube; and an inner circumferential surface of the through hole of the outer quartz tube; A gap formed between the outer peripheral surface of the outer reed has a low-melting glass, and a concave portion provided to expand the through hole is provided at an outer end of the through hole. According to a second aspect of the invention, the recessed portion is formed by a tapered surface that expands toward an opening side of the through hole. According to a third aspect of the invention, the recessed portion is formed by providing a step portion on an inner surface of the through hole. According to a fourth aspect of the invention, the low-melting glass is a ring-shaped solid material, and the outer reed is formed by being heated and melted in a state in which the outer reed is inserted and disposed on an outer end surface of the quartz tube. According to a fifth aspect of the invention, the low-melting glass is a ring-shaped solid material, and the outer reed is formed by being heated and melted in a state in which the outer reed is inserted and disposed inside the concave portion. According to a sixth aspect of the invention, the closed tube is formed so as to protrude from an outer end surface of the outer quartz tube in a tube axis direction to form an outer peripheral wall of the outer quartz tube of the -6-200908066. According to a seventh aspect of the invention, in the outer peripheral surface of the outer reed, a coiled foil is formed on a portion corresponding to the gap. According to the discharge lamp of the first aspect of the invention, the recessed portion provided by expanding the through hole at the outer end of the through hole allows the low-melting glass to enter the through hole of the outer quartz tube. The gap formed between the circumferential surface and the outer peripheral surface of the outer reed is closed to the outside air inlet, and the outside air is blocked to prevent the current collector and the metal foil of the portion welded thereto from being affected by the external air, thereby preventing oxidation. According to the discharge lamp of the second or third aspect of the invention, the concave portion can be formed in the axial direction of the through hole by the tapered surface that expands toward the opening side of the through hole or the stepped portion that is provided on the inner surface of the through hole. The low-melting glass is formed long, and the inlet port of the atmosphere can be surely closed, and the outside air is blocked to prevent the current collector and the metal foil of the portion welded thereto from being affected by the external air, thereby preventing oxidation. According to the discharge lamp of the fourth aspect of the invention, the outer reed penetrates the annular solid object' by being disposed on the outer end surface of the outer quartz tube, and can be easily positioned, and by heating and melting it in this state, The low melting point glass surely closes the opening of the gap. According to the discharge lamp of the fifth aspect of the invention, the low-melting glass is previously filled in the concave portion of the discharge lamp to be heated and melted, so that the gap can be surely closed by the low-melting glass. -7-200908066 The discharge lamp of the sixth invention is formed by projecting from the outer end surface of the outer quartz tube toward the tube axis direction, and by forming the outer peripheral wall of the outer quartz tube, when the low-melting glass is heated and melted, A trickle flow is produced towards the outside of the closed tube. According to the discharge lamp of the seventh aspect of the invention, an outer quartz tube made of quartz glass and an outer portion made of tungsten (W) are formed on the outer peripheral surface of the outer reed by a roll foil at a portion corresponding to the gap. The reeds are not in direct contact. Although the coefficient of linear expansion of the quartz glass and the outer reed is different, the mutual buffering can be suppressed by the coiled foil. [Embodiment] A first embodiment of the present invention will be described. Fig. 1 is a cross-sectional view showing a schematic structure of a discharge lamp. The discharge lamp, for example, made of a light-transmitting material such as quartz glass, is provided with a discharge vessel 1 having an approximately spherical light-emitting tube 3 and a closed tube 2 extending continuously at both ends thereof and extending outward. An anode 6 and a cathode 7 each made of, for example, tungsten (W) are disposed opposite to each other inside the arc tube 3. In the discharge vessel 1, for example, mercury as a luminescent material and helium gas as a buffer gas for assisting activation are sealed with a predetermined amount of encapsulation. The amount of mercury enclosed is, for example, in the range of 1 to 70 m g / c m 3 'e.g., 22 mg/cm 3 , and the entrapment amount of the gas is, for example, in the range of 0.05 to 0.5 MPa, for example, 0. IMP a. In the discharge vessel 1, an inner reed 8 having an anode 6 or a cathode 7 fixed to the front end thereof is disposed in the closed tube 2 along its tube axis. The other end portion of the inner reed 8 200908066 is supported by a cylindrical member 4 of a cylindrical shape, such as quartz glass, disposed in the closed tube 2. On the other hand, the outer portion of the discharge vessel 1 is led out, that is, the one end portion of the outer reed 9 projecting outward from the outer end of the closed tube 2 is supported by the glass member 4. On the outer circumferential surface of the glass member 4, a plurality of, for example, six strip-shaped metal foils 5 separated from each other in the outer circumferential direction are disposed in parallel with each other in the tube axis direction of the discharge lamp. The metal foil 5 is made of, for example, a high melting point metal such as tungsten (W), giant (Ta), ruthenium (Ru), or ruthenium (Re) or an alloy thereof, and is excellent in soldering easiness and solder heat conductivity. The reason for the degree or the like is preferably constituted by a metal containing molybdenum as a main component. Each of the metal foils 5 has a thickness of, for example, 0.02 to 0.06 mm and a width of, for example, 6 to 15 mm. Further, on the end surface of the glass member 4 on the side of the outer quartz tube 13 side, a hole portion having a diameter of 6 mm into which the outer reed 9 is inserted is provided. One end of each of the metal foils 5 is electrically connected to the inner reed 8, and the other end is electrically connected to the outer reed 9. On the other hand, the closed tube 2 of the discharge vessel 1 and the glass member 4 are welded via the metal foil 5 to form a hermetic sealing structure. The holding cylinder 10 is a cylindrical inner reed supporting member made of, for example, quartz glass, which is supported by the inner reed 8, and is welded to the closing pipe 2 of the discharge vessel 1. Specifically, the internal reed 8 is supported in a state of being inserted into the holding cylinder 10, and the metal plate 1 is fixed to the closed portion side of the inner reed 8 by soldering the metal foil 5 to the electrical connection state. The metal plate 1 1 ' electrically connects the inner reed 8 to the metal foil 5. The outer reed 9 inserted into the glass member 4 is supported in a state of being inserted into the outer quartz tube 13, and the current collector plate -9-200908066 1 2 is provided to cover the outer peripheral surface from the end surface of the outer quartz tube 13 on the light-emitting tube side. The outer reed 9 is electrically connected to the metal foil 5 by welding the metal foil 5 to the outer peripheral surface of the current collector plate 12. In the discharge lamp, a high voltage, for example, 20 kV is applied between the electrodes of the anode 6 and the cathode 7 by a lighting power source (not shown) to cause dielectric breakdown between the electrodes, and then a discharge arc is generated to emit, for example, i having a wavelength of 365 nm. Line or light of the g line with a wavelength of 4 3 5 nm. Fig. 2 is an enlarged cross-sectional view showing the outer end side of the closing portion of the discharge lamp. The outer reed 9 is opened to the outside, and the bottomed cylindrical collector plate 12 is inserted through the bottom of the outer reed 9 The state is fixed, and the other end portion of each of the metal foils 5 is welded to the outer peripheral surface of the current collector plate 12, whereby the outer reed 9 and the metal foil 5 are electrically connected via the current collector plate 12. Here, as a material constituting the collector plate 12, for example, molybdenum (Mo) is used. In the inner space of the current collector plate 12, a cylindrical outer quartz tube 13 made of, for example, quartz glass, supported by the outer reed 9 is disposed. The outer peripheral surface of the current collector plate 12 and the metal foil 5 are electrically connected by welding by spot welding or the like at each overlapping portion. When the metal foil 5 is pressed during welding, the metal foil 5 of the welded portion may be thinned. When the metal foil 5 of the welded portion is thinned, the path of the current flowing through the metal foil 5 is narrowed, so that the metal foil 5 on the portion welded to the current collector 12 is likely to rise in temperature. In the portion where the temperature is high, the metal foil 5 is easily oxidized, and the area of the cross section which can become a current path is gradually reduced by the progress of oxidation, so that the electric resistance becomes large and the temperature becomes higher. Because of this phenomenon, the metal foil 5 on the portion welded to the collector plate 12-10-200908066 is the portion most in need of oxidation inhibition. The closed tube 2 and the glass member 4 are welded and sealed by the metal foil 5, and are separated into a light-emitting space and an outside air space. The outer end side of the glass member 4 is an outer air space, and a gap 30 formed between the inner peripheral surface of the through hole 16 of the outer quartz tube 13 and the outer peripheral surface of the outer reed 9 communicates with the outside. The coefficient of thermal expansion of a metal such as tungsten (W) or molybdenum (Mo) differs from the thermal expansion rate of quartz glass by about a single digit. Therefore, in order to heat the metal bS, it is necessary to provide a gap between the metal and the quartz glass. 0. Further, in order to prevent the outer quartz tube 13 composed of quartz glass from being in direct contact with the outer reed 9 composed of tungsten (W), a roll composed of molybdenum (Mo) is provided on the outer peripheral surface of the outer reed 9 The foil 15 is inserted into the outer quartz tube 13 . A through-hole 16 formed in the center of the outer quartz tube 13 is formed with a tapered surface 17 that expands toward the opening side. At the portion where the tapered surface 17 is formed, the distance between the inner circumference of the outer quartz tube 13 and the outer circumference of the outer reed 9 is increased, and the annular recess portion 14 is formed by expanding the outer end of the through hole 16. The recess 14 is formed in the axial direction along the outer circumference of the outer reed 9, and its maximum outer diameter is larger than the inner diameter of the through-hole 16. Between the inner circumferential surface of the through hole 16 of the outer quartz tube 13 and the outer circumferential surface of the outer reed 9, a gap 30 extending in the axial direction of the outer reed 9 is formed by the through hole 16 When the concave portion 1 4 is expanded, the space of the gap 30 of the outer end of the through hole 16 is increased. In order to prevent: because the atmosphere passes through the gap 30, the collector plate 12 and the metal foil 5 and the metal foil 5 on the welded portion thereof are oxidized, and the inner peripheral surface and the outer spring of the through hole 16 of the outer quartz tube 13 are oxidized. The gap 30 formed between the outer peripheral faces of the sheets 9 is filled with the low-melting glass 20 so as to fill the recesses 14 provided to expand the ends of the through holes 16 to -11 - 200908066. The purpose of the low-melting glass 20 is to suppress the inflow of air, so that the cross section cut in the diameter direction of the closed pipe 2 is closely provided so as to form between the inner peripheral surface of the through hole 16 and the outer peripheral surface of the outer reed 9. The gap 30 is closed. The low-melting glass 20 is mainly composed of ruthenium oxide ruthenium oxide, and the total weight of the main component is 70% of the total weight. The temperature of the outer end of the outer quartz tube 13 when the discharge lamp is turned on is 150 to 25 〇 °C. The softening point of the low-melting glass 20 is 420 ° C, so that when the discharge lamp is turned on, the low-melting glass 20 is still non-tacky and has fine cracks on the surface. Because the fine crack formed in the low-melting glass 20 allows the atmosphere to flow between the outer end side of the outer quartz tube 13 and the inside of the gap 30, it is necessary to form a portion of the metal foil which can be prevented from being welded to the current collector plate 12. 5 exposed to outside air. Therefore, the low-melting glass 20 must be formed to have a sufficient thickness with respect to the length of the fine micro-cracks to be formed to cover at least 2 mm in the axial direction of the through-hole 16 . The gap 3 0 formed between the inner circumferential surface of the through hole 16 of the outer quartz tube 13 and the circumferential surface of the outer reed 9 by the recess 14' provided by expanding the outer end of the through hole 16 is The outer end of the through hole 16 becomes large, and the low melting point glass 20 can be efficiently injected. By the low-melting glass 20 injected into the gap, the inlet port of the atmosphere is closed, and the metal foil 5 which blocks the outside air and is welded to the electric plate 12 is not affected by the outside air to prevent oxidation. The gap 3 formed by the outer periphery of the glass member 4 and the outer reed 9 is formed with a void 21 in which the low-melting glass 20 is not provided. By setting the external distribution and the external output, the input power of the 30-energy lamp-12-200908066 is increased, or the length of the closed portion in the axial direction is shortened, and the discharge lamp is turned on. When the conditions are strict, the outer end side of the outer quartz tube 13 is also likely to become high in temperature. Under such conditions, the low-melting glass 20 rises by a temperature of 40 CTC or more when it is turned on, and generates thermal expansion corresponding to the temperature difference. Further, if the gap 2 1 is provided in advance around the low-melting glass 20, the low-melting glass 20 has a margin space which is expandable due to thermal expansion on the outer periphery of the outer reed 9, and is applied to the glass member 4 or the periphery thereof. Low melting point glass 20 does not cause a load. Even in such a condition that the discharge lamp is turned on, the low-melting glass 20 is only at about 45 ° C even if the temperature is raised, and the low-melting glass 20 is softened but does not melt. Therefore, the low-melting glass 20 is maintained at the position originally set, and the void 21 is not buried by the molten low-melting glass 20. Fig. 3 is an enlarged cross-sectional view showing the outer end side of the closed portion of the discharge lamp in the middle of the manufacturing process of the method for forming the low melting point glass 20. Fig. 3 shows a state in which the discharge lamp of the low-melting glass 20 is not formed in the gap 30, and the annular solid 24 is inserted into the outer reed 9. The solid matter 24 has a structure in which a solid low-melting glass is molded. When the annular solid material 24 is disposed on the concave portion 14, and the solid material 24 is heated and melted, the low-melting-point glass is injected into the gap 3 0 formed from the outer end of the outer quartz tube 13 along the communicating through hole 16. . In the gap 30 having a narrow width extending in the axial direction, the low-melting point glass is closely arranged in the diametrical cross section of the gap 30, and it is difficult to close it so as to surely prevent the outside air from entering. However, since the solid solid matter 24 is melted and disposed as the lid of the gap 30, it is easy to maintain the airtightness of the low-melting glass, and it is possible to reliably suppress the inflow of the outside air -13-200908066. By forming the concave portion 14, the opening portion of the gap 30 passing through the outer peripheral perforation 16 of the outer quartz tube 13 is widened, so that the valley-like glass is injected into the gap 30 having a narrow width. The molten low melting point is selectively injected into the outer end surface of the outer quartz tube 13 by a recess 11 of the outer layer. The outer solid piece 9 is inserted through the annular solid 1 by disposing it on the outer end surface 19' of the outer quartz tube 13, and by heating and melting it in this state, the gap 3 can be solidly closed by the low melting point. The opening of 0. It is also possible to provide a low-melting glass 20 ° without using the above solid matter, or a method of forming a molten low-melting glass from the outer end surface 1 9 ' of the closed tube 2 to the outer circumference of the outer quartz tube 13 and the outer reed 9 . In order to efficiently inject the liquid into a small gap, the air in 30 is discharged while the low-melting glass is dropped. When the injected low-melting glass is solidified by natural cooling, the low-melting 20 is filled to the gap 30 between the outer quartz tube 13 and the outer periphery of the outer reed 9. A second embodiment of the present invention will be described. Fig. 4 is an enlarged cross-sectional view showing the outer end side of the closed portion of the discharge lamp. Instead of the bottomed cylindrical collector plate 12 that is open on the outside, a collector disk 18 that forms a through hole is used. A collecting plate 18 is disposed between the glass member 4 and the outer stone, and the outer reed 9 is pressed into the through hole of the collecting plate 18, for example, by press fitting. The high-melting-point gold, such as molybdenum (T a), niobium (N b), tungsten (W), indium (yttrium), etc., which constitutes the collector disk 18, becomes low in the low-melting glass. 24, easy to set the glass indeed, for example, injected into the sin 30 will be enough gaps to form a glass formed is not in the central Ting tube 13 type and solid material, for example. Set -14- 200908066 The thickness of the disc 18, for example 1~5mm. On the outer circumferential surface of the collecting disk 18, the portions which are overlapped at the other end portions of the respective metal foils 5 are electrically connected by spot welding. Since it is joined by this method, it is characterized in that the metal foil 5 of the welded portion is easily thinned and the temperature is liable to rise. In the portion where the temperature is high, the metal foil 5 is easily oxidized, and the cross-sectional area which becomes a current path is gradually reduced by the progress of oxidation, so that the electric resistance becomes large and the temperature becomes higher. Since this phenomenon occurs, even in the case where the collector 18 is to be turned on, the metal foil 5 on the portion welded to the collector 18 is the portion most in need of oxidation inhibition. A lid 23 made of molybdenum (bottom) having a bottomed cylindrical shape is disposed so as to cover the joint portion of the collecting plate 18 and the metal foil 5 and the outer end of the collecting plate 18. By providing the cover 23, it is possible to prevent the outer quartz tube 13 composed of quartz glass from coming into direct contact with the collector disk 18 made of metal, and to prevent the corner portion of the outer peripheral end surface of the collector disk 18 from abutting against the closed tube. 2 . Since the collecting plate 18 does not directly contact the outer quartz tube 13 or the closed tube 2, it is possible to prevent the quartz glass constituting the outer quartz tube 13 or the closed tube 2 from being cracked. The cover 23 is not fixed by being welded to the collecting plate 18 or the metal foil 5, but is kept to such an extent that it does not move between the outer quartz tube 13 and the collecting plate 18. The through hole 16 provided at the center of the outer quartz tube 13 has a step portion 25 formed on the inner surface thereof. The diameter of the through hole 16 is larger than the diameter of the outer reed 9 by about 0.5 mm, and the diameter of the through hole 16 from the outer end side of the step portion 25 is larger than the diameter of the through hole 16 by 0.5 mm to 3 mm. -15-200908066 The outer end side of the through-hole 16 is further increased from the outer end side of the outer quartz tube 13 to the outer circumference of the outer reed 9 to become the outer end of the through hole 16 An annular recess 14 is provided. The concave portion 14 is formed in the axial direction along the outer circumference of the outer reed 9 and has an outer diameter larger than the inner diameter of the through hole 16. The concave portion 14 is formed by expanding the through hole 16 between the inner circumferential surface of the through hole 1 ό of the outer quartz tube 13 forming the gap 30 and the outer circumferential surface of the outer reed 9 to allow the through hole 16 The gap 3 at the outer end becomes larger. The gap 3 formed between the inner circumferential surface of the through hole 16 of the outer quartz tube 13 and the outer circumferential surface of the outer reed 9 by having the concave portion 14 provided to expand the outer end of the through hole 16 0 ' becomes larger at the outer end of the through hole 16', and the low-melting glass 20 can be efficiently injected into the 'inlet of the atmosphere, and the outer foil is blocked from the metal foil 5 of the portion where the collector 18 is welded. Gas influence, but can prevent oxidation. Next, a method of forming the low-melting glass 20 is shown. The recessed portion 14' in which the step portion 25 is formed on the inner surface of the through hole 16 is such a degree that the solid material capable of molding the solid low-melting glass can be disposed inside the recessed portion 14' can take a large internal space. Then, the discharge lamp of the low-melting-point glass 20 is not formed in the gap 30, and can be disposed inside the recessed portion 14 in a state in which the annular solid object is inserted into the outer reed 9. As the solid material molded of the solid low-melting glass, a member having an outer diameter tip smaller than the diameter of the concave portion 14 and having an inner diameter slightly larger than the diameter of the outer reed 9 is used. When solid matter is disposed inside the recess 14 to heat and melt it, the low-melting glass 20 is filled between its inner diameter and the inner diameter of the recess 14 and its outer diameter with the outer reed 9, and can be tightly The low-melting glass 20 is provided to close it and reliably prevent the outside air from entering. -16- 200908066 The solid material formed by the low-melting glass can be cooled by heating to the extent that the outer surface of the low-melting glass can be closed by the low-melting glass 20 to reduce the melting of the low-melting glass 20 toward other places. In the case of the outflow, the state in which the solid matter is not melted in the portion other than the outer surface thereof can be utilized as the low-melting glass 20, so that the atmosphere can be effectively prevented from entering due to the pores generated during heating and melting. Since the solid matter is preliminarily charged in the inside of the concave portion 14 of the discharge lamp and heated and melted, the opening portion of the gap 30 can be surely closed by the low-melting glass 20, and then the third portion of the present invention. The embodiment will be described. Fig. 5 is an enlarged cross-sectional view showing the outer end side of the closed portion of the discharge lamp in which the closed tube 2 is formed to protrude from the outer end surface 19 of the outer quartz tube 13. In the discharge lamp shown in the first embodiment, the closed tube 2 is extended outward in the tube axis direction, and is formed to protrude more toward the tube axis than the outer end surface 19 of the outer quartz tube 13 to form the outer quartz tube 1 The outer peripheral wall 26 of 3. The outer peripheral wall 26 has a function of a retaining edge portion for allowing the fluid to flow out to the outside. Therefore, even if the solid material 24 is placed on the outer end surface of the outer quartz tube 13 by the method shown in FIG. 3, it is heated and melted, and the solid material 24 is disposed inside the outer peripheral wall 26, so that it is melted. The low-melting glass 20 does not leak over the outer peripheral wall 26, and does not cause a dripping of the low-melting glass 20 to the outside of the closed tube 2. And in order to surely prevent the metal foil 5 from coming into contact with the atmosphere and oxidizing', on the surface of the metal foil 5, particularly on the surface of the metal foil 5 welded to the collector plate 12, a riveted composite oxide (Rb2M) is formed. 〇〇 4) Constructed as a seal 22 of 2009-200908066. The sealing material 22 is a ruthenium composite oxide (Rb2M〇04) containing ruthenium (Rb) or molybdenum (Mo), and is a compound which is stable at a high temperature, so that it does not adhere to the metal foil 5 even when the discharge lamp is turned on. The reaction erodes. In addition to the low-melting glass 20, by forming the seal 22 on the surface of the metal foil 5 welded to the current collector plate 12, it is possible to effectively block the outside air and prevent the metal foil 5 from being oxidized. The seal 22 is formed to have a space which becomes the void 21 between the low-melting glass and the low-melting glass. The seal 22 composed of the composite oxide (Rb2M〇〇4) can be adjusted to have an adjusted concentration of the riveted nitrate (RbN) before the low-melting point glass 20 is formed in the gap 30. An appropriate amount of the aqueous solution of 〇3) is dropped from the gap 30 of the outer end surface 19 of the closed tube 2. A discharge lamp filled with an aqueous solution of rivet nitrate in the gap 30 is heated to about 15 ° C to dry it to evaporate water to produce a rivet nitrate. The evaporated water is released to the outside of the discharge lamp. When heated by a hydrogen burner, Ν X gas is released to generate a slag oxide (Rb2 〇), and the high temperature is reacted with a metal case 5 composed of molybdenum (Mo) to produce a ruthenium composite oxide. Seal (2) of (RhMoO4). The aqueous solution of cerium nitrate (RbNo3) is formed, for example, by adjusting pure water and cerium nitrate to a concentration of 2 mol/L to dissolve cerium nitrate in pure water. An aqueous solution of the rivet nitrate is injected to obtain a uniform film, and when the equivalent amount is insufficient, it can be additionally injected after drying. When the injection and drying operations are repeated a plurality of times, a thick film of the sealing material 22 made of _composite oxide (RhMoCU) can be formed on the surface of the metal foil 5. -18- 200908066 The drawing used in the above description is to simplify the closing portion of the actual discharge lamp, and the thickness and the like of the metal foil 5 are exaggerated for illustration. Further, the closed shape used for the current collector plate 12 shown in Fig. 2 and the closed shape used for the collector disk 18 shown in Fig. 4 can be freely selected from each other. The discharge lamp of the present invention can also be used in a temperature region exceeding the softening point of the low melting point glass 20. In the temperature region exceeding the softening point, the low-melting glass 20 has no fine cracks and prevents the outside air from entering, so that the low-melting glass 20 can function more effectively. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a schematic structure of a discharge lamp of the present invention. Fig. 2 is an enlarged cross-sectional view showing the outer end side of the closing portion of the discharge lamp of the present invention. Fig. 3 is an enlarged cross-sectional view showing the outer end side of the closing portion of the discharge lamp of the present invention. Fig. 4 is an enlarged cross-sectional view showing the outer end side of the closing portion of the discharge lamp of the present invention. Fig. 5 is an enlarged cross-sectional view showing the outer end side of the closing portion of the discharge lamp of the present invention. Fig. 6 is an enlarged cross-sectional view showing the outer end side of the closed portion of the discharge lamp of the conventional configuration. [Description of main components] 1 : Discharge capacitor -19- 200908066 2 : Closed tube 3 : Illuminated tube 4 : Glass member 5 : Metal foil 6 : Anode 7 : Cathode 8 : Internal reed 9 : External reed 1 〇 : Hold The cylinder 1 1 : the metal plate 1 2 : the collector plate 1 3 : the outer quartz plate 1 4 : the recess 1 5 : the coil foil 1 6 '· the through hole 1 7 : the tapered surface 2 0 : the low melting point glass 2 1 : void 2 2 : seal