511116 A7 B7 五、發明説明（1) 【發明所屬之技術領域】 本發明係關於，在半導體或液晶面板等的製造上的光 平板印刷工程等，所利用的光源或映像投射用系統中，所 使用的數位顯微鏡元件或液晶等的投影機用的光源，更詳 細的說，係關於短電弧放電燈的電極。 【以往之技術】 以往，在短電弧放電燈的陰極上，係使用注入電子放 射性物質的高熔點金屬材料，例如使用將注入氧化鋰的鎢 材料也就是鋰鎢材。又，作爲該陰極形狀，係將圓柱狀材 料的前端部加工成圓錐狀，該陰極最前端係因應放電燈電 流來造成適當的電流密度而形成平坦或者是帶圓味的形狀 。在該短電弧放電燈中，點燈時亮度變得最高的地方係在 該陰極的前端附近。該陰極前端附近由於是在該陰極直徑 中直徑最小的部份，所以是形成電流密度最高的地方。 經濟部智慧財產局員工消費合作社印製 (讀先閲讀背面之注意事項再填寫本頁) 以往組裝有該短電弧放電燈之光學裝置，係被設計成 將陰極前端高亮度的部份，於該陰極的前端附近也就是亮 點部將該光學裝置聚焦，當安裝該短電弧放電燈時，一般 而言都會把放電燈的位置調整到該光學系照度最大的狀態 。可是，該短電弧放電燈會隨著點燈時間而逐漸耗損掉其 陰極，在前述陰極前端上可達到亮點部的位置，係放電燈 端的方向，例如將陰極配置在放電燈的下方則點燈時，由 於該亮點部的位置會隨著點燈時間而逐漸往下方後退，所 以該光學裝置會從最適的焦點偏移，有時從該光學系放射 本&張尺度適用中國國家標準( CNS ) A4規格(210X297公釐） " ~ 511116 A7 B7 五、發明説明（2 ) (請先閲讀背面之注意事項再填寫本頁} 出來的光會、造成極端的照度劣化的問題。一般認爲這是因 爲在該陰極前端的電流密度高，使該陰極的溫度也變得非 常的高的緣故。對於這個問題，以往雖然可以藉由不時的 調整該光學裝置的放電燈安裝位置來解決，但是不時的調 整不但麻煩，而且每次的調整除了要調整放電燈位置之外 ，還需要調整曝光時間等等，結果，會使工作時間大幅地 增加。 因此，作爲避免該陰極前端部的損耗的方法來增大陰 極的直徑，係使該陰極前端的電流密度降低。可是，若是 使電流密度降低的話，就會有該亮點的亮度本身會降低的 問題。再者，由於該短電弧放電燈本身的不穩定性會使放 射出來的光變得非常的不穩定，所以例如在曝光機等的操 作中，這會是由曝光面上的照度不均一所導致不順利的原 因，在投影機等的操作中這會是導致投影影像模糊浮影的 原因。 經濟部智慧財產局員工消費合作社印製 再者，會有如以下的問題。在該短電弧放電燈中所用 的該陰極材料中，通常是被添加了 2%氧化鋰的鎢棒材，也 就是使用鋰鎢材棒。這種氧化鋰是一種電子放射性物質， 由於在放電時很容易釋放出電子，所以在遍及於陰極前端 整體上，就時間上和空間上如果沒有均一地供給該氧化鋰 的話，就會發生亮點的放大或收縮，甚至是局部性放電集 中等的情形。該氧化鋰的供給，有藉由通過該鋰鎢材材料 的結晶粒之擴散來予以供給，也有藉由藉由析出於該陰極 表面的該氧化鋰的表面擴散來予以供給。對於藉由該表面 本紙張尺度適用中國國家標準（CNS ) A4規格（210 X 297公釐） - 511116 A7 B7 五、發明説明（3) 擴散的供給，例如專利第2782610號公報中所記載的，揭示 有在該陰極前端圓錐部表面的一部份中進行碳化處理程序 。可是，該方法因爲是在該陰極側面上提高所析出氧化鋰 的量，所以雖然確保了前述藉由表面擴散所得到的供給， 但是不會確保前述藉由結晶粒界所得到的供給。再者，該 氧化鋰的供給量不足的話會引起陰極前端部的亮點放大， 而相反的，該氧化鋰的供給量若是過剩的話，則會發生陰 極前端部的亮點收縮或者是電弧放電的模糊浮影的問題。 u 第5圖係顯示以往的短電弧放電燈上的陰極前端的結晶 狀態和電弧放電狀態的說明圖。第5 ( a )圖係以前端形狀 較細的以往的陰極上的放電狀態和該陰極的結晶狀態。在 該陰極前端部上的結晶粒徑係一種與導向棒側相同程度的 較細的結晶粒徑。像這樣比較細的結晶粒徑，係可以藉由 如前述般通過氧化鋰的結晶粒界的擴散所得到的供給而予 .以」活_化，在點燈初期會呈現供給過剩的狀態。因此，電弧 放電的狀態雖然是覆_蓋著前端部整體，但是該放電燈的穩 定性卻很低。而且，由於該陰極前端的徑很細，使該陰極 前端部的電流密度就會很高，所以該陰極前端部的耗損就 會很急遽，而在處於陰極前端位置後退等的狀態下的光學 系就會導致照度極端的低下的狀況。在此，於第5 ( b )圖 中，係顯示將前端徑狀與第5 ( a )圖作比較下，顯得更大 而使流通該陰極的電流密度降低的狀況。點燈初期陰極前 端部上的結晶粒徑會與第5 ( a )圖中的情況相同，而導，向 棒相同程度的比較細的粒徑的情況下會與第5 ( a)圖中的 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） ~' (請先閲讀背面之注意事項再填寫本頁) 訂 經濟部智慧財產局員工消費合作社印製 511116 A7 B7 五、發明説明（4) 情況相同，都會使電弧放電欠缺穩定性。再者’當圖中所 示的電弧放電爲偏向該陰極前端的一部份時，該電弧放電 就會被集中固定在陰極前端的局部，反而使該陰極前端的 〈溫度變得不均一，助長了該陰極的損耗。再者，由於該短 電弧放電燈本身的不穩定性會使放射出來的光變得非常的 不穩定，所以例如在曝光機等的操作中，這會是由於曝光 面上的照度不均一所導致不順利的原因，在投影機等的操 作中，這會是導致投影影像模糊浮影的原因。 【發明所欲解決之課題】 本發明之短電弧放電燈，係提供一種抑制短電弧放電 燈的陰極前端部的損耗，且藉由實現偏向短弧放電或該短 弧放電本身的閃爍量少之短弧放電燈，來防止在組進該短 電弧放電燈的裝置等之光照射面上的照度低落和閃爍不定 :。再者，即使在長期間點燈的情況下，也可以減少亮度之 劣化，且可放射出穩定的光。 【解決課題之手段】 一種短電弧放電燈，係具有略呈球狀的發光管，而在 該發光管內部陽極和陰極爲被互相對向地配置之短電弧放 電燈，其特徵爲：歐極前端部份的結晶構造係由比該陰極 的後端部位粗大化的複數個的結晶所構成，且在該陰極的 前端部份所含有的電子放射性物質爲質量比例0.1 %以下。 再者，其特徵係以含有氧化鋰來作爲電子放射性物質 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） (請先閲讀背面之注意事項再填寫本頁) 訂 經濟部智慧財產局員工消費合作社印製 -7· 511116 A7 _ _B7_ . 五、發明説明（5) 〇 又，其特徵爲，其結晶粒粗大化的部份的厚度，係自 最前端部起0.1mm至3.Omm處。 再者，係以在短電弧放電燈點燈時的陰極前端部的電 流密度爲30A/mm2至100 A/mm2爲特徵。 【發明的實施形態】 第1圖係本發明之短電弧放電燈之槪略圖。_石英玻璃製 略成球狀的燈泡部（1)兩端上有用來保持氣略呈圓 筒狀的密封部（2) 、（3)。該密封部（2) 、（3)jg用由鉬 等所構成的金屬箔，形成該密封部外徑之石英內側上 也就是被金屬箔密封，而在外部和電極之間連接通電。再 者，分別在該密封部（2 )、（3)上係被連接著由例如黃銅等 金屬所構成的圓筒狀的燈泡頭（4) 、（5)。又，在燈泡部 (1 )的內部中以約1.5X105Pa靜壓充塡例如氙氣之稀有氣體 ，而在該燈泡（1 )內部陽極（6 )和陰極（7 )係被對向配 置。該陽極（6)爲外徑25mm全長30mm略呈圓柱的形狀， 而在該陽極（6 )的前端部則是被加工成圓錐狀，正對最前 端部的該陽極的頭部上係設有直徑5mm的圓形平坦部。又， 該陰極（7)爲外徑15mm的圓柱形而該陰極前端部係頂部角 度被加工成60度的圓錐狀，正對最前端部之該陰極頭部上 係設有直徑1.5 mm的圓形平坦部。該陽極（6)和該陰極（7 )係分別藉由內部的導向棒（8 )、（ 9 )被加以保持，該 內部導向棒（8 ) 、（ 9 )係藉由密封部（2 ) 、（ 3 )保持 (請先閱讀背面之注意事項再填寫本頁) 訂 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準（CNS ) Α4規格（210X29*7公釐） -8- 511116 A7 B7 五、發明説明（6) ，並且持續地保有氣密性而與外部接電。本發明係關於這 種構造的短電弧放電燈，特別是以陰極（7 )爲其特徵。 (請先閲讀背面之注意事項再填寫本頁) 第2圖係顯示用在本發明中的陰極的結晶構造的說明圖 。從加工成該陰極（7 )的圓錐狀之內前端部（A )側起， 朝內部導向棒（9 )連接的一側達厚度d處，鋰鎢材的結晶 粒與該導向棒（9 )側的結晶粒相比之下則更形粗大化。在 專利申請範圍第1項中陰極的前端部分，係指該結晶粒粗大 化的部分而言。該粗大化的程度，例如當前端徑爲1.5mm的 陰極時，由數個到十數個複數個的結晶粒被緊縮所成的粗 大化。這種程度的結晶粒粗大化會在結晶粒界擴散，使作 爲被供給的氧化鋰的量時，該氧化鋰的供給量既不會供給 短缺，也不會供給過剩，而維持在適當的量，而可以得到 理想中穩定的短電弧放電燈。 經濟部智慧財產局員工消費合作社印製 又，在該陰極（7 )前端部也就是該粗大結晶粒中，所 含有的氧化鋰的量爲質量比例0.1 %以下。被使用在該陰極 (7 )中的鋰鎢材係含有氧化鋰質量比例約2%的物質，例如 在該陰極（7 )的內部導向棒（9 )側，係將含有氧化鋰質 量比例約2%的狀態持續保持不變。可是，針對該陰極前端 ，必須使該結晶粒徑粗大化，且必須使該粗大化的結晶粒 中所含有的氧化鋰作成質量比例爲0.1 %以下。再者，最理 想的是在點燈初期並不含有該氧化鋰。這是爲了特別是在 短電弧放電燈點燈初期用來減少氧化鋰被供給過剩的效果 的緣故。又，若是該氧化鋰的含量在0.1 %以上的話，則會 引起該氧化鋰的過剩供給，有時會造成電弧放電的局部集 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） 7〇Z ' 511116 A7 B7 五、發明説明（7) cju 〇 (請先閲讀背面之注意事項再填寫本頁) 在該陰極前端所形成的粗大化結晶粒的厚度d，最理想 的是在0.1mm到3.0mm的範圍，這是使該電弧放電穩定的適 當範圍。該厚度d若是在0 · 1 m m以下的話，則從被形成於該 陰極前端的粗大化鋰鎢材結晶的結晶粒界藉由擴散所被供 給的氧化鋰的量就會過剩，而無法得到穩定的電弧放電。 又，相反地，若是該厚度d爲3.0mm以上的話，則從結晶粒 界所供給的氧化鋰的量就會不足，該陰極前端的亮點會發 散到必要的水準以上，使得當光學系採光時會產生光量不 足等的不順利的情形。 經濟部智慧財產局員工消費合作社印製 在第2圖中所示的實施例，該陰極前端徑爲0 l.5mm， 點燈電流約88A，陰極前端的電流密度約50A/mm2。該電流 密度與該陰極前端的損耗有很深的關係，該陰極前端的電 流密度以30A/mm2到100A/mm2的範圍爲適當的値。該電流密 度若是升高到100A/mm2以上的話，該陰極前端的溫度就會 升高，使該陰極前端急遽地損耗。又，若是在30A/mm2以下 的話，則該陰極前端部整體而均一的放電會無法散開，局 部的電弧放電就會集中起來，而無法得到穩定的光。 第3圖係顯示用來製作該粗大化結晶粒的直流放電裝置 的槪略圖。該處理裝置係從被設置在石英玻璃管所組成的 處理槽（10 )的一端的稀有氣體流入口，將例如氬氣等的 稀有氣體流入數十秒左右，將該處理槽（1 〇 )內的空氣用 該稀有氣體來加以置換。在該處理槽（10)內，插進電極 保持棒（1 2 )而被保持的前述短電弧放電燈用的陰極（7 ) 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） ^ 511116 A7 B7_ 五、發明説明（8) ，係被安裝在該裝置的正電荷側（陽極側）。又，在該裝 置的負電荷側（陰極側）上係被安裝有針狀陰極（1 3 )， 可以用來調整被處理物也就是陰極（7 )的位置。該陰極（ 7 )，係在以電極保持棒（1 2 )加以保持的狀態下，透過旋 轉機構部（14)、受電板（15)、供電電刷（16)，連接 在直流電源（17 )的正極側。再者，該直流電源的負極側 則是連接在前述針狀電極（1 3 )的一端。 該粗大化的結晶粒可製作如下。亦即，在直流放電處 理裝置上，將作爲前述短電弧放電燈用的陰極（7)來使用 的鋰鎢材製的電極安裝在該裝置的陽極側，流通稀有氣體 例如氬氣，在該氣流中使該陰極（7 )旋轉同時使在該陰極 (7 )前端部和針狀陰極（1 3 )之間發生放電。該陰極（7 )係於該直流放電處理裝置中藉由施加放電電流例如70A來 加熱，使之升溫至鋰鎢材材料的熔點（約3380°C )。藉由 該放電處理，被處理物也就是該陰極（7 )的前端會熔融， 在該加熱處理後就可以生成粗大化的結晶粒。再者，該陰 極（7 )前端的結晶粒大小係·控制著在該直流放電處理裝置 中的放電電流，可藉由使相當於該陰極（7 )的處理部份的 地方的溫度變化來產生。例如，將要升溫到約3000°C的升 溫期間維持數秒後再升溫到鋰鎢材的熔點，可以藉由維持 言亥溫度數秒的處理方式反復進行數次來予以調節。 又’藉由該加熱處理，由於使該陰極前端部份熔融， 所以該陰極的母材也就是鋰鎢材中所含有的氧化鋰也會和 該加熱處理同時蒸發，而其中的大半部份會朝該陰極的外 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） mmmmmma mmmmmmms nn mMmmmmmmi Ammmmlmm tammmmmmmm eamMMmmmm 11 (請先閲讀背面之注意事項再填寫本頁) 訂 經濟部智慧財產局員工消費合作社印製 -11 - 511116 A7 B7_ 五、發明説明（9) (請先閱讀背面之注意事項再填寫本頁) 部放出。藉此，在該陰極前端部所形成的粗大化的結晶粒 中所含有的電子放射性物質也就是氧化鋰的量會減低到〇·1 %以下。該陰極前端部份也就是粗大化的複數個結晶粒所組 成的部份中由於氧化鋰的含量減少，所以該氧化鋰就不會 供給過剩，而且從複數個的結晶粒的結晶粒界，藉由粒界 擴散，由於藉由從該陰極後方所供給的該氧化鋰不會有供 給短缺的狀況，所以可以提供穩定的電弧放電。 至於組裝有該陰極（7 )的短電弧放電燈，與使用以往 的陰極時的點燈狀況作比較。在該短電弧放電燈上，將水 銀30mg/cc、稀有氣體氙氣以2.0X102Pa的靜壓封入燈泡中。 又，以該放電燈的電極間距離5mm、輸入電力4300W來加以 點燈。. 經濟部智慧財產局員工消費合作社印製 當該短電弧放電燈點燈時，陰極前端會隨著點燈時間 而消耗，因爲會逐漸地變成帶圓味的形狀，所以點燈初期 後，該陰極前端部的形狀會有很大的變化。因此，如第4圖 所示，規定該陰極前端的後退量或前端徑的變化來加以測 .定。亦即，在第4 ( a )圖的陰極前端擴大圖中，在該前端 徑（2 1 )上對陰極（7 )的長軸方向也就是陰極軸，將傾斜 45度的假想線（22)所組成的接線和該陰極（7)所成的交 點所結合的線，作爲前端徑（21 )來加以規範。又，如第4 (b)圖中所記載，前端的後退量，係規定爲將該陰極（7b )的導向棒側作爲基準的陰極最前端部，也就是到同圖白勺 點P2爲止的距離L2與到初期陰極（7a)最前端部？1爲止的 距離L1兩者之間的差L3，來加以測定。 本衹張尺度適用中國國家標準（CNS ) A4規格(210X297公釐） ΓΐΟ _ ' - 511116 A7 _B7_ 五、發明説明（id (請先閲讀背面之注意事項再填寫本頁) 第6圖係針對使用該陰極的短電弧放電燈上的點燈時間 之陰極前端的損耗量的比較圖。同圖的縱軸係表示陰極前 端後退量的長度，橫軸係該短電弧放電燈的點燈時間。若 是以點燈時間爲500小時來和以往的陰極前端後退量作比較 的話/，會有約1/2的變化量也就是0.2mm的後退量。 第7圖係表示相對於使用該陰極的放電燈的點燈時間之 前端直徑增大量的比較圖。同圖的縱軸係將陰極前端徑的 增大量以相對値表示，橫軸係表示該短電弧放電燈的點燈 時間。在點燈時間爲500小時的情況下，相對於以往的陰極 與初期相比前端徑約增大2倍，本發明的陰極與初期相比前 端徑約只增大1/2倍。 【發明之效果】 經濟部智慧財產局員工消費合作社印製 藉由在短電弧放電燈陰極前端部上形成氧化鋰含量0-1 %以下也就是形成鎢的粗大結晶粒，來抑制該短電弧放電燈 陰極前端由點燈所造成的損耗。再者，針對組裝有該短電 弧放電燈的裝置，可以提供一種減少自光學系焦點的亮點 偏移或藉由亮點放大的照射面上的照度降低的問題，而可 以得到在歷經長時間後仍保持穩定亮度的短電弧放電燈。 【圖式之簡單說明】 第1圖係本發明之短電弧放電燈之槪略圖。 第2圖係顯示用在本發明中的陰極的結晶構造的槪略圖 -13- 本紙張尺度適用中國國家標準（CNS ) A4規格（210X29*7公釐） 511116 A7 B7 五、發明説明（n) 第3圖係將本發明之陰極加以放電處理之直流放電裝置 之槪略圖 (請先閲讀背面之注意事項再填寫本頁) 煙b) 第以往的短電弧放電燈上的陰極前端的結晶 狀態和電弧放電狀態的說明圖。 第6圖係本發明所實施的由放電燈上的點燈時間之陰極 前端的損耗量比較圖。 第7圖係本發明所實施的由放電燈上的點燈時間之陰極 前端直徑增大量的比較圖。 【符號說明】 經濟部智慧財產局員工消費合作社印製 1、燈泡部。2、3、密封部。4、5、燈泡頭。6、陽極 。7、7a、7b、陰極。8、9、內部導向棒。A、陰極前端部 份。d、結晶粒粗大化的厚度。1 〇、處理槽。1 1、稀有氣體 流入口。1 2、電極保持棒。1 3、針狀陰極。1 4、旋轉機構 。1 5、受電板。1 6、！供電電刷。17、直流電源。21、前端直 徑。22、相對於極軸呈45。的假想線。23、陰極軸。P、P1 、P2、最前端部。L 1、L2、到陰極前端爲止之間的距離。L 、陰極後退距離。 -14 - 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐）511116 A7 B7 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a light source or an image projection system used in a photolithography process for manufacturing a semiconductor or a liquid crystal panel, etc. The light source for a projector such as a digital microscope element or a liquid crystal is more specifically an electrode of a short arc discharge lamp. [Previous technology] In the past, high-melting-point metal materials injecting electron-emitting substances were used as cathodes of short-arc discharge lamps. For example, a tungsten material that is implanted with lithium oxide, that is, a lithium tungsten material. In addition, as the shape of the cathode, the front end portion of a cylindrical material is processed into a cone shape, and the foremost end of the cathode is formed into a flat or rounded shape due to the appropriate current density caused by the discharge lamp current. In this short arc discharge lamp, the place where the brightness becomes the highest at the time of lighting is near the front end of the cathode. Since the vicinity of the front end of the cathode is the smallest diameter portion of the cathode diameter, it is the place where the highest current density is formed. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs (read the precautions on the back before filling this page). The optical device in which the short arc discharge lamp was previously assembled was designed to make the front end of the cathode with high brightness. The optical device is focused near the front end of the cathode, that is, the bright spot. When the short arc discharge lamp is installed, the position of the discharge lamp is generally adjusted to the state where the optical system has the maximum illuminance. However, the short arc discharge lamp gradually loses its cathode with the lighting time, and the position of the bright spot on the front end of the cathode is the direction of the discharge lamp end. For example, when the cathode is arranged below the discharge lamp, it is turned on. Since the position of the bright spot will gradually recede downward with the lighting time, the optical device will shift from the optimum focus, and sometimes the optical system & Zhang scale from the optical system applies the Chinese National Standard (CNS) A4 specifications (210X297 mm) " ~ 511116 A7 B7 V. Description of the invention (2) (Please read the precautions on the back before filling out this page} The light emitted will cause extreme illuminance degradation. Generally considered this This is because the current density at the front end of the cathode is high and the temperature of the cathode becomes very high. Although this problem can be solved by adjusting the installation position of the discharge lamp of the optical device from time to time, The adjustment from time to time is not only cumbersome, but in addition to adjusting the position of the discharge lamp, each adjustment also needs to adjust the exposure time, etc. As a result, it will make the working time The width increases. Therefore, increasing the diameter of the cathode as a way to avoid the loss of the front end of the cathode reduces the current density at the front end of the cathode. However, if the current density is reduced, the brightness of the bright spot itself is present. The problem will be reduced. In addition, due to the instability of the short arc discharge lamp itself, the emitted light becomes very unstable. Therefore, for example, in the operation of an exposure machine, this is caused by the illuminance on the exposure surface. The cause of the unevenness caused by the unevenness is the cause of the blurred image of the projected image in the operation of the projector, etc. Furthermore, the employee's consumer cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs will print the following problems. In this short arc The cathode material used in the discharge lamp is usually a tungsten rod with 2% lithium oxide added, that is, a lithium tungsten rod. This lithium oxide is an electronic radioactive substance and is easily released during discharge. Electrons, so if the lithium oxide is not uniformly supplied in time and space throughout the entire front end of the cathode, Bright spots are enlarged or contracted, or even localized discharges are concentrated. The supply of lithium oxide is supplied by diffusion of crystal particles of the lithium tungsten material, or by precipitation on the surface of the cathode. The surface diffusion of the lithium oxide is supplied. For the paper size of the surface, the Chinese National Standard (CNS) A4 (210 X 297 mm)-511116 A7 B7 is applied. 5. Description of the invention (3) Supply of diffusion, For example, as disclosed in Patent No. 2782610, it is disclosed that a carbonization process is performed on a part of the surface of the conical portion of the front end of the cathode. However, this method increases the amount of precipitated lithium oxide on the side of the cathode. Although the aforementioned supply obtained by surface diffusion is ensured, the aforementioned supply obtained by crystal grain boundaries is not ensured. In addition, if the supply amount of the lithium oxide is insufficient, the bright spot on the front end of the cathode will be enlarged. On the contrary, if the supply amount of the lithium oxide is excessive, the bright spot shrinkage of the front end of the cathode will shrink or the fuzzy floating of the arc discharge will occur. Shadow problem. u Fig. 5 is an explanatory diagram showing a crystalline state and an arc discharge state of a cathode front end of a conventional short arc discharge lamp. Fig. 5 (a) shows the state of discharge on a conventional cathode with a thinner tip and the state of crystallization of the cathode. The crystal grain size on the front end portion of the cathode is a finer crystal grain size to the same extent as the guide rod side. The relatively fine crystal grain size like this can be activated by the supply obtained by the diffusion of the crystal grain boundaries of lithium oxide as described above, and the state of excess supply will appear in the initial stage of lighting. Therefore, although the state of the arc discharge covers the entire front end portion, the stability of the discharge lamp is low. In addition, because the diameter of the front end of the cathode is very small, the current density of the front end of the cathode will be very high, so the wear of the front end of the cathode will be very rapid, and the optical system in the state where the front end of the cathode is retracted, etc. This can lead to extremely low illumination. Here, Fig. 5 (b) shows a situation where the diameter of the front end is larger than that of Fig. 5 (a) and the current density flowing through the cathode is reduced. In the initial stage of lighting, the crystal grain size on the front end of the cathode will be the same as that in Fig. 5 (a), and the case where the relatively fine grain diameter of the rod is the same as that in Fig. 5 (a) This paper size applies Chinese National Standard (CNS) A4 specification (210X297 mm) ~ '(Please read the notes on the back before filling this page) Order printed by the Intellectual Property Bureau of the Ministry of Economic Affairs and the Consumer Cooperatives 511116 A7 B7 V. Description of the invention (4) The same situation will make the arc discharge less stable. Furthermore, when the arc discharge shown in the figure is a part deviating to the front end of the cathode, the arc discharge will be concentrated and fixed on a part of the front end of the cathode, instead, the <temperature of the front end of the cathode becomes uneven and promotes The loss of the cathode. Furthermore, since the instability of the short arc discharge lamp itself makes the emitted light very unstable, it may be caused by uneven illumination on the exposure surface, for example, in the operation of an exposure machine or the like. The reason for the smoothness is that, in the operation of the projector, etc., this may cause the projected image to blur and float. [Problems to be Solved by the Invention] The short arc discharge lamp of the present invention provides a method for suppressing the loss of the front end portion of the cathode of the short arc discharge lamp, and realizing the short arc discharge or a small amount of flicker of the short arc discharge itself. Short-arc discharge lamp to prevent the illuminance and flicker on the light-irradiating surface of the device and other devices incorporating the short-arc discharge lamp. Furthermore, even when the light is turned on for a long period of time, it is possible to reduce deterioration in brightness and emit stable light. [Means for solving the problem] A short arc discharge lamp is a light bulb with a slightly spherical shape, and the anode and the cathode are short arc discharge lamps arranged opposite to each other in the light bulb, which are characterized by: The crystal structure of the front end portion is composed of a plurality of crystals coarser than the rear end portion of the cathode, and the electron radioactive material contained in the front end portion of the cathode is 0.1% by mass or less. Furthermore, its characteristics are based on the inclusion of lithium oxide as an electronic radioactive substance. The paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) (please read the precautions on the back before filling this page). Order the intellectual property of the Ministry of Economic Affairs Printed by the Bureau ’s Consumer Cooperative -7 · 511116 A7 _ _B7_. 5. Description of the invention (5) 〇 Also, it is characterized in that the thickness of the coarsened part of the crystal grains is 0.1mm to 3 from the foremost part. Omm. Furthermore, it is characterized in that the current density at the front end portion of the cathode when the short arc discharge lamp is lit is 30 A / mm2 to 100 A / mm2. [Embodiment of the invention] Fig. 1 is a schematic diagram of a short arc discharge lamp of the present invention. _Spherical bulb (1) made of quartz glass has sealing parts (2) and (3) at both ends to hold a slightly cylindrical shape. The sealing portions (2) and (3) jg are made of metal foil made of molybdenum, etc., and the inside of the quartz which forms the outer diameter of the sealing portion is sealed by the metal foil, and current is connected between the outside and the electrode. Furthermore, cylindrical bulb heads (4) and (5) made of metal such as brass are connected to the sealing portions (2) and (3), respectively. In addition, a rare gas such as xenon is filled with static pressure of about 1.5 × 105 Pa in the interior of the bulb portion (1), and the anode (6) and the cathode (7) inside the bulb (1) are opposed to each other. The anode (6) has a slightly cylindrical shape with an outer diameter of 25mm and a total length of 30mm, and the front end portion of the anode (6) is processed into a cone shape. A circular flat portion with a diameter of 5mm. In addition, the cathode (7) is cylindrical with an outer diameter of 15 mm, and the front end of the cathode is processed into a conical shape with a top angle of 60 degrees. A circle of 1.5 mm in diameter is provided on the cathode head facing the foremost end.形 平面 部。 Shaped flat portion. The anode (6) and the cathode (7) are held by internal guide rods (8) and (9), respectively, and the internal guide rods (8) and (9) are held by sealing portions (2), (3) Keep (Please read the precautions on the back before filling out this page) Order printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, Consumer Cooperatives This paper is printed in accordance with the Chinese National Standard (CNS) Α4 specification (210X29 * 7 mm) -8- 511116 A7 B7 V. Description of the invention (6), and it keeps air tightness and is connected to the outside. The present invention relates to a short-arc discharge lamp having such a structure, and is particularly characterized by a cathode (7). (Please read the precautions on the back before filling out this page.) Figure 2 is an explanatory diagram showing the crystal structure of the cathode used in the present invention. From the side of the conical inner front end (A) processed into the cathode (7), toward the side where the inner guide rod (9) is connected to a thickness d, the crystal particles of the lithium tungsten material and the guide rod (9) The crystal grains on the side are more coarse and coarse in comparison. The front end portion of the cathode in the scope of patent application item 1 refers to the portion where the crystal grains are coarsened. The degree of coarsening is, for example, a coarsening in which a plurality of crystal grains to ten or more crystal grains are compacted when a cathode having a current end diameter of 1.5 mm is used. This degree of coarsening of crystal grains will diffuse at the crystal grain boundary, so that when the amount of lithium oxide to be supplied is not in short supply or excessive, it will be maintained at an appropriate amount. , And an ideally stable short arc discharge lamp can be obtained. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. Also, the front end of the cathode (7), which is the coarse crystal grains, contains lithium oxide in an amount of 0.1% by mass or less. The lithium tungsten material used in the cathode (7) contains about 2% by mass of lithium oxide. For example, on the inner guide rod (9) side of the cathode (7), it contains about 2% by mass of lithium oxide. The status of% remains constant. However, for the cathode front end, the crystal grain size must be coarsened, and the mass ratio of lithium oxide contained in the coarsened crystal grains must be 0.1% or less. Furthermore, it is most desirable that the lithium oxide is not contained in the initial stage of lighting. This is for the purpose of reducing the effect of excessive supply of lithium oxide, especially in the initial stage of the short arc discharge lamp lighting. In addition, if the lithium oxide content is above 0.1%, an excessive supply of the lithium oxide may be caused, and a local collection of arc discharge may sometimes cause the paper size to comply with the Chinese National Standard (CNS) A4 specification (210X297 mm). 7〇Z '511116 A7 B7 V. Description of the invention (7) cju 〇 (Please read the precautions on the back before filling this page) The thickness d of the coarsened crystal grains formed at the front end of the cathode is most preferably 0.1 The range of mm to 3.0 mm is a suitable range for stabilizing the arc discharge. If the thickness d is less than or equal to 0.1 mm, the amount of lithium oxide supplied from the crystal grain boundaries of the coarsened lithium tungsten material crystals formed at the front end of the cathode by diffusion will be excessive and cannot be stabilized. Arc discharge. On the other hand, if the thickness d is 3.0 mm or more, the amount of lithium oxide supplied from the crystal grain boundary will be insufficient, and the bright point at the front end of the cathode will diverge to a necessary level or more. Unsuccessful situations such as lack of light may occur. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs In the embodiment shown in FIG. 2, the diameter of the front end of the cathode is 0 1.5 mm, the lighting current is about 88 A, and the current density at the front end of the cathode is about 50 A / mm2. The current density has a deep relationship with the loss at the front end of the cathode, and the current density at the front end of the cathode is suitably in the range of 30 A / mm2 to 100 A / mm2. If the current density rises above 100 A / mm2, the temperature at the front end of the cathode will rise, causing the front end of the cathode to be rapidly consumed. If it is 30 A / mm2 or less, the uniform and uniform discharge of the entire front end portion of the cathode cannot be dispersed, and the partial arc discharge is concentrated, and stable light cannot be obtained. Fig. 3 is a schematic view showing a DC discharge device for producing the coarsened crystal grains. This processing device flows a rare gas such as argon into the processing tank (10) from a rare gas inflow port provided at one end of a processing tank (10) composed of a quartz glass tube, and places the processing tank (10) in the processing tank (10). The rare air is replaced with this rare gas. In the processing tank (10), the cathode (7) for the short-arc discharge lamp described above is inserted and held by the electrode holding rod (1 2). The paper size is in accordance with the Chinese National Standard (CNS) A4 (210X297 mm). ^ 511116 A7 B7_ V. Description of the invention (8) is installed on the positive charge side (anode side) of the device. In addition, a needle-like cathode (1 3) is mounted on the negative charge side (cathode side) of the device, and can be used to adjust the position of the object to be processed, that is, the cathode (7). The cathode (7) is connected to a DC power source (17) through a rotating mechanism (14), a power receiving plate (15), and a power supply brush (16) in a state held by an electrode holding rod (1 2). Positive side. The negative side of the DC power supply is connected to one end of the needle electrode (1 3). The coarsened crystal grains can be prepared as follows. That is, in a DC discharge processing device, an electrode made of a lithium tungsten material used as the cathode (7) for the short-arc discharge lamp is mounted on the anode side of the device, and a rare gas such as argon flows through the gas flow. While rotating the cathode (7), a discharge occurs between the front end of the cathode (7) and the needle-like cathode (1 3). The cathode (7) is heated in the DC discharge processing device by applying a discharge current, such as 70A, to raise the temperature to the melting point (about 3380 ° C) of the lithium tungsten material. By this discharge treatment, the to-be-processed object, that is, the tip of the cathode (7) is melted, and coarsened crystal grains can be generated after the heat treatment. Furthermore, the size of crystal grains at the front end of the cathode (7) controls the discharge current in the DC discharge processing device, and can be generated by changing the temperature of the place corresponding to the processing part of the cathode (7). . For example, the temperature rising period to about 3000 ° C is maintained for a few seconds, and then the temperature is raised to the melting point of the lithium tungsten material, which can be adjusted by repeating the process of maintaining the temperature for several seconds. And by the heat treatment, because the front end portion of the cathode is melted, the lithium oxide contained in the base material of the cathode, that is, the lithium tungsten material, will also evaporate at the same time as the heat treatment, and most of it will The size of the paper facing the cathode applies Chinese National Standard (CNS) A4 (210X297 mm) mmmmmma mmmmmmms nn mMmmmmmmi Ammmmlmm tammmmmmmm eamMMmmmm 11 (Please read the precautions on the back before filling this page) Order the staff of the Intellectual Property Bureau of the Ministry of Economic Affairs Printed by Consumer Cooperatives -11-511116 A7 B7_ V. Description of Invention (9) (Please read the notes on the back before filling this page). Thereby, the amount of the electron radioactive substance, that is, lithium oxide, contained in the coarsened crystal grains formed at the front end portion of the cathode can be reduced to less than 0.1%. Since the front end of the cathode is a portion composed of a plurality of coarsened crystal grains, since the lithium oxide content is reduced, the lithium oxide will not be supplied in excess, and from the crystal grain boundaries of the plurality of crystal grains, Diffusion from the grain boundary does not cause a shortage of supply by the lithium oxide supplied from behind the cathode, so that stable arc discharge can be provided. The short-arc discharge lamp incorporating this cathode (7) is compared with the lighting condition when a conventional cathode is used. In this short-arc discharge lamp, 30 mg / cc of mercury and xenon, a rare gas, were sealed in the bulb at a static pressure of 2.0 × 102 Pa. The discharge lamp was lit with a distance between the electrodes of 5 mm and an input power of 4300 W. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. When the short arc discharge lamp is turned on, the front end of the cathode will be consumed with the lighting time, because it will gradually become a round shape, so after the initial lighting, the The shape of the front end of the cathode varies greatly. Therefore, as shown in Fig. 4, the change in the amount of retreat of the front end of the cathode or the change in the diameter of the front end is determined and measured. That is, in the enlarged view of the front end of the cathode in FIG. 4 (a), the imaginary line (22) inclined to the major axis of the cathode (7) on the front end diameter (2 1), that is, the cathode axis, is inclined at 45 degrees. The line formed by the combined wiring and the intersection formed by the cathode (7) is regulated as the front end diameter (21). In addition, as shown in FIG. 4 (b), the amount of receding of the front end is defined as the front end of the cathode using the guide rod side of the cathode (7b) as the reference, that is, to the point P2 in the same figure. Distance L2 to the foremost end of the initial cathode (7a)? The difference L3 between the distances L1 to 1 is measured. The size of this sheet is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) ΓΐΟ _ '-511116 A7 _B7_ V. Description of the invention (id (please read the precautions on the back before filling this page) Figure 6 is for use A comparison chart of the amount of loss at the front end of the cathode during the lighting time of the short arc discharge lamp of this cathode. The vertical axis of the same figure shows the length of the back end of the cathode, and the horizontal axis is the lighting time of the short arc discharge lamp. When the lighting time is 500 hours, and compared with the conventional front-end receding amount of cathode /, there will be a change of about 1/2, that is, a 0.2-mm receding amount. Figure 7 shows the discharge lamp with this cathode. A comparison chart of the increase in diameter at the front end of the lighting time. The vertical axis of the same graph represents the increase in the diameter of the front end of the cathode as relative ，, and the horizontal axis represents the lighting time of the short arc discharge lamp. The lighting time is In the case of 500 hours, the front end diameter of the cathode of the present invention is approximately doubled compared to the initial stage, and the front end diameter of the cathode of the present invention is only approximately 1/2 times of the initial stage. Consumption of property staff Cooperative printing suppresses the loss caused by the lighting of the cathode front end of the short arc discharge lamp by forming coarse oxide grains with a lithium oxide content of 0-1% or less, that is, tungsten on the front end of the cathode of the short arc discharge lamp. For the device in which the short arc discharge lamp is assembled, it can provide a problem of reducing the deviation of the bright spot from the focal point of the optical system or the decrease in the illuminance on the illuminated surface amplified by the bright spot, and it can be maintained after a long period of time. Short arc discharge lamp with stable brightness. [Simplified description of the drawing] Figure 1 is a schematic diagram of the short arc discharge lamp of the present invention. Figure 2 is a schematic diagram of the crystalline structure of the cathode used in the present invention. -This paper size is in accordance with Chinese National Standard (CNS) A4 (210X29 * 7mm) 511116 A7 B7 V. Description of the invention (n) Figure 3 is a schematic diagram of a DC discharge device in which the cathode of the present invention is discharged ( Please read the precautions on the back before filling out this page) Smoke b) Explanatory diagram of the crystalline state and arc discharge state of the cathode front end of the conventional short arc discharge lamp. Fig. 6 is a comparison diagram of the amount of loss at the tip of the cathode from the lighting time on the discharge lamp according to the present invention. Fig. 7 is a comparison diagram of the increase in the diameter of the front end of the cathode from the lighting time on the discharge lamp according to the present invention. [Symbol description] Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 1. Bulb Department. 2, 3, sealing section. 4, 5, bulb head. 6. Anode. 7, 7a, 7b, cathode. 8, 9, internal guide rod. A. The front part of the cathode. d. Thickness of crystal grains. 1 〇, processing tank. 1 1. Rare gas flow inlet. 1 2. Electrode holding rod. 1 3. Needle cathode. 1 4. Rotating mechanism. 1 5. Power receiving board. 1 6! Powered brushes. 17. DC power supply. 21. Front diameter. 22. 45 with respect to the polar axis. Imaginary line. 23. Cathode shaft. P, P1, P2, foremost portion. L 1, L2, the distance to the front end of the cathode. L. Cathode retreat distance. -14-This paper size applies to Chinese National Standard (CNS) A4 (210X297 mm)