201212092 六、發明說明： 【發明所屬之技術領域】 本發明係關於螢光燈，尤其關於放射真空紫外光的螢 光燈。 【先前技術】 自以往以來，紫外線被適當利用在光化學反應、殺菌 或有機物的分解等。以如上所示之紫外線光源而言，係大 部分使用低壓水銀燈，但是近來如日本特開2 0 0 1 _ 0 1 5 0 7 8 號公報（專利文獻1 )所示亦已提出一種利用介電質障壁 放電的螢光燈。 該專利文獻1所記載之螢光燈係在發光管的內部封入 稀有氣體，在一對電極間發生介在有介電質的放電，藉此 激發稀有氣體而放射紫外光（真空紫外光），激發形成在 發光管的內表面全面的螢光體，而得預定波長領域（真空 紫外領域）的紫外光。 此外，在日本特開2010-153054號公報（專利文獻2) 中係揭示一種在發光管的外側具備有至少1個外部電極的 螢光燈，其藉由設置孔徑部來具有指向性。 在該專利文獻2中，以其具體例而言，係揭示出形成 在發光管內面的螢光體層係在其圓周方向的一部分設置未 形成有該螢光體層的領域而形成爲孔徑部者；或者使螢光 體層的圓周方向的一部分比其他部分更爲薄壁，而將該薄 壁部分形成爲孔徑部者。 -5- 201212092 但是，在上述螢光燈中，因螢光體被曝露在放電空間 而容易發生劣化，不易使照度安定維持長時間。以螢光體 劣化的主要劣化原因而言，係考慮有因不純氣體（H20、 co2等）所致者，但是尤其在利用介電質障壁放電時，基 於其放電原理，放電形成在穿越發光管的方向，因此尤其 會有螢光體的損傷大、且不易獲得充分的光安定性的問題 [先前技術文獻] [專利文獻] [專利文獻1]日本特開2001-015078號公報 [專利文獻2]日本特開201 0-1 53054號公報 【發明內容】 (發明所欲解決之課題） 本發明所欲解決的課題係鑑於上述習知技術的問題點 ，提供一種構造係具備有：在內部被封入有含有氙的放電 氣體的發光管；被形成在該發光管的長度方向，且透過介 電質而相對向的一對電極；及形成在前述發光管的內面的 內部螢光體層，在前述發光管的圓周方向的一部分形成有 未形成該內部螢光體層的孔徑部的螢光燈，其避免因螢光 體層放電所造成的劣化而將光安定度維持地較高，且加長 螢光燈之使用壽命者。 201212092 (解決課題之手段） 本發明係鑑於上述習知技術的問題點，爲了解決上述 課題，其特徵爲：以覆蓋發光管的方式配設外管，並且在 前述發光管之與前述孔徑部相對應的外表面上形成外部螢 光體層而成。 此外，其特徵爲··在前述發光管與前述外管之間塡充 有惰性氣體。 此外，其特徵爲：使前述外部螢光體層的厚度小於前 述內部螢光體的厚度。 再者，其特徵爲：前述內部螢光體或前述外部螢光體 層的至少一方含有LaP04: Nd螢光體或YP04: Nd螢光體的 任一者。 (發明之效果） 根據本發明之螢光燈，藉由發光管的孔徑部的外表面 上的外部螢光體，與僅形成有孔徑部的燈相比較，可使其 光輸出增大，並且該外部螢光體層不會有被曝露在放電的 情形，因此不易發生劣化。因此，由螢光燈中的外部螢光 體層所被放射的光係可將光安定性維持爲較高’且可加長 螢光燈的使用壽命。 此外，由於外部螢光體層處於惰性氣體雰圍氣中，因 此其更加不易發生劣化。 此外，藉由使外部螢光體層形成爲比內部螢光體層更 爲薄壁，可一面使螢光燈具有指向性，一面可對被照射物 201212092 效率佳地照射光。 以螢光體層而言，藉由含有LaP04: Nd螢光體或ΥΡ04 :Nd螢光體的任一者而放射波長190nm附近的光，可適於 利.用爲光化學反應、殺菌或有機物的分解.等_的光源。 【實施方式】 第1圖係本發明之螢光燈的剖面圖。 在圖中，螢光燈1係在發光管2的外周面上相對向配置 有一對外部電極3、3。該外部電極3、3係呈朝向管軸向延 伸的槪略帶狀形狀，由例如將銀（Ag )與燒結玻璃混合而 成的銀膏、或將金（Au)與燒結玻璃混合而成的金膏等導 電膜所形成。 在前述外部電極3、3上被覆有由玻璃層所構成的保護 膜4、4，在該外部電極3、3分別連接有引線W 1、W2，該 等與發生高頻電壓的電源10相連接。 前述發光管2係由對波長2 00mm以下的真空紫外光的 透射性高的合成石英玻璃所構成。此外，爲了使得紫外線 照度維持率更爲良好，以使用OH基含有量高的合成石英 玻璃爲佳，例如可使用信越石英製F3 1 0。 接著，在該發光管2內係被封入有稀有氣體作爲放電 氣體，以稀有氣體而言，係可爲僅有氙、或者氙與其他稀 有氣體的混合氣體的任一者。 . 如第2圖詳細所示，在發光管2的內表面形成有內部螢 光體層5。 -8 - 201212092 該內部營光體層5係在發光管2的圓周方向的一部分中 有未形成有前述內部螢光體層5的區域，該部分形成孔徑 部6。 其中，在發光管2與內部螢光體層5之間，除了孔徑部 6以外，亦可形成紫外線反射膜（未圖示）。 在前述發光管2的外周圍係以覆蓋的方式以同芯狀配 設有外管7，在該等之間的空間係被塡充有氮氣（N2 )、 氬氣（Ar )等惰性氣體。該外管7係對藉由螢光體所被轉 換的特定波長領域的光具備有透射性者。以螢光體而言， 若使用放射波長200nm以下的光的特性者時，以材質而言 ，以使用合成石英玻璃爲宜。 接著，在前述發光管2之與孔徑部6相對應的外表面上 形成有外部螢光體層8。 前述內部螢光體層5及外部螢光體層8係藉由利用氙的 發光所被放射出的波長172nm而被激發，而放射按照其特 性之波長領域的光者。若放射波長200nm以下的光，例如 190nm的光時，較佳爲使用以銨所被賦活的LaP04螢光體 、或以鈸所被賦活的YP〇4。其中，钕賦活LaP〇4螢光體具 體而言爲（Lai-x，Ndx)P04 (其中，x = 0.01〜0.1 1 )，鈸賦活 丫？〇4螢光體具體而言爲（丫1〜心![)?04(其中，？{ = 〇.〇1〜 0.11)。 接著，內部螢光體層5的厚度爲例如10〜70 μιη，較佳 爲30〜50μιη，外部螢光體層8的厚度係比其爲更薄，例如5 〜1〇μηι。如上所示，藉由使兩螢光體層5、8的厚度爲不同 -9 - 201212092 ，可形成按照該差異的指向性。 在上述構成中，若由高頻電源10對外部電極3、3施加 高頻高電壓時，在該外部電極3、3間發生介在有發光管2 (介電質）的放電，藉由被封入在內部的氙氣的發光而得 波長172nm的放射。 若藉由氙的發光所形成的波長172nm的光的一部分被 照射在內部螢光體層5時，即被轉換成與構成其之螢光體 特性相對應的光，在螢光體的表面反覆反射，藉此由孔徑 部6放射。此外，其他波長172mm的光的一部分係由形成 在發光管2的孔徑部6透射該發光管2而直接入射至外部螢 光體層8，被轉換成與構成其之螢光體特性相對應的波長 範圍的光而被放射。結果，由螢光燈的外管7被放射出藉 由內部螢光體5所被轉換的光、及藉由外部螢光體層8所被 轉換的光等二者。 因此，若藉由相同的螢光體來構成內部螢光體層5與 外部螢光體層8時，係將該等合算而被輸出至外部。 在此，由於外部螢光體層8的厚度小於內部螢光體層5 的厚度，因此由形成在發光管2的孔徑部6所被放出的光的 量會變大，而形成按照兩螢光體層5、8的厚度差的指向性 〇 若列舉如上所示之螢光燈1之實施例，如下所示。 發光管2係由合成石英玻璃所構成，在該發光管2的內 表面形成內部螢光體層5之前，爲了改善該發光管與螢光 體的密接性，在發光管的內表面形成比合成石英玻璃爲更 •10- 201212092 低熔點的玻璃粉末層（未圖示）。關於該技術，詳細揭示 於曰本特開20 1 0-05 6007號公報等。 具體而言，將軟質玻璃的粉末與適當的黏結劑混合來 調製漿體，將該漿體塗佈在發光管的內表面，將孔徑部的 軟質玻璃粉末去除後，以約600t左右進行燒成。 之後，以構成內部螢光體層5的螢光體而言，使用 (Lai-x，Ndx)P04(其中，x = 0.01〜0.11)螢光體，將該螢光 體漿體進行塗佈乾燥，以5 00〜900°C燒成後，將孔徑部6 的螢光體去除，而形成內部螢光體層5。 接著，在發光管2的外表面上，將由銀（Ag)或銅（ Cu )與燒結玻璃所構成的膏材進行網版印刷，而形成一對 外部電極3、3。 在該電極3、3上，爲了保護該電極免於受到由透射發 光管2所被放射的紫外線影響，以保護膜4、4而言，形成 有將3102與B2〇3加以混練而成的硼矽酸玻璃之層。 之後，將發光管2進行燒成而將電極3、3及保護膜4、 4固接。其中，該保護膜4、4的熱膨脹係數爲30x1 0_7(1/ K )以下。 在外部電極3、3係以由發光管2的單側抽出的方式連 接外部引線Wl、W2，且將該引線Wl、W2與電源10相連接 〇 接著，在與孔徑部6的區域相對應的發光管2的外表面 上，將與前述內部螢光體層5爲相同種類的螢光體漿體藉 由網版印刷進行塗佈且燒成，而形成外部螢光體層8。 -11 - 201212092 在如此形成的發光管2的內部配置由Zr-Fe所構成的收 氣器（getter )，進行發光管內部的排氣而封入Xe氣體 13.3kPa ( lOOTorr )。 此外，外管7係使用與前述發光管2爲相同材質的合成 石英玻璃》 將構成外管7的直管狀合成石英玻璃管的單端在完成 密封的狀態下關閉，在其中揷入發光管2。 接著，形成爲可對外部電極3、3供電的狀態而在外管 7內部塡充N2氣體，且將開口部閉塞。 藉由施加ν〇_ρ = 1 700V的矩形波來使上述實施例之螢光 燈亮燈，藉由光譜輻射計（USHIO電機製，USR40 )來進 行分光光譜測定。以該螢光體的光譜特性而言，係在波長 184nm附近具備峰値者。 在第3圖中係顯示關於上述螢光燈1，作成使內部螢光 體層5與外部螢光體層8的厚度作各種變化的數種類的燈， 將其照度進行測定比較後的結果。 具體而言，針對使內部螢光體層5的厚度分別變化成 18、35、70μιη的各燈，外部使螢光體層8的厚度在0〜 25 μιη之間變化，來測定出來自該孔徑部6的照度。 此外，在第4圖中係顯示以構成前述螢光燈1中的內外 部螢光體層5、8的螢光體而言，將使用YP〇4 : Nd時的照 度進行測定比較後的結果。其中，關於螢光體以外的構成 係與上述實施例相同。 具體而言，針對使內部螢光體層5的厚度分別變化成 -12- 201212092 18、37、55、73μηι的各燈，使外部螢光體層8的厚度在0〜 28 μηι之間變化，來測定出來自該孔徑部6的照度。 在本發明之螢光燈中，外部螢光體層8係藉由透射發 光管2之孔徑部6的波長172nm的紫外光而被激發，放射所 發光的螢光。 因此，此時，由孔徑部6係同時出射藉由外部螢光體 層8所爲的光放射部分、及來自內部螢光體層5的光放射部 分，但是來自發光管2內部的內部螢光體層5的光放射係在 通過外部螢光體層8時，因吸收等變得無法放射一部分， 而會發生損失。亦即，藉由從來自內部螢光體層5的光放 射部分減掉因外部螢光體層8所造成的衰減部分而得的差 分、及來自該外部螢光體層8本身的光放射部分的合算， 來決定光放射輸出的強度。 如第3' 4圖所示，在本發明之形成有外部螢光體層8 的螢光燈中，無關於內部螢光體層5的厚度，相較於沒有 外部螢光體層8的情形，亦即相較於圖中的〇 μιη的情形，可 使其光輸出增大。 尤其，若將外部螢光體層8的厚度形成爲ΐ〇μιη以下， 更佳爲5μπι左右時，可使來自孔徑部6的光輸出增大。 其中，隨著內部螢光體層5的厚度增加，發光管2內部 的反射會變大’若其超過約50μιη時，來自孔徑部6的輸出 幾乎不會改變。亦即，藉由內部蛋光體層5所造成的反射 會達成飽和狀態。如上所示，內部螢光體層5較厚，其反 射功能處於飽和狀態時亦同樣地，若將外部螢光體層8形 -13- 201212092 成爲1 ΟμίΏ以下，更佳爲5μιη左右，則可使來自孔徑部6的 光輸出增大。 接著，前述外部螢光體層8係不會有在放電空間的外 部被曝露於放電的情形，因此螢光體不會劣化，而且’由 於被配置在惰性氣體空間內，因此不易發生螢光體更加劣 化，由孔徑部6係可得安定的光放射。 如以上說明所示，藉由本發明之螢光燈，在發光管的 圓周方向的一部分形成有未形成內部螢光體層的孔徑部而 成的螢光燈中，以覆蓋前述發光管的方式設置外管，在前 述發光管之與前述孔徑部相對應的外表面形成有外部螢光 體層，藉此相較於僅形成有孔徑部者，可使其光輸出增大 ，而且，外部螢光體層並未被曝露在放電空間，因此其具 有不易發生劣化，且經長時間可得安定的光輸出的效果。 【圖式簡單說明】 第1圖係本發明之螢光燈的軸向剖面圖。 第2圖係第1圖的A-Α放大橫剖面圖。 第3圖係表示本發明之外部螢光體層的厚度與相對強 度的曲線圖。 第4圖係使用其他螢光體時與第3圖相同的曲線圖。 【主要元件符號說明】 1 :螢光燈 2 :發光管 -14- 201212092 3 :電極 4 :保護膜 5 :內部螢光體層 6 :孔徑部 7 :外管 8 :外部螢光體層 1 〇 :電源201212092 VI. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to fluorescent lamps, and more particularly to fluorescent lamps that emit ultraviolet vacuum light. [Prior Art] Ultraviolet rays have been suitably used in photochemical reactions, sterilization, or decomposition of organic substances. In the case of the ultraviolet light source as shown above, most of the low-pressure mercury lamps are used, but a dielectric has also been proposed as disclosed in Japanese Laid-Open Patent Publication No. 2000-00 (Patent Document 1). Fluorescent lamp with a barrier discharge. In the fluorescent lamp described in Patent Document 1, a rare gas is sealed in the inside of the arc tube, and a dielectric discharge is generated between the pair of electrodes, thereby exciting a rare gas and emitting ultraviolet light (vacuum ultraviolet light) to excite the lamp. A phosphor is formed on the inner surface of the arc tube to obtain ultraviolet light in a predetermined wavelength region (vacuum ultraviolet region). Japanese Laid-Open Patent Publication No. 2010-153054 (Patent Document 2) discloses a fluorescent lamp including at least one external electrode on the outer side of an arc tube, which has directivity by providing an aperture portion. In the specific example, it is disclosed that the phosphor layer formed on the inner surface of the arc tube is formed in a portion where the phosphor layer is not formed in a part of the circumferential direction, and is formed into an aperture portion. Or, a part of the circumferential direction of the phosphor layer is made thinner than the other portions, and the thin-walled portion is formed as an aperture portion. -5- 201212092 However, in the above-mentioned fluorescent lamp, since the phosphor is exposed to the discharge space, deterioration easily occurs, and it is difficult to maintain the illuminance stability for a long time. In terms of the main cause of deterioration of the phosphor, it is considered to be due to impure gas (H20, co2, etc.), but especially when using dielectric barrier discharge, based on the discharge principle, the discharge is formed across the arc tube. In particular, there is a problem that the damage of the phosphor is large and the light stability is not easily obtained. [Prior Art Document] [Patent Document 1] [Patent Document 1] JP-A-2001-015078 (Patent Document 2) Japanese Unexamined Patent Application Publication No. JP-A No. No. Publication No. No. No. No. No. No. No. No. No. Nos. An arc tube in which a discharge gas containing xenon is sealed; a pair of electrodes formed in the longitudinal direction of the arc tube and facing through the dielectric; and an internal phosphor layer formed on the inner surface of the arc tube A fluorescent lamp in which the aperture portion of the internal phosphor layer is not formed is formed in a part of the circumferential direction of the arc tube, which avoids deterioration due to discharge of the phosphor layer and maintains light stability The ground is higher and the life of the fluorescent lamp is longer. 201212092 (Means for Solving the Problem) The present invention has been made in view of the above problems, and is characterized in that an outer tube is disposed so as to cover an arc tube, and the light-emitting tube is in contact with the aperture portion. An external phosphor layer is formed on the corresponding outer surface. Further, it is characterized in that an inert gas is filled between the arc tube and the outer tube. Further, it is characterized in that the thickness of the external phosphor layer is made smaller than the thickness of the internal phosphor. Further, at least one of the internal phosphor or the external phosphor layer contains either a LaP04: Nd phosphor or a YP04: Nd phosphor. (Effect of the Invention) According to the fluorescent lamp of the present invention, the external phosphor on the outer surface of the aperture portion of the arc tube can increase its light output as compared with a lamp in which only the aperture portion is formed, and The external phosphor layer is not exposed to discharge, and thus is less likely to deteriorate. Therefore, the light system emitted by the external phosphor layer in the fluorescent lamp can maintain the light stability high and can extend the life of the fluorescent lamp. Further, since the external phosphor layer is in an inert gas atmosphere, it is less likely to deteriorate. Further, by forming the external phosphor layer to be thinner than the internal phosphor layer, it is possible to efficiently illuminate the object 201212092 while providing the directivity of the fluorescent lamp. In the case of a phosphor layer, light having a wavelength of around 190 nm is emitted by any one of a LaP04: Nd phosphor or a ΥΡ04:Nd phosphor, and is suitable for use as a photochemical reaction, sterilization, or organic matter. Decompose the source of the _. [Embodiment] Fig. 1 is a cross-sectional view showing a fluorescent lamp of the present invention. In the figure, the fluorescent lamp 1 is provided with a pair of external electrodes 3 and 3 opposed to each other on the outer peripheral surface of the arc tube 2. The external electrodes 3 and 3 are formed in a strip shape extending in the axial direction of the tube, and are, for example, a silver paste obtained by mixing silver (Ag) and sintered glass, or a mixture of gold (Au) and sintered glass. A conductive film such as gold paste is formed. The external electrodes 3 and 3 are covered with protective films 4 and 4 made of a glass layer, and leads W 1 and W 2 are connected to the external electrodes 3 and 3, respectively, and are connected to a power source 10 that generates a high-frequency voltage. . The arc tube 2 is made of synthetic quartz glass having high transmittance to vacuum ultraviolet light having a wavelength of 200 mm or less. Further, in order to further improve the ultraviolet illuminance maintenance rate, it is preferable to use a synthetic quartz glass having a high OH group content, and for example, F3 10 made of Shin-Etsu quartz can be used. Next, a rare gas is sealed in the arc tube 2 as a discharge gas, and in the case of a rare gas, either a crucible or a mixed gas of rhodium and other rare gases may be used. As shown in detail in Fig. 2, an inner phosphor layer 5 is formed on the inner surface of the arc tube 2. -8 - 201212092 The inner camp layer 5 has a region in which the inner phosphor layer 5 is not formed in a part of the circumferential direction of the arc tube 2, and this portion forms the aperture portion 6. Among them, an ultraviolet reflecting film (not shown) may be formed between the arc tube 2 and the inner phosphor layer 5 in addition to the aperture portion 6. The outer tube 7 is disposed in a core shape so as to cover the outer periphery of the arc tube 2, and the space between the two is filled with an inert gas such as nitrogen (N2) or argon (Ar). The outer tube 7 is transmissive to light of a specific wavelength region that is converted by the phosphor. In the case of a phosphor, when a characteristic of light having a wavelength of 200 nm or less is used, synthetic quartz glass is preferably used as the material. Next, an external phosphor layer 8 is formed on the outer surface of the arc tube 2 corresponding to the aperture portion 6. The internal phosphor layer 5 and the external phosphor layer 8 are excited by a wavelength of 172 nm which is emitted by the light emission of xenon, and emit light in the wavelength range according to the characteristics. When light having a wavelength of 200 nm or less, for example, light of 190 nm is emitted, it is preferable to use a LaP04 phosphor activated with ammonium or YP〇4 activated with ruthenium. Among them, the LaP〇4 phosphor of the endowment is (Lai-x, Ndx) P04 (where x = 0.01~0.1 1 ), and the endowment activity? The 〇4 phosphor is specifically (丫1~心![)?04 (where?{{ 〇.〇1~0.11). Next, the thickness of the inner phosphor layer 5 is, for example, 10 to 70 μm, preferably 30 to 50 μm, and the thickness of the outer phosphor layer 8 is thinner than, for example, 5 to 1 μm. As described above, by making the thicknesses of the two phosphor layers 5, 8 different from -9 - 201212092, directivity according to the difference can be formed. In the above configuration, when a high-frequency high voltage is applied to the external electrodes 3 and 3 by the high-frequency power source 10, a discharge which is interposed between the external electrodes 3 and 3 via the light-emitting tube 2 (dielectric) is sealed. Radiation at a wavelength of 172 nm is obtained by the emission of xenon inside. When a part of light having a wavelength of 172 nm formed by luminescence of erbium is irradiated onto the internal phosphor layer 5, it is converted into light corresponding to the characteristics of the phosphor constituting the luminescence, and is reflected on the surface of the phosphor. Thereby, it is radiated by the aperture portion 6. Further, a part of the light having a wavelength of 172 mm is directly incident on the external phosphor layer 8 by the aperture portion 6 formed in the arc tube 2, and is converted into a wavelength corresponding to the characteristics of the phosphor constituting the same. The range of light is emitted. As a result, both the light converted by the internal phosphor 5 and the light converted by the external phosphor layer 8 are radiated from the outer tube 7 of the fluorescent lamp. Therefore, when the internal phosphor layer 5 and the external phosphor layer 8 are formed by the same phosphor, they are output to the outside. Here, since the thickness of the outer phosphor layer 8 is smaller than the thickness of the inner phosphor layer 5, the amount of light emitted from the aperture portion 6 formed in the arc tube 2 becomes large, and the two phosphor layers 5 are formed. The directivity of the difference in thickness of 8 is as follows, as an example of the fluorescent lamp 1 shown above. The arc tube 2 is made of synthetic quartz glass. Before the inner phosphor layer 5 is formed on the inner surface of the arc tube 2, in order to improve the adhesion between the arc tube and the phosphor, a synthetic quartz is formed on the inner surface of the arc tube. Glass is a •10-201212092 low melting glass powder layer (not shown). This technique is disclosed in detail in Japanese Patent Publication No. 20 1 0-05 6007 and the like. Specifically, the powder of the soft glass is mixed with a suitable binder to prepare a slurry, and the slurry is applied onto the inner surface of the arc tube, and the soft glass powder of the aperture portion is removed, and then fired at about 600 t. . Thereafter, the phosphor constituting the internal phosphor layer 5 is coated with a phosphor (Lai-x, Ndx) P04 (where x = 0.01 to 0.11), and the phosphor paste is coated and dried. After firing at 500 to 900 ° C, the phosphor of the aperture portion 6 is removed to form the internal phosphor layer 5 . Next, on the outer surface of the arc tube 2, a paste composed of silver (Ag) or copper (Cu) and sintered glass is screen-printed to form a pair of external electrodes 3, 3. In order to protect the electrode from the ultraviolet light emitted by the transmission light-emitting tube 2, the electrodes 3 and 3 are formed by mixing the 3102 and B2〇3 with the protective films 4 and 4. The layer of tannic acid glass. Thereafter, the arc tube 2 is fired to fix the electrodes 3 and 3 and the protective films 4 and 4. The thermal expansion coefficients of the protective films 4 and 4 are 30×10 −7 (1/K ) or less. The external leads 3, 3 are connected to the external leads W1, W2 so as to be drawn out from one side of the arc tube 2, and the leads W1, W2 are connected to the power source 10, and then, corresponding to the area of the aperture portion 6. On the outer surface of the arc tube 2, the same type of phosphor paste as the inner phosphor layer 5 is applied by screen printing and fired to form the outer phosphor layer 8. -11 - 201212092 A getter made of Zr-Fe is placed inside the arc tube 2 thus formed, and the inside of the arc tube is exhausted to enclose the Xe gas at 13.3 kPa (100 Torr). Further, the outer tube 7 is made of synthetic quartz glass of the same material as the arc tube 2 described above. The single end of the straight tubular synthetic quartz glass tube constituting the outer tube 7 is closed in a state where the sealing is completed, and the light-emitting tube 2 is inserted therein. . Then, in a state in which the external electrodes 3 and 3 can be supplied with power, the inside of the outer tube 7 is filled with N2 gas, and the opening is closed. The fluorescent lamp of the above embodiment was lit by applying a rectangular wave of ν 〇 ρ = 1 700 V, and spectroscopic measurement was carried out by a spectroradiometer (USHIO electromechanical mechanism, USR40). The spectral characteristics of the phosphor are those having a peak in the vicinity of a wavelength of 184 nm. In the third embodiment, a plurality of types of lamps in which the thicknesses of the internal phosphor layer 5 and the external phosphor layer 8 are variously changed are shown in the above-described fluorescent lamp 1, and the illuminance is measured and compared. Specifically, each of the lamps in which the thickness of the internal phosphor layer 5 is changed to 18, 35, and 70 μm, and the thickness of the phosphor layer 8 is changed from 0 to 25 μm outside, and the aperture portion 6 is measured. Illumination. Further, in Fig. 4, the results of measurement and comparison of the illuminance when YP〇4: Nd is used for the phosphor constituting the inner and outer phosphor layers 5 and 8 in the fluorescent lamp 1 are shown. Here, the configuration other than the phosphor is the same as that of the above embodiment. Specifically, for each of the lamps in which the thickness of the inner phosphor layer 5 is changed to -12 to 201212092 18, 37, 55, and 73 μm, the thickness of the outer phosphor layer 8 is changed between 0 and 28 μηι. The illuminance from the aperture portion 6 is obtained. In the fluorescent lamp of the present invention, the external phosphor layer 8 is excited by the ultraviolet light having a wavelength of 172 nm which is transmitted through the aperture portion 6 of the light-emitting tube 2, and emits the emitted fluorescent light. Therefore, at this time, the light-emitting portion by the external phosphor layer 8 and the light-emitting portion from the internal phosphor layer 5 are simultaneously emitted from the aperture portion 6, but the internal phosphor layer 5 from the inside of the arc tube 2 is emitted. When the external light emitter layer 8 passes through the external phosphor layer 8, a part of the light radiation layer cannot be radiated due to absorption or the like, and a loss occurs. That is, the difference obtained by subtracting the attenuation portion due to the external phosphor layer 8 from the light-emitting portion from the internal phosphor layer 5, and the light-emitting portion from the external phosphor layer 8 itself are calculated, To determine the intensity of the light emission output. As shown in Fig. 3'4, in the fluorescent lamp in which the external phosphor layer 8 of the present invention is formed, the thickness of the inner phosphor layer 5 is not related to the case where the outer phosphor layer 8 is not provided, that is, The light output can be increased compared to the case of 〇μιη in the figure. In particular, when the thickness of the external phosphor layer 8 is ΐ〇μηη or less, more preferably about 5 μm, the light output from the aperture portion 6 can be increased. Among them, as the thickness of the inner phosphor layer 5 increases, the reflection inside the arc tube 2 becomes larger. If it exceeds about 50 μm, the output from the aperture portion 6 hardly changes. That is, the reflection caused by the inner egg light layer 5 reaches a saturated state. As described above, when the internal phosphor layer 5 is thick and the reflection function is in a saturated state, if the external phosphor layer 8-13-201212092 is 1 ΟμίΏ or less, more preferably about 5 μm, it can be derived from The light output of the aperture portion 6 is increased. Then, the external phosphor layer 8 is not exposed to the discharge outside the discharge space, so that the phosphor does not deteriorate, and 'the phosphor is more likely to be generated because it is disposed in the inert gas space. Deterioration, stable light emission is obtained by the aperture portion 6. As described above, the fluorescent lamp of the present invention has a portion in the circumferential direction of the arc tube in which a hole portion in which the internal phosphor layer is not formed is formed, and is provided to cover the light-emitting tube. a tube having an outer phosphor layer formed on an outer surface of the arc tube corresponding to the aperture portion, whereby an optical output can be increased compared to the case where only the aperture portion is formed, and the external phosphor layer is Since it is not exposed to the discharge space, it has an effect that it is less likely to be deteriorated, and a stable light output can be obtained over a long period of time. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an axial sectional view of a fluorescent lamp of the present invention. Fig. 2 is an enlarged cross-sectional view taken along line A-Α of Fig. 1. Figure 3 is a graph showing the thickness and relative intensity of the outer phosphor layer of the present invention. Fig. 4 is a graph similar to Fig. 3 when other phosphors are used. [Main component symbol description] 1 : Fluorescent lamp 2 : Illuminated tube -14- 201212092 3 : Electrode 4 : Protective film 5 : Internal phosphor layer 6 : Aperture part 7 : Outer tube 8 : External phosphor layer 1 〇 : Power supply
Wl、W2 :引線 -15Wl, W2: lead -15