JPS59128755A - Low pressure mercury vapor discharge lamp for display device - Google Patents

Abstract

PURPOSE:To obtain emission of high luminance over a luminous surface and improve homogeneity in luminance distribution by making the length of the joint section of an electric discharge tube larger than the diameter of straight tubular sections and expanding along the luminous surface a projection located between the straight tubular bulbs and protruding toward a discharge path. CONSTITUTION:A discharge tube is made by fusing electrodes 4 and 4 to open ends of a pair of straight tubular sections 5 and 6 and connecting the other open ends with an almost semispherical joint section 7. The diameter (D) of the bottom area (8) of the joint section 7 is much larger than the diameter (d) of the straight tubular sections 5 and 6. The inner surface of the spherical area 11 of the joint section 7 is coated with a phosphor film 12 emitting red, green or blue monochromatic light. A semispherical projection 14 protruding toward a discharge path 10 is unifiedly provided in the center of the bottom area 8 of the joint section 7. The distance (l) between the projection 14 and a luminous surface 13 is smaller than the diameter (d) of the straight tubular sections 5 and 6.

Description

【発明の詳細な説明】 〔発明の技術分野〕 本発明は野球場や競技場に設置された表示スクリーンあ
るいは道路情報を示す表示装置において、その表示素子
として用いられる低圧水銀蒸気放電灯に関する。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a low-pressure mercury vapor discharge lamp used as a display element in a display screen installed at a baseball stadium or stadium or a display device showing road information.

〔発明の技術的背景とその問題点〕[Technical background of the invention and its problems]

最近、野球場や競技場等においては、テレビカメラやＶ
ＴＲに納められた画像を大型の表示スクリーン上に写し
出して表示するディスプレイ装置が設置されてｂる。こ
の装置は表示スクリーン上に数千ないし数万個の表示素
子を密に配置し、これら表示素子を画像信号に応じて選
択的に適宜点灯させることによル、上記表示スクリーン
上に所定の画像を表示するよう罠なっている。Recently, television cameras and video cameras are being used at baseball fields and stadiums.
A display device is installed that projects and displays images stored in the TR on a large display screen. This device displays a predetermined image on the display screen by densely arranging thousands to tens of thousands of display elements on the display screen and selectively lighting up these display elements according to image signals. It has become a trap to display.

ところで、この檜の表示素子としては、現在電子ビーム
により単色を発光させるものと、透光性塗料を塗布した
電球により単色を発光させるものが知られている。しか
しながら、上記電子ビームは消費電力が少なく長寿命で
ある等の利点を有するが、表示素子自体が高価なものと
なるためコスト高となる難点がある。また電球は発光素
子自体が安価で制御回路も簡単となる等の利点はあるが
、反面消費電力が大きくかつ寿命が短い等の欠点を有し
ている。Incidentally, currently known display elements made of Japanese cypress include those that emit a single color using an electron beam and those that emit a single color using a light bulb coated with translucent paint. However, although the electron beam has advantages such as low power consumption and long life, it has the disadvantage that the display element itself is expensive, resulting in high cost. Although light bulbs have the advantage that the light emitting element itself is inexpensive and the control circuit is simple, they also have disadvantages such as high power consumption and short lifespan.

そこで、他の表示素子としてけい光ランプに代表される
低圧水銀蒸気放電灯の使用が考えられる。けｈ光ランプ
は消費電力が少なく長寿命で、しかも輝度が高くコスト
も比較的安価であることは周知の通シであシ、この点か
ら見れば表示素子として必要な点を充分に満たしている
と言える。しかしながら、けい光ランプの発光管は電球
等に比べて細いので、上述の如きディスプレイ装置の表
示素子として利用することを考慮すると、発光面積が充
分に得られず、いまだ実用化されていなかった。Therefore, it is conceivable to use a low-pressure mercury vapor discharge lamp, typified by a fluorescent lamp, as another display element. It is well known that fluorescent lamps consume less power, have a long life, have high brightness, and are relatively inexpensive.From this point of view, they fully meet the requirements of display elements. I can say that there is. However, since the arc tube of a fluorescent lamp is thinner than that of a light bulb or the like, when considering its use as a display element in the above-mentioned display device, a sufficient light emitting area cannot be obtained, and it has not yet been put into practical use.

〔発明の目的〕[Purpose of the invention]

本発明はこのような事情にもとづいてなされたもので、
発光面積を充分に確保でき、しかも発光面の輝度が向上
するとともに、輝度分布の均一化を図れ、上述の如き表
示装置の表示素子として何ら問題なく使用できる低圧水
銀蒸気放電灯の提供を目的とする。The present invention was made based on these circumstances, and
The object of the present invention is to provide a low-pressure mercury vapor discharge lamp that can secure a sufficient light-emitting area, improve the brightness of the light-emitting surface, and make the brightness distribution uniform, and can be used as a display element of the above-mentioned display device without any problems. do.

〔発明の概要〕[Summary of the invention]

すなわち、本発明は上記目的を達成するため、放電管の
連結部を、その放電路と交差する方向の長さを直管部の
径よシ大きく形成するとともに、この連結部における直
管部が連結された面にはこれら直管部間に位置して放電
路側に向って突出する突部を形成し、との突部によう連
結部内を通る陽光柱を偏平に押し広げるとともに、発光
面に近づけるよりにしたことを特徴とする。That is, in order to achieve the above-mentioned object, the present invention forms the connecting portion of the discharge tube so that the length in the direction intersecting the discharge path is larger than the diameter of the straight tube portion, and the straight tube portion of the connecting portion is A protrusion is formed on the connected surface that is located between these straight pipe parts and protrudes toward the discharge path side. It is characterized by being made closer to each other.

〔発明の実施例〕[Embodiments of the invention]

以下本発明を第１図ないし第９図に示す第１実施例にも
とづいて説明する。The present invention will be explained below based on a first embodiment shown in FIGS. 1 to 9.

第１図は、例えば野球場や競技場等の一角に設置される
大型な表示スクリーンの概略を示し、略矩形状をなした
スクリーンゲート１上には数子ないし数万個の表示素子
２・・・が密に配置されている。これら表示素子２・・
・はけい光ランノに代表されている低圧水銀蒸気放電灯
であシ、この構造については第２図以降に詳図されて込
る。FIG. 1 schematically shows a large display screen installed in a corner of a baseball field or stadium, for example. On a screen gate 1 having a substantially rectangular shape, there are several to tens of thousands of display elements 2...・are densely arranged. These display elements 2...
・The lamp is a low-pressure mercury vapor discharge lamp, such as the fluorescent lamp, and its structure is shown in detail in Figures 2 onwards.

すなわち３はその放電管であシ、ガラス等の透光性材料
によって構成されている。放電管３は一端開口部に従来
公知の電極４．４が封着された１対の直管部５．６と、
これら直管部５．６０他端開ロ部を連結する略牛球状を
なした連結部２とから構成される。連結部７の底部８は
略平坦な円形をなし、その直径りは直管部５．６の径ｄ
よシも格段に大きく形成されている。この底部８には径
方向に離間した２個所に連結部７内外を連通させる通孔
９．９が開設され、これら通孔９　、９１１？：直管部
５，６の他端開口部が突き合わされて気密にプラス接合
されてｈる。That is, the discharge tube 3 is made of a translucent material such as glass. The discharge tube 3 has a pair of straight tube portions 5.6, each of which has a conventionally known electrode 4.4 sealed to its opening at one end.
It is composed of a connecting portion 2 having an approximately cow-ball shape that connects these straight pipe portions 5 and 60 with the open end portion at the other end. The bottom part 8 of the connecting part 7 has a substantially flat circular shape, and its diameter is equal to the diameter d of the straight pipe part 5.6.
The edges are also significantly larger. This bottom portion 8 is provided with through holes 9.9 at two locations spaced apart in the radial direction for communicating the inside and outside of the connecting portion 7, and these through holes 9, 911? : The other end openings of the straight pipe parts 5 and 6 are butted against each other and are airtightly joined together.

この接合によシ連結部７の底部から１対の直管部５．６
が軸方向に並行に導出された形状の放電管３が構成され
るとともに、電極４．４間に略Ｕ字状をなした放電路１
０が連続して形成され、この放電路１０上を陽光柱１５
が通るよう５− になっている。そして連結部２０球面部１ノの内面１つ
まシ上記底部８と対向された面には、赤、緑、青のいず
れかの単色光を発するけい光体被膜１２が被着されてｈ
るとともに、外面には色度補正のための図示しない透光
性被膜が被着されている。したがってこの連結部７の球
面部１１が表示部としての発光面１３′ｆ、なしておシ
、この発光面１３の背面でかつその外周よりも内側に直
管部５，６が位置されている。なお、放電管１０内には
所定量の水銀とアルゴン等の封入希ガスが所定の圧力で
封入されてｈる。そして各放電管１０・・・は夫々図示
しない点灯回路に接続されておシ、これら点灯回路をマ
イクロコンピュータ等の画像制御部で制御することによ
ｐ％画像信号に応じて発光すべき放ＩＥ管１０・・・の
数および位置が変化し、種々な画像がスクリーンゲート
１上に表示されるよう釦なっている。Through this joining, a pair of straight pipe parts 5.6 are connected from the bottom of the connecting part 7.
A discharge tube 3 is formed in which the electrodes are led out parallel to the axial direction, and a discharge path 1 is formed in a substantially U-shape between the electrodes 4 and 4.
0 are formed continuously, and a positive column 15 is formed on this discharge path 10.
It is set to 5- so that it passes. One inner surface of the spherical portion 1 of the connecting portion 20, which faces the bottom portion 8, is coated with a phosphor coating 12 that emits monochromatic light of red, green, or blue.
At the same time, a transparent coating (not shown) is coated on the outer surface for chromaticity correction. Therefore, the spherical part 11 of this connecting part 7 serves as a light emitting surface 13'f as a display part, and the straight pipe parts 5 and 6 are located on the back side of this light emitting surface 13 and inside its outer periphery. . Note that a predetermined amount of mercury and a rare gas such as argon are sealed in the discharge tube 10 at a predetermined pressure. Each discharge tube 10 is connected to a lighting circuit (not shown), and by controlling these lighting circuits with an image control unit such as a microcomputer, the discharge IE to be emitted according to the p% image signal is controlled. The number and position of the tubes 10 change, and buttons are used to display various images on the screen gate 1.

また、上述の如き放電管１０においては、その発光面１
３の最大径つまシ上記連結部７の底６− 部８の直径りは、５０＋ｕ＋以下に抑えることが望まし
い。すなわち、単一の放電管１ｏを上記スクリーンポー
ドＩＫ取シ付けて点灯した場合、発光面１３の最大径Ｄ
　（ｖ＋ｍ）とこの発光面１３の形状を判別可能な視認
距離ｍとは第７図に示したような関係にある。また多数
個の放電管１゜・・・をスクリーンが一ド１上に＠に並
べ、画像制御部に画像信号を与えて必要な個所の放電管
１０・・・を点灯させてスクリーンが一ド１上に画像を
表示した場合、個々の発光面１３・・・の最大径Ｄ（ａ
ｌ）と画像の視認可能な距離ｍとはＷＪＢ図に示したよ
うな関係にある。そして、一般的な野球場や競技場の広
さのことを考えると、発光面１３の視認距離は最大でも
１５０ｍ程度となるから、上記両図からも明らかなよう
に発光面１３・・・の径りは最大でも５０１ＩＩ１１あ
れば充分であることが分る。In addition, in the discharge tube 10 as described above, the light emitting surface 1
It is desirable that the diameter of the bottom 6-8 of the connecting portion 7 is kept to 50+u+ or less. That is, when a single discharge tube 1o is attached to the screen pod IK and lit, the maximum diameter D of the light emitting surface 13 is
(v+m) and the visible distance m at which the shape of the light emitting surface 13 can be determined have a relationship as shown in FIG. In addition, a large number of discharge tubes 1゜... are lined up in one screen on one screen, and an image signal is given to the image control unit to light up the discharge tubes 10... in the necessary locations. 1, the maximum diameter D(a
l) and the visible distance m of the image have a relationship as shown in the WJB diagram. Considering the size of a typical baseball field or stadium, the visible distance of the light emitting surface 13 is about 150 m at most, so as is clear from the above figures, the light emitting surface 13... It can be seen that a maximum diameter of 501II11 is sufficient.

ところで、上記連結部７の底部８中夫には、放電路１０
側に向って突出する半球状の突部１４が一体に設けられ
ておシ、この突部１４は丁度直管部５．６間に位置され
ている。そして突部１４は連結部７内の放電空間内に入
）込んで発光面１３に対して同軸的に位置されてお）、
との突部１４と発光面１３との間の距離ｔは直管部５．
６の径ｄよ〕も小さく形成されている。By the way, a discharge path 10 is provided at the bottom 8 of the connecting portion 7.
A hemispherical protrusion 14 protruding toward the side is integrally provided, and this protrusion 14 is located exactly between the straight pipe parts 5, 6. The protrusion 14 enters the discharge space in the connecting part 7 and is positioned coaxially with the light emitting surface 13),
The distance t between the protrusion 14 and the light emitting surface 13 is the straight pipe part 5.
The diameter d of 6] is also smaller than that of the diameter d of 6.

したがって、放電路１０は直管部５．６内にあってはそ
の通路断面が円形であるが、連結部７内ではその形状に
対応して放電空間が急激に広がるとともに、通路断面が
偏平な略円弧状に変化されている。Therefore, although the discharge path 10 has a circular cross section in the straight tube section 5.6, the discharge space in the connecting section 7 rapidly expands corresponding to the shape, and the cross section of the path is flat. It has been changed into a roughly arc shape.

このような構成によれば、電極４．４間に放電が生じる
と、Ｕ字状の放電路１０を陽光柱１５が通過し、この陽
光柱から放出された紫外線は連結部？内を通過する過程
で球面部１１内面のけい光体被膜１２に入射してけｈ光
体を励起し、このため発光面１３全面から可視光線が放
射される。この場合、連結部ｉ内では放電路１０が急激
に広がるとともに、突部１４を設けたことにより、通路
断面が偏平状に変化されているから、この連結部７内で
の陽光柱１５は第６図に示したように偏平状に押し潰さ
れて球面部１１に沿って広げられた状態となる。したが
って紫外線強度が最も高匹陽光柱１５の中心部がけい光
体被膜１２に近接してけい光体の励起が活発に行なわれ
、発光面１３全面に亘って輝度の高い発光が得られると
ともに、この発光面１３上の輝度分布の均一性が向上す
る。よって従来の電子ビームや電球と同様に表示素子と
して利用できる。According to such a configuration, when a discharge occurs between the electrodes 4, 4, the positive column 15 passes through the U-shaped discharge path 10, and the ultraviolet rays emitted from this positive column are transmitted to the connecting portion. In the process of passing through the interior, the light enters the phosphor coating 12 on the inner surface of the spherical portion 11 and excites the phosphor, so that visible light is emitted from the entire surface of the light emitting surface 13. In this case, the discharge path 10 widens rapidly in the connecting portion i, and the cross section of the passage is changed to a flat shape by providing the protrusion 14, so that the positive column 15 in the connecting portion 7 is As shown in FIG. 6, it is crushed into a flat shape and expanded along the spherical portion 11. Therefore, the center of the solar column 15 where the ultraviolet light intensity is highest is close to the phosphor coating 12, and the phosphor is actively excited, and high luminance is obtained over the entire surface of the light emitting surface 13. The uniformity of the luminance distribution on the light emitting surface 13 is improved. Therefore, it can be used as a display element in the same way as conventional electron beams and light bulbs.

なお、本発明者らは連結部７の底部８に突部１４を設け
た放電管３と底部８が略平坦な放電管３を点灯させ、夫
々の発光面１３．１３における放電路１０と直交する方
向の発光強度を調べたところ、第９図に示される如き結
果を得た。In addition, the present inventors lit a discharge tube 3 in which a protrusion 14 was provided on the bottom 8 of the connecting portion 7 and a discharge tube 3 in which the bottom 8 was substantially flat, and the discharge tube 10 was perpendicular to the discharge path 10 on the respective light emitting surfaces 13 and 13. When the luminescence intensity in the direction of 100 nm was investigated, the results shown in FIG. 9 were obtained.

この第９図中特性曲線Ａは突部１４を有する放電管３の
発光強度を、同じくＢは底部８が平坦な放電管３０発光
強度を示している。この第９図から明らかなように、放
電管３の方では発光面１３中夫の発光強度が高く、この
中央から遠ざかるに従って発光強度が低下しておシ、発
光＝９− 面１３上の輝度むらが比較的大きｈことが分る。In FIG. 9, characteristic curve A indicates the luminous intensity of the discharge tube 3 having the protrusion 14, and characteristic curve B indicates the luminous intensity of the discharge tube 30 having the flat bottom portion 8. As is clear from FIG. 9, in the discharge tube 3, the light emission intensity at the center of the light emitting surface 13 is high, and the light emission intensity decreases as the distance from this center increases. It can be seen that the unevenness is relatively large.

これに対し、本発明に係る放電管３によると、発光面１
３上の広い範囲に亘って発光強度が一定に保たれ、しか
も発光面１３全面に亘って発光強度の向上が認められる
。このことは陽光柱１５が偏平に押し潰されて球面部１
１に沿って広げられていることを意味し、突部“１４の
効果が充分圧発輝されていることが分る。On the other hand, according to the discharge tube 3 according to the present invention, the light emitting surface 1
The light emission intensity is kept constant over a wide range on the light emitting surface 13, and an improvement in the light emission intensity is observed over the entire light emitting surface 13. This means that the positive column 15 is flattened and the spherical part 1
It can be seen that the effect of the protrusion "14" is sufficiently brightened.

またこの構成によれば、放電路１０の途中の陽光柱１５
が部分的に広がる形となっても、ラング電流、電圧等は
ほとんど変わらず、したがって、放電管３の電気特性に
はほとんど影響がない・ さらに直管部５．６は発光面１３の背面でかつその外周
よシも内側に位置されているから、これら直管部５，６
は発光面１３の方向つｔｂ表示方向から見た場合、発光
面１３によって覆い隠され、したがって多数の放電管２
をその発光面１３を同一方向に向けて並べる場合に、放
電管２をスクリーンは−ド１上に密に並べると１０− とができる。Further, according to this configuration, the positive pillar 15 in the middle of the discharge path 10
Even if it partially expands, the rung current, voltage, etc. will hardly change, so it will have almost no effect on the electrical characteristics of the discharge tube 3.Furthermore, the straight tube section 5.6 is on the back side of the light emitting surface 13. Moreover, since the outer circumference is also located inside, these straight pipe parts 5 and 6
is covered by the light emitting surface 13 when viewed from the direction of the light emitting surface 13 and the tb display direction, and therefore a large number of discharge tubes 2
When the discharge tubes 2 are arranged with their light-emitting surfaces 13 facing in the same direction, and the discharge tubes 2 are closely arranged on the screen 1, a screen 10 can be obtained.

なお、本発明は上述した第１実施例に制約されるもので
はなく、第１０図ないし第１３図に本発明の第２実施例
を示す。この第２実施例は上記連結部７の底部８中夫に
、放電路１０と直交する方向に沿う細長状の突部２１を
設けたもので、との突部２ノは球面部１１１１Ｃ沿うよ
うな曲率の曲面に形成されている。したがって、連結部
１を通過する陽光柱１５は、第１３図に示したように略
三日月状に押し潰されて球面部１１に沿って広げられた
状態となシ、よって放電が広がるので上述した第１実施
例と同様の効果が得られる。Note that the present invention is not limited to the first embodiment described above, and a second embodiment of the present invention is shown in FIGS. 10 to 13. In this second embodiment, an elongated protrusion 21 is provided on the bottom 8 of the connecting portion 7 in a direction perpendicular to the discharge path 10, and the protrusion 21 is arranged along the spherical portion 1111C. It is formed into a curved surface with a certain curvature. Therefore, the positive column 15 passing through the connecting part 1 is crushed into a substantially crescent shape and spread out along the spherical part 11 as shown in FIG. 13, and the discharge spreads as described above. The same effects as in the first embodiment can be obtained.

また上述した各実施例では突部を底部に対して一体に設
は九が、例えば底部内面に別体の部材を設け、この部材
を突部として用いて陽光柱を偏平に押し広げるようにし
ても良い。Furthermore, in each of the above-mentioned embodiments, the protrusion is provided integrally with the bottom, but for example, a separate member is provided on the inner surface of the bottom, and this member is used as the protrusion to flatten and spread the solar column. Also good.

〔発明の効果〕〔Effect of the invention〕

以上詳述した本発明によれば、放電管の連結部を、その
放電路と交差する方向の長さｔ−直管部の径よ）も大き
く形成するとともに、この連結部における発光面と対向
された面には、直管部間に位置して放電路側に突出する
突部を形成し、この突部によ多連結部内を通る陽光柱を
偏平に押し潰して発光面に沿うように押し広げたから、
発光面全面に亘って輝度の高い発光が得られるとともに
、この発光面上の輝度分布の均一性が向上し、したがっ
て、表示素子用としてこれまでの電子ビームや電球と同
様に利用できる。また直管部は発光面の背後内側に隠れ
ているので、多数の放電管の発光面を同一方向に向けて
並べる場合に直管部が邪魔とならず、これら放電管を密
に並べることができる利点がある。According to the present invention described in detail above, the connecting portion of the discharge tube is formed to have a large length in the direction intersecting the discharge path (t - diameter of the straight tube portion), and the connecting portion is formed so as to be opposite to the light emitting surface of the connecting portion. A protrusion located between the straight pipe parts and protruding toward the discharge path side is formed on the surface where the light is emitted, and this protrusion flattens the solar column passing through the multi-connection part and pushes it along the light emitting surface. Because I spread it out,
High-brightness light emission can be obtained over the entire surface of the light-emitting surface, and the uniformity of the brightness distribution on the light-emitting surface is improved, so that it can be used for display devices in the same way as conventional electron beams and light bulbs. In addition, since the straight tube part is hidden behind the light emitting surface, the straight tube part does not get in the way when many discharge tubes are lined up with their light emitting surfaces facing the same direction, and these discharge tubes can be lined up closely. There are advantages that can be achieved.

【図面の簡単な説明】[Brief explanation of drawings]

第１図ないし第９図は本発明の第１実施例を示し、第１
図は表示スクリーンの概略構成図、第２図は放電管の斜
視図、第３図は底面図、第４図は側面図、第５図は第３
図中ｖ−ｖａｔに沿う断面図、第６図は第３図中■−■
線に沿う断面図、第７図および第８図は発光面の直径と
視認距離との関係を示す特性図、第９図は発光面上の発
光強度を示す特性図、Ｍ２Ｏ図ないし第１３図は本発明
の第２実施例を示し、第１０図は放電管の斜視図、第１
１図は底面図、第１２図は第１１図中ＸＩ−ＸＩ線に沿
う断面図、第１３図は第１１図中■−■線に沿う断面図
である。 ３・・・放電管、４・・・電極、５．６・・・直管部、
２・・・連結部、１２・・・けい光体被膜、１３・・・
発光面、１４、Ｊ！１・・・突部。 出願人代理人　　弁理土鈴　江　武　彦１３−1 to 9 show a first embodiment of the present invention.
The figure is a schematic configuration diagram of the display screen, Figure 2 is a perspective view of the discharge tube, Figure 3 is a bottom view, Figure 4 is a side view, and Figure 5 is the third
A sectional view along v-vat in the figure, Figure 6 is ■-■ in Figure 3
7 and 8 are characteristic diagrams showing the relationship between the diameter of the light emitting surface and the visible distance. FIG. 9 is a characteristic diagram showing the luminous intensity on the light emitting surface, and M2O diagrams to 13 10 shows a second embodiment of the present invention, and FIG. 10 is a perspective view of the discharge tube, and FIG.
1 is a bottom view, FIG. 12 is a cross-sectional view taken along the line XI--XI in FIG. 11, and FIG. 13 is a cross-sectional view taken along the line ■--■ in FIG. 3... Discharge tube, 4... Electrode, 5.6... Straight tube section,
2... Connecting portion, 12... Fluorescent coating, 13...
Luminous surface, 14, J! 1... Protrusion. Applicant's attorney Takehiko E, 13-

Claims (1)

【特許請求の範囲】[Claims] 一端に電極が封着され、かつ他端が開口された１対の直
管部と、これら直管部の他端部間を気密に連結して上記
電極間に略Ｕ字状の放電路を形成する連結部とで構成さ
れた光透過性の放電管を備え、この放電管の連結部はそ
の放電路と交差する方向の長さを上記直管部の径よシも
大きく形成し、この連結部の背面内側に上記１対の直管
部が位置するとともに１この放電管のうち少なくとも連
結部における直管部と対向された面にけい光体被膜を被
着して発光面とし、かつこの連結部における直管部が連
結された面にはこれら直管部間に位置して放電路側に向
って突出する突部を設は之ことを特徴とする表示素子用
低圧水銀蒸気放電灯。A pair of straight pipe parts each having an electrode sealed at one end and open at the other end, and the other ends of these straight pipe parts are airtightly connected to form a substantially U-shaped discharge path between the electrodes. The connecting portion of the discharge tube has a length in the direction intersecting the discharge path that is larger than the diameter of the straight tube portion, and The pair of straight tube portions are located inside the back surface of the connecting portion, and a phosphor coating is applied to at least the surface of the discharge tube facing the straight tube portion of the connecting portion to serve as a light emitting surface, and A low-pressure mercury vapor discharge lamp for a display device, characterized in that a surface of the connecting portion where the straight tube portions are connected is provided with a protrusion located between the straight tube portions and protruding toward the discharge path side.