JP2858803B2 - Low pressure discharge lamp - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure discharge lamp, and more particularly to a small-diameter low-pressure discharge lamp such as a fluorescent lamp for a backlight. [Prior Art] Hot cathode discharge lamps and cold cathode discharge lamps are described on pages 759 to 760 of the Illuminating Engineering Handbook (May 1978, Ohmsha) edited by the Illuminating Engineering Institute of Japan. A hot cathode fluorescent lamp is described on page 160 of the same document. The structure of the hot cathode is described on page 121 of the Writing Handbook (November 1987, Ohmsha) edited by the Illuminating Engineering Institute of Japan. [Problems to be Solved by the Invention] In the above-mentioned conventional hot-cathode low-pressure discharge lamp, in order to heat the electrodes by energization, two lead wires connected to both ends of one electrode are required, There is a drawback that the structure of the discharge tube becomes complicated. In particular, when the size of the discharge vessel is small, the above disadvantage is fatal. Further, the cold cathode type low-pressure discharge lamp has one lead wire per electrode, but has a disadvantage that the cathode drop voltage is high and the efficiency is low. Further, when the discharge current is 10 mA or more, the life is short. An object of the present invention is to provide a simple structure at the end of the tube, with high efficiency,
An object of the present invention is to provide a low-pressure discharge lamp having a long life. [Means for Solving the Problems] The above-mentioned object is to provide a so-called refrigerant electrode characterized in that at least two pellets obtained by mounting a mercury alloy in a recess of a metal plate are installed so that the recesses face each other. Achieved by: Furthermore, the distance d between the pellets is 0.
By setting the distance between 2 mm and 1.0 mm, higher efficiency and longer life can be obtained, and even longer life can be achieved by applying a substance having an emissivity of 0.5 or more to at least a part of the outer surface of the pellet. , The above-mentioned transmission is further achieved. [Operation] At least two pellets formed by mounting a mercury alloy in a recess of a metal plate and a pair of electrodes characterized by a structure in which the recesses are opposed to each other are provided, and a glow is formed between the recesses of the pellet. Since the cathode drop voltage is reduced due to the so-called hollow cathode effect and the cathode loss is reduced, a highly efficient low-pressure discharge lamp can be obtained. If the distance d between the pellets is less than 0.2 mm, the voltage drop in the gap becomes large and the efficiency decreases.If the distance d exceeds 1.0 mm, the metal that forms an alloy with mercury is scattered by sputtering. Penetrates through the gap between the pellets and adheres to the tube wall of the lamp to form an alloy with mercury again, so that the mercury does not evaporate and the life is extended. That is, by setting the distance d between the pellets between 0.2 mm and 1.0 mm, higher efficiency and longer life can be obtained. Further, when the emissivity of at least a part of the outer surface of the metal plate forming the pellet is set to 0.5 or more, heat radiation from the metal plate increases, the temperature of the metal plate decreases, and a cathode drop exists. Since the density of the rare gas between the pellets increases, and the electrode material scattered from the cathode is pushed back to the cathode, the wear of the cathode is reduced and a long-life electrode is obtained. Also, when a getter containing zirconium is mixed with the mercury alloy, the work function of zirconium is relatively small, and zirconium absorbs impurity gas, so that high efficiency and long life can be obtained. The above effect is further enhanced by setting the main component of the discharge gas to a rare gas and setting the rare gas pressure expressed in Torr to 280 / M or more and 2000 / M or less when the atomic weight of the rare gas is M. Achieved. Embodiment FIG. 1 shows a first embodiment of the present invention. Cathodes 1 and 2 are sealed at both ends of a straight discharge vessel 4 having a fluorescent film 3 provided on the inner surface thereof, and the cathodes 1 and 2 are connected to one lead wire 5 and 6, respectively. Since there is only one lead wire, the structure of the tube end of the discharge tube is simplified, and there is an advantage that the manufacture is simple. The advantage that the structure of the tube end is simple is great when the inner diameter of the discharge tube is 8 mm or less. FIGS. 2 and 3 show a vertical sectional view of the electrode used in the embodiment of FIG. 1 and a front view of a pellet containing a mercury alloy, respectively. A mercury alloy Ti ₃ Hg 13 is held in a recess 12 provided in a metal plate 11 made of an iron-nickel alloy having a width of 3 mm. The electrode is formed such that the joint portion 14 of the two pellets holding the mercury alloy is bent so that the depressions holding the mercury alloy face each other. Distance d between pellets
Is defined by the distance d between the surfaces of the metal plates 11 and 11 ', and is maintained at 0.5 mm in this embodiment. Further, graphite 15, 15 'having an emissivity of 0.8 is applied to the outside of the metal plates 11, 11'. The phosphor 3 is applied to at least a part of the inner surface of the discharge tube 1. If the phosphor coating film 3 is present, the electrode
When the electrodes 1 and 2 are inserted, the electrodes 1 and 2 come into contact with the phosphor film 3 and the phosphor drops off, or the tube ends are more likely to be blackened. Therefore, one lead wire is provided for each electrode. Is particularly advantageous. In FIG. 1, a discharge tube 4 is a soda glass tube having an inner diameter of 5.7 mm and a length of 270 mm, and a rare earth phosphor Y ₂ O ₃ : Eu, MgAl ₁₁ O ₁₉ : Ce, Tb, 3Sr ₃ as a phosphor 3 on the inner surface. PO ₄ ) A mixture of ₂ · CaCl ₂ was applied. The discharge gas is 10 Torr of argon and mercury vapor. Mercury was generated by heating the pellets to 900 ° C. by high frequency heating. When the above-described low-pressure discharge lamp of the present invention was turned on with a discharge current of 30 kHz and 20 mA, the cathode drop voltage was reduced by 20% from the case where d was 0.1 mm, and a high-efficiency fluorescent lamp was obtained. In addition, the metal that forms an alloy with mercury is scattered by sputtering, but since the clearance between the pellets is small, the amount of the metal coming out is small, the amount of adhesion to the tube wall is small, and the pellets are formed. Since the emissivity of the outer surface of the metal plate is set to 0.8, the heat radiation from the metal plate increases, the temperature of the metal plate decreases, and the density of the rare gas between the pellets in which the cathode drop exists increases, Therefore, since the electrode material scattered from the cathode is pushed back to the cathode, wear of the cathode is reduced, and a long-life fluorescent lamp is obtained from the above two effects. In the second embodiment, as shown in FIG. 4, the distance d between the two pellets in the electrode of the first embodiment is substantially 0 m.
m, and the two pellets are displaced to face each other and discharge is performed through the opening 20. Further, the mercury alloys 13,1
3 'is mixed with a getter made of zirconium and aluminum. Moreover, in which the 'powder 21, 21 of the outer surface to cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2)' metal plates 11 and 11 was applied to the water glass binder. While the emissivity of a normal iron-nickel alloy at a wavelength of several μm to several tens of μm is 0.3 or less, cordierite 21,2
Since the emissivity of 1 'is about 0.8, heat radiation is large,
The temperature of the metal plate dropped, and the electrode had a longer life. Also,
Since cordierite and water glass are electrical insulators, the glow surely entered between the two depressions at the time of starting discharge, and a stable discharge was obtained. Since the getter containing zirconium was mixed with the mercury alloy, the work function of zirconium was relatively small, and high efficiency and long life were obtained because zirconium absorbed the impurity gas. Furthermore, this embodiment has the advantage that the manufacture of the lamp is simplified, since it is not necessary to adjust the distance between the pellets. According to the present invention, a low-pressure discharge lamp having a long life and high efficiency can be obtained. Further, a low-pressure discharge lamp having a simple tube end structure can be obtained, and there is an advantage that the manufacturing method is simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIGS.
FIG. 3 is a longitudinal sectional view of an electrode according to an embodiment of the present invention, and FIG. 3 is a front view of a pellet holding a mercury alloy. 1,2 ... Electrode, 11,11 '... Metal plate, 13,13' ... Mercury alloy, 15 ... Graphite, 21 ... Cordite, 20 ... Opening.

Continuation of the front page (72) Inventor Soichiro Ogawa 888 Fujibashi, Ome-shi, Tokyo Inside the Ome Plant of Hitachi Ltd. (56) References JP-A-62-226555 (JP, A) JP-A-53-26484 (JP) , A) (58) Fields surveyed (Int. Cl. ⁶ , DB name) H01J 61/24 H01J 61/067

Claims (6)

(57) [Claims] 1. A low-pressure discharge lamp comprising an electrode in which at least two pellets each having a mercury alloy mounted in a recess of a metal plate are installed so that the recesses face each other. 2. The low-pressure discharge lamp according to claim 1, wherein a getter material containing at least zirconium is mixed with said mercury alloy. 3. The distance d between the pellets is from 0.2 mm to 1.0 mm.
3. The low-pressure discharge lamp according to claim 1, wherein the low-pressure discharge lamp is located between the discharge lamps. 4. The method according to claim 1, wherein said two pellets are opposed to each other by shifting said recesses.
The low-pressure discharge lamp according to any one of the paragraphs. 5. When the main component of the discharge gas is a rare gas and the atomic weight of the rare gas is M, the pressure of the rare gas expressed in Torr is 28.
The low-pressure discharge lamp according to any one of claims 1 to 4, wherein the discharge pressure is not less than 0 / M and not more than 2000 / M. 6. A method according to claim 1, wherein a substance having an emissivity of 0.5 or more is applied to at least a part of the outer surface of said metal plate. 2. The low-pressure discharge lamp according to 1.