JPH0359942A - Low pressure discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a low-pressure discharge lamp, and particularly to a low-pressure discharge lamp that has a small diameter and operates with a small discharge current, such as a fluorescent lamp for a liquid crystal backlight.

[Conventional technology]

Hot cathode discharge lamps and cold cathode discharge lamps are described on pages 759 to 760 of the Illumination Handbook (May 1978, Ohmsha) edited by the Illuminating Engineering Society of Japan. Further, hot cathode type fluorescent lamps are described on page 160 of the same document. Regarding the structure of the hot cathode, please refer to the Illuminating Engineering Society's Lighting Handbook (1933).
It is described on page 121 of Ohmsha, November 2013.

[Problem to be solved by the invention]

In the above-mentioned conventional hot cathode type low pressure discharge lamp, the lamp is often used in a fixed position. but,
Low-pressure discharge lamps for backlights are portable, and have the disadvantage that electron-emitting substances on the electrodes fall off due to vibrations during movement, shortening the life of the lamp. In particular, when the size of the discharge vessel is small, the size of the electrode cannot be increased, and therefore the amount of electron emitting material retained cannot be increased, so the above-mentioned drawback is fatal. In addition, backlights are often used with a discharge current of 0.1A or less, but in order to stably form an arc spot at low currents, the diameter of the metal wire forming the electrode must be reduced. As a result, the wires tend to break easily and have a short lifespan. An object of the present invention is to provide a low-pressure discharge lamp that has a long life and is highly efficient.

[Means to solve the problem]

The above object is achieved by employing an electrode consisting of a coil formed of at least two metal wires concentrically and wound in opposite directions. [Function] When at least two metal wires are formed concentrically and with opposite winding directions, a brush-shaped coil is obtained, and therefore, the electron emitting substance held by this coil is difficult to fall off. As a result, long life can be achieved. Furthermore, since the winding direction of the coil is reversed, deformation due to vibration is small, and the electron emitting material is less likely to fall off, resulting in a long life. Furthermore,
Since there are two metal wires, there is less deformation due to vibration and less chance of wire breakage. When the diameters of the two metal wires are approximately equal, an electrode with good dimensional accuracy can be obtained, and the manufacturing method can be simplified. When the above-mentioned coil holds an electron-emitting substance, the electrode drop voltage is reduced, and a highly efficient low-pressure discharge lamp can be obtained. If the two metal wires mentioned above are made to have different diameters, the cathode bright spot will be formed on the thin metal wire at low currents, and the cathode bright spot will be formed on the thick metal wire at relatively high currents, allowing a wide current range. Stable discharge can be carried out at the same time, and long life can be achieved. The above effects can be further improved by using a rare gas as the main component of the discharge gas, and by setting the pressure of the rare gas expressed in Torr from 280/M to 2000/M, where M is the atomic weight of the rare gas. more accomplished. The above effect becomes remarkable when the inner diameter of the low-pressure discharge lamp is 10 mm or less and the discharge current is 0.1 A or less.

【Example】

FIG. 1 shows a first embodiment of the invention. Double coil type hot cathodes 1.2 are enclosed at both ends of the straight tube-shaped discharge vessel 4. A vertical cross-sectional view of a portion of the coil of the electrode used in the example of FIG. 1 that is not coated with electron emitting material is shown below.
Shown in Figure 2. A coil 11 made of tungsten wire with a diameter of 0.026 mm and a tungsten coil 1 with the same thickness.
2 are formed concentrically and in opposite winding directions. FIG. 3 is a longitudinal sectional view of the portion of the electrode of the first embodiment coated with the electron emitting material. The electron emitting material 20 is made of oxides of Ba, Sr, and Ca, and is filled in the -order coil. That is, the electrode shown in FIG. 1 is obtained by further winding the coils shown in FIGS. 2 and 3 into a coil shape. A phosphor 3 is coated on at least a portion of the inner surface of the discharge tube 1. In Fig. 1, the discharge tube 4 has an inner diameter of 5.7 mm and a length of 27 mm.
0III11 soda glass tube with phosphor 3 on the inside.
Rare earth phosphor Y203 as: Eu, MgA
11101g: Ce, Tb, 3S r3 (P 04
)2.CaCQ2 mixture was applied. The discharge gas is argon and mercury vapor at 12 Torr. When the above-mentioned low-pressure discharge lamp of the present invention was lit with a discharge current of 30kHz and 40mA, the tungsten line was sufficiently thin, so the electrode operated stably as a hot cathode with a stable arc spot, resulting in a highly efficient low-pressure discharge lamp. Obtained. Also, since the winding directions of coils 11 and 12 are opposite, coils 11 and 12
The tungsten wire forming the coil has an intersection, and the electron emitting material 20 filled in the secondary coil is less likely to fall off even when vibrations are applied, achieving a long life. Furthermore, since the wire diameters of coils 11 and 12 are equal,
It is easier to form the coil, and there is less variation.
A highly accurate electrode was obtained. As described above, the low-pressure discharge lamp of the present invention has a small diameter, high efficiency, and has a long lifespan for other purposes, making it ideal for use as a bank light for liquid crystal display, which strongly requires thinness, high efficiency, and long lifespan. be. Next, a second embodiment of the present invention will be described. FIG. 4 shows a longitudinal cross-sectional view of the portion of the primary and secondary coils of the electrode shown in FIG. 4 that is not coated with electron emitting material. A coil 11 made of a tungsten wire having a diameter of 0.026 mm and a tungsten coil 12 having the same thickness are formed concentrically and in opposite winding directions. FIG. 5 is a longitudinal sectional view 7 of the part of the electrode of the second embodiment where the electron emitting material is coated. The electron emitting material 20 is made of oxides of Ba, Sr, and Ca, and is filled in the -order coil. That is, the electrode shown in FIG. 1 is obtained by further winding the coils shown in FIGS. 4 and 5 into a coil shape. A phosphor 3 is coated on at least a portion of the inner surface of the discharge tube 1. In Figure 1, the discharge tube 4 has an inner diameter of 5.7 mm and a length of 270 cm.
mm soda glass tube, with rare earth phosphor Y20 as phosphor 3 on the inner surface. : Eu, MgA lxlox
g: A mixture of Ce, Tb, 3Sr3(PO4)2-CaCl was applied. The discharge gas is argon and mercury vapor at 12 Torr. When the above-mentioned low-pressure discharge lamp of the present invention was lit with a discharge current of 30 kHz and 30 mA, an arc spot was formed near the coil 12 with a small wire diameter, and the lamp operated stably as a hot cathode, resulting in a highly efficient low-pressure discharge lamp. It was done. When the lamp was lit with a discharge current of 60 mA, an arc spot was formed near the coil 11 having a large wire diameter, and the lamp operated stably as a hot cathode, resulting in a highly efficient low-pressure discharge lamp. Furthermore, the coil 11
Since the winding directions of coil 11 and wire 12 are opposite, the tungsten wire forming coil 11 and wire 2 have an intersection, and the electron emitting material 20 filled in the second coil falls off even if vibration is applied. This has resulted in a longer lifespan. As described above, the low-pressure discharge lamp of the present invention has a small diameter, high efficiency, and has a long lifespan for other purposes, making it ideal for backlights for LCDs, where thinness, high efficiency, and long life are strongly required. be.

【Effect of the invention】

According to the present invention, a small-diameter low-pressure discharge lamp with stable discharge, long life, and high efficiency can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view of Embodiment 1 of the present invention, Figures 2 and 3 are cross-sectional views of Example 1 of the present invention;
The figure is a cross-sectional view of an electrode according to Example 1 of the present invention, and FIGS. 4 and 5 are cross-sectional views of an electrode according to Example 2 of the present invention. Explanation of symbols 1.2... Electrode, 11.12... Coil, 20...
・Electron emitting material.阜／次／／、／２－・・・试敜敜敜敜敜朜数 5藩巳1 I 7λ 2θ ノ／、／２－．・－・Coiled sword...Mr. Muasa ■

Claims (1)

[Scope of Claims] 1. A low-pressure discharge lamp characterized by having an electrode made of a coil formed of at least two metal wires concentrically and with opposite winding directions. 2. The low-pressure discharge lamp according to claim 1, wherein the diameters of the two metal wires are approximately equal. 3. The low-pressure discharge lamp according to claim 1, wherein the two metal wires have different diameters. 4. The low-pressure discharge lamp according to any one of claims 1 to 3, characterized in that the coil holds an electron emitting substance. 5. The low-pressure discharge lamp according to any one of claims 1 to 4, characterized in that the coil is further coiled to form a double coil. 6. 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 280
The low-pressure discharge lamp according to any one of claims 1 to 5, characterized in that it is greater than or equal to /M and less than or equal to 2000/M. 7. The low voltage according to any one of claims 1 to 6, wherein the low pressure discharge lamp has an inner diameter of 10 mm or less and a discharge current of 0.1 A or less. discharge lamp.