JPH05251042A - Low-pressure discharge lamp - Google Patents

Abstract

PURPOSE:To reduce the consumption of electron radiating substance and to obtain a discharge lamp of a long service life, by using a rhenium-tangsten to form the filament of a low-pressure discharge lamp used at a specific tube diameter and a specific lamp current. CONSTITUTION:Glass stems 3 are welded to both sides of a glass tube 1 whose tube diameter is less than 10mm, lead wires 4 are sealed to the stems 3, and filaments 6 to which thermionic radiation substance 5 is applied are connected to the tips of the lead wires 4. As the filaments 6, a triple coil made by winding a tangsten wire with a rhenium-tangsten wire to make its primary winding is used. Argon gas 7 and mercury 8 are sealed in the tube 1. By using rhetium- tangsten as the material of the filaments, the resistance value of the filament is increased, and the heating energy is increased, even though the current value is the same, and the cathode drop voltage is lowered. Consequently, the consumption of the electron radiating substance is reduced, and a long service life can be obtained even though the lamp current is a minute current of 40mA or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure discharge lamp, and more particularly to a low pressure discharge lamp having a small diameter and a low lamp current, such as a fluorescent lamp for a backlight.

[0002]

2. Description of the Related Art The hot cathode discharge lamp and the cold cathode discharge lamp are described in the Lighting Handbook edited by The Institute of Lighting, (553 1978).
Mon, Ohmsha, Ltd.), page 759. Also,
The hot cathode fluorescent lamp is described on page 160 of the same document. Also, the material of the filament of the hot cathode lamp is the Writing Handbook edited by Japan Society of Illumination (Showa 6).
Tungsten has been used as described on page 119 of Ohmsha, Nov. 2).

[0003]

In the above-mentioned conventional hot cathode type low pressure discharge lamp, the lamp current is mainly from 100 mA to 1.5 mA.
It is used in A grade. The filament determines the wire diameter of tungsten so that it will self-heat to about 800 ° C. at its lamp current. Lamp current 4
At 0 mA or less, the wire diameter of tungsten must be 0.02 mm or less, but there is a problem with the strength of the filament, and for double coil filaments, the wire diameter is 0.026 mm.
As described above, in the triple coil filament, the strength of the filament cannot be secured unless the wire diameter of the sub wire is 0.02 mm or more.

When a filament having a large wire diameter is used for the lamp current, the amount of heat generated by the filament due to self-heating is reduced. For this reason, the amount of heat necessary for emitting thermions is not secured, so that the cathode drop voltage remarkably rises, and the consumption rate of the thermionic emissive material becomes extremely high. Since the thermionic emissive substance moves to the tube wall by diffusion, the consumption rate of the thermionic emissive substance is more remarkable as the tube diameter is smaller. Therefore, with a pipe diameter of 10 mm or less,
In addition, a small-diameter fluorescent lamp used with a minute current such as a lamp current of 40 mA or less has a drawback that its life is particularly shortened.

An object of the present invention is to provide a hot cathode type low pressure discharge lamp which has a long life with a tube diameter of 10 mm or less and a lamp current of 40 mA or less.

[0006]

The above object is achieved by using rhenium tungsten as a material of a filament for a fluorescent lamp.

[0007]

By using rhenium-tungsten as the material of the filament for the fluorescent lamp, the resistance value of the filament can be raised (Re3% -W97%, about 1.7 times that of tungsten. Re26% -W34%, tungsten About 5 times). As a result, the amount of heat generated by the filament is large even if the current value flowing through the filament is the same. As a result, the amount of heat necessary for emitting thermoelectrons is secured, and the cathode drop voltage can be reduced.

The reduction of the cathode drop voltage reduces the wear of the electron emitting material, resulting in a long-life fluorescent lamp.

[0009]

1 is a sectional view of a lamp according to the present invention. The glass tube 1 is a small one having a total length of 400 mm or less and an inner diameter of 6.5 mm. The phosphor 2 is applied to the inner surface, dried, and then baked and baked. Then, the glass stems 3 are welded to both sides of the glass tube 1. This glass stem 3
Has a lead wire 4 sealed, and a filament 6 coated with a thermoelectron emissive substance 5 is connected to the tip of the lead wire 4.

The filament 6 has a main wire diameter of about 0.03 mm.
A triple coil is used in which a rhenium tungsten wire having a wire diameter of 0.018 mm is wound around the tungsten wire to be the primary winding. This rhenium tungsten wire uses an alloy of 3% rhenium and 97% tungsten.

As the thermionic emissive substance 5, triple carbonate used in a general fluorescent lamp is ball-milled together with nitrocellulose. The application amount is about
It is 1.5 mg. After that, as in the usual method for manufacturing a fluorescent lamp, the inside of the glass tube 1 is evacuated and the filament is energized to heat and activate the thermionic emissive material 5. Argon gas 7 with a pressure of around 20 Torr is placed inside the glass tube 1.
Then, about 5 mg of mercury 8 is sealed, and the exhaust pipe 9 is chipped.
Complete.

When the lamp manufactured according to this example was lit at a high frequency with a lamp current of 10 mA, the life of the lamp was about twice as long as that of a lamp using a usual thermoelectron emissive material.

[0013]

According to the present invention, it is possible to provide a long-life small-diameter low-pressure discharge lamp.

[Brief description of drawings]

FIG. 1 is a sectional view of a low pressure discharge lamp according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass tube, 2 ... Phosphor, 3 ... Glass stem, 4 ... Lead wire, 5 ... Thermoelectron emissive material, 6 ... Filament, 7
... Argon gas, 8 ... Mercury, 9 ... Exhaust pipe.

Claims (1)

[Claims] 1. A low-pressure discharge lamp used with a tube inner diameter of 10 mm or less and a lamp current of 40 mA or less, wherein rhenium tungsten is used as a material of a filament.