JPS5837942B2 - fluorescent lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluorescent lamp, and more particularly to electrodes sealed at both ends of a lamp tube.

Conventionally, the electrodes sealed at both ends of the lamp tube are made of ternary carbonates of barium, strontium, and calcium (BaCO3, SrC) on a tungsten filament coil.
After sealing electrodes at both ends of the lamp tube, the lamp tube is heated while the inside of the bulb is normally evacuated, and the inside of the lamp tube and the phosphor are heated. After degassing, the filament coil is heated and subjected to decomposition activation treatment to form an electron-emitting substance as an oxide on the filament coil.

However, in fluorescent lamps having electrodes formed in this manner, blackening of the edges may occur during the activation of thermal decomposition of the electron-emitting substance or at the beginning of lamp lighting.

Among these edge blackenings, the blackening that occurs during thermal decomposition activation is caused by reactions shown by the following formulas (1), (2), and (3) occurring during heating of the electrode with electricity.

First, since the thermal decomposition activation treatment is carried out in a high vacuum,
This is based on the fact that the amount of free barium (Ba 2 ) shown in equation (3) is generated in excess of the amount required for thermionic emission, and a large amount of the excess free barium adheres to the inner wall of the lamp tube.

1. Blackening at the initial stage of lighting is caused by the heat generated by lighting, which causes mercury attached to the lead wires that support the filament coil or members for guarding the electrodes, such as the stem, to become blackened on the inner wall of the lamp tube. It adsorbs to the small amount of barium that was not present, causing a blackening phenomenon for a very short period of time.

This invention has been made in view of the above points, and it is an object of the present invention to provide a fluorescent lamp that prevents the blackening of the end of the lamp tube, which occurs during the thermal decomposition treatment of electron-emitting substances or during the initial stage of lighting. .

Since the cause of the blackening described above is free barium produced in excess, the inventors have investigated various methods for suppressing this free barium.

As a result, barium carbonate (B a Co 3) in the electron emissive material applied to the filament coil
It has been found that it is effective to reduce the amount of barium and to expose the barium attached to the tube wall to oxidizing gas to form an oxide.

In this invention, an electron emitting material containing barium carbonate, strontium carbonate, and calcium carbonate as main components and with a molar ratio of barium carbonate of 20 to 45@ is coated on the electrodes sealed at both ends of a fluorescent lamp, and the electron emitting material is coated on the electrodes sealed at both ends of a fluorescent lamp. This method is characterized in that the material is subjected to thermal decomposition activation treatment in a pre-stage part and a post-stage part after the heating and degassing process of the phosphor.

An embodiment of the present invention will be described below. An electron-emitting material mainly composed of ternary carbonate with a molar ratio of barium, strontium, and calcium of 4=3:3 is attached to a tungsten double coil filament in an amount of about 6 Cmg. The electrodes coated with this electron-emitting substance were sealed to both ends of a 40-watt lamp tube whose inner wall was coated with a phosphor.A fluorescent lamp was attached to the exhaust device, and exhaustion of the inside of the lamp tube was started. At the same time, evacuation was continued until the lamp tube was filled with the rare gas.

), the heating of the lamp tube was started via the heating furnace, and the phosphor was degassed, and 5 seconds after the start of evacuation (the pressure inside the lamp tube at this time was 3 Torr).

), the filament coil is energized, and the electron emitting material is subjected to thermal decomposition activation treatment for 15 seconds (this thermal decomposition activation treatment is referred to as a first treatment).

), then this thermal decomposition activation treatment is stopped, and then the filament coil is energized again from 5 seconds before the lamp tube leaves the heating furnace to perform thermal decomposition activation treatment of the electron emitting material for 8 seconds (this thermal decomposition activation The process is called the second process.

) A 40W fluorescent lamp was obtained by using an oxide electrode and filling the lamp tube with mercury rare gas after evacuation.

The fluorescent lamp thus obtained showed almost no blackening at the edges during the thermal decomposition activation of the electron-emitting substance or at the initial stage of lamp operation, and was a fluorescent lamp of good yield and quality.

This is considered to be due to the following reasons.

That is, (IX2) (3) described above by the first process
As shown in the equation, oxide (RO) and excess free barium (Ba) are produced, but barium is extremely chemically active, and free barium produced within the oxide layer, especially at the electrode, is Free barium in the oxide surface layer, which causes blackening of the edges during the thermal decomposition activation treatment and in the early stages of lamp operation, is mainly due to the oxygen released from the phosphor by external heating of the lamp tube after the first treatment. 02), water (H2 0 ), and carbon dioxide gas (CO2) to form barium oxide (Ba
d), and the amount of free barium decreases.

However, at the same time, a part of the surface layer of barium, strontium, and calcium oxides (RO) obtained in the first treatment adsorbs the above impurity gases and forms hydroxides and carbonates corresponding to each element. Although it is a small amount, it forms and causes an adverse effect on the characteristics of the fluorescent lamp.

Therefore, a second treatment of the electrode is performed in order to activate the re-decomposition of the electrode after the latter part of the heating furnace, and impure gas is discharged from the electrode.

In addition, at the time of this second treatment, since the electrode has almost become an oxide from the first treatment, it can be treated at low temperature and easily, so that free barium in the oxide may be generated excessively again in the second treatment. There is also less free barium appearing in the surface layer.

As described above, in the fluorescent lamp of the above embodiment, part of the free barium excessively produced in the first treatment is converted into an oxide, and when the evacuation of the lamp tube is completed, the electrode has an excess of oxide on the surface layer. Because there is almost no free barium,
There is almost no blackening of the edges during the thermal decomposition activation treatment of the electron emitting material or during the initial stage of lighting.

However, the electron emitting substance barium carbonate (BaCO)
As a result of manufacturing fluorescent lamps by varying the amount of 3), it was found that the optimum amount of barium carbonate was 20 to 45 molar ratios.

This means that if the amount of barium carbonate is less than 20% in molar ratio, the absolute amount of barium to maintain lighting for a long time will be insufficient, resulting in a short life as a fluorescent lamp, which is a practical problem. If it exceeds 100%, intermediate substances such as BaW06 shown in formula (2) above are produced in excess, impairing the starting characteristics of the fluorescent lamp or causing blackening while the fluorescent lamp is lit. It was something.

In addition, a suitable effect was shown when the amount of strontium carbonate and the amount of calcium carbonate in the electron emitting material were set to a molar ratio of calcium carbonate/strontium carbonate≦1.2.

This means that when the amount of strontium carbonate and the amount of calcium carbonate are out of the range shown above, the ratio of the amount of strontium carbonate decreases as the amount of calcium carbonate increases, and the ratio of the amount of strontium carbonate decreases. It is thought that the solid solubility of the salt is impaired and thermionic emission itself is reduced.

Barium, strontium, and
In addition to ternary carbonate of calcium, zirconium oxide (Zr
02), barium zirconate (BaZr03)
, Magnesium zirconate (MgZ r03),
Titanium oxide (TiO2) or hafnium oxide (Hf)
It is clear that the same effect can be obtained by mixing O2) or the like.

As described above, in this invention, an electron emitting material is coated with barium carbonate, strontium carbonate, and calcium carbonate as main components, and the molar ratio of barium carbonate is 20 to 45%. Since it has electrodes that have been subjected to thermal decomposition activation treatment in the front and rear stages of the heating and degassing process of the body, it is possible to reduce the amount of barium in the electron emitting material. The amount of barium produced by the step-by-step thermal decomposition activation treatment can also be reduced.
Since the amount of barium required for lighting can be adjusted to the appropriate amount, it is possible to significantly reduce the blackening of the edges during the thermal decomposition activation treatment of the electron emitting material and at the beginning of lighting, resulting in a high yield and high quality fluorescent lamp. It has the effect of improving.

Claims (1)

[Scope of Claims] 1 Main ingredients are barium carbonate, strontium carbonate, and calcium carbonate, and the molar ratio of barium carbonate is 20 to 4.
It has an electrode which is coated with an electron emitting material having a diameter of 5φ and subjected to thermal decomposition activation treatment, dividing the electron emitting material of ζ into a pre-stage part and a post-stage part of the heating and degassing process of the phosphor. Naru fluorescent lamp. 2. The fluorescent lamp according to claim 1, wherein the molar ratio of strontium carbonate to calcium carbonate is calcium carbonate/strontium carbonate≦1.2.