JPH0389443A - Electron emitting material and low-pressure discharge lamp using it - Google Patents

Abstract

PURPOSE:To reduce the starting voltage of a discharge lamp and extend the life by adding Zr of a proper content, and suppressing the early evaporation of an electron emitting material made of carbonate with a small average grain size. CONSTITUTION:Carbonate mainly made of BaCO3, SrCO3, and CaCO3 is formed in an average grain size of 1mum or below, and ZrO is added to suppress early evaporation. The addition is set to 10-30wt.% of carbonate. Or, metal Zr 5-25wt.% is added. The early evaporation of alkaline earth metal carbonate can be satisfactorily suppressed by this addition, the starting voltage is reduced, the dissipation due to early evaporation is prevented, and the life can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an electron radioactive substance and a low pressure discharge lamp having electrodes coated with the electron radioactive substance.

(Prior Art) In low-pressure mercury vapor discharge lamps, such as fluorescent lamps, electrodes are coated with an electron-emitting substance (activated substance-emitter) in order to promote electron emission.

The electron radioactive substances mentioned above are mainly composed of alkaline earth metal carbonates such as barium carbonate, strontium carbonate, and calcium carbonate.The carbonates are ground into fine powder and dissolved into a suspension, and this liquid is applied to the electrodes and fired. By doing so, the oxide is denatured.

By the way, in order to obtain an electron radioactive substance with excellent activation,
It is said that it is advantageous for the particle size of the alkaline earth metal carbonate to be as small as possible, and JP-A-62-76129 discloses that the average particle size is 0. 5-1 jm, i.e. 1μ
It has been proposed that an alkaline earth metal carbonate formed below m may be used.

When the particle size of the electron radioactive substance made of alkaline earth metal carbonate is reduced, it becomes more active, and when heated with electricity, electron radioactive substances such as barium are easily liberated, and this free #1
As a result of the increased amount of electron emissive material compared to conventional large particle sizes, starting becomes easier and the starting voltage can be lowered.

However, electron-emitting substances with small particle sizes tend to evaporate quickly, resulting in a shortened electrode life.

By the way, it is known that zirconium oxide zro2, magnesium oxide MgO, metallic zirconium Zr, or the like may be added in order to suppress early evaporation of the electron radioactive substance.

However, in the conventional combination of an electron radioactive substance made of alkaline earth metal carbonate and zirconium, the average particle size of the alkaline earth metal carbonate is 3 to 5 μm.
In contrast, the amount of zirconium added to suppress early evaporation is 5 to 8% by weight in the case of zirconium oxide ZrO2, and 2% by weight in the case of metallic zirconium Zr.
It was ~3% by weight.

(Problem to be Solved by the Invention) However, when using the alkaline earth metal carbonate formed to have an average particle size of 14 m or less, the amount of zirconium added, that is, the amount of zirconium oxide ZrO If 5 to 8% by weight is added for metal zirconium 2, and 2 to 3% by weight is added for metal zirconium 2, the amount of zirconium added will be relatively insufficient, and the role of suppressing carbonate evaporation will not be sufficiently fulfilled. It turns out.

The present invention provides an electron radioactive material that suppresses early evaporation and has a long life when an alkaline earth metal carbonate with an average particle size of 1 μm or less is used to obtain an electron radioactive material with excellent activation. The present invention also aims to provide a low-pressure discharge lamp using the same.

[Structure of the Invention] (Means for Solving the Problems) The first aspect of the present invention is to prepare carbonates mainly consisting of barium carbonate, strontium carbonate, and calcium carbonate with an average particle size of 1.
In an electron radioactive material formed to a size of μm or less and formed by adding zirconium oxide to this carbonate for the purpose of suppressing early evaporation, the zirconium oxide is added at a ratio of 10 to 30% by weight based on the carbonate. It is characterized by

Radioactive material.

The second aspect of the present invention is that in an electron radioactive material containing metallic zirconium for the purpose of suppressing early evaporation, this metallic zirconium is added in an amount of 5 to 25 ft% based on the carbonate.
It is characterized in that it is added at a ratio of

The third aspect of the present invention is to apply an electron radioactive substance to the electrode sealed inside the arc tube, and this electron radioactive substance is barium carbonate,
In a low-pressure discharge lamp, zirconium oxide is added to a carbonate mainly composed of strontium carbonate and calcium carbonate with an average particle diameter of 1μ or less for the purpose of suppressing early evaporation, in which the zirconium oxide is added to the carbonate. Against 1
The fourth feature of the present invention is that in a low-pressure discharge lamp in which metallic zirconium is added for the purpose of suppressing early evaporation, this metallic zirconium is added to the above carbonate. It is characterized in that it is added at a ratio of 5 to 25% by weight.

(Function) In all cases of the present invention, since zirconium is added in an appropriate amount, the evaporation of electron radioactive substances made of carbonate with a small average particle size is effectively suppressed, and therefore the starting voltage is lowered. It also prevents dissipation due to early evaporation, resulting in a longer life.

(Example) The present invention will be described below based on an example shown in the drawings.

FIG. 1 is a sectional view showing the structure of a straight tube type fluorescent lamp, and 1 is an arc tube bulb. The arc tube 1 has a straight tube shape, and openings at both ends are sealed by flare stems 2.2. Each of these stems 2.2 is encapsulated with an electrode 3.3.

These electrodes 3.3 are composed of a coiled filament 4 made of tungsten and lead wires 5.5 connected to both ends of this filament 4. The lead wire 5.5 passes through the flare stem 2 in an airtight manner and is led out.

Although not shown, the filament 4 is coated with an electron emissive substance (emitter), which will be described later.

A phosphor coating 6 is formed on the inner surface of the arc tube bulb 1, and a predetermined amount of mercury and argon Ar at a predetermined pressure are sealed inside the arc tube bulb 1.

The electron radioactive material applied to the electrode 3 will be explained.

The electron radioactive substance is composed of a ternary carbonate mainly consisting of barium carbonate, strontium carbonate, and calcium carbonate, and the average particle size of the ternary carbonate is 1 μm or less. When using an electron radioactive substance made of this ternary carbonate,
Since the particle size is small, it is easily activated, and when heated with electricity, electron radioactive substances such as barium are easily liberated, and the amount of liberated electron radioactive substances increases compared to conventional particles with a large particle size. Therefore, starting becomes easy and it is effective in lowering the starting voltage.

However, when an electron radioactive substance made of a ternary carbonate with an average particle diameter of 1βm or less is used, the particles are small and easily scatter, resulting in the electron radioactive substance being consumed early.

Therefore, zirconium oxide or metal zirconium is added to the carbonate having an average particle size of 1 μm or less in order to prevent the carbonate from scattering prematurely.

When using zirconium oxide as zirconium, it is added at a ratio of 10 to 30% by weight based on the carbonate,
When metal zirconium is used, it is added in an amount of 5 to 25% by weight based on the carbonate.

The amount added to these zirconium oxides or metallic zirconium was determined through experiments by the present inventors, and the experiments will be described below.

To produce the electron radioactive substance of the present invention, each of barium hydroxide (Ba (OH) 2 .8H20), strontium hydroxide (S r (OH) 2 .8H20), and calcium hydroxide (Ca (OH)) is used. The powders are mixed in a molar ratio of 1:1:1. This powder is suspended in pure water at a total mole number of 0.5 moles/g. This suspension is stirred while maintaining its temperature at 50±5° C., and carbon dioxide gas (CO□) is blown into the suspension during this stirring. As a result, barium (Ba), strontium (Sr)
), a ternary carbonate of calcium (Ca) is precipitated.

After about 3 hours, the precipitate is filtered, dried and milled to reduce the average particle size to, for example, 0.2JII11.
A finely powdered ternary carbonate can be obtained.

The present inventors then obtained the fine powder 3 obtained in this way.
Zirconium oxide or metal zirconium was added to the original carbonate, and the degree of evaporation at high temperatures was measured by changing the content ratio.

The measurement method was to measure the amount of weight loss when a temperature of 1500° C. was applied in the air for 10 hours, and the degree of evaporation was evaluated.

The results are shown in FIG.

The conventional example shown in FIG. 2 is a ternary carbonate having an average particle size of 3.5 μm containing 5% by weight of zirconium oxide, and has a relatively high evaporation suppressing effect.

When adding zirconium for the purpose of preventing the scattering of electron radioactive substances made of finely powdered ternary carbonate, do not add more than 10% by weight for products using zirconium oxide, as shown by characteristic a in Figure 2. It can be seen that the same evaporation suppressing effect as the above-mentioned conventional method cannot be obtained.

Furthermore, when metallic zirconium is used as the zirconium, as shown in the characteristics shown in FIG. 2, it can be seen that if 5% by weight or more is added, the same evaporation suppressing effect as in the prior art can be obtained.

Next, the present inventors used an electron radioactive material obtained by adding zirconium oxide or metal zirconium to the finely powdered ternary carbonate in a 2°W straight tube fluorescent lamp as shown in Fig. 1. I experimented.

That is, a powder obtained by mixing the finely powdered ternary carbonate and zirconium oxide or metal zirconium was dissolved in a suspension and applied to the coil filament 4, which was then dried and fired to adhere to the filament 4.

FIG. 3 shows the results of investigating the starting voltage of such a lamp.

In Fig. 3, the conventional example shown is a ternary carbonate with an average particle size of 3.5 μm containing 5% by weight of zirconium oxide, similar to the example in Fig. 2, and the starting voltage is Relatively high.

In the case where zirconium oxide is added as zirconium for the purpose of preventing the scattering of electron radioactive substances, the starting voltage becomes significantly lower than that of the conventional one at 30% by weight or less, as shown by characteristic a in FIG.

When the amount exceeds 30% by weight, the starting voltage increases rapidly, and this is because the content of the electron radioactive substance having a small particle size decreases.

In addition, when metallic zirconium is used as the zirconium, as shown in the characteristics shown in Figure 3, the starting voltage drops significantly below 25% by weight, and conversely, beyond that, the starting voltage rises rapidly. do.

Therefore, when adding zirconium oxide, 10
The content should preferably be at least 30% by weight, and if metal zirconium is added, the content should be at least 5% by weight and 25% by weight.
The following content is good.

In this way, since the electron radioactive substance made of ternary carbonate with an average particle size of lja or less is used, it is easy to activate, and when heated with electricity, the electron radioactive substance is easily liberated and the starting voltage is lowered. I can do it.

Moreover, zirconium oxide is 10 to 3
Since the metal zirconium was added at a ratio of 0% by weight or 5 to 25% by weight relative to the above carbonate,
Evaporation of electron radioactive substances is suppressed.

Therefore, it is possible to obtain a fluorescent lamp that maintains a low starting voltage state for a long period of time.

Note that the present invention is not limited to the straight tube type fluorescent lamp shown in FIG. The lamp is not limited to a hot cathode, but may be a cold cathode fluorescent lamp.

In addition to fluorescent lamps filled with mercury, there are also rare gas discharge lamps filled with xenon gas (Xe) without mercury, and other conventional lamps such as barium (Ba), strontium (Sr), calcium It is applicable to lamps that use an electron-emitting substance made of ternary carbonate of (Ca).

[Effects of the Invention] As explained above, according to the present invention, since zirconium is added in an appropriate amount, the evaporation of the electron radioactive substance made of carbonate with a small average particle size is effectively suppressed.
Therefore, the starting voltage is lowered and dissipation due to early evaporation is prevented, resulting in a longer life.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; Fig. 1 is a side view of a straight tube fluorescent lamp, Fig. 2 is a characteristic diagram showing the relationship between zirconium content and evaporation amount, and Fig. 3 is a diagram showing the relationship between zirconium content and evaporation amount. FIG. 3 is a characteristic diagram showing the relationship between the amount and the starting voltage. 1... Arc tube bulb, 3. 3... Electrode, 4... Coil filament, 5... Lid wire.

Claims (4)

[Claims] (1) In an electron radioactive material formed by forming a carbonate mainly consisting of barium carbonate, strontium carbonate, and calcium carbonate into a size with an average particle size of 1 μm or less, and adding zirconium oxide to this carbonate, the above-mentioned oxidation An electron radioactive substance characterized in that zirconium is added in a proportion of 10 to 30% by weight based on the carbonate. (2) In an electron radioactive material formed by forming a carbonate mainly consisting of barium carbonate, strontium carbonate, and calcium carbonate to a size with an average particle size of 1 μm or less, and adding metal zirconium to this carbonate, the above metal An electron radioactive substance characterized in that zirconium is added in a proportion of 5 to 25% by weight based on the carbonate. (3) An electron radioactive substance is applied to the electrode sealed inside the arc tube, and this electron radioactive substance is mainly composed of barium carbonate, strontium carbonate, and calcium carbonate and has an average particle size of 1 μm.
A low-pressure discharge lamp obtained by adding zirconium oxide to the carbonate formed below, wherein the zirconium oxide is added in a proportion of 10 to 30% by weight relative to the carbonate. (4) An electron radioactive substance is applied to the electrode sealed inside the arc tube, and this electron radioactive substance is mainly composed of barium carbonate, strontium carbonate, and calcium carbonate, and has an average particle size of 1 μm.
A low-pressure discharge lamp obtained by adding metal zirconium to the carbonate formed below, wherein the metal zirconium is added in a proportion of 5 to 25% by weight relative to the carbonate.