JPH06223774A - Non-organic compound for emitter and electrode for discharge lamp employing aforesaid compound - Google Patents

Abstract

PURPOSE:To lengthen the life of an electrode by forming a metallic oxide layer over a metallic wire, and thereby letting non-organic compounds for an emitter, which includes elements furnished with reduction power for emitter material, be adhered thereon. CONSTITUTION:A metallic wire composed of a Fe-Cr-Al alloy (Cr:20, Al:48(wt.%) and remaining is Fe) is formed on a filament in a double coil shape. The aforesaid filament is sintered at 1150 deg.C for 30 minutes in an air environment, so that a metallic oxide layer 3 composed of aluminum oxide is formed on the surface of the filament. Next, 3% Ta by volume the average grain size of which is 5mum, to the total amount of the non-organic compound, is added to the slurry of alkali earth carbonate composed of BaCO3:42.0, SrCO:32.0 and CaCO3:26.0(wt.%) so as to be mixed. Let the aforesaid compound be adhered on the filament, so that an electron emitting layer 1 is thereby formed thereon. The aforesaid filament is incorporated in a fluorescent lamp, and is processed so as to be activated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic composition for an emitter and an electrode for a discharge lamp using this composition, and more particularly to an inorganic composition for an emitter useful for the emitter of the electrode for a discharge lamp.

[0002]

2. Description of the Related Art In a conventional discharge lamp electrode such as a fluorescent lamp, tungsten is used as a filament metal,
A slurry of alkaline earth metal (Ba, Sr, Ca) carbonate is applied to this filament, and activated by heating in a vacuum or in an inert gas atmosphere. The alkaline earth metal carbonate is transformed into an oxide by the activation treatment, lowers the work function of the electrode surface, and acts as an effective component of the emitter material (thermoelectron emitting material).

By the way, it is desired to extend the life of the thermionic emission cathode, which has a life due to the disappearance of the emitter material. The cause of the disappearance of the emitter material is that the cathode is missing due to ion bombardment when the lamp is turned on, and the emitter material evaporates.
There is one. According to the conventional manufacturing method, the bonding strength of the emitter material to the filament is not sufficient, and therefore, it is considered that the emitter material is likely to drop due to ion bombardment. Therefore, in order to extend the life of the thermionic emission cathode, there is a demand for a method of improving the bonding strength of the emitter material to the filament, even though the disappearance due to the evaporation of the emitter material cannot be avoided.

Further, even if the emitter material consisting of an alkaline earth carbonate is reduced on the electrode surface to liberate the alkaline earth metal, the liberated substance becomes a stable oxide or other compound. However, there is a problem in that the emitter material whose work function cannot be lowered remains, and even if the emitter material remains, it is turned off and the lighting time is shortened.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inorganic composition for an emitter and an electrode for a discharge lamp, which uses the composition and has a long lighting time.

[0006]

An inorganic composition for an emitter according to claim 1 of the present invention is characterized by containing an emitter material and an element having a reducing power.

An electrode for a discharge lamp using the inorganic composition for an emitter according to claim 6 of the present invention is provided with a metal oxide layer (3) around a metal wire (2), and the metal oxide layer (3) is provided thereon. The electron-emitting layer (1) is formed by adhering the above-mentioned inorganic composition for an emitter.

[0008]

The inorganic composition for an emitter according to claim 1 of the present invention contains an emitter material and an element having a reducing power.
The reducing power is improved, and the alkaline earth metal that emits electrons is released until the emitter material consisting of alkaline earth carbonate is eliminated and the alkaline earth metal that releases electrons is released. As a result, the emitter of the electrode for a long-life discharge lamp is released. Is useful as

An electrode for a discharge lamp using the inorganic composition for an emitter according to claim 6 of the present invention is provided with a metal oxide layer (3) around a metal wire (2), and the metal oxide layer (3) is provided thereon. Since the electron-emitting layer (1) was formed by depositing the above-mentioned inorganic composition for an emitter, the metal oxide layer (3) has a bonding force between the emitter material contained in the electron-emitting layer (1) and the metal wire (2). Is considered to be improved and the emitter material is less likely to be missing, and thus has a long life.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings according to the embodiments. FIG. 1 is an enlarged cross-sectional view of a discharge lamp electrode according to an embodiment of the present invention. FIG. 2 is a perspective view of a discharge lamp electrode according to an embodiment of the present invention. FIG. 3 is a perspective view showing a double coil filament of an electrode for a discharge lamp according to an embodiment of the present invention.

In the electrode for a discharge lamp of the present invention, a metal oxide layer (3) is provided around a metal wire (2), and an inorganic composition for an emitter is attached thereon to form an electron emission layer (1). is doing.

The metal wire (2) may be a tungsten wire usually used as a filament material, but it is an iron-chromium-aluminum alloy wire whose elemental composition is Cr: 10.0 to 30.0 wt. %, Al: 1.0
-10.0 wt% and the balance: Fe are preferable. This iron-chromium-aluminum alloy wire is more solid than the tungsten wire, which is usually used as a filament material, when the inorganic composition for an emitter is adhered, and the electron emission layer (1) containing the emitter substance and the metal wire (2) are solidified. This is because it contributes to the wearing power.

The metal oxide layer (3) is formed by subjecting the metal wire (2) to heat treatment in the presence of oxygen.
Aluminum oxide is preferable as the metal oxide layer (3). This aluminum oxide layer diffuses not only in the interface of the electron emission layer (1) containing the emitter material but also in the electron emission layer (1), and the electron emission layer (1) and the metal wire (2).
It is useful for improving the sticking force of and making it difficult for the emitter material to be removed.

The above-mentioned inorganic composition for an emitter contains an emitter material and an element having a reducing power. The element having this reducing power is preferably an element belonging to any of Group 3A, Group 4A, or Group 5A, which is easy to oxidize itself and to easily reduce the surrounding alkaline earth metal carbonate. This 3A group,
As an element belonging to either the 4A group or the 5A group,
Examples thereof include Y, Zr, Ta and the like. This 3A group, 4A
The use of elements belonging to either Group 5A or 5A
This is because, in addition to being easily available as a powder, Ba, Sr, and Ca, which are the main components of the emitter material, can be kept in a free state for a long period of time. This reducing element is 2
You may mix and use 1 or more types.

In the inorganic composition for an emitter of the present invention, the element having a reducing power is 0.5 to 1 with respect to the total amount of the inorganic composition.
It is 0.0 vol%. If this addition rate is satisfied, the reducing power will be improved moderately, and the emitter material consisting of carbonate of alkaline earth metal will be reduced on the electrode surface, and the alkaline earth metal contained as its main component will be liberated, and the emitter material Is released until the discharge disappears, and as a result, the discharge lamp electrode can be used for a long time. That is, 10.0v
If it exceeds ol%, the reducing power will be high, but the alkaline earth metal will be liberated quickly, and the disappearance of the emitter material will be accelerated.
The electrode cannot be used for a long time, and a large amount of free Ba, S
Due to r and Ca, the wall surface of the glass tube of the discharge lamp is blackened and the luminous flux of the discharge lamp is shielded. On the contrary, 0.5v
If it is less than ol%, the alkaline earth metal is not sufficiently reduced on the electrode surface and cannot be liberated.

The inorganic composition for an emitter of the present invention is preferably a powder in which an element having a reducing power has a particle size of 0.5 to 5.0 μm. With this particle size, the particle size is approximately the same as the particle size of the emitter material that is normally used, so that mixing can be performed uniformly. When the particle size of the element having a reducing power exceeds 5.0 μm, the mixture becomes nonuniform and the function of sufficiently reducing the surrounding elements cannot be achieved. On the contrary, if the particle size of the element having reducing power is less than 0.5 μm, the reducing power is
Although improved, Ba and S which are the main components of the emitter material
r and Ca are rapidly liberated, accelerating the disappearance of the emitter material,
The electrode cannot be used for a long time.

When manufacturing electrodes for discharge lamps,
The element having a reducing power may be added to the commonly used alkaline earth metal carbonate before or after the alkaline earth carbonate is made into a slurry. As a method of mixing the alkaline earth carbonate and the element having a reducing power, if the alkaline earth carbonate is in the form of a slurry, it may be mixed with a stirrer. If the alkaline earth carbonate is in powder form, it may be mixed with a ball mill, a stirrer or the like.
In this case, if the dry method is used, an element having a reducing power is activated and there is a risk of rapid oxidation. Therefore, it is better to disperse the element in an organic solvent or the like and perform the wet method. After that, the electron emission layer (1) is formed by adhering it to the metal wire (2) around which the metal oxide layer (3) is provided, and the electron emission layer (1) is set on a fluorescent lamp whose inner surface is coated and set in a vacuum. The metal wire (2) is energized to activate the emitter material. A fluorescent lamp can be filled with an inert gas such as argon or neon and mercury and sealed to form a discharge lamp.

Examples of the present invention will be given below. Example 1 The elemental composition of the iron-chromium-aluminum alloy wire used as the metal wire (2) was as follows: Cr: 22.0 wt%, Al:
The balance was 4.8 wt% and the balance was Fe, and the wire diameter was 50 μm. This metal wire (2) was used as a double coil filament as shown in FIG. The primary winding (4) of this double coil has a diameter of 300 μm, and the secondary winding (5) has a diameter of 500 μm.
μm. The total length of the filament of this double coil is 20 mm, and this filament is fired in an air atmosphere at 1150 ° C. for 30 minutes to form a metal oxide layer (3) of aluminum oxide, and then BaCO ₃ : 4.
2.0 wt%, SrCO ₃ : 32.0 wt%, CaCO
₃ : To the slurry of alkaline earth carbonate consisting of 26.0 wt%, 3 vol% of Ta belonging to Group 5A having an average particle diameter of 5 μm was added with respect to the total amount of the inorganic composition, and mixed with a stirrer for 20 minutes. The inorganic composition for an emitter was attached to a filament to form an electron emission layer (1) and then incorporated into a 20 W type high power fluorescent lamp. The activation of the emitter material was carried out by current heating in vacuum so that the filament temperature was 900 ° C. After activation of the emitter material, the fluorescent lamp was filled with argon gas. A continuous lighting test was performed on the created fluorescent lamp at a discharge current of 2 A, and the time until the lamp was naturally turned off was taken as the continuous lighting time. Next, the residual rate of the emitter material after the spontaneous extinction was examined. The residual ratio of the emitter material indicates the ratio of the weight value of the emitter material remaining when the light is naturally turned off to the weight value of the emitter material contained in the attached inorganic composition for an emitter. The measurement of this weight value was carried out by quantitative analysis by EPMA which is usually performed.

Example 2 Elemental composition of the iron-chromium-aluminum alloy wire used as the metal wire (2) except that Ta was added to the slurry of alkaline earth carbonate in an amount of 10 vol% with respect to the total amount of the inorganic composition. , Wire diameter, shape, total length and treatment method,
All were carried out in the same manner as in Example 1.

Example 3 An iron-chromium-aluminum alloy wire used as the metal wire (2) was prepared, except that 0.5 vol% of Ta was added to the total amount of the inorganic composition in the slurry of alkaline earth carbonate. Elemental composition, wire diameter, shape, total length and treatment method are
All were carried out in the same manner as in Example 1.

Comparative Example 1 Iron-chromium-used as the metal wire (2) except that Ta was not added to the slurry of alkaline earth carbonate.
The elemental composition, wire diameter, shape, overall length and treatment method of the aluminum alloy wire were all the same as in Example 1.

Comparative Example 2 Instead of the iron-chromium-aluminum alloy wire used as the metal wire (2) in Examples 1 to 3 and Comparative Example 1 described above,
The wire diameter, shape, total length and treatment method of the metal wire (2) were all the same as in Example 1 except that tungsten wire was used and Ta was not added to the slurry made of alkaline earth carbonate. .

The results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 1 below. Table 1 shows the continuous lighting test with a discharge current of 2 A for the fluorescent lamps produced in Examples 1 to 3 and Comparative Examples 1 to 2, and shows the time until spontaneous extinction and the residual rate of the emitter material at the time of spontaneous extinction. It is shown. As is clear from Table 1, Comparative Example 1
The fluorescent lamps of Examples 1 to 3 take longer to spontaneously extinguish as compared with the cases of ~ 2, and by adding an element having a reducing power to a normal emitter material, the length of the discharge lamp electrode can be increased. It can be said that the life of the discharge lamp electrode is extended and the emitter material in the inorganic composition for an emitter is effectively used because the residual rate of the emitter material is low, and as a result, the life of the discharge lamp electrode is extended. .

[0024]

[Table 1]

[0025]

According to the inorganic composition for an emitter and the electrode for a discharge lamp using this composition of the present invention, the electrode for a discharge lamp using the inorganic composition for an emitter can have a long life.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a discharge lamp electrode according to an embodiment of the present invention.

FIG. 2 is a perspective view of a metal wire of an electrode for a discharge lamp according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a filament of a double coil of an electrode for a discharge lamp according to an embodiment of the present invention.

[Explanation of symbols] 1 electron emission layer 2 metal wire 3 metal oxide layer

Claims (7)

[Claims] 1. An inorganic composition for an emitter, comprising an emitter material and an element having a reducing power. 2. The inorganic composition for an emitter according to claim 1, wherein the emitter material is a carbonate of an alkaline earth metal. 3. The element having a reducing power is a group 3A, 4
The inorganic composition for an emitter according to claim 1 or 2, which is an element belonging to either Group A or Group 5A. 4. The particle size of the element having a reducing power is 0.
The inorganic composition for an emitter according to any one of claims 1 to 3, which has a thickness of 5 to 5.0 µm. 5. The inorganic composition for an emitter according to claim 1, wherein the element having a reducing power is 0.5 to 10.0 vol% with respect to the total amount of the inorganic composition. 6. An electron emission layer (1) comprising a metal oxide layer (3) provided around a metal wire (2), and the inorganic composition for an emitter according to any one of claims 1 to 5 being deposited thereon. An electrode for a discharge lamp, characterized in that 7. The electrode for a discharge lamp according to claim 6, wherein the metal oxide layer (3) is an aluminum oxide layer.