JPH07166261A - Electrode material for fluorescent lamp - Google Patents

Abstract

PURPOSE:To produce an electrode material for a fluorescent lamp in which work function is reduced and a drop of voltage in the vicinity of the electrode part is lowly reduced, free from the occurrence of the local concentration of electron emission, having electron emission properties and free from secular change even by use for a long time to reduce the blackening of the edges of the tube. CONSTITUTION:This electrode material for a fluorescent lamp is a one produced from a sintering material in which a base material constituted of metallic powder and powder constituted of electron radioactive substance are uniformly mixed. The electrode material has theoretical density. The base material is constituted of at least one kind selected from the group of W, Mo, Re, Ta, Nb and the alloys thereamong. Moreover, the electron radioactive substance is constituted of at least one kind selected from the group of alkali metal oxide, alkaline earth oxide, rare earth metal oxide, Y2O3, ThO2, Ir2O3, rare earth metal boride, BaB6 and SrB6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material for fluorescent lamps.

[0002]

2. Description of the Related Art Generally, there are two types of fluorescent lamps, a hot cathode type and a cold cathode type. Of these, the hot cathode type has a structure in which the cathode is heated to emit thermoelectrons. Therefore, the luminous efficiency is high, but the service life is short at thousands of hours. For this conventional hot cathode type electrode, Al (ell) ₂ O ₃ , SiO ₂ , K ₂ O doped tungsten (hereinafter referred to as doped W) or ThO ₂ doped W is used. Therefore, the thermoelectron emission property is increased, or evaporation of W itself is prevented (blackening prevention).

On the other hand, since the cold cathode type has a long life of tens of thousands of hours, it has an advantage of being maintenance-free, but depending on the material and structure of the electrode, the voltage drop at the electrode part and its vicinity. Has a drawback that the luminous efficiency becomes large and the luminous efficiency becomes low. This cold cathode electrode is made of a material that is relatively easy to process, such as Ni, Ti, and Al (el), and is formed into a coil shape, a cylindrical shape, or a parallel plate shape, and has low electron emission characteristics. In order to compensate for this, a method of coating the surface with a substance having a good electron emission property such as LaB ₆ , BaO or the like by a method such as sputtering, CVD or the like to increase the luminous efficiency has been adopted.

By the way, Japanese Patent Laid-Open No. 4-272109 (hereinafter referred to as "prior art 1") discloses the above-mentioned electrode material for a cold cathode fluorescent lamp. This cold cathode fluorescent lamp electrode material is formed by doping various metals such as W, Mo, Ta, and Nb with an oxide of an alkaline earth metal, an oxide of a rare earth metal, a boride, a carbide of a transition metal, a nitride, and the like. It is manufactured by extrusion molding by powder metallurgy and sintering. Further, in the prior art 1, a method of doping a metal oxide, boride, or nitride that lowers various work functions by a powder metallurgy method and performing only sintering to finish a predetermined electrode shape is also proposed. There is.

[0005]

However, all the above-mentioned methods have drawbacks. In other words, the work function of the hot cathode electrode material is high and the life is short.

On the other hand, when the coating method is used for the cold cathode electrode material, the coated substance evaporates and disappears during use and returns to the characteristics of the electrode base material after long-term use. Further, there is a problem that the evaporated substance adheres to the inner wall of the bulb to cause blackening of the tube end and reduce the illuminance.

Furthermore, when the sintered material electrode shown in Conventional Example 1 is used, the electrode is a sintered material and does not reach the theoretical density of each metal alloy, and therefore has many pores. Moreover, since it is a solid-phase sintered body, the grain boundary strength between the sintering terminals is weak, and when electrons are blown, the solid-phase sintered metal particles such as W (the specific surface area becomes large, and moreover, compared with the forged material). Since the grain boundary strength is weak), the alloy metal evaporates on the inner wall of the bulb due to the impact of thermionic emission, causing blackening of the tube end and lowering the illuminance.

Therefore, the technical problems of the present invention are to lower the work function, suppress the voltage drop in the vicinity of the electrode portion, to prevent local concentration of electron emission, and to have efficient electron emission characteristics, and to use for a long time. It is also to provide an electrode material for fluorescent lamps that does not change over time and reduces blackening at the tube end.

[0009]

In order to solve the above technical problems, the present inventors sinter alloy powder in which a base material made of metal powder and a powder made of electron-emitting material are uniformly mixed. Then, the present invention was achieved by applying to the electrode a material that has been subjected to plastic working such as forging, rolling, rolling, heat treatment wire drawing, etc., and finished to a theoretical density.

That is, the electrode material for a fluorescent lamp of the present invention is an electrode material made of a sintered material in which a metal base material and fine particles of an electron emitting substance are uniformly mixed, and the electrode material is It is characterized by having a theoretical density.

Further, the fluorescent lamp electrode of the present invention is formed by sintering a mixture in which a base material made of metal powder and a powder made of an electron emissive material are uniformly mixed and sintered, and plastic working by a general powder metallurgy method. The process is characterized by being obtained by plastic working such as forging, rolling, rolling, heat treatment drawing and the like.

The base material used in the present invention is made of a refractory metal or a conductive metal material which is a main component of an electrode. Specifically, W, Mo, R
At least one metal selected from the group consisting of e, Ta, Nb and alloys thereof is used.

Here, the reason why the refractory metal is used in the present invention is that the refractory metal has a low vapor pressure and the evaporation in the valve is small.

Next, in the present invention, the electron emissive substance is a substance which has a function of emitting a large amount of electrons at a lower temperature and a lower voltage than the base metal. As the electron emitting substance, a metal compound having a low work function and a low vapor pressure is preferable. Here, the work function is the amount of energy required to release electrons from the surface of a substance into a vacuum. Therefore, a substance having a smaller work function has a higher electron emission property, which is preferable. Further, a substance having a lower vapor pressure is preferable because it disappears during use and is less likely to change over time. Specific examples of such an electron emitting substance include alkali metal oxides Li ₂ O, Na ₂ O, K ₂ O and Rb.
Alkaline earth metal oxides such as ₂ O and Cs ₂ O include BeO, MgO, CaO, SrO, and BaO, and rare earth metal oxides include La ₂ O ₃ , CeO ₂ , and Pr.
₂ O ₃ , Nd ₂ O ₃ , Y ₂ O ₃ , Sc ₂ O ₃ , Pm ₂ O
₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb
₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂
LaB ₆ , CeB ₆ , PrB ₆ , NdB ₆ , Y as rare earth metal borides such as O ₃ Yb ₂ O ₃ and Lu ₂ O _3.
As rare earth nitrides such as B ₆ , LaN, CeN, Pr
N, NdN, YN, ScN, SmN, EuN, GdN,
DyN etc. can be mentioned. Of these, Ba
O, CaO, La ₂ O ₃ , LaB ₆ , CeO ₂ , Y ₂ O
₃ , LaB ₆ , CeB ₆ , YB ₆ and Li ₂ O are preferable.

Further, in the present invention, when two or more kinds of metal compounds are used for the electron emitting substance, the above compounds can be arbitrarily combined, but alkaline earth metal oxides and alkali metal oxides are preferable. And at least one oxide selected from rare earth oxides, and a mixture of at least one oxide selected from ThO ₂ and Ir ₂ O _{3 in} an amount of 1 to 60% by weight based on the total amount of electron-emitting substances. You can Furthermore, for one or more rare earth metal borides and the total amount of electron emissive material, for example, 1
60 wt% of BaB _6, SrB _6, BeB with one or more borides selected from ₆ mixture can be used.

The particle size (particle size) of this electron-emitting metal compound is in the range of less than 1.0 μm. The amount of the electron emitting substance added is 0.05 to 5 based on the electrode material.
% By weight, preferably 0.5 to 2% by weight. The reason is that if the addition amount (doping amount) is less than 0.05, the effect of electron emission cannot be obtained, and if the particle size of the doping agent is 1.0 μm or more, thermionic electrons cause abnormal discharge. Lamp life is significantly reduced. On the other hand, if it exceeds 5% by weight, cracking occurs in the forging, rolling, rolling, and wire drawing of the sintered ingot, making the processing difficult, resulting in a disadvantage that the processing yield is significantly reduced.

In the electrode material of the present invention, the base material made of the above-mentioned metal and the powder made of the electron emitting substance are uniformly mixed and dispersed and subjected to plastic working such as molding, sintering, rolling, etc. (Cross-section reduction rate) is 80% or more, so that lines finished to theoretical density (theoretical specific gravity),
Obtain rods and plates. An electrode using the electrode material of the present invention is
There is no change over time during use, stable light emission is obtained, and evaporation and spatter of the electron emissive material are suppressed, and blackening of the tube end can also be suppressed.

[0018]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram showing an electrode for a fluorescent lamp according to an embodiment of the present invention. The electrode for the fluorescent lamp shown in FIG. 1 is made of a sintered wire rod called a double coil electrode,
A coil having a wire diameter D ₁ is tightly wound to obtain a primary coil of a core wire diameter D ₂ , and the primary coil is wound at a predetermined pitch P with a predetermined number of turns N, a core wire diameter d, and a predetermined coil length C. ．
It is formed so as to be L. For example,
D ₁ = 0.03 mm, D ₂ = 0.10 mm, P = 1.0
mm, N = 6 turns, d = 1.2 mm, C.I. L. = 6m
m.

Further, the fluorescent lamp electrode (not shown) is
There is a so-called single coil electrode. This single coil electrode is a single wire of the primary coil shown in FIG.

FIG. 2 is a partially cutaway sectional view showing a main part of a fluorescent lamp to which the fluorescent lamp electrode of FIG. 1 is attached. As shown in FIG. 2, the fluorescent lamp 10 includes a glass bulb 11, stems 13 provided at both ends of the glass bulb 11, a base pin 15 embedded in the stem 13 and protruding to the outside of the glass bulb 11, and a base. Wells (conductor) 16 connected to the pin 15 and the wells 16, 16
Electrode 20 for fluorescent lamp, which is composed of W coil provided between
(See FIG. 1) and n from the end of the fluorescent lamp electrode 20.
The auxiliary electrode 22 is provided in a bent shape.
On the inner surface of the glass tube 11, there is provided a fluorescent material layer 17 which is prepared by coating a phosphor in the filtered wavelength region so as to have a color temperature of 7500K, and a few mg of mercury (Hg) 19 is deposited on the inner surface of the glass tube 11 at 20 Torr. Argon (Ar) gas is enclosed. The W coil 20 is provided with barium oxide coating or the like.

A lighting circuit (high frequency lighting,
When it is lit at 40 kHz), discharge occurs between the electrodes and Hg1
The fluorescent substance emits light by the ultraviolet ray of 254 nm emitted from 9.

Next, a method of manufacturing the fluorescent lamp electrode 20 will be described.

Powders of metal (W, Mo, Re, Ta, Nb) are prepared. The average particle size of this powder is 1 to 10 μm in Fsss value (value measured by Fischer, sub, sieve, sizer), but preferably 3 to 5 μm
If this is done, the specific gravity of the ingot after sintering will increase, and defects such as cracks during plastic working afterwards will decrease.

On the other hand, electron emitting metal powder FSSS 0.01
A material having an average particle size of ˜1.0 μm is prepared. The smaller the particle size is, the more preferable for uniform dispersion. Next, the metal powder and the electron-emitting metal powder are mixed with a V-type mixer double cone mixer ball mill, vibrating mill, attritor, grinder or the like. After that, molding is performed by a hydrostatic press, a die press, or the like. Square for plate, square bar for bar,
It is desirable to change the shape because the round bar shape facilitates the next plastic working. Next, W, Mo, and Re are in reducing gas,
It depends on the material, but it is about 1800-3000 ℃, T
Sintering is performed for a and Nb in vacuum at about 2000 to 2600 ° C. and for a sintering time of 0.5 to 10 hours. As for the specific gravity (density) of the ingot formed by sintering, 90% or more of the logical density is a desirable value for plastic working in the next process. Next, in the case of a plate, heating and forging or rolling are performed, and in the case of a wire rod, heating and forging or rolling or rolling are performed, and intermediate heat treatment is performed for 1 to 3.
And then wire drawing according to the required diameter,
Get the theoretical density. The material of the finished plate or wire rod is cleaned by electrolytic polishing, chemical polishing or the like on the surface of the material to finish it into a predetermined electrode shape, for example, a double coil electrode shown in FIG. 1 or a single coil electrode not shown. As a method for more evenly and finely dispersing the electron-emissive doping agent, this metal (W, Mo, Re) oxide powder is doped with a water-soluble chloride to dope, mix, dehydrate, and dry. The most preferable method is to make a metal-doped powder by subsequent reduction in a reduction furnace.

Next, a concrete example of manufacturing the electrode material for a fluorescent lamp according to the embodiment of the present invention will be described.

A W blue oxide powder was prepared, doped with a solution of cerium chloride, dehydrated and dried, and then reduced in a hydrogen reduction furnace to obtain cerium oxide-doped W powder FSSS of 3.5 μm. create. Next, it is formed into a rod shape by a die press, pre-sintered, and H ₂
Sintering was carried out in a direct current sintering furnace in an atmosphere. The sintering temperature was about 3000 ° C., the time was 0.5 Hr, the specific gravity was 17.8, and 1% by weight of cerium (Ce) remained. The ingot had a rod-like shape with a cross section of 25 nm × 25 mm. Next, while heating the rod at a heating temperature of 1500 ° C to 1100 ° C, rolling is performed to finish the outer diameter to about 3 mm, and on the way, the diameter is 9.0 m.
Recrystallization heat treatment was performed when m and the diameter were 5.0 mm. Then, it is heated at a temperature of 1000 ° C to 500 ° C, and while being subjected to strain relief heat treatment several times, it is finished into a wire with a diameter of 0.04, and electrolytic polishing is performed to remove the graphite of the lubricant on the surface. Finish into wire with theoretical density of 0.03,
The double coil electrode shown in FIG. 1 was made.

Further, as shown in the prior art 1, in order to produce a cylindrical shape, by rolling, at a diameter of 5.0 mm,
It was easy to cut the material with a material that was not subjected to recrystallization heat treatment to a size of 4 mm in diameter, 0.4 mm in wall thickness, and 7 mm in length, and the effect was as good as the coil.

The wells 16 were spot-welded to the electrode material according to the embodiment of the present invention to form an electrode, and the diameter was 6 mm × 20.
In the glass bulb 11 of 0 mm (170 mm between electrodes),
Encapsulation was performed as shown in FIG.

It is also possible to manufacture the cylindrical electrode of FIG. 1 by rounding and welding the above-prepared plate, and the same effect was obtained. As a comparative example, Al (ell) ₂ O, K ₂ O, SiO ₂ standard dope was prepared. A W double coil filament for a bulb (Reference Example 1) and a coil thereof coated with CeO ₂ by CVD (Comparative Example 1) were prepared.

Since the cathode voltage drop is a voltage of the applied voltage which is decreased near the electrodes and does not contribute to light emission, the lower this voltage is, the higher the light emission efficiency is, which is preferable. The voltage drop was investigated by changing the electrode type in Table 1 below.

[0032]

[Table 1] As is clear from Table 1 above, by changing Ni into doped W, 15 V, and by adding CeO ₂ to W, 3
It can be 5V low range. Even when compared with the conventional Ni-based electrode coated with CeO ₂ ,
The voltage with O ₂ added is 25V lower.

FIG. 4 is a graph showing the degree of blackening at the tube end. In FIG. 4, A is a coil containing CeO _{2 at} 1% by weight, and B is C.
eO ₂ Coated Ni Coil Electrode of Comparative Example 1, C is C
An electrode is used in which a W powder containing 1% by weight of eO _{2 in} a binder is extruded into a linear shape, molded into a coil, and sintered to form a coil. Here, the degree of blackening on the vertical axis in the graph is a visual evaluation of the degree of electrode blackening,
"0" is not blackened, "1" can be confirmed by checking carefully, "2" is slightly blackened, "3" is between 2 and 4, "4"
Indicates blackening over the circumference of the pipe end. As shown in FIG. 4, A is the degree of blackening after 2000HR lighting, A is zero blackening, and B and C are both blackening progressing with time,
It can be seen that the metal and radioactive substances are evaporating.

In particular, by comparing A and C, it can be seen that the material having a specific gravity of 17.8 as sintered (92.7% of the theoretical specific gravity) is also highly blackened. It is thought that this is due to the lack of particle strength and that it cannot withstand thermionic impact.

Table 2 below shows the relationship between the particle diameter of the dopant in the wire and the life of the fluorescent lamp.

The test set forth in Table 2 below was specifically prepared to determine the particle size of the dopant. A W wire having a diameter of 0.03 mm obtained by keeping CeO ₂ at 1% by weight as W was polished and the distribution and particle diameter of the doping agent CeO ₂ were measured by a scanning electron microscope. As a sample, FS
SS 3.5 μm W powder having CeO ₂ powder of different grain size was molded into a doped powder, and after intermediate firing and sintering, plastic working was performed to make a line with a diameter of 0.39 mm, and microscopic examination was performed. still,
With a diameter of 0.03 mm, the wire is too thin and measurement is difficult, so a diameter of 0.39 mm was used. After that, the doped W wires are processed to a diameter of 0.04 mm, electropolished, finished to a diameter of 0.03 mm, a double coil as shown in FIG. 1 is made, set in the fluorescent lamp shown in FIG. 2, and blackened. The time to reach 4 degrees was measured and taken as the life.

[0037]

[Table 2] From Table 2 above, it has been found that the particle size of the doping agent is remarkably reduced when the particle size exceeds 1.0 μm.

[0038]

As described above, according to the present invention, the work function is lowered, the voltage drop in the vicinity of the electrode portion is kept low, the local concentration of electron emission does not occur, and the electron emission characteristic is efficient. However, it is possible to provide an electrode material for fluorescent lamps that does not change over time and reduces blackening at the tube end even after long-term use.

Further, according to the present invention, it is possible to provide an electrode material for a fluorescent lamp which is excellent in plastic workability.

Furthermore, according to the present invention, the powder metallurgy method can be used, and industrialization is easy.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrode for a fluorescent lamp according to an embodiment of the present invention.

FIG. 2 is a partially cutaway sectional view showing a main part of a fluorescent lamp incorporating an electrode for a fluorescent lamp according to an embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the processing rate and the specific gravity (density) of various coils.

FIG. 4 is a diagram showing the degree of blackening at the tube end.

[Explanation of symbols]

 10 Fluorescent Lamp 11 Glass Bulb 13 Stem 15 Base Pin 16 Wells (Conductor) 17 Fluorescent Material Layer 19 Mercury 20 W Coil Electrode 22 Auxiliary Electrode

Claims (6)

[Claims] 1. A fluorescent material, characterized in that the electrode material is made of a sintered material in which a base material made of a metal powder and a powder made of an electron emitting substance are uniformly mixed, and the electrode material has a theoretical density. Lamp electrode material. 2. The fluorescent lamp electrode material according to claim 1, wherein the base material is at least one selected from the group consisting of W, Mo, Re, Ta, Nb and alloys thereof.
An electrode material for a fluorescent lamp, characterized by comprising a seed. 3. The fluorescent lamp electrode material according to claim 1, wherein the electron emitting substance is an alkali metal oxide,
Alkaline earth oxide, rare earth metal oxide, Y ₂ O ₃ , T
hO ₂ , Ir ₂ O ₃ , rare earth metal boride, BaB ₆ ,
An electrode material for a fluorescent lamp, which is at least one selected from the group consisting of SrB ₆ . 4. The electrode material for a fluorescent lamp according to claim 1, wherein the content of the electron emitting substance is 0.05 to 5% by weight based on the electrode material. . 5. The electrode material for a fluorescent lamp according to claim 1, wherein the theoretical density is achieved by plastic working. 6. The fluorescent lamp electrode material according to claim 1, wherein the electron emissive substance is particles having a particle size of less than 1.0 μm uniformly dispersed in the metal base material. Electrode material.