JPH10144202A - Negative electrode for electron tube and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a negative electrode, of which lifetime is prolonged so as to improve the profitability, by including at least one kind of metal, which is selected from a group of vanadium or the like, with the oxide of alkaline rare earth metal, which includes barium, as an electron emitting material. SOLUTION: A metal base 3 is provided in an opening part of one end of a cylindrical sleeve 2, and the base 3 is mainly composed of nickel, and the base 3 includes a fine quantity of reduction element such as magnesium. The base 3 is coated with the electron emitting material composed of alkaline rare earth metal oxide 5, which includes barium or the like, and vanadium 6. Namely, the base 3, which is mainly composed of nickel, is coated with the electron emitting material, which is mainly composed of the oxide of alkaline rare earth metal and which includes at least one kind of vanadium, niobium, tantalum at 0.002-6wt.% in relation to the total weight of the oxide. With this structure, emission current can be stabilized for a long time, and a profitable device having a long lifetime can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode for an electron tube such as a cathode ray tube (CRT) used for a television or information display, a so-called display, and more particularly to an electron emitting material of the cathode and a method for producing the same.

[0002]

2. Description of the Related Art As shown in FIG. 9, a conventional electron tube cathode includes a heater coil 1, a cylindrical sleeve 2 containing the heater coil 1, and a nickel-based sleeve provided at one end opening of the sleeve 2. And a metal substrate 3 containing a trace amount of a reducing element such as magnesium, and an electron emitting material layer 4 deposited on the substrate 3. The electron emitting material layer 4 has an alkaline earth material containing barium. A material containing an oxide of a similar metal as a main component is used as a so-called oxide cathode.

In such a cathode, a phenomenon in which the emission current gradually decreases due to the deterioration of the electron-emitting material in a long-time operation of several thousand hours is observed. There is also a proposal that the life can be prolonged by adding 0.3 to 15% by weight of a rare earth metal oxide such as scandium oxide or yttrium oxide to the electron emitting material layer (for example, see Japanese Patent Application Laid-Open No. 62-22347). ).

[0004]

For the time being, it is a technical problem for the electron tube cathode to suppress the deterioration of the electron emitting material and reduce the decrease in the emission current.

[0005] It is a main object of the present invention to realize an economical electron tube cathode having a long life and being economical.

[0006]

The feature of the present invention is that at least one metal selected from vanadium, niobium and tantalum is used together with an oxide of an alkaline earth metal containing barium as an electron emitting material of a cathode for an electron tube. Due to the inclusion, the effect of suppressing the performance deterioration of the electron emitting material and reducing the decrease in the emission current of the cathode could be confirmed.

[0007]

DETAILED DESCRIPTION OF THE INVENTION An electron tube cathode according to claim 1 of the present invention comprises a metal base containing nickel as a main component and an oxide of an alkaline earth metal as a main component, composed of vanadium, niobium and tantalum. An electron emitting material containing at least one selected metal is applied. As a result, the emission current can be stabilized for a long time, and an economical and long-life electron tube cathode can be realized.

[0008] The electron tube cathode according to claim 2 of the present invention comprises:
2. The electron tube cathode according to claim 1, wherein the total content of metals selected from vanadium, niobium, and tantalum is 0.001 to the total weight of the electron-emitting substance mainly composed of an alkaline earth metal oxide. % By weight or more and 5% by weight or less. As a result, the emission current is stabilized for a long time, and the life of the cathode can be extended.

According to a third aspect of the present invention, there is provided an electron tube cathode comprising:
An electron-emitting substance containing an oxide of an alkaline earth metal as a main component and containing at least one metal oxide of vanadium oxide, niobium oxide, and tantalum oxide is deposited on a metal base containing nickel as a main component. . As a result, the emission current can be stabilized for a long time, and an economical and long-life electron tube cathode can be realized.

The electron tube cathode according to claim 4 of the present invention comprises:
The electron tube cathode according to claim 3, wherein the total content of metal oxides selected from vanadium oxide, niobium oxide, and tantalum oxide is based on the total weight of the electron-emitting substance mainly composed of an alkaline earth metal oxide. Therefore, the content is 0.002% by weight or more and 6% by weight or less. As a result, the emission current is stabilized for a long time, and the life of the cathode can be extended.

[0011] The electron tube cathode according to claim 5 of the present invention comprises:
The average particle diameter of a metal oxide selected from vanadium oxide, niobium oxide, and tantalum oxide is 10 μm or less. This stabilizes the emission current for a long time,
The service life of the cathode can be extended.

According to a sixth aspect of the present invention, there is provided a method for producing an electron tube cathode, comprising: a carbonate in which at least one element selected from vanadium, niobium and tantalum is coprecipitated with an alkaline earth metal;
It is provided with a step of thermally decomposing to an oxide. According to this method, the life can be extended as compared with the case where vanadium, niobium, and tantalum are contained as particles.

According to a seventh aspect of the present invention, there is provided a method of manufacturing an electron tube cathode, wherein the carbonate in which vanadium or niobium is coprecipitated with an alkaline earth metal is formed of vanadium nitrate or niobium nitrate and an alkaline earth metal nitrate. It is obtained by a neutralization reaction between a mixed aqueous solution and at least one aqueous solution selected from the group consisting of alkali metal carbonate, alkali metal bicarbonate, ammonium carbonate and ammonium bicarbonate. According to this method, the amount of impurities remaining in the electron-emitting material is reduced, and the life of the cathode can be extended.

[0014] In the method for manufacturing an electron tube cathode according to claim 8 of the present invention, the carbonate in which tantalum is coprecipitated with an alkaline earth metal may be a mixed aqueous solution of an alkali metal carbonate and tantalum, and an alkaline earth metal. It is obtained by a neutralization reaction with an aqueous metal nitrate solution. According to this method, the amount of impurities remaining in the electron-emitting material is reduced, and the life of the cathode can be extended.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a schematic structure of an embodiment of an electron tube cathode according to the present invention. In FIG. 1, an electron tube cathode includes a heater coil 1, a tubular sleeve 2 containing the heater coil 1, and a nickel-based, trace amount of a reducing element such as magnesium provided at one end opening of the sleeve 2. A metal substrate 3 containing barium and an alkaline earth metal oxide 5 containing barium deposited on the substrate 3
And an electron emitting material layer made of vanadium 6.

The electron tube cathode of the first embodiment will be described sequentially along the manufacturing process. 0.8% by weight of barium and strontium in a binary carbonate having a molar ratio of 1: 1
(1.1% by weight with respect to the electron emitting material layer) or 1.0% by weight (1.3% by weight with respect to the electron emitting material layer) vanadium oxide, and barium strontium carbonate and A mixture with vanadium or vanadium oxide was made. The mixture is applied to a cathode substrate for about 50
μm thick, pyrolyzed at 930 ° C in vacuum,
An electron tube cathode having a structure shown in FIG. 1 having an electron emitting material layer made of barium / strontium oxide and vanadium or vanadium oxide was prepared.

The obtained electron tube cathode was used for a CRT for a display, and a current density at the start of the operation of the CRT was set to 2.0 A / cm ^2, and an accelerated life test for 2,000 hours was performed.

FIG. 2 shows a change with time of the emission current in the accelerated life test.
Is the electron tube cathode of the present invention in which vanadium is added to the electron emitting material layer, the characteristic B is the electron tube cathode of the present invention in which vanadium oxide is added to the electron emitting material layer, and the characteristic a is that the electron emitting material layer is alkaline earth. 1 shows a conventional electron tube cathode made only of a metal oxide.

As is clear from FIG. 2, when vanadium or vanadium oxide is added to the electron emitting material layer, the emission current in the accelerated life test is reduced as compared with the conventional electron tube cathode made of only alkaline earth metal oxide. It can be seen that it is greatly suppressed and a longer life can be achieved.
In particular, when vanadium oxide is added, the decrease in emission current is smaller and the effect is greater.

Vanadium and vanadium oxide are easy to obtain industrially and are inexpensive.
By adding vanadium or vanadium oxide to the electron emitting material layer, an economical electron tube cathode can be realized.

As shown in FIG. 3, the amounts of vanadium and vanadium oxide added are 0.001 to 5% by weight and 0.005% by weight, respectively, based on the entire electron emitting material layer.
In the range of 2 to 6% by weight, an effect of suppressing a decrease in emission current was observed. In particular, as shown in this embodiment, the amount of vanadium and vanadium oxide added to the electron-emitting material layer was around 1.1% by weight and 1.3%, respectively.
The greatest effect was obtained when the weight ratio was set at around%.

In this embodiment, the case where a binary oxide of barium / strontium is used as the alkaline earth metal oxide has been described. However, the same effect can be obtained even when a ternary oxide of barium / strontium / calcium is used. Is obtained.

(Embodiment 2) Next, a second embodiment of the present invention will be described.

In the manufacture of the electron tube cathode having the structure shown in Example 1, niobium oxide was used in place of vanadium oxide in an amount of 1% by weight based on barium strontium carbonate (1.3% by weight based on the electron emitting material layer). ) To form a mixture, and the mixture is applied to a cathode substrate of about 50 μm
And thermally decomposed in vacuum at 930 ° C. to produce an electron tube cathode having an electron emitting material layer composed of barium / strontium oxide and niobium oxide.

The electron tube cathode thus obtained was used for a CRT for a display, and a current density at the start of the operation of the CRT was set to 2.0 A / cm ^2, and an accelerated life test of 2,000 hours was performed. As for the reduction of the emission current, the same result as in the case where vanadium oxide was added was obtained, and a longer life was realized.

Further, in the electron tube cathode of this embodiment, there is an action of suppressing the thermal shrinkage of the electron emitting material layer, whereby the change of the cutoff voltage is reduced. Here, the cut-off voltage indicates a cathode voltage at which the emission current is cut off, and its value changes due to the occurrence of thermal contraction of the electron-emitting material layer.

FIG. 4 shows the change over time of the cut-off voltage in the accelerated life test. The characteristic C in the figure shows the electron tube cathode of this embodiment in which niobium oxide was added to the electron emitting material layer. As is clear from FIG. 4, when niobium oxide is added to the electron emitting material layer, the change in the cutoff voltage in the accelerated life test becomes small. In this embodiment, the case where niobium oxide is added to the electron emitting material layer has been described, but the same result is obtained when niobium is added. Also, niobium and niobium oxide, like vanadium,
Since it is easily available industrially and is inexpensive, an economical electron tube cathode can be realized by adding niobium or niobium oxide to the electron emitting material layer. Regarding the addition amount of niobium and niobium oxide, as in the case of vanadium and vanadium oxide described in Example 1, 0.001 to 5% by weight and 0.002 to 6% by weight with respect to the electron emitting material layer, respectively. Within the range, the effect of suppressing a decrease in emission current was observed.

(Embodiment 3) Next, a third embodiment of the present invention will be described.

In the manufacture of the electron tube cathode having the structure shown in Example 1, 1% by weight of barium strontium carbonate was replaced with tantalum oxide instead of vanadium oxide (1.3% by weight with respect to the electron emitting material layer). ) To form a mixture, and the mixture is placed on a cathode substrate by about 50 μm.
m, and thermally decomposed in vacuum at 930 ° C. to prepare an electron tube cathode having an electron emitting material layer composed of barium / strontium oxide and tantalum oxide.

The obtained electron tube cathode was used for a CRT for a display, and a current density at the start of the operation of the CRT was set to 2.7 A / cm ^2, and an accelerated life test of 2,000 hours was performed.

FIG. 5 shows a change with time of the emission current in the accelerated life test.
Indicates the electron tube cathode of this example in which tantalum oxide is added to the electron emitting material layer, and the characteristic b indicates the conventional electron tube cathode.

As is clear from FIG. 5, when tantalum oxide is added to the electron emitting material layer, the decrease in the emission current in the accelerated life test is smaller than that in the conventional electron tube cathode, and the life can be extended. In this example, the case where tantalum oxide was added to the electron emitting material layer was described,
Similar results are obtained when tantalum is added.

Since tantalum and tantalum oxide are easily available industrially and are inexpensive, adding tantalum or tantalum oxide to the electron emitting material layer allows
An economical electron tube cathode can be realized. About the addition amount of tantalum and tantalum oxide, as in the case of vanadium and vanadium oxide described in Example 1,
0.001 to 5% by weight based on the electron emitting material layer
And, in the range of 0.002 to 6% by weight, an effect of suppressing a decrease in emission current was observed.

Further, vanadium oxide,
When niobium oxide or tantalum oxide is added as particles, there is a difference in reduction in emission current depending on the particle diameter of the particles. FIG. 6 shows the relationship between the average particle diameter of tantalum oxide and the emission current (%) after the 2000-hour test when the time before the start of the accelerated life test is 100%. Is 10 μm or less, there is an effect of suppressing a decrease in emission current.

Similar results were obtained when vanadium oxide and niobium oxide particles were added to the electron emitting material layer. Therefore, when vanadium oxide, niobium oxide, or tantalum oxide is added as particles to the electron emitting material layer, the average particle diameter of the particles is preferably 10 μm or less.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described.

The electron tube cathode according to the fourth embodiment will be described sequentially according to the manufacturing process. An aqueous solution of barium and strontium (1: 1 molar ratio) containing vanadium nitrate in a molar ratio of 0.01 mol% to the entire nitrate is added to an alkali metal carbonate or hydrogen carbonate such as sodium carbonate, or ammonium carbonate or ammonium carbonate. By adding an aqueous solution of ammonium hydrogen carbonate, a ternary coprecipitated carbonate of barium, strontium, and vanadium having a vanadium content of 0.01 mol% was prepared.

The above carbonate is applied on the cathode substrate to a thickness of about 50 μm and pyrolyzed at 930 ° C. in vacuum to obtain a barium / strontium / vanadium oxide having a vanadium content of 0.004% by weight. An electron tube cathode having a structure having an electron emitting material layer composed of

The electron tube cathode thus obtained was used for a CRT for a display, and a current density at the start of the operation of the CRT was set to 2.0 A / cm ^2, and an accelerated life test of 2,000 hours was performed. FIG. 7 shows the change with time of the emission current in the accelerated life test.
A characteristic E in the figure indicates an electron tube cathode in which vanadium is coprecipitated in the electron emitting material layer.

As is clear from FIG. 7, when vanadium is co-precipitated in the electron emitting material layer, the decrease in the emission current in the accelerated life test is small, and it can be seen that the life can be extended. Also, instead of vanadium nitrate, niobium nitrate is used to produce barium, strontium,
The same effect was obtained when the co-precipitated oxide of niobium was used as the electron emitting material layer. The addition amount of vanadium and niobium in the present embodiment is 0.00
In the range of 1 to 1% by weight, an effect of suppressing a decrease in emission current was observed.

(Embodiment 5) Next, a fifth embodiment of the present invention will be described.

A method for manufacturing an electron tube cathode according to the fifth embodiment will be described. Barium and strontium (molar ratio 1:
By adding an aqueous solution of an alkali metal carbonate such as sodium carbonate in which 0.01 mol% of tantalum is dissolved in a molar ratio of the total nitrate to the aqueous solution of nitrate 1), tantalum and barium strontium carbonate are dissolved. (A tantalum content of 0.01 mol%) was produced.

The above coprecipitate was applied to a thickness of about 50 μm on a cathode substrate, and pyrolyzed at 930 ° C.
An electron tube cathode having a structure having an electron emitting material layer made of barium strontium oxide containing 14% by weight of tantalum was prepared.

The thus obtained electron tube cathode was used for a CRT for a display, and a current density at the start of the operation of the CRT was set to 2.7 A / cm ^2, and an accelerated life test for 2,000 hours was performed. FIG. 8 shows the change with time of the emission current in the accelerated life test.
The characteristic F in the figure indicates the electron tube cathode of this embodiment in which tantalum is coprecipitated in the electron emitting material layer.

As is clear from FIG. 8, when tantalum is coprecipitated in the electron emitting material layer, the decrease in emission current in the accelerated life test is small, and it can be seen that the life can be extended. With respect to the amount of tantalum added in the present embodiment, the effect of suppressing a decrease in emission current was observed in the range of 0.001 to 1% by weight with respect to the electron emitting material layer.

[0047]

As described above, according to the present invention,
An electron containing, on a metal base containing nickel as a main component, at least one substance selected from vanadium, niobium, tantalum, vanadium oxide, niobium oxide, and tantalum oxide, mainly containing an oxide of an alkaline earth metal. By applying the radiating material, an economical electron tube cathode having a long lifetime can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic structure of an electron tube cathode of the present invention.

FIG. 2 is a characteristic diagram showing a change over time of an emission current in the conventional and present electron tube cathodes.

FIG. 3 is a characteristic diagram showing the relationship between the content of vanadium and vanadium oxide and the rate of decrease in emission current in the electron tube cathode of the present invention.

FIG. 4 is a characteristic diagram showing a change with time of a change amount of a cutoff voltage in the electron tube cathode of the present invention.

FIG. 5 is a characteristic diagram showing a change with time of an emission current in the electron tube cathode of the present invention.

FIG. 6 is a characteristic diagram showing the relationship between the average particle diameter of tantalum oxide and the rate of decrease in emission current in the electron tube cathode of the present invention.

FIG. 7 is a characteristic diagram showing a change with time of an emission current in an electron tube cathode obtained by the method of the present invention.

FIG. 8 is a characteristic diagram showing a change over time of an emission current in an electron tube cathode obtained by the method of the present invention.

FIG. 9 is a sectional view showing a schematic structure of a conventional electron tube cathode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater coil 2 Sleeve 3 Base 4 Electron emitting material layer 5 Alkaline earth metal oxide 6 Vanadium

Claims (8)

[Claims] 1. An electron emitting material containing an oxide of an alkaline earth metal as a main component and containing at least one metal selected from vanadium, niobium, and tantalum on a metal base containing nickel as a main component. An electron tube cathode characterized by being worn. 2. The total content of a metal selected from vanadium, niobium and tantalum is 0.001 to the total weight of an electron-emitting substance mainly composed of an alkaline earth metal oxide.
2. The electron tube cathode according to claim 1, wherein the content is not less than 5% by weight and not more than 5% by weight. 3. Electron radiation containing an alkaline earth metal oxide as a main component and at least one metal oxide of vanadium oxide, niobium oxide and tantalum oxide on a metal base containing nickel as a main component. An electron tube cathode having a substance deposited thereon. 4. The total content of a metal oxide selected from vanadium oxide, niobium oxide and tantalum oxide is 0.002 to the total weight of an electron-emitting substance mainly composed of an alkaline earth metal oxide. 4. The electron tube cathode according to claim 3, wherein the content is at least 6% by weight. 5. The electron tube cathode according to claim 3, wherein the metal oxide selected from vanadium oxide, niobium oxide, and tantalum oxide has an average particle diameter of 10 μm or less. 6. A method for producing an electron tube cathode comprising a step of thermally decomposing a carbonate obtained by coprecipitating at least one element of vanadium, niobium and tantalum with an alkaline earth metal to form an oxide. 7. A carbonate obtained by co-precipitating vanadium or niobium with an alkaline earth metal, comprising: a mixed aqueous solution of vanadium nitrate or niobium nitrate and a nitrate of an alkaline earth metal;
An electron tube cathode characterized by being obtained by a neutralization reaction with at least one aqueous solution selected from the group consisting of alkali metal carbonate, alkali metal bicarbonate, ammonium carbonate and ammonium bicarbonate. Production method. 8. A carbonate obtained by coprecipitating tantalum with an alkaline earth metal, obtained by a neutralization reaction between a mixed aqueous solution of an alkali metal carbonate and tantalum and an aqueous solution of an alkaline earth metal nitrate. A method for producing an electron tube cathode.