JPH10125214A - Oxide cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a oxide cathode capable of maintaining stable electronic discharge characteristics for a long time under a high electric current density condition. SOLUTION: The cathode comprises a metal sleeve 4 with a high fusing point, a cap shape base 1 fitted to the one end of the sleeve 4 and containing nickel(Ni) as main ingredient and a small quantity of deoxidized metal elements such as silicon(Si), magnesium(Mg) and the like, an electronic discharge material layer coated on a surface of the metal base 1 and containing metal oxide such as barium(Ba), strontium(Sr) and calcium(Ca), and a heater contained in the sleeve 4. Wherein a small quantity of dysprosium oxide (Dy2 O3 ) powder 3 containing particles with a diameter exceeding 4.5μm for each is mixed in the electronic discharge material layer 2. By mixing the dysprosium oxide (Dy2 O3 ) powder 3, an electric resistance is reduced, big joule heat is not produced under high electric current density condition, so that production of free barium(Ba) is not prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide cathode, and more particularly to an oxide cathode used for an electron gun such as a color cathode ray tube or an image pickup tube, which can stably maintain high electron emission characteristics for a long period of time during use. To an oxide cathode prepared as described above.

[0002]

2. Description of the Related Art Conventionally, oxide cathodes used in electron guns such as color cathode ray tubes and image pickup tubes are disclosed in
One disclosed in JP-A-8-154130 and the like is known.

The oxide cathode disclosed in Japanese Patent Application Laid-Open No. 58-154130 is fitted to a sleeve made of a high melting point metal such as molybdenum (Mo), and fitted to one end of the sleeve.
A cap-shaped metal substrate containing nickel (Ni) as a main component and a trace amount of a reducing metal element such as silicon (Si), magnesium (Mg), zirconium (Zr), etc .; barium (Ba), strontium (Sr), and calcium (C
The electron emission material layer is made of the metal oxide of a) and is attached to the surface of the metal substrate, and has a configuration in which a heater is inserted inside the sleeve.

[0004] The oxide cathode according to the above configuration, during operation,
Free barium (Ba) is generated in the electron emitting material layer by a trace amount of reducing metal such as silicon (Si) and magnesium (Mg) contained in the metal substrate, and the generated free barium (Ba) is converted into electrons. Since an atomic layer of barium (Ba) is formed concentrated on the surface of the emitting material layer, many electrons can be continuously emitted from the electron emitting material layer, and an oxide having good electron emission characteristics can be obtained. A cathode is obtained.

[0005]

In recent years, as the definition of an image in a color cathode ray tube, an image pickup tube or the like has advanced, a cathode used in a color cathode ray tube or an image pickup tube has a high current density during operation. In particular, those having stable electron emission characteristics for a long time have been particularly demanded.

Incidentally, the above-mentioned Japanese Patent Application Laid-Open No. 58-154130 has been disclosed.
The known oxide cathode disclosed in No.
When the current density is high, a large current flow is hindered by the electric resistance of the electron emitting material layer and the metal substrate,
At that time, Joule heat is generated to increase the temperature of the electron emitting material layer, causing the electron emitting material layer to melt or evaporate. As a result, the generation of free barium (Ba) in the electron emitting material layer is prevented, the electric resistance of the electron emitting material layer becomes higher, and a vicious cycle occurs in which the flow of current in the electron emitting material layer is hindered.

As described above, Japanese Patent Application Laid-Open No. 58-15413
The known oxide cathode disclosed in No. 0 and the like has a problem that it cannot be operated at a high current density state even if the electron emission characteristics are good.

The present invention has been made to solve the above problems, and has as its object to provide an oxide cathode capable of maintaining stable electron emission characteristics for a long time at a high current density in operation. Is to do.

[0009]

In order to achieve the above object, an oxide cathode according to the present invention comprises a trace amount of dysprosium oxide (Dy ₂ O) containing particles having a particle size exceeding 4.5 μm in an electron emitting material layer. ₃ ) A means for mixing powder is provided.

According to the above means, in the electron emitting material layer,
By mixing a small amount of dysprosium oxide (Dy ₂ O ₃ ) powder containing particles having a particle size exceeding 4.5 μm, the electric conductivity of the electron emitting material layer is improved, and the electric resistance of the electron emitting material layer is thereby increased. Even if the oxide cathode is operated at a high current density, the generation of Joule heat is suppressed, and the electric resistance of the electron emitting material layer is slightly increased, so that the generation of free barium (Ba) is reduced. Not disturbed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, an oxide cathode is fitted to a sleeve made of a refractory metal, and is fitted to one end of the sleeve. A cap-shaped metal substrate containing a trace amount of a reducing metal element such as magnesium (Mg); and a metal oxide of barium (Ba), strontium (Sr), and calcium (Ca), which is adhered to the surface of the metal substrate. A small amount of dysprosium oxide (Dy ₂ O ₃₎ containing particles having a particle size exceeding 4.5 μm in the electron emitting material layer in the oxide cathode including the electron emitting material layer and a heater enclosed in the sleeve. ) A mixture of powders.

In one embodiment of the present invention, the content of dysprosium oxide (Dy ₂ O ₃ ) powder is selected in the range of 0.1 to 7.0% by weight.

In another embodiment of the present invention,
Dysprosium oxide (Dy ₂ O ₃ ) powder has a particle size selected from a range of more than 4.5 μm and up to 20.0 μm.

According to the embodiment of the present invention, a small amount of dysprosium oxide (Dy) is contained in the electron emitting material layer.
₂ O ₃ ) powder is mixed to improve the electric conductivity of the electron emitting material layer, so that the electric resistance in the electron emitting material layer can be reduced, and the device can be operated at a high current density. However, generation of Joule heat based on a high-density current can be suppressed. Since the generation of Joule heat is small, the increase in the electric resistance of the electron-emitting material layer is small, and the generation of free barium (Ba) is not largely hindered. An oxide cathode capable of maintaining stable electron emission characteristics can be obtained.

[0015]

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

FIG. 1 is a sectional view showing the structure of a main part of an embodiment of an oxide cathode according to the present invention.

In FIG. 1, reference numeral 1 denotes a cap-shaped metal base containing nickel (Ni) as a main component and a trace amount of a reducing metal element such as silicon (Si) or magnesium (Mg), and 2 denotes barium (Ba), strontium. (Sr), an electron emitting material layer made of a metal oxide of calcium (Ca), 3 is a dysprosium oxide (Dy ₂ O ₃ ) powder mixed in the electron emitting material layer 2, and 4 is a high-density material such as molybdenum (Mo). A cylindrical sleeve 5 made of a melting point metal is a heater.

Then, the cap-shaped metal base 1 is fitted to one end of the sleeve 4, and the electron-emitting material layer 2 is attached to the surface of the cap-shaped metal base 1. The heater 4 is inserted and fixed in the sleeve 4 from the opening end side. In this case, the sleeve 4 and the lead of the heater 5 are held and fixed to an electron gun structure (not shown) by a holding member (not shown). Also, dysprosium oxide (Dy ₂ O ₃ ) powder 3 having an average particle diameter of 7 μm is mixed in the electron emitting material layer 2 by 0.5% by weight.

The oxide cathode according to the present embodiment having the above structure has
For example, it is manufactured through the following steps.

First, carbonates of barium (Ba), strontium (Sr) and calcium (Ca) {(Ba, S
r, Ca) Dysprosium oxide (Dy ₂ O ₃ ) powder 3 having an average particle diameter of 7 μm and a purity of 99.9% in CO ₃ }
To form a slurry mixed with 0.5% by weight.

Next, this slurry is sprayed onto the surface of the cap-shaped metal base 1 fitted to one end of the sleeve 4 by using a spray gun to form a layer having a thickness of about 70 μm.

Next, carbonates of barium (Ba), strontium (Sr) and calcium (Ca) {(Ba, S
r, Ca) CO ₃ } is heat-treated to obtain barium (Ba),
Oxide of strontium (Sr) and calcium (Ca) {(Ba, Sr, Ca) O}.

Subsequently, oxides of barium (Ba), strontium (Sr), and calcium (Ca) {(Ba, S
(r, Ca) O} is reduced by a trace amount of a reducing metal such as silicon (Si) or magnesium (Mg) contained in the cap-shaped metal substrate 1 to form an activated electron emitting material layer 2. Is done.

In the oxide cathode of this embodiment having such a configuration, a small amount (0.5% by weight) of dysprosium oxide (Dy ₂ O ₃ ) contained in the electron emitting material layer 2 during operation.
The electric conductivity of the electron emitting material layer 2 is improved by the powder 3 as compared with the electron emitting material layer not containing the dysprosium oxide (Dy ₂ O ₃ ) powder 3, and the electric resistance in the electron emitting material layer 2 is reduced. Become. For this reason, even if the oxide cathode of this example is operated at a high current density, the generation of Joule heat based on the high density current is suppressed, and the increase in the electric resistance of the electron emitting material layer 2 is slightly increased. Therefore, the production of free barium (Ba) is not largely hindered, and an oxide cathode that can maintain stable electron emission characteristics for a long time at a high current density can be obtained.

In this case, when the content of the dysprosium oxide (Dy ₂ O ₃ ) powder 3 mixed in the electron emitting material layer 2 becomes 0.1% by weight or more, the dysprosium oxide (Dy ₂ O ₃ )
The effect of adding y ₂ O ₃ ) powder 3 appears. On the other hand, when the content exceeds 7.0% by weight, although the effect of adding dysprosium oxide (Dy ₂ O ₃ ) powder 3 is effective, The initial emission of the oxide cathode will be reduced.

For this reason, in this embodiment, the content of the dysprosium oxide (Dy ₂ O ₃ ) powder 3 is selected in the range of 0.1 to 7.0% by weight.

When the average particle diameter of the dysprosium oxide (Dy ₂ O ₃ ) powder 3 mixed in the electron emitting material layer 2 is 0.5 μm or less, the dysprosium oxide (Dy ₂ O ₃ ) powder No effect due to the addition of No. 3 is exhibited. On the other hand, when the average particle diameter is 20 μm or more,
Dysprosium oxide (Dy ₂ O ₃ ) powder 3 is made of barium (Ba), strontium (Sr), calcium (C
It will not be uniformly mixed in the carbonate (a) {(Ba, Sr, Ca) CO ₃ }.

For this reason, in the present embodiment, the dysprosium oxide (Dy ₂ O ₃ ) powder 3 has an average particle size of 0.1.
It is selected within the range of 5 to 20 μm.

Next, FIG. 2 is a characteristic diagram showing a change with time of the electron activity when the oxide cathode is operated. The horizontal axis is the operation elapsed time in kilohours (KHr), and the vertical axis is the vertical axis. It is a relative value of the electron activity when the initial electron activity is 100.

In FIG. 2, the characteristic (A) shows the characteristic of a color cathode ray tube in which the oxide cathode according to the present embodiment is incorporated in an electron gun, and the characteristic (B) shows that a known oxide cathode is incorporated in an electron gun. This shows the characteristics of a color cathode ray tube.

As shown in the characteristic (B) of FIG. 2, a color cathode ray tube using a known oxide cathode is
At the time when 500 hours have passed, the electron emissivity is about 80%, and when the 1000 hours have passed, the electron emissivity has reached about 65%.
%, And after 1500 hours, the electron emissivity decreases to about 50%. On the other hand, as shown in the characteristic (A) of FIG. 2, the color using the oxide cathode according to the present embodiment is reduced. The cathode ray tube has an electron emissivity of about 85% or more after 500 hours from the start of use and about 80% or less after 1000 hours or 1500 hours.
At the time when the time has elapsed, the electron emissivity is reduced to only about 70%. Obviously, the color cathode ray tube using the oxide cathode of this embodiment uses a known oxide cathode. As compared with a color cathode ray tube, it is possible to maintain excellent electron emission characteristics, that is, life characteristics over a long period of time.

The excellent electron emission characteristics of the oxide cathode in this embodiment as shown in the characteristic (A) of FIG. 2 are exhibited only when the oxide cathode is used for an electron gun of a color cathode ray tube. However, the present invention can be similarly exerted when used in another tube of the same type, for example, an electron gun of an image pickup tube.

[0033]

As described above, according to the oxide cathode of the present invention, a small amount of dysprosium oxide (Dy ₂ O ₃ ) powder containing particles having a particle size exceeding 4.5 μm is mixed in the electron emitting material layer. By using the electron emitting material layer, the electrical conductivity of the electron emitting material layer is increased, the electric resistance of the electron emitting material layer is reduced, and the generation of Joule heat when operating at a high current density is suppressed. As a result, the temperature of the electron emitting material layer is prevented from rising excessively, and the generation of free barium (Ba) is not significantly inhibited, so that even when the oxide cathode is operated at a high current density, it is stable for a long time. There is an effect that it is possible to maintain the improved electron emission characteristics.

Further, according to the oxide cathode of the present invention, there is an effect that a stable oxide cathode having high reliability can be obtained when displaying an image with high definition.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a main part of an embodiment of an oxide cathode according to the present invention.

FIG. 2 is a characteristic diagram showing a change with time of electron activity when an oxide cathode is operated.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 metal base 2 electron emitting material layer 3 dysprosium oxide (Dy ₂ O ₃ ) powder 4 sleeve 5 heater

Claims (3)

[Claims] 1. A sleeve made of a high melting point metal and fitted to one end of the sleeve, containing nickel (Ni) as a main component and a trace amount of a reducing metal element such as silicon (Si) or magnesium (Mg). A cap-shaped metal substrate, an electron-emitting substance layer made of a metal oxide of barium (Ba), strontium (Sr), and calcium (Ca) attached to the surface of the metal substrate, and a heater enclosed in the sleeve An oxide cathode comprising: a small amount of dysprosium oxide (Dy ₂ O ₃ ) powder containing particles having a particle size of more than 4.5 μm in the electron emitting material layer. 2. The method according to claim 1, wherein the trace amount of dysprosium oxide (Dy ₂
O ₃₎ powder, an oxide cathode according to claim 1 in which content is characterized in that in the range of 0.1 to 7.0 wt%. 3. The dysprosium oxide (Dy ₂ O ₃ )
2. The oxide cathode according to claim 1, wherein the powder has a particle size of more than 4.5 [mu] m and up to 20.0 [mu] m.