JPH08236007A - Electron tube with oxide cathode - Google Patents

Abstract

(57) [Summary] [Object] To provide an electron tube provided with an oxide cathode capable of maintaining stable electron emission characteristics at a high current density for a long time. [Structure] A cap-shaped base metal 14 containing nickel (Ni) as a main component and containing a trace amount of reducing metals such as magnesium (Mg), silicon (Si), and zirconium (Zr).
And an electron emission material layer 15 provided on the base metal 14 and made of a metal oxide of barium (Ba), strontium (Sr), and calcium (Ca). The layer 15 has a mixing amount of 0.2 to 3.0% by weight and an average particle size of 0.5 to 2
0 μm of aluminum oxide (Al ₂ O ₃ ) powder 16 is mixed. This aluminum oxide (Al ₂ O ₃ ) powder 1
By mixing No. 6, the electric resistance of the electron emission material layer 15 at high temperature is reduced, and stable electron emission characteristics can be exhibited at a high current density for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron tube provided with an oxide cathode, and more particularly, it shows stable electron emission characteristics of high current density for a long time, and has a high-definition color cathode ray tube, a large color cathode ray tube or an image pickup tube. The present invention relates to an electron tube having an oxide cathode suitable for use in.

[0002]

2. Description of the Related Art Conventionally, an oxide cathode in an electron tube contains nickel (Ni) as a main component, and magnesium (Mg) and silicon (Si) are contained therein, as disclosed in JP-A-58-154130. ), Zirconium (Z
a base metal containing a trace amount of a reducing metal such as r), and an electron emission material layer provided on the base metal and made of a metal oxide of barium (Ba), strontium (Sr), and calcium (Ca), And a heater for heating.

The known oxide cathode having the above-mentioned structure is comparatively long and relatively long as the display screen of an electron tube using such an oxide cathode, in particular, a color cathode ray tube, an image pickup tube or the like is made finer. It has stable electron emission characteristics with high current density.

[0004]

However, when the known oxide cathode is constructed so as to obtain the electron emission characteristics of high current density, the electron emission of electrons is performed when the electron emission is performed at high current density. Joule heat is generated in the material layer, and the temperature of the electron emitting material layer rises, so that the electron emitting material in the electron emitting material layer is melted or evaporated. As a result, the known oxide cathode has a high electric resistance in the electron emission material layer, and the high electric resistance hinders the current flowing in the electron emission material layer, resulting in deterioration of the electron emission characteristic of high current density. I have a problem.

The present invention solves the above-mentioned problems.
An object thereof is to provide an electron tube provided with an oxide cathode capable of maintaining stable electron emission characteristics with high current density for a long time.

[0006]

In order to achieve the above object, the present invention provides a substrate containing nickel (Ni) as a main component and a trace amount of a reducing metal such as magnesium (Mg) or silicon (Si). A metal, provided on the base metal,
In an electron tube provided with an oxide cathode having an electron emitting material layer made of oxides of barium (Ba), strontium (Sr), and calcium (Ca), a trace amount of aluminum oxide (Al ₂ O) is contained in the electron emitting material layer. ₃ ) A means for mixing powders is provided.

According to the above means, the aluminum oxide (Al ₂ O ₃ ) powder mixed in the electron emission material layer is
The mixing amount is in the range of 0.2 to 3.0% by weight, and the average particle size is selected in the range of 0.5 to 20 μm.

[0008]

According to the above-mentioned means, a trace amount of aluminum oxide (Al) is contained in the electron emission material layer composed of oxides of barium (Ba), strontium (Sr) and calcium (Ca).
_{Since 2} O ₃ ) powder is mixed, a donor of aluminum oxide (Al ₂ O ₃ ) is formed in the electron emission material layer. Then, the donor formed in the electron-emitting substance layer works to suppress an increase in the electric resistance of the electron-emitting substance layer, so that the current generated in the electron-emitting substance layer flows relatively easily, and the electron Electron emission characteristics with high current density can be exhibited without impeding the electron emission function from the emission material layer.

In this case, the aluminum oxide (Al ₂ O ₃ ) powder mixed in the electron emission material layer has an average particle size of 0.5.
It has been confirmed that the formation of the donor is promoted when it is in the range of 0.2 to 20 μm, and the content is 0.2% by weight.
It was confirmed that high current density electron emission characteristics can be exhibited by mixing the above amounts. However, when the amount of the mixed aluminum oxide (Al ₂ O ₃ ) powder is 3.0% by weight or more, the initial emission is lowered and the adverse effect is caused.
The amount of ₂ O ₃ ) powder should be selected in the range of 0.2 to 3.0% by weight.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of an electron tube provided with an oxide cathode according to the present invention, showing an example of a color cathode ray tube as the electron tube.

In FIG. 1, 1 is a panel portion, 2 is a funnel portion, 3 is a neck portion, 4 is a fluorescent surface, 5 is a shadow mask, 6 is a magnetic shield, 7 is a deflection yoke, 8 is a magnet for adjusting the purity, Reference numeral 9 is a center beam static convergence adjustment magnet, 10 is a side beam static convergence adjustment magnet, 11 is an electron gun, and 12 is an electron beam.

The tube body constituting the color cathode ray tube is arranged in the front side, the panel section 1, the neck section 3 accommodating the electron gun 11, and the intermediate section between the panel section 1 and the neck section 3. It consists of the funnel section 2. A fluorescent surface 4 is arranged and formed on the inner surface of the panel portion 1, and a shadow mask 5 is arranged so as to face the fluorescent surface 4. A magnetic shield 6 is disposed inside the coupling portion between the panel portion 1 and the funnel portion 2, and a deflection yoke 7 is disposed outside the coupling portion between the funnel portion 2 and the neck portion 3. Neck 3
A magnet 8 for adjusting the center beam static convergence, a magnet 9 for adjusting the side beam static convergence and a magnet 10 for adjusting the side beam static convergence are arranged side by side on the outer side of each of the three electron beams 12 emitted from the electron gun 11 (see FIG. (Only one is shown) is deflected in a predetermined direction by the deflection yoke 7 and then reaches the corresponding pixel on the fluorescent surface 4 through the shadow mask 5.

Since the operation of the color cathode ray tube having the above-mentioned structure, that is, the image display operation is exactly the same as the image display operation of the known color cathode ray tube, the description of the image display operation of this color cathode ray tube will be omitted.

FIG. 2 is an enlarged sectional view showing the structure of an embodiment of an oxide cathode used in the electron gun 11 of the electron tube shown in FIG. 1, that is, the color cathode ray tube.

In FIG. 2, 13 is a cylindrical cathode sleeve made of a refractory metal material such as nickel (Ni), 14 is a main component of nickel (Ni), and a trace amount of magnesium (Mg), silicon ( Si), zirconium (Zr) and the like base metal containing a reducing metal, 1
5 is an electron emission material layer made of metal oxides of barium (Ba), strontium (Sr), and calcium (Ca),
Reference numeral 16 is a small amount of aluminum oxide (Al ₂ O ₃ ) powder mixed in the electron emission material layer 15, and 17 is a heater loaded in the cylindrical cathode sleeve 13.

The tubular cathode sleeve 13 has one end fitted with the opening of the cap-shaped base metal 14, and the heater 17 is housed and loaded therein. An electron emission material layer 15 is formed on the top surface of the hat-shaped base metal 14, and a small amount of aluminum oxide (Al ₂ O ₃ ) is deposited in the electron emission material layer 15.
The powder 16 is mixed.

In the oxide cathode having the above structure,
The electron emission material layer 15 is deposited and formed as follows, for example.

A mixed solution of barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), and calcium carbonate (CaCO ₃ ) had an average particle size of 3.0 μm and contained 1.0 wt. % Aluminum oxide (Al ₂ O ₃ ) powder 16 having a purity of 99.99% is mixed to form a suspension (suspension). The electron emission material layer 15 is deposited on the top surface of the base metal 14 to a thickness of about 70 mm.

When the electron emission material layer 15 having such a structure is used, when electron emission with a high current density is performed in the electron emission material layer 15, Joule heat is generated in the electron emission material layer 15 and As a result, the temperature of the electron emission material layer 15 rises. When the temperature of the electron emission material layer 15 rises, barium (Ba) in the electron emission material layer 15 melts or evaporates, and the electric resistance of the electron emission material layer 15 increases. At this time, the aluminum oxide (Al
_{The 2} O ₃ ) powder 16 forms a donor, and the donor acts to suppress the increased electric resistance of the electron emission material layer 15, so that the current generated in the electron emission material layer 15 flows easily, and at the same time, The amount of electrons emitted from the electron emission material layer 15 also increases, and the electron emission material layer 15 exhibits high current density electron emission characteristics.

Here, FIG. 3 is a characteristic diagram showing the time variation of the electron emission capability in the electron tube having the oxide cathode of the present embodiment and the electron tube having the known oxide cathode.

In FIG. 3, the vertical axis represents the electron emission capacity which is a relative value of the electron emission capacity at each time with respect to the initial electron emission capacity, and the horizontal axis is the operation time which is the time elapsed in kilohours (KHr). Further, (A) shows the characteristics of the oxide cathode of this embodiment, and (B) shows the characteristics of the known oxide cathode.

According to the characteristic diagram shown in FIG. 3, the electron tube provided with the known oxide cathode shows that the electron emission capability of the oxide cathode increases as the operating time elapses, as shown in characteristic (B). Shows that the degree of dip is relatively larger than that of the initial one, whereas the electron tube provided with the oxide cathode of the present example shows that the operating time elapses as shown in the characteristic (A). Therefore, the electron emission capability of the oxide cathode is relatively lower than that of the initial one. For example, comparing the electron emission capacities of the oxide cathode when 10 KHr has passed from the initial time with respect to the characteristics (A) and (B), the electron tube with the known oxide cathode has an initial electron emission capacity (relative Value 1
In contrast, the electron tube with the oxide cathode of this example has an electron emission capacity (relative value of 100) which is about 30% or more lower than that of (00). 20
% (Relative value of about 67), and the same tendency appears at times other than 10 KHr since the initial time. As described above, the electron tube provided with the oxide cathode of the present example shows less deterioration in the electron emission capability with the lapse of operating time and exhibits excellent life characteristics as compared with the electron tube provided with the known oxide cathode. It can be said to be a thing.

In the above-mentioned embodiment, the aluminum oxide (Al
_{The 2} O ₃ ) powder 16 has been described by taking the case where the average particle diameter is 3.0 μm and the mixing amount is 1.0% by weight as an example.
The average particle size and the mixing amount of the aluminum oxide (Al ₂ O ₃ ) powder 16 mixed in the above are not limited to this example, and other average particle sizes and mixing amounts may be selected. Of course.

That is, if the average particle diameter of the aluminum oxide (Al ₂ O ₃ ) powder 16 mixed in the electron emitting material layer 15 is within the range of 0.5 to 20 μm, the inside of the electron emitting material layer 15 is It has been confirmed that the formation of the donor similar to that in the above case is promoted, and the electron emission material layer 15 is also formed.
It has been confirmed that the electron emission characteristic of high current density can be exhibited by setting the mixing amount of the aluminum oxide (Al ₂ O ₃ ) powder 16 mixed in the above to 0.2 wt% or more. However, aluminum oxide (Al
₂ O ₃ ) When the amount of powder 16 mixed is 3.0 wt% or more,
Since the initial emission is lowered, the amount of the aluminum oxide (Al ₂ O ₃ ) powder 16 mixed in the electron emission material layer 15 is selected to be within the range of 0.2 to 3.0 wt%. are doing.

Further, in the above-described embodiment, the example in which the electron tube is a color cathode ray tube has been described, but the electron tube according to the present invention is not limited to the color cathode ray tube, and another electron tube, for example, an image pickup tube. Of course, the same can be applied to the above.

Further, in the above-mentioned embodiment, when the electron emission material layer 15 is formed by coating on the top surface of the cap-shaped base metal 14, an example of applying a suspension by a spray method is given. As described above, the formation of the electron emission material layer 15 according to the present invention is performed by using a suspension.
The present invention is not limited to the case of applying and forming by using a spray method, and such a suspension (suspension) may be formed into a paste and formed by a printing method.

As described above, according to this embodiment, a small amount, that is, 0.2 to 3.0% by weight of aluminum oxide (Al ₂ O ₃ ) powder 16 is mixed in the electron emission material layer 15 to generate an electron emission material. A donor of aluminum oxide (Al ₂ O ₃ ) is formed in the emissive material layer 15. Therefore, at the time of high-density electron emission, Joule heat is generated in the electron-emitting substance layer 15, and the temperature of the electron-emitting substance layer 15 rises before the electric resistance of the electron-emitting substance layer 15 increases, so that aluminum oxide is emitted. Since the donor of (Al ₂ O ₃ ) works to suppress the increase in the electric resistance of the electron-emitting substance layer 15, the current generated in the electron-emitting substance flows relatively easily, and the electric current from the electron-emitting substance layer 15 is generated. It is possible to exhibit high current density electron emission characteristics for a long time without disturbing the electron emission function.

[0029]

As described above, according to the present invention,
Since a small amount of aluminum oxide (Al ₂ O ₃ ) powder is mixed in the electron emission material layer made of oxides of barium (Ba), strontium (Sr), and calcium (Ca), the electron emission material layer A donor of aluminum oxide (Al ₂ O ₃ ) is formed therein. The donor formed in the electron emission material layer suppresses an increase in the electric resistance of the electron emission material layer when the temperature of the electron emission material layer rises due to the Joule heat generated in the electron emission material layer. Current flows in the electron-emitting material relatively easily, so that the electron-emitting characteristics of high current density can be exerted for a long time without hindering the electron-emitting function from the electron-emitting material layer. The effect is that you can

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram showing an embodiment of a color CRT equipped with an oxide cathode according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing the configuration of an embodiment of an oxide cathode used in the electron gun of the color CRT shown in FIG.

FIG. 3 is a characteristic diagram showing a temporal variation of electron emission capability in an electron tube provided with an oxide cathode of the present example and an electron tube provided with a known oxide cathode.

[Explanation of symbols]

1 Panel Part 2 Funnel Part 3 Neck Part 4 Fluorescent Surface 5 Shadow Mask 6 Magnetic Shield 7 Deflection Yoke 8 Purity Adjustment Magnet 9 Center Beam Static Convergence Adjustment Magnet 10 Side Beam Static Convergence Adjustment Magnet 11 Electron Gun 12 Electron Beam 13 Cylindrical cathode sleeve 14 Hat-shaped base metal 15 Electron emission material layer 16 Aluminum oxide (Al ₂ O ₃ ) powder 17 Heater

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihisa Miyama 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Device Division

Claims (3)

[Claims] 1. A base metal mainly containing nickel (Ni) and containing a trace amount of a reducing metal such as magnesium (Mg) or silicon (Si); and a base metal provided on the base metal.
In an electron tube provided with an oxide cathode having an electron emitting material layer made of oxides of barium (Ba), strontium (Sr), and calcium (Ca), a trace amount of aluminum oxide (Al ₂ O) is contained in the electron emitting material layer. ₃ ) An electron tube equipped with an oxide cathode characterized by mixing powders. 2. The amount of aluminum oxide (Al ₂ O ₃ ) powder mixed in the electron emission material layer is in the range of 0.2 to 3.0 wt%.
An electron tube comprising the oxide cathode according to 1. 3. The aluminum oxide (Al ₂ O ₃ ) powder mixed in the electron emission material layer has an average particle size in the range of 0.5 to 20 μm. An electron tube provided with the oxide cathode according to any one of the claims.