JPH08321250A - Electron tube equipped with cathode having electron emitting substance layer - Google Patents

Abstract

PURPOSE: To provide an electron tube equipped with a cathode having an electron emitting substance layer which has a heightned bonding strength between a cathode base metal and the electron emission substance layer and gives a stable electron emission characteristic for a long time even under a high current density condition. CONSTITUTION: The cathode of an electron tube has an electron emitting substance layer 15 on the surface of a cathode base metal 14, wherein the electron emitting substance layer 15 is made in a double layer structure consisting of an under-layer 16 and an over-layer 17; the under-layer 16 is made of oxides of alkali earth metal formed in contact with the surface of the cathode base metal 14, while the over-layer 17 is formed over the under-layer 16 and has such a composition that oxides of rare earth metal in the form of elliptical spheres of a mean particle size of 0.1μm to 5.0μm are dispersed in the oxides of alkali earth metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron tube having a cathode having an electron emitting material layer, and more particularly to a lower layer in which the electron emitting material layer is composed of an alkaline earth metal oxide and a rare earth metal oxide. The present invention relates to an electron tube provided with a cathode having an electron emitting material layer having a two-layer structure of an upper layer having a composition in which a predetermined amount is dispersed in an alkaline earth metal oxide.

[0002]

2. Description of the Related Art Generally, in a display electron tube such as a color picture tube or a data display tube, there is a demand for higher definition of an image displayed on the display surface with diversification of information and higher density of information. Has been done. As a display electron tube satisfying such demands, the cathode used in the electron tube must be capable of maintaining stable electron emission characteristics for a long time even in a high current density state.

By the way, several cathodes for electron tubes satisfying such demands have already been proposed. One of the proposals is disclosed in Japanese Patent Application Laid-Open No. 1-213935, and others. Those disclosed in JP-A-63-310535 and JP-A-63-310536.

Here, FIG. 5 shows the above-mentioned Japanese Patent Laid-Open No. 1-2139.
It is sectional drawing which shows the structure of the cathode of the electron tube disclosed by No. 35.

In FIG. 5, 30 is a bottomless cylindrical cathode sleeve, 31 is a cathode base metal, 32 is an electron emitting material layer,
Reference numeral 33 is a heater, and 34 is a composite oxide layer composed of an alkaline earth metal oxide and a rare earth metal oxide.

The cathode base metal 31 contains nickel (Ni) as a main component, and a small amount of silicon (S) is contained therein.
i) or a refractory metal material containing a reducing metal such as magnesium (Mg), and is provided so as to cover one end of the cylindrical cathode sleeve 30.
A heater 33 is arranged inside the 0 to form an indirectly heated cathode. On the cathode sleeve 31, a composite oxide layer 3 composed of an alkaline earth metal oxide and a rare earth metal oxide.
4 is deposited on the composite oxide layer 34, and the main component is an alkaline earth metal oxide containing at least barium (Ba) and additionally containing strontium (Sr) and / or calcium (Ca). Electron emitting material layer 3
2 is the one formed by deposition.

In the cathode of the electron tube having the above structure,
The composite oxide layer 34 formed of the alkaline earth metal oxide and the rare earth metal oxide deposited on the surface of the cathode sleeve 31 is heated during the activation process of the electron tube, or
When the heater 33 is heated during the normal operation of the electron tube, it is partially dissociated, and the rare earth metal therein, for example, scandium (S
c) becomes a scandium (Sc) atom and is released. At this time, the reducing metal such as silicon (Si) or magnesium (Mg) contained in the cathode sleeve 11 diffuses to the surface of the cathode sleeve 31, and these reducing metals are contained in the electron emitting material layer 32. reacted with (BaO) to produce barium (Ba) atom, at the same time, but to form barium silicate is the intermediate substance (BaSiO _3), the barium silicate (BaSiO ₃₎ is a rare earth metal atom, for example, scandium ( Sc) Decomposed by atoms. Also, when the cathode of this electron tube is operated in a high-density current state, the evaporation of barium (Ba) increases due to the Joule heat generated during this operation, but the evaporated barium (Ba) is oxidized by alkaline earth metal. Adhered to the complex oxide layer 34 composed of a rare earth metal oxide and a barium (B
The evaporation of a) is suppressed.

As described above, in the cathode of the electron tube according to the above-mentioned structure, the amount of the intermediate substance barium silicate (BaSiO ₃ ) formed is small and the amount of barium (Ba) evaporated is small, so that the high-current state For example, even when operated at a current density of 4 A / cm ³ or more, a reduction in emission current is small, and a long-life cathode of an electron tube can be reliably obtained.

Next, FIG. 6 shows a Japanese Patent Laid-Open No. 63-31053.
FIG. 5 is a cross-sectional view showing a configuration of a cathode of an electron tube disclosed in Japanese Patent Laid-Open No. 5 or JP-A-63-310536.

In FIG. 6, 40 is a bottomless cylindrical cathode sleeve, 41 is a cathode base metal, 42 is an electron emitting material layer,
Reference numeral 43 is a scandium oxide (Sc ₂ O ₃ ) crystal dispersed in the electron emitting material layer 22, and 44 is a heater.

The cathode base metal 41 contains nickel (Ni) as a main component, and a small amount of silicon (S) is contained therein.
i) such as a refractory metal material containing a reducing metal, and is provided so as to cover one end of the cylindrical cathode sleeve 40, and the heater 4 is provided inside the cathode sleeve 40.
4 are arranged to form an indirectly heated cathode. On the cathode sleeve 41, an electron emitting material layer 22 in which scandium oxide (Sc ₂ O ₃ ) crystal body 43 is dispersed in an alkaline earth metal oxide is deposited. In this case, the scandium oxide (Sc ₂ O ₃ ) crystal body 43 dispersed in the alkaline earth metal oxide is a dodecahedron (JP-A-63-3
10535) or a columnar polyhedron (JP-A-63-310).
No. 536), and the amount of dispersion thereof is selected to be 0.1% by weight to 20% by weight.

In the cathode of the electron tube having the above-mentioned structure, the dodecahedral or columnar polyhedral scandium oxide (Sc ₂ O ₃ ) 43 dispersed in the alkaline earth metal oxide of the electron emitting material layer 42 emits electrons. Barium (Ba) atoms released from the material layer 42 and donors in the electron emitting material layer 42 are not extinguished, and an intermediate material is formed near the interface between the cathode sleeve 21 and the electron emitting material layer 42. Since it has a function of preventing the formation of a certain complex oxide such as barium silicate (BaSiO ₃ ), it is possible to obtain a cathode of an electron tube capable of exhibiting stable electron emission characteristics for a long time. .

[0013]

Both of the known cathodes of electron tubes according to the above disclosure are capable of obtaining stable electron emission characteristics over a long period of time, but the cathode base metal 31 and the alkaline earth metal oxide. Force between the metal oxide and the complex oxide layer 34 made of rare earth metal oxide, and the alkaline earth metal oxide layer containing the cathode base metal 41 and the rare earth metal crystal 43 deposited on the surface thereof. No consideration is given to the bonding force with the (electron emitting material layer) 42.

Generally, when an electron emissive material layer is deposited on the cathode sleeve, the bonding force between the cathode sleeve and the electron emissive material layer is usually a small amount of silicon contained in the cathode sleeve. It is promoted by a silicon-based intermediate substance generated from (Si), and a relatively high bonding force is obtained.

However, as in the known cathode of an electron tube disclosed in Japanese Patent Laid-Open No. 1-213935, the cathode base metal 31 has an alkaline earth metal oxide and a rare earth metal oxide,
For example, when the complex oxide layer 34 made of scandium oxide (Sc ₂ O ₃ ) is in contact, or the scandium oxide (Sc ₂ O ₃ ) crystal 4 is attached to the cathode base metal 41.
3 is in contact with the alkaline earth metal oxide layer (electron emitting material layer) 42 in which 3 is dispersed, scandium (S
c) Atoms suppress the formation of silicon-based intermediate materials, and as a result, between the cathode base metal 31 and the complex oxide layer 34, or between the cathode base metal 41 and the alkaline earth metal oxide layer (electron emitting material). (Layer) 42, it becomes impossible to obtain a sufficient binding force, and when the cathode is operated,
Between the cathode base metal 31 and the complex oxide layer 34, or
Due to the difference in thermal expansion coefficient between the cathode base metal 41 and the alkaline earth metal oxide layer (electron emission material layer) 42, electrostatic force, or the like, the composite oxide layer 34 or the alkaline earth metal oxide layer (electron emission layer) There is a problem that the material layer) 42 is separated from the cathode base metals 31 and 41, respectively.

By the way, the inventors of the present invention have proposed an electron tube in which an alkaline earth metal oxide layer (electron emitting material layer) in which scandium oxide (Sc ₂ O ₃ ) powder is dispersed is directly formed on a cathode substrate metal. An experiment was conducted on the durability of the cathode, and it was found that the binding force between the cathode substrate metal and the alkaline earth metal oxide layer (electron emitting material layer) gradually decreased while the cathode was operating. Became. Then, the cathode base metal and the alkaline earth metal oxide layer (electron emitting material layer)
When the decrease in the binding force with is extremely large, the alkaline earth metal oxide layer (electron emitting material layer) begins to peel off from the cathode substrate metal, and the rate of such peeling is the alkaline earth metal. It was confirmed that the greater the content of the scandium (Sc) compound in the oxide layer (electron emitting material layer), the more remarkable it was.

Therefore, in order to solve such a problem, the present invention enhances the bonding force between the cathode base metal and the electron emitting material layer, and has stable electron emitting characteristics for a long time even in a high current density state. It is an object of the present invention to provide an electron tube provided with a cathode having an electron-emitting substance layer capable of obtaining the above.

[0018]

In order to achieve the above object, the present invention provides an electron tube provided with a cathode having an electron emitting substance layer on the surface of a cathode substrate metal, wherein the electron emitting substance layer is the cathode substrate. A lower layer having a composition of an alkaline earth metal oxide formed in contact with the surface of the metal, and an average particle size of 0.1 μm to 5.0 μ formed on the surface of the lower layer.
Means having a two-layer structure with an upper layer having a composition in which an elliptic spherical rare earth metal oxide of m is dispersed in an alkaline earth metal oxide.

In this case, according to the present invention, the dispersion amount of the rare earth metal oxide in the upper layer is distributed so as to change in a parabolic shape with respect to the thickness direction of the upper layer, and the average dispersion amount thereof. Is 0.01% to 10% by weight
Is provided as a secondary means.

[0020]

According to the above-mentioned means, the lower layer of the electron-emitting material layer having an alkaline earth metal oxide composition is deposited on the surface of the cathode substrate metal, and the alkaline earth metal is deposited on the surface of the lower layer. An upper layer of an electron emissive material layer having a composition in which a predetermined amount of a rare earth metal oxide, for example, scandium oxide (Sc ₂ O ₃ ) is dispersed in a metal oxide is deposited to form a rare earth metal oxide, for example, , Scandium oxide (Sc ₂ O ₃ ) is not in direct contact with the cathode base metal.

Since scandium oxide (Sc ₂ O ₃ ) does not come into direct contact with the cathode base metal, a small amount of silicon (Si) contained in the cathode base metal causes the formation of a silicon (Si) -based intermediate substance. The lower layer of the electron-emitting material layer whose composition is composed of the cathode base metal and the alkaline earth metal oxide deposited on it by the action of the generated silicon (Si) -based intermediate material without hindering the formation. During the operation of the cathode, the lower layer of the electron-emitting material layer composed of the alkaline earth metal oxide is not peeled off from the cathode base metal during the operation of the cathode.

According to the above secondary means, the scandium oxide (Sc ₂ O ₃ ) crystal has an average particle size of 0.1.
The ellipsoidal spherical shape of μm to 5.0 μm is selected to increase the surface area, and the amount of scandium oxide (Sc ₂ O ₃ ) dispersed in the alkaline earth metal oxide is adjusted to the electron emitting material layer. Since it is dispersed so as to form a parabola in the thickness direction of the upper layer of, the electron emission characteristic is improved while the content of scandium oxide (Sc ₂ O ₃ ) in the upper layer of the electron emitting substance layer is relatively small. Can be improved.

[0023]

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 a cathode having an electron emitting material layer according to the present invention, and showing an example of a color picture tube as the electron tube. is there.

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 which constitutes the color picture tube is
A panel unit 1 arranged on the front side, a neck unit 3 accommodating the electron gun 11, and a funnel unit 2 arranged between the panel unit 1 and the neck unit 3 and connecting the panel unit 1 and the neck unit 3 with each other. It consists of A fluorescent surface 4 is adhered to the inner surface of the panel portion 1, and a shadow mask 5 is arranged so as to face the fluorescent surface 4. Panel section 1 and funnel section 2
The magnetic shield 6 is provided on the inner side of the coupling portion of the deflection yoke 7 and the deflection yoke 7 is disposed on the outer side of the coupling portion of the funnel portion 2 and the neck portion 3.
Is arranged. Outside the neck portion 3, a magnet 8 for adjusting the purity, a magnet 9 for adjusting the center beam static convergence, and a magnet 10 for adjusting the side beam static convergence are arranged side by side, and three electron beams 12 projected from the electron gun 11 ( (Only one is shown in the figure), after being deflected in a predetermined direction by the deflection yoke 7, the fluorescent surface 4 is passed through the shadow mask 5.
In the pixel of the corresponding color.

Since the operation of the color picture 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 picture tube, the description of the image display operation of this color picture tube is omitted. .

Next, FIG. 2 is an enlarged sectional view showing an example of the constitution of a cathode having an electron emitting material layer used in the electron gun 11 of the color picture tube shown in FIG.

In FIG. 2, 13 is a bottomless cylindrical cathode sleeve, 14 is a cap-shaped cathode base metal, 15 is an electron emitting material layer having a two-layer structure, and 16 is an electron having an alkaline earth metal oxide composition. A lower layer of the emissive material layer, 17 is an upper layer of the electron emissive material layer having a composition in which a rare earth metal oxide is dispersed in an alkaline earth metal oxide, and 18 is a heater.

The cylindrical cathode sleeve 13 is made of a refractory metal material, and the heater 18 is arranged inside the cathode sleeve 13 to form an indirectly heated cathode. The cap-shaped cathode base metal 14 is composed of a refractory metal material containing nickel (Ni) as a main component and a small amount of a reducing metal such as silicon (Si) or magnesium (Mg) in it. , Is provided so as to seal one end of the cathode sleeve 13. The electron-emitting material layer 15 having a two-layer structure is the cathode metal substrate 1
No. 4, which is deposited on the surface of No. 4 and has an alkaline earth metal oxide composition, and an upper layer 17 having a composition in which a predetermined amount of a rare earth metal oxide is dispersed in the alkaline earth metal oxide. It consists of In this case, barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), calcium carbonate (CaC) are used as the alkaline earth metal oxides constituting the lower layer 16 of the electron emitting material layer.
O ₃ ), and the like, and the alkaline earth metal oxides constituting the upper layer 17 of the electron emitting material layer include barium carbonate (BaCO ₃ ), strontium carbonate (SrC).
O _3), there is such as calcium carbonate (CaCO _3),
Scandium oxide (Sc ₂ O ₃ ) or the like is used as the rare earth metal oxide dispersed therein.

In the present embodiment, the lower layer 16 of the electron emitting material layer is formed of an alkaline earth containing barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), and calcium carbonate (CaCO ₃ ). composed of metalloid oxides, also, the upper layer 17, barium carbonate (BaCO ₃₎ of the electron emissive material layer, strontium carbonate (Sr
CO ₃ ), calcium carbonate (CaCO ₃ ) in alkaline earth metal oxides, 0.0 per cathode
5% by weight of scandium oxide (Sc ₂ O ₃ ) is dispersed and configured. In this case, such scandium oxide (S
c ₂ O ₃ ) is an ellipsoidal crystal having an average particle size of about 0.5 μm, and contains 80% by weight or more of pure scandium oxide (Sc ₂ O ₃ ). As shown in the distribution state of scandium oxide (Sc ₂ O ₃ ), the distribution is such that a parabola is drawn in the thickness direction of the upper layer 17 of the electron emitting material layer. The elliptic spherical crystal structure of scandium oxide (Sc ₂ O ₃ ) has barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), and calcium carbonate (Ca
CO ₃ ), which is almost the same as the needle-shaped crystal structure, and the average particle size of about 0.5 μm in the scandium oxide (Sc ₂ O ₃ ) crystal is the barium carbonate (BaCO).
₃ ), strontium carbonate (SrCO ₃ ) and calcium carbonate (CaCO ₃ ) crystals are selected to be about 1/10 of the average particle size. Further, the total content of scandium oxide (Sc ₂ O ₃ ) in the electron emitting material layer 15 is selected to be in the range of 0.01% by weight to 10% by weight.

Electron gun 1 of color picture tube according to the above construction
The cathode having the electron emitting material layer used in 1 is manufactured by the following procedure.

First, barium carbonate (BaCO ₃ ),
To crystalline powders of strontium carbonate (SrCO ₃ ) and calcium carbonate (CaCO ₃ ) are added nitrocellulose lacquer and butyl acetate, followed by rolling and mixing.
Prepare a first slurry. In addition, barium carbonate (BaCO ₃ ) and strontium carbonate (SrC
O ₃ ), calcium carbonate (CaCO ₃ ) crystal powder, and 0.1% by weight of scandium oxide (Sc) per cathode.
₂ O ₃ ) crystal powder was dispersed, and nitrocellulose lacquer and butyl acetate were also added and rolling mixed,
Prepare a second slurry. In addition, barium carbonate (BaCO ₃ ) and strontium carbonate (SrC
O ₃ ), calcium carbonate (CaCO ₃ ) crystal powder, and 0.03% by weight of scandium oxide (S
To a dispersion of the crystal powder of c ₂ O ₃ ) is also added nitrocellulose lacquer and butyl acetate, followed by rolling and mixing to prepare a third slurry.

Then, the first slurry is applied to the cathode base metal 14 provided so as to seal one end of the cathode sleeve 13 by a spray method to a thickness of about 10 μm, and an alkaline earth metal oxide is applied. The lower layer 16 of the electron emitting material layer having the composition is formed.

Subsequently, the second slurry is applied on the lower layer 16 of the electron emitting material layer by a spraying method to a thickness of about 40 μm, and the third slurry is further sprayed thereon. Then, the upper layer 17 of the electron emitting material layer is formed by the method to form the electron emitting material layer 15 having a two-layer structure.

Next, in the vacuum evacuation process of the color picture tube,
Then, the electron emitting material layer 15 is heated by the heater 18.
However, the barium carbonate (B
aCO₃), Strontium carbonate (SrCO₃),
Calcium carbonate (CaCO ₃) Is thermally decomposed and oxidized
Barium (BaO), strontium oxide (SrO),
Calcium oxide (CaO) is formed, and then electron emission
Apply the spray layer 15 in an atmosphere of 900 ° C to 1100 ° C.
It is activated by heating to form a cathode with an electron emissive material layer.
It is what makes it happen.

By the way, in the case of manufacturing the cathode having the electron emitting material layer of the present embodiment, the scandium oxide (Sc ₂ O ₃ ) dispersed in the second and third slurries is an ellipsoidal crystal. In addition, since the average grain size of the crystal is selected to be about 0.5 μm, the dispersion stability in the second and third slurries is, for example, 20 l (liter) in the first volume tank. And put the second slurry in
Also in the second capacity tank of 20 l (liter) the third
Slurry was placed, and the time the spraying is started in these slurries, in a working end that has elapsed since that time about 8 hours, scandium oxide in the second and third slurry (Sc ₂ O ₃₎ The difference in the amount of dispersion is only about 0.01% by weight, exhibiting extremely high dispersion stability.

Next, FIG. 4 is a characteristic diagram showing the relative ratio between the operating time and the maximum anode current in the color picture tube in which the cathode having the electron emitting material layer of this embodiment is mounted, and a known cathode is mounted. It shows a comparison with the characteristics of a color picture tube.

In FIG. 4, the vertical axis represents the relative ratio of the maximum anode current, the horizontal axis represents the operating time, the curve a is the characteristics of the cathode having the electron emitting material layer of this embodiment, and the curve b is the electron emission. The characteristics of the cathode with a known electron emissive material layer with only the upper layer of the material layer, curve c, are scandium oxide (S
₃ shows characteristics of a cathode having a known electron emissive material layer containing no c ₂ O ₃ ).

As shown in FIG. 3, the characteristics of the cathode having the electron emitting material layer of this example (curve a) and the cathode having the known electron emitting material layer containing no scandium oxide (Sc ₂ O ₃ ). Comparing with the characteristics (curve c) of Example 1, the cathode of this example has a higher relative ratio of the maximum anode current at all operating times. Therefore, the cathode of this example has much longer life characteristics. It is clear that Further, the characteristic of the cathode having the electron emitting material layer of this embodiment (curve a) is compared with the characteristic of the cathode having the known electron emitting material layer having only the upper layer of the electron emitting material layer (curve b). In the initial operating time, the known cathode has a higher relative ratio of the maximum anode current and exhibits excellent characteristics. However, when the operating time exceeds 2000 hours, the known cathode rapidly increases. While the relative ratio of the maximum anode current becomes low and the characteristics are deteriorated, the cathode of the present embodiment does not cause the characteristics to be deteriorated even when the operating time exceeds 2000 hours. .

Here, in the present embodiment, as described above, the total amount of scandium oxide (Sc ₂ O ₃ ) contained in the electron emitting material layer 15 is in the range of 0.01% by weight to 10% by weight. As shown in, the scandium oxide (Sc
₂ O ₃ ) dispersion amount is selected. The reason for this is that if the total amount of scandium oxide (Sc ₂ O ₃ ) is less than 0.01% by weight, the function due to the electron emitting material layer 15 having a two-layer structure cannot be sufficiently exhibited, while scandium oxide (Sc
_When the total amount of ₂ O ₃ ) exceeds 10% by weight, when the color picture tube is operated, as shown by the curve b in FIG. This is because the characteristics are deteriorated. When the total amount of scandium oxide (Sc ₂ O ₃ ) exceeds 10% by weight, the cause of such rapid deterioration of characteristics is that the electron emitting material layer 15 is separated from the cathode base metal 14. Conceivable.

As described above, in the cathode having the electron emitting material layer used in the electron gun 11 of the color picture tube according to the present embodiment, scandium oxide (Sc) is formed on the lower layer 16 of the electron emitting material layer in contact with the cathode base metal 14. ₂ O ₃ ) is not present, the production of silicon (Si) -based intermediate substances, such as barium silicate (BaSiO ₃ ), which is formed from a small amount of silicon (Si) contained in the cathode base metal 14, is prevented. Absent. The barium silicate (BaSiO ₃ ) generated here is bonded to the cathode base metal 14 and the lower layer 16 of the electron emitting material layer having a composition of the alkaline earth metal oxide deposited on the cathode base metal 14. Since the lower layer 16 of the electron emitting material layer is not separated from the cathode base metal 14 during the operation of the color picture tube, the electron emitting material operates stably even in a high current density state and has a long life. A cathode with a material layer can be obtained.

The cathode having the electron emitting material layer used in the electron gun 11 of the color picture tube according to the present embodiment is a scandium oxide (Sc ₂ O ₃ ) crystal dispersed in the upper layer 17 of the electron emitting material layer. , An ellipsoidal shape with a large surface area and an average particle size of about 0.5 μm is used.
Moreover, the dispersion state of scandium oxide (Sc ₂ O ₃ )
Since they are dispersed so as to form a parabola in the thickness direction of the upper layer 17 of the electron emitting material layer, the content of scandium oxide (Sc ₂ O ₃ ) in each cathode is reduced and the electron emitting characteristics are improved. Can be improved.

In the above-mentioned embodiments, the case where the electron tube is a color picture tube has been described as an example, but the symmetrical electron tube of the present invention is not limited to the color picture tube, but a data display tube. Needless to say, the present invention may be applied to other display electron tubes such as the above, and may be applied to other electron tubes other than the display electron tube.

In the above-mentioned embodiments, the case where the rare earth metal oxide dispersed in the upper layer 17 of the electron emitting material layer is scandium oxide (Sc ₂ O ₃ ) has been described as an example. The rare earth metal oxide according to the present invention is not limited to scandium oxide (Sc ₂ O ₃ ), but other rare earth metal oxides such as yttrium oxide (Y ₂ O ₃ ), cerium oxide (Ce ₂ O ₅ ), and barium. Scandate (Ba
₂ S ₂ O ₅ ) or a complex oxide (BaY ₂ O ₄ ) containing an alkaline earth metal such as barium (Ba) or scandium (Sc), (Sr ₂ Sc ₄ O ₈ ), (Ba ₃
Even with Y ₄ O ₉ ), (CaSc ₄ O ₉ ), and (Ba ₃ Ce ₄ O ₉ ), it is possible to obtain the same action and effect as when scandium oxide (Sc ₂ O ₃ ) is used.

Further, in the above-mentioned embodiments, the case where the average particle diameter of scandium oxide (Sc ₂ O ₃ ) dispersed in the upper layer 17 of the electron emitting material layer is about 0.5 μm is described as an example. However, the average particle size of scandium oxide (Sc ₂ O ₃ ) according to the present invention is not limited to about 0.5 μm, and similar effects can be obtained within the range of 0.1 μm to 5.0 μm. I have confirmed this experimentally.

[0047]

As described above in detail, according to the present invention, the lower layer of the electron emitting material layer having the composition of the alkaline earth metal oxide is deposited on the surface of the cathode substrate metal, On the surface of the lower layer, a predetermined amount of rare earth metal oxide, for example, scandium oxide (Sc ₂
The upper layer of the electron emitting material layer having a composition in which O ₃ ) is dispersed is formed by deposition so that scandium oxide (Sc ₂ O ₃ ) is not in direct contact with the cathode base metal. The generation of the silicon (Si) -based intermediate material based on the trace amount of silicon (Si) contained in is not hindered, and the action of the generated silicon (Si) -based intermediate material causes the cathode base metal and the metal The adhesion with the lower layer of the electron-emitting material layer having the composition of the deposited alkaline earth metal oxide is promoted, and the alkaline earth metal oxide layer is separated from the cathode base metal during the operation of the cathode. There is an effect that there is no

According to the present invention, the scandium oxide (Sc) crystal has an average particle size of 0.1 μm to 5.
Select an ellipsoidal spherical shape of 0 μm to increase its surface area and make the amount of scandium (Sc) dispersed in the alkaline earth metal oxide relative to the thickness direction of the upper layer of the electron-emitting substance layer. Since it is dispersed in a parabolic shape, scandium oxide (S
There is an effect that the electron emission characteristics can be improved while the content of c) is relatively small.

[Brief description of drawings]

FIG. 1 is a schematic sectional configuration diagram showing an embodiment of a color picture tube including a cathode having an electron emitting material layer according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing an example of the configuration of a cathode having an electron emitting material layer used in the electron gun of the color picture tube shown in FIG.

FIG. 3 is an explanatory diagram showing an example of a dispersed state of scandium oxide in an upper layer of an electron emitting material layer in the embodiment shown in FIG.

FIG. 4 is a characteristic diagram showing a relative ratio between an operating time and a maximum anode current in a color picture tube in which a cathode having an electron emitting material layer of the present embodiment is mounted.

FIG. 5 is a cross-sectional view showing an example of the configuration of a cathode having a known electron emitting material layer.

FIG. 6 is a cross-sectional view showing another example of the configuration of a cathode having a known electron emitting material layer.

[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 Magnet for Adjusting Purity 9 Center Beam Static Convergence Adjusting Magnet 10 Side Beam Static Convergence Adjusting Magnet 11 Electron Gun 12 Electron Beam 13 Cathode sleeve 14 Cathode substrate metal 15 Electron emitting material layer 16 Lower layer of electron emitting material layer 17 Upper layer of electron emitting material layer 18 Heater

Claims (4)

[Claims] 1. In an electron tube provided with a cathode having an electron emitting substance layer on the surface of a cathode substrate metal, the electron emitting substance layer comprises an alkaline earth metal oxide formed in contact with the surface of the cathode substrate metal. A lower layer having a composition, and an average particle size of 0.1 μm to 5.0 μ formed on the surface of the lower layer.
An electron tube provided with a cathode having an electron emitting material layer, which has a two-layer structure of an upper layer having a composition in which an elliptic spherical rare earth metal oxide of m is dispersed in an alkaline earth metal oxide. . 2. The dispersion amount of the rare earth metal oxide in the upper layer is dispersed so as to change in a parabolic shape in the thickness direction of the upper layer, and the average dispersion amount is 0.01. The electron tube having a cathode having an electron emitting material layer according to claim 1, wherein the electron tube has a content of 10 wt% to 10 wt%. 3. The rare earth metal oxide in the upper layer is scandium oxide (Sc ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (Ce ₂ O ₅ ), barium scandate (Ba ₂ S _2). An electron tube provided with a cathode having an electron emitting material layer according to any one of claims 1 to 2, which is at least one of O ₅ ). 4. The rare earth metal oxide in the upper layer is a complex oxide (BaY ₂ O ₄ ), (Sr ₂ Sc ₄ O ₈ ), (Ba ₃ ) such as barium (Ba) or scandium (Sc).
Y ₄ O ₉ ), (CaSc ₄ O ₉ ), and (Ba ₃ Ce ₄ O ₉ ), which is at least one of the electron-emitting substance layers according to any one of claims 1 to 2. An electron tube with a cathode having.