JP2000200541A - Cathode assembly - Google Patents

Abstract

(57) [Summary] [Purpose] While maintaining excellent high-density current operation characteristics,
Provided is a cathode structure which prevents a decrease in the amount of electron emission and can cope with an increase in the size and the brightness of a cathode ray tube. The cathode structure includes a cathode sleeve, a cathode base fitted to one end of the cathode sleeve, and an electron emitting material layer formed on the top surface of the cathode base. material layer 23 is located on the top side of the cathode substrate 22, a lower layer 23 ₁ formed by the alkaline earth metal oxide particles of polyhedral shape, located on the lower layer 23 _1, the rare earth metal oxide inclusive consist upper layer 23 ₂ formed by the alkaline earth metal oxide particles of needle shape, the thickness of the lower layer 23 ₁ is in the range of 5 to 37% of the thickness of the electron emitting material layer 23 It has been chosen to be.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode structure and, more particularly, to a cathode structure in which an electron emission material layer of a cathode is formed of a lower layer and an upper layer.
The present invention relates to a cathode ray tube which has a layer structure and obtains a cathode capable of maintaining high-density current operation characteristics for a long period of time by selecting the shape of particles forming the lower layer and the upper layer or the thickness of those layers.

[0002]

2. Description of the Related Art Generally, in a cathode ray tube, such as a color picture tube for displaying a received image of a television broadcast or a data display tube for displaying data image information obtained by an information processing device such as a personal computer, data to be displayed is required. With the diversification and high density of information and the like, it has been demanded to display a high-definition image on a display image to be displayed. As a cathode ray tube satisfying such demands, the cathode structure includes:
It is necessary to use a cathode structure capable of maintaining stable electron emission characteristics for a long time in a high current density state. As one of such cathode structures, a cathode structure disclosed in JP-A-5-12983 is known. .

Here, FIG.
FIG. 4 is a cross-sectional view illustrating a cathode structure disclosed in No. 3;

In FIG. 6, reference numeral 61 denotes a cylindrical cathode sleeve, 62 denotes a cap-shaped cathode base, 63 denotes an electron emitting material layer, 63
₁ the lower layer of the electron emitting material layer 63, 63 ₂ the upper layer of the electron emitting material layer 63, 64 is a heater.

[0005] The cylindrical cathode sleeve 61 is made of a material containing a high melting point metal, for example, nickel (Ni) as a main component, and a small amount of a reducing metal such as silicon (Si) or magnesium (Mg) therein. Become. Cap-shaped cathode base 62
Is made of the same material as the cathode sleeve 61 and is fitted to one end of the cathode sleeve 61. The electron emitting material layer 63 is made of an alkaline earth metal oxide, and includes a lower layer 63 ₁ formed on the top surface of the cathode base 62 and a rare earth metal oxide such as barium scandate (Ba ₂ Sc ₂ O). ₅₎ a composite oxide laden alkaline earth metal oxides such as, a two-layer structure by an upper layer 63 _2, which is deposited and formed on the lower layer 63 _1. The heater 64 is supported and fixed in the cathode sleeve 61 to form an indirectly heated cathode.

In the case of forming the electron emitting material layer 63 having the above-described structure, first, a lower (first) layer made of an alkaline earth metal carbonate is formed on the top surface (surface) of the cathode substrate 62 by depositing. Next, barium scandate (Ba) was placed on the lower layer.
_An upper (second) layer made of an alkaline earth metal carbonate containing a rare earth metal oxide such as ₂ Sc ₂ O ₅ ) is formed by deposition, and then, during a heat treatment in a cathode ray tube manufacturing process,
The thermal decomposition of the lower (first) layer and the upper (second) layer changes the alkaline earth metal carbonates of the lower (first) layer and the upper (second) layer into alkaline earth metal oxides, respectively. It is to form a lower layer 63 ₁ and the upper layer 63 _2.

According to the cathode structure having the above-described structure, an alkaline earth metal containing a rare earth metal oxide such as barium scandate (Ba ₂ Sc ₂ O ₅ ) formed on the electron emission surface side of the electron emission material layer 63. Upper layer 63 made of oxide
_2, the free barium produced by reducing metal silicon (Si) and magnesium (Mg) or the like in the cathode substrate 62 (Ba) is constrained to the upper layer 63 in the _2, free barium in the electron emissive material layer 63 (Ba) is maintained in a high concentration state. As a result, even when the cathode is operated at a high current density, the generation of Joule heat in the electron emitting material layer 63 is reduced and the barium (B
The degree of evaporation of a) is also reduced.

As described above, the cathode structure disclosed in the above-mentioned Japanese Patent Application Laid-Open No. HEI 5-12983 has a high-density current operating state, for example, 2A.
Even when operated in a high current density state of about / cm ² , a decrease in current emission can be reduced, and a long-life cathode assembly can be obtained.

[0009]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 5-129 is disclosed.
The cathode assembly disclosed in No. 83 can obtain stable electron emission characteristics in a high current density operation state for a long time. For example, the cathode assembly is used for a large display monitor having a phosphor screen diagonal diameter of 51 cm. In the color cathode ray tube used, the diameter of the electron beam passage hole of the first grid electrode (G1) of the electron gun is 0.4 mm, and the cathode current is 300.
In the case of μA (equivalent to 2.7 A / cm ² at the time of cathode load), the cathode current at the time of cathode load is large, so that it is not possible to obtain sufficient electron emission characteristics as a color cathode ray tube, and a relatively short-life color cathode ray tube May be a tube. That is, the cathode assembly disclosed in the above-mentioned JP-A-5-12983 is
No consideration is given to the enlargement and high brightness (increase in cathode current) of a color cathode ray tube such as a color cathode ray tube used for a large display monitor.

Generally, barium scandate (Ba ₂ S)
rare earth metal oxides such as c ₂ O ₅ )
3 for keeping free barium (Ba) in the electron emitting material layer 63 in a high concentration state, and containing barium (Ba) contained in the upper layer 63 ₂ of the electron emitting material layer 63. The higher the dispersion of scandate (Ba ₂ Sc ₂ O ₅ ), the higher the concentration of free barium (Ba) can be maintained.

However, barium scandate (Ba ₂
Since rare earth metal oxides such as Sc ₂ O ₅ ) do not contribute to electron emission at all, if the content of rare earth metal oxides is increased in order to improve high-density current operation characteristics, the electron emitting material layer The amount of electron emission from 63 is reduced. On the other hand, it is possible to increase the thickness of the electron emitting material layer 63 and relatively increase the amount of dispersion of the rare earth metal oxide. However, with such a configuration, the heat capacity of the electron emitting material layer 63 can be increased. And the operating characteristics deteriorate, such as the emission rise time (image output time) being delayed, and at the same time, the thermal stress based on the difference in thermal expansion coefficient between the electron emitting material layer 63 and the cathode substrate 62 increases. In some cases, the electron emitting material layer 63 may be separated from the cathode base 62.

Further, in the electron emissive material layer 63, thinning the thickness of the lower layer 63 _1, when increasing the thickness of the relatively upper layer 63 _2, the alkali metal oxide in the lower layer 63 in ₁ since the average particle diameter is almost the same degree as the thickness of the lower layer 63 _1, barium upper layer 63 in the ₂ scandate (Ba ₂ S
The rare earth metal oxide such as c ₂ O ₅ ) comes into contact with the cathode substrate 62, and the adhesive force of the electron emitting material layer 63 decreases,
The electron-emitting substance layer 63 comes off from the cathode base 62.

The present invention has been made in view of such technical background, and has as its object to prevent a decrease in the amount of electron emission while maintaining excellent high-density current operation characteristics, and to provide a cathode ray tube. An object of the present invention is to provide a cathode structure that can cope with an increase in size and an increase in luminance.

[0014]

In order to achieve the above object, a cathode structure according to the present invention comprises a polyhedral alkaline earth metal oxide particle having an electron emission material layer on the top side of a cathode substrate. And a lower layer formed on the lower layer by needle-shaped alkaline earth metal oxide particles containing a rare earth metal oxide. The thickness is 5 to 3 times the thickness of the electron emitting material layer
With the first means selected to be in the range of 7%.

According to another aspect of the present invention, there is provided a cathode structure according to the present invention, wherein the electron emission material layer is on the top surface of the cathode substrate, and has an alkaline earth metal oxide having a first average particle size. A lower layer formed by the particles, and alkaline earth metal oxide particles having a second average particle size larger than the first average particle size on the lower layer and containing the rare earth metal oxide. A second means selected from the group consisting of an upper layer formed and a thickness of the lower layer being in a range of 5 to 37% of a thickness of the electron emitting material layer.

According to the first means and the second means,
Since the lower layer of the electron emitting material layer to be formed on the top side of the cathode substrate is formed of polyhedral alkaline earth metal oxide particles or alkaline earth metal oxide particles having a small average particle size. Even if the thickness of the lower layer is reduced, contact between the rare earth metal oxide in the upper layer of the electron emitting material layer and the cathode substrate can be prevented, so that the thickness of the upper layer can be increased. As a result, the dispersion amount of the rare earth metal oxide contained in the upper layer can be relatively increased. When the amount of dispersion of the rare earth metal oxide becomes relatively large, free barium (Ba) in the electron emitting material layer is increased.
Is maintained in a high concentration state, so that the electric resistance of the electron emitting material layer is small, the generation of Joule heat in the electron emitting material layer is reduced, and a cathode structure capable of exhibiting excellent high current density operation characteristics is provided. Obtainable.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention, a cathode assembly is formed by attaching a cathode sleeve, a cathode base fitted to one end of the cathode sleeve, and a top surface of the cathode base. An electron emitting material layer, wherein the electron emitting material layer is on the top side of the cathode substrate, and a lower layer formed of polyhedral alkaline earth metal oxide particles,
An upper layer formed of needle-like alkaline earth metal oxide particles containing a rare earth metal oxide on the lower layer, and the lower layer has a thickness of 5 times the thickness of the electron emitting material layer. ３７37%.

In the second embodiment of the present invention, the cathode structure includes a cathode sleeve, a cathode base fitted to one end of the cathode sleeve, and an electron emitting material layer formed on the top surface of the cathode base. A lower layer formed of alkaline earth metal oxide particles having a first average particle size, the lower layer being located on the top surface side of the cathode substrate, And an upper layer formed by alkaline earth metal oxide particles having a second average particle size larger than the first average particle size containing the rare earth metal oxide, and a thickness of the lower layer. The thickness is 5 to 37 times the thickness of the electron emitting material layer.
% Are selected.

In one specific example of the second embodiment of the present invention, the cathode structure has a first average particle diameter selected to be not more than の of a second average particle diameter.

In a preferred embodiment of the first and second embodiments of the present invention, the cathode structure is characterized in that the rare earth metal oxide is barium scandate (Ba ₂ Sc ₂ O ₅ ) and the content is 1 to 3 % By weight.

According to the first embodiment of the present invention, as the electron emitting material layer for emitting electrons from the cathode, a lower layer formed on the top surface of the cathode base, and a lower layer formed on the lower layer. The upper layer is formed into a two-layer structure, and the lower layer is formed of polyhedral alkaline earth metal oxide particles, and the upper layer is formed of needle-shaped alkaline earth metal oxide particles containing a rare earth metal oxide. Since the average particle size of the alkaline earth metal oxide particles in the lower layer is small, even if the lower layer is formed to be relatively thin, the rare earth metal oxide in the upper layer and the cathode substrate Can be prevented from contacting with each other, and the thickness of the lower layer can be reduced, so that the thickness of the upper layer can be increased accordingly, and the dispersion of the rare earth metal oxide contained in the upper layer can be reduced. The amount can be relatively large.

When the amount of dispersion of the rare earth metal oxide in the electron emitting material layer becomes relatively large, the free barium (Ba) in the electron emitting material layer can be maintained in a high concentration state. It is possible to obtain a cathode assembly which has small electric resistance, generates less Joule heat in the electron emitting material layer, and can exhibit excellent high current density operation characteristics capable of coping with an increase in the size or brightness of a cathode ray tube. .

According to the second embodiment of the present invention, the lower layer formed on the top surface of the cathode substrate and the lower layer formed on the lower layer are used as the electron emitting material layer for emitting electrons from the cathode. The upper layer is formed of a two-layer structure, and the lower layer is made of alkaline earth metal oxide particles having a small average particle diameter, and the upper layer is made of alkaline earth metal oxide having a large average particle diameter containing a rare earth metal oxide. Even if the lower layer is formed to have a relatively small layer thickness, it is possible to prevent the rare earth metal oxide in the upper layer from coming into contact with the cathode substrate. Since the thickness of the layer can be reduced, the thickness of the upper layer can be increased accordingly, and the amount of dispersion of the rare earth metal oxide contained in the upper layer can be relatively increased.

When the amount of dispersion of the rare earth metal oxide in the electron emitting material layer is relatively large, the free barium (Ba) in the electron emitting material layer can be maintained in a high concentration state. It is possible to obtain a cathode structure that has excellent electric current density operating characteristics, which has a small electric resistance, generates less Joule heat in the electron emitting material layer, and can respond to an increase in the size or brightness of the cathode ray tube. it can.

[0025]

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

FIG. 1 is a sectional view showing a schematic configuration of a color cathode ray tube using the cathode assembly according to the present invention.

In FIG. 1, reference numeral 1 denotes a panel portion, 1F denotes a face plate, 2 denotes a neck portion, 3 denotes a funnel portion, 4 denotes a fluorescent surface, 5 denotes a shadow mask, 6 denotes a magnetic shield, 7 denotes a deflection yoke, and 8 denotes a deflection yoke. The adjusting magnet assembly, 9 is an in-line electron gun, and 10 is an electron beam (only one of the three is shown).

The glass tube constituting the color cathode ray tube is provided on the front side of the glass tube, is provided with a panel section 1 having a large-diameter face plate 1F, and is provided on the rear side of the glass tube, and is internally provided. It comprises an elongated neck portion 2 in which an inline electron gun 9 is housed, and a funnel-shaped funnel portion 3 connecting the panel portion 1 and the neck portion 2 and having a deflection yoke 7 mounted on the outer periphery. A fluorescent surface 4 is formed on the face plate 1F of the panel unit 1 on its inner surface.
A shadow mask 5 is fixed inside so as to face the fluorescent screen 4. A magnetic shield 6 is arranged inside a joint area between the panel unit 1 and the funnel unit 3. Neck part 2
A magnet assembly 8 for adjusting the purity and convergence is arranged outside the box. The three electron beams 10 projected from the in-line electron gun 9 are deflected in a predetermined direction by a magnetic field generated by the deflection yoke 7, and then are passed through many electron beam passage holes (not shown) provided in the shadow mask 5. To reach the corresponding color pixel on the fluorescent screen 4 through the light emitting element.

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

FIG. 2 is a side view showing the structure of the in-line electron gun 9 used in the color cathode ray tube shown in FIG.

In FIG. 2, reference numeral 11 denotes a cathode structure, 12 denotes a control electrode (G1), 13 denotes an acceleration electrode (G2), and 14 denotes a first electrode.
Focusing electrodes (G3), 15 (1), 15 (2) are second focusing electrodes (G4), 16 is third focusing electrodes (G5), 17 is an anode electrode, 18 is a pair of bead glasses, 19 is a stem, 2
0 is a support material.

The in-line electron gun 9 includes a control electrode 12, an acceleration electrode 13,
The first focusing electrode 14, the second focusing electrode 15 (1), the second focusing electrode 15 (2), the third focusing electrode 16, and the anode electrode 17 are arranged in this order. Control electrode 12, accelerating electrode 13, first
Each of the focusing electrode 14, the second focusing electrode 15 (1), the second focusing electrode 15 (2), the third focusing electrode 16, and the anode electrode 17 passes three electron beams emitted from the cathode assembly 11. An electron beam passage hole (not shown) is provided, and is held and fixed by a pair of bead glasses 18. The pair of bead glasses 18 are fixed to pins (not shown) erected on a stem 19, hold and fix the cathode structure 11 with a support member 20, and at the same time, simultaneously control the control electrode 1.
2, acceleration electrode 13, first focusing electrode 14, second focusing electrode 1
5 (1), second focusing electrode 15 (2), third focusing electrode 1
6. Each of the anode electrodes 17 is held and fixed.

FIG. 3 is a cross-sectional view showing the configuration near the cathode assembly 11 in the in-line electron gun 9 shown in FIG.

In FIG. 3, 12H is an electron beam passage hole of the control electrode 12, 21 is a cylindrical cathode sleeve, 22 is a cap-shaped cathode base, 23 is an electron emitting material layer, 24 is a heater,
24L is a heater lead, 25 is a funnel-shaped metal support, 2
Reference numeral 6 denotes a bosh eyelet, reference numeral 27 denotes a heater support, and other components that are the same as those shown in FIG.

The cylindrical cathode sleeve 21 has a cap-shaped cathode base 22 fitted at one end and a heater 24 housed therein, thereby constituting an indirectly heated cathode. The cap-shaped cathode substrate 22 has an electron-emitting material layer 23 formed on the top surface.
In the control electrode 12, an electron beam passage hole 12H is formed in a portion facing the electron emitting material layer. Heater 24
The open ends of the heater leads 24L provided at both ends are welded to one end of the heater support 27. The funnel-shaped metal support 25 has a small-diameter portion and a large-diameter portion, and the small-diameter portion is fitted and fixed to the outer periphery of the other end region of the cathode sleeve 21. The bosh eyelet 26 includes a small-diameter portion and a large-diameter portion, and the small-diameter portion is fitted and fixed to the outer periphery of the large-diameter portion of the funnel-shaped metal support 25. Bonded to bead glass 18. The heater support 27
The other end is joined to the pair of bead glasses 18.

With such a configuration, the cathode sleeve 2
1 is fixed to a pair of bead glasses 18 by a funnel-shaped metal support 25, a bosh eyelet 26, and a support material 20, and the heater 24 is also fixed to a pair of bead glasses 18 by a heater lead 24L and a heater support 27. .

FIG. 4 is a sectional view showing the main components of the cathode structure 11 shown in FIG.

[0038] In FIG. 4, 23 ₁ the electron emitting substance layer 2
3 of the lower (first) layer, 23 ₂ is the upper (second) layer of the electron emitting material layer 23, other, are identified by the same reference numerals for the same components as those shown in FIG. 3 .

The cylindrical cathode sleeve 21 is made of a metal material containing a high melting point metal, for example, nickel (Ni) as a main component and a small amount of a reducing metal such as silicon (Si) or magnesium (Mg) therein. Composed of Similarly, the cap-shaped cathode substrate 22 is made of a metal material containing a high melting point metal, for example, nickel (Ni) as a main component and a small amount of a reducing metal such as silicon (Si) or magnesium (Mg) therein. Be composed. Lower layer 23 ₁ of the electron emitting material layer 23 is made of an alkaline earth metal oxide particles of polyhedral shape, it is deposited and formed on the top surface of the cathode substrate 22. The upper layer 23 _{and second} electron emitting material layer 23 is made of an alkaline earth metal oxide particles of needle-shaped including a rare earth metal oxide, is deposited and formed on the upper surface of the lower layer 23 _1.

[0040] In this case, the alkaline earth metal oxide used in the lower layer 23 ₁ is a carbonate of barium strontium calcium [(Ba · Sr · Ca) CO 3], used in the upper layer 23 ₂ The alkaline earth metal oxide containing the rare earth metal oxide to be used is a barium strontium calcium carbonate [(Ba.Sr.Ca) C] in which barium scandate (Ba ₂ Sc ₂ O ₅ ) or the like is dispersed.
O ₃ ].

Here, the lower layer 23 of the electron emitting material layer 23
₁ and the upper layer 23 ₂ is formed by the following procedure.

[0042] For the first suspension to form a lower layer 23 ₁ (slurry), 54 wt% of barium nitrate (Ba
NO ₃ ), 39% by weight strontium nitrate (SrNO
_3), in a mixed solution of 7% by weight of calcium nitrate (CaNO _3), carbonate of barium strontium calcium by addition of sodium carbonate _{(Na 2 CO 3) [(} Ba
[Sr.Ca) CO ₃ ] was precipitated to obtain a first powdery precipitate. Barium strontium calcium carbonate [Ba.Sr.Ca] which is the first precipitate
[CO ₃ ] has a polyhedral shape (observed by an electron microscope) having an average particle size of 2 μm when measured using a Microtrac particle size distribution analyzer. A nitrocellulose lacquer and butyl acetate were added to the obtained first precipitate, followed by rolling and mixing, and a first suspension (slurry) was obtained.
Is prepared.

The measurement of each particle shape described below
All were measured using a Microtrac particle size distribution meter.

On the other hand, for the second suspension to form the upper layer 23 ₂ (slurry), 53 wt% of barium nitrate (Bano _3), 38 wt% of strontium nitrate (S
rNO ₃ ), 6% by weight of calcium nitrate (CaNO ₃ )
Sodium carbonate (Na ₂ CO ₃ ) is added to the mixed solution to precipitate barium, strontium, calcium carbonate [(Ba.Sr.Ca) CO ₃ ] to obtain a powdery second precipitate. ing. Barium strontium calcium carbonate [Ba.Sr]
.Ca) CO ₃ ] has an average particle diameter of 10 μ
m. 3% by weight of barium scandate (Ba ₂ Sc ₂ O) was added to the obtained second precipitate.
₅ ) is mixed, and a nitrocellulose lacquer and butyl acetate are added to the mixture, followed by rolling and mixing to prepare a second suspension (slurry).

Next, the top surface of the cap-shaped cathode substrate 22 mainly composed of nickel (Ni), a first suspension is applied by spraying, the lower layer 23 ₁ having a thickness of about 8μm Form. Then, the upper surface of the lower layer 23 _1, similar to the second suspension is applied by spraying, to form the upper layer 23 ₂ thickness of about 60 [mu] m. At this time, the particle shape of barium scandate (Ba ₂ Sc ₂ O ₅ ) has an average particle size of 1.
It has a 2μ polyhedron shape.

[0046] Then, in the vacuum evacuation process of the color cathode ray tube, the lower layer 23 ₁ and the upper layer 23 _{and second} electron emitting material layer 23, by heating by energization of the heater 24, the lower layer 23 ₁ and the upper carbonate of barium strontium calcium in the layer 23 in the ₂ [(Ba-Sr
[Ca] CO ₃ ] is thermally decomposed to produce oxides of barium, strontium and calcium [(Ba.Sr.Ca) O]. Therefore, the electron emitting material layer 23 includes a lower layer 23 ₁ consisting of alkaline earth metal oxide particles, the upper layer 23 ₂ is formed consisting of rare earth metal oxides laden alkaline earth metal oxide particles .

After that, the electron emitting material layer 23 is heated at a temperature of 90 °.
Activation is performed by heating in an atmosphere of 0 to 1100 ° C. to form the cathode assembly 11.

According to the cathode structure 11 of the present embodiment having the above-described configuration, the upper layer 23 made of alkaline earth metal oxide particles containing barium scandate (Ba ₂ Sc ₂ O ₅ ).
₂ and barium scandate (Ba ₂ Sc ₂ O ₅ )
The free barium (Ba) is constrained by this, and the free barium (Ba) in the electron emitting material layer 23 is maintained in a high concentration state, so that a cathode assembly that can exhibit excellent high current density operation characteristics can be obtained. In this case, cathode assembly 11 of this embodiment, since the select the layer thickness of the lower layer 23 ₁ consisting of alkaline earth metal oxide particles to about 12% of the layer thickness of the whole electron emitting material layer 23, an electron 88% of the emissive material layer 23 can be configured by the upper layer 23 ₂ that are dispersed rare earth metal oxide, it is possible to improve the high current density operating characteristics. Also, appropriate alkaline earth metal oxide particles constituting the lower layer 23 ₁ is assumed polyhedral, about 1/4 of the layer thickness of the lower layer 23 ₁ average particle size is a 2μm since, without barium scandate dispersed in the upper layer _{23 2 (Ba 2 Sc 2 O} 5) is in contact with the cathode substrate 22, the adhesion between the electron emitting material layer 23 and the cathode substrate 22 is lowered As a result, the electron emitting material layer 23 does not peel off from the cathode base 22.

In the above embodiment, the electron emitting material layer 2
The layer thickness of the lower layer 23 ₁ in 3 to about 8 [mu] m, although the thickness of the upper layer 23 ₂ illustrates an example of approximately 60 [mu] m, the cathode structure of the present invention the lower layer 23 ₁ and the upper layer 23 _Two
The thickness of each layer is not limited to the above example, and may be selected so as to be each other.

[0050] That is, the one example (hereinafter, the example of another of the first example) as forms to resemble approximately 5μm layer thickness of the lower layer 23 ₁ in the electron emissive material layer 23,
It formed so that the layer thickness of the upper layer 23 ₂ to about 75 [mu] m, is obtained by the thickness of the lower layer 23 ₁ to about 6% of the layer thickness of the whole electron emitting material layer 23. The method of forming the electron-emitting material layer 23 in the other first example is the same as that of the above-described embodiment. First, the first surface prepared in the above-mentioned embodiment by the spray method is applied to the top surface of the cap-shaped cathode base 22. suspension the same suspension as the (slurry) is applied to form a layer lower layer 23 ₁ having a thickness of about 5 [mu] m, then the out by the upper surface of the lower layer 23 _1, similar spraying examples The second prepared in
Apply the same suspension (slurry) as
those forming the upper layer 23 _{and second} layer thickness of m.

[0051] In another first embodiment, the electron emitting material layer the layer thickness of the lower layer 23 ₁ consisting of alkaline earth metal oxide 2
Barium scandate (Ba ₂ Sc ₂₎
By the O ₅₎ the ratio of the layer thickness of the upper layer 23 ₂ made of alkaline earth metal oxide containing about 94% of the layer thickness of the electron emitting material layer 23, as in the embodiment, the height Current density operation characteristics can be improved. Further, also in the first example of another, with 2μm average particle size of the alkaline earth metal oxide constituting the lower layer 23 _1, it falls into about 2/5 of the layer thickness of the lower layer 23 _1, never barium scandate dispersed in the upper layer _{23 2 (Ba 2 Sc 2 O} 5) is in contact with the cathode substrate 22, the adhesion between the electron emitting material layer 23 and the cathode substrate 22 is reduced, the electronic The radiation material layer 23 does not peel off.

[0052] Moreover, other examples (hereinafter, this example that other second example) as forms to resemble approximately 26μm layer thickness of the lower layer 23 ₁ in the electron emissive material layer 23, the upper layer 23 to form a layer thickness of ₂ to be about 60 [mu] m, it is obtained by the thickness of the lower layer 23 ₁ to about 30% of the thickness of the whole electron emitting material layer 23. The method of forming the electron-emitting material layer 23 in the other second example is the same as that of the above-described embodiment.
First, the same suspension as the first suspension (slurry) prepared in the above embodiment was applied to the top surface of the hat-shaped cathode substrate 22 by a spray method, and the lower layer 23 having a thickness of about 26 μm was applied. ₁ is formed, then the upper surface of the lower layer 23 _1, first prepared in the example by the similar spraying method 2
Of the same suspension (slurry) of
those forming the upper layer 23 _{and second} layer thickness of m.

In another second example, an alkaline earth metal
Lower layer 23 made of oxide₁Layer thickness of electron emitting material layer 2
3 to about 30%, barium scandate (Ba_TwoSc
_TwoO _Five) Containing alkaline earth metal oxides
Layer 23_TwoOf the thickness of the electron emitting material layer 23
By making it about 70% of the thickness, similar to the above embodiment,
High current density operation characteristics can be improved. Also,
In the other second example, the lower layer 23₁Make up the arca
The average particle diameter of the earth metal oxide is 2 μm, and the lower layer 23₁
Of the upper layer 23,_TwoMinute
Scattered barium scandate (Ba_TwoSc_TwoO_Five)But
The electron emitting material layer 2 does not come into contact with the cathode base 22.
3 and the cathode substrate 22 have reduced adhesive strength,
The material layer 23 does not peel off.

Here, FIG. 5 is a characteristic diagram showing the relationship between the amount of electron emission and the operation time in the cathode assembly of the present invention.

[0055] In FIG. 5, the electron emission amount and the vertical axis in% and the abscissa is a operation time, expressed in kh (Kiroawa), 8 [mu] m layer thickness of the lower layer 23 ₁ curve a, the upper layer 23
Despite the _second thickness to 60 [mu] m Examples and 26μm of thickness of the lower layer 23 _1, an example in which the thickness of the upper layer 23 ₂ to 60 [mu] m, the curve b 5 [mu] m layer thickness of the lower layer 23 ₁ , an example in which the thickness of the upper layer 23 ₂ to 75 [mu] m. Curve c is for comparison and is a known example in which the thickness of each of the lower layer and the upper layer is 34 μm.

As shown by the curves a and b in FIG. 5, the cathode structure of the present embodiment has a smaller rate of decrease in the amount of electron emission as the operation time elapses as compared with the known cathode structure. As a result, the life can be extended while maintaining the high current density operation.

[0057] In this case, the layer thickness of the lower layer 23 _1, becomes less than 5% of the thickness of the electron emitting material layer 23, the lower layer 23 ₁
Barium scandate (Ba) dispersed in the upper layer 23 from the relationship between the layer thickness of Al and the average particle size of the alkaline earth metal oxide.
₂ Sc ₂ O ₅ ) may contact the cathode substrate 22, which is not preferable.
Barium scandate (Ba ₂ Sc)
Similarly, the total amount of ₂ O ₅ ) becomes insufficient. As a result, the layer thickness of the lower layer 23 ₁ definitive present invention selected to be in the range of 5 to 37% of the thickness of the electron emitting material layer 23.

In each of the examples including the above embodiment,
The content of barium scandate (Ba ₂ Sc ₂ O ₅₎ has been described by way of example a 3% by weight, a barium scandate contained in the upper layer 23 _{and second} electron emitting material layer 23 of the present invention (Ba ₂ Sc ₂ O ₅ ) content is 3% by weight
Is not limited to the case, other contents, specifically 0.0
Any content within the range of 1 to 15.0% by weight can be selected.

That is, barium scandate (Ba ₂
If the content of Sc ₂ O ₅ ) is 0.01% by weight or less,
The significance of the inclusion of barium scandate (Ba ₂ Sc ₂ O ₅ ) is lost. On the other hand, when the content of barium scandate (Ba ₂ Sc ₂ O ₅ ) is 15.0% by weight or more, electron emission occurs. Since the electron emission function in the material layer 23 is reduced, barium scandate (Ba ₂ Sc) is used.
The content of ₂ O ₅ ) is selected in the range of 0.01 to 15.0% by weight.

[0060] Further, the in each case, including the examples, barium scandate (Ba ₂ S as the rare earth metal oxide used in the upper layer 23 _{and second} electron emitting material layer 23
Although an example using c ₂ O ₅ ) has been described, the rare earth metal oxide used in the present invention is barium scandate (B
It is a matter of course that the rare earth metal oxide having similar characteristics to barium scandate (Ba ₂ Sc ₂ O ₅ ) may be used without being limited to a ₂ Sc ₂ O ₅ ).

[0061]

As described above, according to the first aspect of the present invention, as the electron emitting material layer that emits electrons from the cathode,
A lower layer adhered and formed on the top side of the cathode substrate and an upper layer adhered and formed on the lower layer have a two-layer structure, and the lower layer is formed of polyhedral alkaline earth metal oxide particles. The upper layer is formed of needle-shaped alkaline earth metal oxide particles containing a rare earth metal oxide, and the average particle diameter of the alkaline earth metal oxide particles in the lower layer in the thickness direction is small. Even if the lower layer is formed to have a relatively small thickness, the rare earth metal oxide in the upper layer can be prevented from contacting the cathode substrate, and the lower layer can be made thinner. In addition, the thickness of the upper layer can be increased by that amount, and the amount of dispersion of the rare earth metal oxide contained in the upper layer can be relatively increased. And when the dispersion amount of the rare earth metal oxide in the electron emitting material layer becomes relatively large,
Since free barium (Ba) in the electron emitting material layer can be maintained in a high concentration state, the electric resistance of the electron emitting material layer is small, the generation of Joule heat in the electron emitting material layer is reduced, and the cathode ray tube It can respond to large size and high brightness,
There is an effect that a cathode assembly capable of exhibiting excellent high current density operation characteristics can be obtained.

According to the second aspect of the present invention, as the electron emitting material layer for emitting electrons from the cathode, a lower layer formed on the top surface of the cathode base and a lower layer formed on the lower layer are formed. The upper layer is formed of a two-layer structure, and the lower layer is made of alkaline earth metal oxide particles having a small average particle diameter, and the upper layer is made of alkaline earth metal oxide having a large average particle diameter containing a rare earth metal oxide. Even if the lower layer is formed to have a relatively small layer thickness, it is possible to prevent the rare earth metal oxide in the upper layer from coming into contact with the cathode substrate. Since the thickness of the layer can be reduced, the thickness of the upper layer can be increased accordingly, and the amount of dispersion of the rare earth metal oxide contained in the upper layer can be relatively increased. When the dispersion amount of the rare earth metal oxide in the electron emitting material layer becomes relatively large, free barium (Ba) in the electron emitting material layer can be maintained in a high concentration state. The effect is that the electrical resistance is small, the generation of Joule heat in the electron emitting material layer is reduced, and a cathode structure that can exhibit excellent high current density operation characteristics that can respond to the enlargement and high brightness of the cathode ray tube is obtained. There is.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a color cathode ray tube using a cathode assembly according to the present invention.

FIG. 2 is a side view showing a configuration of an in-line electron gun used in the color cathode ray tube shown in FIG.

FIG. 3 is a cross-sectional view showing a configuration near a cathode assembly in the in-line electron gun shown in FIG.

FIG. 4 is a cross-sectional configuration diagram illustrating main components of the cathode assembly illustrated in FIG. 3;

FIG. 5 is a characteristic diagram showing a relationship between an electron emission amount and an operation time in a cathode assembly obtained according to the present invention.

FIG. 6 is a cross-sectional view showing an example of a configuration of a known cathode structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Panel part 1F Face plate 2 Neck part 3 Funnel part 4 Fluorescent surface 5 Shadow mask 6 Magnetic shield 7 Deflection yoke 8 Magnet assembly for adjustment 9 In-line electron gun 10 Electron beam 11 Cathode assembly 12 Control electrode (G1) 12H Electron beam passage Hole 13 Acceleration electrode (G2) 14 First focusing electrode (G3) 15 (1), 15 (2) Second focusing electrode (G4) 16 Third focusing electrode (G5) 17 Anode electrode 18 A pair of bead glasses 19 Stem 20 Support material 21 Cylindrical cathode sleeve 22 Cap-shaped cathode base 23 Electron emitting material layer 23 ₁ Lower (first) layer 23 ₂ Upper (second) layer 24 Heater 24L Heater lead 25 Metal support 26 Eyelet 27 Heater support

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yukio Koizumi 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd. (72) Inventor Satoru 3300 Hayano, Mobara-shi, Chiba Electronic Device Business, Hitachi, Ltd. Department F-term (reference) 5C031 DD04 DD09

Claims (4)

[Claims] 1. A cathode structure comprising: a cathode sleeve; a cathode substrate fitted to one end of the cathode sleeve; and an electron emission material layer adhered to a top surface of the cathode substrate. The layer is on the top side of the cathode substrate, a lower layer formed of polyhedral alkaline earth metal oxide particles, and a needle-shaped layer on the lower layer, containing a rare earth metal oxide. An upper layer formed of alkaline earth metal oxide particles, wherein the thickness of the lower layer is selected to be in the range of 5 to 37% of the thickness of the electron emitting material layer. A cathode structure characterized by the above-mentioned. 2. A cathode structure comprising: a cathode sleeve; a cathode substrate fitted to one end of the cathode sleeve; and an electron emission material layer adhered to a top surface of the cathode substrate. A layer on the top side of the cathode substrate, a lower layer formed by alkaline earth metal oxide particles having a first average particle size, and a layer on the lower layer, the rare earth metal oxide And an upper layer formed of alkaline earth metal oxide particles having a second average particle size larger than the first average particle size. Cathode structure selected to be in the range of 5 to 37% of the thickness of the cathode structure. 3. The cathode structure according to claim 2, wherein the first average particle size is selected to be equal to or less than half of the second average particle size. 4. The rare earth metal oxide is barium scandate (Ba ₂ Sc ₂ O ₅ ), and its content is in the range of 1 to 3% by weight. 4. The cathode ray tube according to 3.