JPH01194231A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To suppress increase of crossover dia. and enhance the characteristic by offsetting a zone in the center of the electron emitting surface of a cathode pellet, wherein the zone shall have an area smaller than the dia. of an electron beam passing hole in adjoining No.1 electrode and emit an extraordinarily small amount of electron beam. CONSTITUTION:A cylindrical dint 1h is formed in the center of the electron emitting surface of an impregnated type cathode pellet 1. Ahead the pellet 1, No.1-No.3 electrodes 2-4 provided in their centers with electron beam passing holes 21, 31, 41 are arranged concentrically with the cylindrical dint 1h. The cathode pellet 1 is fitted to a cup 6 made of heat resistant metal, and this cup 6 is fixed to one end of a sleeve 7 made of heat resistant metal equipped internally with a heater 5. Therein most of the electron beam 8 is emitted from the flat part 1a of cathode pellet 1 other than the dint 1h, which suppresses spread of the crossover 9 because of the space charge effect.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cathode ray tube equipped with an impregnated cathode, and particularly to an impregnated cathode that can form a hollow electron beam suitable for improving electron beam focusing performance. The present invention relates to a cathode ray tube equipped with a cathode.

[Conventional technology]

A conventional example will be explained with reference to FIG. This figure shows a half cross section from the center of the cathode, showing the impregnated cathode mounted in an electron gun with a triode electron emitting section. That is, 1' is a cathode pellet made of a porous metal base made of a sintered body of a high-melting point metal such as tungsten (W) or molybdenum (Mo) impregnated with an electron emitting substance, and is inserted into the cup 6. . Reference numeral 7 denotes a cylindrical sleeve, into which the cup 6 is press-fitted, and the heater 5 is attached to the lower part of the sleeve. On the electron beam emitting surface side of the cathode pellet 1', there is an electron beam passage hole 21 in the center.
．． First electrode 2, second electrode 3 of an electron gun having 31.41
．． The third electrodes 4 are arranged coaxially with the center of the cathode pellet and spaced apart from each other by a predetermined distance. 8′
9 schematically indicates the spread of the emitted electron beam, 9' indicates the crossover portion of the electron beam, and r/c schematically indicates the crossover radius of the electron beam. In the triode-type electron emitting section shown in this figure, the first electrode 2 is set at a lower potential or at most the same potential as that of the cathode pellet 1', while the second and third electrodes 4 are set at several hundred to several thousand volts. It is set to high potential. An example of this type of method is JP-A-59-18539.

Although it is not an impregnated cathode, an example of a general literature in which a hollow electron beam is formed using the cathode of a microwave tube is McGraw-Hill Physical and Quantum Electronics Series [Space Charge Flow J, 1967, p. 157] (McGRAV・HILLPHYSIC
AL AND QUANTUM ELECTRONIC
55ERIES.

Space-Charge Flow, 1967,
Page 157).

[Problem to be solved by the invention]

In the case of the electrode potential configuration as shown in FIG. They are converged and, as a result, intersect near the first electrode 2 or the second electrode 3. This is called a crossover 9', but the crossover has a finite size (radius r /
c). The electron beam 8' then expands again, but
Second electrode3. The light is accelerated by the electric field formed by the third electrode 4 and enters the main lens portion (not shown). Further, in the case of a cathode ray tube, for example, the electron beam is converged by the main lens portion to form a spot on the phosphor screen. Incidentally, in order to improve the resolution of a cathode ray tube, it is generally necessary to reduce the spot diameter of the electron beam, and for this purpose it is effective to reduce the crossover radius r10.

One possible method for reducing the crossover and improving the resolution of the cathode ray tube is, for example, to make the electron beam passage hole of the first electrode 2 smaller than before to suppress the effect of silent speed dispersion. However, with this method, the electron emission area of the cathode is severely limited, making it difficult to obtain a large current.
For example, it is not suitable for large cathode ray tubes or projection cathode ray tubes that require a large current electron beam of several mA to several tens of mA.

Furthermore, at such a large current, the space charge effect becomes a major cause of increased crossover.

Furthermore, this space charge effect from the main lens to the phosphor screen is also a major cause of an increase in spot diameter.

In addition, the above-mentioned document in which the hollow electron beam was formed is an example of a microwave cathode, and relates to a mere cylindrical electrode, and does not give any consideration to an impregnated cathode.

Therefore, the technical problem to be solved by the present invention is to develop a cathode ray kit equipped with an impregnated cathode that can suppress the space charge effect and reduce the crossover diameter even in high-current electron beams. . Therefore, an object of the present invention is to achieve the above-mentioned technical problem and to provide a cathode ray tube having improved and excellent characteristics.

[Means to solve the problem]

The above technical problem can be achieved by the following solution. That is, the cathode ray tube of the present invention includes an impregnated cathode having a cathode pellet in which a heat-resistant porous metal substrate is impregnated with an electron-emitting substance, in which a central portion of the cathode pellet on the electron-emitting surface side, The present invention is characterized in that a region having an area smaller than the diameter of the electron beam passing hole of the adjacent first electrode and emitting an extremely small amount of electron beam is provided.

Examples of the heat-resistant porous metal substrate include well-known tungsten (W), molybdenum (Mo), iridium (Ir),
It is manufactured by press-molding and sintering high-melting point metal powder such as rhenium (Re). Further, the porosity of the porous metal substrate is considered to be approximately 17 to 30%. The impregnated cathode contains well-known electron-emitting substances such as barium (Ba) and strontium (Sr) in the pores.
, oxides of alkaline earth metals such as calcium (Ca), magnesium (Mg), or lanthanum boride (La
It is constructed by impregnating it with a boride of a rare earth element such as B.).

Practically preferred configurations for the region where the amount of electron beam emission is extremely small, which is a feature of the present invention, will be specifically exemplified below.

(1) First, the first configuration is to provide a polygonal recess or through hole including a circle with a surface area smaller than the diameter of the electron beam passage hole of the first electrode in the center of the electron emitting surface side of the cathode pellet. It is.

As a result, the area where the recess or through hole is provided emits significantly less electron beam than the area around the recess that has not been specially processed, and when looking at the cross section of the electron beam emitted from the surface of the cathode pellet, it appears as if it were hollow. It's like a beam. An important point of the present invention is to form such a hollow electron beam. Therefore, the effect of the through hole is greater than that of the recess. In addition, as a method for applying this type of processing to the cathode pellets, by providing a convex portion in advance on the press mold when press forming the metal powder constituting the base, the process can be easily performed at the same time as forming. Furthermore, after obtaining a flat sintered pellet, the central portion thereof may be processed. However, from a practical point of view, the former method is preferred because it is easier to process during molding.

(2) In the second configuration, instead of providing a recess or a through hole as described above, a material layer that inhibits electron beam emission is formed in this region of the pellet impregnated with an electron-emitting material, and the electron beam in the center of the pellet is The goal is to shield the beam from being emitted. The shape of the material layer is preferably a polygon (triangular, square, triangular, etc.) including a circle, as in the first configuration, since it forms a hollow electron beam. The material constituting this is preferably at least one metal such as titanium (Ti), zirconium (Zr), hafnium (Hf), carbon (C), or palladium (Pd).

As a forming method, well-known pattern forming techniques such as ordinary vapor deposition, sputtering, and printing can be used.

The preferred thickness is at least 10 nm, practically 0.5 to lOI! It is m.

(3) The third configuration uses the above-mentioned electron beam emission,
Instead of forming an inhibiting material layer, the pores in the porous portion of this region are crushed to make it non-porous. Although it is preferable to completely collapse the pores, it is also possible to significantly reduce the porosity.

The formation method can be realized by converging a laser beam or an electron beam and irradiating the predetermined region. This configuration can also be combined with the first configuration. In other words, by making the porous portion of the inner wall of the recess or through hole non-porous, the formation of a hollow electron beam can be made more favorable.

Moreover, this third configuration can be combined with the second configuration. In other words, a more preferable hollow electron beam can be formed by making a predetermined region non-porous using the third configuration and then forming a material layer thereon that inhibits electron beam emission using the second configuration. Can be done.

(4) As a fourth configuration, for example, ruthenium (RuL, iridium (Ir), , osmium (Os)
, scandium (S c), rhenium (Re), platinum (
An electron emission promoting material layer made of at least one of Pt) and alloys and oxides thereof is formed as a coating. This makes it possible to significantly increase the amount of electron emission in the peripheral part compared to the central part, and in combination with the first to fourth specific configurations described above, it is possible to form a more preferable hollow electron beam. Note that the thickness of this coating layer is practically about 10 nm to 1-1.

[Effect]

By configuring the cathode pellet as described above, most of the electron beam is emitted from the periphery excluding the center, and the electron beam becomes a hollow beam. effect) can be suppressed.

(Example) Hereinafter, seven examples of the present invention will be shown with reference to the drawings, and the present invention will be explained more specifically in detail.

FIG. 1 is a cross-sectional view of one side of the cathode of the present invention mounted in a triode type electron emitting section of an electron gun. In this example, a cylindrical depression 1h is formed in the center of the impregnated cathode pellet 1 on the electron emission surface side. In front of this cathode pellet 1 is a first electrode 2.31°41 provided with an electron beam passage hole 21.31°41 in the center. Second electrode3. The third electrodes 4 are arranged so as to be coaxial with the centers of the cylindrical recesses 1h of the cathode pellets. Note that the cathode pellet l is placed in a cup 6 made of heat-resistant metal.
The cup 6 is fixed to one end of a sleeve 7 made of heat-resistant metal and having a heater 5 provided therein by press-fitting, welding, or the like. In the case of such a cathode shape, most of the electron beam 8 is emitted from the flat part 1a of the cathode pellet 1 other than the depression 1h, and it is possible to suppress the spread of the crossover 9 due to the space charge effect. In this figure, the electron beam 8. crossover 9 and crossover r'c
is schematically shown. As a result, the crossover radius rc of the cathode pellet 1 of this embodiment is smaller than the crossover radius rIc of the conventional cathode pellet 1' shown in FIG. 4, which does not have a recess.

For cathode ray tubes and image pickup tubes, crossover radius (object point)
Reducing the size will reduce the spot diameter (image point) on the fluorescent screen or target surface, which is an extremely important condition for improving resolution.

However, in the case of this embodiment, electrons are also emitted from the recess 1h, albeit in a small amount. Since the emission direction and position (axial position) of this electron beam are different from most of the emitted electrons emitted from other parts, it is necessary to converge and irradiate both onto, for example, a phosphor screen under the same focus condition. This is difficult and results in a slight deterioration of focus characteristics. In order to improve this characteristic deterioration, a through hole (not shown) may be provided in place of the recess 1h, or a second
As shown in the figure, which is an enlarged view of the cathode pellet 1, there is a depression 1h.
By forming such a structure, the so-called electron emission promoting material layer 1c that promotes electron emission is coated on the flat part la other than the depression 1h, and the emission ability from the flat part 1a other than the depression 1h is improved. The amount of electrons emitted from the recess 1h is smaller than the amount emitted from other parts, and the deterioration of focus characteristics is improved.

As mentioned above, preferable examples of the electron emission promoting material layer include a material made of at least one of Ru, Ir, Os, Sc, Re, Pt, and alloys or oxides thereof.

The thickness of the coating layer IC is desirably 10 nm to 1 μm in consideration of the life of one layer and the diffusion of the electron-emitting substance impregnated into the porous substrate to the surface.

Note that 1b in FIG. 2 is an electron-emitting substance such as barium oxide, which is impregnated into the pores formed by the heat-resistant porous substrate 1e such as tungsten.

FIG. 3 is a diagram illustrating an assembly method for mounting the cathode having the configuration shown in FIG.
This figure shows a method for aligning the central axes of the electron beam passing holes 21.31°41 of No. 3 and 4.

As shown in FIG. 2, the impregnated cathode is made by impregnating a heat-resistant porous substrate 1e such as W with an electron-emitting substance 1b such as barium oxide, so it has considerable mechanical strength. , when mounting the cathode, use a center pin 10 as shown in FIG.
l Other inter-electrode spacing d2. d, can be easily set. That is, by inserting the tip of the center pin into the cylindrical recess 1h provided in the cathode pellet 1, accurate positioning is possible.

By the way, as another structure for forming a hollow electron beam, instead of providing the recess 1h shown in FIG. 1, a material layer is formed in the center of the electrode pellet to block electron emission from the surface of the electrode pellet.

Those that locally heat the fine pores on the surface of the porous body in the center of the pellet using a laser beam or electron beam to crush them and make them non-porous, and those that combine these with other configurations mentioned above. However, from the point of view of ease of alignment between the central axis of the cathode pellet and the central axis of the electron beam passing hole in the center of the electrode of the electron gun, it is recommended that the cathode pellet has a recess 1h or a through hole as shown in Figure 1 above. (not shown) is preferable because it can be mounted more accurately.

In other words, this depression can be used as a reference point for alignment.

Next, a method for manufacturing the cathode shown in FIGS. 1 and 2 will be explained in detail.

The heat-resistant porous metal substrate 1e is manufactured by press-forming into a cathode pellet shape using a cylindrical press jig and sintering using W powder whose particle size is adjusted.

Moreover, there is no problem in machining the cathode shape by cutting or the like after sintering. Incidentally, the depression 1h may be formed by providing a convex part in the mold during press working, or may be formed into a cylindrical depression with a drill etc. after sintering. A sintered body having a porosity of 28% was obtained by carrying out the same method as described in No. 18539. This porous metal substrate 1
In addition to the barium aluminate compound, a mixture of barium carbonate, aluminum oxide, and calcium carbonate may be used as the starting material for the electron emitting substance 1b to be impregnated into the pores of e. In this way, 4BaO- CaO-
A porous metal substrate 1e was impregnated with an electron-emitting material 1b made of AIlzO. The method of impregnating the porous metal substrate 1e with the electron-emitting substance 1b was a well-known technique. That is, the above barium aluminate compound raw material is placed on a porous metal substrate, heated and melted in hydrogen at about 1700° C., and poured into the pores to produce the impregnated cathode pellet 1.

Diameter 0.3mm, depth 0 manufactured as above
．． A 3111II impregnated cathode pellet 1 having a cylindrical recess is inserted into a molybdenum cup 6, and this is inserted into one end of a cylindrical molybdenum sleeve 7 in which a W-Re heater 5 (alumina coating) is installed. It was inserted and fixed to form a cathode. On the electron emitting surface side of this cathode, there is a first tube. Second. The third electron gun electrodes 2, 3.4 are arranged at predetermined intervals, with their central axes aligned with the center of the recess 1h provided in the cathode pellet (mounted using the center pin 1O shown in FIG. 3), It was mounted in a triode type electron emitting section having the configuration shown in FIG.

The results of calculating the crossover radius rc using the triode electron gun shown in FIG. 1 will be explained below.

Note that the diameter of the electron beam passage hole of the first electrode 2 at this time is 0.
．． 7 nua, and the diameter of the electron beam passage hole of the second electrode 3 was 0.7 mm.

A voltage of 30 to 200 V is applied to the cathode pellet, the first electrode 2 is at ground potential, and the second electrode 3 is at 600 V.

When a voltage of about 9 kV is applied to each of the third electric rods 4, an electron beam crossover 9 is formed between the first electrode and the second electrode, and its radius rC is as shown in the curve 51 in FIG. be.

On the other hand, under the same voltage application conditions, the crossover radius r10 calculated by the conventional example shown in FIG. 4 is as shown by a curve 52.

As described above, by forming a hollow electron beam according to the present invention, the crossover radius can be significantly improved compared to the conventional method.

FIG. 6 is a characteristic curve diagram showing the electron beam spot diameter on the phosphor screen when the cathode of the present invention is applied to a cathode for finch projection in comparison with that using a conventional cathode. Curve 61 according to the present invention had a significantly smaller spot diameter than the conventional curve 62, and very favorable results were obtained.

Note that the phosphor screen voltage was 30 kV.

〔Effect of the invention〕

According to the present invention, an increase in the crossover diameter due to the space charge effect can be suppressed, and the resolution of cathode ray tubes such as cathode ray tubes and image pickup tubes can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the cathode and electron gun electrode arrangement for explaining one embodiment of the present invention, and FIG. 4 is a conventional example.
FIG. 2 is a cross-sectional view of a cathode of another embodiment for further improving the effects of the present invention, FIG. 3 is a cross-sectional view of a cathode and an electrode showing an assembly method for mounting the cathode of the present invention in an electron gun, and FIG. 6 is a curve diagram showing an embodiment of the present invention, comparing the crossover radius and the spot diameter of the phosphor screen with a conventional example. In the figure, 1... Cathode pellet 1h... Hollow portion l
a... Cathode pellet flat portion 1e... Heat-resistant porous substrate 1b... Electron emitting material 1c... Coating layer 8 of a substance that promotes electron emission...
Emitted electron beam 9...Crossover re...
Crossover radius 10... Center pin agent Junnosuke Nakamura Figure 1 Figure 3 Figure 5 Beam 1, Tb (Day A)

Claims (1)

[Scope of Claims] 1. In a cathode ray tube equipped with an impregnated cathode having a cathode pellet in which a heat-resistant porous metal substrate is impregnated with an electron-emitting substance, a cathode pellet adjacent to the center of the electron-emitting surface side of the cathode pellet is provided. A cathode ray tube characterized in that a region having an area smaller than the diameter of the electron beam passage hole of the first electrode and emitting an extremely small amount of electron beam is provided. 2. As the region where the amount of electron beam emission is extremely small,
Claim 1, characterized in that a polygonal recess or through hole including a circle with a surface area smaller than the diameter of the electron beam passage hole of the first electrode is provided in the center of the electron emitting surface of the cathode pellet. The cathode ray tube according to item 1. 3. The cathode ray tube according to claim 2, wherein the cathode pellet is made non-porous by crushing the fine pores on the inner peripheral wall surface of the recess or through hole provided in the cathode pellet. 4. As the region where the amount of electron beam emission is extremely small,
2. The cathode ray tube according to claim 1, wherein a material layer that inhibits electron beam emission is formed at the center of the cathode pellet. 5. The material layer that inhibits electron beam emission is made of Ti, Z
5. The cathode ray tube according to claim 4, comprising at least one metal element selected from the group consisting of r, Hf, C, and Pd or an oxide thereof. 6. As the region where the amount of electron beam emission is extremely small,
Claims characterized in that a polygonal non-porous region including a circle having an area smaller than the diameter of the electron beam passing hole of the first electrode is provided in the center of the electron emitting surface side of the cathode pellet. The cathode ray tube according to item 1. 7. A patent characterized in that the cathode pellet is coated with an electron emission promoting material layer except for a region where the amount of electron beam emission is extremely small, which is provided at the center of the electron emission surface side of the cathode pellet. Claims 1, 2, and 4
The cathode ray tube according to item 6 or item 6. 8. The electron emission promoting material layer is made of Ru, Ir, Os, Sc.
8. The cathode ray tube according to claim 7, wherein the cathode ray tube is made of at least one metal element or metal oxide selected from the group consisting of , Re, and pt. 9. The thickness of the electron emission promoting material layer is 10 nm to 1 μm.
A cathode ray tube according to claim 7 or 8, characterized in that: 10. Claims 1 and 2, wherein the heat-resistant porous metal substrate is made of at least one metal element selected from the group consisting of W, Mo, Ir, and Re. The cathode ray tube according to item 4, 6 or 7.