JPH07161307A - Electron gun and electron tube provided with electron gun - Google Patents

Abstract

PURPOSE:To effectively suppress unnecessary electron emission by forming an oxide coating film possessing an electric insulating property in the vicinity of an aperture of an electrode controlling an electron beam of an electron gun. CONSTITUTION:Oxide coating films 40, 42 are formed in the vicinity of electron beam passing apertures 18a, 20a in each of electrodes 18, 20 of an electron gun. Usually, formation of deposition parts 18b, 20b tends to be generated in the vicinity of an electron emitting layer 14 of a negative electrode 17, and the deposition part is hardly formed in the area far from the electron emitting layer. Therefore, by means of the coating films 40, 42, grid emission can be effectively suppressed even when an electron emissive material such as barium is deposited on each of the electrodes 18, 20 from the negative electrode 17. Metal oxide such as silicon oxide or aluminum oxide is desirable for the coating films 40, 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun and an electron tube equipped with the electron gun, and more particularly to improvement of an electrode structure capable of suppressing unnecessary electron emission.

[0002]

2. Description of the Related Art An electron gun which emits an electron beam from a cathode heated to a high temperature in a vacuum and which has an electrode for controlling a current amount of the electron beam in the vicinity of the cathode is used as a cathode ray tube (CRT) or a signal of a television. It is widely used as an electron source for an amplifying element (traveling wave tube), and the cathode ray tube is extremely common as a color television or other picture tube.

An oxide cathode having an electron emission layer on a cathode substrate is generally used as a cathode for emitting electrons, and FIG. 4 shows a main part of this type of oxide cathode. Has been done.

In FIG. 4, a cathode cylinder 10 made of nickel-chromium alloy or the like is covered with a cap-shaped cathode substrate 12, and usually this cathode substrate 12 is made of nickel or the like. The electron emission layer 1 is formed on the surface of the cathode substrate 12.
4 is provided, and this electron emission layer 14 is, for example, barium,
It is composed of an oxide in which strontium and calcium are mixed, and usually barium functions as an electron emitting substance.

A heater 16 for heating the cathode is arranged in the cathode tube 10.

The cathode of FIG. 4 is shown as a main part of any one of three electron guns used in a color television picture tube, and the cathode 1 having the above-mentioned structure is shown.
7 is provided with a current control electrode 18 and an acceleration electrode 20 in the vicinity of the electron emission layer 14 to control the amount of current of the electron beam 22 emitted from the electron emission layer 14. Of course, the accelerating electrode 20 can be configured in multiple stages. As is well known, in the electron gun, the cathode 17 and the electrodes 18 and 20 are integrally connected by a support (not shown), and the electron gun is constructed by enclosing the cathode 17 and the electrodes 18 and 20 in a vacuum tube. A picture tube such as a color television is formed by arranging the fluorescent light emitting portion at the other end. Although the structure of the entire picture tube is well known, it is not shown, but it is natural to provide a deflection mechanism, a shadow mask, and the like for causing the electron beam 22 to collide with a predetermined fluorescent portion of the fluorescent light emitting portion in a predetermined scanning state. .

Although an oxide cathode is shown in FIG. 4, in recent years, an impregnated cathode has also been used, and has an advantage that a large amount of current can be obtained as compared with the oxide cathode. .

This impregnated cathode has a structure in which tungsten powder having a particle size of several microns is sintered to form a porous plate, and the porous plate is impregnated by melting an electron emitting substance at a high temperature. A mixture of barium oxide, calcium oxide and aluminum oxide is used as the basic constituent material of the electron emitting substance. This impregnated cathode has the advantage that it can be used at higher current densities than oxide cathodes, but on the other hand the operating temperature must be raised, and in the usual case, good electron emission will be obtained when heated to 1000 ° C or higher. Radiation can occur.

[0009]

Although the conventional electron gun and picture tube have the above-mentioned structure, there is a problem that grid emission (unnecessary electron emission) is likely to occur. This grid emission is caused by the fact that an electron emitting substance such as barium is vapor-deposited from the surface of the cathode 17, especially from the surface of the electron emission layer 14 on the electrodes 18 or 20 which are arranged in the vicinity of the cathode 17 and are opposed to each other with a narrow interval. In FIG. 4, it is understood that vapor deposition layers 18b and 20b of an electron emitting material are formed in the electron beam passage openings 18a and 20a of the current control electrode 18 and the acceleration electrode 20, respectively. Such vapor-deposited layers 18b and 20b are inevitably generated during high-tone heating of the cathode 17 in the manufacturing process and operating state of the electron gun or picture tube, and it is difficult to prevent such vapor deposition. Then, in the operating state of the electron gun, the respective electrodes 18, 20 become high in temperature due to radiant heat or conductive heat due to heating of the cathode 17, so that the vapor deposition section 1
8b and 20b are weak, but the chain line 30a or 3
Grid emission indicated by 0b occurs.
Particularly, in the impregnated cathode, such a grid emission often occurs due to its high operating temperature.

When such grid emissions 30a and 30b are generated, a floating electron beam is formed with respect to the intrinsic electron beam 22, which causes remarkable image quality disturbance in the case of a picture tube. This image quality disturbance causes a defect that a floating image is generated on the screen in a high quality picture tube such as a computer display. Further, even in a normal picture tube, there is a drawback that an afterimage is generated when the cutoff voltage is adjusted.

The present invention has been made to solve the above problems, and an object thereof is to provide an electron gun or electron tube having an electrode capable of effectively suppressing unnecessary electron emission.

[0012]

In order to achieve the above object, the present invention forms an electrically insulating oxide film on at least the surface of the electrode located near the cathode at the vicinity of the electron beam passage opening. It is characterized by

In the present invention, this oxide film is preferably a metal oxide film, particularly preferably silicon or aluminum oxide or a composite oxide thereof.

[0014]

According to the present invention, as described above, the electrode film in the vicinity of the cathode is provided with the electrically insulating oxide film, and as a result, even if the electron emitting substance is vapor-deposited from the cathode to each electrode, Since the supply of electrons from each electrode to the vapor-deposited electron emitting material is cut off, after the initial grid emission from the vapor deposition section occurs for a very short time, the electron emission from the vapor deposition section continues any longer. It is possible to effectively suppress the generation of grid emission.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

A preferred embodiment of the electron gun according to the present invention is shown in FIG. 1 as an enlarged view of a main part, and the same members as those in FIG.

A characteristic of the present invention is that each electrode 1
This is because an oxide film having electrical insulation is formed on the surfaces of 8 and 20, and in the illustrated embodiment, the oxide film 40 is formed in the vicinity of the electron beam passage openings 18a and 20a of the electrodes 18 and 20, 42 is formed. In the usual case, the formation of the vapor deposition portions 18b and 20b is likely to occur in the vicinity of the cathode 17, particularly the electron emission layer 14, and hardly occurs in the region away from this, so that in the embodiment, as described above, the openings 18a and 20b are formed. The oxide coatings 40 and 42 are formed only in the vicinity of 20a. Of course, in the present invention, it is possible to form such an oxide film on the entire surface of each electrode 18, 20.

In the examples, ceramics obtained by sintering metal oxides are suitable as the oxide, and particularly silicon (S
It is preferable to use oxides of i) or aluminum (Al) alone or in combination. As the silicon oxide, for example, SiO, SiO ₂ , SiO ₃ or the like is used, and as the aluminum oxide, AlO or AlO.
₂ , Al ₂ O ₃ (alumina) and the like are preferable.

In the present invention, such a sintered ceramic of a metal oxide has extremely stable chemical characteristics and further has heat resistance, so that it is not deteriorated even at a high temperature in the manufacturing process. There is an advantage that it does not occur.

In the present invention, the electrodes 18, 2 are thus
By forming an oxide film having an electrically insulating property on the surface of No. 0, grid emission can be effectively suppressed even when an electron emitting substance such as barium is vapor-deposited from the cathode 17 to each of the electrodes 18 and 20. it can.

In FIG. 1, as in the conventional case, the vapor deposition section 18
b and 20b are formed on the surfaces of the electrodes 18 and 20, respectively. As described above, in the present invention, since the vapor deposition portions of the electrodes 18 and 20 are covered with the oxide coatings 40 and 42, the vapor deposition portions 18b and 20b. Also formed on the oxide coatings 40, 42. As described above, the grid emission causes deterioration of image quality as unnecessary electron emission from the vapor deposition parts 18b and 20b, but the electron emitting substance such as barium vapor deposited will perform such floating electron emission after initial floating electron emission. In order to continue the above, it is necessary to receive an electron supply, and in the related art, since it is directly deposited on the surfaces of the electrodes 18 and 20, it is possible to directly and easily receive an electron supply from each electrode 18, 20. Grid emissions will continue without interruption.

However, in the present invention, the vapor-deposited portions 18b and 20b are provided with the electrically insulating oxide coatings 40 and 4b.
As a result of being deposited on the surface 2, the floating electron emission is quickly terminated because it can no longer receive an electron supply shortly after the initial electron emission ends. Therefore, according to the present invention, even if vapor deposition occurs on the electrode, it becomes possible to suppress the grid emission to a negligible amount.

FIGS. 2 and 3 are experimental examples showing the effect of suppressing the grid emission by forming an oxide film on the electrode according to the present invention. The electron current is actually measured and displayed in computer graphics.

In the figure, the aperture 18 of the current control electrode 18 is shown.
In order to compare the suppression effect, a silicon oxide film 40 is formed only in the upper half portion in the vicinity of a as shown in FIG.
As a result of arranging this electrode 18 in the vicinity of the cathode and aging at 1200 ° C. for 2 hours, as shown in FIG.
A vapor deposition portion 18b was formed near a.
FIG. 3 is a view seen from the direction of arrow A in FIG. 2. The vapor deposition portion 18b is on the coating film 40 where the oxide coating film 40 is formed, and on the half portion where the oxide coating film 40 is not sputtered. Are directly deposited on the electrode 18.

The electron emission distribution on the electron beam exit side of the electrode 18 was measured in this manner.
As shown in FIG.
In the absence of light, a low level of grid emission is observed as indicated by reference numeral 200, whereas in the portion where the oxide film 40 is applied, almost no such grid emission can be observed, and the grid emission from the cathode is not observed. Only the intrinsic electron beam was observed.

Therefore, the effect of the oxide film of the present invention can be confirmed from the experimental examples shown in FIGS.

Although the oxide cathode has been described in the above-mentioned embodiment, the effect of suppressing the grid emission due to the oxide coating can be similarly obtained in the impregnated cathode.
In particular, in the impregnation type electrode, since the operating temperature is high, the effect of the present invention is more remarkable.

[0028]

As described above, according to the present invention,
Even if vapor deposition of the electron emitting substance from the cathode to the neighboring electrode occurs,
The grid emission from the vapor deposition section can be remarkably suppressed, the characteristics of the electron beam emitted from the electron gun can be improved, and the image quality of the picture tube can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of an electron gun having an electrode coated with an oxide film according to the present invention.

FIG. 2 is a diagram showing an electron beam distribution in an electrode part showing an experimental example for observing the effect of the present invention.

3 shows an arrow A in FIG. 2 to show the effect of the present invention.
It is a figure of the electron beam distribution seen from the direction.

FIG. 4 is an enlarged sectional view of a main part of a conventional electron gun.

[Explanation of symbols]

 17 Cathode 18 Current Control Electrode 18a Opening 18b Vapor Deposition Section 20 Accelerating Electrode 20a Opening 20b Vapor Deposition Section 40, 42 Oxide Coating 22 Intrinsic Electron Beam

Claims (5)

[Claims] 1. An electron gun including a cathode that emits an electron beam and an electrode that is provided in the vicinity of the cathode and has an opening through which the electron beam passes and that controls the electron beam. At least an opening of the electrode. An electron gun having an electrically insulating oxide film formed in the vicinity thereof. 2. The electron gun according to claim 1, wherein the oxide film is a metal oxide film. 3. The electron gun according to claim 2, wherein the metal oxide film is silicon (Si) or aluminum (Al).
An electron gun characterized by being an oxide film of. 4. The electron gun according to claim 2, wherein the metal oxide film is a composite oxide film of silicon (Si) and aluminum (Al). 5. An electron gun including a cathode for emitting an electron beam and an electrode for controlling the electron beam, the electrode being provided in the vicinity of the cathode and having an opening through which the electron beam passes, the electron gun being a vacuum tube. An electron tube, which is disposed at one end of a body and has a fluorescent light emitting portion provided at the other end of the vacuum tube body, characterized in that an oxide film having an electrically insulating property is formed at least in the vicinity of the opening of the electrode. Electron tube.