JP2001256881A - Cathode support structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode support structure capable of preventing deposition of an emitter evaporating from a cathode base on the flare of a cathode holding cylinder. SOLUTION: A reflector 14 having a flare 14a which obstructs pass of emitter evaporating from a cathode base body 8 toward the flare surface of a cathode holding cylinder 2 is installed in a cathode structure 15. The flare 14a obstructs the emitter passing from the cathode base body 8 toward the flare part of the cathode holding cylinder 2 to prevent generation of unnecessary thermionic emission from the flare part of the cathode holding cylinder 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode support structure used for a cathode ray tube or the like, and more particularly, to a highly reliable cathode support structure for a cathode ray tube having greatly improved insulation characteristics between electrodes.

[0002]

2. Description of the Related Art An electron gun structure provided in a cathode ray tube includes:
For example, there is a configuration shown in FIG. This figure shows the structure near the cathode structure in the electron gun structure.

In FIG. 1, A is an electron gun structure, and B is a cathode support structure. 1 is a support frame, and Fe
A plane formed of a Ni alloy or the like and having an upper surface portion and a lower surface portion opened has a substantially oval shape. Inside the support frame 1, a plurality of cathode holding cylinders 2 provided with a flare at the upper end and a heater connector support member 3 are arranged side by side at a predetermined interval. The member 3 is integrally fixed to the support frame 1 by an insulating support 4 made of crystallized glass or the like. A cathode structure 5 is mounted inside the cathode holding cylinder 2. Thereby, the cathode support structure B is configured.

[0004] Reference numeral 6 denotes a first grid formed of metal and having a cup shape with an open lower surface. This first
A cathode support structure B, that is, the support frame 1 is fitted inside the grid 6 to form an electron gun structure A.

Next, the structure of the cathode assembly 5 will be described with reference to FIG.

In FIG. 1, reference numeral 7 denotes a cathode sleeve, 8 denotes a cathode base, and 9 denotes a heater. The cathode sleeve 7 is formed of a cylindrical body whose upper end and lower end are open, and is formed of, for example, tantalum, and has dimensions of an outer diameter of 1.3 mm and a thickness of 20 μm.
m, length 5.0 mm. The inner peripheral surface of the cathode sleeve 7 is coated with a blackening layer made of alumina and heat-resistant metal powder. A cup 10 made of tantalum is fitted and fixed to the upper end opening portion of the cathode sleeve 7, and a disk-shaped impregnated cathode base 8 is fitted and fixed to the cup 10.

The impregnated cathode substrate 8 is made of porous tungsten having a porosity of about 20%, and has a molar ratio of 4: 1:
1. An emitter (electron emitting substance) composed of BaO, CaO, and Al ₂ O ₃ is melt-impregnated in a high-temperature hydrogen atmosphere or in a vacuum, and the surface is coated with a metal film such as an Ir or Os-Ru alloy. is there.

A coiled double helical type heater 9 is inserted and arranged inside the cathode sleeve 7. An electrode connection tab 11 is fixed to the lower end of the heater 9 by laser welding. The cathode sleeve 7 is made of Fe-Co-Ni.
It is arranged coaxially inside a cylindrical cathode holder 12 made of an alloy or the like. The strip-shaped toslap 13 formed of three tantalums disposed around the cathode sleeve 7 has its upper end fixed to the cathode holder 12 and its lower end fixed to the cathode sleeve 7 by laser welding.
Thereby, the cathode sleeve 7 is supported by the cathode holder 12.

Reference numeral 14 denotes a cylindrical reflector formed of a Ni-W alloy. This reflector 14 is coaxially arranged between the cathode sleeve 7 and the cathode holder 12 and is fixed to the upper end of the cathode holder 12.

The cathode structure 5 constructed as described above is inserted into the inside of the cathode holding cylinder 2 from its lower opening, and is fixed to the lower end of the cathode holding cylinder 2 by laser welding. Thereby, it is fixed to the cathode holding cylinder 2. At this time, the distance between the cathode base 8 and the first grid 6 is accurately set from the electron beam passage hole 6a formed in the first grid 6 by a method such as an air microphone opening method, a capacitance method, or a laser method. .

The thus constructed electron gun structure A is assembled to an electron gun in combination with another grid, and mounted inside the neck of the cathode ray tube. Thereafter, a required evacuation step and aging step are performed to complete a cathode ray tube.

Such an electron gun assembly A is suitable for forming a relatively small in-line type electron gun, and has a smaller number of components compared to a conventional type in which three electron gun assemblies are separated. It is more often used because of its advantages.

However, the electron gun structure and the cathode support structure thus configured have the following problems. Generally, after the cathode assembly is assembled in a cathode ray tube, the electron emission ability is stabilized through an exhausting and aging process. In these steps, a heater voltage higher than the rated voltage is applied. as a result,
The temperature of the cathode substrate becomes high, and the evaporation of the emitter from the cathode substrate is accelerated. The evaporated emitter (mainly Ba) is completely shielded by the flare provided at the upper end of the cathode holding cylinder and is deposited on the insulating board, thereby impairing the insulation characteristics between the first grid and the cathode and between the cathodes. Never. However, the evaporated emitter also deposits on the upper part of the flare provided at the upper end of the cathode holding cylinder. During operation, the temperature of the flare rises to about 300 ° C., so that unnecessary thermoelectron emission is generated from this part, causing insulation failure between the cathodes.

This phenomenon is remarkable during the life, reaches a maximum during a certain operation time, and thereafter continues to increase slightly with time without decreasing. Therefore, the video signal input to the cathode is disturbed, which is a fatal problem particularly when the drive voltage difference between the cathodes is large. In the case of the impregnated cathode, the operating temperature is about 200 ° C. higher than that of the oxide cathode, so that much emitter evaporation occurs and the problem due to insulation failure between the cathodes appears more prominently.

Unwanted electron emission between the cathodes greatly depends on the distance between the flares. However, when the flares are widened, the effect of preventing evaporation on the insulating plate is reduced, and the insulation characteristics between the first grit and the cathode are deteriorated. In addition, in the case of a low-power compact cathode assembly, it is not possible to reduce unnecessary electron emission to a degree that does not cause a problem by expanding the interval between flares to completely suppress the evaporation of the emitter onto the insulating plate. Difficult.

The following countermeasures have been studied for this problem.

As a first method, there is a method of thinly coating a metal having an effect of diffusing and absorbing BaO and Ba, such as Au, Ag and Pt, on the upper surface of the flare of the cathode holding cylinder. However, it is difficult to form a uniform coating film by this method, and the expected effect cannot be obtained. In addition, it leads to an increase in cost, and practical application is difficult.

As a second method, it is conceivable to lower the temperature of the flare portion of the cathode holding cylinder. However, the temperature of the flare portion of the cathode holding cylinder is substantially determined by the power supplied to the cathode heater if the diameter of the electron gun is the same. Therefore, it is difficult to lower the temperature to 200 ° C. or less even with a low-power 2-watt cathode having the smallest neck diameter at present.

The electron emission from the emitter evaporated on the upper part of the flare of the cathode cylinder is thermionic emission, and greatly depends on the work function of the evaporated emitter, the temperature of the flare part, the impurity element and concentration of the underlying metal, the distance between the flare and the like. Therefore, even if the measures described above can reduce the amount of thermionic emission, they cannot be prevented.

[0020]

As described above,
In the conventional cathode support structure, unnecessary thermoelectron emission occurs from an emitter deposited on the upper part of the flare of the cathode holding cylinder, and insulation failure between cathodes occurs. In particular, in the case of a power saving type impregnated type cathode, the operating temperature is considerably higher than that of an oxide cathode, which appears as a more prominent problem.

This phenomenon remarkably progresses during life, reaches a maximum during a certain operation time, and thereafter continues to increase slightly with time without decreasing. Therefore, the video signal input to the cathode is disturbed, which is a fatal problem particularly when the drive voltage difference between the cathodes is large.

Further, it is difficult to predict the amount of unnecessary electron emission because it depends on the temperature variation of the cathode, the work function of the deposition emitter, the temperature variation of the flare portion, the dimensional accuracy between the flares, and the like. Since the operating temperature of the type cathode is about 200 ° C. higher than that of the oxide cathode, the evaporation of the emitter is large, and the above-mentioned phenomenon is remarkably exhibited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a cathode support structure in which an emitter evaporating from a cathode base is reliably prevented from being deposited on a flare of a cathode holding cylinder to improve reliability. The purpose is to provide.

[0024]

In order to achieve the above object, a cathode support structure according to the present invention comprises a substantially elliptical metal support frame and a heater fixing terminal fixed to the metal support frame by an insulating support. A cathode holding cylinder fixed to the metal support frame by an insulating support and having a flare at an upper end, a cathode assembly mounted in the cathode holding cylinder and having a cathode base at an upper end, and attached to the cathode assembly A reflector having a flare for blocking an emitter evaporating from the cathode base against a flare surface of the cathode holding cylinder.

In the present invention, the flare provided above the reflector can prevent the emitter evaporated from the cathode base from being deposited on the upper flare of the cathode holding cylinder, and the temperature of the flare rises during operation. Also, unnecessary thermoelectron emission does not occur from this portion, and insulation failure between the cathodes can be prevented.

[0026]

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

FIG. 1 shows the structure of a cathode structure incorporated in a cathode support structure according to one embodiment of the present invention.

In the figure, 7 is a cathode sleeve, 8 is a cathode base, and 9 is a heater. The cathode sleeve 7 is formed of a cylindrical body whose upper end and lower end are open, and is formed of, for example, tantalum, and has dimensions of an outer diameter of 1.3 mm and a thickness of 20 μm.
m, length 5.0 mm. The inner peripheral surface of the cathode sleeve 7 is coated with a blackening layer made of alumina and heat-resistant metal powder. A cup 10 made of tantalum is fitted and fixed to the upper end opening of the cathode sleeve 7, and a disk-shaped impregnated cathode base 8 is fitted and fixed to the cup 10.

The impregnated cathode substrate 8 is made of porous tungsten having a porosity of about 20% and has a molar ratio of 4: 1:
(1) An emitter (electron emitting material) composed of BaO, CaO, and Al ₂ O ₃ is melt-impregnated in a high-temperature hydrogen atmosphere or in a vacuum, and its surface is coated with a metal film such as an Ir or Os-Ru alloy. .

Inside the cathode sleeve 7, a coiled double helical type heater 9 is inserted and arranged. An electrode connection tab 11 is fixed to the lower end of the heater 9 by laser welding. The cathode sleeve 7 is made of Fe-Co-Ni.
It is disposed coaxially inside a cylindrical cathode holder 12 formed of an alloy or the like. The strip-shaped toslap 13 formed of three tantalums disposed around the cathode sleeve 7 has its upper end fixed to the cathode holder 12 and its lower end fixed to the cathode sleeve 7 by laser welding. Thus, the cathode sleeve 7 is supported by the cathode holder 12.

Reference numeral 14 denotes a cylindrical reflector formed of a Ni-W alloy. A flare portion 14 a is formed at the upper end of the reflector 14. This reflector 14 is coaxially arranged between the cathode sleeve 7 and the cathode holder 12 and is fixed to the upper end of the cathode holder 12.

The cathode structure 15 configured as described above is
As shown in FIG. 2, the cathode holding cylinder 2 provided in the same cathode support structure B as that of the related art is inserted into the cathode holding cylinder 2 from its lower opening, and the cathode holder 12 is attached to the cathode holding cylinder 2.
Is fixed to the cathode holding cylinder 2 by being fixed to the lower end portion by laser welding. At that time, the first grid 6
The distance between the cathode base 8 and the first grid 6 is accurately set by a method such as an air microphone opening method, a capacitance method, or a laser method from the electron beam passage hole 6a formed in the above.

The thus constructed electron gun assembly A is assembled with another grid to assemble the electron gun, and is mounted inside the neck of the cathode ray tube. Thereafter, a required evacuation step and aging step are performed to complete a cathode ray tube.

Next, the operation of the flare portion 14a of the reflector 14 attached to the cathode assembly 15 will be described with reference to FIG. FIG. 3 is an enlarged view of a main part of FIG.

In general, evaporation of the emitter in the electron tube may be regarded as going straight. In the case of a conventional cathode structure, the cathode base 8
The emitter evaporating from the outermost peripheral portion A goes straight along the line Y and deposits on the flare portion B of the cathode holding cylinder 2. On the other hand, in the case of the present embodiment, since the flare portion 14a is provided on the upper portion of the reflector 14 attached to the cathode structure, the emitter evaporated from the outermost peripheral portion A of the cathode base 8 is discharged from the flare portion 14a. It goes straight along the line X connecting the outermost point C and does not deposit on the flare portion B of the cathode holding cylinder 2.

That is, when the outer peripheral point A of the cathode base 8 is viewed from the outer peripheral point B of the cathode holding cylinder 2, the outer peripheral point A of the cathode base 8 is formed by the flare portion 14 a of the reflector 14.
Of the cathode base 8 is shielded by the flare portion 14a of the reflector 14, and the vapor deposition of the emitter on the flare B of the cathode holding cylinder 2 is prevented. . Therefore, even if the temperature of the flare rises during operation, thermionic emission from this part does not occur, and insulation failure between the cathodes can be prevented.

The setting of the outer diameter and height of the flare portion 14a of the reflector 14 is determined by the contact point D of the line Y connecting the outer peripheral point A of the cathode base 8 and the outer peripheral point B of the cathode holding cylinder 2. The outer diameter of the flare portion 14a of the reflector 14 may be located on the left side of the contact D, that is, set to be larger, and the height of the flare portion 14a may be appropriately set to a position above the contact D, that is, a higher position.

The positional relationship between the outer peripheral point A of the cathode base 8 and the outer peripheral point B of the cathode holding cylinder 2 differs depending on the size of the electron gun and the cathode assembly 15. The outer diameter and height can be set optimally.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications. For example, the flare 14a provided at the upper end of the reflector 14 is
The configuration is not limited to the configuration formed integrally with the reflector 14.
For example, as shown in FIG. 4A, the flare portion 14c is formed separately from the reflector 14, and the flare 14c is fitted to the outer peripheral side of the upper end of the reflector 14 and fixed by means such as welding. A structure or a structure in which the flare 14c is fitted to the inner peripheral side of the upper end portion of the reflector 14 and fixed by welding or the like as shown in FIG.
In the above-described embodiment, the embodiment of the impregnated cathode structure has been described, but the present invention can also be applied to an oxide cathode structure having a reflector.

[0040]

As described above, according to the present invention, the flare provided on the reflector can shield the emitter evaporated from the cathode base from being deposited on the upper flare portion of the cathode holding cylinder. Even if the temperature of the flare part rises, unnecessary thermionic emission does not occur from this part,
Poor insulation between the cathodes can be prevented.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a configuration of a cathode structure in a cathode support structure according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a cathode support structure in which the cathode structure of FIG. 1 is incorporated.

FIG. 3 is an enlarged view of a main part for explaining the operation of a flare section provided on a reflector of the cathode assembly of FIG. 1;

FIG. 4 is a diagram showing a modified example of the flare of the reflector according to the present invention.

FIG. 5 is a cross-sectional view showing a configuration of a conventional cathode assembly.

FIG. 6 is a partial cross-sectional view showing a configuration of a conventional cathode support structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Support frame 2 ... Cathode holding cylinder 3 ... Heater connector support 6 ... 1st grid 7 ... Cathode sleeve 8 ... Cathode base 9 ... Heater 10 ... Cup 12 ... Cathode holder 14 ... Reflector 14a ... Flare 15 ... Cathode structure

Continued on the front page (72) Inventor Eiichiro Uda 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in Toshiba Yokohama Office 5C031 DD15 DD20

Claims (1)

[Claims] A metal support frame having a substantially elliptical shape; a heater fixing terminal fixed to the metal support frame by an insulating support; a heater fixing terminal fixed to the metal support frame by an insulating support;
A cathode holding cylinder having a flare at an upper end thereof; a cathode assembly mounted in the cathode holding cylinder and provided with a cathode base at an upper end; and an emitter mounted on the cathode assembly and evaporating from the cathode base. And a reflector having a flare that blocks the flare surface of the cathode support structure.