JP2002093337A - Cathode ray tube - Google Patents

Abstract

An object of the present invention is to provide a cathode ray tube equipped with an electron gun having a cathode structure capable of obtaining high current density and stable electron emission performance for a long time. A cathode sleeve (52) having a base metal (53) holding an electron emission material (54A) containing a plurality of alkaline earth metal oxides containing barium as a main component, and a cathode sleeve (52) containing a heater (55) therein is provided. The metal 53 is mainly composed of nickel, contains a trace amount of a reducing element,
No. 4 contained a trace amount of antimony oxide 54B in a metal oxide 54A of barium, calcium, and strontium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor tube for OA equipment terminals, a cathode ray tube such as a cathode ray tube for a TV set including a projection type, and an image pickup tube for broadcasting. The present invention relates to a cathode ray tube provided with an electron gun having a highly reliable indirectly heated cathode structure.

[0002]

2. Description of the Related Art A cathode ray tube of this type, for example, a color cathode ray tube used for a monitor of an OA equipment terminal, generally has a panel coated with a phosphor, a neck for accommodating an electron gun, and a funnel for connecting the panel to the neck. Having a vacuum envelope consisting of

In the above-mentioned electron gun used for the cathode ray tube, an indirectly heated cathode structure is exclusively used as a cathode structure which is a component of the electron gun. The indirectly heated cathode structure is roughly classified into an oxide cathode structure in which a thermionic emission material is directly applied on a base metal body, and an impregnated cathode structure in which a thermoelectron emission material is impregnated in a high-melting metal porous substrate. It has been known.

FIG. 8 is a cross-sectional view of a main part showing an indirectly heated cathode structure constituting an electron gun of a cathode ray tube and a structure in the vicinity thereof, in which an oxide is used as a thermoelectron emitting material. In FIG. 8, reference numeral 51 denotes an indirectly heated cathode structure. The indirectly heated cathode structure 51 includes a cylindrical cathode sleeve 52.
A cap-shaped base metal 53 fixed to one end of the cathode sleeve 52; an electron-emitting material layer 54 applied to the top surface of the base metal 53;
2 has a heater 55 for heating whose part is arranged.

In the heater 55, a part of a heating core wire 55a wound spirally is covered with an insulating film 55b containing alumina as a main component and a coating film 55c containing alumina and tungsten fine powder. That is, the insulating film 55b of the insulating film 55b and the coating film 55c is the heating core wire 55 of the heater 55.
The coating film 55c extends from the top coil portion 55f so as to cover almost the entire area except the vicinity of the welding end 55d outside the insulating film 55b except for the welding end 55d except for the welding end 55d. The cathode sleeve 52 is attached to an end portion 55g located further outside the widened lower end 52a of the cathode sleeve 52.

The coating film 55c is a black coating film containing a small amount of tungsten powder and exhibiting a black color as described above, and the insulating film 55b is a white insulating film exhibiting a white color because it contains alumina as a main component. The heater is generally called a dark heater because its appearance is black when the entire heater is viewed.

On the other hand, the heater 55 is welded and fixed to the heater support 56 at a welding end 55d. The cathode sleeve 52 is held by a cylindrical cathode support eyelet 57 and a cathode disk 58 having a small diameter portion fixed to the cathode sleeve 52 and a large diameter portion fixed to the cathode support eyelet 57. Through the bead support 59
The heater supports 56 are fixed to the multi-form glass 61 via heater lead straps 60, respectively.

Reference numeral 62 denotes a control electrode which forms an electron beam generating portion with the cathode and an acceleration electrode (second electrode) not shown. It is fixed to 61.

The base metal 53 constituting such an indirectly heated cathode structure contains nickel: Ni as a main component and a trace amount of a reducing element such as magnesium: Mg, silicon: Si, and zirconium Zr. The electron emission material 54 applied on the base metal 53 is made of an alkaline earth metal oxide containing barium: Ba.

[0010] In recent years, demands for power saving and energy saving are as follows.
It is only becoming stronger with the spread of personal computers and large TV monitors. On the other hand, the realization of a high current density of the electron beam and stable electron emission characteristics over a long period of time is required as the screen becomes larger and higher definition.

[0011]

However, in the cathode structure using the above-described electron emission material of an alkaline earth metal oxide containing barium, it is possible to sufficiently obtain stable electron emission at a high current density for a long time. It was one of the issues to solve this.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a cathode structure capable of obtaining a stable electron emission performance at a high current density for a long time, and to provide an electron gun using the same. It is to provide a cathode ray tube.

[0013]

In order to achieve the above object, the present invention provides an indirectly heated cathode structure constituting an electron gun of a cathode ray tube, comprising calcium: Ca, strontium Sr containing at least barium: Ba at one end. And the like, and containing a small amount of antimony oxide: Sb ₂ O ₃ (hereinafter, also referred to as addition).

The antimony oxide content is 0.01
wt% or more and less than 1.0 wt%.

By including a small amount of antimony oxide,
The electric conductivity of the electron emission material layer applied to the base metal is improved, and the electric resistance of the electron emission material layer is reduced. It is necessary that the content is practically not less than 0.01 wt%. If the content is too large, sintering occurs in the electron emission material layer, and the emission of the oxide cathode (electron emission) Function) is reduced. According to experiments conducted in consideration of securing the required amount of the required electron-emitting substance, the content of the antimony oxide is practically less than 1.0 wt% with respect to the electron-emitting substance.

As a result, it is possible to obtain high current density and stable electron emission performance for a long time.

The present invention is not limited to the above configuration and the configuration of the embodiment described later, and various modifications can be made without departing from the technical idea of the present invention.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The specific numerical values in the description of the embodiments are merely examples.

FIG. 1 is a schematic sectional view of a main part of an indirectly heated cathode structure for explaining one embodiment of a cathode ray tube according to the present invention. In the figure, 52 is a cathode sleeve, 53 is a base metal, 54 is an electron emission substance applied to the base metal 53, and 55 is a heater housed in the cathode sleeve 52.

The electron-emitting material 54 starts from an alkaline earth ternary carbonate containing barium: Ba and is decomposed to obtain a plurality of alkaline earth containing barium represented by the chemical formula (Ba, Ca, Sr) O. A metal oxide 54A contains a small amount of antimony oxide: Sb ₂ O ₃ fine powder 54B.

Base metal 53 holding electron emitting material 54
Has a thickness of 0.14 mm and a small amount of magnesium: Mg
And silicon: a cap member made of nickel containing a reducing agent such as Si.

The cathode sleeve 52 is a cylindrical member having the base metal 53 attached to one end (upper side in the figure), and has a total length of 7.5 mm and a thickness of 0.02 mm nickel-chrome (Ni-Cr). Made of alloy.

Antimony oxide: Sb ₂ O contained in the alkaline earth metal oxide 54A constituting the electron emitting material 54
The fine powder 54B of No. ₃ has an average particle size of 5 μm and a purity of 99%. Ba, Ca, Sr
A suspension of carbonate ((Ba, Ca, Sr) CO ₃ ) was added at 0.5 wt% and mixed, and a coating film layer of about 70 μm was formed on the top surface of the base metal 53 welded and fixed to the sleeve 52 using a spray gun. Form. Next, the sleeve 52
The heater 55 is inserted into the inside of the device to complete the oxide cathode.

The cathode structure of the present embodiment manufactured in this manner (denoted as the present oxide cathode in the figure) and a conventional cathode structure using an electron emitting material containing no antimony oxide (denoted as a known oxide cathode in the figure) Will be described below.

FIG. 2 is an explanatory diagram of a temperature change at the time of a cathode operation with respect to a cathode current. In the figure, A shows a case using the present oxide cathode, and B shows a case using a conventional (known) cathode. The vertical axis shows the temperature change (°
C), the horizontal axis shows the cathode current.

In this evaluation, the heater voltage was set to 6.3 V and the temperature of the electron emitting material 54 was set to 725 ° C. which is a normal operating condition.
After the desired value is set for b (Cb is the luminance temperature display) using an infrared radiation thermometer, the cathode current is increased, and the luminance temperature change of the electron-emitting substance 54 at each time is obtained.

As is apparent from FIG. 2, the operating temperature of the present oxide cathode to which a small amount of antimony oxide: Sb ₂ O ₃ is added is lower than that of the known oxide cathode, as the cathode current is increased. The phenomenon appears strongly.
When the cathode current is further increased to 2 mA or more, a transition to a so-called Joule heating phenomenon occurs.

However, the Joule heat of the present oxide cathode is smaller than that of the known oxide cathode, and works in the direction of suppressing the cathode temperature rise during operation.

FIG. 3 shows a heater voltage-cathode current characteristic showing a change of a cathode current with respect to a heater voltage of an oxide cathode containing a trace amount of antimony oxide (the present oxide cathode) and an oxide cathode not containing the same (known oxide cathode). FIG. FIG. 3A shows an initial operation, and FIG.
Indicates the operation after 2000 hours.

FIG. 3A shows the heater voltage-cathode current characteristics in the initial operation, and shows that both the present oxide cathode of the curve A and the known oxide cathode of the curve B show almost the same characteristics. Have been.

However, as shown in FIG.
After operating for 000 hours, the characteristic of the known oxide cathode shown by the curve B shows that a slump phenomenon (cathode current slows down) of the cathode current occurs from 4 V to 8 V due to the influence of gas. On the other hand, the occurrence of the above-described slump phenomenon of the cathode current is not observed in the present oxide cathode. This indicates that the present oxide cathode has good gas resistance.

FIG. 4 shows the electron emission when the oxide cathode containing a trace amount of antimony oxide (the present oxide cathode) and the oxide cathode not containing the same (known oxide cathode) are operated in a cathode ray tube for a long time. FIG. 4 is an explanatory diagram of a change over time in the performance.

The vertical axis of FIG. 4 shows the relative value of the electron emission ability when the initial electron emission ability of each cathode is 100, and the horizontal axis shows the cathode current and the current density of 3.5 A / cm ² (peak loading). The operation time when forced operation is performed is plotted in units of 500 hours.

As shown in FIG. 4, the oxide cathode shown by the curve A maintains an electron emission ability of more than 70% even after about 15000 hours. On the other hand, the known oxide cathode shown by the curve B decreases to 50% or less of the present oxide cathode over the same time.

The amount of antimony oxide added to the electron-emitting material constituting the oxide cathode is 0.01 to 1.0.
wt%. This range of the amount of addition can exert the above-mentioned effect with a so-called very small amount, and the basis for setting the above range to the above numerical value will be described.

FIG. 5 is an explanatory diagram showing the relationship between the amount of added antimony oxide and the resistance value of the oxide cathode. The abscissa indicates the amount of added antimony oxide (wt%), and the ordinate indicates the resistance value of the oxide cathode as a relative value.

The lower limit of the amount of antimony oxide (Sb ₂ O ₃ ) to be added, 0.01 wt%, is the lowest measurable value at which a change in the resistance value of the oxide cathode can verify the above effect. , And also the minimum value that can be detected by analysis.

On the other hand, if the addition amount is 1.0 wt% or more, sintering occurs in the electron emission material layer, and the electron emission ability of the oxide cathode is reduced, and the maximum is 1.0 wt%.

Therefore, the amount of antimony oxide added to the electron-emitting substance is in the range of 0.01 to 1.0 wt%, preferably 0.01 to 0.5 wt%.

As described above, it can be seen that the present oxide cathode containing a trace amount of antimony oxide has excellent electron emission characteristics as compared with a known oxide cathode containing no trace amount of antimony oxide.

FIG. 6 is a side view for explaining an example of the configuration of an electron gun used for a cathode ray tube. This electron gun includes a control electrode (first grid electrode: G1) 11, an acceleration electrode (second grid electrode: G2) 12, a focusing electrode (third grid electrode: G1).
G3, fourth grid electrode: G4, fifth grid electrode: G
5) 13, 14, 15, anode (sixth grid electrode: G
6) 16 and the shield cup 17 are arranged at a predetermined interval and a positional relationship in the pipe axis direction,
And a tab or lead wire provided on each electrode is welded to a stem pin 18a erected on the stem 18.

In this electron gun, a cathode structure 21 is arranged close to the stem 18 of the control electrode 11. In addition,
Reference numeral 19 denotes a valve spacer contact, which has a function of resiliently contacting the inner wall of the neck portion to make the center axis of the electron gun coincide with the tube axis, and applying an anode voltage to the electron gun from the funnel and the internal conductive film applied to the inner wall of the neck. Has a function to introduce.

The control electrode 11, the accelerating electrode 12, and the indirectly heated cathode structure 21 constitute an electron beam generator (three-pole part). The focusing electrodes 13 to 15 accelerate and focus the electron beam emitted from the electron beam generating unit, and the focusing electrode 15 and the anode 1
6 converges on a predetermined electron beam diameter by the main lens and is directed toward the fluorescent screen.

The stem 18 is welded to the open end of the neck of the vacuum envelope, and transmits an external signal or voltage to the stem pin 1.
A signal / voltage input terminal to be applied to each electrode via 8a.

FIG. 7 is a schematic sectional view for explaining a schematic structure of a shadow mask type color cathode ray tube as an example of a cathode ray tube according to the present invention, wherein 1 is a panel portion, 2 is a funnel portion, 3 is a neck portion, Is a phosphor screen formed by applying a phosphor on the inner surface of the panel portion, 5 is a shadow mask as a color selection electrode, 6 is a magnetic shield for shielding an external magnetic field (geomagnetism), and the trajectory of the electron beam is changed by the geomagnetism. To prevent Reference numeral 7 denotes a deflection yoke, 8 denotes a correction magnetic device for correcting mismatch between the electron gun and the phosphor due to a slight axis shift or rotation shift between the electron gun and the panel / funnel / shadow mask, and 9 denotes three electron beams. An electron gun provided with an indirectly heated cathode structure for emitting an electron beam represents one of three electron beams as a representative.

The three electron beams 10 from the electron gun 9 are modulated by video signals from an external signal processing circuit (not shown).
The light is emitted toward the fluorescent screen 4. The electron beam 10 is scanned two-dimensionally on the phosphor screen 4 by passing through horizontal and vertical deflection magnetic fields generated by a deflection yoke 7 provided in a transition region between the neck portion 3 and the funnel portion. The shadow mask 5 passes through a large number of apertures formed in the plane.
Each of the electron beams of the book is selected for each color to excite the corresponding phosphor on the phosphor screen to reproduce a required image.

By applying the above-described embodiment to the cathode structure constituting the electron gun of the color cathode ray tube, it is possible to obtain high current density and stable electron emission performance for a long time.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention described in the appended claims.

[0049]

As described above, according to the present invention,
It is possible to provide a cathode ray tube provided with an electron gun that realizes a high current density of an electron beam and a stable electron emission characteristic over a long period of time with an increase in screen size and definition.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of an indirectly heated cathode structure for explaining one embodiment of a cathode ray tube according to the present invention.

FIG. 2 is an explanatory diagram of a temperature change during a cathode operation with respect to a cathode current.

FIG. 3 is an explanatory diagram of a heater voltage-cathode current characteristic showing a change in a cathode current with respect to a heater voltage of an oxide cathode containing a small amount of antimony oxide and an oxide cathode not containing the same.

FIG. 4 is an explanatory diagram of a change over time in electron emission ability when an oxide cathode containing a trace amount of antimony oxide and an oxide cathode not containing the same are incorporated in a cathode ray tube and operated for a long time.

FIG. 5 is an explanatory diagram showing the relationship between the amount of antimony oxide added and the resistance value of an oxide cathode.

FIG. 6 is a side view illustrating a configuration example of an electron gun used in a cathode ray tube according to the present invention.

FIG. 7 is a schematic sectional view illustrating a schematic structure of a shadow mask type color cathode ray tube as an example of a cathode ray tube according to the present invention.

FIG. 8 is a cross-sectional view of a main part showing an indirectly heated cathode structure constituting an electron gun of a cathode ray tube and a structure in the vicinity thereof;

[Explanation of symbols]

 52 Sleeve 53 Base metal 54 Cathode 54A Electron emitting material 54B Antimony oxide 55 Heater.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikumitsu Nonaka 3300 Hayano, Mobara-shi, Chiba F-term in Hitachi Display Group (reference) 5C031 DD15

Claims (2)

[Claims] 1. An electron beam generated by a panel section having a phosphor screen formed by applying a phosphor on an inner surface thereof, and an electron beam generating section having an indirectly heated cathode structure, a control electrode and an acceleration electrode. A neck portion accommodating an electron gun having a plurality of electrodes that emit light toward the panel, and a deflection yoke for connecting the panel portion and the neck portion and scanning an electron beam emitted from the electron gun on a phosphor screen are provided. The indirectly heated cathode structure, which has a vacuum envelope constituted by a funnel portion, and constitutes an electron beam generating portion of the electron gun, mainly includes a plurality of alkaline earth metal oxides containing at least barium at one end. A cathode sleeve having a base metal holding an electron-emitting substance to be heated and containing a heater therein, and a holder supporting the cathode sleeve, wherein the base metal is mainly nickel. Min and, and also contains a reducing trace elements, the electron emission material may be a cathode ray tube, wherein barium, calcium, that containing antimony oxide of trace metal oxide of strontium. 2. The antimony oxide content is 0.01%.
2. The cathode ray tube according to claim 1, wherein the content is not less than 1.0 wt%.