JPH05174701A - Cathode structure - Google Patents

Abstract

PURPOSE:To materialize the long life of a cathode structure without its loss due to useless evaporation of magnesium by providing a high melting point metal layer where magnesium is hard to diffuse by heat on the rear surface of a cathode basic body. CONSTITUTION:A high melting point metal layer 14 consisting of tungsten is formed on the rear surface of a cathode basic body 12 by sputtering method. Then, an emitter layer 13 is formed by applying O layer of 50:40:10mol.% (Ba, Sr, and Ca) on the other face. It turns out that the magnesium inside the basic body 12 is restrained from evaporating from the rear surface side by providing a layer 14. Therefore, most magnesium staying inside the basic body 12 reacts upon the oxide of the layer 13 on the main surface, of the basic body 12 so it turns out that a material capable of contributing to emission may be generated. Therefore, any loss due to useless evaporation of magnesium can be eliminated so the long life can be materialized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode assembly, and to an improvement of the cathode substrate.

[0002]

2. Description of the Related Art In a cathode assembly which is a constituent member of an electron gun, an emitter layer made of, for example, (Ba, Sr, Ca) O is generally formed on a main surface of a cathode substrate containing nickel as a main component and magnesium. (JP-A-63-314741, IEICE Technical Report 8
2, 49-56 (82)).

The reason why the cathode substrate contains magnesium is that it reacts with barium oxide in the emitter layer, and barium generated by this reaction contributes to emission.

[0004]

However, according to the cathode assembly having such a structure, the magnesium contained in the cathode substrate evaporates from the back surface side of the cathode substrate during its use. I had left.

For this reason, magnesium is consumed more quickly without contributing to electron emission, resulting in a shorter life.

Therefore, the present invention has been made under such circumstances, and an object thereof is to provide a cathode assembly having a long life.

[0007]

In order to achieve such an object, the present invention is basically applied to a cathode substrate containing nickel as a main component and magnesium and a main surface of the cathode substrate. In the cathode structure composed of oxide,
A refractory metal layer in which magnesium is less likely to thermally diffuse is provided on the back surface.

[0008]

In the thus constructed cathode assembly, the refractory metal layer in which magnesium is less likely to diffuse is provided on the back surface of the cathode substrate, so that the magnesium in the cathode substrate is prevented from evaporating from the back surface side. Will be.

For this reason, most of the magnesium in the cathode substrate reacts with the oxide on the main surface of the cathode substrate,
It becomes possible to produce materials that contribute to emissions.

Therefore, magnesium is prevented from being unnecessarily evaporated and worn away, so that the life can be extended.

[0011]

FIG. 2 is a partially cutaway view showing an embodiment of a color cathode ray tube to which the cathode structure according to the present invention is applied.

In the figure, a face panel 21, a phosphor film 22, a shadow mask 23, and an electron gun 25 are sequentially arranged from the image plane side. A funnel 26 is provided so as to be closed from the side of the face panel 21 and include the electron gun 25 therein.

Here, the electron beam 27 emitted from the electron gun 25 is deflected by the magnetic field of the deflection yoke arranged on the outer surface of the funnel 26, passes through the shadow mask 23 and is applied to the phosphor film 22. It has become so.

FIG. 3 is a perspective view showing an embodiment of the electron gun 25 shown in FIG.

The electron gun 25 is a blue electron gun 25 having the same structure.
B, a red electron gun 25R, and a green electron gun 25G,
Each electron gun is arranged such that its central axis is positioned at each vertex of an equilateral triangle.

Each of these electron guns is fixed by a glass support bead 28, and a convergence magnetic pole 29 is provided on the phosphor film 22 side (front portion) thereof, and at the rear portion thereof. It has a base.

FIG. 4 is a perspective exploded view showing the blue electron gun 25B shown in FIG. 3, for example. The first grid G ₁ , the second grid G ₂ , the third grid G ₃ , and the fourth grid G ₄ each having a cylindrical shape are arranged so that their central axes coincide with each other, and the present embodiment is provided in the first grid G ₁ . In the example, a particularly improved cathode structure 1 is incorporated,
Further, a heater 2 is built in the cathode structure 1.

FIG. 1 is a sectional view showing a more detailed structure of the cathode assembly 1 and a heater 2 incorporated in the cathode assembly 1.

In the figure, there is a cylindrical body 11 made of, for example, nichrome, which is arranged so as to coincide with the center line of the electron gun. Inside this cylindrical body 11, a heater 2 is arranged. A cathode substrate 12 is arranged in the front part of the cylindrical body 11.

The cathode substrate 12 contains, for example, nickel (Ni) or nickel-tungsten (W) as a main component, and a reducing metal such as magnesium (Mg) or silicon (Si) in an amount of 0.01 to 0.1. It is configured to contain in the range of weight percent. here,
These reducing metals composed of magnesium and silicon are added to reduce BaO in the emitter layer 13 described later to generate Ba.

Then, the cathode substrate 1 thus constructed
An emitter layer 13 is formed by coating on the surface (main surface) located on the front side of 2.

The material of the emitter layer 13 is (B
a, Sr, Ca) O, and has a diameter of 1 to 2 μm and a length of 10 to 15 μm. In addition, (Ba,
Sr, Ca) O should be (B
It is obtained by thermal decomposition by heat during the heat treatment in which the material consisting of a, Sr, Ca) CO ₃ is added in the vacuum evacuation process of the electron tube.

Further, a refractory metal layer 14 made of, for example, tungsten (W) is formed on the back surface of the cathode base 12, and the refractory metal layer 14 made of tungsten is formed of magnesium from the cathode base 12. It is provided as a metal layer that makes heat diffusion difficult. Therefore, for such reasons, the metal layer is not necessarily limited to tungsten, and may be a metal layer made of molybdenum (Mo), tantalum (Ta), rhenium (Re), or the like.

In the cathode assembly 1 having such a structure, for example, a cathode substrate having a thickness of 0.15 mm is heated to about 450 ° C. and one surface of the cathode substrate is sputtered to a thickness of about 0.01 mm. Forming a tungsten layer,
Then, a 50:40:10 mol% (Ba, Sr, Ca) O layer having a thickness of about 0.09 mm can be applied and formed on the other surface.

According to the cathode assembly 1 thus constructed,
On the back surface of the cathode substrate 12, for example, a tungsten layer 14 is formed.
As described above, since the refractory metal layer in which magnesium is difficult to diffuse is provided, the magnesium in the cathode substrate 12 is suppressed from evaporating from the back surface side.

Therefore, most of the magnesium in the cathode substrate 12 reacts with the oxide of the emitter layer 13 on the main surface of the cathode substrate 12 to produce a material that contributes to emission.

Therefore, the magnesium is prevented from being uselessly evaporated and worn away, so that the life can be extended.

According to the cathode assembly constructed as in the above-mentioned embodiment, a decrease in electron emission was observed after about 1,500 hours at an operating temperature of about 850 ° C., whereas it was about 5,5.
It was found that the time could be extended to 00 hours. In addition, as a result of X-ray analysis, diffusion of magnesium into the tungsten layer was recognized, but it was found that it did not reach the surface of the tungsten layer, and a sufficient effect of suppressing thermal diffusion of magnesium was confirmed.

[0029]

As described above, according to the cathode assembly of the present invention, the life can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a cathode assembly according to the present invention.

FIG. 2 is a partially cutaway configuration diagram showing an embodiment of a color blanket tube to which the present invention is applied.

3 is a perspective configuration diagram showing an embodiment of the electron gun shown in FIG. 2. FIG.

4 is a perspective exploded view showing an embodiment of a blue electron gun of the electron gun shown in FIG. 3. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cathode structure, 2 ... Heater, 12 ... Cathode base, 13 ... Emitter layer, 14 ... Tungsten layer.

Claims (1)

[Claims] 1. A cathode structure comprising a cathode substrate containing nickel as a main component and containing magnesium, and an oxide coated on the main surface of the cathode substrate, wherein a refractory metal layer in which magnesium is less likely to thermally diffuse is formed on the back surface. A cathode structure characterized by being provided.