JPH08315727A - Picture tube - Google Patents

Abstract

PURPOSE: To provide a cathode with excellent electron emission property in good reproducibility by bringing tungusten oxide into the thin film of an impregnated cathode and manually controlling the oxidation state of tungusten. CONSTITUTION: Cathode material 1 contains W porous base 2 with fixed porosity ratio and holes 3. The hole 3 are incorporated and impregnated with BaCo3 , CaCO3 , Al2 O3 as electron emission metarial at a preset mole ratio. Such pellets 1 are mounted on a Ta cup 4 and laser-welded to a Ta sleeve 5. Prior to vacuum sputtering evaporation, oxygen partial pressure in a container is kept at a preset value and measured while bringing high purity oxygen through a gas guide. In this way, W in a thin film 8 is oxidized. A cathode with the thin film formed of W and SC2 O3 is thus obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-definition picture tube using an impregnated cathode, which is drawing attention as a high current density cathode.

[0002]

2. Description of the Related Art A conventional impregnated cathode for a picture tube is disclosed in Japanese Patent Application Laid-Open No. 61-13526 (Japanese Patent Application No. 59-13314).
No. 9), a thin film composed of a refractory metal and Sc or an oxide of Sc or both of them was provided on the electron emission surface of the heat resistant porous substrate.

[0003]

In the above-mentioned conventional cathode, the thin film constituent elements, particularly the oxidation state of W, are not taken into consideration, and the degree of W oxidation changes depending on the vacuum atmosphere during thin film formation. It was

An object of the present invention is to artificially control the oxidation state of W.

[0005]

The above object is achieved by introducing an oxygen gas, an oxidizing gas such as water vapor, or a well-controlled oxidizing gas or vapor at the time of depositing a thin film in manufacturing the conventional cathode. The above object can also be achieved by using pre-oxidized W powder or a plate as a target during sputter deposition.

[0006]

The electron emission characteristics of the impregnated cathode are governed by the work function of the cathode surface. The work function is determined by the arrangement of atomic groups on the outermost surface of the cathode.

On the outermost surface of the cathode coated with a mixed thin film of W and Sc ₂ O ₃ , ideally, a monomolecular layer composed of Ba, Sc and O is mixed. The constituent elements of this monomolecular layer, Sc and O, are replenished from the coating mixed thin film, and Ba is replenished from the normal impregnated cathode of the base, and during the cathode operation, the supply and evaporation of these elements are in equilibrium and a steady state is achieved. Become.

Of these, O is an oxide of W in the thin film (W
It is supplied by the decomposition of O ₃ ) and Sc ₂ O ₃ . In particular, the presence of W oxide is indispensable because a large amount of O is required at the initial formation of the monolayer.

After the thin film is formed, the W oxide is easily formed on the surface by exposing the cathode to the atmosphere once, but the thickness of this oxide layer is extremely thin, and it cannot be a sufficient source of O 2 supply. The present invention controls and artificially forms the W oxide.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view schematically showing an impregnated cathode according to the present invention. In the figure, reference numeral 1 is a cathode material pellet (1.4φ), which is formed of a porous W substrate 2 and pores 3 having a porosity of 20 to 25%. As the porous substrate, Mo, Ir, Pt, Re or the like and alloys thereof may be used.

In the holes 3, BaCO is used as an electron emitting material.
Impregnation was carried out by mixing ₃ , CaCO ₃ and Al ₂ O ₃ in a molar ratio of 4: 1: 1. Note that materials having different molar ratios or electron-emitting materials to which different materials are added may be used.
The pellet 1 may be attached to the Ta cup 4, and then the Ta cup 4 may be laser-welded to the Ta sleeve 5. Instead of laser welding, a brazing material may be used. The heating of the cathode is performed using a heater 7 in which the W core wire 6 is coated with alumina. The above is the Ba supply source. The amount of replenishment of Ba depends on the heating temperature, but the molar ratio of the electron emission material is changed, or Zr, Hf, Ti, Cr, Mn, Si,
It can also be adjusted by including an activator such as Al. The Sc ₂ O ₃ W thick 10nm~1μm as makeup source and Sc ₂ O ₃ thin film 8 made from by adhering by vacuum sputtering deposition. Mo, Re, Pt, Ir, Ta instead of W
You may use metals, such as these, or these alloys.

Prior to the sputter deposition in vacuum, the oxygen partial pressure in the sputter deposition container is adjusted to 1 × 10 to ⁵ to 1 × 10 to ⁴ T.
orr and high purity (9
(9.9%) oxygen was introduced, and the partial pressure was measured by a small mass spectrometer mounted in the container.

By this operation, W in the thin film 8 can be oxidized. It is also possible to introduce oxygen at a partial pressure measured in advance during the sputter deposition to oxidize only a part of the thin film 8. As the introduced gas, an oxidizing gas other than oxygen can be used.

Using such a cathode, the width of the anode is 5 μS and the repetition is 10
Saturation current density was measured by applying a high-voltage pulse of 0 Hz. The result is shown in FIG.

Reference numeral 9 in the figure shows the characteristics of the cathode coated with a thin film of W and Sc ₂ O _{3 according} to the present invention.

In the figure, 10 is the characteristic of the cathode without the oxidation treatment of the thin film. In the figure, 11 indicates the characteristics of the cathode not coated with a thin film.

[0017]

According to the present invention, B is formed on the outermost surface of the cathode.
Since a monomolecular layer composed of a, Sc and O can be stably supplied, a cathode having excellent electron emission characteristics can be obtained with good reproducibility, and a high-definition picture tube can be realized.

[Brief description of drawings]

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

FIG. 2 is a diagram comparing electron emission characteristics of an impregnated cathode according to the present invention and a conventional impregnated cathode.

[Explanation of symbols]

1 ... Cathode pellet, 2 ... W substrate, 3 ... Hole, 4 ... T
a cup, 5 ... Ta sleeve, 6 ... W core wire, 7 ... Alumina coating, 8 ... Thin film, 9 ... Electron emission characteristics of impregnated cathode according to the present invention, 10 ... Conventional impregnated type in which thin film is not subjected to oxidation treatment Electron emission characteristics of cathode, 11 ... Electron emission characteristics of impregnated cathode without thin film coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Sasaki 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] 1. A step of preparing a heat-resistant porous body substrate impregnated with an electron-emitting substance containing barium, and at least one selected from the group consisting of scandium and scandium oxide on the surface of the heat-resistant porous body substrate. A cathode ray tube using an impregnated cathode manufactured by a manufacturing method, which comprises a step of forming a thin film made of tungsten and an oxide of tungsten. 2. The oxide of tungsten is obtained by oxidizing the tungsten in the thin film by introducing an oxidizing gas during the formation of the thin film. Picture tube. 3. The picture tube according to claim 1, wherein the oxide of tungsten is obtained by sputter deposition using pre-oxidized tungsten powder or a tungsten plate as a target. 4. The picture tube according to claim 1, wherein the thin film has a thickness of 10 nm to 1 μm.