JPH11204053A - Cathode for cathode-ray tube and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for reduction of an oxide, and to restrain peeling of the oxide from a base metal surface by finishing into a coarse face the surface of a cathode base body provided with the oxide as an electron radiation substance. SOLUTION: A cathode base body 17 consists of a cup-shaped molded nickel alloy, and contains a fine quantity of a reducer such as magnesium or tungsten. A top surface 17a thereof is processed by a relatively coarse abrasive using a general polishing machine to make a course face. A cathode sleeve 18 is fitted with an internal diameter of the cup of the cathode base body 17, and is bonded and fixed by laser welding. An alkaline earth metal oxide layer 19 such as barium, strontium or calcium is formed on the coarse top face 17a by spraying method. A bonding strength of the oxide layer 19 is increased with an increase in surface area due to coarse processing, and at the same time a reaction rate of the reducer and oxide included in the cathode base body 17 increases, and activation process time in an aging process is significantly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube cathode used for a cathode ray tube and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, an oxide cathode (oxide cathode) of an electron gun of a cathode ray tube uses an alloy mainly composed of nickel as a cathode base metal and containing a small amount of a reducing agent such as magnesium or tungsten. The cathode base metal made of the above alloy is press-formed into a required shape, and is joined and fixed to the tip of the cathode sleeve. An alkaline earth metal carbonate powder containing barium (Ba), strontium (Sr), calcium (Ca), etc., which becomes an electron emitting material layer, is applied on the surface of the cathode base metal by a method such as spraying. The cathode is incorporated in an electron tube, and the above alkaline earth metal carbonate is thermally decomposed in vacuum, for example, at about 1300 K, to change into alkaline earth metal oxide. The alkaline earth metal carbonate is a double salt or a mixed salt of an alkaline earth metal containing barium as a main component. Generally, barium is 57% by weight, strontium is 39% by weight, and calcium is 4% by weight. The ternary carbonate, which is a double salt, is widely used.

[0003] Of the above alkaline earth metal oxides, barium oxide (BaO) contributes to electron emission from the cathode.
During the operation of the oxide cathode, barium oxide is reduced at the interface between the base metal and the oxide by a reducing agent such as magnesium or tungsten that diffuses in the cathode base metal. Free barium that contributes to electron emission is formed by the reaction (1).

BaO + Mg → Ba + MgO (1)

[0005] Therefore, in the oxide cathode, the reaction between the reducing agent and the oxide as the electron emitting layer mainly proceeds near the interface between the cathode base metal and the oxide layer. Between the cathode base metal and the oxide layer, an oxidation product of a reduction reaction, for example, a layer called an intermediate layer made of a magnesium oxide layer is formed. The step of forming an intermediate layer by this reduction reaction is called an aging step, and the oxide layer provided on the surface of the cathode base metal is activated by this step.

[0006]

Since the above-mentioned reduction reaction is mainly performed at the interface between the cathode base metal and the oxide layer, if the reaction temperature in the aging step is kept constant, the rate of the reduction reaction increases. It will vary depending on the area of the cathode base metal. Therefore, when a metal formed only by the conventional press forming is used as the cathode base metal, it takes a long time to sufficiently reduce the oxide formed on the surface of the cathode base metal. In addition, as long as a conventional cathode base metal is used, a cathode oxide formed at a certain ratio is formed in the cathode base metal due to a problem of adhesive strength in any of the manufacturing processes of the electron gun for the cathode ray tube and the cathode ray tube. There was a problem of peeling off from the surface.

The present invention has been made in view of the above-mentioned problems, and has been made to reduce the time required for the reduction reaction of an oxide provided on the surface of a cathode base metal of a cathode for a cathode ray tube. It is an object of the present invention to provide a cathode for a cathode ray tube capable of suppressing peeling of an oxide from a cathode, and a method for producing the same.

[0008]

According to the cathode for a cathode ray tube of the present invention, an oxide as an electron-emitting substance is provided on the surface,
A cathode for a cathode ray tube containing a reducing agent that reacts with the oxide, wherein a surface of the cathode substrate on which the oxide is provided is roughened.

In the present invention, since the surface of the cathode base constituting the cathode for a cathode ray tube is roughened, the substantial surface area of the cathode base is increased as compared with the case where the roughening is not performed. Become. For this reason, the bonding strength between the oxide which is an electron-emitting substance provided on the roughened surface of the cathode substrate and the cathode substrate is improved.

Preferably, an oxide comprising an alkaline earth metal is provided on the surface of the cathode base.

The method of manufacturing a cathode for a cathode ray tube according to the present invention includes a forming step of forming a predetermined metal material into a cathode, a finishing step of finishing the surface of the cathode base to a rough surface, and an oxide layer on the surface of the cathode base. Forming an oxide layer.

In the present invention, since the surface of the cathode base constituting the cathode for a cathode ray tube is roughened, the substantial surface area of the cathode base is increased. For this reason, the speed of the reduction reaction with the reducing agent contained in the cathode substrate on the surface of the cathode substrate also increases.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of one embodiment of a cathode for a cathode ray tube according to the present invention, and FIG. 2 is a conceptual diagram of a cathode for a cathode ray tube according to the present embodiment.
FIG. 3 is a conceptual diagram of a cathode ray tube electron gun according to the present embodiment, and FIG. 4 is a conceptual diagram of a cathode ray tube (CRT) according to the present embodiment. First, an overall configuration of a cathode ray tube and an electron gun to which the cathode for a cathode ray tube according to the present invention is applied will be described.

As shown in FIG. 3, a CRT 31 includes a panel glass 32.
And a funnel glass 33, which are fused with frit glass (not shown), and the inside of the CRT 31 is maintained at a high vacuum. An electron gun 36 welded to the stem 35 by heating and fusing the neck 34 to a stem 35 provided with a plurality of pins 35a is enclosed in the neck 34 of the funnel glass 33. Interior carbon 37 is applied to the inner surface of the cone portion of the funnel glass 33 and the contact surface of the neck portion 34 with the electron gun 36.
Via the anode button 38 embedded in the cone,
A voltage can be applied from outside the CRT 31. A fluorescent screen 3 is provided on the inner surface of the panel glass 32.
9 is formed, and an aperture grill 40 is provided on the back surface thereof.
Is installed. A deflection yoke (not shown) is mounted on the outer periphery of the neck portion 34. The three electron beams emitted, controlled, and focused from the electron gun 36 are deflected by the deflection yoke (not shown) to form a fluorescent screen 39. The entire surface is scanned.

The electron gun electron gun 36, as shown in FIG. 4, the front of the cathode assembly 10 having three cathode 21, first grid G1, second grid G2, a third grid G3, fourth grid G4 and a fifth grid G5 are fixed in this order to the bead glass 43 as an insulating support at predetermined intervals along the longitudinal direction. Cathode assembly 10, first grid G1 and second grid G1
The grid G2 is a current control electrode, and a voltage of, for example, 50 V, 0 V, and 300 V is applied to these electrodes. The third grid G3, the fourth grid G4, and the fifth grid G5 are an accelerating electrode and a focusing electrode, and a voltage applied to the third grid G3 and the fifth grid G5 is, for example, about 27 kV. The voltage applied to the four grids G4 is about 9 kV.

Cathode Here, the cathode 21 is, as shown in FIG.
And a cathode sleeve 18. Cathode substrate 17
Is, for example, a trace amount of a reducing agent such as magnesium (M
g) and nickel (Ni) containing tungsten (W)
It is formed from an alloy and is shaped like a cup. The upper surface 17a of the cathode base 17 is roughened, and has many irregularities on the surface. An oxide layer 19 as an electron-emitting substance is formed on the upper surface 17a of the cathode base 17. The oxide layer 19 includes, for example, BaO,
It is composed of an alkaline earth metal oxide made of an electron-emitting substance such as SrO and CaO.

The cathode sleeve 18 is a tubular member having a hollow inside, made of, for example, a nickel-based nichrome alloy. A V-shaped metal wire 13 is welded in the middle of the outer periphery of the cathode sleeve 18 to support the cathode sleeve 18.

The cathode unit cathode assembly 10, as shown in FIG. 2, the supporting metal bar 11 for supporting the RGB for three of the above-mentioned cathode 21 has a ceramic disk 12 embedded, each support The metal rod 11 and each cathode 21 are connected to the V-shaped metal wire 1 described above.
3 are welded and fixed. A heater rest 15 for supporting a heater 16 is welded to a support metal rod 14 having a length different from that of the support metal rod 11. Three heaters 16 are welded to the heater rest 15, respectively, and the three heaters 16 are connected to the respective cathode sleeves 1 for RGB.
8 is inserted inside. The heater 16 is, for example,
It is composed of a high melting point metal composed of components such as iron, chromium, and aluminum, and generates heat by passing an electric current. The heating temperature of the heater 16 is, for example, about 900 ° C. to 1000 ° C.

Next, the cathode 21 constructed as described above is used.
An example of the operation of the CRT 31 having the following will be described. C
Since the RT 31 is equipped with the stem pin 35a and the anode button 38, a desired voltage is supplied from these to the CR 31.
It can be applied to each part inside T31. When a predetermined voltage is applied to the stem pin 35a and the anode button 38, a predetermined current flows through the heater 16. As a result, the heater 16 is heated, and then the cathode substrate 17 is heated to a predetermined temperature, and thermoelectrons are emitted from the attached electron-emitting substance.

Next, a desired voltage is applied to each part in the CRT 31 and a deflection yoke (not shown). Thereafter, by applying a predetermined video signal to the cathode 21,
The emitted and controlled electron beam is applied to the fluorescent screen 39 inside the panel glass 32, and an image is projected outside the panel glass 32. The electron gun 3 according to the present embodiment
Although the case 6 has been described as applied to a color cathode ray tube, it is also applicable to a cathode ray tube having an oxide cathode other than the color cathode ray tube.

Hereinafter, a manufacturing process of the cathode 21 configured as described above will be described. FIG. 5 is a flowchart illustrating an example of a manufacturing process of the cathode for a cathode ray tube according to the present embodiment. Cathode Base 17 As described above, the cathode base 17 is formed in a cup shape and contains a small amount of a reducing agent such as magnesium or tungsten. The cathode base 17 is formed into a required shape by pressing a nickel alloy obtained by rolling by sandwiching the nickel alloy from above and below (step S).
1).

The above-described pressing process is performed by using the conventional cathode 21.
This is also a step performed in the manufacturing process. In the present embodiment, a finishing step for finishing the upper surface 17a of the cathode base 17 to a predetermined roughness is additionally performed (Step S2). Specifically, for example, the upper surface 17a of the cathode base 17 can be polished by using a relatively polished abrasive with a normal polishing machine to make the surface rough. Also, besides using a polishing machine,
The surface may be roughened by using a file, or a lot of scratches may be formed.

Cathode Sleeve On the other hand, the cathode sleeve 18 is formed by drawing a cylindrical nichrome alloy into a predetermined shape (step S1).
0). Specifically, the outer shape of the cathode sleeve 18 is formed so as to match the inner diameter of the cathode base 17 cup.

Next, in order to hold the cathode sleeve 18 on the above-mentioned ceramic disk 12, a metal wire 13 made of a refractory metal formed into a V-shape is laser-welded to the cathode sleeve 18 (step S11). Then, the cathode sleeve 18 is heat-treated in humidified hydrogen to be selectively oxidized to blacken the surface (step S13).

Here, the outer surface of the cathode sleeve 18 is fitted into the inner diameter of the cup of the cathode base 17 which has been subjected to the above-mentioned roughening, and the cathode base 17 and the cathode sleeve 18 are welded by laser welding.
(Step S14). Thereafter, an oxide layer 19 as an electron-emitting material is formed on the upper surface 17a of the cathode base 17 by, for example, a spraying method (Step S15). Thereby, the cathode 21 is completed. In the present embodiment, the surface of the cathode base 17 on which the oxide layer 19 is formed is roughened. For this reason, the adhesion strength of the oxide layer 19 to the upper surface 17a of the cathode base 17 is larger than that in the case where the roughening is not performed.

The above-mentioned electron-emitting substance comprises, for example, alkaline earth metal carbonates such as barium, strontium and calcium. After that, the V-shaped metal wire 13 welded to the cathode sleeve 18 is welded to the cathode support bar 11 embedded in the ceramic disk 12. Further, a heater rest 15 is welded to a supporting metal rod 14 having a length different from that of the cathode supporting rod 11, a heater 16 is inserted into each of the cathode sleeves 17, and the heater 16 and the heater rest 15 are welded to each other. 10 is completed.

The cathode assembly 10 is incorporated into an electron gun 36, and the electron gun 36 is heated and welded to a glass container in which a panel and a funnel are fused with frit glass (not shown) to form a bulb. Next, the valve is evacuated to a vacuum in an exhaust furnace. Then, the oxide layer 19 made of an alkaline earth metal carbonate, which is an electron-emitting substance, attached to the surface of the cathode substrate 17 is thermally decomposed in a vacuum to change into an alkaline earth metal oxide. After the exhaust pipe of the cathode ray tube (not shown) is chipped off, the oxide layer 19 converted into the alkaline earth metal oxide is activated in an aging step, whereby the cathode structure 10 is completed. This aging step is a step of forming an oxidation product of a reduction reaction generated between the cathode substrate 17 and the oxide layer 19, for example, a layer called an intermediate layer made of a magnesium oxide layer. In the present embodiment, since the surface of the cathode substrate 17 on which the oxide layer 19 is formed is roughened, the reduction reaction rate between the reducing agent traveling in the cathode substrate 17 and the oxide constituting the oxide layer 19 is reduced. Increase. Therefore, the time required for the aging step is significantly reduced.

[0028]

According to the present invention, since the surface of the cathode substrate is roughened, the substantial surface area is greatly increased as compared with the conventional case. Therefore, the adhesive strength between the oxide as the electron-emitting substance formed on the cathode substrate and the cathode substrate is improved, and the probability of occurrence of a defect that the electron-emitting substance peels off can be reduced. Further, according to the present invention, since the substantial surface area of the cathode base is increased, it is possible to increase the reaction rate of the reduction reaction performed near the interface between the cathode base and the electron-emitting substance. For this reason, the time required for the aging step in the cathode ray tube manufacturing process can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of one embodiment of a cathode for a cathode ray tube according to the present invention.

FIG. 2 is a conceptual diagram of a cathode for a cathode ray tube according to the present embodiment.

FIG. 3 is a conceptual diagram of an electron gun for a cathode ray tube according to the present embodiment.

FIG. 4 is a conceptual diagram of a cathode ray tube according to the embodiment.

FIG. 5 is a flowchart illustrating an example of a manufacturing process of the cathode for a cathode ray tube according to the embodiment.

[Explanation of symbols]

17: cathode base, 17a: surface of cathode base, 18: cathode sleeve, 19: oxide layer.

Claims (9)

[Claims] 1. A cathode ray tube cathode having an oxide as an electron-emitting substance provided on a surface thereof and containing a reducing agent which reacts with the oxide, wherein the oxide of the cathode base is provided. The surface used is a cathode for cathode ray tubes that has been roughened. 2. The cathode for a cathode ray tube according to claim 1, wherein said cathode base is mainly composed of Ni. 3. The cathode for a cathode ray tube according to claim 1, wherein an oxide comprising an alkaline earth metal is provided on a surface of said cathode base. 4. The cathode for a cathode ray tube according to claim 1, wherein said cathode base contains Mg as a reducing agent. 5. A forming step of forming a predetermined metal material on a cathode base, a finishing step of finishing the surface of the cathode base to a rough surface, and forming an oxide layer as an electron-emitting substance on the surface of the cathode base. A method for producing a cathode for a cathode ray tube, comprising: an oxide layer forming step. 6. The oxide layer forming step includes the steps of: providing an alkaline earth metal carbonate on the surface of the cathode base; heating the cathode base in a vacuum to convert the alkaline earth metal carbonate to an alkaline earth; 6. The method for producing a cathode for a cathode ray tube according to claim 5, further comprising a step of changing to a metal oxide. 7. The method for producing a cathode for a cathode ray tube according to claim 6, further comprising an aging step of activating an alkaline earth metal oxide formed on the cathode substrate. 8. The method according to claim 5, further comprising, after the finishing step, a joining step of joining the cathode base to a cathode sleeve.
3. The method for producing a cathode for a cathode ray tube according to item 1. 9. The cathode wire according to claim 8, wherein in the forming step, the cathode base is formed in a cup shape, and in the joining step, the cathode sleeve is fitted into the cup-shaped cathode base and both are welded. A method for producing a cathode for a tube.