JP2933670B2 - Manufacturing method of cathode assembly for cathode ray tube - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cathode assembly for a cathode ray tube, which is suitable for a cathode ray tube, particularly a small picture tube, and has a high speed and a high speed.

2. Description of the Related Art For a small-sized monochrome picture tube used for a viewfinder or the like of a video camera, it is desired to use a direct-heated cathode assembly having a small wattage and excellent in speed.

However, a direct-heated cathode assembly formed by spraying an electron-emitting carbonate layer on a linear coil filament suspended between a pair of metal posts or by applying a dip method,
When used for a small cathode ray tube having a relatively short axial length, not only the carbonate layer is easily peeled off due to the influence of heat applied when sealing the glass bulb, but also it is difficult to obtain good electron emission characteristics and focusing characteristics. .

Therefore, the carbonate layer is applied to the coil filament by an electrodeposition (immersion electrodeposition) method. In this case, relatively good electron emission characteristics and focusing characteristics can be obtained.

However, the electrodeposition treatment involves contacting a linear coil filament suspended between a pair of metal pillars with the electron-emitting carbonate suspension filled in the liquid tank. Therefore, carbonate is electrodeposited also on the filament fixing portion of the support and the periphery thereof, and in the cathode ray tube incorporating the cathode structure completed by the electrodeposition treatment, the carbonate adhered to the metal support is a small piece. They tend to peel off in the form of so-called foreign matter in the tube. And, if such foreign matter in the pipe moves irregularly in the pipe, the pipe characteristics may be adversely affected.

In the manufacture of a small watt indirectly heated cathode structure, an electrically insulating metal oxide layer such as alundum may be formed by electrodeposition on a linear coil filament suspended between a pair of metal posts. However, there was the same problem as described above.

Means for Solving the Problems According to the present invention, an electrodeposition treatment is performed by contacting a linear coil filament suspended between a pair of metal columns with a suspension of an electron-emitting carbonate or an electrically insulating metal oxide. First, a small conductive cup having a size that allows a small amount of the suspension to be pumped from the liquid tank and contact only the coil filament is used.

Operation With this configuration, the area to be electrodeposited on the coil filament is determined by the width of the small cup to be used, and the level of the suspension to be supplied is easily regulated. The electrodeposition treatment limited to a predetermined region of the coil filament can be performed only by setting an appropriate value in advance. In addition, since the suspension pumped up by the small cup is outside the liquid tank, the suspension in the liquid tank can be stirred during the electrodeposition process, thereby increasing the processing efficiency.

Next, the present invention will be described with reference to the embodiments shown in the drawings.

As shown in FIGS. 1 to 3, a linear coil filament 1 made of tungsten is fixed to the distal ends of a pair of metal posts 2, 3 at both ends by laser welding or resistance welding. Also, a pair of metal posts 2,
The ceramic insulating substrate 4 which supports 3 at the middle portions has a metal cylinder 5 for degassing at the center, and enters the cylindrical portion of the cup-shaped control grid electrode (not shown) to fit into this cylindrical portion. It has a metal cylinder 6 to be welded on its outer peripheral surface.

As a means for depositing the electron-emitting carbonate layer 7 only on a predetermined area A of the coil filament 1 by an electrodeposition (immersion electrodeposition) method, a small conductive cup 8 is used. The small cup 8 illustrated in FIG. 4 is formed by processing a thin ribbon-shaped piece or block piece made of stainless steel into a spoon shape, and is connected to an elevating mechanism (not shown). The small cup 8 lifted up from the coil pumps the electron-emitting carbonate suspension 10 little by little, and
To supply. Both metal columns 2 and 3 are connected to the negative electrode of a DC power supply 12 via a protective resistor 11, and the small cup 8 is connected to the positive electrode of the DC power supply 12. Further, the suspension 10 in the liquid tank 9 is always subjected to a stirring process indicated by an arrow by a stirrer (not shown). The protection resistor 11 prevents a short circuit due to the contact between the coil filament 1 and the small cup 8.

Since the width of the small cup 8 is set to be substantially the same as or slightly smaller than the inner width between the tips of the two columns 2 and 3,
The small cup 8 that has been lifted by pumping the suspension 10 therein makes the suspension 10 contact only the coil filament 1. The suspension 10 before contact with the coil filament 1 is raised by the surface tension in the small cup 8, and when the coil filament 1 comes into contact with the suspension 10, the suspension 10 is turned into a coil as shown in FIG. Cover the filament 1. Then, since the electrodeposition process proceeds in this state, the electron-emitting carbonate layer 7 can be electrodeposited only in the predetermined area A, and the carbonate layer is unintentionally formed at the tip of the metal column or in the vicinity thereof. Will not be done. Further, the suspension 10 in the liquid tank 9 can be constantly stirred.

Taking the cathode structure provided for a 0.7-inch monochrome picture tube as an example, the coil filament has a wire diameter of 8.7 μm,
The outer diameter of the coil is 58 μm, the metal pillar is a Kovar wire having a diameter of 0.65 mm, the span of the filament suspension is 1.0 mm, and the layer thickness of the electron-emitting carbonate layer is 12 μm.

The above describes the embodiment in which the carbonate layer made of electron emission is formed on the surface of the coil filament by electrodeposition.
The electric insulating layer can be formed by electrodeposition simply by changing the suspension in the liquid tank to a suspension of metal oxide such as alundum.

Effect of the Invention Since the present invention is configured as described above, it is possible to efficiently form an electron-emitting carbonate layer or an insulating layer only in a predetermined region of a coil filament while applying an immersion electrodeposition method,
Manufacturing yield can be increased. In addition, an incomplete layer is not formed over an undesired region, small pieces of the same layer are not scattered as foreign matter in a tube, and the suspension in the liquid tank can be stirred during the electrodeposition process. Therefore, the processing efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a model diagram of a step of performing an electrodeposition process by applying the manufacturing method of the present invention, FIG. 2 is a perspective view of a completed cathode structure, and FIG.
FIG. 4 is a side sectional view of the cathode assembly, and FIG. 4 is a side sectional view of a spoon-shaped small cup used in the embodiment of the present invention. 1 ... Coil filament, 2,3 ... Metal support, 7 ...
Electron-emitting carbonate layer, 8 small cup, 9 liquid tank, 10
... suspension.

Claims (1)

(57) [Claims] 1. A suspension of an electron-emitting carbonate or an electrically insulative metal oxide is brought into contact with a linear coil filament suspended between a pair of metal pillars to perform an electrodeposition treatment. A method for manufacturing a cathode assembly for a cathode ray tube, comprising using a small conductive cup having a size such that a small amount is pumped from a liquid tank and brought into contact only with the coil filament.