JPH03269930A - Manufacture of cathode composition for cathode-ray tube - Google Patents

Abstract

PURPOSE:To form an electrodeposited layer only on a prescribed region and improve production yield, by drawing up a suspension of an electron radiative carbonates, etc., in a conductive small cup and bringing it into contact with a linear coil filament between metal poles at the time of electrodeposition of the suspension on the filament. CONSTITUTION:The width of a small cup 8 is set to be almost the same as or slightly narrower than the width between two inner tips of both poles 2, 3 and a suspension 10 in a liquid tank 9 is taken up and risen with the cup and electrodeposition is carried out while coil filament is sunk in the suspension. Consequently, an electron radiative carbonate layer is electrodeposited only on a prescribed region and undesired carbonate deposition does not occur in the tip parts of the poles 2, 3 and the neighboring region. The suspension 10 in the liquid tank 9 can be stirred during electrodeposition and thus process efficiency is improved. A protective resistor 11 prevents short-circuit due to a contact between the coil filament 1 and the small cup 8.

Description

DETAILED DESCRIPTION OF THE INVENTION 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 cathode ray tubes, particularly small picture tubes, and has a small wattage and excellent interlocking properties.

2. Description of the Related Art For small monochrome picture tubes used in viewfinders of video cameras, it is desired to use a directly heated cathode structure which is small in wattage and has excellent interlocking performance.

However, a directly heated cathode structure in which a linear coil filament suspended between a pair of metal supports is coated with an electron-emissive carbonate layer by spraying or dipping is used for compact cathode ray tubes with a relatively short axial length. If used for this purpose, the carbonate layer not only tends to peel off due to the effect of heat applied when sealing the glass bulb, but also makes it difficult to obtain good electron emission characteristics and focusing characteristics.

Therefore, the carbonate layer is deposited on the coil filament by electrodeposition (immersion electrodeposition), and in this case, relatively good electron emission characteristics and focusing characteristics can be obtained.

Problems to be Solved by the Invention However, the electrodeposition process involves bringing a linear coiled filament suspended between a pair of metal supports into contact with an electron-emitting carbonate suspension filled in a liquid bath. from,
Carbonate is also electrodeposited on the filament fixing part of the support and its surroundings, and in a cathode ray tube incorporating a cathode structure completed by such electrodeposition treatment, the carbonate attached to the metal support is formed in the form of small pieces. It is easy to peel off and become a so-called foreign body in the tube. If such foreign matter within the tube moves irregularly throughout the tube, it may adversely affect the characteristics of the tube.

In addition, in manufacturing indirectly heated cathode structures of small wattage, it is also possible to form an electrically insulating metal oxide layer such as alundum on a linear coil filament suspended between a pair of metal supports by electrodeposition. , there were issues similar to those mentioned above.

Means for Solving the Problems According to the present invention, a straight coil filament suspended between a pair of metal supports is brought into contact with a suspension of an electron-emitting carbonate or an electrically insulating metal oxide to perform electrodeposition treatment. A small electrically conductive cup is then used to draw a small amount of the suspension from the bath into contact with the coil filament.

Effect: When horizontally drawn in this way, the area to be electrodeposited on the coil filament is determined by the width of the small cup used, and it also makes it easier to regulate the level of the suspension to be supplied. Just set it to an appropriate value in advance,
Electrodeposition processing can be performed limited to a predetermined area of the coil filament. Furthermore, since the suspension drawn up by the small cup is outside the liquid tank, the suspension in the liquid tank can be stirred during the electrodeposition process, and the processing efficiency can be increased accordingly.

Example Next, the present invention will be explained along with embodiments shown in the drawings.

As shown in FIGS. 1 to 3, a linear coil filament 1 made of tungsten is fixed at both ends to the tips of a pair of metal struts 2 and 3 by laser welding or resistance welding. In addition, a pair of metal supports 2
. It has a metal cylindrical body 6 on its outer peripheral surface to be welded to the metal cylinder 6.

A small conductive cup 8 is used as a means for depositing the electron emissive carbonate layer 7 only on a predetermined region A of the coil filament 1 by electrodeposition (immersion electrodeposition). The small cup 8 illustrated in FIG. 4 is a spoon-shaped thin ribbon-like piece or block piece made of stainless steel, and is connected to an elevating mechanism (not shown). The small cup 8 rising from position 8a in the liquid tank 9 contains electron-radioactive carbonate! F
! The turbid liquid 10 is pumped up little by little and supplied to the coil filament 1. Both metal supports 2 and 3 are connected to the negative electrode of a DC power source 12 via a protective resistor 11, and the small cup 8 is connected to the positive electrode of the DC power source 12. Further, the suspension 10 in the liquid tank 9 is constantly subjected to a stirring process indicated by an arrow by a stirrer not shown. The protective resistor 11 prevents a short circuit caused by contact between the coil filament 1 and the small cup 8.

The width of the small cup 8 is set to be approximately the same as or slightly smaller than the inner width of the support columns 2.3, so the liquid tank 9
The small cup 8, which has risen by sucking up the suspension 10 inside, sinks the coiled filament 1 into the suspension 10, as shown in FIG. Since the electrodeposition process proceeds in this state, the electron emissive carbonate layer 7 can be electrodeposited only in the predetermined area A, and the carbonate layer is not formed inadvertently at the tip of the metal support or in its vicinity. You will no longer be exposed to it. Further, the suspension 10 in the liquid tank 9 can be constantly stirred.

0. Taking the cathode assembly used in a Finch-type monochrome picture tube as an example, the wire diameter of the coil filament is 8.7 μm.
1 coil outer diameter is 58μm 1 metal support wire diameter is 0.651m
With 1m of Kovar wire, the filament suspension span is 1.
0 mm, and the layer thickness of the electron emissive carbonate layer is 12 μm.

The above describes an example in which an electron-emitting carbonate layer is formed on the surface of a coil filament by electrodeposition, but it is also possible to simply change the suspension in the liquid bath to a suspension of metal oxide such as alundum. , the electrically insulating layer can be formed by electrodeposition.

4. Effects of the Invention Since the present invention is configured as described above, it is possible to efficiently form an electron emissive carbonate layer or an insulating layer only in a predetermined area of a coil filament while applying an immersion electrodeposition method, thereby improving manufacturing yield. can be increased. In addition, an incomplete layer is not formed across undesired areas, small pieces of the same layer are not scattered as foreign objects in the tube, and the suspension in the liquid bath can be agitated during the electrodeposition process. Therefore, processing efficiency can be improved.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the electrodeposition process using the manufacturing method of the present invention, Figure 2 is a perspective view of the completed cathode structure, and Figure 3 is a perspective view of the completed cathode structure.
The figure is a side sectional view of the cathode assembly, and Figure 4 is a side sectional view of a spoon-shaped measuring cup used in an embodiment of the present invention. 1... Coiled filament, 2, 3...
・Metal pillar, 7... Electron radioactive carbonate layer, 8.
...Small cup, 9...Liquid tank, 10...
...suspension.

Claims (1)

[Claims] When a suspension of an electron-emitting carbonate or an electrically insulating metal oxide is brought into contact with a straight coiled filament suspended between a pair of metal supports for electrodeposition, a small amount of the suspension is removed from a liquid bath. A method for manufacturing a cathode assembly for a cathode ray tube, comprising using a small conductive cup that is pumped up and brought into contact with the coil filament.