JPH01296536A - Manufacture of indirectly heated cathode - Google Patents

Abstract

PURPOSE:To facilitate the formation of a continuous portion by heating the preset position of an electron emitting material, evaporating a binder contained in it, removing the electron emitting material, exposing a cathode substrate, and heating and making fragile the remainder of the exposed cathode substrate. CONSTITUTION:The required position of a cathode wire section 20 is heated by a heater 21. An organic binder contained in an electron emitting material 15 on the outermost layer of the cathode wire section 20 is evaporated and scattered, the binding force between a cathode substrate 14 and the electron emitting material is weakened. The heated electron emitting material 15 is then removed. A cathode terminal 16 is formed for the substrate 14 exposed when the electron emitting material is removed. The cathode substrate 14 is removed at the portion where no cathode terminal 16 is formed. The portion of the cathode substrate 14 to be removed is heated by a heater 23. An insulating layer 13 stuck on the heater wire 12 is then peeled off by a physical means such as a scraper to expose the heater wire 12, thereby this position is used as a power feed terminal for the heater wire 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a linear indirectly heated cathode, and in particular,
The present invention relates to a method for manufacturing an indirectly heated cathode that facilitates the formation of a connection portion for a heating power supply to a heater wire and a connection portion for a cathode potential to a cathode substrate, and enables continuous formation.

[Conventional technology]

A linear cathode is generally used as an electron source for a display device such as a fluorescent display tube. In this case, the electron-emitting substance (
(Ba, Sr, Ca), etc.), a potential difference corresponding to the heater heating voltage is generated at both ends of the linear cathode.

Therefore, in order to eliminate the difference in brightness between the display sections facing both ends of the cathode, it is necessary to devise a drive method such as heating a heater with alternating current, or to adjust the perveance by changing the distance between the display sections at both ends of the cathode. It is necessary to devise a second structure to obtain uniform electron emission.

Therefore, various studies have been conducted on indirectly heated cathodes in which a heater portion and a cathode substrate to which a cathode potential is applied are electrically separated.

As one of the basic configurations when constructing a linear cathode using an indirectly heated cathode, as disclosed in Japanese Utility Model Application Publication No. 58-193549, a core wire of a high melting point metal such as a thin tungsten wire is used. There is a structure in which an insulating layer is coated on the substrate, a metal conductive layer serving as a base metal is coated on the insulating layer, and then an electron-emitting substance is deposited.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 62-1.88130, thin metal wires of a predetermined pitch are wound twice (or once is of course possible) around a heater wire coated with an insulating layer. A structure in which a coiled cathode substrate is used and an electron-emitting material is deposited on the cathode substrate is also being considered.

The formation of electrical connection terminals for the heater wires of the formed linear cathode and the cathode substrate is generally performed as follows.

(2) Generally, the insulating layer and the electron-emitting material are deposited continuously by electrodeposition. Therefore, when depositing these substances, the electricity to the electrodeposited layer is stopped at the connection terminal forming location, and the heater wire and the cathode base are left exposed to prevent the electrodeposited substances from adhering.

After that, connection terminals are formed on this exposed metal portion.

■ After the steps up to the deposition of the electron-emitting material are continued, the material is cut to a required length and the electron-emitting material at both ends or one end is peeled off to expose, for example, the coiled cathode substrate. Unwind and use as a connection terminal to the cathode substrate.

Furthermore, the insulating layer coating on the tip is removed to provide a connection terminal for the heater wire.

[Problem that the invention seeks to solve]

” In the method for forming two connection terminals, in method ①, when making linear cathodes of various lengths, the voltage application and stop times during electrodeposition are different, and it is difficult to adjust them in the continuous manufacturing process. The problem is that it is extremely difficult. Particularly in the case of fluorescent display tubes, there is a trend toward high-mix, low-volume production, and the length of the cathode is not constant.

Therefore, there are problems in that it is necessary to change the settings of the electrodeposition apparatus each time, and cathodes of various lengths must be kept in stock.

On the other hand, in method (2), it is troublesome to handle the cathode cut to a predetermined length, and it is also difficult in practice to unwind the coiled cathode substrate. Therefore, continuous formation of cathodes by automation is difficult.

[Means for solving problems]

In general, it is preferable for the linear cathode used in a display device to be thin. For example, a linear indirectly heated cathode used in a fluorescent display tube has a wire diameter of about 100 μm to 200 μm.

Therefore, the thickness of the electron-emitting material or insulating layer coated thereon, and the cathode substrate wound or wrapped around it, is also about 50 μm at most.

The present inventor focused on the second feature of the above-mentioned structure of this seeded linear indirectly heated cathode, and by heating any part of the heater wire and the cathode base where a connection terminal is to be formed,
It has been found that the electron emitting material and the cathode substrate can be easily removed.

Therefore, the present invention includes a step of locally heating an arbitrary position where a connection terminal is to be formed on a linear cathode body in which a heater wire, an insulating layer, a cathode substrate, and an electron-emitting substance are successively formed. The object of the present invention is to provide a method for manufacturing an indirectly heated cathode.

[For production]

When the electron-emitting material is locally heated, binders such as organic substances contained in the electron-emitting material evaporate and scatter in the heated portions. As a result, the adhesion force between the electron-emitting materials and the cathode substrate is lost. therefore,
The cathode substrate can be exposed by simple physical means such as an air blower or a scraper.

Next, the exposed part of the cathode base is locally heated to embrittle the cathode base itself. As mentioned above, since the thickness of the cathode substrate is small, the metal material constituting it is easily oxidized and can be peeled off using a scraper or the like.

Thereafter, the insulating layer is peeled off by physical means or the like to expose the heater wire and use it as a power supply terminal for the heater wire.

〔Example〕

The substrate structure of the indirectly heated cathode is a laminated structure of a heater wire, an insulating layer, a cathode substrate, and an electron emitting material, as described in the section of the prior art. Here, the heater wire used is a wire made of a high melting point metal material such as tungsten, molybdenum, rhenium tungsten, etc. and having a diameter of about 10 μm to 50 μm.

Alumina powder is generally deposited on the surface of the heater wire by electrodeposition or the like and sintered at about 500°C to 2000°C to form an insulating layer. The thickness of the insulating layer is approximately 30 μm. Furthermore, a cathode substrate is formed on this insulating layer.

There are various types of cathode substrate structures, including those using a thin metal sleeve, those formed as a metal film by vapor deposition, and those formed by winding a thin metal wire into a coil. It is being However, in any case, the thickness of this cathode substrate is at most several tens of
It is less than μm.

Then, an electron emitting material is deposited on the cathode substrate.

For this electron-emitting substance, a method is generally employed in which B a + S r + Ca is electrodeposited in the form of a ternary carbonate.

FIG. 1 schematically shows an outline of this carbonate electrodeposition apparatus. Here, reference numeral 1 denotes a supply-side spool around which a cathode strand 2, which is continuously formed up to the cathode substrate, is wound. Then, the cathode wire 2 is supplied from the spool 1 to the electrodeposition tank 3. In the electrodeposition tank 3, for example, acrylic resin as a binder and B as an electron emitting substance are contained in an acetone solvent.
An electrodeposition liquid 4 containing carbonates of a, Sr, and Ca is mixed in an adjusted manner.

Further, the liquid 4 in the electrodeposition tank 3 is circulated and stirred by a motor 6 passing through a pipe S to prevent precipitation of carbonates in the tank 3. Then, a positive potential is applied to the electrodeposition tank 3 by the power source 7, and a negative potential is applied to the cathode wire 2 fed out from the spool 1 via the electrode roller 8. Rollers 9.10 are support rollers for supporting the cathode strand 2, and IX is a spool for winding up the ternary carbonate coated cathode strand 2.

The laminated structure of the cathode wire (hereinafter referred to as cathode wire section) on which carbonate is deposited as described above is shown in FIG. 2 in a partially cutaway manner. That is, on the surface of the heater wire 12 as a core wire, there is an insulation M13 made by coating and sintering alumina or the like, and this is covered with the cathode base 14. In the illustrated embodiment, the cathode substrate 14 is a tightly wound coiled thin metal wire. Further, this cathode substrate 14 was coated with a ternary carbonate 15 using an electrodeposition apparatus shown in FIG.

Next, a method for forming a connecting portion, which is the gist of the present invention, will be explained step by step starting from FIG.

First, as shown in FIG. 2, required portions of the cathode ray section 20 that have been coated with the carbonate 15 are heated by the heater 21. As will be described later, the electron emitting material 15 in this heated portion is removed, and a connection terminal for a cathode potential and a heating voltage supply portion for the heater wire 1 are formed here.

Therefore, the heating length is arbitrarily determined depending on the structure of the display tube to which the cathode is to be attached. In this example, the cathode ray section 20 was heated over 7 mm. Various structures can be considered for the heater 21 used for heating, but for example, a cylindrical micro-heater as shown in FIG. 3(a), a parallel plate-shaped heater as shown in FIG. 3(b), etc. are adopted. can.

Thus, the organic binder contained in the electron-emitting material 15 in the outermost layer of the cathode ray section 20 is evaporated and scattered by the heater 21, thereby weakening the adhesion between the cathode substrate 14 and the electron-emitting material. - For example, the organic binder can be evaporated by heating at about 350° C. for about 5 seconds. Of course, the heating temperature and time can be arbitrarily selected depending on the electrodeposition state and thickness of the carbonate.

Next, the heated electron emitting material 15 is removed.

Various methods can be considered as the removal means, but in this embodiment, as shown in FIG.
The electron-emitting substances are removed by blowing pressurized air from them. The electron-emitting substance may be scraped off by other physical means.

A cathode terminal 16 is formed on the cathode base 14 exposed by removing the electron-emitting substance] 5.

The cathode terminal 16 may be fixed by welding or the like to a toric body having a lead wire connection portion 16a as shown in FIG. 5(b), for example. Of course, the Riet wire can also be directly welded to the exposed cathode base 14. In this embodiment, cathode terminal 1
The length of 6 was 2 mm.

Subsequently, the portion of the cathode base 15 where the cathode terminal 16 is not formed is removed. That is, as shown in FIG. 6, the portion of the cathode base 14 to be removed is heated by the heater 23. As the heating means, a micro heater or the like was used as in the case of removing the electron emitting substance 15, and in this example, 5 mm of the exposed cathode base 15 was heated at 600° C. for 5 seconds. Since this heating is performed in air, the cathode base 14 itself is oxidized and becomes brittle. At this time, oxygen may be supplied through a nozzle or the like as necessary to promote oxidation.

By the way, as mentioned above, although the cathode substrate 14 itself is made of a metal material, it is made of thin wire, an extremely thin sleeve,
Alternatively, since it is a thin film, it becomes extremely brittle when heated and oxidized. Therefore, it is easy to peel it off, and it can also be peeled off using a scraper 24 made of ceramic, metal, resin, etc., as shown in FIG. 7, for example. In addition to this, in order to remove the embrittled cathode substrate 4, in addition to the two-way physical means, pressure air blowing means 11 as shown in FIG. 4 can be used.

Thereafter, the insulating layer 13 coated on the heater wire 12 is peeled off using a physical means such as a scraper, and the
By exposing and shaking, this is used as a power supply terminal for the heater wire 12.

By going through the above steps, as shown in FIG. 8, it is possible to form an indirectly heated cathode in which a connecting portion of the heater wire 12 and a cathode terminal 16 in electrical contact with the cathode base 14 are formed.

By the way, in each of the above-mentioned steps, it is possible to form the terminal portion by processing required portions of the cathode ray portion 20 while continuously feeding the cathode ray portion 20. This can be schematically shown in FIG. 9. That is, the cathode ray portions 20 that have been wound onto the spool 11 after the deposition of the electron emitting material are completed are sequentially fed out. First, the electron emitting material is heated and peeled off, and the cathode terminal 16 is attached to the exposed cathode base 14. After that, remove unnecessary parts of the cathode base 14.
is heated and made brittle, and this brittle base metal is removed. Furthermore, if the insulating layer is removed afterwards, the heater wire scum will be exposed, so fix the exposed part of the heater wire to the mounting part that will become the heater power supply terminal on the anode substrate of the fluorescent display tube, and connect the cathode terminal to the cathode terminal. By connecting the leads, the indirectly heated cathode of the fluorescent display tube is completed.

〔effect〕

In the method for producing an indirectly heated cathode according to the present invention, the cathode ray portion, which is formed continuously up to the electron emitting material, is processed to form an electrical terminal portion. Forming force up to 1 part becomes extremely easy.

In addition, the formation of the connection terminal for the cathode base and the power supply terminal for the heater wire can be performed continuously for the cathode wire part that is continuously supplied, and the force 1 and the formation position can be set arbitrarily. .

Therefore, it is possible to continuously manufacture the entire indirectly heated cathode, and there is an advantage that indirectly heated cathodes of various lengths can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an outline of an electrodeposition tank used for producing an indirectly heated cathode, and FIGS. 2 to 8 are diagrams for explaining an embodiment of the present invention step by step. FIG. 9 is a diagram for explaining the entire process of the method for manufacturing an indirectly heated cathode according to the present invention. 12... Heater wire 13... Insulating layer 14... Cathode base 15... Electron emitting material 16... Cathode terminal patent applicant Futaba Electronics Co., Ltd./7 circles

Claims (1)

[Claims] (1) A cathode base is wrapped around a heater portion made of a heater wire covered with an insulating layer, an electron-emitting substance is deposited on the cathode base, and electrical connection is made to the heater wire and the cathode base. In a method for manufacturing an indirectly heated cathode equipped with a terminal, a predetermined portion of an electron-emitting material layer continuously deposited on the cathode substrate is heated to evaporate and scatter a binder contained in the electron-emitting material layer. a step of removing the electron-emitting material layer from which the binder has been removed to expose the cathode substrate; a step of forming a connection terminal on a part of the exposed cathode substrate; and a step of heating the remaining portion of the exposed cathode substrate. After embrittlement,
A method for manufacturing an indirectly heated cathode, comprising: exposing an insulating layer by removing the insulating layer; and removing the exposed insulating layer to expose a heater wire.