JPS601729B2 - Manufacturing method of electron tube heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electron tube heater such as a cathode ray tube.

Some indirectly heated cathode heaters attached to electron tubes such as cathode ray tubes are constructed by coating a conductive wire made of tungsten or an alloy of tungsten and nium with alumina as an insulating material.

The alumina coating on the above-mentioned filament bodies is usually carried out by electrodeposition, which can be roughly divided into two types: positive electrodeposition and negative electrodeposition. The positive electrodeposition method involves immersing the conductive filament to be electrodeposited with alumina into a haze deposition solution obtained by suspending fine particles of alumina in an organic solvent solution of a polymeric substance such as nitrocellulose. and use this as the positive electrode,
Alumina electrodeposition is performed using the other electrode in the lightning deposition liquid as a negative electrode.

Although this method forms an insulating layer of alumina electrodeposited layer with a dense and smooth surface on the above-mentioned filament, it has the following drawbacks. That is, in order to connect the filamentous body to the positive electrode and conduct electricity, it is necessary to anodize the filamentous body. Therefore, for example, in a cathode ray tube that incorporates a cathode in which such a striated body is arranged as a heater, during operation, the heater becomes an oxygen supply source within the tube, lowering the degree of vacuum inside the tube and reducing the operational function. let In some types of electron tubes, in order to improve heat radiation efficiency, fine powder of a high melting point colored material such as tungsten or molybdenum is further included on the white alumina electrodeposited layer of the heater8.
A tone-colored alumina electrodeposition layer may be formed, and when such multilayer electrodeposition is performed, nitrocellulose, etc., which acts as a binder for the white electrodeposition layer that has been exposed in advance, is used as a lightning solution for the dark electrodeposition layer. When soaked in water, the white electrodeposited layer may be redissolved and the white electrodeposited layer may partially run off, making it impossible to obtain a uniform multilayer electrodeposited layer. In addition, electrodeposition solutions containing polymeric substances such as nitrocellulose do not have sufficient throwing power, and it is difficult to uniformly deposit them onto striatal bodies with complex shapes. be. On the other hand, in the negative electrodeposition method, a suspension of fine alumina powder dispersed in a solution of electrolytes such as magnesium nitrate dissolved in a solvent such as water or ethanol that can dissolve the above electrolytes is used as the electrodeposition liquid. The conductive filament to be electrodeposited with alumina is immersed therein and used as a negative electrode, and the other electrode in the electroplating liquid is used as a positive electrode to perform alumina electrodeposition. When carrying out alumina electrodeposition using this method, it is necessary to add a magnesium compound to obtain good electrodeposition properties. For example, an electrodeposition solution containing magnesium nitrate can provide a good alumina multilayer electrodeposition layer. At this time, magnesium nitrate hydrolyzed in the lightning solution forms an exposed layer with alumina in the form of magnesium hydroxide, which functions as a binder, and magnesium hydroxide is poorly soluble in solvents such as water. Therefore, even if multilayer electrodeposition is performed, the white electrodeposited layer does not dissolve and a uniform military coated layer can be obtained. However, even if a good electrodeposited layer is obtained, in cathode ray tubes incorporating a cathode arranged as a heater, during operation, the magnesium compound in the alumina layer is exposed to the rays under high vacuum and high temperature. Reacts with components such as tungsten to produce metallic magnesium. The produced magnesium evaporates and lowers the vacuum inside the tube, and when the heater is stopped, the cooled magnesium evaporates between the heater and the cathode.
It precipitates between lead terminals and reduces insulation. Therefore, it is not preferable to incorporate a heater in which alumina is electrodeposited using a coating liquid containing a magnesium compound into an electron tube. This invention relates to an improvement in the manufacturing method of an electron tube heater in which an alumina insulating layer is formed on a filament by the electrodeposition method described above. A heater for an electron tube is characterized in that a good alumina insulating layer is formed on a filament made of a high melting point metal by using a lightning deposition liquid in which fine alumina powder is suspended in an aqueous solution of The method of manufacturing a privately heated cathode heater.

Therefore, the aqueous solution of aluminum acetates described above is gradually hydrolyzed to produce aluminum hydroxide according to the reactions shown in the following reaction formulas (1) and (2).
CH3COO)3 10 milk LO → A evening (OH) 3 10 milk day 3 COO day...'1}
A〇〇(CH3C〇〇) 2 12th 2〇→A〆(OH
) 3 10XH3COO days...■ Sufficiently dried solid aluminum hydroxide hardly dissolves in water or alcohol, but aluminum hydroxide obtained in solution form like this does not dissolve in water or alcohol. The aluminum hydroxide particles are uniformly dispersed to form a sol-like solution, and the aluminum hydroxide particles in this solution are positively charged.

When the above hydrolysis reaction is carried out in a suspension in which fine alumina particles are dispersed, the generated aluminum hydroxide is uniformly adsorbed on the surface of fine alumina particles in the suspension.
Alumina fine particles are positively charged. When the suspension in such a state is used as an electrodeposition liquid and a conductive filament for a heater is immersed therein, this is connected to the negative electrode, and the other electrode in the electrodeposition liquid is connected to the positive electrode. Alumina fine particles are deposited on the striatum. At that time, the surface of alumina fine particles. The adsorbed aluminum hydroxide acts as a binder, and within the alumina layer formed by open deposition, dispersed soot such as water is pushed out of the alumina layer by electroosmosis, and the alumina particles become even more tightly bound together. . Aluminum hydroxide, which is strongly fixed together with alumina particles, becomes resistant to water and alcohol, and the alumina electrodeposited layer is then washed with water or immersed in the flea solution again to form multilayer military uniforms. Even if it flows, it will never fall. Furthermore, when aluminum acetates are added to a suspension of fine alumina particles and tungsten fine particles dispersed in water or alcohol, and this is used as an electrodeposition liquid, a hierarchical alumina electrodeposition layer is formed on the striatum. It is formed.

Therefore, if the above-mentioned fine tungsten particles or the like are further electrodeposited with alumina on a white electrodeposited layer consisting only of fine alumina particles, a uniform and strongly fixed double electrodeposited layer can be obtained. Furthermore, if necessary, an exposed layer can be formed thereon to form a triple layer. That is, by using aluminum acetates, a uniform multilayer electrodeposited layer can be easily formed. The acetic acid (COOH) produced by the above reaction can be easily removed by washing with water, and the aluminum hydroxide in the hazed alumina layer can be dehydrated without oxidizing the twill bodies by heating in a nitrogen atmosphere, for example. can be converted into alumina.

The electron tube heater having the alumina electrodeposited layer formed in this manner is dense and has strong adhesion, can be uniformly formed even on complex-shaped filaments, has a very smooth surface, and has high mechanical strength.

Examples of the present invention will be described below.

Example 1 Water was added to an 8% aqueous solution of basic aluminum acetate, and a suspension of fine alumina powder dispersed in this solution was used as a hazing liquid.

The composition at this time is as follows. Alumina fine powder
3% water by weight
The proportion of aluminum added in the form of 8% aqueous basic aluminum acetate solution 5 in the form of 5% acetates by weight is 0.665% by weight.

) A conductive filament made of tungsten is immersed in the above dew solution and connected to the negative electrode, a platinum electrode in the dew solution is connected to the positive electrode, and 50 V DC is applied between the two electrodes. If (lightning liquid temperature 15-25 0) a thickness of 60 mm is deposited on the striatum.
A uniform white alumina electrodeposition layer was obtained.

The alumina layer was then heated to 1650 qC for 10 minutes in a reducing atmosphere to sinter it onto the filament.

In the heater obtained in this way, the alumina insulating layer has strong adhesion, and when the cathode equipped with this heater is incorporated into, for example, a cathode ray tube and operated, the insulation properties and withstand voltage are improved without reducing the degree of vacuum. However, it showed extremely good operating characteristics, including a significantly longer product life. Example 2 Fine tungsten powder and fine alumina powder are dispersed in a solution containing a 5% aqueous solution of aluminum acetate and ethanol to obtain a suspension, which is used as a coating liquid.

The composition at this time is as follows. Alumina fine powder
24% by weight tungsten fine powder
6% by weight ethanol 6
5% aqueous solution of aluminum acetate 1% by weight
(The proportion of aluminum added in the form of acetates is 0.
06% by weight.

) When the heater having the alumina white insulating layer obtained in Example 1 above (but before sintering treatment) is immersed in the above electrodeposition liquid and 40 V DC is applied in the same manner as in Example 1, a white insulating layer is formed. A uniform clear-colored alumina electrodeposition layer of 40 mm thickness was obtained on top.

This double electrodeposited alumina layer was then deposited at 165% in a reducing atmosphere.
It was heated to 0 qo for 10 minutes to cause crystallization on the striatum.

The heater thus obtained was a heater with good heat radiation efficiency, and an electron tube incorporating this heater had good electron radiation efficiency, a long heater life, and extremely stable tube characteristics. Examples 3-6 are summarized in the following table.

Examples 3, 4, and 5 are atomized liquids that correspond to the electrodeposition liquid of Example 1, and Example 6 is an electrodeposition liquid that corresponds to the spray liquid 2 of Example 2.

If the concentration of aluminum acetates in the electrodeposition solution is less than 0.005% by weight in terms of aluminum content, the adhesion of the alumina electrodeposition layer formed on the green striae will be insufficient;
If it exceeds 7% by weight, the uniformity of the alumina electrodeposition layer formed on the filament will decrease. Therefore 0.00
5-0. The range of weight % is good. As described above, all heaters on which alumina insulating layers are deposited and formed by the method of the present invention have the excellent characteristics described above, and electron tubes equipped with cathodes equipped with these heaters have excellent product reliability and service life. , it was possible to significantly improve operating characteristics, economic efficiency, etc.

Claims (1)

[Claims] 1. When manufacturing a heater by forming an alumina insulating layer on a linear body made of a high melting point metal by electrodeposition, an aqueous solution of aluminum acetate with a concentration of 0.005 to 0.7% by weight calculated as aluminum content is added. A method for manufacturing an electron tube heater, comprising forming an alumina insulating layer using an electrodeposition liquid in which fine alumina powder is suspended.