JPH0778549A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a cathode-ray tube with which stable electron emission characteristics can be obtained constantly from a cathode under various usage environments by using binding material after dissolving it in organic solvent to be solution which is then filtered to eliminate solid impurities in forming electron emission material. CONSTITUTION:For a cathode-ray tube, electron emission material mainly comprising carbonate of alkali soil metal is applied on cathode base metal mainly comprising nickel, and by an electron beam as collected electrons emitted from this cathode, a fluorescent surface formed on an inner surface of a panel is scanned to emit light for displaying an image in the panel. In manufacturing this cathode-ray tube, binding material is dissolved in organic solvent, this solution is filtered by a filter, and carbonate powder of alkali soil metal is added to this filtered liquid or mixed liquid of this with the organic solvent to be mixed to form a suspension liquid. Next, this suspension liquid is applied on the cathode base metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an electron emitting material layer containing an alkaline earth metal carbonate as a main component, which is capable of maintaining excellent electron emitting characteristics over a wide cathode temperature range for a long period of time. The present invention relates to a cathode ray tube having a cathode formed by coating as an electron emission source.

[0002]

2. Description of the Related Art Generally, a so-called oxide cathode is used in a cathode ray tube. In the conventional oxide cathode manufacturing process, for example, "The Oxide Coated Cathode" (Chapman & Hall Ltd. London 1951) is used. Issue)
Carbonate powder ([Ba.Sr.
Ca] CO ₃ ) and a binder (nitrocellulose, acrylic resin, etc.) are dissolved and mixed in an organic solvent to form a suspension, which is applied to a cathode base metal containing nickel as a main component by a spraying method or the like. Was. After incorporating this cathode into a cathode ray tube and going through steps such as exhaust, activation, and aging,
The carbonate is converted into an oxide ([Ba.Sr.Ca] O), and free barium is generated by the reducing agent contained in the cathode base metal in a trace amount, and an atomic layer of barium is formed on the surface of the oxide. Are formed and electrons are emitted from this layer. For example, in the case of a color cathode ray tube, the electron emission characteristic is directly related to the brightness of the screen, and always operates so as to obtain a desired maximum electron emission amount (for example, necessary for displaying the highest brightness part of the screen of a color television). Required to do so. As is well known in the art, the presence of impurities in the electron emission material layer often significantly deteriorates electron emission characteristics. In particular, since impurities present in the carbonate powder affect the initial and life characteristics, sufficient attention has been paid so far to the raw material of the carbonate powder and the production method. However, regarding the nitrocellulose as a binder used in the production of the suspension for spray coating, an organic solvent, etc., it is considered that it will evaporate during the activation and aging steps, and regarding the contamination of impurities. It was in a state where it could not be said that sufficient attention was paid.

[0003]

SUMMARY OF THE INVENTION As described above, conventionally,
Regarding the quality control of the binder of the spraying suspension and its organic solvent in the spraying process of the oxide cathode, there is a tendency to be somewhat neglected as compared with the quality control of the carbonate powder. Although it hardly causes any problem as long as it is used at a voltage, it causes a problem such as finding a product lot in which deterioration of electron emission characteristics is clearly recognized when used at a voltage reduced state.

According to the present invention, the conventional problems concerning the cathode as described above do not occur, and stable electron emission characteristics can always be obtained from the cathode even under various use environments. Therefore, the manufacturing yield is improved and the reproducing process is performed. It is an object of the present invention to provide a method of manufacturing a cathode ray tube, in which no loss occurs in the above.

[0005]

In order to solve the above-mentioned problems, in the present invention, an electron emitting substance containing a carbonate of an alkaline earth metal as a main component is applied to a cathode base metal containing nickel as a main component. Then, the electron beam focused from the electrons emitted from the cathode causes the fluorescent surface formed on the inner surface of the panel to scan and emit light, thereby displaying an image on the panel. Dissolved in, and after filtering this solution through a filter, the alkaline earth metal carbonate powder is mixed with the filtrate or the filtrate and an organic solvent to form a suspension, and the suspension is It was decided to use a cathode coated on the cathode substrate metal as an electron beam emission source. Specifically, as a filter used for filtering the solution in which the binder is dissolved in an organic solvent,
It was decided to use, for example, one made of polypropylene, which has a filtration characteristic of capturing solid foreign matter having a particle size of 0.1 to 2 μm or more.

[0006]

[Function] Among the impurities contained in the binder and the organic solvent, those which dissolve in the organic solvent are evaporated into the atmosphere together with the organic solvent at the stage of coating on the cathode base metal by the spraying method as described above. Resulting in. It has been found that it is solid impurities that are not dissolved in an organic solvent that cause deterioration in the electron emission characteristics. In particular, it has been found that the binder unexpectedly contains many impurities such as Fe, S, Ca, Cl and K. These can be removed by using an appropriate filter. Thus, the impurities in the carbonate applied to the cathode base metal can be removed. Thus, according to the present invention, it is possible to reduce impurities that may deteriorate the electron emission characteristics in the carbonate of the cathode,
Good electron emission characteristics can be obtained after the oxide is formed.

However, the amount of the above solid impurities is extremely small in absolute value, and the influence thereof is always forced acceleration at which a sample is sampled at a predetermined ratio in the cathode ray tube manufacturing factory. It occurs only at a low rate that can not be detected in the life test, and it can be pointed out that the life of this lot seems to be poor statistically after several years or more have passed since the shipment of a specific lot. Therefore, the effect of the present invention is not such that the result appears immediately after implementation,
For example, it is clear that this is effective when the chemical supplier is forced to change due to a factory accident. The filtration performance of the above filter is the most severely determined in consideration of the performance price ratio of the cathode ray tube.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining a manufacturing process of a cathode of a cathode ray tube according to the present invention, and FIG. 2 is a diagram for explaining a manufacturing process of a cathode of a conventional cathode ray tube.

First Example: 40 g of nitrocellulose was dissolved in a mixed solution of 6 kg of diethyl carbonate and 3 kg of diethyl oxalate, and this solution was filtered through a polypropylene filter having a 0.2 μm mesh. After that, 6 kg of diethyl carbonate, 3 kg of diethyl oxalate and carbonate powder consisting of barium, strontium and calcium [(Ba.
12 kg of Sr.Ca) CO ₃ ] is mixed to form a suspension (suspension). By spraying the above suspension,
It is applied on the cathode base metal 2 of the cathode shown in FIG. In addition,
In FIG. 3, 1 is a carbonate, 2 is a base metal, 3 is a cathode sleeve, and 4 is a cathode disk.

Second Example: 40 g of nitrocellulose was dissolved in a mixed solution of 12 kg of butyl acetate and 6 kg of amyl acetate, and this solution was filtered through a polypropylene filter having a 0.2 μm mesh. After that, 12 kg of carbonate powder [(Ba.Sr.Ca) CO ₃ ] is mixed to obtain a suspension (suspension). The above suspension is applied onto the cathode base metal 2 of the cathode shown in FIG. 3 by the spray method.

Third embodiment: 12 kg of ethyl acetate,
40 g of nitrocellulose is dissolved in a mixed solution of 6 kg of amyl acetate, and this solution is filtered through a polypropylene filter having a 0.2 μm mesh. After that, carbonate powder [(Ba ・ Sr ・ Ca) CO ₃ ] 12k
g to make a suspension (suspension). The above suspension is applied onto the cathode base metal 2 of the cathode shown in FIG. 3 by the spray method.

As the above-mentioned filter for filtration, 0.1 to 2 μm
It was decided to use a filter having a filtration performance to capture solid foreign matter having a particle size of m or more. And by filtering a solution of the above binder such as nitrocellulose dissolved in an organic solvent,
It was possible to remove at least 70% or more of solid foreign matters having a particle size of 2 μm or more. In addition, it was confirmed that the electron emitting material layer containing the alkaline earth metal carbonate of the cathode as a main component according to the above-mentioned embodiment of the present invention did not contain foreign matter having a particle size of 3 μm or more.

[0013]

As described above, according to the present invention, the carbonate of the cathode, which serves as an electron emission source for the electron beam of the cathode ray tube (in actual operation, the carbonate changes to an oxide, An atomic layer of barium is formed on the surface)
Impurities in the cathode are reduced and the electron emission characteristics of the cathode are improved, which contributes to the improvement of the manufacturing yield in the manufacturing process of the cathode ray tube, while the electron emission characteristics are good for the user over a long life period, and It is possible to obtain a cathode ray tube in which a decrease in brightness is hardly felt.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a cathode of a cathode ray tube according to the present invention.

FIG. 2 is a diagram illustrating a manufacturing process of a cathode of a conventional cathode ray tube.

FIG. 3 is a side sectional view showing a structure of a cathode of a cathode ray tube.

[Explanation of symbols]

1 ... Carbonate, 2 ... Base metal, 3 ... Cathode sleeve,
4 ... Cathode disk.

Claims (1)

[Claims] 1. An electron-emitting substance containing a carbonate of an alkaline earth metal as a main component is applied to a cathode base metal containing nickel as a main component, and an electron beam focused by electrons emitted from the cathode is used. The fluorescent surface formed on the inner surface of the panel is scanned to emit light, and in a cathode ray tube designed to display an image on the panel, the binder is dissolved in an organic solvent, and the solution is filtered through a filter, and then the alkaline earth is used. A carbonate powder of a group metal is mixed with the above-mentioned filtrate or the above-mentioned filtrate and an organic solvent to form a suspension, and the cathode coated with this suspension on the above-mentioned cathode base metal is used as an electron beam emission source. Is a cathode ray tube.