JPH08293247A - Manufacture of anode base and of fluorescent character display tube - Google Patents

Abstract

PURPOSE: To reduce the adverse effects of a cathode on emission due to decomposition of a phosphor by forming an alkaline earth sulfide phosphor layer over the anode base of a fluorescent character display tube without causing adverse effects such as surface degradation. CONSTITUTION: An anode base for fluorescent character display tube is manufactured. A paste in which 1.5 parts by weight of terepionel and 1 part by weight of CaS:Ce are mixed is applied onto the anode base using a doctor blade. The anode base is baked in nitrogen gas at temperatures not higher than the boiling point of terepionel to form a phosphor layer. The residual emission rate of a fluorescent character display tube using the anode base is good compared with two other examples, one using screen printing and the other using atmospheric baking. The possibility of the surfaces of phosphor particles degrading due to heat treatments in the atmosphere and moisture is totally eliminated, and the fluorescent character display tube having an alkaline earth metal sulfide phosphor that has little adverse affect on emission can be put to practical use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an anode substrate provided with an alkaline earth metal sulfide phosphor, in which the emission characteristics of a cathode are less deteriorated with the passage of lighting time, or a method for manufacturing such a fluorescent display tube. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art A sulfide-based phosphor that is excited by a low-speed electron beam and is used for an anode, which is a light-emitting display portion of a fluorescent display tube, is a ZnS-based phosphor having ZnS as a matrix or a ZnS-based phosphor.
A ZnCdS-based phosphor having CdS as a matrix has been known. In addition to these, phosphors obtained by activating rare earths in alkaline earth sulfides, such as CaS: Ce, have been known as sulfide-based phosphors having excellent luminous efficiency in a high voltage region. .

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Phosphors such as CaS: Ce, which are obtained by activating rare earths on alkaline earth sulfides and have excellent luminous efficiency, are suitable for EL, CRT, projection tubes, etc. It was suggested to use. However, in spite of such a proposal, according to the findings obtained by the present inventors,
Since the alkaline earth sulfide phosphor such as CaS: Ce is chemically unstable, it cannot be practically used as a phosphor for a display element. Here, chemically unstable refers to a point that is easily oxidized and hydrolyzed in the air. For example, in the case of CaS, it is oxidized in the air to produce calcium thiosulfate, and hydrogen sulfide is generated by the action of moisture and carbon dioxide. Further, although it is hardly soluble in cold water, it gradually hydrolyzes to produce calcium hydrogen sulfide and calcium hydroxide.

Due to such properties, CaS: Ce
Alkaline earth sulfide phosphors such as, for example, as described below, the phosphor is easily decomposed in the step of applying the phosphor as a light emitting display portion in a predetermined pattern, and the phosphor adhered in a predetermined pattern It is easily oxidized in the step of baking.

First, in the screen printing method, which is a general method for depositing a phosphor, the phosphor and a vehicle are mixed to form a paste, which is printed in a predetermined pattern on a substrate and then baked in the atmosphere. To make the paste components CO ₂ and evaporate. In order to decompose the organic matter used during deposition by firing, it is necessary to perform firing in an oxidizing atmosphere. However, if this is done, the alkaline earth sulfide phosphor itself such as CaS: Ce will also be oxidized.

In the electrodeposition method, which is another method for depositing the phosphor,
The phosphor was dispersed in water, and the phosphor was attached to the anode according to the principle of electric permanence. Since water is used in this method, the Ca
The alkaline earth sulfide phosphor such as S: Ce is hydrolyzed.

In the slurry method, which is another method for depositing the phosphor, the phosphor is dispersed in a liquid containing polyvinyl alcohol or ammonium dichromate as a main medium, and the coated product is covered with a mask having a predetermined pattern. After exposure, the polyvinyl alcohol is removed by water development to obtain a predetermined pattern. In this method, the alkaline earth sulfide phosphor such as CaS: Ce is P
It reacts with a photosensitizer such as UA-ADC, PUA-SbQ, etc., and the slurry liquid becomes gel and cannot be used.

From the above circumstances, even if the alkaline earth sulfide phosphor is formed in the light emitting portion of the display element by the conventional forming method,
The surface of the phosphor was in a rough state and the light emitting state was poor, so that it was not practical. Further, when applied to a display element, for example, a fluorescent display tube, when electrons collide with the phosphor during driving, S is easily emitted due to heat generation, which contaminates the cathode and deteriorates electron emission characteristics. As shown in FIG. 1, in the alkaline earth sulfide phosphor formed by the conventional forming method, ZnS:
The reduction rate of the pulse emission remaining with respect to the elapsed time is more remarkable than that of the Cu and Al phosphors.

The present invention has been made on the basis of the findings of the inventors of the present invention described above, and an alkaline earth sulfide can be formed on the anode substrate of a fluorescent display tube without detrimental effects such as surface deterioration. It is an object of the present invention to provide a method of manufacturing a fluorescent display tube which can form a phosphor layer and has a small adverse effect on the emission of the cathode due to the decomposition of the phosphor.

[0010]

A method of manufacturing an anode substrate according to a first aspect of the present invention comprises mixing an alkaline earth metal sulfide phosphor with a non-aqueous solvent that evaporates in an inert atmosphere or in a vacuum. And a step of evaporating the solvent from the paste on the substrate in an inert atmosphere or in a vacuum to form a phosphor layer.

A method for manufacturing an anode substrate according to a second aspect is the method for manufacturing an anode substrate according to the first aspect, wherein the solvent is evaporated from the paste on the substrate to form a phosphor layer, It is characterized in that the substrate is baked at a temperature equal to or lower than the boiling point of the solvent.

According to a third aspect of the present invention, there is provided a method of manufacturing a fluorescent display tube, which comprises forming a layer of a paste obtained by mixing a non-aqueous solvent that evaporates in an inert atmosphere or in a vacuum with an alkaline earth metal sulfide phosphor. Forming on the substrate, forming a phosphor layer by evaporating the solvent from the paste on the substrate in an inert atmosphere or in vacuum, and keeping the phosphor layer isolated from the active atmosphere While providing a control electrode and a cathode on the substrate, a step of sealing the container part to the substrate to form an envelope while keeping the phosphor layer isolated from the active atmosphere, and the envelope. And a sealing step for making the inside of the container a vacuum.

[0013]

EXAMPLES As described in the section [Problems to be Solved by the Invention], the inventors of the present invention apply to a case where a fluorescent display tube is formed by a conventional manufacturing method using an alkaline earth sulfide phosphor. It was considered that the reason why the emission characteristics of the cathode sharply deteriorated was that the alkaline earth sulfide phosphor was easily hydrolyzed and was weak against heating in an oxidizing atmosphere.

Therefore, the inventors of the present application, based on the above findings, in order to prevent the emission characteristics of the cathode from deteriorating in the fluorescent display tube, the alkaline earth sulfide is hydrolyzed by heat treatment in a hydrolysis or oxidizing atmosphere. The object of the present invention is to provide a method for manufacturing a fluorescent display tube in which the surface of the fluorescent substance does not deteriorate.

In the method of manufacturing a fluorescent display tube using the alkaline earth sulfide phosphor described in this embodiment, in addition to the fluorescent display tube that emits a low-speed electron beam, the anode voltage is several hundred volts or more for medium speed and It is also suitable for a high-speed electron tube, and as an electron source, it is suitable for either a fluorescent display tube having a filament cathode having an electron emitting substance or a fluorescent display tube having an FEC (Field Emission Cathode).

In the method of manufacturing the fluorescent display tube of this embodiment, an inert atmosphere (eg, nitrogen gas, argon gas, etc.) is used.
Organic solvent that is a non-aqueous solvent that evaporates in vacuum or in vacuum (eg, terpineol with a boiling point of about 180 ° C., boiling point of about 40 ° C.)
Glycerin at 0 ° C.) is mixed with an alkaline earth metal sulfide phosphor to form a paste. This paste is applied on a substrate in a predetermined pattern by a doctor blade method or a screen method, and the organic solvent is evaporated from the paste on the substrate in an inert atmosphere or in vacuum to form a phosphor layer. After that, the process is advanced while keeping the phosphor layer isolated from the active atmosphere. First, the control electrode and the cathode are provided on the substrate, and then the container is sealed to the substrate to form the envelope. Then, the inside of the envelope is evacuated and sealed.

As described above, by vacuum-sealing while preventing deterioration of the phosphor particle surface due to heat treatment in the atmosphere and moisture, a fluorescent display tube to which an alkaline earth metal sulfide phosphor could not be conventionally applied. It could be put to practical use as a phosphor for a field emission device.

Hereinafter, the manufacturing process of a fluorescent display tube using an alkaline earth metal sulfide phosphor and the performance of the manufactured fluorescent display tube will be described with reference to specific examples 1 to 3. (Example 1) A fluorescent display tube having a quadrupole structure having two control electrodes was manufactured. As shown in FIG. 4, an electrode 2 made of an ITO film is formed on a glass anode substrate 1. Electrode 2
And a light emitting region 3 having a diameter of 4 mm is provided on the anode substrate 1. The anode substrate 1 other than the light emitting region 3 is covered with an insulating layer 4 having a thickness of 35 μm. The phosphor paste 5 is prepared by adding 1 part by weight of CaS: Ce to 1.5 parts by weight of terpineol,
The mixture was used. As shown in FIG. 4, the phosphor paste 5 is used to form a phosphor layer having a thickness of about 20 μm on the insulating layer 4 by using a doctor blade 6. The anode substrate 1 having this phosphor layer is fired in nitrogen gas at a temperature not higher than the boiling point of terpineol for 30 minutes, and the anode substrate 1 is taken out after the temperature of the firing furnace reaches room temperature. A fluorescent display tube was manufactured. During the assembly process of the fluorescent display tube, the phosphor layer was always kept in an inert gas atmosphere.

Anode voltage 400 V, anode current density 25 mA
A luminous efficiency of 5.81 m / W at / cm ² was obtained. The emission characteristic of the fluorescent display tube of this example is as shown in FIG. 1, which shows the relationship between the lighting elapsed time and the pulse emission residual rate. In FIG. 1, a fluorescent display tube having ZnS: Cu, Al phosphors formed by screen printing and holding at 450 ° C. in air for 15 minutes, and CaS formed under the same conditions:
The relative residual emission rate of the fluorescent display tube having the Ce phosphor is shown for comparison. As is apparent from FIG. 1, by using the method of this example, the deterioration of the phosphor particle surface due to heat treatment and humidity in the atmosphere is completely eliminated, and the adverse effect on the emission of the alkaline earth metal sulfide phosphor is small. It was possible to put into practical use a fluorescent display tube equipped with.

Example 2 A paste having the following composition was prepared and screen printed on an anode substrate. CaS: Eu 1 part by weight Glycerin 1 part by weight Using this paste, printing was carried out by an ordinary screen printer to form a film having an average thickness of 13 μm on the anode substrate. This anode substrate was fired in a nitrogen atmosphere at a temperature not higher than the boiling point of glycerin (290 ° C.). This anode substrate was mounted on a high voltage tube having an electron acceleration voltage of 8 kV, and the temporal change of pulse emission was measured in the same manner as in Example 1.
During the mounting process on the high voltage tube, the phosphor layer was always kept in an inert gas atmosphere. A comparative example was a positive electrode substrate on which a paste film was formed with the same materials and steps and which was fired in air at 450 ° C. The residual rate of pulse emission with respect to the elapsed time showed the same tendency as in Example 1. The luminous efficiency is
The relative value was 100 in Example 2 of the nitrogen gas firing, and 80 in the comparative example of the air firing. FIG. 2 shows the change in luminous efficiency with respect to the elapsed time. Luminous efficiency is 1000
Even after a lapse of time, 80% or more was maintained.

Example 3 A paste having the following composition was prepared and screen printed on an anode substrate. CaS: Ce 1 part by weight Glycerin 1 part by weight In ₂ O ₃ 0.25 part by weight Using this paste, printing was carried out by an ordinary screen printing machine to form a film having an average thickness of 13 μm on the anode substrate. . This anode substrate was fired in a nitrogen atmosphere at a temperature not higher than the boiling point of glycerin. This anode substrate was mounted on a fluorescent display tube, and a life test was conducted by lighting at an anode voltage of 50V. During the assembly process of the fluorescent display tube, the phosphor layer was always kept in an inert gas atmosphere. As in Example 1, the change in pulse emission over time was measured. The result is shown in FIG. A comparative example in which an anode substrate on which a paste film is formed with the same material / process is fired in air at 450 ° C. is shown in the same figure. The residual rate of pulse emission showed the same tendency as that of the first example.

As in the example described above, according to the present embodiment, no water is used for manufacturing the phosphor layer, no baking is performed in the atmosphere, and the anode substrate is used as a part of the fluorescent display tube. Assembled as, since the manufactured phosphor layer is not exposed to the atmosphere, there is no risk of the surface of the alkaline earth sulfide phosphor being deteriorated by heat treatment in a hydrolysis or oxidizing atmosphere,
It is possible to manufacture a fluorescent display tube provided with an alkaline earth sulfide phosphor in which the emission characteristics of the cathode are less likely to deteriorate.

In each of the examples described above, CaS: E
The u phosphor is particularly useful as a red light emitting phosphor, and the CaS: Ce phosphor is useful as a yellow green light emitting phosphor.

In the embodiment described above, CaS:
Although the Eu phosphor and the CaS: Ce phosphor have been described, the present invention is also applicable to other BaS phosphors and alkaline earth sulfide phosphors shown in Table 1 below.

[0025]

[Table 1]

[0026]

According to the present invention, a non-aqueous solvent is used in place of water for the production of the phosphor layer, and firing in the atmosphere is not performed, and the anode substrate is used as a part of the fluorescent display tube. Since the manufactured phosphor layer is not exposed to the active atmosphere until assembled, there is no risk of the surface of the alkaline earth sulfide phosphor being deteriorated by heat treatment in a hydrolysis or oxidizing atmosphere,
It is possible to manufacture a fluorescent display tube provided with an alkaline earth sulfide phosphor in which the emission characteristics of the cathode are less likely to deteriorate.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an elapsed time and a pulse emission residual rate in a practical example 1 of an example in comparison with a comparative example.

FIG. 2 is a graph showing the relationship between the elapsed time and the remaining emission luminance in Example 2 of Example.

FIG. 3 is a graph showing the relationship between the elapsed time and the pulse emission residual rate in Example 3 of the example, in comparison with the comparative example.

FIG. 4 is a diagram showing one manufacturing process of the anode in Example 1 of the example.

[Explanation of symbols] 1 Anode substrate

Claims (3)

[Claims] 1. A step of forming, on a substrate, a paste layer formed by mixing a non-aqueous solvent that evaporates in an inert atmosphere or in a vacuum with an alkaline earth metal sulfide phosphor, and in an inert atmosphere or And a step of evaporating the solvent from the paste on the substrate in a vacuum to form a phosphor layer. 2. The method for manufacturing an anode substrate according to claim 1, wherein in the step of forming the phosphor layer by evaporating the solvent from the paste on the substrate, the substrate is baked at a temperature equal to or lower than the boiling point of the solvent. 3. A step of forming, on a substrate, a paste layer formed by mixing a non-aqueous solvent that evaporates in an inert atmosphere or in vacuum with an alkaline earth metal sulfide phosphor, and in an inert atmosphere or Forming a phosphor layer by evaporating the solvent from the paste on the substrate in a vacuum; and providing a control electrode and a cathode on the substrate while keeping the phosphor layer isolated from the active atmosphere, And a step of forming an envelope by sealing the container part to the substrate while keeping the phosphor layer isolated from an active atmosphere, and a step of sealing the inside of the envelope to a vacuum. Fluorescent display tube manufacturing method.