KR20020051704A - cathod of color cathode ray tube - Google Patents

Abstract

PURPOSE: A cathode of a color cathode ray tube is provided to improve a characteristic of electron emission in the cathode by changing composition of an electron emission material layer formed on an upper face of a base metal. CONSTITUTION: Scandium oxide powder as rare-earth metal oxide powder(12) and thorium nitride powder as actinium metal compound powder(14) are prepared. Triple carbonation including (Ba,Sr,Ca)CO3 is mixed with the scandium oxide powder. The mixed material is mixed again with a binder including a nitrocellulose and a butylacetate in order to form a suspension. The first electron emission material layer(13b) is formed by spraying the suspension on a base metal(11). The suspension is formed by mixing the triple carbonation including (Ba,Sr,Ca)CO3, the thorium nitride powder, and the binder including the nitrocellulose and the butylacetate. The second electron emission material layer(16) is formed on the first electron emission material layer(13b) by coating the suspension on the first electron emission material layer(13b).

Description

Cathode of color cathode ray tube

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode structure for color cathode ray tubes, and more particularly, to an anode structure that improves electron radiation characteristics of a cathode and enables stable electron radiation for a long time even under high current density.

In the color cathode ray tube, as shown in FIG. 1, a panel 1 having a fluorescent film formed on its inner surface and a funnel 2 coated with conductive graphite on its inner surface are sealed with fusion glass. The neck portion 3 is equipped with an electron gun 4 for generating an electron beam. A shadow mask 5, which is a color-selective electrode, is supported by a frame inside the panel 1, and an electron beam is provided on the outer circumferential surface of the funnel 2. A deflection yoke (6) for horizontally biasing is mounted.

In the electron gun 4, a cathode 7 for emitting hot electrons is embedded, and the cathode emits hot electrons from the cathode by voltages applied to a plurality of adjacent G _{1 and} G ₂ grids 8. .

In the cathode ray tube configured as described above, when an image signal is input to the electron gun 4, hot electrons are emitted from the cathode 7 of the electron gun 4, and the emitted electrons are accelerated and focused toward the panel by the voltage applied from each electrode of the electron gun. Go through the process. At this time, the path of the electron beam is adjusted by the magnetic field of the magnet mounted on the neck portion of the panel, and the adjusted electron beam is scanned on the inner surface of the panel by the deflection yoke 6, and the deflected electron beam of the shadow mask 5 Color selection is performed while passing through the slot, and the selected electron beam collides with the fluorescent film on the inner surface of the panel to emit light to reproduce an image signal.

As the cathode 7 for the cathode ray tube, an oxide cathode using hot electron emission characteristics is mainly used. As shown in FIG. 2, a heater 9 formed by coating an alumina with an insulating layer is inserted into a cylindrical cathode sleeve 10 by inserting a heater 9 into which a tungsten (W) is a main component. A base metal 11 including a reducing agent (magnesium (Mg), silicon (Si), etc.) is formed, and on the upper surface of the base metal, at least strontium carbonate (SrCO ₃ ) containing carbon (Ba) and carbonic acid calcium (CaCO ₃₎ are composed of electron emission material layer 13 is composed mainly of an alkaline-earth (alkaline -earth), metal carbonates (Cabonate) and the like.

Another cathode is the decomposition of rare earth metal oxides such as alkaline earth metal carbonates and scandium oxide (Sc ₂ O ₃ ) powders 12 including at least barium (Ba) on the above-described gas metal 11 as shown in FIG. 3. It is composed of a cathode having an electron emitting material layer 13a containing a metal oxide.

The electron emitting material layer of the conventional oxide cathode for producing the cathode is a binder composed of triple carbonation (Ni, cellulose) and butyl acetate (Butylacetate) consisting of (Ba, Sr, Ca) CO ₃ It is mixed with and made into a suspension (suspension) form, and by coating it on the base metal 11 by spraying or the like to form an electron emitting material layer (13) (13a). The operation of generating electrons in the cathode manufactured as described above is as follows.

That is, the alkaline earth metal carbonate coated on the base metal 11 is converted into a ternary composite oxide of (Ba, Sr, Ca) O by heating the heater in a vacuum exhaust process.

(Ba, Sr, Ca) CO ₃ → (Ba, Sr, Ca) O + CO ₂ -------------- ①

In the vacuum exhaust process, the electron emitting material layers 13 and 13a, which are converted into a composite oxide of (Ba, Sr, Ca) O, are contained in the base metal 11 by heating at 900 to 1100 ° C. of the heater in the aging process. It reacts with a reducing metal such as Si or Mg to produce barium (Ba), which is an electron emission source.

That is, the reductive element present in the base metal 11 by the high temperature heating of the heater diffuses to the interface between the electron emitting material layers 13 and 13a composed of the base metal and the complex oxide of (Ba, Sr, Ca) O. It moves and reacts with the composite oxide to produce free barium (Ba). For example, the reaction scheme of barium oxide (BaO) is as follows.

2BaO + Si → 2Ba + SiO ₂ ------------- ②

BaO + Mg → Ba + MgO -------------- ③

4BaO + Si → 2Ba + Ba ₂ SiO ₄ ----------- ④

In conclusion, the alkaline earth metal oxide formed on the base metal 11 is partially reduced to generate free barium (Ba), and electrons are generated from the free barium (Ba).

Ba Ba ²⁺ + 2e ^- (E generated) ------------- ⑤

The oxide cathode prepared as described above provides an electron emitting material layer that can be used at a current density of 0.5 to 0.8 A / cm ² at an operating temperature of 700 to 800 ° C.

Another conventional cathode, an oxide cathode having a structure as shown in FIG.

That is, the conventional negative electrode having the structure of FIG. ₃ has triple carbonation, nitrocellulose and butyl acetate composed of (Ba, Sr, Ca) CO ₃ , which is the same as the conventional negative electrode having the structure of FIG. 2. (Butylacetate) and a binder (0.1-20% by weight of scandium oxide powder 12) are mixed to form a suspension (suspension) form, and then coated on the base metal 11 by spraying or the like method The electron emitting material layer 13a is formed.

It is recorded in Japanese Patent No. 64-5417 that a conventional anode as shown in FIG. 3 can maintain a current density of ² A / cm ² at a temperature of 700 to 800 ° C., which is a normal oxide cathode.

The reason why high current density is obtained as described above is because Ba ₃ Sc ₄ O _{9, which} is a complex oxide produced by reacting scandium oxide with an alkaline earth metal oxide, that is, BaO, is decomposed in the electron-emitting material layer, and Ba ₃ Sc ₄ The composite oxide of O ₉ can easily decompose at the operating temperature of the cathode to produce free barium, an electron radiation source.

That is, in FIG. 2, free barium is generated by a reducing element such as Si or Mg, but in the case of the conventional negative electrode as shown in FIG. 3, free barium is added by thermal decomposition of a composite oxide of Ba ₃ Sc ₄ O ₉ . Barium deficiency does not occur. Another reason is that some of the complex oxides of Ba ₃ Sc ₄ O ₉ are decomposed into metal scandium (Sc) and present in the electron emitting material layer 13a, thereby improving the conductivity of the electron emitting material layer 123a and thereby conducting the intermediate layer. Since this decreases, it is possible to supplement the current flow stably. The reason shown above is expressed as follows.

2Sc ₂ O ₃ + 3BaO → Ba ₃ Sc ₄ O ₉ ----------- ⑥

Ba ₃ Sc ₄ O ₉ → 3Ba + 3O ₂ + Sc ₂ O ₃ ---------- ⑦

In the case of the conventional negative electrode having the structure of FIG. 3 for the above reason, Japanese Patent No. 64-54 17 claims that a current density of about ^{2 A} / cm ² can be obtained at the normal temperature of the negative electrode of 700 to 800 ° C.

The reason why the conventional negative electrode as shown in FIG. 2 implements a low current density of 0.50.8 A / cm ² at the operating temperature of the negative electrode includes the following problems.

First, the free barium (Ba) generated in the electron-emitting material layer 13 by operating the cathode at high temperature is evaporated to the periphery of the cathode due to the high vapor pressure, thereby reducing the free barium (Ba) as the electron-emitting source. Undesired electron beams can be emitted by attaching barium (Ba) to electrodes and other components.

In addition, when free barium (Ba) is generated from an alkaline earth metal oxide through an aging process, silicon oxide (Si) is formed at the interface between the base metal 11 and the electron-emitting material layer 13 as shown in the above equations (2), (3), (4). An intermediate layer of an oxide or a composite oxide such as SiO ₂ ), magnesium oxide (MgO), and barium silicon oxide (Ba ₂ SiO ₄ ) is formed, and the high resistance of the intermediate layer prevents the flow of current.

In addition, the intermediate layer prevents the reducing element in the gas metal 11 from diffusing into the electron emitting material layer 13, so that free barium (Ba) that emits hot electrons is not sufficiently produced. Therefore, the amount of current radiated from the entire cathode becomes smaller, the current density becomes lower, and the work function becomes larger. Therefore, when the conventional cathode is operated at a high current density of 0.6 to 0.8 A / cm ² or more, there is a problem in that the life is rapidly deteriorated.

In addition, the conventional negative electrode having the structure of FIG. 3 includes the following problems.

5 is a graph showing the pressure of the amount of gas discharged from the scandium oxide powder 12 as the temperature is raised. The vertical axis represents the gas pressure discharged from the scandium oxide powder, and the horizontal axis represents the temperature. As can be seen in FIG. 5, the amount of gas emitted from the scandium oxide powder emits the largest amount of gas around 150 to 350 ° C. The gas thus generated appears to contain a large amount of oxygen.

In the vacuum exhaust process of the cathode ray tube manufacturing process, the temperature of the cathode rises to 200 to 400 ° C. In this case, in the conventional cathode having the structure as shown in FIG. 3, the gas generated in the transfer radiating material layer 13a is surrounded by the cathode and the cathode. It exists in itself and interferes with the electron radiation, and the gas released from the electron emitting material layer during the aging process serves to oxidize the free barium (Ba) that is already generated, thereby reducing the free barium, which is an electron radiation source.

In addition, the problem addressed is that carbon dioxide generated in the electron emission material layer 13a during the vacuum exhaust process is combined with scandium oxide to inhibit the formation of complex oxides of Ba ₃ Sc ₄ O ₉ , thereby preventing the supply of free barium. This reaction scheme is as follows.

Sc ₂ O ₃ + ₃ CO ₃ → Sc ₂ (CO ₃ ) ₃ ------------ ⑧

Due to the problems described above, the conventional cathode is rapidly deteriorated when operating the cathode at a high current density for a long time.

The present invention is to solve the above-mentioned conventional problems, it is formed by mixing the scandium oxide powder and thorium nitrate powder in the electron emitting material layer formed on the upper surface of the gas metal, or by using a separate layer of each of these materials (服 層) The purpose of the present invention is to provide an oxide cathode suitable for improving the electron emission characteristics of the cathode and allowing stable electron radiation for a long time even in a high current density state.

1 is a structural diagram of a color cathode ray tube

2 is a cathode structure diagram for a conventional cathode ray tube

3 is a conventional cathode structure diagram for another cathode ray tube

Figure 4a is a cathode structure diagram of the present invention

Figure 4b is another cathode structure of the present invention

5 is a graph showing the amount of emitted gas against the temperature of the scandium oxide powder

6 is a graph showing the current value for the gas of the cathode

7 is a graph showing the current density and initial current value for the cathode

Explanation of symbols for main parts of the drawings

11: gas metal 12: rare earth metal compound powder

13b: first electron emission layer 14: actinium group metal compound

15 electron emitting material layer 16 second electron emitting material layer

The present invention for achieving the above object can be configured as shown in Figures 5 and 6 showing the embodiment.

That is, as shown in FIG. 5, a small amount of reducing elements such as silicon (Si) or magnesium (Mg) is contained in the upper portion of the cylindrical cathode sleeve 10 in which the cathode heating heater 9 is inserted, and the main component is nickel (Ni). In an oxide cathode having an electron-emitting material layer composed of a metal compound containing at least barium (Ba) on a base metal (11) composed of

The electron emitting material layer is composed of a cathode of a color cathode ray tube composed of an alkaline earth metal compound, a rare earth metal compound 12, and an electron emission material layer 15 composed of an actinium group metal compound 14.

In another configuration, as shown in FIG. 6, a small amount of a reducing element such as silicon (Si) or magnesium (Mg) is contained on the top of the cylindrical cathode sleeve 10 in which the cathode heating heater 9 is inserted, and the main component is nickel. In an oxide cathode in which an electron emitting material layer formed of a metal compound containing at least barium (Ba) is formed on a base metal 11 made of (Ni),

The first electron emitting material layer 13b of which the electron emitting material layer is composed of an alkaline earth metal compound and a rare earth metal compound 12, and the alkaline earth metal compound and actinium group metal compound on the first electron emitting material layer 13b. A second electron emitting material layer 16 composed of (14) is formed, and is made of a cathode of a color cathode ray tube.

In the above configuration, the metal compound containing at least barium (Ba) includes at least barium (Ba), and other alkaline earth metal carbonates such as strontium (Sr) and calcium (Ca), and the rare earth metal compound is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), prasedium (Pr), neodymium (Nd) of the rare earth metal oxide may be composed of at least one or more, actinium group metal compound Silver may be made of at least one of actinium group metal oxides consisting of actinium (Ac), thorium (Th), and prolactinium (Pa), or thorium nitrate.

The manufacturing process of the negative electrode as shown in Figure 4a of the present invention described above is as follows.

First, the scandium oxide powder, which is the rare earth metal oxide powder 12, is heated at a temperature of 800 ° C. or higher for at least 30 minutes, thereby releasing the gas present in the scandium oxide powder. When the powder is heated at a temperature above 1000 ° C., sintering occurs and a suspension cannot be formed.

In addition, the scandium oxide powder is heat-treated at a temperature of 800 to 1000 ° C. for 1 hour in an oxygen-containing hydrogen atmosphere, which is well distributed in the suspension for forming the electron emission layer 15.

In addition, in preparing the thorium nitrate powder, which is the actinium group metal compound 14, it is left unheated or prepared by heating at a temperature of less than 500 ° C even when heated. This is because the nitric acid (NO ₃ ) constituting thorium nitrate evaporates to a gas at a temperature of 500 ° C. or more, rather it is not well distributed in the electron emitting layer.

It is mixed with a binder composed of scandium oxide powder, thorium nitrate powder, (Ba, Sr, Ca) CO ₃ prepared above, triple carbonation, nitrocellu lose, and butyl acetate (Butylacetate). It is made in the form of a suspension (suspension). The suspension is completed by setting the weight ratio of scandium oxide powder in the suspension to 10% or less and the weight ratio of thorium nitrate powder 14 to 5% or less.

Subsequently, nickel is the main component, and the electrospinning material layer 15 of the cathode proposed by the present invention is coated on the base metal 11 containing a small amount of reducing elements such as silicon (Si) or magnesium (Mg) by spraying or the like. Will form).

In the cathode of the present invention having the structure of FIG. 4A, the alkali earth metal carbonate constituting the electron emission material layer 15 is converted into an alkali earth metal oxide in the vacuum exhaust process of the electron tube, wherein the carbon dioxide in the electron emission material layer 15 is changed to carbon dioxide. Gas is generated (Scheme ①). Conventionally, in the case of the negative electrode, the generated carbon dioxide reacts with scandium oxide to reduce the performance of scandium oxide (Scheme ⑧), but in the present invention, the generated carbon dioxide reacts with the thorium nitrate powder before reacting with the scandium oxide powder to generate thorium carbonate. (Scheme ⑨) The degradation of scandium oxide performance does not occur.

In the aging process, the electron emission material layer 15 is heated to a temperature of 900 to 1000 ° C., and the alkali earth metal oxide reacts with the reducing metal present in the gas metal 11 to generate free barium (Ba) as an electron radiation source. (Scheme ② to ⑤).

In addition, scandium oxide powder reacts with barium oxide in alkaline earth metal oxides to produce Ba ₃ Sc ₄ O ₉ , a composite oxide, which is present in all parts of the electron emitting material layer, and pyrolyzes during operation of the cathode to generate free barium. ⑥, ⑦).

In addition, thorium nitrate reacts with carbon dioxide in a vacuum exhaust process to change to thorium carbonate, but in the aging process, thorium carbonate releases carbon dioxide and reacts with barium oxide in the electron emitting layer 15 to generate free barium as an electron radiation source ( Scheme iv) It is possible to perform stable electron emission at high current density. Looking at the above operation through the reaction scheme is as follows.

(Ba, Sr, Ca) CO ₃ → (Ba, Sr, Ca) O + CO ₂ -------------- ①

Th (NO ₃ ) ₄ + 4CO ₂ Th (CO ₂ ) ₄ + 4NO ₃ ------------- ⑨

2Sc ₂ O ₃ + 3BaO → Ba ₃ Sc ₄ O ₉ ----------- ⑥

Ba ₃ Sc ₄ O ₉ → 3Ba + 3O ₂ + Sc ₂ O ₃ ---------- ⑦

Th (CO ₂ ) ₄ + ₂ BaO 2Ba + ThO + 4CO ₂ ----- ⑩

A negative electrode manufacturing process of FIG. 4B having another structure of the present invention is as follows.

First, scandium oxide powder, which is a rare earth metal oxide powder 12, and thorium nitrate, which is an actinium group metal compound powder 14, prepared when a cathode having a structure as shown in FIG. 4A are prepared are prepared in the same manner. Next, triple carbonation consisting of (Ba, Sr, Ca) CO ₃ and the scandium oxide powder prepared above were mixed and mixed with a binder consisting of nitrocel lulose and butyl acetate (Butylacetate). After the suspension is prepared and cut on the base metal 11 by spraying or the like to form the first electron emitting material layer 13b. Thereafter, triple carbonation consisting of (Ba, Sr, Ca) CO ₃ and thorium nitrate powder prepared above were mixed and mixed with a binder consisting of nitrocel lulose and butyl acetate (Butylacetate). After preparing a suspension and coating the first electron emitting material layer 13b by spraying or the like to form a second electron emitting material layer 16, the cathode of the present invention is completed.

Referring to the operation of the present invention cathode as shown in Figure 4b.

First, the cathode tube is changed from alkaline earth metal carbonate to alkaline earth metal oxide in the vacuum exhaust process, and carbon dioxide, which is a byproduct, reacts with thorium nitrate distributed in the second electron-emitting material layer 16. The performance of the scandium oxide powder does not decrease (Scheme ① or ⑨).

In addition, in the case of FIG. 4A, since scandium oxide and thorium nitrate are distributed together in the electron emission material layer 15, there is a problem that the gas generated in the electron gun portion on the cathode may react with the scandium oxide powder in the electron emission material layer. In the case of the cathode as shown in FIG. 4B, a gas generated in the electron gun first reacts with the thorium nitrate of the second electron emitting material layer 16 because the electron emitting material layer 16 containing thorium nitrate is present thereon. By reacting the reactions ⑥, ⑦, ⑨, and 않고 without degrading the performance of, it is possible to smoothly generate free barium, which is an electron radiation source, and to perform stable electrospinning.

In the aging process and the operation of the cathode, free barium is generated by the same operation as in the reaction of 2 through 5, but silicon oxide (SiO), magnesium oxide (MgO), An intermediate layer of an oxide or a composite oxide, such as barium silicon oxide (Ba ₂ SiO ₄ ), is also formed. However, in the case of the cathode having a structure as shown in FIG. 4B, the scandium in the electron-emitting material layer 13B is formed of silicon oxide (SiO) and magnesium oxide (MgO) because the electron-emitting material layer 13b containing scandium oxide is present directly on the base metal. ), By reducing the production of oxides or complex oxides such as barium silicon oxide (Ba ₂ SiO ₄ ), or by breaking the formed intermediate layer (Scheme ⑪, ⑫, ⑬), the reducing metal present in the base metal (11) As a result, free barium serving as an electron radiation source is generated by reacting with the barium oxides of the electron emitting material layers 13b and 16 to realize stable electron emission.

2Sc ₂ O ₃ + 2Ba ₂ SiO ₄ → 4Sc + 4BaO + 2SiO ₂ + 3O ₂ ------ ⑪

2Sc + 3MgO → Sc ₂ O ₃ + 3MgO ---------- ⑫

4Sc + 3SiO ₂ → 2Sc ₂ O ₃ + 3Si --------- ⑬

Figure 6 is a graph showing the rectification value for the cathode as a result of the bipolar tube test is a graph showing the current value from the cathode structure of Figures 2, 3, 4a, 4b with respect to time.

In the experiment of FIG. 6, after checking the initial current value for each cathode, the gas is injected into the bipolar tube to reduce the vacuum degree, thereby preventing the current value from the cathode, and increasing the vacuum degree in the bipolar tube after about 40 minutes. The effect of the cathode on the gas can be seen. In other words, it can be seen how quickly the initial current value recovers.

Arrows (⇒) and hearts (♥) shown in FIG. 6 indicate that each cathode represents an 80% recovery time of the super value current. As can be seen from FIG. 6, the recovery time of the conventional negative electrode having the structures of FIGS. 2 and 3 is longer than 40 minutes and 30 minutes, respectively, whereas the negative electrode of the present invention having the structures of FIGS. 4A and 4B is 25, respectively. It can be seen that the recovery time is about twice as fast as the conventional minute and 15 minutes.

Another effect of the negative electrode of the present invention is the same as FIG. FIG. 7 is a chart showing initial current values and current densities of respective cathodes. In the case of the initial current values, the cathode of the present invention shown in FIGS. 4A and 4B shows a value 1.5 times larger than that of the conventional cathode. In the case of the current density, it can be seen that a large value of about 2-4 times.

As described above, the present invention is to form a single layer formed by mixing scandium oxide powder and thorium nitrate powder in the electron emitting material layer formed on the upper surface of the gas metal having a cathode structure, or these materials are separately formed in the electron emitting material. By forming and forming in a multilayer, the recovery time of the initial current value is quick, and the oxide cathode can be obtained which can perform stable electron emission for a long time even in a high current density state by improving the initial current value and current density.

Claims (11)

At least barium (Ba) is placed on the base metal (11) containing a small amount of reducing elements such as silicon (Si) or magnesium (Mg) on the top of the cylindrical cathode sleeve in which the cathode heating heater is inserted. In an oxide cathode having an electron emitting material layer composed of a metal compound comprising: The cathode of the color cathode ray tube, characterized in that the electron emitting material layer is composed of an alkaline earth metal compound, a rare earth metal compound and an actinium group metal compound. The method of claim 1, The rare earth metal compound is at least one rare earth metal oxide of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), pracedium (Pr) and neodium (Nd) Cathode of cathode ray tube. The method of claim 1, An anode of a color cathode ray tube, characterized in that the actinium group metal compound is at least one of an oxide of actinium (Th), thorium (Th), and a prolactinium (Pa). The method of claim 1, The cathode of a color cathode ray tube, characterized in that the electron-radiating material layer contains at least barium (Ba), in addition to an alkaline earth metal compound containing strontium (Sr) and calcium (Ca), and scandium oxide and thorium nitrate. . The method of claim 4, wherein A cathode of a color cathode ray tube, wherein scandium oxide is heated at 800 to 1000 ° C. The method of claim 4, wherein A cathode of a color cathode ray tube, characterized in that less than 10% by weight of scandium oxide and 5% by weight of thorium nitrate in the electron-emitting material layer. At least barium (Ba) is placed on the base metal (11) containing a small amount of reducing elements such as silicon (Si) or magnesium (Mg) on the top of the cylindrical cathode sleeve in which the cathode heating heater is inserted. In an oxide cathode in which an electron-emitting material layer composed of an alkaline earth metal compound is formed, The electron emitting material layer is a first electron emitting material layer composed of an alkaline earth metal compound and a rare earth metal compound and a second electron emitting material layer composed of an alkaline earth metal compound and an actinium group metal compound on the first electron emitting material layer. The cathode of the color cathode ray tube, characterized in that is formed. The method of claim 7, wherein A color cathode ray tube characterized in that the rare earth metal oxide is at least one oxide of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), pracedium (Pr), and neodium (Nd). Cathode. The method of claim 7, wherein An anode of a color cathode ray tube, characterized in that the actinium group metal compound is at least one of an oxide of actinium (Th), thorium (Th), and a prolactinium (Pa). The method of claim 7, wherein A cathode of a color cathode ray tube, wherein scandium oxide is heated at 800 to 1000 ° C. The method of claim 7, wherein A cathode of a color cathode ray tube, characterized in that the scantium oxide is 10 wt% or less and the thorium nitrate is 5 wt% or less in the electron emitting material layer.