KR20050025849A - Cathode for crt and method of making thereof - Google Patents

Abstract

A cathode and a method for manufacturing the same are provided to lengthen the useful life of the cathode, by reducing the size of crystal grain such that the surface area of the gas metal contacting an electron radiation material layer is increased. A cathode comprises a cylindrical sleeve where a cathode heater is inserted; a gas metal welded to the top of the sleeve; and an electron radiation material layer formed at the top of the gas metal. The electron radiation material layer contains barium as a main component, and the gas metal contains nickel as a main component. The crystal grain of the gas metal has a mean size of 1‘í to 20‘í.

Description

Cathode for cathode ray tube and its manufacturing method {Cathode For CRT and Method of Making

The present invention relates to a cathode used in an electron gun for a cathode ray tube and a method of manufacturing the same, which not only can smoothly radiate electrons during the operation of the cathode, but also is not significantly affected by an intermediate layer that interferes with electron emission. The present invention relates to a cathode for a cathode ray tube and a method of manufacturing the same, which can maintain a long life characteristic.

In general, the cathode ray tube neck portion is provided with an electron gun, and the electron beam emitted from the electron gun is deflected by the deflection yoke to be scanned by a fluorescent film formed on the inner surface of the cathode ray tube panel to reproduce an image. The electron gun is provided with a cathode structure for emitting an electron beam and an electrode structure for focusing and accelerating the emitted electron beam by being fixed by bead glass.

As shown in FIG. 1, a cathode structure, which is a component of the electron gun, is first fixed to a cylindrical sleeve 2 in which a cathode heating heater 4 is inserted, and fixed to an upper end of the sleeve, such as silicon (Si), magnesium (Mg), and the like. A base metal (1) containing a trace amount of a reducing element and having a main component of nickel (Ni) is provided.

In addition, the holder 5 is welded to the lower end of the sleeve to support the sleeve. The base metal has barium (Ba) as a main component, and other alkali metal carbonates such as strontium (Sr) and calcium (Ca). An electrospinning material layer (3) is provided.

Looking at the manufacturing method and operation principle of a cathode for a conventional cathode ray tube having such a structure as follows.

FIG. 2 is an exploded view of FIG. 1, where (a) is a cap-shaped base metal 1, (b) is a cylindrical sleeve 2, and (c) is a holder 5, and FIG. ) Is the heater 4.

First, the cylindrical sleeve 2 is inserted through the b) part of the holder 5 into the a) part to be fastened as shown in FIG. 1 and then welded. Subsequently, a base metal having a main component of nickel (Ni) in a cap shape as shown in FIG. (A) is covered with an upper end of a sleeve made of an alloy of chromium (Cr) and nickel (Ni), followed by welding.

Subsequently, a furnace having a high temperature of 1000 ° C. or higher is prepared, and the inside of the furnace is subjected to a heat treatment for about 5 minutes on the base metal and the sleeve assembly in a wet hydrogen atmosphere. In this way, the chromium present in the sleeve is oxidized to chromium oxide, and the sleeve becomes black, resulting in a sleeve having high thermal emissivity and excellent thermal conductivity. This effectively absorbs the heat radiated from the heater, and serves to easily transfer the absorbed heat to the gas metal.

And on the base metal is an alkaline earth metal carbonate composed mainly of barium (Ba), preferably the alkaline earth metal carbonate consisting of a ternary metal carbonate represented by (Ba, Sr, Ca) CO3 is an electron-emitting material layer To form.

A process of forming the electron emitting material layer will be described. First, ternary carbonate (Triple Carbonation) consisting of (Ba, Sr, Ca) CO3 is mixed with an organic solvent such as nitrocellulose to form a suspension (suspension). In addition, when the suspension is coated on the base metal by spraying or electrodeposition, an electron-emitting material layer is formed.

In order to use the cathode fabricated as described above in the cathode ray tube, the cathode is first mounted on the electron gun, the electron gun equipped with the cathode is inserted in the cathode ray tube, and then heated to about 600 ° C. to have an exhaust process. In addition, when the cathode for the cathode ray tube subjected to the exhaust process is subjected to an activation process of heating to a high temperature of 900 to 1000 ° C., the electron-emitting material layer has a semiconductor property. Subsequently, when a predetermined voltage is applied to the electron gun, electrons are radiated to reproduce an image.

Looking at the change of the electron-emitting material layer of the conventional negative electrode structure undergoing the above process, first, most of the heat emitted from the heater is transferred to the sleeve by the radiation (radiation), most of the heat transferred to the sleeve is heat conduction (Heat) Is transferred to the base metal and the holder and only a portion of the heat is lost to the surroundings by radiation.

The heat transferred to the gas metal is transferred to the electron-emitting material layer by heat conduction, wherein the heat transferred to the electron-emitting material layer reacts the alkali earth metal carbonate reactions of the following reactions ①, ②, ③, ④, and ⑤. To let electrons pass through.

BaCO ₃ (heating) → BaO + CO ₂ ↑ ---------- ①

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

2BaO + Si → Ba + SiO ₂ ---------- ③

BaO + Mg → Ba + MgO ---------- ④

Ba → Ba ²⁺ + 2e- (Generation) ---------- ⑤

Figure 3 is an actual measurement of the gas metal surface of the conventional negative electrode structure that went through the manufacturing process and process as described above with an electron microscope.

As shown in Figure 3 it can be seen that the crystal grains of the base metal are formed in an average size of about 30㎛. This is because during the fabrication of the anode structure, the heat treatment is performed at a temperature of 1000 ° C. or higher and a wet hydrogen atmosphere, and the grains of the gas metal composed of 99% or more nickel are greatly grown as the cathode injected into the electron tube undergoes an activation step of 1000 ° C. or higher. to be. When heat treatment is performed at a temperature of 1000 ° C. or higher and a wet hydrogen atmosphere during fabrication of the negative electrode structure, the grains of the base metal are already grown to about 10 μm to 20 μm, and the negative electrode structure is put into an electron tube and subjected to an activation process of 1000 ° C. or higher. The grain size of the base metal grows to 30 μm or more, so that the surface area of the base metal in contact with the electron-emitting material layer is reduced. This means that the surface area of the base metal in contact with the electron-emitting material layer is small because the grain size of the base metal is increased.

As such, when the surface area in which the base metal is in contact with the electron emitting material layer decreases, the possibility of the electron emitting material reacting with the reducing agent present in the base metal is low, and thus, free barium (Ba), which is an electron radiating source, is not easily generated. Come.

The cracks between the grains and the grains of the base metal are important passages for the reducing agent present in the base metal to move to the surface of the base metal, but as the grain size increases, the number of such cracks decreases as a whole. Since the present reducing agent does not react smoothly with the electrospinning material, there is a problem that the lifetime of the negative electrode deteriorates during long time operation.

In addition, reaction products such as Ba2SiO₄, SiO2, MgO, etc. are formed at the boundary between the electron-emitting material layer and the gas metal as shown in the reaction formulas ②, ③, and ④ during the manufacturing process and operation of the cathode structure as described above. It is also created in the crack between the grains and the grains.

The reaction product thus formed forms an intermediate layer and inhibits the diffusion of reducing agents such as magnesium (Mg) and silicon (Si) in the gas metal into the electron-emitting material layer, thereby suppressing the formation of free barium (Ba) as an electron-emitting source. Done.

Therefore, the conventional negative electrode structure results in a rapid deterioration of the service life in a long time operation.

In addition, the intermediate layer has a problem of limiting current density by interrupting the flow of electron emission with high resistance.

The cathode thus formed does not satisfy the characteristics of the high current density, long life cathode required by television and other display devices in accordance with the trend of high definition and large size.

The present invention is to solve such a problem in the prior art, in the cathode for cathode ray tube cathode by reducing the grain size to increase the surface area of the base metal in contact with the electron-emitting material layer, the reducing agent present in the base metal during operation of the cathode It is not only able to generate free barium, which is an electron radiation source, by reacting with a lot of contact with electron emitting materials, but also not affected by the intermediate layer generated during the reaction process. It is an object of the present invention to provide a cathode for a cathode ray tube and a method of manufacturing the same.

The first technical means of the present invention for achieving the above object is a cylindrical sleeve in which a heater for heating the cathode is inserted, a base metal welded to the upper end of the sleeve, a holder welded to the lower end of the sleeve to support the sleeve, and the base In the cathode for a cathode ray tube including an electron-emitting material layer formed on the upper surface of the metal, the electron-emitting material layer is made of barium (Ba), the base metal is made of nickel (Ni), the base metal The grain size is characterized by having a range of 1㎛ ~ 20㎛.

In addition, the second technical solution is a cylindrical sleeve in which a heater for cathodic heating is inserted, a base metal welded to the upper end of the sleeve, a holder welded to the lower end of the sleeve to support the sleeve, and electromagnetic radiation formed on the base metal upper surface. In the cathode production method for a cathode ray tube including a material layer, the gas metal is characterized in that the heat treatment in a furnace in a dry hydrogen atmosphere and the temperature of 500 ℃ ~ 800 ℃.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 4 shows a cathode structure for a cathode ray tube according to the present invention.

The structure of the negative electrode structure is the same as that of a conventional negative electrode structure, and a cylindrical sleeve 22 in which a cathode heating heater 44 is inserted, and a base metal 11 having a main component of nickel on the upper end of the sleeve and a trace amount of a reducing element. It is fixed, the lower end of the sleeve is welded to the holder 55 to support the sleeve, the electron emitting material layer 33 composed of alkaline earth metal carbonate is formed on the upper surface of the base metal.

The manufacturing process of the negative electrode of the present invention having such a structure is as follows.

First, a cylindrical sleeve made of an alloy of chromium (Cr) and nickel (Ni) is subjected to heat treatment for about 5 minutes or more in a furnace at a high temperature and a wet hydrogen atmosphere of 1000 ° C. or higher to oxidize chromium present in the sleeve to be chromium oxide. When reacted with the sleeve, the sleeve becomes black by an oxidation reaction, thereby forming a sleeve having high thermal radiation rate and excellent thermal conductivity.

In addition, the main metal is nickel (Ni) and contains a small amount of reducing elements such as magnesium (Mg) or silicon (Si) in a gas in a temperature range of 500 ° C. to 800 ° C. and a furnace in a dry hydrogen atmosphere for about 10 minutes. Heat treatment is performed.

After that, the welding of the sleeve 3 and the base metal completes the cathode assembly.

On the base metal 22 of the negative electrode assembly, an alkaline earth metal carbonate having a barium (Ba) as a main component forms an electron emission material layer. At this time, the electron-emitting material layer is preferably formed of an alkaline earth metal carbonate consisting of a ternary metal carbonate represented by (Ba, Sr, Ca) CO3.

As described above, the electron-emitting material layer formed on the base metal is prepared by first mixing ternary carbonate (Triple Carbonation) composed of (Ba, Sr, Ca) CO3 with an organic solvent such as nitrocellulose. Suspension), and then the suspension is coated on the base metal by spraying or electrodeposition to form a layer of electrospinning material.

The cathode manufactured as described above first has the cathode mounted on the electron gun, the electron gun equipped with the cathode inserted into the cathode ray tube, and then has an exhaust process while being heated.

Thereafter, the cathode for the cathode ray tube subjected to the exhaust process undergoes an activation process, and the electron-emitting material layer has a semiconductor property, and when a predetermined voltage is applied thereto, electrons are radiated toward the screen to reproduce an image.

FIG. 5 is an actual view of the surface of the base metal, which is a component of the anode structure of the present invention, after the manufacturing process of the cathode structure as described above using an electron microscope.

As shown in FIG. 5, it can be seen that the size of the grains of the base metal is substantially in the range of 1 μm to 20 μm. The grain size is in the range of approximately 1 μm to 20 μm, but there may be a few grains outside the above range. Even in this case, it can be seen that the average size of the grains of the base metal is approximately 20 μm or less. In addition, it may not be easy to determine the size because the crystal grain is spherical or the cross section is atypical rather than circular or elliptical. Even in this case, it can be seen that the average value of the cross-sectional area of the crystal grains is 100 × πm ² or less.

This heat treatment of the base metal at a temperature of about 500 ° C. to 800 ° C. and a dry hydrogen atmosphere during the fabrication of the anode structure brings only the effect of stress removal and cleaning of the base metal, and no grain growth occurs.

In addition, the fabricated cathode structure is mounted on an electron gun, put into an electron tube, and undergoes an activation process of 1000 ° C. or more. At this time, it can be seen that the grain size of the base metal 22 grows up to about 10 μm.

As described above, the negative electrode structure of the present invention may not only maximize thermal efficiency by different heat treatments of the sleeve 3 and the base metal 22, but also achieve efficient electrospinning.

That is, the sleeve is heat treated in a high temperature and a wet hydrogen atmosphere of 1000 ℃ or more to provide a sleeve having a high thermal radiation rate and excellent thermal conductivity. This effectively absorbs the heat radiated from the heater, and serves to easily transfer the absorbed heat to the gas metal.

The gas metal is heat treated for about 10 minutes in a furnace at a temperature of about 500 ° C. to 800 ° C. and in a dry hydrogen atmosphere to form a negative electrode structure, and the gas metal surface of the negative electrode structure is subjected to a series of processes by injecting the same into an electron tube. Small crystal grains are distributed at.

As a result, the contact area between the base metal and the electron radiating material becomes large, and the reducing agent of the base metal reacts with the electron radiating material a lot to smoothly generate free barium as an electron radiating source.

In addition, since there are many cracks between the grains and the grains, the reducing agent present in the gas metal is much easier to move to the surface of the gas metal, so that it can react smoothly with the electron radiating material to easily generate free barium (Ba) as an electron radiation source. do.

Meanwhile, even when the cathode of the present invention is operated for a long time, the alkaline earth metal carbonate constituting the electron emitting material layer reacts to generate intermediate products such as Ba 2 SiO 4, SiO 2, MgO, and the like. It is formed at the boundary of the electron-emitting material layer and serves as an intermediate layer, thereby preventing the reducing agent present in the gas metal from diffusing to the surface.

However, in the present invention, the grain size of the surface of the base metal is formed to be small so that the reducing agent present in the base metal reacts smoothly with the electron-emitting material, thereby preventing the life from deteriorating rapidly.

Figure 6 is a graph showing the lifetime data for the conventional negative electrode structure and the negative electrode structure of the present invention.

In other words, the maximum current emitted from the cathode (Maximum Cathode Current) shows the deterioration rate that appears over time, A is the lifetime degradation curve of the cathode structure of the present invention, B is the lifetime degradation curve of the conventional cathode structure It represents.

As shown, it can be seen that the negative electrode structure of the present invention does not show severe deterioration even after a long time.

7 is a graph showing the life of the anode structure according to the grain size of the base metal.

As shown in FIG. 7, the life characteristics are excellent when the grain size of the base metal is 20 μm or less, but the life characteristics are poor when the grain size is 30 μm or more.

This may be a result of the small surface area of the gas metal in contact with the electron-emitting material, but the cracks between the grains and grains during the long-term operation of the cathode block the cracks formed by intermediate layers such as Ba2SiO4, SiO2, MgO, and the reducing agent in the gas metal. It can't diffuse to the surface and can't react with the electron-radiating material, so its life is worse.

As such, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, the above-described embodiments are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the appended claims rather than the foregoing description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the present invention reduces the grain size to increase the surface area of the base metal in contact with the electron-emitting material layer in the cathode for the cathode ray tube, and the reducing agent present in the base metal during the operation of the cathode causes a lot of contact with the electron-emitting material. Not only does it react freely to generate free barium, which is an electron radiation source, but also is not significantly affected by the intermediate layer generated during the reaction process, and thus the lifespan characteristics of the cathode can be maintained for a long time.

1 is a schematic view showing a cathode structure for a conventional cathode ray tube.

Figure 2 is an exploded view of a conventional cathode ray structure for cathode ray tubes.

3 is a view showing a gas metal surface state of the conventional negative electrode structure.

Figure 4 schematically shows a cathode structure for a cathode ray tube of the present invention.

5 is a view showing a gas metal surface state of the negative electrode structure according to the present invention.

Figure 6 is a view showing the life characteristics of the conventional negative electrode structure and the negative electrode structure of the present invention.

7 is a view showing the life characteristics according to the gas metal grain size of the negative electrode structure.

***** Explanation of symbols for the main parts of the drawing *****

1,11 gas metal 2,22 sleeve

3,33: electrospinning material layer 4,44: heater

5,55: holder

Claims (4)

In the cathode for a cathode ray tube comprising a cylindrical sleeve in which a heater for heating a cathode is inserted, a base metal welded to an upper end of the sleeve, and an electron emitting material layer formed on an upper surface of the base metal, An average size of the crystal grains of the base metal has a range of 1㎛ ~ 20㎛ negative electrode for cathode ray tubes. The method of claim 1, A cathode for a cathode ray tube, characterized in that the maximum size of the grain of the base metal is 20㎛. The method of claim 1, The cathode for a cathode ray tube, characterized in that the average value of the cross-sectional area of the grains of the base metal is 100 X π μm ² or less. The method according to any one of claims 1 to 3, The base metal is nickel (Ni) as a main component and a cathode for a cathode ray tube, characterized in that it contains a trace amount of reducing elements.