KR20010100644A - Cathode for CRT - Google Patents

Abstract

The present invention relates to an anode-impregnated cathode structure for cathode ray tubes, which has a structure capable of preventing heat shrinkage, and thus prevents reduction of the ignition point voltage, thereby enabling stable high current density hot electron emission during a long time operation. . According to the constitution, a cathode for a cathode ray tube having a sleeve mainly composed of tantalum (Ta) and an inner surface of a blackening layer including tungsten (W) and alumina (Al ₂ O ₃ ) is disposed between the inner surface of the sleeve and the blackening layer. It is a technology consisting of a cathode for a cathode ray tube, characterized in that the site layer is formed.

Description

Cathode for cathode ray tube {Cathode for CRT}

The present invention relates to a cathode for a color cathode ray tube, and in particular to a structure capable of preventing heat shrinkage on the cathode sleeve, thereby preventing the reduction of the ignition point voltage through the cathode ray tube capable of stable high current density hot electron emission during long time operation It relates to a needle-shaped cathode structure.

In the color cathode ray tube, as shown in FIG. 1, a panel 1 having a fluorescent film formed on an inner surface thereof and a funnel 2 coated with conductive graphite on an inner surface thereof are fused with glass, and a neck portion 3 of the funnel 2 is formed. It is equipped with an electron gun 4 for generating an electron beam, and a cathode 5 which emits hot electrons is built in the electron gun, and the cathode is formed by a voltage applied to a plurality of electrodes 6 adjacent to the heat and the cathode. Hot electrons are emitted from the cathode.

Inside the panel 1, a shadow mask 7, which is a color-selective electrode, is supported by a frame, and a deflection yoke 8 for deflecting the electron beam from side to side is mounted on the outer circumferential surface of the funnel.

In the cathode ray tube configured as described above, when the image signal is input to the electron gun, hot electrons are emitted from the cathode of the electron gun, and the emitted electrons are accelerated and focused toward the panel by the voltage applied from each electrode of the electron gun. The propagation path of the electron beam is adjusted by the magnetic field of the magnet mounted on the neck of the funnel, and the adjusted electron beam is scanned on the inner surface of the panel by the deflection yoke 9, and the deflected electron beam is shadow mask coupled to the inner frame of the panel. Color selection is performed while passing through the thin slot (7), and the selected electron beams collide with each fluorescent film on the inner surface of the panel to emit light to reproduce an image signal.

In the above structure, the impregnated cathode 5 is compressed into a heat-resistant metal powder such as tungsten (W) or molybdenum (Mo) as shown in FIG. 2 and then sintered into a pellet having a pore of 20 to 25% by BaO, CaO, Al. _A gaseous metal (9) obtained by melting and impregnating an electron-spinning material such as ₂ O ₃ in a hydrogen atmosphere is formed, and the gaseous metal (9) is formed inside a cathode cup (10) made of molybdenum (Mo) or tantalum (Ta). Insert and laser weld the sides.

In addition, a cylindrical cathode sleeve 11 made of heat-resistant metal (Mo or Ta) is attached and fixed to an outer surface of the cathode cup 10, and the cathode sleeve 11 has an inner surface for enhancing heat radiation efficiency from the heater 12. 11a is formed of a blackening layer, and the outer surface 11b is formed of a double film not blackened. The lower end of the sleeve 11 and the holder 14 are connected to the ribbon 13.

In order to operate the impregnated cathode, heat must first be transferred from the heater 12 to the pellets, and an oxide of BaO or the like impregnated using the transferred heat reacts with a metal such as tungsten (W) to reduce the barium. (Ba) An atom is generated to form an electron generating source.

In addition, barium (Ba) atoms absorb this heat to emit electrons. This can be expressed as follows.

6 (Ba0)₃ Al₂O₃+ W = 6 (BaO)₂Al₂O₃+ Ba₃WO₆+ 3Ba

Ba + heat = Ba ²⁺ + 2e

At this time, heat from the heater 12 is transferred to the base metal 9 through two paths. First, radiant heat is transmitted from the heater 12 to the bottom of the cup 10, and heat is transferred to the contact surface of the base metal 9 and the cup 10 through the cup 10 by a heat conduction mechanism. The other is that radiant heat is transferred from the heater 12 to the sleeve 11, a part of which causes radiant heat loss to the outer surface of the sleeve 11 and the other part of the cup 10 and the sleeve 11 through the heat conduction mechanism. Gina is the heat transfer to the contact surface of the cup 10 and the base metal (9).

That is, there are two paths of heat: heat transfer in the order of heater 12-cup 10-gas 9 and heat transfer in the order of heater 12-sleeve 11-cup 10-gas 9. . It can be seen that the heat of the heater 12 is transferred to the base metal 9 via the heat resistant layer such as the cup 10 or the sleeve 11 through the two paths. The state of the sleeve 11 should be designed to have an optimal heat transfer condition such as using a material having excellent thermal conductivity or generating a blackening layer only on the inner surface 11a in order to increase radiation efficiency. The impregnated cathode is a method of blackening the inner surface of a tantalum (Ta) sleeve, and in forming a thermal radiation coating on the inner surface of the sleeve constituting a part of the hot electron emission cathode, tungsten (W) and alumina (Al ₂ O) as the thermal radiation coating material. ₃ ) depositing a material having a composition of about 50:50 on the surface of the molybdenum (Mo) metal wire, and then penetrating the deposited metal wire through the cylindrical sleeve opening, and heating the metal wire by energization to deposit the metal wire. Is deposited on the inner surface of the sleeve.

However, in the blackening using tungsten-alumina as the heat radiation coating material, there is a problem that the sleeve of the impregnated cathode is thermally contracted during long time operation. The cause of such heat shrinkage is that the oxygen of the alumina reacts with the diffusion movement into the tantalum to convert tantalum having a melting point of about 2990 ° C. into tantalum oxide (TaO ₅ ) having a melting point of about 1800 ° C. As such, when the sleeve material is converted into a material having a low melting point, crystal growth occurs at a cathode operating temperature of about 1000 ° C. to coarsen the crystal.

This coarsening of crystals entails volume shrinkage, which causes thermal contraction. As a result of the heat shrinkage, the distance between the cathode and the control electrode is increased and the brightening voltage is reduced. The bright spot voltage is a factor that quantifies the voltage relationship taking into account the geometrical characteristics of the negative electrode and the control and acceleration electrodes, and the bright spot voltage decreases as the distance between the negative electrode and the control electrode increases.

In addition, when the bright spot voltage decreases, the voltage applied to the cathode decreases, thereby reducing the hot electron current density during the cathode operation for a long time.

From the above phenomena, a high resolution, high definition cathode of a large screen with stable current density for a long time cannot be manufactured and should be improved.

And known techniques related to the internal blackening of the tantalum sleeve is as follows.

In Japanese Patent Laid-Open No. 3-105826 (Toshiba, 1989, 9), the inner surface of the tantalum material sleeve is oxidized to form a blackening layer of Ta0 _X (X = 1 to 2). This is accomplished by holding the outside of the sleeve in an argon (Ar) atmosphere and applying heat from the outside while flowing air into the sleeve.

In addition, Japanese Patent Application Laid-open No. Hei 5-299008 (Toshiba, 1002,4) forms a blackening film containing a high melting point metal nitride (TaN) and an inorganic binder on the inner surface of the sleeve.

It applies a slurry containing black nitride powder of a high melting point metal and an inorganic binder, and after baking, it is baked in a reducing atmosphere to form a blackening film.

The present invention solves the above-mentioned problems and differs from the above-described Japanese Patent Application. The present invention provides a tungsten forming blackening layer by forming an oxygen diffusion preventing layer between the inner surface of the blackening layer and the inner surface of the sleeve, which constitute a heat radiation coating material. -The purpose of this study is to prevent the oxygen of alumina (Al ₂ O ₃ ), which is the cause of blackening heat shrinkage, in the alumina composition from being diffused into tantalum (Ta) and reacting to change the melting point to low tantalum oxide (Ta0 ₅ )

1 is a structural diagram of a cathode ray tube

2 is a conventional impregnated cathode structure diagram

3 is a cathode structure diagram of the present invention

4 is a state diagram for depositing a heat radiation coating material on the inner surface of the cathode sleeve

Figure 5a is a micrograph showing the particle size of the conventional inner sleeve sleeve material

Figure 5b is a micrograph showing the particle size of the inner material of the negative electrode sleeve of the present invention

6 is a graph showing the change in the bright spot voltage according to the lifetime

Explanation of symbols for main parts of the drawings

15: cathode sleeve 15a: blackening inner surface 15b: inner sleeve

15c: oxidative diffusion barrier layer

The present invention for achieving the above object is a cathode for a cathode-ray tube having a sleeve having a main component of tantalum (Ta) and a blackening layer inner surface of tungsten (W) and alumina (Al ₂ O ₃ ), the inner surface of the sleeve And a silicide site layer formed between the blackening layer and the cathode for cathode ray tubes.

The silicide layer is composed of a silicide layer containing at least one of molybdenum silicide (MoSi ₂ ) and tantalum silicide (TaSi ₂ ).

Figure 3 is a cross-sectional view showing a cathode structure of the present invention, except for the sleeve structure is the same as the conventional structure shown in FIG.

According to the present invention, an oxygen diffusion preventing layer 15c is formed on an inner surface 15b of a tantalum (Ta) sleeve forming a part of the impregnated cathode sleeve 15, and an oxide-containing blackening layer inner surface 15a is formed thereon. It is composed of a structure.

In detail, the formation method described above may be performed by first forming at least one of molybdenum silicide (MoSi ₂ ) or tantalum silicide (TaSi ₂ ) as an oxygen diffusion preventing material on the surface of the molybdenum (Mo) metal wire, and then An oxygen diffusion preventing material formed in the metal wire by penetrating through the opening of the sleeve 15 and energizing the metal wire is deposited on the inner surface 15b of the sleeve to form the oxygen diffusion preventing layer 15c. Thereafter, a material composed of tungsten-alumina is deposited on the oxygen diffusion preventing layer 15c as a heat radiation coating material, and the metal wire is energized and heated to form an inner surface 15a of the blackening layer.

The molybdenum silicide (MoSi ₂ ) used as the oxygen diffusion preventing material has a melting point of 2052 ° C. and, once deposited on the inner surface of the sleeve 15b mainly composed of tantalum (Ta), the silicon (Si) component in the molybdenum silicide (MoSi ₂ ) This transfer forms tantalum silicide (TaSi ₂ ) having a melting point of 2197 ° C. to form molybdenum-tantalum composite silicide.

This composite silicide prevents oxygen from alumina (Al ₂ O ₃ ) from diffusing into tantalum (Ta), has excellent chemical stability at high temperature, and tantalum oxide formed by reacting with diffusion of oxygen from alumina into tantalum. The thermal conductivity is higher than that of TaO ₅ ), and the adhesion to the inner surface 15b of the tantalum sleeve is excellent.

4 shows an example of fabricating a cathode sleeve according to the present invention. Molybdenum silicide (MoSi ₂ ) is easily formed by contacting silicon (Si) powder on the surface of molybdenum (Mo) metal wire 16 and conducting and heating the metal wire 16. Can be formed. The reaction temperature of molybdenum and silicon is carried out for about 1 hour at about 500 ° C., about 30% of the melting point. As described above, the molybdenum silicide (MoSi ₂ ) 17 formed on the surface of the molybdenum metal wire as an oxygen diffusion preventing material is inserted into the opening of the cylindrical sleeve 15 in vacuum, and the metal wire is energized and heated to prevent the oxygen diffusion prevention layer ( 15c) is deposited on the inner surface 15b of the sleeve.

Then, a material composed of tungsten-alumina having a thickness of about 50:50 using the heat radiation coating material 18 is deposited on the upper surface on which the oxide diffusion preventing layer 15c is formed, and the metal wire is electrically heated to form an inner surface 15a of the blackening layer. .

5A and 5B show a comparison of particle diameters showing the results of the conventional practice and the present invention, respectively, in which the average particle diameter of the material of the sleeve inner surface 11b near the blackening inner surface 11a of the conventional 5a is about 10 μm, In the case of the present invention (FIG. 5B), the average particle diameter of the sleeve inner surface 15b material is reduced to about 2.5 mu m.

In addition, if the component analysis, the conventional sleeve inner surface (11b) material is detected a large amount of tantalum oxide (TaO ₅ ), but in the case of the present invention, the material of the sleeve inner surface (15b) is not detected tantalum oxide. As such, the sleeve material is prevented from being changed into a material having a low melting point, thereby preventing crystal coarsening due to crystal growth at a cathode temperature of about 1000 ° C.

In addition, such crystal coarsening prevents volume shrinkage and reduces heat shrinkage. The reduction in thermal contraction brings about stabilization in the gap between the cathode and the control electrode, thereby reducing the change in the bright spot voltage.

6 is a graph showing the change in the point of viscous voltage according to the life of the present invention, the conventional blackening / reduction heat treatment of the negative electrode sleeve has a heat shrink of about 8㎛ during a long time operation as a result of the heat shrink voltage This decreases by about 5-10%. Therefore, the current density residual ratio is further reduced by about 10 to 15%. However, as a result of the present invention, the breakdown voltage is reduced by about 5% and the current density is reduced by about 10% less than the conventional cathode.

In addition, when the point voltage is reduced, the voltage applied to the cathode is stabilized, so that the hot electron current density emitted from the cathode is maintained for a long time. As a result, a large-resolution, high-definition cathode with stable current density for a long time can be manufactured. Can be.

As described above, the present invention forms an oxygen diffusion barrier layer between the inner surface of the blackening layer and the inner surface of the sleeve, which constitute the thermal radiation coating material, on the cathode sleeve, thereby causing the blackening heat shrinkage in the tungsten-alumina composition forming the blackening layer (Al ₂ O ₃ ). Oxygen is reacted by diffusion movement into tantalum (Ta) to suppress the change of melting point to low tantalum oxide (Ta0 ₅ ) to prevent crystal coarsening. This suppression of crystal coarsening prevents volume shrinkage and reduces heat shrinkage. The reduction in thermal shrinkage brings about stabilization in the gap between the cathode and the control electrode, thereby reducing the change in the bright spot voltage.

From the above effects, a large-resolution, high-definition cathode having a large current density stable for a long time is obtained.

Claims (2)

In a cathode for a cathode ray tube having a tantalum (Ta) main component and a blackening layer inner surface of tungsten (W) and alumina (Al ₂ O ₃ ), a silicide layer is formed between the inner surface of the sleeve and the blackening layer. Cathode for cathode ray tube, characterized in that The method of claim 1, The silicide layer is a cathode for a cathode ray tube, characterized in that at least one or more of molybdenum silicide (MoSi ₂ ) or tantalum silicide (TaSi ₂ ) as a main component.