JPH08102245A - Direct heated cathode structure - Google Patents

Abstract

PURPOSE: To provide a direct-heated cathode structure with stable support structure and capable of emitting rapid thermions by constituting its structure in which one pellet has at least three filaments at predetermined angles and intervals. CONSTITUTION: A direct-heated cathode structure comprises a porous pellet 100 impregnated with cathode material, and a heater means in contact with the pellet 100. The heater means involves at least three filaments 200, which are in direct contact at their one-side ends with the outer surface of the pellet 100 at predetermined intervals held between one and the next. The volume of the pellet 100 should fall within the range between 0.012 and 1.0 mm<3> . The filaments 200 are preferably provided in four from various points of view. The filaments 200 preferably measure 0.02 to 0.1 millimeters in diameter. The filaments 200 may be passed through the pellet 100 or welded to the sides of the pellet 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct heating type cathode structure, and more particularly to a direct heating type dispenser cathode structure for an electron gun for a color cathode ray tube.

[0002]

2. Description of the Related Art Cathodes emit thermoelectrons by thermal energy and are roughly classified into an indirectly heated type by an indirect heating method and a direct heating type by a direct heating method. The direct-heating cathode has a structure in which the filament and the thermionic emission source are in contact with each other.

Generally, the indirectly heated cathode is applied to an electron gun which requires a large amount of thermoelectrons, and is divided into, for example, an oxide cathode and a dispenser cathode, which have a built-in filament as a heat source. It comprises a sleeve and a base metal or storage tank fixed to the upper end of the sleeve. An oxide cathode material is mainly coated on the surface of the base metal, and a dispenser cathode is inserted in the storage tank.

In the case of the indirectly heated cathode, the heat generated from the filament is transferred to the base metal through the sleeve, so that it takes 8 to 12 seconds for the electron to be emitted from the cathode material applied to the base metal. It takes a long delay time to some extent.

On the other hand, the direct heating type cathode has a base metal or medium directly fixed to the filament and is often used in a small cathode ray tube for a viewfinder such as a video camera. In the direct heating type oxide cathode, the oxide cathode is applied to the base metal in the same manner as described above. The direct heating type dispenser cathode can also be applied to a cathode ray tube for a large size or a data display that requires a large current, and a storage tank is fixed to a filament, and this storage tank is made of a porous material impregnated with a cathode material. It has a structure in which pellets are received.

The latter direct heating type dispenser cathode has been filed by the present applicant as Korean Patent Application No. 91-9461. The structure is characterized in that, as shown in FIG. 1, the filaments 2 and 2'are in direct contact with both sides of the porous pellet 1 impregnated with the cathode material. More specifically, as shown in FIG. 2, the structure in which the filaments 2 are directly welded to both side surfaces of the pellet 1 as shown in FIG. 2, and as shown in FIG. It has a structure that penetrates the body.

Such a cathode has a merit that it takes a short time to release thermoelectrons after a voltage is applied and a current starts to flow, and high density electrons can be emitted. In order to shorten the time required for electron emission, it is necessary to reduce the heat capacity of the portion where electrons are emitted, that is, the pellet.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a direct heating type cathode structure which has a more stable support structure and is capable of quick thermionic emission.

[0009]

In order to achieve the above-mentioned object, the cathode structure according to the present invention is preferably a porous pellet impregnated with a cathode material, and a heating means for contacting the porous pellet. A direct heating cathode structure comprising a supporter supporting the heating means and an insulating block supporting the supporter, wherein the heating means is at least 3
A plurality of filaments, one end of each of the filaments being in direct contact with the outer surface of the porous pellet at a predetermined distance from each other, and the volume of the porous pellet is
It is characterized by being in the range of 0.012 mm ^{3 to} 1.0 mm ³ .

In such a cathode structure of the present invention,
The porous pellets may be formed in a circular cross-section,
Alternatively, it may be formed to have a polygonal cross-sectional shape. Filaments that come into contact with the porous pellets are provided at three or more locations around the body of the pellets at predetermined angular intervals.
A point support or higher support structure is formed. The filament may be formed so as to penetrate through the body of the pellet, or a plurality of filaments exposed to the outside of the body of the pellet may be integrally formed of one material inside the pellet. Further, in addition to the above structure, a plurality of pellets, particularly three pellets, may be provided for one insulating block, which allows application to a color cathode ray tube.

[0011]

By providing at least one porous pellet containing an electron-emitting substance and fixing three or more filaments on the side surface of each pellet, vibration and permanent deformation due to impact are suppressed, resulting in high reliability. It becomes possible to manufacture a cathode ray tube.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail based on embodiments with reference to the accompanying drawings.

FIG. 4 shows a first embodiment of the present invention. The porous pellet 100, which is an electron emission source, is obtained by compressing and molding a powder of a refractory metal such as tungsten and then sintering the powder, and is a hexahedron in which the cathode material is filled in the pores. . One end portion of each of the four filaments 200 is in contact with each side surface of the pellet 100, and the other end portions thereof extend long downward. When viewing the four filaments as one filament overall, the pellet 100 can be viewed as having four legs.

Each of the filaments 200 may be welded to the outer surface (side surface in the drawing) of the pellet 100 as shown in FIG. 5, or intersect each other as shown in FIG. 6 as another embodiment. Two filaments 200 may be provided so as to penetrate the body of the pellet 100. Therefore, it is also possible to obtain four filaments exposed to the outside of the pellet by the two filament materials that substantially penetrate the pellet 100. In the case of the through type as shown in FIG. 6, the two filaments 200 may be in contact with each other inside the pellet 100, or may be in contact with each other without contacting each other. When two filaments are in contact, the intersecting filaments can also be formed as an integrally connected structure having a plurality of filaments exposed to the outside of the body of the pellet 100, as shown in FIG. . At this time, the number of exposed filaments is at least three, and more filaments can be formed if necessary. However, considering various aspects, it is desirable to use four filaments 200. In the structure described above, when the filament is welded to the side surface of the pellet 100 as shown in FIG. 5, the filament 200 may serve as a heating element, but the pellet 100 is directly heated. Since it is a system, it rather plays a large role as a leg that supports pellets. That is, even if the filament is heated and its strength is deteriorated, at least three filaments 200 support the pellet 100 in a balanced manner.
The 00 support structure is stable. Therefore, the pellet 100 is not significantly affected by the impact from the outside, so that the shake of the screen and the change of the hue in the color cathode ray tube do not significantly appear.

On the other hand, the pellet 100 can be modified into various forms. That is, the pellet 100 may be formed to have a circular cross-sectional shape as shown in FIG. 8, or may be formed to have a polygonal cross-sectional shape as shown in FIGS. 9 and 10. Good.

In the case of a pellet 100 having eight sides as shown in FIG. 9, four filaments may be provided by providing one filament 200 on every two sides. Depending on the case, eight filaments can be provided by providing a filament on each surface.

FIG. 10 shows a pellet 10 having six sides.
Indicates 0. Here, although three filaments 200 are provided, in this case as well, six filaments extended from each surface may be provided.

11 and 12 show a more specific example of the direct heating type cathode structure of the present invention used for a monochromatic cathode ray tube.

The pellet 100 is a hexahedron, and a filament 200 is provided on each of four side surfaces. The filament 200 is directly attached to the fixed block 300.
It is welded to one supporter 400. At this time,
As shown in FIG. 2, each supporter 400 has two welding surfaces 4
01 and 402, and one filament 200 is welded to each welding surface. 11 and 1
As can be seen from 2, in this structure, two filaments are connected in parallel, a current is applied through the two filaments, and the current is drawn out through the remaining two filaments. With such a current application structure, the current in the filament is reduced, so the amount of heat generated by the filament is reduced and the amount of heat generated in the pellet is increased. In particular, when the filament is welded to the side surface of the pellet instead of penetrating the pellet, that is, when the pellet itself functions as a filament, the distribution voltage to the pellet increases due to the decrease in the linear resistance value of the filament. It is even more effective. Moreover, since the structure is such that heat is supplied to the pellets simultaneously from the four filaments, the pellets are heated very quickly, and thermionic emission can be performed immediately after the current is applied.

FIG. 13 shows a cathode structure of the present invention that can be used in a color cathode ray tube.

The cathode structure shown in FIG. 13 has a structure in which one insulating block has three unit structures shown in FIGS. 11 and 12, and each of the pellets has a structure for applying a current. It has 3 pairs of supporters.

In the cathode structure according to the present invention described above, there is a large difference in the initial electron emission time depending on the size (volume) of the emitter (pellet). If the emitter is too large, it takes a long time to heat the emitter, and the effect of shortening the electron emission time, which the present invention aims to improve, is reduced. On the other hand, if it is too small, not only is it difficult to handle when manufacturing the cathode structure, but it is also difficult to manufacture. That is, if it is smaller than the grid hole, it becomes difficult for the emitter to be accurately located at the center of the hole, and it may deviate from the grid hole, which causes poor reproducibility when actually applied. Also, if the emitter is too thin, cracks are likely to occur, making it difficult to emit electrons continuously.

Therefore, an appropriate size is required, but it is appropriate that the size is slightly larger than the grid hole generally used in the existing electron gun. That is, since the grid holes are 0.4 mm to 0.7 mm, it is appropriate that the diameter of the emitter (pellet) shown in FIG. 14 is 0.5 mm to 1.5 mm.

Since the structure in which two or more filaments penetrate the emitter, the thickness of the emitter is
At least 3 times the filament diameter is required. Therefore, the minimum emitter volume is the minimum emitter diameter (0.5m
m) and minimum emitter thickness (minimum filament diameter 0.02 m
It becomes the value calculated from m × 3).

From the aspect of reducing the electron emission time, as a result of the experiment by the present inventor, as shown in FIG. 15, when the emitter volume exceeds 1.0 mm ³ , no improvement effect appears, so that the emitter The volume must not exceed this.
Therefore, a suitable volume of the emitter is about 0.012 mm ^{3 to} 1.0 mm ³ .

Further, the cross-sectional area of the filament used as the heater, that is, the thickness has a great influence on the electron emission time. According to the experiments conducted by the present inventor, the electron emission time increases as the filament diameter decreases. This is because the contact area is small when the heat energy is conducted from the filament to the emitter, so that the conduction time becomes long.
As shown in FIG. 16, when the filament diameter is less than 0.02 mm, the electron emission time becomes long and the improvement effect of this structure is lost. On the contrary, when the diameter is increased, the electron emission time is shortened, but other problems appear. That is, a certain amount of electric power is required to reach the proper temperature, but since the electric power (P) = V ² / R, the applied voltage V also decreases as the resistance decreases. Then, the resistance R = ρ (l /
s) (ρ is the resistivity of the material, l is the length of the filament, s
Ρ is a fixed value in the filament cross-section), and l cannot be increased infinitely due to the cathode structure and must be limited to an appropriate length. It is determined by changing the area, ie the diameter of the filament.

Generally, the applied voltage has an error of ± 0.05 V or more with respect to the rated voltage, but if the rated voltage is too low, it may have a fatal influence on the operating characteristics of the cathode. . That is, when the rated voltage is 1V, 0.0
5V error is 5% error, but the rated voltage is 0.5V
In the case of, the error is 10%. Due to the characteristics of the cathode, the operating voltage must be applied within ± 10% of the rated voltage, but in order to do so, the rated voltage must be 0.5 V or higher. According to an experiment by the inventor, as shown in FIG. 17, the rated voltage is 0.5 at the operating temperature.
The filament diameter must not exceed 0.1 mm in order to exceed V. Therefore, the diameter of the filament is 0.02mm
It is desirable to have a value within the range of ~ 0.1mm.

[0028]

The cathode structure according to the present invention is characterized mainly in that at least three filaments are provided in one pellet at predetermined angles and intervals, and supports a pellet having a certain weight. The structure is very suitable for. That is, since at least three filaments support the pellet when the pellet is impacted, the pellet becomes strong against vibration and reduces the risk of deformation, and the vibration suppressing effect makes the first grid in the electron gun. The degree of change in relative position with respect to can be made extremely small. The suppression of the relative position change between the cathode structure and the first grid prevents screen shake and hue anomaly due to an impact and achieves stable stability of image quality, and in particular, a permanent anomaly due to long-term operation. Effectively suppress deformation. Such a cathode structure of the present invention can be adapted to be used not only in a general microminiature black-and-white cathode ray tube but also in a color cathode ray tube, particularly in a television or data display cathode ray tube having a large screen. Then, by setting the optimum size of the emitter and the optimum size of the filament, it is possible to provide a cathode structure with a faster electron emission.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a conventional direct heating type cathode structure.

2 is a cross-sectional view for explaining an example of the direct heating cathode structure shown in FIG.

FIG. 3 is a cross-sectional view illustrating an example of the direct heating cathode structure shown in FIG.

FIG. 4 is a partial perspective view of a direct heating type dispenser cathode structure according to the present invention.

5 is a cross-sectional view illustrating an example of the direct heating type dispenser cathode structure according to the present invention shown in FIG.

6 is a cross-sectional view illustrating an example of the direct heating type dispenser cathode structure according to the present invention shown in FIG.

7 is a cross-sectional view illustrating an example of the direct heating type dispenser cathode structure according to the present invention shown in FIG.

FIG. 8 is a plan view showing the form of pellets according to an embodiment of the present invention.

FIG. 9 is a plan view showing the form of pellets according to an embodiment of the present invention.

FIG. 10 is a plan view showing the form of pellets according to an embodiment of the present invention.

FIG. 11 is a side view of a cathode structure according to the invention assembled for a monochromatic cathode ray tube.

12 is a plan view of the cathode structure of the present invention shown in FIG.

FIG. 13 is a schematic perspective view of a cathode structure according to the present invention assembled for a color cathode ray tube.

FIG. 14 is a perspective view for illustrating the diameter, thickness, etc. of pellets in an example of the direct heating type dispenser cathode structure according to the present invention.

FIG. 15 is a graph showing a volume of an emitter with respect to an image output time in a direct heating type dispenser cathode structure according to the present invention.

FIG. 16 is a graph showing filament diameter with respect to image output time in a direct heating type dispenser cathode structure according to the present invention.

FIG. 17 is a graph showing a filament diameter with respect to a filament applied voltage in the direct heating type dispenser cathode structure according to the present invention.

[Explanation of symbols]

 1 Porous pellet 2 Filament 2'Filament 100 Porous pellet 200 Filament 300 Fixed block 400 Supporter 401 Welding surface 402 Welding surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Sinho, 503--20, Ansujugyu-dong, Suwon, Gyeonggi-do, Republic of Korea

Claims (10)

[Claims] 1. A direct heating cathode structure comprising a porous pellet impregnated with a cathode material and a heating means in contact with the pellet, the heating means comprising at least three filaments, One end of each of the filaments is in direct contact with the outer surface of the pellet at a predetermined distance from each other, and the volume of the pellet is in the range of 0.012 mm ^{3 to} 1.0 mm ^3. Thermal cathode structure. 2. The direct heating cathode structure according to claim 1, further comprising a supporter supporting the filament and an insulating block supporting the supporter. 3. The direct heating type cathode structure according to claim 1, wherein the diameter of the filament in contact with the pellet is in the range of 0.02 mm to 0.1 mm. 4. The direct heating type cathode structure according to claim 1, wherein the pellet has a circular cross-sectional shape. 5. The directly heated cathode structure according to claim 1, wherein the pellet has a polygonal cross-sectional shape. 6. The directly heated cathode structure according to claim 1, wherein the pellet is a hexahedron. 7. The directly heated cathode structure according to claim 6, wherein filaments are provided on four sides of the pellet. 8. The filament is provided so as to penetrate the pellet.
8. A directly heated cathode structure according to any one of 7 to 7. 9. The direct heating type cathode structure according to claim 8, wherein the filament has a structure integrally connected in the body of the pellet. 10. The direct heating cathode structure according to claim 1, wherein each of the filaments is welded to a side surface of the pellet at a predetermined angular interval.