JPH07249366A - Electron gun with impregnated cathode - Google Patents

Abstract

(57) [Abstract] [Purpose] An electron gun equipped with an impregnated cathode that does not disturb the electric field of the electron lens system, does not significantly change the structure or state of the electron emission surface, and can maintain a stable electron emission state for a long period of time. provide. In an electron gun having at least an impregnated cathode and a plurality of grids 17 and 18, the impregnated cathode is provided with a recess 20 in a portion of the electron emitting surface facing the electron beam passage hole 21 of the first grid 17, This recess 20
Are formed so as to be rotationally symmetric with respect to an axis perpendicular to the electron emission surface, and the shape of the electron emission surface is similar to the shape of the electron beam passage hole 21 of the first grid 17. To be done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun provided with an impregnated cathode, and more particularly to an electron gun provided with an impregnated cathode having an electron emission surface with improved resistance to ion bombardment.

[0002]

2. Description of the Related Art Conventionally, in a cathode capable of emitting a high-density current, in many cases, the electron emission capability is in the state of a monoatomic layer to several atomic layers formed on the surface of the electron emitting surface of the cathode. It depends a lot. For example, the known impregnated cathode in which the electron emission surface of the cathode is coated with osmium (Os), or the electron emission surface of the cathode is osmium / ruthenium (Os / Ru), iridium (I)
In the known cathode coated with r), an electric dipole of barium (Ba) -oxygen (O) -metal M, for example, osmium (Os) is formed on the surface of the electron emission surface of the cathode, and this By the action of the dipole, the electron emission capability of the electron emission surface of the cathode is enhanced. In this case, the coverage of barium (Ba) is
The optimum value is 0.6 to 1.0. Also, semiconductor pn
Even in a cathode formed by using a junction or a cold cathode having a MIM (metal-insulator-metal) structure, in order to enhance the electron emission capability of the electron emission surface, such as barium (Ba) or cesium (Cs) is used. It is known to coat a layer of elements in the order of 0.6 atomic layer to mono atomic layer. And, of course, in the cathode having the above-mentioned configuration,
When the atomic layer formed on the surface of the electron emission surface is lost, the electron emission ability is significantly reduced.

Generally, the cathode is used in a vacuum envelope, but even if it is called a vacuum envelope, some residual gas exists in the vacuum envelope. When the residual gas molecules collide with the electron flow emitted from the cathode, positive ions and negative ions are released from the residual gas. Among the liberated ions,
Negative ions move toward the anode to which a positive voltage is applied, but part of the positive ions are accelerated by the influence of the accelerating electric field and the focusing electric field and move toward the cathode. At this time, when positive ions accelerated by a high acceleration electric field or a focusing electric field collide with the surface of the electron emission surface of the cathode at a high speed, the surface is sputtered by the positive ions,
The atomic layer formed on the surface of the electron emitting surface, that is, the atomic layer of the surface portion having a high electron emitting ability is lost. The atomic layer lost by such ion bombardment recovers the atomic layer on the surface to some extent in the thermionic emission type cathode, but in the case of the cold cathode type cathode, The recovery of the atomic layer on the surface is not desired, and the electron emission capability is directly reduced. If no measures are taken to reduce the electron emission capability of the electron emission surface of the cathode, the electron emission capability will eventually be lost, and the cathode function will be lost. Further, even in a state before the electron emission capability is lost, for example, in a color picture tube or the like, the focusing performance is deteriorated.

Here, FIG. 7 is a cross-sectional configuration diagram showing an outline of the configuration of the impregnated cathode and the first and second grid portions in a known electron gun.

In FIG. 7, 31 is a cathode pellet and 32 is
Is a cup, 33 is a sleeve, 34 is a heater, and 35 is a first
The grid 36 is a second grid.

The cathode pellet 31 is composed of a porous substrate made of a refractory metal such as tungsten (W) and barium (B) impregnated in the pores of the porous substrate.
It is composed of an electron emitting material containing a) and is inserted and held in a cup 32 made of a refractory metal such as molybdenum (Mo). A sleeve 33 also made of a high melting point metal
Has a cup 32 welded on top and a heater 34 contained therein. The first grid 35 functions as a limiting electrode and is arranged close to the electron emitting surface of the cathode pellet 31. The second grid 36 functions as an extraction electrode and is arranged on the opposite side of the first grid 35 from the cathode pellet 31.

Since the operation of the electron gun having such a configuration is already well known, the description of the operation of this electron gun will be omitted.

Next, FIG. 8 is a characteristic diagram showing the electric field intensity distribution, electron emission density distribution, and positive ion incidence density distribution on the electron emission surface of the impregnated cathode in the known electron gun shown in FIG.

In FIG. 8, the vertical axis indicates the normalized intensity of the electric field intensity distribution (curve), the electron emission density distribution (curve), and the positive ion incident density distribution (curve), and the horizontal axis indicates the electron emission surface of the impregnated cathode. Each position is shown.

As shown in FIG. 8, in the known electron gun, the distribution of the electric field strength applied to the electron emission surface of the impregnated cathode is such that the electron beam passing through the first grid 35 as shown by the curve. The portion facing the center of the hole is maximized, and becomes smaller abruptly with increasing distance from the portion facing the center. The distribution of the electron emission density, as shown by the curve, corresponds to the distribution of the electric field intensity, and the portion of the first grid 35 facing the center of the electron beam passage hole is maximized, and the distribution of the electron emission density is opposed to the center. It becomes a little sharper as it gets farther away from the part. Further, as shown by the curve, the distribution of the positive ion incident density is such that the energy of the positive ions is considerably large and almost no divergence occurs in the vicinity of the impregnated cathode, so that the distribution of the electric field strength and the electron emission density are The first grid 35 as well as the distribution
Of the electron beam passage hole is maximized, and it becomes considerably sharper as it goes away from the portion of the electron beam passage hole facing the center.

As described above, in the known electron gun, the maximum portions of the distribution of the electron emission density and the maximum distribution of the incidence density of the positive ions coincide with each other, and the distribution shapes thereof are substantially the same, so that the electron emission The probability that the atomic layer on the surface of the electron emission surface where the density is high is lost due to the collision of positive ions increases, and the electron emission amount of the impregnated cathode decreases due to the collision of positive ions.

In order to deal with such a situation, means for preventing the electron emission surface of the cathode from deteriorating the electron emission ability have already been proposed, and one example thereof is JP-A-62-62.
The means disclosed in No. 172636 can be mentioned.
The means disclosed in Japanese Patent Laid-Open No. 172636/1987 is configured such that the electron emission region of the cathode is annular, and
A plate is arranged at a portion where three electron flows emitted from each of the three cathodes cross over, and this plate prevents positive ions from colliding with the electron emission surface of the cathode.

[0013]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Although the means disclosed in Japanese Patent No. 2636 can prevent positive ions from colliding with the electron emission surface of the cathode, the plate is arranged at a portion where three electron flows cross each other. Therefore, not only is it necessary to prepare a plate having a special configuration, but also there is a problem that the electric field of the electron lens system is disturbed by the arrangement of the plate. Further, the means disclosed in JP-A-62-172636 makes the structure of the non-electron emitting region different from the structure of the cathode, or the surface condition of the non-electron emitting region when forming the annular electron emitting region. Since the structure that is different from the surface state of the electron emission region is adopted, it is necessary to use an additional separate mask, which causes a problem that the manufacturing cost becomes high, and the operating temperature of the cathode is high. In this case, there is also a problem that the electron emission region is expanded due to thermal diffusion.

The present invention eliminates the above-mentioned problems, and its purpose is not to disturb the electric field of the electron lens system, to largely change the structure or state of the electron emission surface, and to be stable for a long period of time. An object of the present invention is to provide an electron gun including an impregnated cathode capable of maintaining an electron emission state.

[0015]

To achieve the above object, the present invention provides an electron gun having at least an impregnated cathode and a plurality of grids, wherein the impregnated cathode comprises a first grid of an electron emission surface. A means for providing a concave portion at a portion facing the electron beam passage hole is provided.

[0016]

According to the above-mentioned means, since the impregnated cathode is provided with the concave portion in the portion of the electron emitting surface facing the electron beam passage hole of the first grid, the electric field applied to the electron emitting surface of the impregnated cathode is formed. The intensity of the surrounding area is larger than that of the area facing the center of the electron beam passage hole of the first grid, and the electron emission density also corresponds to the distribution of the electric field strength. The surrounding portion is larger than the portion facing the center of the passage hole. Further, the positive ion incident density is the same as the distribution of the positive ion incident density of the known impregnated cathode, and the portion facing the center of the electron beam passage hole of the first grid becomes the maximum, and the portion facing the center. It gets smaller rapidly as it gets away from.

As described above, according to the above-mentioned means, the contribution of electron emission is made to the maximum portion of the positive ion incident density on the electron emission surface, that is, the atomic layer on the electron emission surface which is largely damaged by the collision of positive ions. Since the area is relatively small, the probability that the atomic layer on the electron emission surface of the area where the electron emission density is high will be damaged by the collision of positive ions is much smaller than that of the known impregnated cathode, and the overall resistance is low. An electron gun having an impregnated cathode having improved ion bombardment can be obtained.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the outline of the construction of an embodiment of an electron tube loaded with an electron gun according to the present invention, and shows an example in the case of a color picture tube as the electron tube. .

In FIG. 1, 1 is a panel portion, 2 is a funnel portion, 3 is a neck portion, 4 is a fluorescent surface, 5 is a shadow mask, 6 is a magnetic shield, 7 is a deflection yoke, 8 is a purity adjusting magnet, and 9 is a magnet. Is a center beam static convergence adjustment magnet, 10 is a side beam static convergence adjustment magnet, 11 is an electron gun, and 12 is an electron beam.

The tubular body forming the color picture tube is
It comprises a panel section 1 arranged on the front side, a neck section 3 accommodating the electron gun 11, and a funnel section 2 arranged between the panel section 1 and the neck section 3. A fluorescent surface 4 is arranged and formed on the inner surface of the panel portion 1, and a shadow mask 5 is arranged so as to face the fluorescent surface 4. A magnetic shield 6 is provided inside the connecting portion of the panel portion 1 and the funnel portion 2.
Is provided, and the deflection yoke 7 is provided outside the connection portion of the funnel portion 2 and the neck portion 3. On the outside of the neck portion 3, a magnet 8 for adjusting the purity, a magnet 9 for adjusting the center beam static convergence, and a magnet 10 for adjusting the side beam static convergence.
Are arranged side by side, and the three electron beams 12 projected from the electron gun 11 are deflected in a predetermined direction by the deflection yoke 7, and then reach the picture element of the corresponding color on the fluorescent surface 4 through the shadow mask 5. Is configured to.

In this case, the image display operation in the color picture tube having the above-mentioned structure is exactly the same as the image display operation in the known color picture tube, and therefore the description of the image display operation in this color picture tube is omitted.

Next, FIG. 2 shows an impregnated cathode for emitting an electron beam in the electron gun 11 of the color picture tube shown in FIG. 1 and a first grid serving as an electrode for limiting the electron beam, and an electrode for extracting the electron beam. It is sectional drawing which expanded and showed the structure of the part of the working 2nd grid.

In FIG. 2, 13 is a cathode pellet and 14 is a cathode pellet.
Is a cup, 15 is a sleeve, 16 is a heater, and 17 is a first
A grid, 18 is a second grid, 19 is a metal film having a low work function, 20 is a recess, and 21 is an electron beam passage hole of the first grid 17.

The cathode pellet 13 is composed of a porous substrate made of a refractory metal such as tungsten (W) and barium (B) impregnated in the pores of the porous substrate.
a) -electron emitting material containing calcium (Ca) aluminate as a main component, and a refractory metal such as
It is inserted and held in the cup 14 made of molybdenum (Mo). The porous substrate has a metal film 19 having a low work function in the exposed portion, for example, osmium (Os) or scandium (Sc) -tungsten (W) -oxygen (O).
The composite film is vapor-deposited to form an electron emission surface, and the recess 20 is formed in a portion of the electron emission surface facing the electron beam passage hole 21 of the first grid 17. Sleeve 15
Is made of a refractory metal such as molybdenum (Mo). The cup 14 is welded to the upper part and the heater 16 is included inside. The first grid 17 serving as a limiting electrode is arranged close to the electron emission surface of the cathode pellet 13, and the second grid 18 serving as a lead electrode is arranged on the opposite side of the first grid 17 from the cathode pellet 13. Has been done.

Here, the cathode pellet 1 having the concave portion 20
To describe an example of the case of configuring No. 3, first, tungsten (W) powder is compacted by press shaping,
A solid body having a recess 20 is formed. Then, this solid is sintered in a reducing atmosphere or in a vacuum to form a porous sintered body (porous substrate). Next, the pores of this porous sintered body (porous substrate) are impregnated with an electron emitting substance containing barium (Ba) -calcium (Ca) aluminate as a main component, and the excess electron emitting substance is removed. The cathode pellet 13 is formed.

In this case, the outer edge shape of the recess 20 provided on the electron emission surface of the cathode pellet 13 as viewed from the first grid 17 side is rotationally symmetrical with respect to the axis perpendicular to the electron emission surface, and its cross section is 2 may have a V-shape or a U-shape as shown in FIG. 2, or may have a semicircular or semi-elliptical cross section. Furthermore, the outer edge shape of the electron emission surface of the recess 20 viewed from the first grid 17 side may be circular, elliptical, or polygonal.
The electron beam passage hole 21 may have a similar shape. The size of the outer edge area of the electron emission surface of the concave portion 20 is selected so as to correspond to the size of the opening area of the electron beam passage hole 21 or smaller than the size of the opening area. There is.

Since the normal operation of the electron gun having the above-mentioned structure is already well known, the description of the normal operation of the electron gun of this embodiment will be omitted.

FIG. 3 is a characteristic diagram showing the electric field intensity distribution, the electron emission density distribution, and the positive ion incidence density distribution on the electron emission surface of the impregnated cathode in the electron gun of this embodiment shown in FIG. .

In FIG. 3, the vertical axis represents the normalized intensity of the electric field intensity distribution (curve), the electron emission density distribution (curve), and the positive ion incident density distribution (curve), and the horizontal axis represents the electron emission surface of the impregnated cathode. Each position is shown.

As shown in FIG. 3, according to the electron gun of this embodiment, the distribution of the electric field strength applied to the electron emission surface of the impregnated cathode is, as shown by the curve, It becomes maximum at the portion facing the periphery of the electron beam passage hole 21, and the electron beam passage hole 21 of the first grid 17
It becomes smaller as it approaches the center of the electron beam passage hole 21 of the first grid 17, and has a minimum value at the part of the first grid 17 facing the center of the electron beam passage hole 21. Further, the distribution of the electron emission density becomes maximum at the portion of the first grid 17 facing the periphery of the electron beam passage hole 21, corresponding to the distribution of the electric field strength, as shown by the curve, and the first grid It becomes smaller as it approaches the center of the electron beam passage hole 21 of 17, and becomes a minimum value at the part of the first grid 17 facing the center of the electron beam passage hole 21. On the other hand, as shown by the curve, the distribution of the positive ion incident density becomes maximum at the portion of the first grid 17 facing the center of the electron beam passage hole 21, and sharply increases as it moves away from the portion of the first grid 17 facing the center. Get smaller.

As described above, the electron gun of this embodiment is constructed so that the distribution of the electron emission density (curve) on the electron emission surface of the impregnated cathode and the distribution of the positive ion incidence density (curve) are different. Therefore, specifically, the part showing the maximum value of the positive ion incident density on the electron emission surface of the impregnated cathode is made to substantially coincide with the part showing the minimum value of the electron emission density, and the damage due to the positive ions is relatively large. The contribution to the electron emission in the electron emission surface portion is considerably reduced, and the ion impact resistance of the impregnated cathode is substantially improved.

In the present embodiment, the recess 20 provided on the electron emission surface of the impregnated cathode is the portion of the electron emission surface facing the electron beam passage holes 21 of the first grid 17, that is, substantially the center of the electron emission surface. Although it is described as being provided in the portion, the location on the electron emission surface where the recess 20 is provided is appropriately selected according to the arrangement state of the impregnated cathode.

That is, in the case of a single type electron gun in which one impregnated cathode is arranged or in the case of a delta type electron gun in which three impregnated cathodes are arranged in a delta type, Similar to the present embodiment, the recess 20 of each impregnated cathode may be provided substantially at the center of the electron emission surface of each impregnated cathode, but three impregnated cathodes are arranged in line. In the case of an in-line type electron gun, among the recesses 20 provided on the electron emission surface of each impregnated cathode, the recess 20 of the impregnated cathode arranged at the center is provided at substantially the center of the electron emission surface. However, the recessed portions 20 of the impregnated cathodes arranged on both sides may be provided in a portion slightly deviated to the impregnated cathode side disposed substantially in the center from the substantially central portion of the electron emission surface.

FIG. 4 is a top view showing the location of the recesses 20 provided in the inline type electron gun, that is, the three impregnated cathodes arranged inline. The electron emission surface of the impregnated cathode of
As seen from the grid 17 side, FIG. 5 shows an electron gun (center gun) arranged at the center of the in-line type electron gun and an electron gun (side gun) arranged at one end,
For example, it is a cross-sectional configuration diagram showing the configuration of a main part of a blue (B) side gun, wherein (a) shows a green (G) center gun and (b) shows a blue (B) side gun. is there.

In FIGS. 4 and 5A and 5B, 1
3G is cathode pellet for green (G), 13B is blue (B)
Cathode pellet, 14G is green (G) cup, 14B
Is a blue (B) cup, 15G is a green (G) sleeve, 15B is a blue (B) sleeve, 16G is a green (G) heater, 16B is a blue (B) heater, 17G
Is a first grid for green (G), 17B is a first grid for blue (B), 18G is a second grid for green (G), 18
B is a second grid for blue (B), 19B is a metal film for green (G), 19B is a metal film for blue (B), 20R is a recess for red (R), 20G is a recess for green (G), 20B. Is a concave portion for blue (B), 21G is the first grid 1 for green (G)
Electron beam passage hole of 7G, 21B is electron beam passage hole of the first grid 17B for blue (B), 22R is red (R).
Is a green (G) impregnated cathode, and 22B is a blue (B) impregnated cathode.

Then, as shown in FIG. 4, red, green,
Among the impregnated cathodes 22R, 22G, and 22B of each color of blue, the impregnated cathode 22G for green (G) that constitutes the center gun is arranged at the center, and the impregnated cathode for red (R) that constitutes one side gun. Shaped cathode 22R is on the left side and the other side gun is a blue (B) impregnated type cathode 2
2B are arranged on the right side. The impregnated cathode 22G for green (G) has a recessed portion 20 at a substantially central portion of the electron emission surface.
G is provided, and the impregnated cathode 22R for red (R) is
A recess 20R is provided in a portion slightly deviated from the substantially central portion of the electron emission surface toward the impregnated cathode 22G for green (G),
The impregnated cathode 22B for blue (B) also has a recess 20B in a portion slightly deviated from the substantially central portion of the electron emission surface toward the green impregnated cathode 22G.

Further, as shown in FIGS. 5 (a) and 5 (b), the center gun and the two side guns have the same constructions as described above except for the locations of the recesses 20R, 20G and 20B. Since the structure is the same as that of the electron gun (gun) shown in FIG. 2, description of the structures of the center gun and the two side guns will be omitted.

Here, three impregnated cathodes 22R, 2
Recesses 20R provided on the electron emission surfaces of 2G and 22B,
An example of the shapes and dimensions of 20G and 20B will be described. Now, for each of the center gun and the two side guns, the diameter of the electron beam passage hole 21 of the first grid 17 is 0.45 mm, and the impregnation with the first grid 17 is performed. The distance from the cathode 22 is 0.1 mm, the thickness of the first grid 17 is 0.1 mm, the first grid 17 and the second grid 1 are
8 has a dimension of 0.2 mm, the concave portions 20R, 20G, and 20B have a U-shaped cross section (depth d) perpendicular to the electron emission surface and have a shape on the electron emission surface. When the outer edge shape viewed from the 1 grid 17 side is circular (diameter a), the diameter a is 0.1
About 5 mm is selected, and the depth d is selected so as to satisfy the relationship of d / a ≧ 1. Further, in the case of one having the above-mentioned dimensions, the impregnated cathode 2 in the two side guns
Recesses 20R provided on the electron emission surfaces of 2R and 22B,
The location of 20B is selected so that the deviation Δx from the central portion of these electron emission surfaces toward the impregnated cathode 22G in the center gun is about 0.12 mm.

In this case, the above-mentioned recesses 20R, 20G,
Although the shape and dimensions of 20B show a preferable example, the recess 20R provided in the electron gun of the present invention,
The configurations of 20G and 20B are not limited to those having the above-described shapes and sizes, and may have, for example, a V-shaped, semicircular, or semielliptical cross-sectional shape in the direction perpendicular to the electron emission surface. It may be present, and the first grid 17 on the electron emission surface
The outer edge shape viewed from the side may be a non-circular shape such as an elliptical shape or a polygonal shape that is line-symmetric with respect to the axis in the in-line direction, and the size thereof may be appropriately changed.
When the outer edge shape of the recess is non-circular, the diameter a in FIG. 5 may be the shortest. Of course, if the center gun and the two side guns are electron guns having various sizes different from those described above,
Recesses 20R, 2 according to various dimensions of one side gun
It goes without saying that the size of each part of 0G and 20B and the size of the deviation Δx of the arrangement location are also changed. The deviation Δx of the arrangement location mainly depends on the configuration and function of the main electron lens as described below. Therefore, when the configuration and function of the main electron lens are different, the magnitude of the deviation Δx is changed. However, when the diameter of the electron beam passage hole 21 of the first grid 17 or the applied voltage of the second grid 18 is different, it is not necessary to change the magnitude of the deviation Δx. possible.

Next, FIG. 6 shows a side gun of an in-line type electron gun, for example, an impregnated cathode 22 for red (R).
FIG. 9 is an operation explanatory view showing trajectories of electrons and positive ions in a side gun having R, showing the electron emitting surfaces of the red (R) impregnated cathode 22R and the blue (B) impregnated cathode 22B which form the side gun. Place the recess 20 in
Δx toward the center gun, not at the center of the electron emission surface
This is to explain the need to choose only the biased parts.

In FIG. 6, 23 is a third grid, and 24
Is a fourth grid, 25 is a fifth grid, 26 is an electron orbit, 27 is a positive ion orbit, and the others are shown in FIGS.
The same components as the components shown in FIG.

Then, the first grid 17 and the second grid 18 constitute a pre-electron lens, and the third grid 2
The third, fourth grid 24, and fifth grid 25 form a main electron lens.

As shown in FIG. 6, in the red (R) side gun, the red (R) impregnated cathode 22R is used.
The electrons emitted from the electron beam undergo a first deflection in the in-line outward direction (upper direction in FIG. 6) by the pre-electron lens, and then in the in-line inward direction (downward direction in FIG. 6) by the main electron lens. After being deflected by 2, the light travels along a trajectory 26 in which a shadow mask (not shown) converges with electrons of the other two colors, green (G) and blue (B). In this case, the velocity of the electrons is still small in the portion where the pre-electron lens is arranged, so that the first deflection is relatively large, and the velocity of the electron is large in the portion where the main electron lens is arranged. The deflection will be a relatively small deflection. On the other hand, for example, positive ions generated in the vicinity of the fifth grid 25 are first deflected in the in-line inward direction (downward direction in FIG. 6) by the main electron lens, and then are in-line outside by the pre-electron lens. Orbit 2 which receives a second deflection in the direction (upward direction in FIG. 6) and collides with the electron emission surface of the impregnated cathode 22R for red (R).
Proceed along 7. In this case, since the velocity of positive ions is still small in the arrangement portion of the main electron lens, the first deflection is relatively large deflection, and the velocity of positive ions is large in the arrangement portion of the pre-electron lens. , The second deflection can be a fairly small deflection or no deflection.

In this case, focusing on positive ions,
In the arrangement part of the main electron lens, the velocity is slow and therefore it is largely deflected, whereas in the arrangement part of the pre-electron lens, the velocity is fast and almost no deflection is made. When it collides with the electron emission surface of the red (R) impregnated cathode 22R through the arrangement portion of the electron lens, it mainly collides not with the central portion of the electron emission surface but with the portion deviated by Δx in the direction of the center gun. Like

Therefore, in the red (R) side gun, the recessed portion 20R is disposed on the electron emitting surface of the red (R) impregnated cathode 22R by Δx from the center of the electron emitting surface toward the center gun. If the biased portion is selected, as described above, the contribution of the relatively large portion of the damage of the atomic layer on the electron emission surface due to the collision of the positive ions to the electron emission can be considerably reduced, and the red (R) color can be substantially reduced. It is possible to realize the improvement of the ion impact resistance of the impregnated cathode 22R.

Further, as for the other side gun of the in-line type electron gun, for example, the blue (B) side gun having the impregnated cathode 22B for blue (B) is also the case of the above-mentioned red (R) side gun. If the location of the recess 20B on the electron emission surface of the blue (B) impregnated cathode 22B is selected to be a portion deviated from the center of the electron emission surface by Δx in the center gun direction,
Similarly, the contribution of the relatively large part of the damage of the atomic layer of the electron emission surface due to the collision of positive ions to the electron emission can be made considerably small, and the ion impingement of the impregnated cathode 22B for blue (B) can be substantially reduced. It is possible to measure the improvement of sex.

Regarding the concave portion of the electron emitting surface of the impregnated cathode which constitutes the side gun described above, an example is shown in which the arrangement location is selected to be a portion deviated in the direction of the center gun. When the outer edge shape of the electron emission surface viewed from the grid side is a non-circular shape that is long in the in-line direction, for example, a horizontally long slit shape, it may not be necessary to deviate the concave portion toward the center gun.

When the depth of the cross section of the recess in the direction perpendicular to the electron emission surface or the diameter of the outer edge of the recess as viewed from the first grid side on the electron emission surface is made larger in the center gun direction than in the inline outer direction. However, it may not be necessary to deviate the recess toward the center gun.

[0050]

As described above, according to the present invention,
Since the impregnated cathode has a recess in the portion of the electron emission surface facing the electron beam passage hole of the first grid, the electric field strength applied to the electron emission surface of the impregnated cathode is equal to that of the electron beam of the first grid. The surrounding area is larger than the area facing the center of the passage hole, and the electron emission density also corresponds to the area of the electron beam passage hole of the first grid in accordance with the distribution of the electric field strength. Compared to the distribution of the positive ion incident density of the known impregnated cathode, the positive ion incident density is
The portion of the first grid facing the center of the electron beam passage hole is maximized, and the distance is sharply reduced as the distance from the portion of the first grid facing the center is increased.

Therefore, the portion where the incident density of positive ions on the electron emission surface is the maximum, that is, the atomic layer on the electron emission surface which is largely damaged by the collision of positive ions corresponds to the portion where the contribution of electron emission is relatively small. Therefore, the probability that the atomic layer on the electron emission surface of the portion where the electron emission density is high is damaged by the collision of positive ions is considerably smaller than that of the known impregnated cathode. It has the effect of getting a gun.

Further, according to the present invention, since the internal structure of the pre-electron lens or the main electron lens is not changed,
Since the electric field of the electron lens system is not disturbed, and the structure or state of the electron emission surface is not largely changed, the electron emission surface can be manufactured inexpensively and easily for a long period of time. There is an effect that a stable electron emission state can be maintained throughout.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing the outline of the configuration of an embodiment of an electron tube loaded with an electron gun according to the present invention.

FIG. 2 is an enlarged cross-sectional configuration diagram showing a configuration of an impregnated cathode and first and second grid portions of an electron gun in the electron tube shown in FIG.

FIG. 3 is a characteristic diagram showing an electric field intensity distribution, an electron emission density distribution, and a positive ion incidence density distribution on an electron emission surface of an impregnated cathode in the electron gun of the present embodiment.

FIG. 4 is a top view showing the locations of recesses provided in three in-line type impregnated cathodes.

FIG. 5 is a cross-sectional configuration diagram showing the configuration of a main part of a center gun and a side gun arranged at one end of an in-line type electron gun.

FIG. 6 is an operation explanatory diagram showing trajectories of electrons and positive ions in a side gun of an in-line type electron gun.

FIG. 7: Impregnated cathode of known electron gun and first and second
It is a cross-sectional block diagram which shows the outline of a structure of the part of a grid.

FIG. 8 is a characteristic diagram showing an electric field intensity distribution, an electron emission density distribution, and a positive ion incidence density distribution on an electron emission surface of an impregnated cathode in a known electron gun.

[Explanation of symbols]

1 Panel Part 2 Funnel Part 3 Neck Part 4 Fluorescent Surface 5 Shadow Mask 6 Magnetic Shield 7 Deflection Yoke 8 Purity Adjusting Magnet 9 Center Beam Static Convergence Adjusting Magnet 10 Side Beam Static Convergence Adjusting Magnet 11 Electron Gun 12 Electron Beam 13 Cathode Pellet 13G Green (G) cathode pellet 13B Blue (B) cathode pellet 14 Cup 14G Green (G) cup 14B Blue (B) cup 15 Sleeve 15G Green (G) sleeve 15B Blue (B) sleeve 16 Heater 16G Green (G) heater 16B Blue (B) heater 17 First grid 17G Green (G) first grid 17B Blue (B) first grid 18 Second grid 18G Green (G) second grid 18B Second grid for blue (B) 19 Metal film with low work function 19G Metal film for green (G) 19B Metal film for blue (B) 20 Recess 20R Red (R) recess 20G Green (G) recess 20B Blue (B) recess 21 Electron beam passage hole of the first grid 17 21G Green (G) first grid 17G electron beam passage hole 21B Blue (B) first grid 17B electron beam passage hole 22R Red ( R) Impregnated cathode 22G Green (G) impregnated cathode 22B Blue (B) impregnated cathode 23 Third grid 24 Fourth grid 25 Fifth grid 26 Electron orbit 27 Orbit of positive ion

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Claims (6)

[Claims] 1. An electron gun having at least an impregnated cathode and a plurality of grids, wherein the impregnated cathode is provided with a recess in a portion of an electron emission surface facing the electron beam passage hole of the first grid. An electron gun having an impregnated cathode. 2. The electron gun with an impregnated cathode according to claim 1, wherein the recess is formed so as to be rotationally symmetrical with respect to an axis perpendicular to the electron emission surface. 3. The impregnation according to claim 1, wherein the recess is formed such that the shape of the electron emission surface is similar to the shape of the electron beam passage hole of the first grid. Electron gun with a cathode. 4. The impregnated cathode according to claim 1, wherein the recess has a non-circular outer edge shape on the electron emission surface when viewed from the first grid side. Electron gun with. 5. When the impregnated cathode is arranged in an in-line type, the recess of the impregnated cathode arranged in the center is provided in a substantially central portion of the electron emission surface, and the recesses of the impregnated cathode arranged on the left and right are An electron gun having an impregnated cathode according to any one of claims 1 to 4, wherein the electron gun is provided at a portion of each of the electron emitting surfaces, which is disposed in the center and is biased toward the impregnated cathode. 6. The impregnated cathode is characterized in that the porous substrate portion including the electron emission surface is formed together with the recess by pressing a porous sintered body made of a refractory metal. An electron gun having the impregnated cathode according to any one of claims 1 to 4.