JP2002304957A - Electron gun and cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron gun and a cathode-ray tube intending to enhance drive characteristics and to improve emittance. SOLUTION: In this electron gun, a cathode 9, a G1 electrode 1 having an opening 10, and a G2 electrode having an opening 20 are provided, and they are disposed in this order. The cathode 9 has an emitter 3, a supportive structure 7, and a heater 8, the emitter is formed on the surface of the supportive structure 7, and the heater 8 is fixed in the supportive structure 7 to heat the emitter 3. The emitter 3 has a base part 5 and a protrusion 4, one main face of the base part 5 is brought into contact with the supportive structure 7, and the protrusion 4 is integrally formed on the other main face of the base part 5. The protrusion 4, the center of the opening 10 of the G1 electrode 1, and the center of the opening 20 of the G2 electrode are disposed on a center axis 50. The protrusion 4 of the emitter 3 has a shape recessed toward the G1 electrode 1 on the center axis 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron gun, and more particularly to an electron gun used for a cathode ray tube.

[0002]

2. Description of the Related Art FIG. 12 is a cross-sectional view schematically showing the structure of a triode in a conventional electron gun provided in a cathode ray tube. As shown in FIG. 12, the conventional triode includes an emitter 3 that emits electrons, a G1 electrode 1 having an opening 10, and a G2 electrode 2 having an opening 20, which are arranged in this order. Then, the emitter 3 and the opening 10 of the G1 electrode 1 are formed.
And the center of the opening 20 of the G2 electrode 2
0. The emitter 3 includes a heater (not shown), a support structure (not shown) for supporting the emitter 3, and the like, and is called a cathode.

The triode having the above-described structure mainly plays a role of extracting electrons into space in an electron gun. Specifically, the cathode, G1 electrode 1 and G2 electrode 2
Is applied with a predetermined voltage, and the emitter 3 is heated by a heater, whereby electrons are extracted from the surface of the emitter 3. The extracted electrons pass through the opening 10 of the G1 electrode 1 and the opening 20 of the G2 electrode 2 in this order while being focused by the electric field lens composed of the cathode, the G1 electrode 1 and the G2 electrode 2, and the central axis 50. Proceed in the direction.

[0004]

Generally, brightness of a cathode ray tube is adjusted by adjusting a current (cathode current) drawn from a cathode. The adjustment of the cathode current is based on a drive voltage (a voltage applied to the cathode and a voltage (0V) based on a voltage at which the cathode current starts to be emitted (also referred to as a "cutoff voltage"). Also referred to as a "cathode modulation voltage"). Controlled and performed. That is, when the drive voltage is increased, the brightness of the cathode ray tube increases.

[0005] In the conventional electron gun having the triode shown in FIG. 12, the drive voltage is 40 V in order to obtain a desired luminance.
Was needed. However, with the improvement in the resolution of the cathode ray tube, the fundamental frequency of the drive voltage is increasing to several hundred MHz corresponding to the frequency of the video signal, and an amplifier for generating the drive voltage is required to obtain a desired luminance. It has become difficult to output a voltage. As a method of solving this problem with the conventional structure, it has been considered to lower the voltage of the G2 electrode 2 and lower the cutoff voltage. When the cutoff voltage is reduced, a cathode current equivalent to that when the drive voltage is set to 40 V can be obtained even at a drive voltage lower than 40 V. However, when the cut-off voltage is reduced, the area for emitting electrons on the surface of the emitter 3 becomes large, and as a result, the emittance of the electron beam is reduced. For this reason, there is a problem that the spot diameter on the phosphor screen of the cathode ray tube becomes large and the resolution is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an electron gun and a cathode ray tube which improve drive characteristics and emittance.

[0007]

Means for Solving the Problems Claim 1 of the present invention
Wherein the electron gun includes a cathode, a first electrode having a first opening, and a second electrode having a second opening, and the centers of the first and second openings are the same. Disposed on an axis, the cathode has an emitter disposed on the central axis, the emitter has a side surface surrounding the central axis, and a normal at an arbitrary point on the side surface is defined as the central axis. A projection normal obtained by projecting on a cross section including the arbitrary point intersects the central axis outside the emitter, and the arbitrary point on the cross section is further away from the central axis,
The angle formed between the projection normal and the central axis is reduced.

According to another aspect of the present invention, there is provided an electron gun comprising: a cathode; a first electrode having a first opening;
A second electrode having a second opening, wherein the center of each of the first and second openings is disposed on the same central axis, and the cathode has an emitter disposed on the central axis. The emitter has a side surface surrounding the central axis, and in a cross section including an arbitrary point on the side surface and the central axis, the side surface has an arc, and an end portion of the arc most distant from the central axis. Is perpendicular to the central axis outside the emitter.

The electron gun according to a third aspect of the present invention is the electron gun according to the second aspect, wherein the emitter has a cross section including an arbitrary point on the side surface and the central axis. The emission of electrons is started from a point on the arc located at a predetermined distance from the end of the arc of the side surface to the center axis side.

[0010] In the electron gun according to the present invention, the emitter emits thermionic electrons.

A cathode ray tube according to a fifth aspect of the present invention includes the electron gun according to any one of the first to fourth aspects.

[0012]

FIG. 1 is a sectional view schematically showing a structure of a triode portion of an electron gun according to the present embodiment. As shown in FIG. 1, the triode according to the present embodiment includes a cathode 9, a G1 electrode 1 having an opening 10, and a G2 electrode 2 having an opening 20, and is arranged in this order. The cathode 9 has an emitter 3, a support structure 7, and a heater 8. The emitter 3 is formed on the surface of the support structure 7, and the inside of the support structure 7 is heated to heat the emitter 3. Is provided with a heater 8. Emitter 3
Has a substrate portion 5 and a projection portion 4, one main surface of the substrate portion 5 is in contact with the support structure 7, and the projection portion 4 is integrated on the other main surface of the substrate portion 5. Is molded. And
The protrusion 4, the center of the opening 10 of the G1 electrode 1, and G2
The center of the opening 20 of the electrode 2 is located on the center axis 50. The emitter 3 is an oxide obtained by oxidizing Ba, Ca, Sr or the like, and the cathode 9 having such an emitter 3 is called an “oxide cathode”. In this embodiment, the oxide cathode is used, but the emitter 3
B in the porous part in the sintered metal of tungsten
A dispenser cathode using one containing a may be used.

In this embodiment, the G1 electrodes 1 and G2
The thickness of the electrode 2 is, for example, 0.065 mm, 0.22 mm
The openings 10 and 20 of each electrode have a diameter of, for example, 0.1 mm.
These are circular openings of 4 mm and 0.54 mm. The distance between the substrate part 5 of the emitter 3 and the G1 electrode 1 is, for example, 0.1 mm.
The distance between the G1 electrode 1 and the G2 electrode 2 is, for example, 0.23 mm.

The triode according to the present embodiment having the above-described structure mainly serves to extract electrons from the cathode 9. Specifically, the emitter 3 heated by the heater 8 emits thermoelectrons from the surface of the projection 4. Here, when predetermined voltages applied to the cathode 9, the G1 electrode 1 and the G2 electrode 2 are voltages VK, VG1 and VG2, respectively, and when a predetermined voltage satisfying VG1 <VK <VG2 is applied to each electrode, the emitter 3 emits. Thermoelectrons are extracted into the space on the G1 electrode 1 and G2 electrode 2 side,
While being focused by an electric field lens composed of the cathode 9, the G1 electrode 1 and the G2 electrode 2, the apertures 10,
Through the opening 20 in this order, it proceeds in the direction of the central axis 50.

Next, the shape of the emitter 3 will be described in detail. 2A and 2B are schematic views showing the structure of the emitter 3. FIG. 2A is a plan view of the emitter 3 as viewed from the G1 electrode 1 side toward the central axis 50, and FIGS. )
FIGS. 3A and 3B are cross-sectional views taken along arrows AA and BB in FIG. The present invention is not limited to the projection 4 of the emitter 3.
In FIG. 2, the protrusion 4 is mainly shown in FIG.

As shown in FIG. 2, the projection 4 of the emitter 3
Has a shape recessed toward the G1 electrode 1 on the central axis 50. Specifically, as shown in FIGS. 2B and 2C, a semicircle 16 having a radius X2 is arranged so as to protrude from the substrate portion 5 toward the G1 electrode 1, and the semicircle 16 The center is separated from the center axis 50 by a distance X1. The projection 4 of the emitter 3 is a rotator obtained by rotating the semicircle 16 around a central axis 50. In the present embodiment, the values of the distance X1 and the radius X2 are, for example, 70 μm and 90 μm, and X1 <X2.

The emitter 3 has a side surface 14 that is a part of the surface of the projection 4 and surrounds the central axis 50.
As shown in FIGS. 2B and 2C, the side surface 14 of the emitter 3 has an arc 17 in a cross section including the central axis 50 of the emitter 3. The tangent at the end 15 of the arc 17 farthest from the center axis 50 is orthogonal to the center axis 50 outside the emitter 3. That is, the end 15 of the arc 17 is the most G in the projection 4 of the emitter 3.
This is a portion protruding toward one electrode 1.

The projection 4 of the emitter 3 has a semicircle 16
Is a rotating body obtained by rotating around the central axis 50, the shape of the protruding portion 4 at any point on the side surface 14 in the cross section including the point and the central axis 50 is 2
It becomes equal to the shape shown in (b) and (c).

An electron gun having the above structure is shown in FIG.
The drive characteristics are improved as compared with the conventional electron gun shown in FIG.
This has the effect of improving emittance. next,
Each effect will be described in detail.

FIGS. 3 to 6 are views for explaining the effect of improving the drive characteristics. FIG. 3 is a cross-sectional view showing an emission start portion of the electron gun according to the present embodiment. In FIG. 3, the high voltage side equipotential surfaces 10a and 10b are equipotential surfaces showing a value higher than the voltage applied to the cathode 9, and the high voltage side equipotential surface 10b is higher than the high voltage equipotential surface 10a. Potential is higher than Low voltage side equipotential surface 11
Reference numerals a and 11b denote equipotential surfaces indicating a value lower than the voltage applied to the cathode 9, and the low-voltage equipotential surface 11b has a lower potential than the low-voltage equipotential surface 11a. Further, the emission start point 30 indicates a place where the emission of the electron beam starts when the voltage applied to the cathode 9 (referred to as “cathode voltage”) is changed below the cutoff voltage.

As described above, the emitter 3 has a shape recessed toward the G1 electrode 1 at the center axis 50. Usually, the high voltage side equipotential surfaces 10a and 10b are
Since the bulges toward the emitter 3 with the center at 0, the point where the high voltage side equipotential surfaces 10a and 10b come closest to the emitter 3 is on the side surface 14 and the center axis 50 is smaller than the end 15.
It is a position close to. Since the side surface 14 is convex with respect to the high voltage side equipotential surfaces 10a and 10b, the portion where the high voltage side equipotential surfaces 10a and 10b come closest to the emitter 3 is on the side surface 14 and has a central axis. The position is closer to the end 15 than 50. Generally, to start emission from the position where the high-voltage side equipotential surface 10 comes closest,
As shown in FIG. 3, the emission start point 30 is at the end 1
5 and is located on the side surface 14 while being deviated from the central axis 50.

FIG. 4 is a diagram showing an emission start position of the electron gun according to the present embodiment. 4A is a plan view of the emitter 3 as viewed from the G1 electrode 1 side in the direction of the central axis 50, and FIG. 4B is a cross-sectional view taken along a line CC in FIG. 4A. . As shown in FIG.
4 surrounds the central axis 50, the emission start point 30 is located at the central axis 50 from the G1 electrode 1 side of the emitter 3.
In the plan view in the direction, it becomes a ring-shaped region surrounding the central axis 50.

When the cathode voltage is further reduced, the area on the emitter 3 where emission is performed (hereinafter, simply referred to as "emission area") is expanded. FIG. 5 is a diagram showing a state where the emission region is widened in the electron gun according to the present embodiment, and FIG. 6 is a diagram showing a state where the emission region is widened in the conventional electron gun. Emission area 4 in the figure
0 indicates an emission region when the cathode voltage is changed from the cutoff voltage by a predetermined voltage. The conventional electron gun shown in FIG. 6 differs only in the shape of the emitter 3, that is, only in whether or not the projection 4 is provided. This is almost the same as the electron gun (hereinafter, if there is a description of “conventional electron gun”, it is assumed that only the shape of the electron gun according to the present embodiment and the emitter 3 are different).

As shown in FIG. 5, since the emission start point 30 is displaced from the end portion 15 and the center axis 50, the emission region 40 is in a direction approaching the center axis 50 from the emission start point 30 and from the center axis 50. It spreads in both directions, away from (ie, toward the end 15). Then, as shown in FIG.
However, the distance y1 that spreads in a direction away from the center axis 50 from the emission start point 30 and the distance y2 that spreads in a direction approaching the center axis 50 are substantially the same distance.

On the other hand, in the conventional electron gun, as shown in FIG. 12, the surface of the emitter 3 is substantially flat and the central axis 5
0, and intersects substantially perpendicularly.
Since the shapes of 0a and 10b are swollen toward the emitter 3 around the center axis 50, the emission start point 30 in the conventional electron gun is on the center axis 50 as shown in FIG. When the cathode voltage is changed from the cut-off voltage by a predetermined voltage, the emission region 40 becomes the central axis 50.
It spreads in a substantially circular shape with the center as the center. Here, FIG.
As shown in FIG.
Assuming that the distance extending from 0 is the distance y3, the distance y3 is as shown in FIG.
The distance is substantially equal to the distances y1 and y2 in FIG. Therefore, the width of the emission region 40 generated when the cathode voltage is changed from the cutoff voltage by a predetermined voltage is wider in the electron gun according to the present embodiment than in the conventional electron gun. Therefore, the electron gun according to the present embodiment can extract more cathode current with the same amount of cathode voltage change than the conventional electron gun. In other words, the electron gun according to the present embodiment has improved drive characteristics as compared with the conventional electron gun.

FIGS. 7 to 9 are diagrams for explaining the effect of improving the emittance. FIG. 7 is a cross-sectional view schematically illustrating the structure of the emitter 3 in the electron gun according to the present embodiment, and is a cross-sectional view particularly illustrating the structure of the side surface 14 of the emitter 3 described above. In the drawing, a portion corresponding to the side surface 14 of the surface of the emitter 3 is indicated by a solid line, and other portions are indicated by broken lines. Although the structure of the side surface 14 of the emitter 3 has been described above with reference to FIG. 2, here, the structure of the side surface 14 of the emitter 3 will be described at an angle different from that described with reference to FIG. 2.

As shown in FIG.
, And points a, b, and c are defined as the distance from the central axis 50 increases. In a section including the points a, b, and c and the central axis 50, each normal line of the points a, b, and c corresponds to the emitter 3
And intersects with the central axis 50 outside. And point a,
The angles formed by the respective normals of b and c and the central axis 50 are respectively
Assuming the angles θ ₁ , θ ₂ , θ ₃ , the angles θ ₁ , θ ₂ , θ ₃ decrease in size in this order. That is, the emitter 3
Has a side surface 14 surrounding the central axis 50, and in a cross section including the normal line at an arbitrary point of the side surface 14 and the central axis 50, the more the arbitrary point is away from the central axis 50, the more the normal line of the arbitrary point and the And the angle formed by the angle is small. Note that the angles θ ₁ , θ ₂ , θ ₃ are angles of 90 ° or less.

In a section including an arbitrary point on the side surface 14 of the emitter 3 and the central axis 50, the emitter 3 can be positioned at any point on the side surface 14 even if the normal line of the arbitrary point does not intersect with the central axis 50. A structure in which a projection normal obtained by projecting a normal onto a section including the center axis 50 and an arbitrary point thereof intersects the center axis 50 outside the emitter 3 may be employed.
At this time, in a cross section including the arbitrary point of the side surface 14 and the central axis 50, the angle formed by the projection normal and the central axis 50 becomes smaller as the arbitrary point becomes farther from the central axis 50.

FIG. 8 is a diagram showing the trajectory of the electron beam in the conventional electron gun, and FIG. 9 is a diagram showing the trajectory of the electron beam in the electron gun according to the present embodiment. Figures 8 and 9
Electron beams EB1 and EB2 described above indicate electron beams extracted from the emitter 3 when the cathode voltage is changed from the cutoff voltage by a predetermined voltage, and the electron beam EB1 is extracted near the central axis 50 of the emitter 3. 3 shows an electron beam. The electron beam E
B2 indicates an electron beam extracted from a position farthest from the central axis 50 in the emission region of the emitter 3.

The electron beam E extracted from the emitter 3
B1 and EB2 are converged by an electric field lens composed of the cathode 9, the G1 electrode 1 and the G2 electrode 2 to form a crossover. Then, while diverging, it is incident on a main lens composed of a G3 electrode (not shown) and a G4 electrode (not shown). Each electron beam is slightly focused by a pre-focus lens composed of a G2 electrode 2 and a G3 electrode (not shown) before being incident on the main lens, and its divergence is suppressed. A virtual image of the crossover is generated on the opposite side of the surface of the emitter 3 from the G1 electrode 1. 8 and 9, the beam diameters in the virtual image of the crossover are shown as the maximum object point diameters Z1 and Z2. The maximum divergence angles α1 and α2 in the figure indicate the angles formed by the electron beam EB2 and the central axis 50 after the divergence is suppressed by the above-described prefocus lens.

In the conventional electron gun shown in FIG.
Is substantially flat and intersects substantially perpendicularly with the central axis 50. The shape of the high-voltage equipotential surface 10 is swollen toward the emitter 3 with the central axis 50 as the center. The focusing force received by the extracted electron beam increases as the distance from the central axis increases. Therefore, the point P1 at which the electron beam EB1 extracted from the vicinity of the central axis 50 of the emitter 3 intersects with the central axis 50 is located at a point P1 which is extracted from a position farther from the central axis 50 than the electron beam EB1.
The point of the emitter 3 is higher than the point P2 where B2 intersects the central axis 50.
It is a position away from the surface of.

In the electron gun of the present embodiment shown in FIG. 9, the side surface 14 which is a part of the surface of the emitter 3 has a cross section including a normal line and a central axis 50 at an arbitrary point.
The angle formed between the normal and the central axis 50 decreases as the arbitrary point moves away from the central axis 50. The electron beam EB2 has an initial trajectory on the surface of the emitter 3, particularly a cosine waveform about the normal drawn on the side surface 14, so that the electron beam EB2 has an initial trajectory more than the electron beam EB1. It faces the center axis 50 side. Therefore, the point P1 at which the electron beam EB1 intersects the center axis 50 is closer to the point P2 at which the electron beam EB2 intersects the center axis 50 than in the conventional electron gun. As a result, as shown in FIGS. 8 and 9, the maximum object point diameter Z2 of the electron gun of the present embodiment is smaller than the maximum object point diameter Z1 of the conventional electron gun. Note that the electron beam EB2 is emitted from the emitter 3
Since the position from the central axis 50 taken out from the surface is substantially the same in the electron gun of the present embodiment and the conventional electron gun, the maximum divergence angle α2 in the electron gun of the present embodiment is:
It is almost the same size as the maximum divergence angle α1 in the conventional electron gun.

In an electron gun used for a cathode ray tube or the like, it is desired that an electron beam extracted from an emitter be focused on a phosphor screen at one point. The emittance is used as an index indicating the characteristic. Since the precise definition of emittance is complicated, here, for convenience, if the product of the above-mentioned maximum object diameter and maximum divergence angle is defined as emittance, as described above, the maximum divergence angle is the same and the maximum object diameter is small. The signifies that the emittance is reduced.

FIG. 10 is a diagram showing the drive characteristics of the electron gun according to this embodiment, and FIG. 11 is a diagram showing the emittance characteristics of the electron gun according to this embodiment. FIG.
Each value in 11 is a simulation result, in which the characteristics of the electron gun of the present embodiment are indicated by broken lines, and the characteristics of the conventional electron gun are indicated by solid lines. As shown in FIG. 10, for example, the cathode current taken out by the electron gun of the present embodiment at a drive voltage of 80 V is about 3 mA,
The cathode current extracted in a conventional electron gun is about 1.5 mA. That is, the electron gun according to the present embodiment can extract about twice the cathode current as compared with the conventional electron gun. As shown in FIG. 11, the emittance of an electron beam taken out by the electron gun of the present embodiment at a cathode current of 3 mA is about 6000, for example.
μm · mrad, and the emittance of the electron beam extracted by the conventional electron gun is about 3200 μm · m.
rad. That is, the emittance of the electron gun according to the present embodiment is about 1/2 of the emittance of the conventional electron gun.
It has been improved by a factor of two.

As described above, the electron gun according to the present embodiment can extract a larger amount of cathode current than the conventional electron gun, so that the brightness of the cathode ray tube provided with the electron gun according to the present embodiment has a lower luminance. improves. Further, since the emittance of the electron gun according to the present embodiment is improved compared to the emittance of the conventional electron gun, the resolution of the cathode ray tube including the electron gun according to the present embodiment is improved.

As the electron gun provided in the cathode ray tube, as in the electron gun according to the present embodiment, thermal energy is supplied to the emitter by a heater, and electrons are extracted from the emitter. There is a field emission type in which electrons are emitted from an emitter by concentrating a positive electric field. The thermionic emission type electron gun tends to have a larger maximum object diameter of the extracted electron beam than the field electron emission type electron gun. For this reason, it is necessary that the thermionic emission type has a smaller maximum object diameter than the field emission type. Therefore, as in the present embodiment, the need can be met by applying the present invention to a thermionic emission type electron gun.

[0037]

According to the electron gun according to the first aspect of the present invention, the electric field lens formed by the electrodes and the cathode arranged on the central axis usually has its focusing power as the distance from the central axis increases. Becomes larger. As the projection normal to an arbitrary point on the side surface of the emitter becomes farther away from the central axis, the angle formed with the central axis becomes smaller, so that electrons emitted from the vicinity of the central axis on the side surface of the emitter move away from the central axis on the side surface of the emitter. The initial orbit is more toward the central axis than the electrons emitted from the place. Therefore, the distance between the point at which electrons emitted from the vicinity of the center axis of the side surface of the emitter intersects the center axis and the point at which electrons emitted from a location away from the center axis on the side surface of the emitter intersects the center axis is: Get closer. Therefore, the maximum object diameter is reduced, and the emittance of the electron beam is reduced.

Further, according to the electron gun according to the second and third aspects of the present invention, in a cross section including an arbitrary point on the side surface of the emitter and the central axis, the arc of the side surface of the emitter is the most centered. Since the tangent line at the end away from the axis is orthogonal to the central axis outside the emitter, the entire emitter is concave toward the first electrode. Therefore, the equipotential surface that shows a voltage higher than the cathode voltage formed by the cathode and each electrode is closest to the emitter on the side surface, not on the central axis. Therefore, the emission of the electron beam is started not on the central axis of the emitter but on the side surface. Further, since the side surface of the emitter is convex with respect to the central axis and surrounds the central axis, the emission of the electron beam starts from a region surrounding the central axis. Therefore, when the cathode voltage is changed, the emission region expands in a direction approaching the central axis from a region surrounding the central axis and in a direction away from the central axis. As a result, a larger amount of cathode current can be obtained with a smaller amount of change in cathode voltage than an electron gun whose emission region extends from one point on the central axis. That is, the drive characteristics of the electron gun are improved.

According to the electron gun of the present invention, since the emitter emits thermionic electrons, the electron gun of the present invention supplies thermal energy to the emitter to extract electrons from the emitter. It is an emission type electron gun. Thermionic emission type electron guns tend to have a larger maximum object diameter of the extracted electron beam than the field emission type. For this reason, it is necessary that the thermionic emission type has a smaller maximum object diameter than the field electron emission type. By applying the present invention to a thermionic emission type electron gun, the need can be met.

According to the cathode ray tube according to the fifth aspect of the present invention, by providing an electron gun with reduced emittance or improved drive characteristics, a cathode ray tube with improved resolution or improved brightness is provided. Tubes can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a structure of an electron gun according to an embodiment.

FIG. 2 is a schematic diagram showing a structure of an emitter 3 according to the present embodiment.

FIG. 3 is a diagram showing an emission start position of the electron gun according to the present embodiment.

FIG. 4 is a diagram showing an emission start point of the electron gun according to the present embodiment.

FIG. 5 is a diagram showing a state where an emission region is widened in the electron gun according to the present embodiment.

FIG. 6 is a diagram showing a state in which an emission region is widened in a conventional electron gun.

FIG. 7 is a cross-sectional view schematically showing a structure of an emitter 3 according to the present embodiment.

FIG. 8 is a diagram showing a trajectory of an electron beam in a conventional electron gun.

FIG. 9 is a diagram showing a trajectory of an electron beam in the electron gun according to the present embodiment.

FIG. 10 is a diagram showing drive characteristics of the electron gun according to the present embodiment.

FIG. 11 is a diagram showing emittance characteristics of the electron gun according to the present embodiment.

FIG. 12 is a sectional view schematically showing the structure of a conventional electron gun.

[Explanation of symbols]

1 G1 electrode, 2 G2 electrode, 3 emitters, 4 protrusions, 9 cathodes, 10,20 openings, 14 side surfaces, 1
5 ends, 17 arcs, 30 emission start points,
50 Central axis.

Claims (5)

[Claims] A first electrode having a first opening; and a second electrode having a second opening, wherein the centers of the first and second openings are on the same central axis. Wherein the cathode has an emitter arranged on the central axis, the emitter has a side surface surrounding the central axis, and a normal line at an arbitrary point on the side surface is defined by the central axis and the arbitrary A projection normal obtained by projecting a cross-section including a point intersects the central axis outside the emitter, and the more the arbitrary point is away from the central axis in the cross-section, the more the projection normal and the central axis An electron gun with a smaller angle. 2. A cathode, a first electrode having a first opening, and a second electrode having a second opening, wherein the centers of the first and second openings are on the same central axis. Wherein the cathode has an emitter disposed on the central axis, the emitter has a side surface surrounding the central axis, and in a cross-section including an arbitrary point on the side surface and the central axis, An electron gun wherein the side surface has an arc, and a tangent at an end of the arc farthest from the central axis is orthogonal to the central axis outside the emitter. 3. A point on the arc located at a predetermined distance from an end of the arc of the side surface to the center axis side in a cross section including an arbitrary point on the side surface and the center axis. The electron gun according to claim 2, wherein the electron gun starts emitting electrons. 4. The electron gun according to claim 1, wherein said emitter emits thermoelectrons. 5. A cathode ray tube comprising the electron gun according to claim 1. Description: