JP2920934B2 - Electron gun - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube electron gun, particularly for air traffic control.
It is suitable for use in electron guns for high-definition color cathode ray tubes such as CRTs, CRTs for CAD / CAM, and CRTs for computer graphics.

[Summary of the Invention]

According to the present invention, in an electron gun of a cathode ray tube, an auxiliary electrode is arranged between a second electrode and a third electrode of a prefocus lens constituted by a first electrode, a second electrode, and a third electrode.
By configuring the electric field between the electrode and the auxiliary electrode to be stronger than the electric field between the auxiliary electrode and the third electrode, the prefocusing system has a concave lens function to optimally adjust the divergence angle of the electron beam with respect to the main electron lens. Thus, an electron beam having a small spot size is obtained.

[Conventional technology]

Generally, an electron gun for a color cathode ray tube, for example, a three-beam single electron gun, has three cathodes K [ _Kr , _Kg , _Kb ] corresponding to red, green and blue as shown in FIGS. Three first
The electrode G ₁ [G _1r , G _1g , G _1b ], the second electrode G ₂ , the third electrode G ₃ , the fourth electrode G _4, and the fifth electrode common to the three cathodes K
And a G _5, 4 sheets of the electrostatic deflection electrode plates to the subsequent stage (p _a)
The convergence means (c) consisting of (p _b ), (p _c ) and (p _d ) is arranged. (H ₁₎ [(h _1r) (h _1g)
(H _1b )] is an electron beam transmitting hole formed in the first electrode G _1r , G _1g , G _1b , respectively, and (h ₂ ) [(h _2r ) (h _2g ) (h _2b )] is a second electrode G ₂ , the electron beam transmission holes formed in (h ₃ ) [(h
_{3r) (h 3g) (h} 3b) ] is an electron beam transmission hole formed in the third electrode G _3. The cathode K is such an electron gun, the first electrode G _1, the second electrode G _2, pre-focus system by the third electrode G ₃ (i.e. pre-focus lens) is formed, the electron beam B [B from the cathode K in this region _r, B _g, the initial state of the B _b] (Monoten径, object point position, divergence angle, etc.) is determined, an electron beam B _r that have passed through the pre-focus system, B _g, B _b is applied anode voltage The light enters the main electron lens formed by the third electrode G ₃ and the fifth electrode G ₅ and the fourth electrode G ₄ to which the focus voltage is applied so as to intersect at the center of the lens, and then emits the fluorescent light by the convergence means (c). It is made to converge on the surface. The focus state of the main electron lens is determined by its aperture (that is, lens diameter), but if the main electron lens system is determined, the electron beam spot size differs depending on the state of the electron beam incident on the main electron lens.

Generally air traffic control CRT · CAD, CRT for CAM, high definition electron gun of the color cathode ray tube, such as a CRT or the like for computer graphics, the electron beam transmitting hole h ₁ and the first electrode G ₁ and the second electrode G ₂ reducing the diameter of h _2, to obtain a small electron beam spot-size by and longer electron gun electrodes G ₁ ~G ₄ of the smaller image magnification.

[Problems to be solved by the invention]

However乍Ra, in the conventional electron gun high-definition color cathode-ray tube, the diameter of the electron beam transmitting hole h ₁ and h ₂ of the first electrode G ₁ and the second electrode G ₂ is reduced, and the image magnification is small Even if the configuration is such that the spot size of the electron beam, for example, the electron beam current value 30 in a 32-inch cathode ray tube
At 0 μA, the limit is about 0.7 mm, and an electron beam having a small spot size smaller than 0.7 mm was not obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides an electron gun suitable for a high-definition color cathode ray tube, which enables a reduction in the spot size of an electron beam.

[Means for solving the problem]

The present invention provides an electron gun including a prefocus lens including a first electrode, a second electrode, and a third electrode, and a main electron lens connected to the prefocus lens.
An auxiliary electrode is disposed between the second electrode and the third electrode, and the electric field intensity between the second electrode and the auxiliary electrode is made stronger than the electric field intensity between the third electrode and the auxiliary electrode, so that the electron with respect to the main electron lens is changed. It is configured to control the optimum divergence angle of the beam.

[Action]

Generally speaking, regarding the spot size of the electron beam,
As the divergence angle of the electron beam incident on the main electron lens increases, the influence of spherical aberration on the main electron lens increases, and the spot size deteriorates.On the other hand, the spot size decreases, so the spot size decreases accordingly. Become smaller.
Therefore, there is an optimal electron beam divergence angle at which the spot size is minimized in both balances.

According to the electron gun of the above-described configuration, the second electrode G ₂ of the auxiliary electrode G _M between the third electrode G ₃ is arranged to configure the pre-focus lens, the electric field between the auxiliary electrode G _M and the second electrode G ₂ by the configured to be stronger than the electric field between the auxiliary electrode G _M and the third electrode G _3, would be added concave lens action in the pre-focus system, the divergence angle of the electron beam is increased in this concave action The direction can be adjusted to obtain an optimal divergence angle of the electron beam with respect to the main electron lens. Therefore, the spot size of the electron beam is improved to be smaller.

〔Example〕

Hereinafter, an embodiment of an electron gun according to the present invention will be described with reference to the drawings.

FIG. 1 shows a case where the present invention is applied to a unipotential three-beam single electron gun for a high-definition color cathode ray tube.

Is in the present example, as in the Figure 7 described above, the red, green and three cathodes K corresponding to blue [K _r, K _g, K _b] and three first electrodes G ₁ [G _1r, G _1g , G _1b ], the second electrode G ₂ , the third electrode G ₃ , the fourth electrode G _4, and the fifth electrode common to the three cathodes K.
And G _5, 4 sheets of the electrostatic deflection electrode plates _{(p a) (p b)} (p c) (p d)
Having convergence means (c) consisting of
Formed by further arranging the auxiliary electrode G _M between the second electrode G ₂ and the third electrode G _3. The first electrodes G _1r , G _1g , and G _1b have electron beam transmission holes h, respectively.
_1r, h _{1 g,} h _1b is formed, the second electrode G _2, and the third electrode G ₃ to the respective electron beam transmitting hole h _2r, h _2g, h _2b and h _3r, h _{3 g,} is h _3b is formed . Further electron beam to the auxiliary electrode G _M transmission hole h _Mr,
h _Mg and h _Mb are formed. Further, each of the first electrodes G _1r , G _1g , G _1b and the common second electrode G ₂ are integrated via an insulating spacer (for example, a ceramic spacer) (1) having both surfaces metallized.

High pressure and the third electrode G ₃ are the fifth electrode G _5, for example, the anode voltage of about 30kV is applied, the third electrode G ₃ voltage of about focus electrode for example 9kV~11kV is applied to the fourth electrode G ₄ ,
Main electron lens unipotential is constituted by the fourth electrode G ₄ and the fifth electrode G _5. Further, the first electrode G ₁ is applied for example 0V is, the second electrode G ₂ such as a low of about 500V~1kV is applied, the intermediate pressure of the same 9kV~11kV about the focus voltage to the auxiliary electrode G _M Is applied, the cathode K, the first
The electrode G ₁ , the second electrode G _2, and the third electrode G ₃ form a prefocus lens. And an auxiliary electrode G _M so that the distance l ₁ between the auxiliary electrode G _M and the second electrode G ₂ is smaller than the distance l ₂ between the auxiliary electrode G _M and the third electrode G ₃ are in this embodiment the second electrode side closer disposed in the electric field between the auxiliary electrode G _M and the second electrode G ₂ is configured to be stronger than the electric field between the auxiliary electrode G _M and the third electrode G ₃ (see FIG. 2).

The cathodes K _r, K _g, the electron beam B _r from K _{b, B g, B b} is incident to intersect at the center in the main electron lens through respective pre-focus lens, the subsequent convergence means (c) Converged on the phosphor screen.

According to the configuration described above, the second electrode G ₂ and the third high pressure low
Place the auxiliary electrode G _M of the intermediate pressure between the electrode G _3, i.e. the electric field between the second electrode G ₂ and the auxiliary electrode G _M is stronger than the electric field between the auxiliary electrode G _M and the third electrode G ₃ by placing the compensation electrode G _M in a position such that, a concave lens is formed on the pre-focus system as illustrated by the equipotential lines in Figure 2. Each electron beam B _r with respect to the main electron lens by the concave lens action, B _g, beam divergence angle of the B _b is adjustable in a direction to increase. In addition, since the concave lens is formed in a region where the electron beam is not accelerated, the diverging effect of the electron beam is large. Therefore, an optimum divergence angle of the electron beam can be obtained, and the spot size of the electron beam can be further reduced.

FIG. 4 is a graph comparing the electron beam spot sizes of the electron gun of the present invention and the conventional electron gun. Curve (I) in the case of the electron gun which is generally used high-definition color cathode ray tube, curve (II) is reduced diameter of the electron beam transmitting hole h ₁ and h ₂ of the first electrode G ₁ and the second electrode G ₂ for conventional electron gun for high-definition color cathode ray tube that, with the curve (III) is reduced diameter of the electron beam transmitting hole h ₁ and h ₂ of the first electrode G ₁ and the second electrode G _2, the image magnification In the case of the conventional electron gun for a high-definition color cathode ray tube which is reduced in size, the curve (IV) is the case of the electron gun according to the present invention. From the graph of FIG. 4, it can be seen that, in the electron gun of the present invention, the spot size was 0.6 at the current value of 300 μA of the high-definition color cathode ray tube.
3mm electron beam can be obtained, the conventional limit value of 0.7mm
The spot size can be further reduced.
The spot sizes of the curves (I), (II) and (III) at 300 μA are 0.95 mm, 0.75 mm and 0.7 mm, respectively.

Table 1 below shows a comparison of specific evaluations between the electron gun of the present invention (see FIG. 5) and the conventional electron gun (see FIG. 6). The present invention electron gun of FIG. 5 and conventional electron gun Figure 6 another except auxiliary electrode G _M has the same configuration, and d, D,
The dimensional relationship between t ₁ and t ₂ is the same.

The evaluation was performed using the following formula for finding the spot size of the electron beam: beam divergence angle θ, object diameter d _c , emittance E
(= D _C · θ · V ^1/2 ), object point position, etc.

SS = [(Md _C + 1 / 2MC _S θ ³ ) ² + d ² _rep ] ^1/2 ... (1) SS: Electron beam spot size M: Image magnification d _C : Object point diameter C _S : Main electron lens Spherical aberration θ: Divergence angle of the electron beam incident on the main electron lens d _rep : Increase in diameter due to mutual repulsion of electrons d _C · θ · V ^1/2 = constant = E (2) V: anode voltage From the equations (1) and (2), the optimum divergence angle θ _opt and the minimum spot size SS _min are given by the following equations.

As is clear from Table 1, the electron gun of the present invention can obtain the optimum divergence angle of the electron beam as compared with the conventional electron gun.
In addition, E is also small, and an electron beam with a smaller spot size can be obtained.

In the above example stronger than the electric field between the auxiliary electrode G assist electric field between the second electrode G ₂ and the auxiliary electrode G _M the position of _M as a distance l ₁ <l ₂ electrode G _M and the third electrode G ₃ But the auxiliary electrode
Position of G _M may be to obtain an electric field distribution to form a concave lens by controlling the potential of the auxiliary electrode G _M and optionally.

Although in the above example is the case of fixing the potential of the auxiliary electrode G _M, other auxiliary when the electrode G _M Not fix the potential spacing l ₁ and the auxiliary electrode between the second electrode G ₂ auxiliary electrode G _M by changing the electric field distribution around the auxiliary electrode G _M by distance l ₂ between G _M and the third electrode G ₃ to vary the potential of the auxiliary electrode G _M if Sadamare can change the strength of the lens.

As another example, the third and second electrode G ₂ as shown in FIG auxiliary electrode G reinforce the electric field between the _M electrode G _M and spacing l ₁ so as to be weaker than the electric field between the third electrode G _3> with a relationship l ₂ by placing an auxiliary electrode G _M can also be configured to be adjusted in a direction to reduce the divergence angle of the electron beam remembering convex lens action in the pre-focus system. This configuration is effective when the diameter of the main electron lens is small (that is, when the optimum divergence angle is small).

According to the present invention to above, gives an intermediate potential of the second electrode G ₂ potential and the potential of the third electrode G ₃ between the second electrode G ₂ and the third electrode G ₃ of the pre-focus system of the electron gun the auxiliary electrode G _M arranged, since to adjust the divergence angle θ of the electron beam using a lens function formed by the electric field distribution before and after the auxiliary electrode G _M, the optimum divergence angle is obtained, the electron beam Can be improved to a smaller spot size.

In the above example, the present invention was applied to a three-beam single electron gun.
Also applicable to beam electron guns.

In the above example, the present invention is applied to a unipotential type electron gun. However, the present invention can be applied to a bipotential type electron gun. In this case the second electrode G ₂ even the auxiliary electrode G _M between the third electrode G ₃ is disposed, the potential of the auxiliary electrode G _M is higher the potential of the second electrode G _2,
So as to provide a potential lower than the potential of the third electrode G _3.

〔The invention's effect〕

According to the electron gun of the present invention, the auxiliary electrode is arranged between the second electrode and the third electrode constituting the prefocus lens,
By making the electric field between the electrode and the auxiliary electrode stronger than the electric field between the auxiliary electrode and the third electrode so that the prefocus system has a concave lens action, an optimum divergence angle of the electron beam with respect to the main electron lens is obtained, The spot size of the electron beam can be made smaller than before.

Therefore, CRTs for air traffic control, CRTs for CAD / CAM,
The present invention can be suitably applied to an electron gun of a high-definition color cathode ray tube such as a graphic CRT.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an electron gun according to the present invention, and FIG.
FIG. 3 is an electric field distribution diagram of a prefocus system of the electron gun according to the present invention, FIG. 3 is an electric field distribution diagram of a prefocus system showing another example of the electron gun according to the present embodiment, and FIG. FIG. 5 is a graph showing a comparison between the beam spot sizes of the gun and the conventional electron gun, FIG. 5 is a cross-sectional view of a main part of the electron gun of the present invention used for evaluation measurement, and FIG. FIG. 7 is a sectional view of a main part of the gun, FIG. 7 is a configuration diagram showing an example of a conventional electron gun,
FIG. 8 is an enlarged view of the main part A. G ₁ is a first electrode, G ₂ is a second electrode, G _M is the auxiliary electrode, G ₃ is a third
Electrode, G ₄ and the fourth electrode, G ₅ denotes a fifth electrode.

Claims (1)

(57) [Claims] 1. An electron gun comprising: a prefocus lens including a first electrode, a second electrode, and a third electrode; and a main electron lens connected to the prefocus lens. An auxiliary electrode is disposed between the third electrodes, and the electric field strength between the second electrode and the auxiliary electrode is set to the third electric field.
An electron gun characterized in that the electric field strength between an electrode and the auxiliary electrode is made stronger to control an optimum divergence angle of an electron beam with respect to the main electron lens.