JPH10188845A - Electron gun for color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align the center of the elliptic hole of an inner electrode body with the inner wall center of a main lens electrode, ensure an accurate assembly work, eliminate the astigmatism or a main lens and improve a resolution by dividing a grid electrode as the constituent of the main lens into a plurality of cylindrical electrode bodies, and providing the inner electrode body at the jointed part of the cylindrical electrode bodies. SOLUTION: A G3 electrode 21 is formed out of two cylindrical electrode bodies 211 and 212, an inner electrode body 112 and a G3 lower electrode 213. The inner electrode body 112 is clamped with the jointed part C3 of the two cylindrical electrode bodies 211 and 212. On the other hand, a G4 electrode 22 is formed out of two cylindrical electrode bodies 221 and 222 as well as an inner electrode body 122. Also, the inner electrode body 122 is clamped with the jointed part C4 of the two cylindrical electrode bodies 221 and 222. The length 1 of the cylindrical electrode bodies 212 and 221 in this case is set at a value equal to a distance from the opposed edges 214 and 224 of both electrodes 21 and 22 to the inner electrode bodies 112 and 122. In this state, a mandrel for keeping three elliptical holes of the inner electrode body 112 aligned with the inner wall centers of the cylindrical electrode bodies 211 and 212 is used, and the inner electrode body 112 and the cylindrical electrode bodies 211 and 212 are welded to one another.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun for a color cathode ray tube, and more particularly to an in-line type electron gun, and more particularly to a structure of an electrode constituting a main lens of the electron gun.

[0002]

2. Description of the Related Art One of the factors affecting the focus characteristics of a color cathode ray tube, for example, a color picture tube, is a main lens aperture of a picture tube electron gun. In order to obtain good focus characteristics, it is desirable that the aperture of the main lens be as large as possible.

However, in an in-line electron gun, three electron guns corresponding to three colors of green, blue and red are arranged on the same horizontal plane and integrated, so that the electron gun is housed in a neck tube having a limited inner diameter. The possible values of the diameter of the cylinder and the distance between the main lenses constituting the main lens of each electron gun are greatly restricted, and it is extremely difficult to satisfy the demand for increasing the diameter of the main lens. Such a problem will be described with reference to the drawings. FIG. 6 is a plan sectional view of a color picture tube provided with an electron gun having a conventional structure. On an inner wall of the face plate portion 2 of the glass envelope 1, a fluorescent surface 3 on which phosphors of three colors are alternately applied in a stripe shape is supported. Cathodes 6, 7,
The central axes 15, 16, and 17 of 8 are a first grid electrode (hereinafter, referred to as a G ₁ electrode) 9, a second grid electrode (hereinafter, referred to as a G ₂ electrode) 10, and one of electrodes of a pair of electrodes constituting a main lens. 3 grid electrode (hereinafter referred to as G ₃ electrodes) 11 and a respective coincident with the center axis of each of the opening portions corresponding to the cathode of the shield cup 13, in a common plane, are substantially parallel to each other. The direction along this common plane is hereinafter referred to as the horizontal direction. Which is the other electrode constituting the main lens center axis of the central aperture of the fourth grid electrode (hereinafter referred to as G ₄ electrode) 12 is consistent with the central axis 16, the outer of the two openings The central axes 18 and 19 are slightly displaced outward without being coincident with the corresponding central axes 15 and 17, respectively. The three electron beams emitted from each of the cathodes 6 to 8 are:
The light enters the main lens along the central axes 15, 16 and 17.
G ₃ electrode 11 is set to a potential lower than _{G 4} electrode 12 of the high potential, _{G 4} electrode 12 of the high potential, a shield cup 1
3. A high voltage having the same potential as that of the conductive film 5 provided on the inner wall of the glass envelope 1 is applied. G ₃ , G ₄ electrodes 11, 1
Since the opening at the center of 2 is coaxial, the main lens formed in the center is axisymmetric, and the central beam travels straight along the axis after being focused by the main lens. On the other hand, since the apertures outside the electrodes 11 and 12 are off-axis from each other, a non-axisymmetric main lens is formed outside.
Therefore, the side beams are disposed outside, among the main lens region, a diverging lens region formed on the G ₄ electrode 12 side, passes through a portion deviated from the lens center axis to the central beam direction, the main lens At the same time as the convergence action by the center. In this way, the three electron beams form an image on the shadow mask 4 and are concentrated so as to overlap each other. The operation of concentrating each beam in this manner is called static convergence. Further, each electron beam undergoes color selection by the shadow mask 4, and only a component that excites and emits a phosphor of a color corresponding to each beam passes through the aperture of the shadow mask 4 and reaches the fluorescent surface 3. Further, an external magnetic deflection yoke 14 is provided for scanning an electron beam on the fluorescent screen.

[0004]

Factors that greatly affect the focus characteristics of a color picture tube as described above include the lens magnification and aberration of the main lens, which strongly depend on the intensity of the lens focusing action.

In general, in a picture tube, when the lens focusing function of the main lens is weakened, the lens magnification and spherical aberration are reduced, and the focusing performance is improved. One method of weakening this focusing action is to enlarge the openings of the G ₃ and G ₄ electrodes forming the main lens.

However, in the in-line type electron gun as shown in FIG. 6, the main lenses corresponding to the three colors of R, G, and B are arranged on the same horizontal plane. In the enclosure 1, the thickness must be equal to or less than 1/3 of the diameter of the neck accommodating the electron gun. Considering the thickness of the electrode, and considering the problems in processing the electrode, the limit value is further reduced. Becomes The present inventors have disclosed in JP-A-59-2
No. 15640 has proposed a method for effectively expanding the opening beyond the limit value. 7 and 8 show a front view of a G ₄ electrode 12 side from the partially broken perspective view showing the electrode structure of the main lens portion shown in the proposal and G ₃ electrode 11 side. The G ₃ electrode 11 and _{G 4} inner electrode member 112 and 122 constituting the opposing face of the electrode 12 to retract from each other. As a result, the potential of the counter electrode penetrates deeply into the inner electrode body, and has the same effect as an increase in the diameter of the opening. That is, the effective diameter of the main lens increases. This method of assembly is inserted, for example, the metal core to match the inner diameter center of the ellipse hole 123, 124 and _{G 4} electrode 12 of the inner electrode member 122 and the like, to secure a subsequent laser welding 200 to 203 and the like. In the figure, A
₁ , A ₂ , A ₃ , and A ₄ indicate central axes.

[0007] However components fabricated on, it is desirable to make equal the inner diameter D of the outer diameter d and G ₄ electrode 12 of the inner electrode member 122, in practice the outer diameter d of the inner electrode member 122 as shown in FIG. 9
The inner diameter D of _{G 4} electrode 12 may become larger relative,
In this case G ₄ electrode 12 as shown in FIG. 9 when fixed by laser welding or the like is locally deformed, the end face of the G ₄ electrode 12 1
2a is also deformed as shown in FIG. Incidentally, _{A 5} represents a central axis of the _{G 4} electrode 12. Of course the outer diameter d of the inner electrode member 122 is larger than the inner diameter D of the G ₄ electrode 12 is the inner electrode member 122 can not assemble without being inserted into G ₄ electrode 12.

[0008] _{G 3} main lens that same face and between the oval holes of the end surface 12a and the inner electrode member 122 of the _{G 4} electrode 12
It is formed between the end face of the electrode 11 and the inner electrode body 112. Now, G ₄ when the end face 12a of the electrode 12 is to the main lens is formed in a deformed state resulting electric field disturbance as shown in FIG. 9, so that the distorted main lens is formed. As a result, the beam that has passed through the main lens has astigmatism, resulting in degradation of resolution.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the resolution of a picture tube by eliminating astigmatism of a main lens portion by accurately assembling the center of an elliptical hole of an inner electrode body and the center of an electrode inner wall. An object of the present invention is to provide a tube electron gun.

[0010]

In order to achieve the above object, the present invention divides a grid electrode constituting a main lens into a plurality of cylindrical electrode bodies, and connects the plurality of cylindrical electrode bodies. By providing an inner electrode body at the joint, the center of the elliptical hole of the inner electrode body and the center of the inner wall of the main lens electrode are matched.

Since the grid electrode has a coupling structure of a plurality of cylindrical electrode bodies, and the inner electrode body is arranged at the coupling portion,
The positional dimensions of the inner electrode body become constant, and the deformation of the cylindrical electrode body and the inner electrode body when they are combined can be reduced, so that a main lens without distortion can be formed.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a partially cutaway sectional view showing an embodiment of the electron gun of the present invention.

[0013] In the figure, 21 is _{G 3} electrodes, 22 G
_{There are four} electrodes, and each of the electrodes 21 and 22 has the following configuration. That is, first _{G 3} electrode 21,
Two cylindrical electrode bodies 211 and 212 and inner electrode body 112
Furthermore it has become a combination of _{G 3} a lower electrode 213,
Sandwiching the inner electrode member 112 at the junction _{C 3} of the tubular electrode 211 and 212. On the other hand, _{G 4} electrode 22 sandwich the two cylindrical electrodes 221 and 222 and is made of a combination of the inner electrode member 122, the inner electrode member 122 at the junction _{C 4} of the tubular electrode 221 and 222 ing. 1 denotes the length of the cylindrical electrode bodies 212 and 221, and the length of the inner electrode body 1 is determined from the opposing end surfaces 214 and 224 of the electrodes 21 and 22.
The dimensions up to 12 and 122 are set to the same value. Reference numeral 23 denotes a bead glass, and the same symbols are given to the same portions as those in the above-described drawings.

FIG. 2 is a partially cutaway enlarged view showing an engagement structure between the cylindrical electrode body and the inner electrode body.
2, the cylindrical electrode bodies 211 and 212 are arranged,
The three members are joined at the welding points 20 of the cylindrical electrode body 212 shown in FIG.
Four tongue pieces 212a provided at portions corresponding to 0 to 203
Is extended to the other cylindrical electrode body 211 side beyond the inner electrode body 112, and a concave portion 211 provided in the cylindrical electrode body 211 is provided.
As shown in FIG. 2A, the two tubular electrode bodies 212 and 211 are welded and joined together with the inner electrode body 112 at the tongue piece 212a. The details of the structure of this welded joint are shown in FIG.
Shown in FIG. 3 is a sectional view taken along line III-III of FIG.

With such a structure, the inner electrode body 11
The three elliptical holes 2 and the inner walls of the cylindrical electrode bodies 211 and 212 are welded to each other by using a metal core having the same center. Therefore, if the outer diameter of the inner electrode body 112 is
Even when the inner diameter of the inner electrode 211 is smaller than the inner diameter of the inner electrode 112, the tongue 212a is deformed without deforming the inner diameter of the main body of the cylindrical electrode. The coincidence is assured, and the astigmatism of the main lens can be removed.

FIGS. 4 and 5 show another embodiment corresponding to FIG. 3 showing an engagement structure between the cylindrical electrode body and the inner electrode body. FIG. The inner diameter of the electrode body 212 is larger than that of the other electrode body. In this structure, it is not necessary to provide a recess in the other cylindrical electrode body 211. In FIG. 5, the tongue piece 112a is provided on the inner electrode body 112 side, and this structure does not require special processing for joining both the cylindrical electrode bodies 211 and 212.

In the above embodiment, both the G ₃ and G ₄ electrodes have 2 electrodes.
Although a combination of the cylindrical electrode body and the inner electrode body is used, the present invention is not limited to this. Further, although a combination structure of the cylindrical electrode body and the inner electrode body to G ₃ and G ₄ electrode both in the embodiment described above, it of course can be may be only one.

In the above-described embodiment, the electron gun having the structure having the grid electrodes up to the fourth grid has been described. However, it is needless to say that the present invention is not limited to this.

Further, in the present invention, the structure of the inner electrode body is not limited to that of the embodiment. For example, the electron beam passage hole is not limited to an ellipse but may be a perfect circle. Needless to say, the portion may be such that the notched electron beam passage hole becomes a semicircle.

[0020]

According to the present invention, there is an effect that astigmatism generated at random in the main lens portion is removed and the focus characteristic of the color cathode ray tube can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of an electron gun showing one embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a sectional view of a main part showing an example of an engagement structure between a tubular electrode body and an inner electrode body according to the present invention.

FIG. 4 is a cross-sectional view of a main part showing an example of an engagement structure between a tubular electrode body and an inner electrode body according to the present invention.

FIG. 5 is a cross-sectional view of a main part showing an example of an engagement structure between a tubular electrode body and an inner electrode body according to the present invention.

FIG. 6 is a plan sectional view schematically showing an in-line type color picture tube.

FIG. 7 is a partially broken perspective view showing an example of an electron gun main lens in which the effective aperture diameter of the conventional electron gun structure is enlarged.

FIG. 8 is a front view of FIG. 7;

FIG. 9 is a view of a portion corresponding to FIG. 8 for describing a modification of the electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Envelope 2 ... Face plate 3 ... Fluorescent surface 4 ... Shadow mask 6-8 ... Cathode 9-12, 21, 22 ... Grid electrode 112, 122 ... Inner electrode body 113, 114, 123, 124 ... Electron beam Passing elliptical holes 211, 212, 221 and 222: cylindrical electrode 211a: concave portion 212a: tongue piece.

Continued on the front page (72) Inventor Katsuyuki Shirai 3300 Hayano, Mobara-shi, Chiba Pref. In the Mobara Plant of Hitachi, Ltd. (72) Inventor Ikuya Takahara 3300-Hayano, Mobara-shi, Chiba Pref. Inventor Ryo Endo 3300 Hayano, Mobara-shi, Chiba Pref.Hitachi, Ltd.Mobara Plant

Claims (9)

[Claims] 1. An electron gun for a color cathode ray tube, comprising: three cathodes arranged in an in-line direction for emitting electron beams, respectively; and a plurality of grid electrodes including electrodes constituting a main lens for focusing the electron beams. At
The electrode constituting the main lens of the plurality of grid electrodes is configured such that a high-potential electrode to which a high voltage is applied and a low-potential electrode to which a voltage lower than the high voltage is applied face each other. At least one of the electrode and the low potential electrode
An inner electrode body provided with a hole through which the electron beam passes at the center, and two cylindrical electrode bodies sandwiching the inner electrode body are combined along the electron beam emission direction. One of them is provided with a long elliptical opening facing the high potential electrode or the low potential electrode and surrounding the three electron beams in common and extending in the in-line direction. An electron gun for a color cathode ray tube, wherein a center of a hole through which a beam passes and a center of a cylindrical electrode body facing the high potential electrode or the low potential electrode substantially coincide with each other. 2. An electron gun for a color cathode ray tube, comprising: three cathodes arranged in an in-line direction for emitting electron beams, respectively; and a plurality of grid electrodes including electrodes constituting a main lens for focusing the electron beams. At
The electrode constituting the main lens of the plurality of grid electrodes is configured such that a high-potential electrode to which a high voltage is applied and a low-potential electrode to which a voltage lower than the high voltage is applied face each other. Each of the electrode and the low-potential electrode is formed by combining a central inner electrode body provided with a hole through which the electron beam passes, and two cylindrical electrode bodies sandwiching the inner electrode body along the electron beam emission direction. Any one of these cylindrical electrode bodies is provided with an elliptical opening facing the low potential electrode or the high potential electrode and surrounding the three electron beams in common and long in the in-line direction, An electron gun for a color cathode ray tube, wherein a center of a hole through which an electron beam passes in the center of the inner electrode body and a center of a cylindrical electrode body facing the low potential electrode or the high potential electrode are substantially aligned. 3. The electron gun for a color cathode ray tube according to claim 1, wherein the central hole of the inner electrode body through which the electron beam passes has a smaller horizontal diameter than a vertical diameter. 4. A hole through which an electron beam at the center of the inner electrode body passes is elliptical.
An electron gun for a color cathode ray tube as described in the above. 5. The electron gun for a color cathode ray tube according to claim 1, wherein a hole in the center of the inner electrode body through which the electron beam passes has the same diameter in the horizontal direction and the diameter in the vertical direction. 6. The hole through which an electron beam at the center of the inner electrode body passes has a perfect circular shape.
An electron gun for a color cathode ray tube as described in the above. 7. An electron gun for a color cathode ray tube according to claim 4, wherein holes formed by said inner electrode body through which electron beams on both sides pass have a semicircular outer portion. 8. The electron gun for a color cathode ray tube according to claim 6, wherein the holes formed by the inner electrode body, through which the electron beams on both sides pass, have a semicircular outer portion. 9. An electron gun for a color cathode ray tube according to claim 1, wherein said inner electrode body is plate-shaped.