JPH0716285Y2 - Electron gun - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an electron gun for a cathode ray tube such as an image pickup tube.

SUMMARY OF THE INVENTION The present invention relates to an electron gun in which an insulating plate having an electron beam transmitting hole is interposed between first and second grids, and a second grid side portion of the electron beam transmitting hole of the insulating plate is provided. The hole has a larger diameter than the portion on the 1st grid side, and a portion that is shaded with respect to the 1st grid side is formed on the surface of the hole facing the second grid so as to reach the side wall of this hole. By doing so, the first
Also, the resistance value between the second grids is prevented from being lowered, that is, the deterioration of the insulating plate is prevented.

[Conventional technology]

2. Description of the Related Art Conventionally, there is known an electron gun having a structure in which a heat resistant insulating plate is interposed between the first and second grids so that stable electrode arrangement and the like can be performed.

FIG. 3 shows an example of such an electron gun. In the figure, K is a cathode, and the electron beam is transmitted to the center of the electrode plate portion (1) made of, for example, a cup-shaped metal electrode body and its closed end plate coaxially with the cathode K. A first grid G ₁ having holes h ₁ is arranged.

In addition, the first grid G ₁ is made up of, for example, first and second cup-shaped metal electrode bodies that are arranged coaxially with the first grid G ₁ so as to overlap with each other. An electron beam transmission hole h _2A is formed at the center of the electrode plate portion (2A) made of the closed end face plate, and the electrode plate portion (2B) made of the closed end face plate of the inner second cup-shaped metal electrode body is formed. A second grid G ₂ having an electron beam transmitting hole h _2B formed in the center is arranged.

Further, an electron beam transmission hole h ₃ is formed coaxially with the first grid G ₁ and the second grid G _2, and
The main surfaces (10a) and (10b) facing each other are flat surfaces having a high degree of parallelism, and the thickness thereof corresponds to the distance between the first grid G ₁ and the second grid G ₂ to be set. A heat-resistant insulating plate, for example, an insulating plate (10) made of ceramic is interposed. The electrode plate portion (1) of the first grid G ₁ and the electrode plate portion (2A) of the second grid G ₂ are brazed to the main surfaces (10a) and (10b) of the insulating plate (10), respectively. Are integrated.

An electron gun as shown in FIG. 3 is disclosed in, for example, Japanese Patent Laid-Open No. 58-1880.
This is described in detail in Japanese Patent Publication No. 37.

[Problems to be solved by the invention]

According to the electron gun shown in FIG. 3, a high-precision electron gun can be obtained, but in order to obtain a stable electron flow and a high electron emission density, the cathode K is, for example, disclosed in
When an impregnated cathode (impregnated cathode) as detailed in JP-A-58-87735 is used, its operating temperature is high, vaporization of barium (Ba) which is an emission material from the cathode K, and electrode material As a result of evaporation of certain nickel (Ni), as shown in FIG.
0) attached to the inner wall of the beam transmission hole h ₃ of the first grid G ₁
Also, there is a disadvantage that the resistance value between the second grid G ₂ is lowered, that is, the insulation property is deteriorated. When the insulation is deteriorated in this way, a leak current flows between the first grid G ₁ and the second grid G ₂ , and the second grid G _{2 and the} like cannot maintain a predetermined potential, which results in electron beam current characteristics. Could change.

In view of this aspect of the present invention, it is intended to prevent the resistance value between the first grid G ₁ and the second grid G _{2 from being} lowered, that is, the deterioration of the insulation property due to the attachment of evaporative substances and the like from the cathode.

[Means for solving problems]

The present invention is directed to electrode plate parts (1) and (2) having electron beam transmission holes h ₁ and h _2A of the first and second grids G ₁ and G ₂ , respectively.
An electron gun in which an insulating plate (10) having an electron beam transmitting hole h ₃ is interposed between A), the portion of the insulating plate (10) on the second grid G ₂ side of the electron beam transmitting hole h ₃ A hole h ₃₀ having a diameter larger than that of the portion on the first grid G ₁ side is provided, and the surface (6) of the hole h ₃₀ facing the second grid G _{2 is provided} on the side wall (7) of this portion h _30. As it reaches, a portion (5) that is shaded with respect to the electrode plate portion (1) side of the first grid G ₁ is formed.

[Action]

In the above configuration, the electron beam transmission hole of the insulating plate (10)
A shadowed portion (5) is formed in the inner wall of h _{3 on} the surface (6) of the large diameter hole h ₃₀ facing the second grid G ₂ so as to reach the side wall (7) of the hole h _30. since the evaporation, etc. from the cathode, of the inner wall of the electron beam transmitting hole h _3,
It is difficult to attach to this shaded part (5), therefore
It is possible to prevent the resistance value between the first grid G ₁ and the second grid G _{2 from} decreasing.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, the inner diameter of the electron beam transmission hole h ₃ of the insulating plate (10) is changed, and the inner wall has a portion (5) that is shaded from the electrode plate portion (1) side of the first grid G _1. Is formed.
That is, the larger the hole h ₃₀ of the diameter than the portion of the first grid G ₁ side is formed in the second grid G ₂ side portion of the electron beam transmitting hole h ₃ of the insulating plate (10), of the hole h ₃₀ Second grid G ₂
A portion (5) that is shaded with respect to the electrode plate portion (1) side of the first grid G ₁ is formed so as to reach the side wall (7) of the hole portion h _{30 on} the surface (6) facing to.

The insulating plate (10) having such a shape is formed, for example, by press-molding powder ceramics using two molds (20A) and (20B) as shown in FIG. 2 and firing. .

Others are the same as those in the example of FIG.

This example is configured as described above, and in the inner wall of the electron beam transmitting hole h ₃ of the insulating plate (10), the hole h is formed on the surface (6) facing the second grid G ₂ of the hole h _{30 having} a large diameter. _{Since the} shaded portion (5) is formed so as to reach the side wall (7) of ₃₀ , for example, when an imprecathode is used as the cathode K,
Evaporated substances and the like from the cathode K are unlikely to adhere to the shadowed portion (5) of the inner wall of the electron beam transmission hole h ₃ . Moreover, since the inner wall of the insulating plate (10) can be changed, the first grid G ₁
And the distance between the second grids G ₂ also becomes longer.

Therefore, according to this example, it is possible to prevent a decrease in the resistance value between the first grid G ₁ and the second grid G ₂ , that is, deterioration of the insulation property due to the attachment of evaporative substances from the cathode K to the electron beam transmission holes h ₃ . Can, 1st grid G ₁ and 2nd grid
No leak current flows between G ₂ .

The inner wall shape of the electron beam transmitting hole h ₃ of the insulating plate (10) in the above embodiment is an example, and various other shapes are conceivable. The point is that the electron beam transmitting hole h _{3 of the} insulating plate (10) is important.
Has a hole portion h ₃₀ having a larger diameter than the portion on the second grid G ₂ side of the first grid G ₁ side, and the surface (6) of this hole portion h ₃₀ facing the second grid G ₂ is It suffices if a portion that is shaded with respect to the electrode plate portion (1) side of the first grid G ₁ is formed so as to reach the side wall (7) of the hole h ₃₀ .

[Effect of device]

According to the present invention described above, a hole portion having a diameter larger than that of the first grid side portion is formed in the second grid side portion of the electron beam transmitting hole of the insulating plate interposed between the first and second grids. Then, since a portion of the hole facing the electrode plate portion side of the first grid is formed on the surface of the hole facing the second grid so as to reach the side wall of the hole, evaporation from the cathode It is possible to sufficiently prevent a decrease in resistance value between the first and second grids (deterioration of insulation) due to adhesion of the like.

When an oxide (metal oxide type) cathode is used as the cathode instead of the in-cathode, evaporative substances from the cathode adhere to the electron beam transmission holes of the insulating plate, but the amount is small. Is particularly effective when an imprecathode is used as the cathode.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining it, and FIG. 3 is a block diagram of a conventional example. (1) (2A) and (2B) are electrode plate parts, (5) is a shaded part, (6) is a part facing the second grid, (7) is a side wall, (10) is an insulating plate, h ₃ is an electron beam transmitting hole, h ₃₀ is a hole, G ₁ is a first grid, and G ₂ is a second grid.

Claims (1)

[Scope of utility model registration request] 1. An electron gun in which an insulating plate having electron beam transmitting holes is interposed between electrode plate portions having electron beam transmitting holes of each of the first and second grids. The second grid side portion has a hole portion having a larger diameter than the first grid side portion, and the surface of the hole portion facing the second grid reaches the side wall of the hole portion. An electron gun, characterized in that a portion that is shaded with respect to the electrode plate portion side of the grid is formed.