JPH0528932A - Electron gun for cathode-ray tube - Google Patents

Abstract

PURPOSE:To readily form an electron gun having a large aperture electron lens with high accuracy. CONSTITUTION:A plurality of electrodes forming both an electron-beam forming portion and a main electrode lens portion are integrally fixed by a pair of insulative support members 36 which are almost parallel and opposite to each other via support pieces. The main electron lens portion is formed by a first electrode comprising a large-diameter cylindrical portion 31 and a flat tube portion 32 having a maximum diameter portion being smaller in diameter than the cylindrical portion 31 and by a second electrode having a large-diameter cylindrical portion 33 surrounding the large-diameter cylindrical portion of the first electrode. The first electrode has a support piece 37 mounted on the long side face of the flat tube portion and in the second electrode support pieces 38 are formed in a pair of support plates 34 in such a manner as holding the support pieces of the first electrode from both sides. Each of the support plates is attached to the second electrode by at least three holddown pieces 35 comprising two holddown pieces each extending in the same direction as the support pieces and one holddown piece extending in the perpendicular direction to the two holddown pieces.

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 cathode ray tube, and more particularly to an electron gun for a cathode ray tube having a large diameter electron lens which can be assembled with high precision.

[0002]

2. Description of the Related Art Generally, a cathode ray tube is constructed as shown in FIG.
A phosphor screen 3 is formed on the inner surface of the face plate 2 of the envelope 1, and an electron beam 6 emitted from an electron gun 5 arranged in a neck 4 of the envelope 1 is attached to the outside of the envelope 1. Deflection is performed by the magnetic field generated by the deflection yoke 7 thus generated,
The phosphor screen 3 is horizontally and vertically scanned to form an image display structure. Particularly for a color picture tube, a shadow mask 8 having a large number of electron beam passage holes formed therein is mounted facing the phosphor screen 3, and the electron gun 5 serves as an electron gun for emitting three electron beams. The electron beam 6 emitted from the electron gun 5 is selected by the electron beam passage hole of the shadow mask 8 and the three-color phosphor layer forming the phosphor screen 3 is landed to form a structure for displaying an image. Has been formed.

Although there are various types of electron guns having various structures, in general, an electron composed of a cathode and a plurality of electrodes for controlling electron emission from the cathode and focusing the emitted electrons to form an electron beam. It has a beam forming unit and a main electron lens unit composed of a plurality of electrodes for focusing the electron beam emitted from the electron beam forming unit on the phosphor screen 3.

By the way, in order to improve the image drawn on the phosphor screen, it is necessary to reduce the beam spot of the electron beam on the phosphor screen. For that purpose, it is necessary to improve the lens performance of the electron lens, particularly the main electron lens portion. As a means for improving the lens performance of this main electron lens portion, it is known that it is better to make the lens aperture larger to make a large aperture electron lens.

As an electron gun having such a large-diameter electron lens, Japanese Patent Publication No. 57-18665 discloses a caliber of a cathode side electrode forming a main electron lens portion as shown in FIGS. 4 (a) and 4 (b). Is shown to be as close as possible to the inner diameter of the neck, and the electrode aperture on the phosphor screen side is made smaller than that. That is, FIG.
In the main electron lens portion shown in (a), a large-diameter cathode side electrode 10 and a small-diameter phosphor screen side electrode 11 are fixed via an insulating support member made of ceramic 12.
As for the main electron lens portion shown in FIG. 2B, the large-diameter cathode side electrode 10 and the small-diameter phosphor screen side electrode
11 and 11 are fixed by an insulating support member made of bead glass 13.

However, when the main electron lens unit is constructed as described above, the one in which both electrodes 10 and 11 are fixed through the ceramic 12 is as follows: (a) In the case of a color picture tube to which a high voltage is applied,
The withstand voltage becomes insufficient, causing dielectric breakdown.

(B) Ceramics, which are difficult to process, must be processed with high precision, which is economically problematic.

(C) Stoppers 14a and 14b must be used to fix the electrodes 10 and 11 to the ceramic 12, which makes assembly difficult.

(D) The stored gas from the ceramic 12 is released.

There are problems such as

Further, in the case of fixing both electrodes 10 and 11 with the bead glass 13, the bead glass is heated and melted from one side to be fused to the supporting piece of the electrode as in the usual electron gun assembly. It is difficult to assemble. There is no other suitable assembly method.

For such an electron gun, Japanese Patent Publication No. 58-
As disclosed in Japanese Patent No. 31696, as an electron gun that can be assembled, as shown in FIG. 5, an end portion of a second anode (fifth grid) 16 having a diameter as large as possible has a small diameter on the cathode K side and is provided in this small diameter portion. The supported support piece 17 is fused and supported on the insulating support member 18, while the first anode (fourth grid) 19 is divided into two, and the small diameter of the second anode 16 is provided on the cathode K side of the large diameter portion 20. Form a small diameter neck portion 21 that penetrates without contacting the part,
At the time of assembling the electron gun, the neck portion 21 is the cathode K side portion
The structure connected to 22 is shown.

However, with this structure, the decrease in accuracy and the difficulty of assembly due to the connection of the two-divided portions cannot be sufficiently solved.

As an improved structure of this electron gun, Japanese Patent Publication No. 2-
In Japanese Patent No. 16537, as shown in FIG. 6, a part of the cathode K side end portion of the second anode (fourth grid) 16 having the largest diameter is inserted into the inside to form the insertion portion 24. When assembling the gun, as shown in FIG. 7, the first anode (third grid) 19 is inserted by rotating it by an appropriate angle θ with respect to the second anode 16, so that the support piece 25 of the first anode 19 is inserted. And second anode 16
After avoiding contact with the indentation part 24, the angle θ is returned to the original position so that the support piece 25 of the first anode 19 and the support piece 17 of the second anode 16 are located on the same plane, and the insulating support member 18 is provided. The structure of fusing and fixing is shown. 8 (a) and (b)
Are the structures of the different insertion portions 24 of the second anode 16, respectively.

However, in any case, in the structure of this example, it is necessary to insert the first anode 19 and the second anode 16 by rotating the first anode 19 and the second anode 16 relative to each other by an angle of θ, and then return them to the original state after the insertion. However, the assembly is still complicated and mass productivity is lacking.
Especially in the structure as shown in FIG. 8A, the mechanical strength is weak,
There is a problem in practicality. Further, in the structure as shown in FIG. 8B, similarly to the electron gun shown in FIG. 5, the decrease in accuracy and the difficulty of assembly due to the connection of the two-divided portions cannot be sufficiently solved.

Further, such a large-diameter electrode (first anode
19) and another large diameter electrode surrounding this electrode (second
When forming a large-diameter electron lens with the anode 16),
Since both electrodes are quite long electrodes, these electrodes are
It is necessary to support and fix it very firmly. However, in the above electron gun, the support piece 25 of the first anode 19 and the second anode
Since the support pieces 17 of 16 are located on the same plane and apart from each other in the axial direction of the electron gun and are supported and fixed by the insulating support member 18, when the second anode 16 is strongly supported, Inevitably, the portion of the second anode 16 on the cathode K side becomes long. However, if the portion of the second anode 16 on the cathode K side becomes longer in this way, the supporting piece 25 of the first anode 19 must be moved to the cathode K side in terms of withstand voltage, and as a result,
The withstand voltage between the anode 19 and the adjacent second grid 26 becomes a problem, and the length of the first anode 19 from the support piece 25 on the phosphor screen side becomes long, so that strong support and fixation cannot be performed. Particularly, when the support and fixation of the first anode 19 is not strong, and therefore the phosphor screen side portion moves, not only the axis of the electron lens moves, but also the large diameter portion 27 of the first anode 19 on the phosphor screen side. The slight gap between the large diameter portion 28 of the second anode 16 is further narrowed, and not only the withstand voltage failure occurs, but also a fatal defect such as a short circuit between the first anode 19 and the second anode 16 is caused. I will wake up.

[0017]

As described above, in order to improve the electron lens performance of the electron gun, the main electron lens portion of the electron gun is a large-diameter electron lens, and this large-aperture electron lens has a large diameter. There is one formed by one electrode and another large-diameter second electrode surrounding the large-diameter portion of the first electrode. However, the conventional large-aperture electron lens has problems that it is difficult or complicated to assemble, and that it is difficult to assemble with high precision. Further, it is difficult to firmly support and fix both electrodes, and problems such as withstand voltage and short circuit due to contact between both electrodes occur.

The present invention has been made to solve the above-mentioned problems, and includes a large-diameter first electrode and another large-diameter second electrode surrounding the large-diameter portion of the first electrode. In an electron gun with a large aperture electron lens formed,
An object of the present invention is to construct a highly practical electron gun which is easy to assemble the electron gun and has a high mass productivity, and whose electrodes are firmly supported and fixed to enable highly accurate assembly.

[0019]

An electron beam forming unit comprising a cathode and a plurality of electrodes for controlling electron emission from the cathode and focusing the emitted electrons to form an electron beam, and the electron beam forming unit. And a main electron lens section composed of a plurality of electrodes for focusing the electron beam emitted from the phosphor screen onto the phosphor screen, and the cathode and the plurality of electrodes forming the electron beam forming section and the main electron lens section are In a cathode ray tube electron gun integrally fixed by a pair of insulating supporting members facing each other in parallel via supporting pieces provided on a plurality of electrodes, a main electron lens portion of the electron gun portion is a large diameter cylinder on the phosphor screen side. A first electrode integrally formed on the cathode side of the large-diameter cylindrical portion with a maximum diameter portion having a smaller diameter than the large-diameter cylindrical portion; A second electrode having a large-diameter cylindrical portion that surrounds the large-diameter cylindrical portion of one electrode, and the first electrode is provided with a support piece fixed to the insulating support member on the long side surface of the flat cylindrical portion; A pair of supports in which a large-diameter cylindrical portion of the electrode covers the maximum diameter portion of the flat cylindrical portion of the first electrode and is fixed to the insulating support member so as to sandwich the supporting piece of the first electrode from both sides. The plate is attached by at least three fixing pieces, and the three fixing pieces extend from both sides of each supporting plate in the same direction as the supporting pieces formed on each supporting plate, It is composed of one fixing piece extending from the central portion of the two fixing pieces in a direction orthogonal to the supporting piece.

[0020]

As described above, the first electrode is composed of the large-diameter cylindrical portion and the flat cylindrical portion whose maximum diameter portion is smaller than the large-diameter cylindrical portion, and the supporting piece is provided on the long side surface of the flat cylindrical portion. With the provision
The second electrode is attached with a pair of support plates formed so as to cover the maximum diameter portion of the flat tubular portion of the first electrode and sandwich the support pieces of the first electrode from both sides. The mounting is performed by at least two fixing pieces extending from both sides of each supporting board in the same direction as the supporting pieces formed on each supporting board.
When one fixing piece extending in the direction orthogonal to the supporting piece from the middle of the individual fixing pieces is used, a supporting piece for fixing these first and second electrodes to the insulating supporting member is provided for both electrodes. It can be provided near the large-diameter cylindrical portion, and the first and second electrodes can be firmly supported and fixed to the insulating support member. In addition, the supporting plate of the second electrode is formed by at least two fixing pieces in the same direction as the supporting piece and one fixing piece in the direction orthogonal to the supporting piece, so that the insulating supporting member is used as the supporting piece. It is possible to reduce the deformation of the support plate caused by the pressing force at the time of fusing and the distortion of the second electrode caused by the deformation of the support plate.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 shows an electron gun for a cathode ray tube which is an embodiment of the present invention. This electron gun has a cathode K, this cathode K
And a first to fourth good G1 sequentially arranged from the cathode K in the phosphor screen direction.
~ G4, fifth good G5 (first electrode) and sixth good G6
(Second electrode).

The first and second grids G1 and G2 are composed of plate electrodes having a relatively small plate thickness. The third grid G3 is composed of a cylindrical electrode formed by abutting two relatively shallow cup electrodes. The fourth good G4 is composed of a plate electrode having a relatively large plate thickness. The fifth grid G5 is composed of one plate-shaped electrode 30 having a relatively large plate thickness and four sets of cylindrical electrodes formed by butting two cup electrodes. The fifth grid G5 is provided on the phosphor screen side of the fifth grid G5. The electrode is a large-diameter cylindrical portion 31 and a cathode K of this cylindrical portion 31.
It is composed of a horizontally elongated flat tubular portion 32 having a smaller maximum diameter than the large-diameter cylindrical portion 31 mounted on the side. Also the 6th
The grid G6 includes a large-diameter cylindrical portion 33 that surrounds the large-diameter cylindrical portion 31 of the fifth grid G5, and the maximum diameter of the flat cylindrical portion 32 of the fifth grid G5 is on the cathode K side of the cylindrical portion 33. A pair of support plates 34 that cover the parts are attached.

Particularly in the electron gun of this example, the support plate 34 is
Is formed by bending at least three fixing pieces 35 at the end edge of each supporting plate 34 on the side of the cylindrical portion 33.
It is attached by welding 35 to the bottom attachment portion of the cylindrical portion 33. 2 out of the at least 3 fixing pieces 35
One is from both sides of the support plate 34 in the same direction as the following support pieces provided on the support plate 34, and one is from the central portion of the support plate 34 (the middle of the two fixing pieces 35) to the above support piece. It extends in the direction of.

The cathode K, the heater, and the first to sixth good parts G1 to G6 are supported and fixed by a pair of insulating support members 36 facing each other substantially in parallel via support pieces. Regarding the support and fixation by the pair of insulating support members 36, in particular, in the electron gun of this example, the electrode on the phosphor screen side of the fifth grid G5 has a support piece at the center of the long side surface of the horizontally long flat cylindrical portion 32. Install 37, while the sixth
For the grid G6, the flat tubular portion of the fifth grid G5
The pair of support plates 34 covering the maximum diameter portion of 32 are arranged so that the support pieces 37 at the central portions of the long side surfaces of the flat tubular portion 32 are horizontally sandwiched from both sides at the side edge portions of the electron gun with respect to the support pieces 37. The support piece 38 is bent and formed with a slight shift in the axial direction.

To apply a voltage to each electrode of this electron gun, the cathode K is set to 0 to 200 V, a video signal is added to this, the first grid G1 is set to the ground potential, and the second grid G2 is applied.
500V-1kV, 3rd grid G3 5-10kV, 4th grid
A high voltage of 0 to 1 kV is applied to G4, a high voltage of 5 to 10 kV is applied to the fifth grid G5, and a high voltage of 20 to 40 kV is applied to the sixth grid G6.

By applying the above-mentioned voltage, the electron emission from the cathode K is controlled by the cathode K and the first to third grids G1 to G3, and the emitted electrons are focused to form an electron beam. Parts are formed. The electrodes 30 on the fourth grid G4 side of the third and fourth grids G3 and G4 and the fifth grid G5 form a unipotential electron lens that weakly focuses the electron beam emitted from the electron beam forming unit. Further, the large-diameter cylindrical portion 31 on the phosphor screen side of the fifth grid G5 and this cylindrical portion
The large diameter cylindrical portion 33 of the sixth grid G6 surrounding 31 forms a large diameter electron lens that strongly focuses the electron beam focused by the unipotential electron lens. As a result, the beam spot on the phosphor screen can be made extremely small due to the focusing of the large-diameter electron lens.

By the way, assembling of the electron gun is as shown in FIG.
From the open side of the tip of the large-diameter cylindrical portion 33 of the sixth grid G6 shown in (a), insert the fifth grid G5 shown in (b),
The combination of the fifth and sixth grids G5 and G6 is used as a support piece for the heater and the cathode K and the first to fourth grids G1.
~ G4 and the cathode K side portion consisting of one plate electrode 30 of the fifth grid G5 and four sets of tubular electrodes, and after positioning and arranging in a predetermined relationship on the electron gun assembly jig, the heater and cathode The supporting piece of K and the supporting piece of each grid are pressed against the pair of insulating supporting members 36 which are heated and melted,
It is assembled by fusing so as to face each other substantially in parallel.

Therefore, as described above, the fifth grid G5
Is composed of a large-diameter cylindrical portion 31 and a horizontally long flat cylindrical portion 32 whose maximum diameter is smaller than that of the large-diameter cylindrical portion 31.
A supporting piece 37 is provided at the center of the long side of the
A pair of support plates 34 are provided on the cathode K side of the large diameter cylindrical portion 33 of G6 so as to cover the maximum diameter portion of the flat cylindrical portion 32 of the fifth grid G5.
Two fixing pieces 35 extending in the same direction as the supporting pieces 38 provided on the supporting plate 34 and the supporting piece 38 from the central portion of the two fixing pieces 35.
Attached by at least three fixing pieces 35 composed of one fixing piece 35 extending in a direction orthogonal to the supporting pieces 38 provided on the pair of supporting plates 34, the flat tubular portion of the fifth grid G5. If the support pieces 37 of 32 are provided so as to be sandwiched from both sides, the electron gun having a special structure having the two large-diameter cylindrical portions 31 and 33 can be easily assembled like an ordinary electron gun.

Moreover, if the fifth and sixth grids G5 and G6 are configured as described above, this type of electron gun, which has been difficult to assemble with high precision in the related art, can be assembled with high precision.
That is, the sixth grid G6, together with the heater and the support piece for the cathode K, and other grids are positioned and arranged in a predetermined relationship on the electron gun assembly jig, and the insulating support member 36 heated and melted is pressed against the sixth grid G6. The pair of support plates 34 of the grid G6 are crushed in the Y direction shown in FIG. 1B by the pressing force when pressing the insulating support member 36, and a deforming force that spreads in the X direction orthogonal to the Y direction is applied. Receive, but each support plate 34
Is composed of two fixing pieces 35 extending in the same direction as the supporting pieces 38 and at least one fixing piece 35 extending from the central portion of the two fixing pieces 35 in a direction orthogonal to the supporting pieces 38. Since it is attached to the large diameter cylindrical portion 33 by the three fixing pieces 35,
When the insulating support member 36 is pressed, it is possible to sufficiently resist the deformation force that is crushed in the Y direction and spread in the X direction, and each support plate 34
Therefore, the distortion of the large-diameter cylindrical portion 33 can be reduced.

Further, in general, in order to firmly support and fix an electrode having a large-diameter cylindrical portion, it is preferable to bring a support piece for fixing the electrode to the insulating support member as close to the large-diameter cylindrical portion as possible. Conventionally, there is a supporting means disclosed in Japanese Patent Publication No. 57-18665 shown in FIG. 4B, but this supporting means is not practical because it is difficult to fuse the supporting piece to the insulating supporting member. Further, the ceramic method shown in FIG. 4A is not practical in terms of cost and accuracy. Further, in the supporting means of Japanese Patent Publication No. 2-16537 shown in FIG. 6, since the second anode is provided with the supporting piece near the large diameter portion, it is firmly supported and fixed. Two
The first anode, which is the inside of the anode, cannot be firmly supported and fixed because the support piece is far away from the large diameter portion. In order to firmly support and fix the first anode,
Although it is sufficient to make the supporting piece large, it is difficult to make it a practical electron gun because there is a limitation in terms of withstand voltage characteristics and electron gun design.

On the other hand, in the electron gun of this example, since the fifth and sixth grids G5 and G6 are provided with the support pieces 37 and 38 near the large diameter cylindrical portions 31 and 33, both grids are provided. G5, G6
Can be firmly supported and fixed. That is, with respect to the support piece 37 provided on the flat tubular portion 32 of the fifth grid G5,
The fifth portion is provided on the cathode K side of the large-diameter cylindrical portion 33 of the sixth grid G6.
A pair of support plates covering the maximum diameter portion of the flat tubular portion 32 of the grid G5
Since the support pieces 38 are attached to the pair of support plates 34 so that the support pieces 37 of the fifth grid G5 are horizontally sandwiched from both sides, both the fifth and sixth grids G5 and G6 are large. Support pieces 37 and 38 can be provided near the cylindrical portions 31 and 33 having a diameter, whereby both grids G5 and G6 can be firmly supported and fixed, and the electron gun can be assembled with high accuracy.

In this case, the distance between the support piece 37 of the fifth grid G5 and the support piece 38 of the sixth grid G6 is such that the withstand voltage characteristic between the fifth and sixth grids G5, G6 is compensated, that is, the above-mentioned value. The size is set so that no discharge occurs between the support pieces 37 and 38. The distance between the two support pieces 37, 38 is equal to that of the insulating support member.
If the width of 36 is increased and the support piece 38 of the sixth grid G6 is slightly displaced in the axial direction of the electron gun with respect to the support piece 37 of the fifth grid G5, it is sufficient as in the normal axial arrangement of the electron gun. Therefore, it is possible to provide a sufficient space for the withstand voltage characteristics between both grids G5 and G6.

Further, since the electron gun of this example has an integrated structure in which the large-diameter cylindrical portions 31 and 33 of the fifth and sixth grids G5 and G6 forming the large-diameter electron lens are not divided,
There is an advantage that a highly accurate electron lens is formed.

[0035]

The main electron lens section for focusing the electron beam emitted from the electron beam forming section on the phosphor screen is a large-diameter cylindrical section on the phosphor screen side, and the main electron lens section is arranged on the cathode side of the large-diameter cylindrical section. A first electrode integrally formed with a flat cylindrical portion having a maximum diameter portion smaller than the large diameter cylindrical portion, and a second electrode having a large diameter cylindrical portion surrounding the large diameter cylindrical portion of the first electrode The first electrode is provided with a support piece fused to the insulating support member on the long side surface of the flat tubular portion, while the second electrode covers the maximum diameter portion of the flat tubular portion of the first electrode, and A pair of support plates having support pieces fused to the insulating support member so as to sandwich the support piece for one electrode from both sides are the same as the support pieces formed on each support plate from at least both sides of each support plate. Two fixing pieces extending in the direction and the support from the center of these two fixing pieces Attached by three fixed piece consisting of one fixed piece extending in a direction perpendicular to its first
When the support pieces for the second electrode and the support piece for the second electrode are fixed by a pair of insulating support members facing each other substantially in parallel, the support pieces for the first and second electrodes can be provided near the large-diameter cylindrical portion, respectively, and the insulation support member can be provided. It is possible to reduce the deformation of the support plate and the second electrode to which the support plate is attached due to the pressing force at the time of fusing, and to firmly fix the support plate to the insulating support member. In addition, since the support piece for the second electrode is provided so as to sandwich the support piece for the first electrode from both sides, it is not as complicated and difficult as the conventional assembly method, but is as easy and mass-produced as an ordinary electron gun. It is possible to assemble with high accuracy by a method rich in nature. Moreover, since the first and second electrodes can be firmly fixed, it is possible to improve the lens performance of the large-diameter electron lens with high accuracy, and to provide a high-performance and practical electron gun. Furthermore, the support piece of the first electrode and the second piece
Since the gap between the electrode and the support piece can be set to a sufficient size as in the case of the normal arrangement of the electron gun in the axial direction, the withstand voltage can be secured.

[Brief description of drawings]

FIG. 1 (a) is a front view showing the structure of an electron gun for a cathode ray tube according to an embodiment of the present invention, and FIG. 1 (b) is its B- line.
A sectional view taken along the line B, and FIG. 1C is a side view showing the main part thereof.

2A and 2B are views for explaining a combination of a fifth grid and a sixth grid of the electron gun, FIG. 2A is a perspective view of the sixth grid, and FIG. It is a perspective view of a 5th grid.

FIG. 3 is a diagram showing a configuration of a color picture tube.

FIG. 4 (a) is a view showing an assembly structure of an electrode forming a conventional large aperture electron lens, and FIG. 4 (b) is a view showing a different assembly structure.

FIG. 5 is a view showing a different assembly structure of electrodes forming a conventional large-diameter electron lens.

FIG. 6 (a) is a front view showing a partially sectional view of a further different assembly structure of an electrode forming a conventional large aperture electron lens, and FIG. 6 (b) is a sectional view of the first and second anode portions thereof. It is a figure.

FIG. 7 is a diagram for explaining a method of assembling the main part thereof.

8 (a) and 8 (b) are views showing different structures of the second anode, respectively.

[Explanation of symbols]

 31 ... Large diameter cylindrical portion of the 5th grid 32 ... Flat cylindrical portion 33 ... Large diameter cylindrical portion of the 6th grid 34 ... Support plate 35 ... Fixed piece 36 ... Insulating support member 37 ... Support piece 38 ... Support piece k ... Cathode G1 ... 1st grid G2 ... 2nd grid G3 ... 3rd grid G4 ... 4th grid G5 ... 5th grid G6 ... 6th grid

Claims (1)

Claim: What is claimed is: 1. An electron beam forming unit comprising a cathode and a plurality of electrodes for controlling electron emission from the cathode and focusing the emitted electrons to form an electron beam, and the electron beam. A main electron lens portion composed of a plurality of electrodes for focusing the electron beam emitted from the forming portion on the phosphor screen, and the cathode and the plurality of electrodes forming the electron beam forming portion and the main electron lens portion are In an electron gun for a cathode ray tube integrally fixed by a pair of insulating supporting members facing each other substantially in parallel via supporting pieces provided on the cathode and a plurality of electrodes, the main electron lens part is large on the phosphor screen side. A first electrode integrally formed with a flat cylindrical portion having a maximum diameter portion smaller than the large diameter cylindrical portion on the cathode side of the large diameter cylindrical portion, Is formed by the second electrode having a large-diameter cylindrical portion which surrounds the large-diameter cylindrical portion of the first electrode of said first
The electrode is provided with a support piece fixed to the insulating support member on the long side surface of the flat tubular portion, and the second electrode has the large diameter cylindrical portion with the maximum diameter portion of the flat tubular portion of the first electrode. A pair of support plates, each of which has a support piece and is fixed to the insulating support member so as to cover and sandwich the support piece of the first electrode from both sides, are attached by at least three fixing pieces, and the three fixing pieces are fixed. Two fixing pieces extending from the both sides of each supporting plate in the same direction as the supporting pieces formed on each supporting plate, and from the central portion of the two fixing pieces in the direction orthogonal to the supporting piece. An electron gun for a cathode ray tube, comprising an extending one fixing piece.