JPH0416893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun for a color picture tube, and more particularly to the structure of an electrode forming a main electron lens of an electron gun that is attached to a shadow mask type color picture tube and emits a plurality of electron beams. be.

A shadow mask type color picture tube accelerates and collects thermoelectrons emitted from multiple electron beam sources of an electron gun installed inside the network. It is designed to reproduce color images.

Various types of electron guns are known, but in all of them, thermionic electrons emitted from an electron beam source, that is, a cathode, are converted into electron beams, which are accelerated and focused onto a phosphor screen by a main electron lens. It is made to do. Generally, an electrostatic lens is used as the main electron lens, and the characteristics of the electrostatic lens are determined by the diameter of the lens, similar to optical lenses.

Generally, the maximum diameter of the main electron lens is determined by the inner diameter of the picture tube network and the structure of the electron gun. For example, when emitting electron beams arranged in a row from an electron gun consisting of electrodes each having an independent structure, the diameter of the main electron lens is approximately 30 mm.
%, when emitted from an electron gun consisting of an integrated structure of electrodes, the diameter of the main electron lens is limited to about 28%, which cannot be a sufficient diameter due to its characteristics.

On the other hand, a shadow mask type color picture tube reproduces a color image by focusing three electron beams onto a phosphor screen and scanning them both horizontally and vertically using a deflection device. In this case, focusing the three electron beams on the phosphor screen is called convergence, and in general, the smaller the neck diameter, the better the characteristics are obtained, and the power required to deflect and scan the electron beams. That is, the deflection power is proportional to the neck diameter, and the smaller the neck diameter, the less power is required.

As mentioned above, electron beam focusing, convergence, and deflection scanning are interrelated with each other with respect to the net diameter, and the current situation is that a compromise between the two is generally used in the design, especially in the case of recent color picture tubes. The diameter of the net is becoming ultra-thin from the conventional 29.1 mm to 22.5 mm in order to save resources and power. Naturally, as the net diameter becomes smaller, the electron gun also becomes smaller and accuracy becomes more demanding.

Next, the structure of a shadow mask type color picture tube will be explained with reference to FIG.

In other words, the shadow mask type color picture tube produces red, green, blue, and
A panel 2 is formed by adhering a phosphor screen 1 in which a phosphor layer emitting light in each color is regularly provided in the form of dots or bands, and a network 4 connected to this panel 2 via a funnel 3. and an electron gun 8 that emits three electron beams 7 into a high-vacuum envelope consisting of a stem 6 in which a stem pin 5 is implanted; Shadow mask 9 to be projected onto the phosphor layer
and a deflection device 10 attached to the outer wall from the funnel 3 to the neck 4. This deflection device 10 directs the electron beam 7 to the phosphor screen 1.
The phosphor screen 1 is deflected and scanned in the horizontal and vertical directions to reproduce a color image on the phosphor screen 1.

The electron gun 8 installed in such a shadow mask type color picture tube is roughly divided into an independent electrode electron gun and an integrated electrode electron gun. An example will be explained. As shown in FIG. 2, at least a cathode 11, a first grid 12, a second grid 13, 2
a third grid 14 consisting of bottomed cylindrical electrode elements 14 ₁ and 14 ₂ ; a fourth bottomed cylindrical grid 15;
It consists of a convergence electrode 16 shown by a broken line and an electrode support 17 made of glass or the like that implants and supports implant pieces provided on each of these electrodes,
The cathodes 11 are independent corresponding to the three electron beams, but the other electrodes, namely the first grid 12,
The second grid 13, the third grid 14, and the fourth grid 15 each have a structure in which three electron beam passage holes are formed in the integrated electrode.

In the electron gun 8 having the above structure, the cathode 11, the first
The grid 12 and the second grid 13 are referred to as a triode, which emits thermionic electrons and forms an object point for a main electron lens to be described later, and a main electron lens is formed between the third grid 14 and the fourth grid 15. , adapted to focus the electron beam onto a phosphor screen. In addition, in the electron gun shown in FIG. 2, the passage holes for three electron beams are bored in the integrated electrode, so the assembly accuracy after implanting and fixing them to the electrode support 17 through the implant pieces. is better than an independent electrode electron gun, and the center axis spacing of the through hole is 1
8 is also constant.

However, for example, the third grid 14 of the electron gun 8 described above is connected to the electrode element 1 as shown in FIGS. 3 and 4.
The bottom part 21 of 4 ₁ has electron beam passage holes 22, 23 and 2 for injecting the electron beam from the triode part.
4 is perforated, so there is not much problem, but the electrode element 14 ₂ has a large diameter electron beam passage hole 32, 32 and 3 which forms the main electron lens in the bottom part 31.
4 are bored, and these passage holes 32, 33 and 3
4 has a substantially perfect circular shape, and the diameter 35 of the passage holes 32, 33, and 34 cannot be made sufficiently large due to the center axis spacing 36 and the widths of the bridge portions 37, 38. Further, the passage holes 32, 33, and 34 are provided with an electrostatic lens formed in the center passage hole 32 and an electrostatic lens formed in the passage holes 33, 34 on both sides so that they do not interfere with each other. wall portion 32 ₁ ,
33 ₁ and 34 ₁ , that is, burring portions are provided independently. In the figure, 40 is a grafted piece, 1
4 _1a and 14 _2a are flange parts. The length 39 of this wall portion is generally required to be at least half the diameter of the passage holes 32, 33, and 34. Moreover, the width of the bridge portions 37 and 38 is the width of the wall portions 32 ₁ , 33 ₁ and 34 ₁
Due to the burring process, it cannot be made narrower than a certain level, and the limit is the thickness of the metal plate forming the electrode element 14 ₂ , the strength of the burring jig used during the burring process, especially the die, and the wall portions 32 ₁ , 33 ₁
It is impossible to make the width of the bridges 37, 38 extremely narrow and to enlarge the diameter 35 of the passage holes 32 _, 33 and 34. When such an electrode is applied to an electrode for a main electron lens for a harmonic network of 22.5 mmφ and the lengths 39 of the wall portions 32 ₁ , 33 ₁ and 34 ₁ are set to 3 mm or more, the passage holes 32 , 33 and The diameter of 34 is approximately 3.5 mm to 3.9 mmφ. It is generally said that the spherical aberration of a lens is inversely proportional to the cube of its diameter, so a main electron lens formed by such a small diameter passage hole has the disadvantage of extremely large spherical aberration. Also, the wall portions 32 ₁ , 3
Mechanical distortion is likely to occur in the electrode element 14 ₂ during the process of forming 3 ₁ and 34 ₁ , and changes in the electrode element 14 ₂ may occur during the aging process of the color picture tube and the heating process during operation. Another drawback is that it tends to increase the spherical aberration of the main electron lens.

In order to eliminate the drawback that the passage holes 32, 33, and 34 cannot be enlarged, the electrode element facing the fourth grid is structured as shown in FIGS. 5 and 6. Things are being thought of.

That is, the electrode element 14' ₂ has electron beam passage holes 42 and 43 forming a main electron lens in the bottom part 41.
and 44 are bored, but in order to enlarge the main electron lens, the diameter 45 of the passage holes 42, 43 and 44 is approximately equal to or slightly larger than the center axis spacing 46. Further, the passage holes 42, 43, and 44 are provided with holes to prevent the electrostatic lens formed in the central passage hole 42 and the electrostatic lenses formed in the passage holes 43, 44 on both sides from interfering with each other. Wall portions 48 ₁ , 44 ₁ or burring portions are provided. In addition, the wall portions 43 ₁ and 44 ₁ are the passage hole portions 4
2, 43, and 44 are approximately equal to or slightly larger than the center axis spacing of the electron beam, so they are not provided at opposing positions.

However, in the electrode element ₁₄₂ , the passage holes 42, 43 and 44 are first formed as one large hole, that is, a communicating hole, and then the metal plates 47 and 48 are fixed by means such as welding to form independent holes. has been formed. Therefore, when press forming a thin plate with a thickness of about 0.4 mm, the passage holes 42, 43 and 44 are
There is no bridge between the electrode elements, so the accuracy of the finished electrode element is significantly degraded compared to one with a bridge, and for example, twisting occurs.
Further, the metal plates 47 and 48 are not necessarily arranged with high precision, and the precision of their combination is still a problem. Furthermore, when assembling an electron gun, there is a problem in that it is easily distorted by mechanical stress from an assembly jig, etc., and the effect of increasing the size of the passage hole cannot be fully exhibited.

The present invention has been made in view of the above-mentioned drawbacks and problems, and an object of the present invention is to provide an electron gun for a color picture tube that has excellent mechanical precision and is capable of improving electron beam focusing performance.

Next, an embodiment of an electron gun for a color picture tube according to the present invention will be described with reference to FIGS. 7 to 10.

That is, as shown in FIG. 7, the color picture tube electron gun 58 has a third grid consisting of a cathode 61, a first grid 62, a second grid 63, a bottomed cylindrical support member ₆₄₁ , and a perforated plate member ₆₄₂ . 64, a fourth grid 65 also made of a perforated plate-like member, a convergence electrode 66, and an electrode support 67 made of glass or the like for implanting and supporting the implant pieces provided on each of the electrodes other than the convergence electrode 66. The cathodes 61 are independent corresponding to the three electron beams arranged in a row, but the other electrodes, that is, the first grid 62, the second grid 63, the third grid 64, and the fourth grid 65 are integrated. Each electrode has a structure in which three passage holes for electron beams are formed.

In the electron gun 58 having such a structure, the cathode 6
1. The first grid 62 and the second grid 63 are referred to as a triode, which emits thermionic electrons and forms an object point for a main electron lens, which will be described later. is formed,
The electron beam is adapted to be focused onto a phosphor screen. In the electron gun shown in FIG. 7, passage holes for three electron beams are formed in the integrated electrode, so the assembly accuracy after implantation and fixation on the electrode support 67 through implantation pieces is low. This is superior to an independent electrode electron gun, and the passage hole portion, ie, the center axis spacing 68 of the electron beam, is also constant.

Next, the structure of the third grid of the electron gun 58 will be explained with reference to _FIGS . Portions 72, 73, and 74 are drilled, and the opening has a flange portion 75. Further, at least the inner wall of the side wall portion 76 is coaxial with the axes of the passage holes 72, 73, and 74, and the implant piece 80 is fixed to the outer wall by means such as welding.

Next, the flange portion 75 of the bottomed cylindrical support member 64 ₁
This perforated plate member 64 ₂ is placed and fixed in the passage hole portion 42 of the electrode element 14 ₂ ′ in FIGS. 5 and 6 and the wall portion 4 _.
3 ₁ . . . to form the metal plates 47 and 48, and the conditions to be met are as follows.

(1) The diameter 85 of the passage holes 82, 83, and 84 is approximately equal to or larger than the center axis spacing 68 of the electron beam.

(2) Bridge portions 87 and 88 are perforated plate-like members 64 ₂
is formed integrally with the height 90 and the thickness 8
be lower than 9 by a specified amount.

(3) Strong overall mechanical precision and mechanical shock resistance.

Regarding the first requirement, the diameter of the main electron lens should be increased to such an extent that the focusing characteristics of this lens are not deteriorated, and the diameter is determined by the type of color picture tube.

The second requirement is that the bridge portions 87, 88 are formed integrally with the perforated plate-like member ₆₄₂ , and are formed a predetermined amount lower than the surface facing the fourth grid, so that the central passage hole The electrostatic lens is formed smoothly in both the longitudinal direction and the transverse direction (the direction in which the bridge portion is located), making it possible to reduce asymmetrical aberrations of the electron beam.

In other words, in FIG.
The (X-X') and (Y-Y') planes including 8 are set lower than the outer peripheral wall 800 by a predetermined amount 801. For this reason, the equipotential lines forming the electrostatic lens are drawn in the longitudinal direction (X-X' axis) and the transverse direction (Y-
(Y' axis) are smoother than when the plane including the bridge is flush with the outer peripheral wall, and therefore it is possible to create an electrostatic lens without astigmatism.

This is because when the plane containing the bridge and the outer peripheral wall are on the same plane, the shape of the aperture becomes oval, so the electrostatic lens also has strong asymmetry, and astigmatism is reduced. By occurring. Conversely, if the bridge portions 87 and 88 do not exist at all, the electrostatic lens corresponding to the central hole 82 and the electrostatic lenses corresponding to the side holes 83 and 84 will interfere, resulting in astigmatism. do. That is, in order to obtain an enlarged electrostatic lens without astigmatism, the plane including the bridge portion needs to be set lower than the plane of the outer peripheral wall.

The third requirement is that the bridge part is integrally formed from the beginning instead of fixing a metal plate as in conventional electrodes, so the mechanical strength and mechanical shock resistance are as shown in Figures 5 and 6. It's a lot better than anything else.

That is, the overall shape of the perforated plate member 64 ₂ is almost the same as the conventional one except for the lack of a flange, but the shape of the passage hole is similar to that of the conventional one.
In the vicinity of the surface facing the grid, three passage holes are communicated with each other to form one communication hole, and three passage holes are independent of the bridge parts 87 and 88. Such a structure is the same in the case of the fourth grid 65.

In addition to the above-mentioned advantages, this embodiment has the advantage that it is hardly distorted even by mechanical stress during assembly of the electron gun. As a result, the reference point (reference plane) during assembly can be selected at any point on the perforated plate-like member ₆₄₂ , so there is no restriction on the assembly method. For example, the reference point during assembly can be set on the outer wall instead of on the passage hole, which facilitates automatic assembly.

Another advantage of this example is that it has excellent resistance to treatment by tumbling. That is, in general, in an electron gun, it is necessary to remove minute protrusions on the electrode surface in order to prevent a discharge phenomenon occurring between the electrodes. To do this, a mechanical polishing process called tumbling is applied. At this time, the electrode is subjected to mechanical shock, and the degree of distortion is large, especially in the shape of conventional electrodes that do not have a bridge part or the shape that has a metal plate attached, but in this example, such distortion is hardly affected. .

Next, to show the specific dimensions of the electrode element ₆₄₂ , the center axis distance 68 of the electron beam is 6.6mm, and the bridge part 8
7, 88 have a width of 0.3 mm, and the diameter of the passage holes 82, 83, and 84 in the longitudinal direction is 7.0 mm.
The height 90 of 88 is 1.5 mm, and the thickness 89 is 2 mm.

Next, FIG. 11 shows a perforated plate member 64 ₂ ' adapted to another embodiment of the present invention. Figures 8 to 1 in the figure
The same parts as in FIG. 0 are given the same reference numerals and will not be particularly described.

That is, the perforated plate-like member 64 ₂ ' has passage holes 82 and 83.
and 84 with bridge portions 87 and 88 between them.
It is characterized in that it is formed from a perforated plate-like member 94 ₁ and a second perforated plate-like member 94 ₂ with which passage holes 82', 83', and 84' are communicated.

In the electrode shown in FIG. 11, the bridge portion is formed by a first perforated plate member 94 ₁ and the outer peripheral wall is formed by a second member 94 ₂ . Therefore, the plane including the bridge portion is set lower than the outer peripheral wall by the thickness of the second member ₉₄₂ .
Further, by forming the two perforated plate members 94 ₁ and 94 ₂ separately and integrating them in this way, there is an advantage that machining becomes easy.

Although the above embodiment mainly describes a bipotential electron gun that emits and focuses electron beams arranged in a row, the present invention is not limited to this, and can be applied to other types of electron guns. can. Furthermore, it is of course possible to use the perforated plate-like member itself as an electrode without being placed and fixed on the cylindrical support member.

As mentioned above, the electron gun of the present invention completely solves the mechanical problems caused by enlarging the diameter of the main lens, and has high precision and good convergence characteristics, so its industrial value is extremely high. It is.

[Brief explanation of drawings]

Fig. 1 is a simplified explanatory diagram of a color picture tube, Fig. 2 is a side view showing an example of a conventional electron gun for color picture tubes, Fig. 3 is a plan view seen from the fourth grid side of the third grid, and Fig. 4. 3 is a cross-sectional view taken along the line A-A', and FIG. 5 shows an electrode element placed opposite the fourth grid of the third grid for the purpose of enlarging the passage hole. A plan view, FIG. 6 is a sectional view of FIG. 5 taken along line B-B', and FIGS. 7 to 10 are views showing an embodiment of the electron gun for color picture tube according to the present invention. Figure 7 is a side view, Figure 8 is a side view, and Figure 8 is a side view.
The figure is a plan view of the third grid viewed from the fourth grid side, FIG. 9 is a sectional view taken along line C-C' of FIG. 8, FIG. 10 is an exploded perspective view, and FIG. The figure is an exploded perspective view of a perforated plate member adapted to another embodiment of the present invention. 8, 58...electron gun, 12,62...first grid, 13,63...second grid, _14,64 ...third grid, _141,142 ...bottomed cylindrical electrode element,
37, 38, 87, 88...Bridge part, 47, 4
8...Metal plate, 64 ₂ , 64 ₂ '... Perforated plate member, 6
4...Bottomed cylindrical support member.

Claims (1)

[Claims] 1. A plurality of electrodes including an electrode group forming a main electron lens for focusing three electron beams arranged in a row onto a phosphor screen, and an electrode support that supports these electrodes. In the electron gun for a color picture tube, the opposing electrodes for forming the main electron lens are made of a thick perforated plate-like member in which three electron beam passage holes are formed. It consists of substantially integrated electrodes separated by a bridge portion in which the beam passage hole portion is integrally molded, and the distance between the opposing electrodes is smaller than the distance between the opposing electrodes between the outer circumferential walls so that the three electron beams pass through. An electron gun for a color picture tube characterized in that the distance between the planes obtained by connecting the ends of the bridge section between the holes on the opposing surface side is wide. 2. The bridge portion including at least the line connecting the center of the passage hole is missing in the difference between the height of the outer circumferential wall on the opposing electrode surface side and the height of the plane obtained by connecting the bridge portions, and three bridge portions are missing. 2. The electron gun for a color picture tube according to claim 1, wherein the passage hole portions communicate with each other through the missing portion.