JPH0821337B2 - Electron gun structure - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an electron gun assembly, and more particularly to a so-called in-line type electron gun assembly in which three electron guns used for a color picture tube are arranged in a line. Is.

[Technical background of the invention and its problems]

As shown in FIG. 1, a color picture tube (10) has a plurality of electron beams emitted from an electron gun assembly (12) enclosed in a neck of a glass envelope (11) including a panel, a funnel and a neck. The deflecting device (14) outside the glass envelope (11) deflects and scans (13), and the fluorescent screen (1) is passed through a large number of electron beam passage holes formed in the shadow mask (15).
It is made to hit the 6) and a color image can be drawn on this fluorescent screen (16).

As an electron gun assembly (12) used for such a color picture tube (10), an electron gun having a so-called in-line type in which three electron guns are arranged in a line is generally used. .

The deflection magnetic field generated by the deflecting device (14) is a non-uniform magnetic field exhibiting a pincushion having a strong horizontal deflection magnetic field and a barrel having a strong vertical deflection magnetic field, and the three electron beams (13) are matched at the peripheral portion of the screen. It is common to form a so-called self-convergence magnetic field distribution.

When the electron beam (13) passes through such a deflection magnetic field, the electron beam (13) undergoes distortion called deflection aberration. As a result, the shape of the electron beam (13) becomes significantly distorted in the peripheral portion of the screen as shown in FIG.

That is, the bright spot is composed of two components, the core (23) and the halo (24), which are shown by diagonal lines, and the horizontal axis (XX) end (2
In 1) the core (23) becomes horizontally long and the halo (2
4) is seen, the core (23) is slanted in the diagonal part (22), the halo (24) is seen in the vertical direction of this core (23), and the vertical axis (YY) end (25 ), The core (23) becomes horizontally long, and the halo (24) is seen in the vertical direction.

As described above, since the shape of the electron beam is distorted, the resolution is deteriorated in the peripheral portion of the screen and the uniformity of focus is impaired.

Next, the most general bi-potential type electron gun structure of the related art will be described with reference to FIG. However, this FIG.
FIG. 2 is a schematic diagram showing two electron guns.

That is, the electron gun structure includes a cathode (30) and a first grid (3
1), the second grid (32), the third grid (33) and the fourth grid (34) are sequentially arranged on the central axis (35). Of these, the cathode (30), the first grid (31), and the second grid (32) are called the three-pole part, and the third
A main lens (36) is formed between the grid (33) and the fourth grid (34).

In such an electron gun assembly, for example, the cathode (30) is about 150 V, the first grid (31) is grounded, and the second grid (3
Voltage of 600V is applied to 2), voltage of about 5kV is applied to the third grid (33), and voltage of about 25kV is applied to the fourth grid (34).

By applying such a voltage, the three poles of the cathode (30), the first grid (31) and the second grid (32) form an electron beam and an object point for the main lens (36). The electron beam from the pole is focused by the main lens (36) formed by the third grid (33) and the fourth grid (34), and the focused electron beam spot is obtained on the fluorescent screen. The second grid (32) and the third grid (3
The focus lens (37) is formed by 3). The focus lens (37) has a function of pre-focusing the electron beam on the main lens (36).

The electron beam emitted from such an electron gun assembly is focused on the outside of the fluorescent screen (16) by the spherical aberration of the main lens (36) due to the focusing action of the main lens (36). That is, the electron beam has two components, a core (41) showing an underfocus characteristic and a halo (42) showing a characteristic of focusing inside the phosphor screen (16), that is, an overfocus characteristic.

The focus state of these two components differs depending on the formation state of the main lens (36). Generally, the third grid (3) is arranged so that the core (41) and the halo (42) overlap at the center of the screen.
3) Adjusted by voltage.

However, when it is deflected to the peripheral portion of the screen, the core (41) and the halo (42) do not precisely overlap each other in the peripheral portion of the screen due to the influence of the deflection aberration of the deflection magnetic field, and the result is shown in FIG. As shown in the figure, a halo (24) appears to bleed around the core (23), which is the bright spot.

As a countermeasure against this, in order to improve the uniformity of focus, a structure is proposed in which a non-rotationally symmetric lens is formed in the electron gun to improve the shape of the electron beam.

As an example thereof, an electron gun assembly in which slit-shaped concave groove portions are installed in the vertical direction on the cathode side of the third grid will be described with reference to the schematic view of FIG.

That is, the second grid of the third grid (33) of the electron gun assembly including the cathode (30), the first grid (31), the second grid (32), the third grid (33), and the fourth grid (34). By providing the electron beam passage hole portion (33a) for the (32) in the slit-shaped concave groove portion (50) provided in the vertical direction (YY), a vertical cross section near the electron beam passage hole portion (33a). As shown in FIG. 5 (a), which is a drawing, a thin portion (51) is provided in the vertical direction, and as shown in FIG. 5 (b) which is a sectional view in the horizontal direction (XX), the thickness is provided in the horizontal direction. To form a part (52). Therefore, the shape of the electric field distribution in this portion is such that the horizontal electric field distribution (54) penetrates deeper into the main lens (36) side than the vertical electric field distribution (53), and as a result,
The divergence angle of the electron beam becomes larger than that in the vertical direction.

Thus, when the electron beam having different divergence angles in the vertical direction and the horizontal direction enters the main lens (36), the vertical component having a small divergence angle enters the inside of the main lens (36). Then, due to the spherical aberration of the main lens (36), the vertical component incident on the inner side has its focus position separated from the focus position of the horizontal component passing outside the main lens (36). As a result, the electron beam core on the phosphor screen (16) becomes longer in the vertical direction during vertical deflection, for example, and copes with the phenomenon that the core becomes longer in the horizontal direction like deflection aberration.

If you explain this to the electron beam halo,
Similarly for the halo, the vertical position of the halo is more distant from the main lens (36) than that of the horizontal component, but the halo exhibits an overfocus characteristic, so that for example on the fluorescent screen (16) At the time of vertical deflection, the vertical direction becomes shorter. This will suppress the vertical halo.

By using the non-rotationally symmetric lens based on the above principle, the distortion of the electron beam can be corrected and the bleeding can be reduced.

However, if the non-rotationally symmetric lens is used with the same configuration for three electron beams, the following problems occur.

That is, the three electron beams emitted from the three electron guns arranged in an in-line type pass through the vicinity of the tube axis and are divided into a center beam located at the center of the three electron beams and side beams located on both sides thereof. However, the deflection aberration that causes the distortion of the electron beam, that is, the distortion state of the deflection magnetic field is 3
It depends on the passing position of the electron beam of the book. Therefore, the distortion states of the three electron beams are not the same. As described above, it is not appropriate to correct the distortion of the deflection aberration by using the non-rotationally symmetric lens having the same structure for the three electron beams having different distortions.

Explaining this with reference to FIG. 6, when the electron beams (61), (62), (63) arranged in an in-line type pass through the vertical magnetic field (60) showing a strong barrel shape, 3 Since the electron beam of the book has different passing positions, it passes through the place where the magnetic field distribution is different and the force (64), (6
The sizes and directions of 5) and (66) are different. Therefore, the electron beam has a shape as shown in FIG. 7 on the fluorescent screen (16), and the core (71) and the halo (72) have different sizes and shapes. That is, the side beam has a larger vertical length in both the core and the halo than the center beam.

Table 1 shows the vertical axial lengths of the core and the halo of the vertically deflected electron beam obtained by the actual measurement. However, the measurement conditions were a cathode current of 4 mA and an anode voltage of 25 kV using an in-line type electron gun structure and a self-convergence type deflection yoke that generates a non-uniform magnetic field.

As is clear from Table 1, the influence of deflection aberration is different between the center beam (G) and side beams (R) and (B), and the vertical length of the electron beam is 0.5 mm at the core and 0.35 mm at the halo. The average value of the side beam is larger than that of the center beam.

When a non-rotationally symmetric lens having the same configuration is used for three electron beams having different vertical lengths due to such deflection aberration, the non-rotationally symmetric lens has an action of making the core of the electron beam vertically long. Even if the side beam lengthened in the vertical direction due to the deviation aberration is increased by the same ratio as the center beam, the difference in the vertical direction on the actual fluorescent screen becomes larger.

Table 2 shows the vertical lengths of the core and the halo of the vertically deflected electron beam obtained by actual measurement in the case of using this non-rotationally symmetric lens. The measurement conditions are the same as in Table 1. In Table 2, an in-line type electron gun assembly was used in which a slit of 0.3 mm width in the vertical direction (vertical direction) was formed on the cathode side of the third grid.

As is clear from Table 2, the influence of the deflection aberration is further different between the center beam (G) and the side beams (R) and (B), which is 1.45 mm at the core and 1.7 mm at the halo.

On the other hand, regarding the effect of suppressing the vertical length of the halo, which is an advantage of the non-rotationally symmetric lens, comparing Tables 1 and 2, Table 1 shows that the average halo of three electron beams is 8.4 mm,
While the core is 4.6 mm, in Table 2 using a non-rotationally symmetric lens, the halo is 7.3 mm and the core is 5.5 mm.

As described above, in the structure for improving the distortion and size of the shape of the electron beam due to the deflection aberration of the non-uniform magnetic field by using the non-rotationally symmetric lens having the same configuration for the three electron beams, the size of the electron beam in the vertical direction is increased. Is significantly different between the center beam and the side beam. Moreover, effective measures to improve this have not yet been found.

[Object of the Invention]

The present invention has been made in view of the above problems,
An electron gun structure comprising three cathodes and a plurality of grids, each having at least one non-rotationally symmetric lens arranged in a row. It is an object of the present invention to provide an electron gun assembly capable of reducing the difference in size and shape of electron beams from these electron guns by making them different from each other.

[Outline of Invention]

That is, the present invention comprises an electron gun which is composed of a cathode and a plurality of grids, and which is configured to project an electron beam emitted from the cathode onto a fluorescent surface through at least one non-rotationally symmetric lens in the center and both sides. In the electron gun assembly that is arranged in a row, the non-rotationally symmetric lens is formed by a concave groove portion including an electron beam passage hole portion that is provided in a direction orthogonal to the arrangement direction of the electron guns at the center and both sides. The depth of the electron gun is different between the electron gun in the center and the electron guns on both sides, and the depth of the groove in the electron gun on the center side is greater than the depth in the groove in the electron gun on both sides. The embodiment is that the depth is shallow, and the concave groove portion including the electron beam passage hole portion forming the non-rotationally symmetric lens is provided on the cathode side of the third grid. Sen from the central electron gun The vertical and horizontal focusing actions are made different according to the degree of influence of the deflection aberration of the beam and the side beams from the electron guns on both sides, so that the size and shape of the three electron beams are made equal and the resolution of the entire screen is improved. Is to improve.

Example of Invention

Next, an embodiment of the electron gun assembly of the present invention is shown in FIGS.
It will be described with reference to the drawings.

That is, the electron gun assembly (81) has a first grid (8) having electron beam passage holes at positions corresponding to the three cathodes (83) arranged in a row, each containing a heater (82).
4), 2nd grid (85), 3rd grid (86), 4th
The grid (87) and the convergence electrode (88) are fixed to an insulating support rod (not shown) so as to have a predetermined distance from each other through their respective implantation portions. Of these, the first grid (84) and the second grid (85) are substantially flat electrodes,
The third grid (86) has two cup-shaped electrodes (86a), (8
6b), 4th grid (87), convergence electrode (88)
Are composed of cup-shaped electrodes, respectively, and are configured to emit three electron beams (89a), (89b), and (89c) with a well-known bipotential integrated in-line electron gun assembly. Although the structure is almost the same, the cup-shaped electrode (86) of the third grid (86) is used in this embodiment.
The slit-shaped recess including the electron beam passage holes (90a), (90b), (90c) in the direction (horizontal direction) perpendicular to the arrangement direction (horizontal direction) of the electron guns on the cathode (84) side of (a). Groove (9
1a), (91b), (91c) are provided, and the depth of the slit-like groove (91b) of the central electron gun that emits the center beam (89b) emits the side beams (89a), (89c) Slit-shaped concave grooves (91a) and (91c) of the electron gun on both sides
It is characterized by being formed shallower than the depth of.

According to the non-rotationally symmetric lens having such a configuration, compared to the halo of the center beam (89b), the side beam (8b
9a) and (89c) have a long halo in the vertical direction, which is different from the conventional non-rotationally symmetric lens. By making it deeper than the slit-like groove (91b) that forms the non-rotationally symmetric lens of the gun, the penetrating electric field that penetrates into the cup-shaped electrode (86a) in the electron guns on both sides is further suppressed at the cathode (83) side. The divergence angle of the electron beam due to the permeation electric field becomes small, and the incident position on the main lens passes through the inside where the spherical aberration is small. As a result, the focus positions of the vertical components of the side beams (89a) and (89c) exhibit overfocus characteristics. With regard to the halo component, the halo component can be further moved to the phosphor screen, and the vertical length of the halo of the side beam can be reduced.

Based on this principle, if the depth of the slit-shaped grooves of the electron guns on both sides of the central electron gun is made deeper, the electron beam correction that takes into account the degree of deflection aberration due to the vertical deflection magnetic fields of the center beam and side beams Is possible. As an actual design value, the depth of the slit-like groove is
0.3mm, with electron guns on both sides of 0.45mm to 0.6mm,
Good results were obtained.

〔The invention's effect〕

As described above, according to the present invention, it is possible to improve the non-uniformity of the focus due to the difference in the distortion of the shapes of the three electron beams in the peripheral portion of the screen, and the structure is relatively simple.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of a color picture tube,
2 is an explanatory plan view showing the electron beam shape on the fluorescent screen, FIG. 3 is an explanatory schematic diagram showing the structure of a bipotential type electron gun, and FIG. 4 is an electron beam from the main lens in FIG. 5 is a schematic diagram for explaining the locus of FIG. 5, FIG. 5 is a diagram showing the effect of the non-rotationally symmetric lens, FIG. 5 (a) is an explanatory diagram showing the vertical component of the electron beam, and FIG. 5 (b) is Explanatory drawing showing the horizontal direction component of the electron beam, FIG. 5 (c)
Is a partially enlarged perspective view showing a slit-shaped groove provided on the cathode side of the third grid in FIGS. 5 (a) and 5 (b), and FIG. 6 is in a barrel-shaped non-uniform vertical magnetic field. 6 is a schematic view for explaining the force received by the three electron beams, FIG. 7 is a plan view showing the shape of the electron beam on the fluorescent surface of FIG. 6, and FIGS. 8 and 9 are electron guns of the present invention. FIG. 8 is a view showing an example of the structure, FIG. 8 is a sectional view for explaining a bipotential type integrated in-line electron gun structure, and FIG. 9 (a) is a cup-shaped electrode on the cathode side forming the third grid. FIG. 9B is a side view showing the cup-shaped electrode on the cathode side which constitutes the third grid. 12 ... electron gun, 13,41,43 ... electron beam 14 ... deflecting device, 15 ... shadow mask 16 ... phosphor screen, 23 ... core 24 ... halo, 30,83 ... cathode 31,84 ... first grid, 32,85 … Second grid 33,86… Third grid, 34,87… Fourth grid 36… Main lens, 37… Focus lens 33a, 90a, 90b, 90c… Electron beam passage hole 50,91a, 91b, 91c… Slit Groove

Claims (3)

[Claims] 1. An electron gun comprising a cathode and a plurality of grids, wherein an electron beam emitted from the cathode is projected onto a fluorescent surface through at least one non-rotationally symmetric lens in the center and In an electron gun assembly arranged in a row on both sides, the non-rotationally symmetric lens is formed by a concave groove portion including an electron beam passage hole portion provided in the center and in a direction orthogonal to the arrangement direction of the electron guns on both sides, An electron gun assembly characterized in that the depth of the groove is different between the electron gun in the center and the electron guns on both sides. 2. The electron gun assembly according to claim 1, wherein the depth of the concave groove portion of the central electron gun is shallower than the depth of the concave groove portions of the electron guns on both sides. . 3. The electron gun according to claim 1, wherein a concave groove portion including an electron beam passage hole portion forming the non-rotationally symmetric lens is provided on the cathode side of the third grid. Structure.