KR890003729B1 - Electron gun for brown tube - Google Patents

Abstract

The electron gun comprises a cathode (K) emitting electron, the first grid (1) controlling a quantity of the electron, the second grid accelerating the velocity of the electron and a grid for connector. The second grid is composed of the first material that electron-beam passes through the hole and of the second material whose horizontal length is longer than the vertical length. The gun minimizes the ratio and the variation of the focus voltage against the variation of beam-current.

Description

CRT gun

1 is a plan view showing an example of an electron gun according to the prior art.

2 is a plan view showing an electron gun according to the present invention.

3a and 3b show the front and back sides of the acceleration grid used in the present invention, respectively.

4 is a view showing an auxiliary electrode used in the present invention.

5 is a longitudinal sectional view of the electron gun shown in FIG.

FIG. 6 (a) is a diagram showing the space potential distribution near the three poles of the conventional electron gun and the trajectory of the electron beam accordingly. FIG.

Fig. 6 (b) is a diagram showing the space potential distribution near the three poles of the electron gun and the trajectory of the electron beam according to the present invention.

7 (a) and 7 (b) are diagrams for comparing the beam spot shape according to the prior art with the beam spot shape according to the present invention, respectively.

FIG. 8 is a photograph of the change of the beam spot in the center of the screen when the beam current is changed. FIG. 8 (a) is a beam spot photograph by a conventional electron gun, and FIG. 8 (b) is a beam spot photograph by an electron gun of the present invention. .

9 is a graph showing the correlation of the focus voltage to the beam current.

* Explanation of symbols for main parts of the drawings

1: 1st grid 2, 2 ': 2nd grid

3: third grid 5: insulation support

15: crude electrode 4: fourth grid

K: cathode

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a CRT for a CRT, and more particularly to an improvement of an inline electron gun used for a CRT.

The CRT electron gun is a dislocation lens formed by a plurality of cylindrical or plate electrodes arranged coaxially, and emits and connects an electron beam emitted from the cathode. To form. This light emission spot (referred to as a beam spot for convenience) constitutes a pixel of an image reproduced on a fluorescent surface, and its size becomes an important factor in determining the sharpness of an image.

However, it can be seen that the spot of the electron beam changes in size as the beam current changes, and as a result, the sharpness of the screen also changes. This phenomenon is due to the different beam size and focus voltage for changing the beam current, which remains a problem to be improved in the future.

Accordingly, an object of the present invention is to minimize the change in the focus voltage against the change in the beam current, to obtain a high quality beam electron density, to reduce the beam distortion at the periphery of the screen due to the deflection yoke to improve the sharpness of the CRT To provide.

In general, the resolution of a CRT is related to the pitch of the shadow mask and the beam spot diameter on the screen. Since the pitch of the shadow mask is fixed, reducing the beam spot diameter remains the final challenge of resolution improvement.

The beam spot diameter Dt on the screen is represented by the following equation.

Dt = [(Dx + Dsa) ² + (Dsc) ² ] ^1/2

Where Dx is the magnification component of the beam by the lens ratio, Dsa is the magnification component of the beam by spherical aberration in the main lens system, and Dsc is the beam magnification component by the space charge repulsion effect on the front of the screen.

In order to reduce the beam spot diameter of the electron gun, the Dx component and the Dsa component have been improved so far by large-diametering the main lens of the electron gun.

In the present invention, unlike the conventional approach, the Dx component and the Dsa component are improved by controlling the electron beam divergence angle at the three pole portions (collectively referred to as the cathode, the first grid, and the second grid) of the electron gun.

In addition, the present invention seeks to reduce the distortion of the electron beam by the magnetic field of the deflection by changing the spatial potential distribution in the vertical and horizontal directions near the three poles for the focus uniformity on the screen.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated, comparing with a conventional example with reference to an accompanying drawing.

FIG. 1 shows a schematic structure of a conventionally widely used bipotential electron gun, which is three cathodes (K) each emitting three electron beams independently, and a first grid for controlling the amount of the electron beams. 1), the second grid 2 for accelerating the electron beam, and the plurality of electrodes 3 and 4 constituting the kettle lens are arranged in series at a predetermined interval, and then supported by the insulating support 5. Consists of. Here, the cathode signal K has a luminance signal voltage, the first grid 1 has an OV voltage (Vg1), the second grid 2 has a voltage Va2 of 400-1000 V, and the third and fourth grids. (3) and (4) are applied with a voltage Vg3 of 6-10 KV and a voltage Eb of 25 KV, respectively.

Here, the cathode K, the first grid 1 and the second grid 2 are referred to as so-called tripoles, and as shown in FIG. 7 (a), the electron beam emitted from the cathode K is focused. The tripolar lens LI is formed to form a crossover. Then, the second and third grids 2 and 3 constitute the prefocus lens L2 according to the voltage applied to each, and the divergence angle of the electron beam incident on the main lens L3 at the crossover point. It serves to reduce.

However, despite such a configuration, the divergence angle α1 of the electron beam is formed to be 4-6 ° large and condensed in the main lens L3, thereby forming a large amount of soft on the fluorescent surface. Still remained.

Moreover, the electron beam emitted from the three poles is distorted by the deflection magnetic field, in particular the pincushion magnetic field and barrel magnetic field, thereby displaying the beam beam horizontally extended as shown in Fig. 8 (a) at the periphery of the screen. There was a disadvantage that focus uniformity could not be obtained.

In contrast, in the present invention, as shown in FIG. 2, the first grid 1 maintained at the ground potential by providing the deceleration control electrode 1 'between the second grid 2' and the third grid 3. The first part 2a '(see also 3a) having three annular holes through which the second grid 2' can pass through the second grid 2 ', respectively. And the second member 2b '(see also 3b) in which the opening in the direction in which the horizontal length is longer than the vertical length are formed to solve the aforementioned conventional problems.

The slots formed in parallel to upper and lower peripheral portions of the first and second members of the second grid 2 'are formed to increase the diameter strength of these members.

FIG. 4 is a view showing the structure of the members constituting the deceleration control electrode 1 '. Two members of FIG. 4 are combined to form a cylindrical deceleration control electrode. The diameter D of the electron non-passing through hole formed in Fig. 2) is approximately equal to or slightly larger than the vertical length W2 of the longitudinal opening in the second member 2b 'of the second grid.

Then, the horizontal length W1 of the rectangular opening in the second member 2b 'is equal to or greater than 2S when the distance of the electron beam passing through hole in the first member 2a' is S.

5 is a longitudinal sectional view of the electron gun according to the present invention including the electrodes described above. In the present embodiment, the first grid 1 and the deceleration control electrode 1 'are electrically connected internally so that the voltage Vg1 of OV is applied and the voltage of 400-1000V is applied to the second grid 2'. A voltage Vg3 of 6-10 KV and a voltage Eb of 25 KV are respectively applied to the third grid 3 and the fourth grid 4 by Va2.

With this configuration, the zero potential is applied to the deceleration control electrode 1 'as shown in FIG. 6 (b), so that the space potential distribution between the second grid 2' and the third grid 3 is reduced. The gradient is formed large, and as a result, the prefocus lens L2 'in this embodiment is much strengthened than the conventional prefocus lens L2. That is, the thickness of the lens becomes thicker than the conventional one, and the magnification increases, and the aperture also becomes large, resulting in much smaller aberration of the lens. As a result, the electron beam emitted at the crossover point and preliminarily connected by the focus lens L2 'is incident toward the main lens L3 at a divergence angle α2 (α2α1) smaller than that of the conventional art. Therefore, the magnification component Dx of the beam spot by the lens magnification is reduced by approximately ³ (tan α1 / tan α2) as compared with the conventional art.

The size of the prefocus lens L2 'depends on the thickness G of the deceleration control electrode 1', the hole diameter D in the electrode, and the second grid 2, depending on the desired current utilization range of the cathode ray tube. And the distance Gp1 between the deceleration control electrode 1 'and the distance Gp2 between the deceleration control electrode 1' and the third grid 3 may be changed.

In this embodiment, the following relationship was set for the above parameters by using numerical analysis by an electronic calculator. That is, G / D = 0.2-0.4, Gpl = 0.4-0.6mm, and Gp2 = 0.4-0.6mm. In this state, while changing the beam current IK to 0.5 mA, 1.0 mA, 2.0 mA, and 3.0 mA, the shape of the beam spot in the center of the screen was observed. As a result, the conventional beam shown in FIG. It was confirmed that the size was reduced as shown in FIG. 8 (b) rather than the spot diameter.

In addition, in the conventional electron gun, when the focus voltage Vg3 applied to the third grid 3 changes due to the change in the beam current, the beam spot size on the screen is large as shown in FIG. 8 (a). Although varying in width, in the electron gun of the present invention, the rate of change of the beam spot size due to the beam current fluctuation in the medium current and the low current region of 2 mA or less appears much smaller than before. As can be seen from the characteristic curve of the beam current-focus voltage (Fig. 9 (b)), in the electron gun of the present invention, even if the beam current fluctuates in the current region of 2 mA or less, the focus voltage Vg3 remains almost linear. On the contrary, in the conventional electron gun, as shown in the characteristic curve of FIG. 9 (a), the focus voltage changes in a curve non-uniformly with the change of the beam current.

In view of such a point, it is possible to provide a screen having excellent resolution, blooming, and spreading characteristics when applied to an industrial color monitor or the like, which is particularly used in low current of the electron gun of the present invention.

However, in FIG. 9 (b), the electron gun of the present invention exhibits blooming characteristics in a large current region having a beam current of 3 mA or more, but this is a ratio of thickness to diameter of different reduction control electrodes 1 '(G / D). And it can solve by adjusting the distance between each electrode, and can also solve with the main lens of the multistage focusing system conventionally used in the art. Meanwhile, in the present invention, the horizontal length W1 is vertical in the second member 2b 'of the second league 2' in order to eliminate the unevenness of focus at the periphery of the screen shown in FIG. 7 (a). The longitudinal opening longer than the length W2 is provided.

With this structure, the horizontal component of the electron beam emitted from the second grid 2 'and connected again in the main lens L3 is stronger than the vertical component, so that the horizontal focal length Fh in the main lens is It becomes shorter than the vertical focal length Fv at.

In this embodiment, the dimension of the opening in the second member 2b 'of the second grid electrode 2' is set to W2 / W1 = 0.3-0.6 to obtain a relationship of Fv / Fh = 1.3-1.5. The beam spot of FIG. 7 (a) was reduced in the horizontal direction and extended in the vertical direction to achieve focus uniformity over the entire screen as in FIG. 7 (b).

At this time, the spot of the center portion of the screen is slightly longer than the horizontal length (Eh) vertical length (Bv) appears, which is not enough to adversely affect the improvement of the overall focus uniformity of the screen.

As described above, according to the electron gun of the present invention, a deceleration control electrode electrically connected to the first grid maintained at the ground potential is provided between the second grid for accelerating the electron beam and the third grid for forming the connection lens. By reinforcing the focus lens, the diameter of the electron beam passing through the main lens is reduced, so that spherical aberration of the electron beam due to the aberration of the electron lens can be reduced without increasing the diameter of the main lens. The phenomenon can be reduced, and economic advantages can be achieved because it is not necessary to provide a separate power source to be applied to the deceleration control electrode. In addition, it is possible to obtain a stable and clear screen by improving focus uniformity of the entire screen.

In addition, according to the present invention, since the potential difference is not so large as compared with the potential difference between electrodes of the conventional multi-stage focusing electron gun, the problem of spark generation can be solved, and the electrodes forming the prefocus lens are also referred to as the third (a). As shown in (b) and 4, the assembly precision can be improved by assembling using guide holes formed on the left and right sides of the electrode, thereby obtaining high reliability.

Although the main lens method illustrated in the above description and the drawings is of a bipotential type, the forming means of the focus lens according to the present invention can be applied to a unipotent cell type or a multi-stage focused electron lens.

Claims (1)

(Correction) A cathode for emitting an electron beam, a first grid for controlling the electron beam amount, a second grid for accelerating the electron beam, and a plurality of focusing grids constituting the kettle lens at predetermined intervals In a CRT tube array, the second grid described above is formed by a first member having a hole that can pass through an electron beam, and a second member having a rectangular opening whose horizontal length is longer than the vertical length. And a deceleration control electrode having a tubular shape having a predetermined thickness between the second grid and the third grid, wherein the same voltage as that of the first grid is applied to the deceleration control electrode.

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