JPH07262936A - Electron gun for color picture tube - Google Patents

Abstract

PURPOSE: To provide a method to improve resolution throughout the entire screen regions of a color picture tube by installing multiple electrodes that apply a predetermined voltage between a static focusing electrode and dynamic focusing electrode surfaces that face each other. CONSTITUTION: A constant focusing voltage Vsf is applied to a grid electrode 23 through a direct voltage source; a focusing voltage Vdf , which is produced by adding a constant dc focusing voltage Vdf and a voltage V varying in proportion to electron beam deflection on the screen, is applied to an accelerating/ focusing electrode 25. The same low voltage Ec2 as a voltage applied to an electrode 12 is applied to an electrode 24 located in between the electrode 23 to which the static focusing voltage Vsf is applied and the electrode 25 to which the dynamic focusing voltage Vdf is applied. When only the voltage Vsf of the constant focusing voltage through the direct voltage source is applied to a front edge auxiliary focusing lens composed of an upper electrode 23 of the grid 23 and a lower electrode 25a of the grid electrode 25, the focusing and diffusing actions of the electron beams in both the horizontal and vertical widths are the same so that the beam spots form a circle.

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 color picture tube, and more particularly to an electron gun for a color picture tube having a dynamic focus lens field which changes depending on a deflection amount of an electron beam deflected by a deflection yoke of the color picture tube.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 1, an electron gun for a color picture tube has grid electrodes (11, 12,
13 and 14) A large number of "in-line integrated" grid electrodes (11 to 14) in which a plurality of electron beam passage holes are perforated in a perfect circle in a horizontal in-line on a plane are stacked to form each grid electrode (11 to 14). ), A pair of bead glass (Bead Glass) is buried and fixed and maintained.

As shown in FIG. 1, the conventional electron gun in which the grid electrodes (11 to 14) are laminated while sequentially maintaining a constant interval in the tube axis direction as described above has a heater (not shown).
The cathode that emits thermionic electrons by the heat source generated by the
10), an electron beam forming unit (BFR) composed of first and second grid electrodes (11, 12) for controlling and accelerating the electron beam generated from the cathode (10), and inside the electron beam forming unit It is composed of first and second accelerating / focusing electrodes (13, 14) for forming a beam spot on the screen of a color picture tube that finely focuses the electron beam accelerated from the second grid electrode (12). It is composed of a main electrostatic focusing lens field and a shield electrode (15) for shielding and weakening the leakage magnetic field of the deflection yoke.

There is also an example in which an electron gun for performing multi-stage focusing is applied in order to improve the focusing effect, but such an electron gun for a color picture tube has the electron beam forming unit (BFR) and the main electrostatic focusing lens. 3rd and 4th for auxiliary focusing between and
There is also an example in which a focusing lens field is formed by inserting a grid electrode. The operation of the conventional electron gun for a color picture tube thus constructed will be described in detail with reference to FIGS. First, when heat is generated from the heater installed inside the cathode (10), the cathode (10) heated by the generated heat emits thermoelectrons. The electron beam emitted from the cathode (10) is controlled by the first grid electrode (11) which is a control electrode, is accelerated by the second grid electrode (12) which is an acceleration electrode, and is incident on the main electrostatic focusing lens field. It The electron beam incident on the main electrostatic lens field is finely focused by the first and second accelerating / focusing electrodes (13, 14), and then passes through a mask installed on the inner surface of the fluorescent screen (not shown). It will emit light by colliding with the phosphor screen.

At this time, the electron beam passing holes from the first grid electrode (11) to the second accelerating / focusing electrode (14) are perforated in a state close to a perfect circle, and the first accelerating / focusing electrode (13). ) And the main electrostatic focusing lens formed by the second accelerating / focusing electrode (14) also become a lens with a circular axis symmetry, so that when an operating power is applied to the electron gun, an electron beam passing through the electron beam passage hole (see FIG. 2-16) is Lagrangian (La)
The electron beam (16) is circularly focused by the (Grange) law of refraction to be circular. If the circular electron beam (16) emitted from the electron gun reaches the center of the screen of the color picture tube which is not affected by the deflection yoke, the electron beam (16) is focused into a circular shape and the circular beam spot. (17 in FIG. 2) is formed.

In the color picture tube, an image is reproduced by scanning the entire area of the screen with the electron beam (16) emitted from the electron gun by the deflection magnetic field of the deflection yoke. Further, in a color picture tube that emits a plurality of electron beams (16), the deflection magnetic field of the deflection yoke deflects the electron beams (16) and, at the same time, a plurality of electron beams (1
Since 6) must be concentrated (converged) on one fulcrum of the screen, the electron beam (16) is emitted horizontally in-line, and the deflection magnetic field generated by the deflection yoke has different magnetic field strengths in the central portion and the peripheral portion. A self-convergence method that can concentrate on a non-uniform magnetic field is applied.

The R, G, B electron beams (16) are concentrated on the entire screen by the self-focusing magnetic field. In the self-focusing magnetic field, the pincushion magnetic field of the horizontal deflection magnetic field is shown in FIG. 2 (A).
The barrel magnetic field of the vertical deflection magnetic field is shown in FIG.
The pincushion magnetic field and the barrel magnetic field are composed of two-pole and four-pole components, respectively, as shown in FIG. Therefore, the electron beam (16) emitted from the electron gun is mainly deflected by the dipole component in the dotted line direction shown in FIG.
Microscopically, the quadrupole component causes a magnetic force in the arrow direction to diffuse in the horizontal direction (pincushion magnetic field) and a focusing force in the vertical direction (barrel magnetic field). As a result, astigmatism is generated in the beam spot (17 in FIG. 2) in the peripheral portion of the picture tube screen, so that the image planes of the electron beam (16) are different from each other in the vertical and horizontal directions. Therefore,
The beam spot (17) is vertically overfocused on the fluorescent screen, which deteriorates the vertical resolution of the color picture tube.

Further, in the development in which the electron beam (16) is laterally elongated by the non-uniform deflection magnetic field as described above, the intensity of the non-uniform magnetic field becomes stronger toward the peripheral portion of the screen, so that it is deflected to the peripheral portion of the screen and more remarkable. However, as shown in FIG. 4, the electron beam (41) having a vertical cross section is accelerated and focused by the free focus lens (30, 31, 32) and the main electrostatic focusing lens (36) to generate a vertical deflection magnetic field. It is focused by the lens (38).

The electron beam (40) having a horizontal cross section is accelerated and focused by the free focus lens (30, 31, 32) and the main electrostatic focusing lens (36), and is diverged by the lens (39) by the horizontal deflection magnetic field. , The core (18) becomes thinner with the beam spot (17) appearing on the screen as it goes to the periphery of the screen of the color picture tube.
The shade or halo (19) becomes large, greatly reducing the resolution of the color picture tube.

As described above, in order to remove the horizontally elongated core (18) formed thinly in the peripheral portion of the color picture tube and the halo (19) having a low electron density generated above and below the core, the main electrostatic charge of the electron gun is removed. In order to make the electron beam (16) oblong in advance before entering the focusing lens and make the electron beam (16) incident on the deflection region into oblong by passing through the circular axisymmetric lens of the main electrostatic lens. A laterally long electron beam passage hole was formed in the second grid (12) to correct astigmatism due to a non-uniform magnetic field.

However, in such a conventional electron gun for a color picture tube, since the beam spot at the center of the screen is not affected by the magnetic field, the vertically elongated electron beam emitted from the electron gun appears as it is, and the image quality at the center of the screen of the color picture tube is displayed. There is a problem that the characteristics are deteriorated, and the halo component corresponding to the difference between the focus locus and the screen cannot be completely removed even in the peripheral part of the screen.

That is, a screen of an electron gun for a color picture tube having an electron beam passage hole having a circular axis symmetry. As shown in FIG. 13 (A) showing the shape of a beam spot at each position, a screen not affected by a non-uniform magnetic field. The central part is formed only on the circular core (18), but the core (18) is thin in the peripheral part of the screen affected by the non-uniform magnetic field, and the wide halo (19) is formed on the upper and lower parts. You can see that it has been diffused. Further, as can be seen from FIG. 13B showing the beam spot shape of the electron gun for a color picture tube in which the horizontally long non-circular electron beam passage hole is installed in the electron beam forming unit (BFR), the core (18 ) Above and below (1
9), the improvement has been made, but it can be seen that a vertically elongated core (18) is formed in the central portion of the screen.

An object of the present invention is to form a dynamic focus lens field which changes depending on the deflection amount of an electron beam deflected by a deflection yoke of a color picture tube, and to obtain a good color image over the entire screen area of the color picture tube. To provide an electron gun for tubes.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plurality of cathodes and a static electrode in order to make the electron beam emitted from the cathodes have different vertical and horizontal electron beam focusing and diverging degrees. A voltage lower than the static focus voltage is installed between the electrode that applies the focus voltage and the electrode that applies the dynamic focus voltage that changes depending on the increase or decrease of the deflection current of the deflection yoke, and the facing surface of the static focus electrode and the dynamic focus electrode. The present invention is achieved by an electron gun for a color picture tube, comprising: a front end auxiliary focusing lens field having one or more electrodes to be applied; and a main electrostatic focusing lens field sequentially arranged in the tube axis direction.

[0015]

FIG. 5 is a sectional view of an electron gun for a color picture tube of the present invention, showing a cathode (10), first to fourth grid electrodes (11, 12, 23, 24), and a first accelerating / focusing electrode ( 25) and the second acceleration / focusing electrode (26) are sequentially arranged in the tube axis direction of the picture tube.

FIG. 12 is a schematic view of the electron optics field for explaining the deformation of the electron beam spot shape according to the present invention, in which the electron beam forming section (cathode (10), first and second grid electrodes (11) and (12)) is formed. 30) and (31) for focusing the electron beam (16) at a certain distance (1) from the cathode (10), and lower electrodes of the second grid electrode (12) and the third grid electrode (23). Focusing of the electron beam (16) on the horizontal width (X-X) and the vertical width (Y-Y) in order to improve the focusing effect in the peripheral portion of the screen of the electron beam (16) between the (23a) and (23a). And a free-focus lens (32, 33) having different divergence effects, and is configured as an upper electrode (23b) of the third grid electrode (23), a fourth grid electrode (24), and an accelerating / focusing electrode (25). The lower electrode (25a) of the Constitutes a focusing lens (34, 35), the upper electrode of the first accelerating / focusing electrode (25) (25
b) and the second accelerating / focusing electrode (26) form the main electrostatic focusing lens (36, 37).

The operation and effect of the thus configured electron gun for a color picture tube according to the present invention will be described in detail with reference to FIGS. 6 to 13. First, as shown in FIG. 5, a constant focusing voltage (Vs) is applied to the third grid electrode (23) by a DC power source.
f) is applied, and a constant DC focusing voltage (Vsf) is superimposed on the first accelerating / focusing electrode (25) with a voltage (V) that changes proportionally with the amount of deflection of the electron beam (16) on the screen. A dynamic focusing voltage (Vdf) is applied. A fourth grid electrode positioned between the third grid electrode (23) to which the static focus voltage (Vsf) is applied and the first acceleration / focusing electrode (25) to which the dynamic focus voltage (Vdf) is applied. The same low voltage Ed2 as the voltage applied to the second grid electrode (12) is applied to (24). A front end auxiliary focusing lens (3) configured as an upper electrode (23b) of the third grid electrode (23), a fourth grid electrode (24), and a lower electrode (25a) of the first acceleration / focusing electrode (25).
4, 35), when only a static focus voltage (Vsf) having a constant focusing voltage is applied by the DC power supply,
As shown in (A), the horizontal width (XX) and the vertical width (Y-
The focusing and diverging actions of the electron beam (16) in Y) are almost the same.

Therefore, the beam spot (1
7) obtains an almost circular shape. Front end auxiliary focusing lens (3
4, 35) constituting the third and fourth grid electrodes (23,
24) and the first accelerating / focusing electrode (25) at the same time constitutes the main electrostatic focusing lens (36, 37), and the AC voltage source proportional to the first accelerating / focusing electrode (25) is changed by the deflection amount by the deflection yoke. (V) is the static focus voltage (Vs
When the dynamic focus voltage (Vdf) superimposed on f) is applied, the focusing and diverging actions of the electron beam in the horizontal width (XX) and the vertical width (YY) are different as shown in FIG. 12B. . That is, there is almost no divergence of the electron beam in the horizontal width (XX) and the divergence region is large in the vertical width (YY), so that the main electrostatic focusing lens (3
The vertical width (Y-) of the deflection magnetic field (38, 39) generated by the deflection yoke by lengthening the electron beam that has passed through 7).
The focusing effect on Y) and the diverging effect on the horizontal width (XX) are mutually compensated. Therefore, the beam spot (1
7) The shape is almost the same as the central portion of the screen as shown in FIG. 13C, and the image quality on the entire screen can be improved.

FIG. 6 shows another embodiment of the present invention in which a constant voltage (Vsf) is applied to the first accelerating / focusing electrode (25) and the first accelerating electrode is applied to the third grid electrode (23). / A dynamic focus voltage (Vdf) in which an AC voltage source (V) is superimposed on a constant voltage (Vrf) applied to the focusing electrode (25) is applied. A low voltage (Ec2) having the same potential is applied to the fourth grid electrode (24) and the second grid electrode (12), and the operation is the same as the operation of FIG. 5 described above.

FIG. 7 shows another embodiment of the present invention, in which the voltage application method is the same as that of FIG. 5, and the third grid electrode (2
The astigmatism correction electrode Q1 is disposed on the lower electrode (23a) of 3), and the lower electrode (25) of the first acceleration / focusing electrode (25) is
This is a configuration in which the astigmatism correction electrode Qc is provided in a). The operation of the astigmatism correction electrodes (Qa) (Qc) is shown in FIG.
As shown in (A), when the static focus voltage (Vsf) and the dynamic focus voltage (Vdf) are the same, immediately when the deflection current of the deflection yoke (D, Y) is "0", the beam The spot (17) is located at the center of the screen. At this time, the focusing action of the front end auxiliary focusing lens (34) is horizontal (X
-X) and the vertical width (Y-Y) have almost the same focusing / diverging action, and the beam spot (17) in the central portion of the screen has a substantially circular shape, as shown in FIG. 12 (B). To the first acceleration / focusing electrode (25) provided with the astigmatism correction electrode (Qc) by applying a dynamic focusing voltage (Vdf) that changes with an increase or decrease in the deflection current of the deflection yoke (D, Y) to ), The front end auxiliary focusing lens (35) formed between the lower electrode (25a) and the upper electrode (24b) of the opposing fourth grid electrode (24) has a vertical width (Y
The divergence region of the electron beam is increased in −Y) so that the horizontal width (XX) does not change.

As a result, the deflection magnetic field (3) generated by the deflection yoke (D, Y) is obtained by lengthening the electron beam (16) passing through the main electrostatic focusing lens (37).
(8, 39) focusing on the vertical width (YY) and diverging on the horizontal width (XX) are mutually compensated, and the beam spot (17) shape is almost the same as the central part of the screen in the peripheral part of the screen. By doing so, the image quality on the entire screen is improved. When the dynamic focus voltage (Vdf) is applied, the halo (19) generated in the peripheral portion of the screen can be removed by compensating for the difference in focal length between the central portion of the screen and the peripheral portion of the screen.

FIG. 8 shows another embodiment of the present invention, in which the voltage application method is the same as in FIGS. 5 and 7, and the upper and lower electrodes (24b, 24a) of the fourth grid electrode (24) are respectively formed. This is a form in which astigmatism correction electrodes (Qb, Qb ') are provided.
FIG. 9 shows another embodiment of the present invention, the method of applying a voltage is the same as in FIGS. 5, 7, and 8, and the upper electrode (23b) of the third grid electrode (23) is astigmatized. The aberration correction electrode (Qb ') is provided, and the astigmatism correction electrode (Qc) is provided on the lower electrode (25a) of the first acceleration / focusing electrode (25).

FIG. 10 is a schematic diagram of the astigmatism correction electrode. (10A) is Wa / Ha ≦ 0.4, and (10A) is
B) is Wa ′ / Ha ′ ≧ 1.0, and (10C) is W
b / Hb ≧ 1.0, and (10D) is Wb ′ / Hb ′.
≧ 1.24, and (10E) is Wc / Hc ≧ 1.0,
t ₁ > t ₂ and (10F) is Wc ′ / Hc ′ ≧ 1.
25, t ₁ > t ₂ . FIG. 11 shows the respective characteristics of the astigmatism correction electrode, and shows ⊚: excellent, ◯: excellent, Δ: normal, ×: defective in the remarks column.

[0024]

As described in detail above, according to the present invention, the vertically long focal length and the horizontal width (XX) have different focal lengths due to the increase or decrease of the deflection current amount of the deflection yoke. An electron beam can be formed, and a circular beam spot can be formed in the peripheral area of the screen by compensating for the oblong beam spot shape by the non-uniform deflection magnetic field of the deflection yoke. Can be prevented from deteriorating.

Further, the development in which the distance difference between the electron beam focus locus and the screen of the color cathode ray tube becomes larger toward the peripheral portion of the screen is increased by increasing the dynamic focusing voltage (Vdf) to lengthen the focus of the main electrostatic lens. The locus can be matched with the screen of the color picture tube, and a good resolution can be obtained in the entire area of the screen of the color picture tube.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional electron gun for a color picture tube.

FIG. 2 is an explanatory diagram of a relationship between an electron beam spot and a self-focusing magnetic field in FIG.

FIG. 3 is an explanatory diagram for explaining a relationship between an electron beam spot and a magnetic field in FIG.

FIG. 4 is a schematic view of an electron optical field for explaining a modification of the electron beam spot shape in FIG.

FIG. 5 is a sectional view of the electron gun for a color picture tube of the present invention.

FIG. 6 is a sectional view (No. 1) showing another embodiment of the electron gun for color picture tubes of the present invention.

FIG. 7 is a sectional view (No. 2) showing another embodiment of the electron gun for color picture tubes of the present invention.

FIG. 8 is a sectional view (3) showing another embodiment of the electron gun for color picture tubes of the present invention.

FIG. 9 is a sectional view (No. 4) showing another embodiment of the electron gun for color picture tubes of the present invention.

FIG. 10 is a schematic view (A to F) showing an electron gun astigmatism correction electrode according to the present invention.

11 is an explanatory view of a combination of installation of astigmatism correction electrodes of FIG.

FIG. 12 is a schematic view of an electron optical field for explaining a modification of the electron beam spot shape according to the present invention.

FIG. 13 is an electron beam spot shape diagram for each part appearing in a color picture tube according to the related art and the present invention, (A)
FIG. 3A is a conventional electron beam spot shape diagram, FIG. 3B is an electron beam spot shape diagram having a non-axisymmetric electron beam passage hole, and FIG. 3C is an electron beam spot shape diagram of the present invention.

[Explanation of symbols]

 11, 12, 23, 24 ... Grid electrode 15 ... Shielding electrode 16 ... Electron beam 17 ... Beam spot 18 ... Core 19 ... Halo 30, 31 ... Electron beam forming unit 34, 35 ... Focusing lens 36, 37 ... Main electrostatic focusing lens

Claims (11)

[Claims] 1. A plurality of cathodes, an electrode for applying a static focus voltage to make electron beam emitted from the cathodes have different vertical and horizontal electron beam focusing and divergence levels, and deflection. An electrode that applies a dynamic focus voltage that changes depending on an increase or decrease in the deflection current of the yoke, and one or more electrodes that are provided between the facing surfaces of the static focus electrode and the dynamic focus electrode and that apply a voltage lower than the static focus voltage. An electron gun for a color picture tube, comprising: a front end auxiliary focusing lens field having: and a main electrostatic focusing lens field sequentially arranged in a tube axis direction. 2. The front end auxiliary focusing lens field is characterized in that a static focus voltage is applied to an electrode close to a cathode and a dynamic focus voltage is applied to an electrode which also constitutes a main electrostatic focusing lens field. An electron gun for a color picture tube according to claim 1. 3. The front end auxiliary focusing lens field is characterized in that a dynamic focus voltage is applied to an electrode close to a cathode and a static focus voltage is applied to an electrode which also constitutes a main electrostatic lens field. Item 1. An electron gun for a color picture tube according to item 1. 4. A static focus electrode which is composed of a plurality of cathodes and three or more electrodes and which applies a static focus voltage, and a dynamic focus electrode which applies a dynamic focus voltage that changes according to an increase or decrease in the deflection current of the deflection amount. When the dynamic focus voltage is the same as the static focus voltage, the focus action in the specific direction and the focus action in the direction orthogonal to the direction are configured to be substantially the same, and it is specified that the dynamic focus voltage is different from the static focus voltage. An electron gun for a color picture tube, comprising: a front end auxiliary focusing lens field for making a focusing action in a direction different from a focusing action in a direction orthogonal to the above direction; and a main electrostatic focusing lens field. 5. The astigmatism correction electrode is further provided, which forms a rotationally asymmetric front end auxiliary focusing lens when the static focus voltage and the dynamic focus voltage of the front end auxiliary focusing lens field are different. Electron gun for color picture tube described. 6. The astigmatism correction electrode has a horizontal width (XX) or a vertical width (YY) surrounding each of the electron beam passage holes on one plane of the electrode forming the front end auxiliary focusing lens field. The electron gun for a color picture tube according to claim 5, further comprising one or more plate-shaped electrodes having linearly continuous polygonal holes. 7. The astigmatism correction electrode has a polygonal hole linearly continuous in a horizontal width (XX) surrounding each electron beam passage hole on one plane of the electrode forming the front end auxiliary focusing lens field. The electron gun for a color picture tube according to claim 5, further comprising at least one plate-shaped electrode body having the plate-shaped electrode body. 8. The astigmatism correction electrode has a polygon continuous in a vertical width (Y-Y) surrounding each of the electron beam passage holes on a plane of a constituent electrode of the front end auxiliary focusing lens field near the cathode. A plate-shaped electrode body having a hole is provided, and a horizontal width (XX) surrounding each of the electron beam passage holes is linearly continuous on the plane of the low-potential electrode facing surface of the electrode that also constitutes the main electrostatic lens field. An electron gun for a color picture tube according to claim 5, further comprising a plate-shaped electrode body having the formed polygonal holes. 9. A polygonal hole of a plate-shaped electrode body provided on a plane of a facing surface and a low-potential electrode of the electrode that also constitutes the main electrostatic lens field is the sum of thicknesses of cross sections parallel to the horizontal direction. (Σt
9. The electron gun for a color picture tube according to claim 8, wherein 1) is larger than a sum (Σt2) of thicknesses of cross sections parallel to the direction orthogonal to the direction. 10. The astigmatism correction electrode is a low voltage application electrode that constitutes a front end auxiliary focusing lens field, and is linear in a vertical width (Y-Y) surrounding each electron beam on an electrode plane near the cathode. A plate-like electrode body having continuous polygonal holes, and having a polygonal hole linearly continuous in a horizontal width (XX) surrounding each electron beam on an electrode plane close to the main electrostatic lens The electron gun for a color picture tube according to claim 5, further comprising an electrode body. 11. The plate-shaped electrode body has a sum of thicknesses of cross sections parallel to a direction orthogonal to the direction smaller than a sum of thicknesses of parallel cross sections of a polygonal hole surrounding each electron beam passage hole in a specific direction. The electron gun for a color picture tube according to claim 10.