JPH0388242A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a good resolution for the whole range of a phosphor screen by applying a dynamic voltage of a small amplitude by composing a fourth grid from a first to a third electrode element disposed in the direction from a third grid to a fifth grid in order. CONSTITUTION:A third to a fifth grid G3-G5 are composed, and a voltage is applied to each of them, so a rotation asymmetric lens is formed between the third grid G3 and a first electrode element G41 of the fourth grid G4 and between the fifth grid G5 and a third electrode element G43 of the fourth grid G4. In the meanwhile, a rotation asymmetric lens is formed between the first to third electrode elements G41-G43 of the fourth grid G4, so these rotation asymmetric lenses offset actions applied on a sectional form of an electron beam. A resolution at the peripheral parts of a phosphor screen can thus be improved largely using a dynamic voltage of a small amplitude without increasing the lens magnitude of a main lens system.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention relates to a color cathode ray tube, and in particular to a color cathode ray tube that improves its electron gun and provides high resolution over the entire phosphor screen. Regarding.

(Prior Art) The mainstream of color cathode ray tubes is the so-called in-line electron gun system, which has an electron gun that emits three parallel electron beams on the same horizontal plane. The cause of the deterioration of the resolution characteristics of this in-line electron gun color cathode ray tube is deflection aberration, which causes the beam spot on the phosphor screen to become larger when the electron beam is deflected from the center of the phosphor screen to the periphery. .

This deflection aberration consists of a superposition of the following two different deflection aberrations.

One is that the trajectory of the electron beam from the electron gun to the phosphor screen increases as the deflection of the electron beam increases, so a small diameter and perfectly circular beam spot can be obtained at the center of the phosphor screen. This is a deflection aberration caused by the fact that when the focus voltage is set to , the beam spot becomes overfocused in the peripheral area of the phosphor screen.

The other one is deflection aberration caused by non-uniformity of the deflection magnetic field. That is, in the in-line electron gun type color cathode ray tube, as shown in FIGS. 8(a) and (b),
By making the horizontal deflection magnetic field (1) of the deflection device a vincsion type and the vertical deflection magnetic field (2) a barrel-shaped non-uniform magnetic field, three electron beams (3B), (3G) can be generated.
, Self-convergence (3R). Therefore, the electron beams (3B), (3G), and (3R) that have passed through this non-uniform magnetic field have a long and flat shape in the horizontal direction, and the beam spot, especially around the periphery of the phosphor screen, is distorted into a non-circular shape. Become something.

Because of the overlap of these two deflection aberrations, as shown in FIG. is non-circular, consisting of a high-luminance core portion (8a) and a low-luminance halo portion (8b), and the resolution in the peripheral portion of the phosphor screen (5) is significantly degraded.

As a means of purifying the beam spot in the peripheral area of the phosphor screen, Japanese Patent Application Laid-Open No. 61-99249 discloses
Regarding the pi-potential type electron gun, its focusing electrode is
The electron beam passing holes on the opposing surfaces of the two focusing electrodes are formed into a rectangle whose long axes are perpendicular to each other, and a constant voltage is applied to one focusing electrode, and the electron beam is applied to the other focusing electrode. A dynamic voltage that changes depending on the amount of deflection of the electron beam is applied to form a rotationally non-symmetrical lens when the electron beam is deflected, and at the same time, the strength of the main lens is weakened, thereby compensating for deflection aberration.

However, this measure requires a constant focusing voltage on one electrode,
A high voltage that is a dynamic voltage superimposed on the focusing voltage is applied to the other electrode, and this high voltage must be supplied from the base pin, so a special base and socket of the color cathode ray tube are required. Become.

In addition, as another means, Japanese Patent Laid-Open No. 81-74248 and Japanese Patent Laid-Open No. 63-143725 disclose a quidra potential type electron gun in which the fourth grid is composed of three electrode elements, and the fourth grid is composed of three electrode elements, and a second electrode element located at;
Alternatively, there is one that compensates for deflection aberration by applying a dynamic voltage to the first and third electrode elements and applying a constant voltage to the other electrode elements to form a rotationally asymmetric lens between the three electrode elements. It is shown.

This method has the advantage that a special base and socket are not required, since the constant voltage and dynamic voltage applied to the electrode elements are low DC voltages. but,
In order to make the strength of the non-rotationally symmetrical lens formed between the electrode elements sufficient with a low amplitude dynamic link voltage, the length of each electrode element must be increased or the diameter of the electron beam passage hole of each electrode element must be increased. It needs to be made smaller. This increases the strength of the unipotential lens formed between the third grid and the fifth grid, and the lens magnification of the main lens system formed between the third grid and the sixth grid increases. growing. As a result, the diameter of the beam spot formed on the phosphor screen increases. On the other hand, when the amplitude of the dynamic voltage is increased, the maximum applied voltage becomes larger, and the
Not only is a special base and socket required as in the case of the No. 249 publication, but also compensation for the withstand voltage characteristics of the cathode ray tube is required. Furthermore, the cost of the circuit that generates the dynamic voltage increases.

(Problems to be Solved by the Invention) As described above, in order to improve the resolution over the entire phosphor screen of an in-line electron gun type color cathode ray tube, the electron gun is a quadra potential type electron gun, and The fourth grid is composed of three electrode elements,
Some attempts have been made to improve the resolution, especially around the periphery of the phosphor screen, by applying appropriate voltages to each electrode element. However, in order to sufficiently improve the resolution of the periphery of the phosphor screen using this conventional electron gun, a dynamic voltage with a large amplitude is required, or the lens magnification of the main lens system is increased. There are problems such as the beam spot becomes large and the resolution becomes insufficient.

This invention was made to solve the above problems, and it is possible to obtain good resolution over the entire phosphor screen by applying a dynamic voltage with a small amplitude in an in-line electron gun type color cathode ray tube. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) An electron gun is provided that emits three parallel electron beams on the same plane including the tube axis, and the electron gun is directed along the tube axis toward the phosphor screen. In a color cathode ray tube comprising at least an array of cathodes and first to sixth grids, the fourth grid is composed of eleventh second and third electrode elements arranged sequentially in the direction from the third grid to the fifth grid. , a circular electron beam passing hole is formed in the first and third i1 pole elements, a long electron beam passing hole is formed in the 21st pole element in the direction in which the three electron beams are arranged, and a constant hole is formed in the first and third electrode elements. A constant voltage lower than the voltages of the first and third electrode elements is applied to the second f1 pole element, and the opposing surface of the third grid facing the first electrode element and the third grid facing the third electrode element are A groove with an electron beam passing hole at the bottom is formed on the opposing surface of the 5 grids, and the longitudinal direction is the arrangement direction of the 3 electron beams.
The structure was designed to apply a voltage that increases as the deflection of the electron beam increases.

(Function) As described above, when the third to fifth grids are configured and the above voltage is applied to each of them, the third grid and the fourth grid are
A non-rotationally symmetric lens is formed between the first electrode element of the grid and between the fifth grid and the third electrode element of the fourth grid, while the lens is formed between the first to third electrode elements of the fourth grid. Also, non-rotationally symmetric lenses are formed, and each of these non-rotationally symmetric lenses can be made to cancel the effect on the cross-sectional shape of the electron beam. The voltage can significantly improve the resolution around the phosphor screen.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings.

FIG. 4 shows the overall configuration of a color cathode ray tube, which is one embodiment of the present invention. This color cathode ray tube consists of a panel <lO> and a funnel (lO) integrally joined to this panel (lO).
A phosphor screen (12) consisting of a three-color phosphor layer emitting light in blue, green, and red is formed on the inner surface of the panel (1).
A shadow mask (13) with a large number of electron beam passing holes formed inside thereof, facing the mask (12) and spaced apart from it by a predetermined distance.
is installed. Also, in the neck (14) of the funnel (11), 3 electron beams (15B), (15G),
The following electron gun (1G) that emits (15R) is installed. Three electron beams (15B), (15G), (15R) are emitted from this electron gun (16).
the deflection device (1) attached to the outside of the funnel (11).
The phosphor screen (12) is deflected horizontally and vertically by the binction type horizontal deflection magnetic field and the barrel type vertical deflection magnetic field of 7), and is scanned by scanning the phosphor screen (12>) through the shadow mask (13>). It is formed into a structure that displays a color image on top.

The electron gun (1B) emits three electron beams (15B).
), (15G), and (15R) are arranged in parallel on the same horizontal plane including the tube axis (Z-axis), and as shown in FIG. 3 cathodes (K)
It is configured in a quidra potential shape consisting of the first to sixth grids (Gl) to (G6) of an integrated structure arranged sequentially on the front surface (in the direction of the phosphor screen), and the fourth grid (G4) or the third grid Grid (G3) to 5th grid (
The first, second, and third electrode elements (041), (G42), and (G43) of integral structure are sequentially arranged in the C5> direction.
). Each electrode element (G41) of the grid of this electron gun (16>) and the fourth grid (G4)
, (G42).

(043), three electron beam passing holes (19) of a predetermined size are formed in parallel in the horizontal direction (X-axis direction) (the direction in which the three electron beams are arranged). This electron beam passage hole (19) is circular except for the second electrode element (G42) of the fourth grid (G4), which will be described later.

In this electron gun (16), there are sub-lenses between the third, fourth and fifth grids (G3), (G4) and (G5), and between the fifth and sixth grids (G5), (
A main lens is formed between G8), and these lenses focus three electron beams emitted from each cathode (K) and irradiate the phosphor screen.

Furthermore, in this electron gun (16), the fourth grid (G4
The third grid (G41) facing the first electrode element (G41)
G3〉 opposing surface (20a), and the third electrode element (G
43) of the fifth grid (G5) facing the opposite surface (20
b), as shown in Fig. 2, grooves (21) whose longitudinal direction is in the horizontal direction are formed, and three electron beam passage holes (19) are formed at the bottom of these grooves (21). .

Furthermore, as described above, the electron beam passing holes (19) of the first and third electrode elements (G41) and (G43) of the fourth grid (G4) are similar to the electron beam passing holes (19) of the other grids (
19), but as shown in FIG. 3, the electron beam passage hole (19a) of the second electrode element (G42) is formed in a non-circular shape with the long axis in the horizontal direction. has been done.

The following voltage is applied to this electron gun (16) during operation. That is, 50-150V to each cathode (K).

OV1 to the first grid (G1), 800 to 800V (Vc2) to the second grid (G2), 6th grid (G
6) t,: 25 to 27 kV, the first and third electrode elements (G41) of the fourth grid (C4), the second to (G43)
600-800V (Vc2) same as grid (G2)
), 0 to 200V (V
c4), third and fifth grids (G3).

A dynamic voltage (24) that changes in synchronization with the deflection current (23) shown in FIG. 5 is applied to (G5).

When such a voltage is applied to each electrode of the electron gun (16), the voltage between the first electrode element (G41) of the third grid (G3) and the fourth grid (G4) and the fourth grid (
G4) third electrode element (G43) and fifth grid (G5
) A non-rotationally symmetric lens is formed between the two. Both of these non-rotationally symmetric lenses are indicated by the arrow (23a) in Fig. 6(a).
, (24a), gives each electron beam a strong focusing effect in the horizontal direction (X-axis direction) and a slightly weaker focusing effect in the vertical direction (Y-axis direction). Therefore, the cross-sectional shape of the electron beam passing through this non-rotationally symmetric lens (25)
has a vertically long shape. On the other hand, the fourth grid (
G4) first to third electrode elements (G41) to (G43)
A non-rotationally symmetric lens is also formed between them. However, this non-rotationally symmetric lens is indicated by the arrow (23b) in FIG.
, (24b), a diverging effect is applied to each electron beam in the horizontal direction, and a focusing effect is applied to the vertical direction. Therefore, the cross-sectional shape (25) of the electron beam that has passed through this non-rotationally symmetrical lens is elongated in the horizontal direction.

By the way, as shown in FIG. 5, the dynamic voltage (24) applied to the third and fifth grids (G3) and (C5) deflects the electron beam when the deflection current (23) is zero. If not, it is VR. Therefore, in this case, the second electrode element (G
42), if the voltage Vc4 applied to the fourth
First to third electrode elements (G41) of grid (G4)
(043) Due to the action of making the electron beam of the non-rotationally symmetrical lens formed between the horizontally long cross-sectional shape (25〉),
Between the electrode element (G41) and the fourth grid (G4)
The effect of the non-rotationally symmetrical lens formed between the third electrode element (G43) and the fifth grid (G5), which makes the electron beam have a vertically long cross-sectional shape (25), is canceled out.
The cross-sectional shape of the electron beam incident on the rotationally symmetrical main lens formed between the grid (G5) and the sixth grid (G6) can be made circular. As a result, this electron beam having a circular cross-sectional shape is focused by the rotationally symmetrical main lens to form a perfectly circular beam spot on the phosphor screen.

On the other hand, when the electron beam is deflected, the dynamic voltage (24) shown in FIG. 5 is higher than vf and increases as the deflection increases.
and the first electrode element (G41) of the fourth grid (G4), and the third electrode element (G4) of the fourth grid (G4).
3) and the fifth grid (G5) are both strengthened. Therefore, the cross-sectional shape (25
) is further strengthened to make it vertically long. This effect cancels out the effect of shaping the electron beam into a horizontally elongated cross-sectional shape due to the nonuniform magnetic field consisting of the binction type horizontal deflection magnetic field and the barrel type vertical deflection magnetic field of the deflection device.

Furthermore, the increase in the dynamic voltage (24)
The potential difference between the grid (G5) and the sixth grid (G6) is reduced to weaken the focusing effect of the main lens formed between these grids (05) and (GO).
Compensates for overfocus caused by deflection of the electron beam. In this case, the increase in the dynamic voltage (24) causes the third grid (G3) to the fifth grid (G
The sub-lens formed during step 5) is strengthened to prevent the effect of strengthening the focusing effect of the main lens, but this compensating effect can be made as large as necessary and sufficient since the main lens has a strong strength.

Therefore, according to this electron gun (1B), the deflection aberration at the periphery of the phosphor screen (12) is sufficiently removed to minimize the beam spot, and the resolution at the periphery of the phosphor screen (12) is greatly improved. In this case, the third grid (G3) and the fourth grid (G4)
between the first electrode element (041) of the fourth grid (G4>) and the third electrode element (G43) of the fourth grid (G4>) and the fifth grid (G4).
5) The strength of the lens action that makes the electron beam a long cross-sectional shape in the vertical direction of the non-rotationally symmetrical lens formed between
It depends on the width W and depth D of the grooves (21) formed in the third and fifth grids (G3) and (05). However, this third and fifth grid (G3), (G5)
The strength of the sub-lens formed between this groove (21)
does not depend much on the width W and depth D of. therefore,
By appropriately setting the width W and depth D of the groove (21), deflection aberration caused by a non-uniform magnetic field can be avoided without increasing the amplitude Vd of the dynamic voltage (24) or increasing the strength of the sub-lens. can be adequately compensated for.

Therefore, the dynamic voltage (24
), a uniform and small beam spot can be obtained over the entire area of the phosphor screen (12), and the resolution over the entire area of the phosphor screen (12>) can be improved.

According to experiments, when the width W of the grooves formed in the third and fifth grids was set to 6.5 mm, and the depth D was set to 0.8 mm, an electron beam was applied to the diagonal periphery of the phosphor screen. The amplitude Vd of the dynamic voltage when deflecting could be set to about 200V.

This value is equivalent to normal dynamic focus, without increasing the cost of the circuit that generates the dynamic voltage, and with the only high voltage supplied from the base pin of the color cathode ray tube, requiring a special base and socket. no longer needed.

In the above embodiment, three non-circular electron beam passing holes with long sleeves in the horizontal direction were formed in the second electrode element of the fourth grid in correspondence with three electron beams, but as shown in FIG. , the electron beam passing hole (G42) of this second electrode element (G42)
X9a) may be one non-circular hole whose major axis is in the horizontal direction.

Further, in the above embodiment, the first and third grids of the fourth grid
[! Although the voltage Vc2 applied to the i-element is the same, the voltages applied to the first and third electrode elements are not limited to this, and even if different constant voltages are applied to each, the same result can be obtained. effect can be obtained.

Effects of the Invention The electron gun has an electron gun that emits three parallel electron beams on the same plane including the tube axis, and this electron gun has at least a cathode arranged in the direction of the phosphor screen along the tube axis, and In a color cathode ray tube consisting of a sixth grid, the fourth grid is composed of first, second, and third electrode elements arranged sequentially in the direction from the third grid to the fifth grid, and the first and third electrodes are arranged sequentially in the direction from the third grid to the fifth grid. A circular electron beam passage hole is placed in the element.
A long electron beam passage hole is formed in the second electrode element in the direction in which the three electron beams are arranged, and a constant voltage is applied to the first and third electrode elements, and the voltage of the first and third electrode elements is applied to the second electrode element. By applying a constant voltage lower than If the structure is such that a groove having a passage hole at the bottom is formed and a voltage is applied that increases as the deflection of the three electron beams increases, the groove between the first electrode element of the third grid and the fourth grid and the fifth A non-rotationally symmetric lens is formed between the grid and the third electrode element of the fourth grid, and a non-rotationally symmetric lens is also formed between the first to third electrode elements of the fourth grid. The fifth and sixth symmetrical lenses can each cancel out the effect on the cross-sectional shape of the electron beam.
Without increasing the lens magnification of the main lens system formed by the grid, a dynamic voltage with a small amplitude can eliminate deflection aberrations and provide a color cathode ray tube with good resolution over the entire phosphor screen.

[Brief explanation of drawings]

1 to 7 are detailed explanatory diagrams of the present invention, in which FIG. 1 is a perspective view of an electron gun of a color cathode ray tube, which is an embodiment of the invention, and FIGS. A plan view showing the structure of the first and third electrode elements of the fourth grid and a cross-sectional view thereof taken along the line ■-■.
! FIG. 4 is a plan view showing the structure of the pole element, FIG. 4 is a sectional view showing the structure of a color cathode ray tube as an example, and FIG. 5 is a deflection current flowing through the deflection device and the dynamic voltage applied to the third and fifth grids. Figures 6(a) and 6(b) show the relationship between the first and second grids of the third and fourth grids, respectively.
between the electrode element or the 31st ! of the 5th grid and the 4th grid! Explaining the effect that the non-rotationally symmetrical lens formed between the pole element has on the electron beam, and the effect that the non-rotationally symmetrical lens formed between the first to third electrode elements of the fourth grid has on the electron beam. Figure 7 is the 4th diagram for
Plan views showing different structures of the second electrode elements of the grid, FIGS. 8(a) and 8(b) illustrate the influence of the horizontal deflection magnetic field of the deflection device on the electron beam and the influence of the vertical deflection magnetic field on the electron beam, respectively. FIG. 9 is a diagram showing the shape of a beam spot on a phosphor screen of a conventional color cathode ray tube. 12...phosphor screens 15B, 15G, 15R...3? ! Child beam 16・
...electron gun 17...deflection device 19...
Circular electron beam passage hole 19a...Non-circular electron beam passage hole 21...Groove
Gl...First grid G2...Second grid G3...Third grid G4...Fourth grid G5...Fifth grid G6...Sixth grid G41...First electrode element 042... Second electrode element 043... Third electrode element K... Cathode

Claims (1)

[Scope of Claim] The electron gun has an electron gun that emits three parallel electron beams on the same plane including the tube axis, and this electron gun has at least a cathode and a first electron beam arranged along the tube axis in the direction of the phosphor screen. In a color cathode ray tube, which displays an image on the phosphor screen by deflecting three electron beams emitted from the electron gun in horizontal and vertical directions by a deflection device, the fourth grid is Consisting of first, second, and third electrode elements arranged sequentially in the direction from the third grid to the fifth grid, and circular electron beam passing holes are formed in the first and third electrode elements of the fourth grid. A long electron beam passage hole is formed in the second electrode element in the direction in which the three electron beams are arranged, a constant voltage is applied to the first and third electrode elements, and a constant voltage is applied to the second electrode element. A constant voltage lower than the voltage of the first and third electrode elements is applied,
The opposing surface of the third grid facing the first electrode element of the fourth grid and the opposing surface of the fifth grid facing the third electrode element are provided with electron beams with the longitudinal direction of the arrangement direction of the three electron beams. A color cathode ray tube characterized in that a groove having a passage hole at the bottom is formed, and a voltage that increases as the deflection of the three electron beams increases is applied to the third and fifth grids.