JPH08203446A - Inline-type cathode-ray tube - Google Patents

Abstract

PURPOSE: To improve a moire produced in both side parts of a screen in a low brightness region of a cathode-ray tube without deteriorating the focusing function from an average current region of electron beam to a high brightness region. CONSTITUTION: The ratio t/d of the thickness (t) of an accelerating electrode 2 of a tripole composed of a cathode 6, a control electrode 1, and the accelerating electrode 2 and the diameter (d) of an electron beam passing hole 2a formed in the accelerating electrode 2 is set to be within a range, 0.3<=t/d<=0.65.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun of an in-line type color cathode ray tube, and more particularly to an electron gun having improved moire characteristics in a low luminance region without deteriorating focus characteristics.

[0002]

2. Description of the Related Art FIG. 8 is a longitudinal sectional view showing a conventional in-line type cathode ray tube. In the figure, 6a, 6b and 6c are cathodes arranged on the same horizontal plane, 17a, 17b and 17c are heaters inserted in the respective cathodes, and 1 is an electron beam passage corresponding to three cathodes 6a, 6b and 6c. Holes 1a, 1
b, 1c has a control electrode, 2 similarly has an acceleration electrode having three electron beam passage holes 2a, 2b, 2c, and 3 has similarly six electron beam passage holes 3a, 3b, 3c, 3d, 3
Focusing electrodes 4 having e, 3f are welded to a shield cup 5 to which a contactor 16 is attached by an anode electrode, and electron beam passage holes 4a, 4b, 4 similar to the other electrodes 1 to 3 are formed.
c. Each electrode is insulated and held by glass (not shown) to form an electron gun. Reference numeral 8 is a stem for applying a potential to each of the electrodes 1 to 3, 9 is a glass envelope, 10 is an external deflection yoke, 11 is an anode button for applying an anode voltage, and 12 is an inner surface of the envelope 9. Attached interior graphite, 13 is a shadow mask placed inside the envelope 9,
Reference numeral 14 is an internal magnetic shield, and 15 is a phosphor coated on the inner surface of the screen.

Next, the operation will be described. Heater 17
Electrons generated from the cathodes 6a, 6b, 6c heated to a predetermined temperature by a, 17b, 17c are generated by the control electrode 1,
A prefocus lens which is formed into an electron beam by the acceleration electrode 2 and is generated between the acceleration electrode 2 and the focusing electrode 3, and an anode electrode 4 to which a high voltage is applied through the anode button 11, the interior graphite 12 and the contactor 16.
Is focused by a main electron lens generated between the focusing electrode 3 and the focusing electrode 3 to form three electron beams 7a, 7b, 7c, which form a spot on the screen. At this time, the three electron beams 7a, 7b, and 7c are color-selected by the shadow mask 13, and the phosphors 15 of the colors defined by the respective electron beams are made to emit light. Usually, the electron beams 7a are red, 7b are green, and 7c are blue electron beams for phosphors.

Electron beam 7 produced by an electron gun
a, 7b, and 7c are 7d and 7 shown in FIG. 8 by the horizontal deflection magnetic field and the vertical deflection magnetic field which the deflection yoke 10 produces.
The fluorescent substance 15 in each part of the screen is made to emit light by being deflected like the three deflected electron beams e and 7f to complete the screen.

Recently, a self-focusing system is adopted in which the three deflected electron beams 7d, 7e and 7f are focused on one point in each part of the screen to reproduce an image without any special circuit correction. Therefore, the magnetic field generated by the deflection yoke 10 is distorted non-uniformly in the horizontal direction as a pinch shape and in the vertical direction as a barrel shape. If no special measures are taken with an electron gun, the spot shape of the electron beam is vertical on both sides of the screen even if a high resolution is obtained by narrowing it to a perfect circle at the center of the screen as shown in FIG. 9A. An overfocused portion (hereinafter referred to as “halo”) occurs in the direction, and the resolution is significantly deteriorated.

For this reason, the electron gun is given an astigmatic effect,
As shown in FIG. 9B, the vertical direction of the electron beam spot in the center of the screen is slightly unconverged (hereinafter referred to as “blooming”) to reduce the halo at the horizontal end and reduce the halo at the center and the end. We are trying to compromise resolution.

Further, the conventional electron gun for cathode ray tube is shown in FIG.
In the electron beam optical model shown in 0, the distance a from the main electron lens to the virtual object point changes depending on the amount of electrons extracted from the cathode (hereinafter referred to as the beam current), and from the main lens to the virtual object point. The distance a changes as shown in FIG. As a result, the optimum focusing electrode voltage (hereinafter referred to as “just focus voltage”) that minimizes the spot diameter at each beam current changes as shown in FIG.
Normally, the just focus voltage is adjusted when the beam current of each electron beam is about 500 to 600 [μA] (hereinafter, referred to as “average current”), so that the beam current is low in a low luminance region (about 10 [μA]). ]) And a high brightness region (about 3000 to 4000 [μA]) where the beam current is large, the voltage (EF1) actually applied is higher than the just focus voltage (EF2).

This state indicates that it is in an unfocused state rather than just focus, that is, the electron beam spot becomes blooming in the low luminance region and the high luminance region. For this reason, the divergence angle θ of the electron beam increases in the high brightness region, and the halo is likely to appear. Therefore, the above phenomenon is convenient in terms of reducing the halo. On the other hand, in the low luminance region, the divergence angle θ is small and the halo is difficult to appear from the beginning, so that the electron beam spot is in a just focus state at the horizontal end due to the above phenomenon, as shown in FIG. 9C.

[0009]

Since the conventional electron gun of the in-line type cathode ray tube is constructed as described above, the focusing characteristics from the average current region to the high brightness region are good without any problem, but low. Since the beam spot diameters on both sides of the screen are too small in the brightness area, streak-shaped moire (bridge mask pitch of shadow mask and interference fringes of scanning lines) occurs as shown in FIG. 13, which deteriorates image quality. There was a point. In particular, recently, with the widespread use of wide-screen televisions with an aspect ratio of 16: 9, the vertical width of the screen can be freely changed. The problem of increasing the bridge pitch of the shadow mask, which is the most inconspicuous moiré pattern from the number of lines, cannot be taken.

The present invention has been made to solve the above-mentioned problems, and like the conventional cathode ray tube, the focusing characteristic from the average current region to the high brightness region is good,
Moreover, it is an object of the present invention to obtain an electron gun of an in-line type cathode ray tube in which moire does not occur on both sides of the screen in a low brightness area.

[0011]

An in-line type cathode ray tube according to the present invention has a plurality of linearly arranged cathodes and a plurality of electron beam passage holes provided so as to face the plurality of cathodes. Control electrode, acceleration electrode, focusing electrode,
In an in-line type cathode ray tube equipped with an electron gun in which the anodes are sequentially arranged at a predetermined interval, a ratio t between a plate thickness t of the electron beam passage hole portion of the acceleration electrode and a hole diameter d of the electron beam passage hole.
/ D is formed so that 0.3 ≦ t / d ≦ 0.65.

Further, a slot is provided on the control electrode side of the accelerating electrode in which the length of the electron beam passage holes in the arrangement direction is longer than that in the perpendicular direction.

Further, the electron beam passage holes of the control electrode are formed to have a shape in which the length of the electron beam passage holes in the arrangement direction is longer than the right angle direction, and the electron beam passage holes are arranged closer to the control electrode acceleration electrode side than the arrangement direction of the electron beam passage holes. Is also provided with a slot having a shape longer in the right-angled direction.

Further, a slot is provided on the accelerating electrode side of the focusing electrode in the direction orthogonal to the arrangement direction of the electron beam passage holes.

[0015]

According to the present invention, the distance from the main electron lens to the virtual object point in the low luminance region is larger than the distance from the main electron lens to the virtual object point in the average current region due to the electron lens characteristics of the electron gun. , The focus state at both ends of the screen in the low brightness area is in the halo direction. Therefore, even if the divergence angle θ of the electron beam is small in the low luminance region, the beam spot state on both sides of the screen becomes halo and the spot diameter becomes large due to the influence of the deflection magnetic field. Therefore, the occurrence of moire on both sides of the screen in the low-luminance region due to excessive narrowing is eliminated.

Further, the slot provided in each electrode can adjust the divergence state of the electron beam, and can improve the deterioration of the resolution on both sides of the screen.

[0017]

【Example】

Example 1. An embodiment of the present invention will be described below. FIG. 1 is a vertical cross-sectional view showing set dimensions of the three-pole portion of the electron gun of the first embodiment, showing only the three-pole portion including the cathode 6a.
In the figure, L1 is the distance between the control electrode 1 and the acceleration electrode 2,
L2 is the distance between the acceleration electrode 2 and the focusing electrode 3, d is the hole diameter of the electron beam passage hole of the acceleration electrode 2, and t is the plate thickness of the electron beam passage hole portion of the acceleration electrode 2.

According to the inventor's analysis and technical research,
It was found that the dimension most affecting the change in the distance from the electron lens to the virtual object point with respect to the beam current is the plate thickness t of the electron beam passage hole of the acceleration electrode 2. This is because the positional relationship between the crossover formed near the control electrode 1 and the acceleration electrode 2 and the prefocus lens formed between the acceleration electrode 2 and the focusing electrode 3 changes depending on the plate thickness t of the control electrode 2. It is thought to be for the reason.

Normally used L1 = 0.1-0.3
mm, L2 = 0.7 to 1.5 mm, d = 0.4 to 0.6
FIG. 2 shows the result of simulating the distance from the main electron lens to the virtual object point with respect to the beam current within the range of 4 mm. The plate thickness t of the electron beam passage hole portion of the conventional accelerating electrode 2 is 0.65 <t / d when normalized by the hole diameter d, and becomes the characteristic shown by the solid line in FIG. Distance a1 from the main electron lens to the virtual object point in the current range
On the other hand, the distance a2 from the main electron lens to the virtual object point in the low current region is a2 <a1.

On the other hand, by setting t / d ≦ 0.65, as shown by the broken line in FIG. 2, the distance a3 from the main electron lens to the virtual object point in the low luminance region is a3> a1.
It turns out that This phenomenon is caused by setting t / d ≦ 0.65, as described above, so that the plate thickness of the electron beam passage hole portion of the acceleration electrode 2 becomes thinner than that of the conventional example, and the acceleration electrode 2 and the focusing electrode 3 are This is because the prefocus formed during the period approaches the crossover.

Next, the above characteristics were confirmed by examining the change of the just focus voltage with respect to the beam current in an actual cathode ray tube. The result is shown in FIG. In the case of 0.65 <t / d in the conventional example, the just focus voltage EF2 in the low luminance region is low as EF2 <EF1 with respect to the just focus voltage EF1 in the average current region as well. In the case of ≤0.65, the just focus voltage EF3 in the low luminance region becomes high as EF3> EF1. At this time, when t / d <0.3, the just focus voltage becomes higher in the high-brightness region than 0.65 <t / d in the conventional example, as shown by a dashed line in FIG. The focus characteristics deteriorate at. Therefore, 0.3
It is desirable that ≦ t / d ≦ 0.65.

As a result of the above, 0.3 ≦ t / d ≦ of this embodiment
In the case of 0.65, the focusing voltage adjustment of the cathode ray tube device (hereinafter,
Since "just focus adjustment" is performed in the average current region, a voltage lower than the just focus voltage is applied in the low brightness region, and the state of the electron beam spot becomes a halo (overfocus) state. As a result of the combination of the astigmatism characteristics of the electron gun, the shape of the electron beam spot in the low luminance region is deteriorated in the vertical direction in which the electron beam spot diameter at the horizontal edge of the screen becomes halo as shown in FIG. . As a result, the moire on both sides of the screen, which was caused by the excessive narrowing of the beam spot, does not occur.

Further, this means that the electron beam spot diameters on both sides in the horizontal direction in the low luminance region become large, so that the resolution may be deteriorated, but the electron beam in the low luminance region of about 10 [μA] is considered. Since the spot diameter is small enough, there is no problem at all.

Further, the just focus voltage characteristic with respect to the beam current in the high luminance region above the average current region is almost the same as that of the conventional example as shown in FIG. 3, and the focus characteristic in the high luminance region is substantially maintained. It

Example 2. In Example 1, the change of the just focus voltage with respect to the beam current in the high brightness region is almost the same as that of the conventional example, but the divergence angle θ of the electron beam shown in FIG. 10 is slightly increased. Therefore, the deflection magnetic field is apt to be influenced, and a halo is generated in the vertical direction of the electron beam spot in the peripheral portion of the screen in the high luminance region, and the resolution is slightly deteriorated.

The second embodiment is intended to solve this problem, and the plate thickness t of the electron beam passage hole portion of the acceleration electrode 2 is set to 0.
While maintaining 3 ≦ t / d ≦ 0.65, as shown in FIG. 5A, the arrangement direction of the electron beam passage holes on the side of the control electrode 1 of the acceleration electrode 2 (the arrangement direction of the electron gun) (hereinafter, The length of the "horizontal direction" is the right angle direction (hereinafter "vertical direction")
It is sufficient to provide a rectangular slot 2d longer than the above). FIG. 5B is a trihedral view showing the shape of the slot 2d. By providing the slot 2d that is long in the horizontal direction, the divergence angle θ in the vertical direction of the electron beam can be suppressed as shown in FIG. 5C, and the vertical direction of the electron beam spots on both sides of the screen in the high brightness region can be suppressed. Since the halo of can be reduced, the deterioration of resolution can be prevented.

Embodiment 3 FIG. 6A and 6B are views showing a third embodiment of the present invention. FIG. 6A shows a sectional view of a triode portion, and FIG. 6B shows a shape of a slot 1d provided on the acceleration electrode 2 side of the control electrode 1. FIG. In this control electrode 1, the electron beam passage hole 1a is formed in a rectangular shape having a long horizontal direction, and the slot 1d is formed in a rectangular shape having a long vertical direction.

According to the third embodiment, due to the synergistic effect of the electron beam passage hole 1a and the slot 1d, the vertical divergence angle θ of the electron beam as shown in FIG.
Since the vertical halo of the electron beam spots on both sides of the screen applied to the high-luminance region can be further reduced as compared with the second embodiment, the deterioration of resolution can be further reduced.

Example 4. 7A and 7B are views showing Embodiment 4 of the present invention. FIG. 7A is a sectional view of a three-pole portion, and FIG. 7B shows a shape of a slot 3d provided on the accelerating electrode 2 side of the focusing electrode 3. In the three views, the slot 3d of the focusing electrode 3 is formed in a rectangular shape in which the vertical direction is longer than the horizontal direction.

According to the fourth embodiment, the divergence angle θ of the electron beam in the vertical direction can be suppressed to be smaller than that in the third embodiment as shown in FIG. The vertical halo of the electron beam spots on both sides can be further reduced, and the deterioration of resolution can be further reduced.

In the above embodiments, the electrodes 1, 2,
Although the slots 1d, 2d, and 3d provided in No. 3 have a rectangular shape, the same effect can be obtained even if they are oval or elliptical.

Further, although the slots 1d and 2d are provided in the third embodiment, a certain effect can be obtained even when only the slot 1d is provided. Further, although the slots 1d, 2d and 3d are provided in the fourth embodiment, a certain effect can be obtained even when only the slot 3d is provided.

Although the above embodiments have been described with respect to the high potential type electron gun, the same effects can be obtained by applying the same to a unipotential type electron gun and a multi-stage focusing type electron gun.

[0034]

According to the present invention, the ratio t / d of the plate thickness t of the electron beam passage hole of the accelerating electrode constituting the three-pole portion of the electron gun and the hole diameter d of the electron beam passage hole is 0.3≤. t / d ≦ 0.
Since it is set to 65, the focusing characteristic from the average current region of the electron beam to the high luminance region is good, and the moire generated on both sides of the screen in the low luminance region can be suppressed.

Further, the electron beam passage holes of the accelerating electrode are formed in a rectangle, an ellipse, or an ellipse whose length in the arrangement direction of the electron beam passage holes is longer than the right angle direction, and the surface of the electrode facing the control electrode is formed. Since the rectangular, elliptical or elliptical slot whose length in the electron gun array direction is longer than the right angle direction is formed, the vertical halo of the electron beam spots at both edges of the screen can be reduced in the high brightness area, and the acceleration electrode By reducing the plate thickness of, the deterioration of resolution due to the increase of the divergence angle can be improved.

Further, since a rectangular, oval or elliptical slot having a direction perpendicular to the length in the arrangement direction of the electron beam passage holes is formed on the surface of the control electrode facing the accelerating electrode, the focus in the high brightness region is increased. The characteristics are improved.

Further, since the slot which is longer in the direction perpendicular to the arrangement direction of the electron beam passage holes is formed on the surface of the focusing electrode facing the acceleration electrode, the focus characteristic in the high brightness region is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a three-pole portion of an electron gun according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing changes in the distance from the main lens to a virtual object point with respect to the beam current of Example 1.

FIG. 3 is a diagram showing a just focus voltage characteristic with respect to a beam current according to the first embodiment.

FIG. 4 is a diagram showing a shape of a low-luminance beam spot according to the first embodiment.

5A and 5B are a longitudinal sectional view of a triode portion of an electron gun of Embodiment 2 of the present invention, a trihedral view of an accelerating electrode, and an explanatory view of the operation.

FIG. 6 is a longitudinal sectional view of a three-pole portion of an electron gun according to a third embodiment of the present invention, a three-sided view of a control electrode, and an explanatory view of the operation.

FIG. 7 is a longitudinal sectional view of a three-pole portion of an electron gun according to a fourth embodiment of the present invention, a three-sided view of a focusing electrode, and an explanatory view of the operation.

FIG. 8 is a vertical cross-sectional view of an in-line type cathode ray tube.

FIG. 9 is a diagram showing a converged state on both sides.

FIG. 10 is a diagram showing an optical model of an electron beam.

FIG. 11 is a diagram showing a change characteristic of a distance from a main lens to a virtual object point with respect to a beam current value.

FIG. 12 is a diagram showing a just focus voltage characteristic with respect to a beam current value.

FIG. 13 is a diagram showing moire generated on both sides of the screen in a low brightness area.

[Explanation of symbols]

1 control electrode, 1a, 2a, 3a electron beam passage hole,
1d, 2d, 3d slots, 2 acceleration electrodes, 3 focusing electrodes, 6a cathodes.

Claims (4)

[Claims] 1. A control electrode, an acceleration electrode, a focusing electrode, and an anode each having a plurality of linearly arranged cathodes and a plurality of electron beam passage holes provided corresponding to the plurality of cathodes, are arranged at predetermined intervals. In an in-line type cathode ray tube provided with an electron gun which is sequentially arranged with a space t, the plate thickness t of the accelerating electrode is
And the hole diameter d of the electron beam passage hole, t / d is 0.3 ≦ t
/D≦0.65, an in-line type cathode ray tube. 2. A rectangular, oval or elliptical slot in which the length of the accelerating electrode facing the control electrode in the direction of arrangement of the electron beam passage holes is longer than the length in the direction orthogonal to the electron beam passage hole. 2. The in-line type cathode ray tube according to claim 1, wherein the electron beam passage hole is formed by a plate thickness t. 3. An electron beam passage hole of the control electrode is formed in a rectangular shape in which the length of the electron beam passage hole in the arrangement direction is longer than the length in the orthogonal direction, and the surface of the control electrode facing the acceleration electrode is formed. A rectangular, oval or elliptical slot whose length in the direction perpendicular to the electron beam passage holes is longer than that in the arrangement direction is formed so as to surround the electron beam passage holes. 2. The in-line type cathode ray tube according to claim 1, wherein t is t. 4. A rectangular, oval or elliptical slot whose length in a direction orthogonal to the arrangement direction of the electron beam passage holes is formed on a surface of the focusing electrode facing the accelerating electrode. The in-line type cathode ray tube according to claim 1, wherein the plate thickness of the electron beam passage hole portion is t.