JPH11149883A - Color cathode ray tube - Google Patents

Abstract

An object of the present invention is to provide a color cathode ray tube in which an external magnetic shield function of a magnetic shield 7 is greatly increased and occurrence of a landing error of an electron beam 13 is suppressed. SOLUTION: A panel part 1 having a fluorescent film 4 formed on an inner surface of a face plate 1A, a neck part 2 accommodating an electron gun 9,
A funnel portion 3 connecting the panel portion 1 and the neck portion 2, a shadow mask 6 disposed inside the panel portion 1 so as to face the fluorescent film 4, mounted inside a connection portion between the panel portion 1 and the funnel portion 3, and having an opening on the shadow mask side. A color cathode ray tube comprising a magnetic shield 7 having a substantially quadrangular pyramid shape having an opening 7B and an electron gun side opening 7B, and a deflection yoke 8 attached to the outside of the funnel unit 3. The shape of the electron gun side opening 7B is changed to a cathode ray tube tube. The distance D between the face plate side end of the magnetic core 8B of the deflection yoke 8 and the electron gun side end of the magnetic shield 7 in the plane including the axis is the inclination angle of the plane electron beam 13 with respect to the horizontal scanning line direction. It was formed so as to be almost constant against the change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray tube, and more particularly, to an improvement in the shape of a magnetic shield mounted in the color cathode ray tube, thereby greatly reducing the mislanding of an electron beam based on an external magnetic field applied to the color cathode ray tube. The present invention relates to a color cathode ray tube which is suppressed.

[0002]

2. Description of the Related Art Generally, a color cathode ray tube comprises a panel having a fluorescent film formed on the inner surface of a face plate, a neck for accommodating an electron gun, and a funnel connecting the panel and the neck. A vacuum envelope (glass bulb) is provided. In this vacuum envelope, a shadow mask is disposed at least inside the panel portion so as to face the fluorescent film, and approximately 4 holes having openings on the shadow mask side and the electron gun side are provided. A pyramid-shaped magnetic shield is mounted so as to extend from the inside of the funnel to the inside of the panel, and a deflection yoke is mounted outside the funnel.

[0003] During operation of the color cathode ray tube having such a configuration, while an electron beam emitted from the electron gun travels to the shadow mask, an external magnetic field existing at a place where the color cathode ray tube is installed, in particular, an influence of geomagnetism. Receiving
The trajectory of the electron beam shifts slightly from the original trajectory in accordance with the magnitude of the terrestrial magnetism and the direction in which the electron beam is applied, resulting in a displacement of the electron beam projected on the phosphor film, that is, a landing error. Become.

FIG. 5 is an explanatory diagram showing a state of occurrence of such an electron beam landing error.

As shown in FIG. 5, an electron beam 51 emitted from an electron gun (not shown) is bent in a predetermined direction from a deflection center O by a beam deflection action by a deflection yoke (not shown). Thereafter, the light beam travels straight in a bent state, and passes through one of the electron beam passage holes 52A of the shadow mask 52 to reach the arrival position P of the fluorescent film 53 formed on the inner surface of the face plate 1A. At this time, if the electron beam 51 is not affected by the external magnetic field at all, the vehicle travels on a normal running trajectory as shown by the solid line in FIG. Slightly deviating from the trajectory, the trajectory proceeds in a modified trajectory as shown by the dotted line in FIG. 5, and as a result, the position P ′ deviated by Δe from the arrival position P on the fluorescent film 53 where the electron beam 51 should originally reach. , And a so-called landing error of the electron beam 51 occurs.
When the landing error of the electron beam 51 occurs, not only does the color purity of the display image deteriorate, but also the white uniformity and the luminance uniformity of the display image significantly deteriorate.

The occurrence of a landing error of an electron beam in such a color cathode-ray tube is caused by shielding an electron beam traveling in the color cathode-ray tube from an external magnetic field. Specifically, a magnetic shield is provided from inside a funnel to inside a panel. It is known that the arrangement can be suppressed by extending the arrangement. In a color cathode ray tube, the arrangement of the magnetic shield is no longer essential.

FIGS. 6A to 6C are perspective views showing various structural examples of a magnetic shield used in a known color cathode ray tube.

As shown in FIGS. 6A to 6C,
Magnetic shield 60 used in known color cathode ray tubes
Has a substantially quadrangular pyramid shape having openings on the shadow mask side and the electron gun side, respectively, and the shape of the shadow mask side opening is a substantially rectangular shape having a flat edge. On the other hand, as shown in FIG. 6A, the shape of the electron gun side opening 61 is a substantially rectangular shape having a flat edge portion, and as shown in FIG. A substantially rectangular shape in which all four sides of the edge are cut into a V-shape, and a substantially rectangular shape in which all four sides of the edge are cut into a U-shape as shown in FIG. And the like.

When the magnetic shield 60 having such a structure is used for a color cathode ray tube, even if an external magnetic field, particularly a geomagnetism, is present at a place where the color cathode ray tube is disposed, a magnetic flux is applied to the magnetic shield 60 made of a magnetic metal material. Only when it is generated, the inside of the magnetic shield is shielded from the external magnetic field (terrestrial magnetism), so that the electron beam passing inside the magnetic shield 60 is not affected by the external magnetic field (terrestrial magnetism). For this reason, as a constituent material of the magnetic shield 60, a high-permeability metal material that can efficiently concentrate an external magnetic field (geomagnetism) is usually used.

[0010]

In recent years, along with the progress of color cathode ray tube manufacturing techniques, there has been a strong demand for higher definition of the fluorescent screen of the color cathode ray tube. With higher definition, the landing error tolerance of the electron beam has been considerably reduced. For this reason, in a recent color cathode ray tube, it is necessary to pay some attention to the magnetic shield 60 in order to increase the landing error margin of the electron beam.

As described above, the magnetic shield 60 used in the known color cathode ray tube has a generally quadrangular pyramid shape as described above, and the opening 61 on the electron gun side has a flat edge. Substantially rectangular shape having a section, four sides of the edge portion are substantially rectangular shapes cut in a V-shape, and four sides of the edge portion are substantially rectangular shape cut in all U-shapes Was used.

In the color cathode ray tube, it can be considered that the magnetic shield 60 and the magnetic core of the deflection yoke mounted near the magnetic shield 60 form one magnetic circuit.

In the present specification, the angle θ with respect to the horizontal scanning line direction of the electron beam, including the tube axis of the cathode ray tube, will be hereinafter referred to.
The distance D between the face plate-side end surface of the magnetic core and the electron gun-side end of the magnetic shield in the cutting plane inclined only is referred to as the "magnetic shield-yoke core distance".
In addition, the angle θ is referred to as “the inclination angle of the plane including the tube axis”.

The magnetic shield 60 used in the known color cathode ray tube has a distance D between the magnetic shield and the yoke core,
The configuration was not substantially constant with respect to the change in the inclination angle θ of the plane including the tube axis.

FIG. 3 is an explanatory view showing the relationship between the distance D between the magnetic shield and the yoke core and the inclination angle θ of the plane including the tube axis in the color cathode ray tube in a polar coordinate format. It shows the distance D between the magnetic shield and the yoke core with respect to the known magnetic shield 60, and the circled line shows the distance D between the magnetic shield and the yoke core in the magnetic shield 7 according to the embodiment of the present invention described later. .

In FIG. 3, reference numeral 8B denotes a magnetic core of the deflection yoke.

[0017] As shown in FIG. 3, in a known color cathode ray tube, when the calculated distance D between the magnetic shield yoke core, the distance of the midpoint M _H in the long side direction (horizontal direction) D _HM, short The distance of the midpoint M _{V in} the side direction (vertical direction) is D
_{When VM} and the distance between the corners are D _C , D _HM <D _VM <
D _C relationship of. Then, the distance between the magnetic shield yoke core D becomes successively larger towards the D _C from D _HM toward the corner portion from the intermediate point M _H in the long side direction (horizontal direction), similarly, the short side direction (vertical (Direction), it gradually increases from D _VM toward D _C from the middle point M _V toward the corner.

Like a known color cathode ray tube, the configuration of the magnetic shield 60 is such that the distance between the magnetic shield and the yoke core is D.
Is not constant with respect to the change in the inclination angle θ of the plane including the tube axis, the magnitude of the magnetic resistance also corresponds to the distance D between the magnetic shield and the yoke core, that is, the change in the inclination angle θ of the plane including the tube axis. Changes in response to At this time, the magnetic flux due to the external magnetic field concentrates on the portion having low magnetic resistance, and the magnetic shield 60
Since the magnetic flux does not uniformly flow through the whole, a sufficient shielding effect by the magnetic shield 60 cannot be expected, and the electron beam 51 passing through the inside of the magnetic shield 60 is slightly affected by external magnetism (earth magnetism). The running trajectory changes slightly.

As described above, the known color cathode ray tube cannot completely shield the external magnetism (geomagnetism) by the magnetic shield 60, and as shown in FIG. And the traveling path slightly changes, the arrival position of the electron beam 51 on the phosphor film reaches a position P ′ slightly shifted from the original arrival position P, so that a so-called landing error occurs. Become. The known color cathode ray tube has a problem that, when a landing error occurs, the color purity of the display screen is deteriorated, and the uniformity of white or the brightness is also deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to significantly increase the shielding function of a magnetic shield against external magnetism and sufficiently suppress the occurrence of electron beam landing errors. It is to provide a cathode ray tube.

[0021]

In order to achieve the above object, a color cathode ray tube according to the present invention is characterized in that the shape of the opening of the magnetic shield on the electron gun side is such that the distance between the magnetic shield and the yoke core is inclined on a plane including the tube axis. It is configured to be substantially constant with changes in angle.

In order to achieve the above object, a color cathode ray tube according to the present invention is characterized in that the shape of the opening of the magnetic shield on the electron gun side is changed by changing the inclination angle of the plane including the tube axis of the cathode ray tube. The maximum value of the distance is Dma
x, when the minimum value is Dmin, and the average value is Dave,
0.75 Dave ≦ (Dmax + Dmin) / 2 ≦ 1.
25Dave is formed, or
Dmax ≦ 1.5Dave and 0.5Dave ≦ D
min.

Note that the average value Dave in this case is equal to the magnetic shield distance at the midpoint _MH in the long side direction (horizontal direction).
Yoke core distance D _HM, magnetic shielding yoke core distance D _C between the magnetic shielding yoke core distance D _VM, the corner portion at the midpoint M _V in the short side direction (vertical direction)
_May be defined by (D _HM + D _VM + D _C ) / 3.

According to the present invention, the magnetic resistance of the magnetic circuit composed of the magnetic shield and the magnetic core of the deflection yoke mounted near the magnetic shield is limited to the entire circumference of the end of the magnetic core on the face plate side. Over the entire magnetic shield, the magnetic flux based on the external magnetic field flows almost uniformly over the entire magnetic shield. A magnetic shielding effect can be achieved, and as a result, the electron beam is less likely to be affected by an external magnetic field, and it is possible to sufficiently suppress the occurrence of a landing error of the electron beam.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment of the present invention, a color cathode ray tube has at least a panel portion having a fluorescent film formed on an inner surface of a face plate, a neck portion accommodating an electron gun, and a panel portion. And a funnel part connecting the neck part, a shadow mask arranged inside the panel part facing the fluorescent film, and mounted inside the connection part of the panel part and the funnel part, with openings on the shadow mask side and the electron gun side. And a deflection yoke attached to the outside of the funnel portion, wherein the shape of the opening of the magnetic shield on the side of the electron gun is set in a plane including the tube axis of the cathode ray tube. The distance between the face plate side end of the magnetic core and the electron gun side end of the magnetic shield is almost constant with respect to changes in the tilt angle of the plane electron beam with respect to the horizontal scanning line direction. It is obtained by forming so that.

In another embodiment of the present invention, the shape of the opening on the electron gun side of the magnetic shield is changed with respect to the change in the inclination angle of the plane including the tube axis of the cathode ray tube.
The maximum value of the distance between the yoke cores is Dmax, and the minimum value is Dmi.
n, when the average value is Dave, 0.75 Dave ≦
(Dmax + Dmin) /2≦1.25Dave, or Dmax ≦ 1.5D
ave and 0.5 Dave ≦ Dmin.

Note that the average value Dave in this case is equal to the magnetic shield value at the midpoint _MH in the long side direction (horizontal direction).
Yoke core distance D _HM, magnetic shielding yoke core distance D _C between the magnetic shielding yoke core distance D _VM, the corner portion at the midpoint M _V in the short side direction (vertical direction)
_May be defined by (D _HM + D _VM + D _C ) / 3.

According to these embodiments of the present invention, the shape of the opening of the magnetic shield on the electron gun side is set so that the distance between the magnetic shield and the yoke core is substantially constant with respect to the change in the inclination angle of the plane including the tube axis. Or a value within a predetermined range, the magnetic shield,
The magnetic resistance of a magnetic circuit composed of the magnetic core of the deflection yoke mounted near the magnetic shield has a substantially uniform value over the entire circumference of the face plate side end of the magnetic core, or has substantially no effect. Since the value is a constant value within the range, the magnetic flux based on the external magnetic field flows almost uniformly throughout the magnetic shield, and the magnetic shield can achieve a sufficient magnetic shielding effect against the external magnetic field. If the magnetic shield sufficiently performs the magnetic shielding effect against the external magnetic field, the electron beam traveling inside the color cathode ray tube becomes less affected by the external magnetic field, and the traveling trajectory of the electron beam may change. Therefore, the occurrence of a landing error is sufficiently suppressed, and the color purity of the display screen is not degraded, and the uniformity of white or the luminance is not degraded.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic structure of an embodiment of a color cathode ray tube according to the present invention.

In FIG. 1, 1 is a panel portion, 1A is a face plate, 2 is a neck portion, 3 is a funnel portion, 4 is a fluorescent film, 5 is a support frame, 6 is a shadow mask,
6A is an electron beam passage hole, 7 is a magnetic shield, 7A is a shadow mask side opening of the magnetic shield 7, 7B is an electron gun side opening of the magnetic shield 7, 8 is a deflection yoke, 8A is a coil, 8B is a magnetic core, 9B. Is an electron gun, 10 is a purity adjustment magnet, 11 is a 4-pole magnet for side beam static convergence adjustment, 12 is a 6 pole magnet for center beam static convergence adjustment,
Reference numeral 13 denotes an electron beam, and O denotes a center of deflection of the electron beam 13.

The vacuum envelope (bulb) constituting the color cathode ray tube has a panel portion 1 having a face plate 1A on the front side, an elongated cylindrical neck portion 2 containing an electron gun 9 therein, and a panel portion 1 And a funnel part 3 having a substantially funnel shape connecting the neck part 2. The panel unit 1
A fluorescent film 4 is formed on the inner surface of the face plate 1A, and a support frame 5 is arranged and fixed on the inner peripheral portion. The peripheral edge of the shadow mask 6 is held by the support frame 5, and the effective surface is arranged to face the fluorescent film 4.
The substantially quadrangular pyramid-shaped magnetic shield 7 has the shadow mask side opening 7A held by the support frame 5, and is arranged and fixed inside the portion from the panel unit 1 to the funnel unit 3. The magnetic shield 7 is provided with a shadow mask side opening 7A on one side of the substantially quadrangular pyramid and an electron gun side opening 7B on the other side. The deflection yoke 8 has a coil 8A mounted inside a magnetic core 8B.
And the neck portion 2 is mounted outside the vicinity of the joint portion. A purity adjusting magnet 10, a side beam static convergence adjusting quadrupole magnet 11, and a center beam static convergence adjusting hexapole magnet 12 are arranged side by side outside the neck portion 2. Electron gun 9
Are deflected in a predetermined direction by a deflection yoke 8, and then pass through a predetermined electron beam inside the magnetic shield 7 and the effective surface of the shadow mask 6. The light is projected onto the fluorescent film 4 through the hole 6A.

In this case, the image display operation of the color cathode ray tube of the present embodiment is almost the same as the image display operation of this type of known color cathode ray tube, and such operation is well known in the art. Therefore, the description of the image display operation in the color cathode ray tube of the present embodiment is omitted.

FIGS. 2A to 2C are diagrams showing an example of the magnetic shield 7 used in the color cathode ray tube of the present embodiment shown in FIG. 1, wherein FIG. A top view, (b) is a side view of a long side (horizontal direction), and (c) is a side view of a short side (vertical direction).

In FIGS. 2A to 2C, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

As shown in FIGS. 2A to 2C,
The magnetic shield 7 is formed in a substantially quadrangular pyramid shape as a whole, is provided with a substantially rectangular large-diameter opening 7A on the shadow mask side, and has a long side and a short side on the electron gun side as described below. The intermediate region is cut into a slope shape, and is provided with an opening 7B having a small diameter that approximates a rectangle as a whole.

In this case, the cut shape in the intermediate region of each of the long side and the short side in the electron gun side opening 7B is such that the distance D between the magnetic shield and the yoke core is such that the change in the inclination angle θ of the plane including the tube axis changes. It is formed so as to be substantially constant.

FIG. 3 shows the relationship between the distance D between the magnetic shield and the yoke core and the inclination angle θ of the plane including the tube axis, as described above, on a polar coordinate system, with the color cathode ray tube of this embodiment and a known color cathode ray tube. It is a comparison with a pipe.

The line indicated by the rectangle in FIG.
In contrast to the known distance D between the magnetic shield and the yoke core with respect to the magnetic shield 60, the line indicated by a circle indicates the distance D between the magnetic shield and the yoke core in the magnetic shield 7 according to the embodiment of the present invention described later. is there.

As shown by the circled line in FIG. 3, the magnetic shield 7 of the color cathode ray tube of the present embodiment has an opening shape on the electron gun side, the distance D between the magnetic shield and the yoke core is smaller than that of the magnetic core 8B. almost a constant value D _R over the entire circumference of the face plate end, as a result, the magnetic shield 7
The magnetic resistance of the magnetic circuit composed of the magnetic core 8B and the magnetic core 8B is substantially constant over the entire circumference of the end of the magnetic core 8B on the face plate side.

Therefore, in the color cathode ray tube of the present embodiment, even when external magnetism (geomagnetism) is applied, almost all of the magnetic flux based on the external magnetism (geomagnetism) is generated by the substantially uniform magnetic resistance exhibited by the magnetic shield 7. Since the magnetic shield 7 passes through the inside of the magnetic shield 7, the magnetic shield 7 can sufficiently exhibit a shielding effect of external magnetism (geomagnetism). In the color cathode ray tube of the present embodiment, since the shielding effect of the magnetic shield 7 is sufficiently exhibited, the electron beam 13 traveling inside the color cathode ray tube is hardly affected by external magnetism (geomagnetism). Since the traveling trajectory of the beam 13 does not deviate, occurrence of a landing error is sufficiently suppressed. As a result, the color cathode-ray tube of the present embodiment can significantly improve the deterioration of color purity and the uniformity of whiteness or the brightness, as compared with the known color cathode-ray tube of this type.

FIG. 4 shows the intensity of an external magnetic field applied experimentally from the horizontal direction in the color cathode ray tube of this embodiment.
5 is a graph showing the relationship between the spot movement (change) amount of the electron beam 13 (see FIG. 1) and a curve A, which is a characteristic of the color cathode ray tube of the present embodiment, and a curve B, which is provided for reference. This is a characteristic exhibited by a known color cathode ray tube.

As shown in FIG. 4, the color cathode ray tube of the present embodiment and the known color cathode ray tube both increase in intensity of the external magnetic field as shown by the curves A and B. The point that the spot movement (change) amount of the electron beam 13 also increases in proportion to the same is the same, but the ratio of the increase in the spot movement (change) amount of the electron beam 13 to the increase in the intensity of the external magnetic field is as follows. The color cathode ray tube of the present embodiment is about half the color cathode ray tube of the present embodiment as compared with the known color cathode ray tube. It can be seen that the magnetic shield 60 is much better than the external magnetic shield effect.

In this embodiment, the cut shape of the intermediate portion of each of the long side and the short side in the electron gun side opening 7B of the magnetic shield 7 is determined by setting the distance D between the magnetic shield and the yoke core to the inclination angle θ of the plane including the tube axis. substantially while indicating the formed example shown a constant value D _R, cut each intermediate region of the long and short sides of the electron gun side opening 7B of the magnetic shield 7 of the present invention to changes in The shape is not limited to the shape described above, and may be a shape described below.

That is, the opening 7 B of the magnetic shield 7 on the electron gun side.
And the maximum value of the change in the distance D between the magnetic shield and the yoke core with respect to the change in the inclination angle θ of the plane including the tube axis is Dma.
x, when the minimum value is Dmin, and the average value is Dave,
0.75 Dave ≦ (Dmax + Dmin) / 2 ≦ 1.
25Dave is formed, or
Dmax ≦ 1.5 Dave and 0.5 Dave ≦ D
Even when the magnetic shield 7 is formed so as to satisfy min, the obtained magnetic shield 7 can obtain a shield function according to the excellent shield function of the magnetic shield 7 used in the above-described embodiment. As a result, it is possible to obtain substantially the same effect as the effect obtained in the above embodiment.

The average value Dave in this case is such that the distance at the midpoint M _H in the long side direction (horizontal direction) is D _HM , the distance at the mid point M _V in the short side direction (vertical direction) is D _VM ,
When the distance in the corner portion was set to D _C, (D _HM + D
_VM + D _C ) / 3.

The distance D _C at the corner portion is set to the minimum value Dm of the change in the distance D between the magnetic shield and the yoke core.
By selecting a value close to in, it is possible to effectively suppress the occurrence of a landing error of the electron beam. This is because the magnetic resistance in the corner part where the landing error margin of the electron beam is small is small,
This is because the magnetic flux of the external magnetic field is concentrated there, and the magnetic shielding effect is enhanced.

[0048]

As described above, according to the present invention, the shape of the opening on the electron gun side of the magnetic shield is substantially constant with respect to the change in the inclination angle θ of the plane including the tube axis, with the distance D between the magnetic shield and the yoke core. Or a value within a predetermined range, and the magnetic resistance of the magnetic circuit composed of the magnetic shield and the magnetic core of the deflection yoke changes with respect to the change in the inclination angle θ of the plane including the tube axis. Is set to a value that is almost constant or within a range that does not substantially affect the magnetic flux, so that the magnetic flux due to the external magnetic field passes almost uniformly through the entire magnetic shield, and the magnetic shield , The electron beam traveling inside the color cathode ray tube is hardly affected by external magnetism, and the traveling locus of the electron beam does not deviate. Therefore, the occurrence of a landing error is sufficiently suppressed, and there is an effect that the color purity of the display screen is not degraded, and the uniformity of white or the luminance is not degraded.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of a color cathode ray tube according to the present invention.

FIG. 2 is a configuration diagram illustrating an example of a configuration of a magnetic shield used in the color cathode ray tube illustrated in FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship between a distance between a magnetic shield and a yoke core and an inclination angle of a plane including a tube axis.

FIG. 4 is a characteristic diagram showing a relationship between a horizontal external magnetic field and a moving amount of an electron beam spot for a color cathode ray tube of the present invention and a known color cathode ray tube.

FIG. 5 is an explanatory diagram showing a state of occurrence of a landing error of an electron beam.

FIG. 6 is a perspective view showing a configuration example of different magnetic shields used in a known color cathode ray tube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Panel part 1A Face plate 2 Neck part 3 Funnel part 4 Fluorescent film 5 Support frame 6 Shadow mask 6A Electron beam passage hole 7 Magnetic shield 7A Shadow mask side opening 7B Electron gun side opening 8 Deflection yoke 8A Coil 8B Magnetic material core 9 Electron gun 10 Purity adjustment magnet 11 4-pole magnet for side beam static convergence adjustment 12 6-pole magnet for center beam static convergence adjustment 13 Electron beam

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidehiro Mitsumura 3300 Hayano Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd.

Claims (3)

[Claims] At least a panel portion having a fluorescent film formed on an inner surface of a face plate, a neck portion containing an electron gun, a funnel portion connecting the panel portion and the neck portion, and A substantially quadrangular pyramid-shaped magnetic shield, which is mounted inside a connecting portion between the panel portion and the funnel portion, and has openings on the shadow mask side and the electron gun side; A deflection yoke attached to the outside of the funnel portion, wherein the opening shape of the magnetic shield on the electron gun side is in the plane including the tube axis of the cathode ray tube, and the face plate side of the magnetic core of the deflection yoke on the face plate side. The distance between the end and the end of the magnetic shield on the side of the electron gun is substantially equal to the change in the inclination angle of the plane electron beam with respect to the horizontal scanning line direction. A color cathode ray tube characterized by being formed so as to be constant. 2. A panel having a fluorescent film formed on an inner surface of a face plate, a neck accommodating an electron gun, a funnel connecting the panel and the neck, and a panel inside the panel. A substantially quadrangular pyramid-shaped magnetic shield, which is mounted inside a connecting portion between the panel portion and the funnel portion, and has openings on the shadow mask side and the electron gun side; A deflection yoke attached to the outside of the funnel portion, wherein the opening shape of the magnetic shield on the electron gun side is in the plane including the tube axis of the cathode ray tube, and the face plate side of the magnetic core of the deflection yoke on the face plate side. The distance between the end and the end of the magnetic shield on the electron gun side is the maximum value for the change in the inclination angle of the plane electron beam with respect to the horizontal scanning line direction. Is Dmax, the minimum value is Dmin, and the average value is Dave, and 0.75 Dave ≦ (Dm
ax + Dmin) /2≦1.25 Dave. 3. A panel having a fluorescent film formed on an inner surface of a face plate, a neck accommodating an electron gun, a funnel connecting the panel and the neck, and a panel inside the panel. A substantially quadrangular pyramid-shaped magnetic shield, which is mounted inside a connecting portion between the panel portion and the funnel portion, and has openings on the shadow mask side and the electron gun side; A deflection yoke attached to the outside of the funnel portion, wherein the opening shape of the magnetic shield on the electron gun side is in the plane including the tube axis of the cathode ray tube, and the face plate side of the magnetic core of the deflection yoke on the face plate side. The distance between the end and the end of the magnetic shield on the electron gun side is the maximum value for the change in the inclination angle of the plane electron beam with respect to the horizontal scanning line direction. Is Dmax, the minimum value is Dmin, and the average value is Dave, 0.5 Dave ≦ Dmi
n, and a color cathode ray tube formed to satisfy Dmax ≦ 1.5 Dave.