JPH04267036A - Color picture tube - Google Patents

Abstract

PURPOSE:To provide a color picture tube with good color purity regardless of the installation direction by offsetting the landing drift of left rotation generated when no magnetic field control plate is provided. CONSTITUTION:In a color picture tube fitted with an inner magnetic shielding body 11 on a mask frame 6 with an L-shaped cross section supporting the mask main body 5 of a shadow mask 4 arranged to face a fluorescent screen formed on the inner face of a panel, a magnetic field control plate 22 magnetically coupled with a side face end section and an inside stretch end section extended in the horizontal direction of the mask frame 6 is arranged between them.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube, and more particularly to a color picture tube that can reduce the effects of external magnetic fields such as earth's magnetism and provide good landing characteristics.

0002

2. Description of the Related Art Generally, a color picture tube has an envelope consisting of a glass panel 1 and a funnel-shaped glass funnel 2 integrally joined to the panel 1, as shown in FIG. A phosphor screen 3 made of a three-color phosphor layer that emits blue, green, and red light is formed on the inner surface of the panel 1, and a shadow mask 4 is arranged inside the phosphor screen 3, facing the phosphor screen 3. This shadow mask 4 consists of a mask body 5 in which a large number of electron beam passage holes are formed, and a mask frame 6 having an L-shaped cross section and attached to the periphery of this mask body 5. In addition, 3 electron beams 8 are placed in the neck 7 of the funnel 2.
An electron gun 9 that emits . The three electron beams 8 emitted from the electron gun 9 are deflected by a magnetic field generated by a deflection yoke 10 mounted on the outside of the funnel 2, and the fluorescent screen 3 is scanned horizontally and vertically. It is formed in a structure that displays a color image on the surface 3.

Usually, the phosphor screen 3 and the shadow mask 4 are arranged in a matching relationship so that the three electron beams 8 passing through the respective electron beam passage holes of the mask body 5 land correctly on the three color phosphor layers. However, the beam landing on the three-color phosphor layer is still affected by an external magnetic field such as earth's magnetism, and the color purity deteriorates due to landing deviation. Therefore, an internal magnetic shield 11 is conventionally attached to the mask frame 6 to shield the three electron beams 8 emitted from the electron gun 9 from external magnetic fields such as earth's magnetism.

This internal magnetic shield 11 has a plate thickness of 0.1
It is made of a ferromagnetic material such as a mild steel plate with a thickness of approximately 0.3 mm and mainly composed of iron, and as shown in FIG. 6, its basic structure is an integrally molded hollow trapezoid. but,
This internal magnetic shield 11 has a limited magnetic shielding effect, and good beam landing cannot be obtained.

[0005]Here, in order to simplify the explanation of the earth's magnetic beam landing, the magnetic shielding effect will be explained with respect to a color picture tube whose phosphor screen is composed of striped three-color phosphor layers extending in the vertical direction.

In a color picture tube in which the striped three-color phosphor layer extends vertically, the color purity does not deteriorate even if the landing deviates in the vertical direction. therefore,
The magnetic field that affects beam landing is centered around its vertical axis (Y
axis) direction component By and tube axis (Z-axis) direction component Bz
becomes.

In general, the Lorentz force F(
If the charge is q, the velocity v (vector), and the magnetic flux density is B (vector), it is expressed as F=qv×B.For electrons, if the charge is e, then F
=-ev×B.

Here, regarding a color picture tube in which striped three-color phosphor layers extend vertically, the horizontal axis (X
Because the deviation in the axial direction affects the beam landing,
If the horizontal axis component of the Lorentz force is FX, the vertical axis component of the magnetic flux density B is By, the tube axis direction component is Bz, the tube axis direction velocity component of the electron beam is vz, and the vertical axis direction velocity component is vy, then FX =-e(vyBz-vzBy). That is, vy and vz act on By and Bz, causing landing deviation.

In FIG. 7(a), the landing deviation due to the component Bz of the magnetic flux density B in the tube axis direction is shown by an arrow 12a. This is actually a landing shift caused by the tube axis direction component Bz of the earth's magnetism when the color picture tube is installed facing north, and the vertical axis direction velocity component vy of the electron beam due to vertical deflection. If the color picture tube is installed facing south, the arrow 12 shown in Figure 7(a)
A landing deviation occurs in the opposite direction to a. Also, Figure 7
In (b), the landing deviation due to the vertical component By of the magnetic flux density B is indicated by an arrow 12b. This is a landing deviation caused by the vertical component By of the earth's magnetism in the northern hemisphere and the velocity component vz in the tube axis direction of the electron beam.

As mentioned above, there is a limit to the magnetic shielding effect of the internal magnetic shield 11 shown in FIG. The tube axis direction component B of the geomagnetic field is present in the beam passage area.
A leakage magnetic field with z and vertical axis components By was present, causing the landing deviation shown in FIGS. 7(a) and 7(b) and degrading the color purity of the image.

Conventionally, in order to reduce the beam landing shift shown in FIG. 7(a), as shown in FIG. 8, a substantially rectangular hollow trapezoidal internal magnetic shield with a V-shaped notch 13 formed on the short side was used. 11a is disclosed in Japanese Unexamined Patent Publication No. 15061/1983.

In this internal magnetic shield 11a, when the color picture tube is installed facing north, the magnetic lines of force in the tube axis direction are forced to the long sides extending in the horizontal direction of the internal magnetic shield 11a, and as a result, Vertical component of geomagnetism By
increases, +By increases in the +Y direction, and -By increases in the -Y direction. As a result, the beam landing moves to the right at the top of the screen and moves to the left at the bottom of the screen. This corrects the counterclockwise landing deviation shown by the arrow 12a in FIG. 7(a), and prevents deterioration of color purity when the color picture tube is installed facing north or south. However, when the color picture tube is installed facing east or west, the horizontal axis component Bx of the earth's magnetism is transmitted from the V-shaped notch 13 to the internal magnetic shield 11a.
Since it becomes easier to enter the inner electron beam passing region, the magnetic flux density in the electron beam passing region increases and the magnetic field shape becomes more barrel-shaped. That is, for example, when a color picture tube is installed facing east, the shape of the leakage magnetic field becomes more barrel-shaped, as shown by the broken line 14 in FIG. The component By increases, and a trapezoidal landing deviation occurs as shown by an arrow 16. Furthermore, if the color picture tube is installed facing west, a landing shift occurs in the opposite direction to the broken line 14 in FIG.

[0013] In this way, with the conventional internal magnetic shield, if an attempt is made to reduce the landing deviation when the color picture tube is installed facing north or south, the landing deviation when the color picture tube is installed facing east or west is reduced. Since the deviation increases, the landing deviation when installed facing north or south and the landing deviation when installed facing east or west are adjusted and balanced by the amount of cut of the V-shaped cut 13. Therefore, it has been insufficient to improve the color purity of images in all installation directions.

Furthermore, the influence of external magnetic fields such as the earth's magnetism on beam landing increases as the size of the color picture tube increases. For example, in the case of an ultra-large color picture tube of about 34 inches, the distance from the electron gun to the phosphor screen increases. The distance is approximately 1.6 times that of a 21-inch color picture tube, and the movement of the electron beam is also approximately 2.5 times. Furthermore, since the distance between the phosphor screen and the shadow mask also increases, the movement of the electron beam increases accordingly. Actual measurements in Japan of a 34-inch color picture tube equipped with an internal magnetic shield show that when the color picture tube is changed from facing south to facing north, it moves about 50 mm.

Furthermore, recent high-quality ultra-large color picture tubes aim to have a horizontally elongated phosphor screen with an aspect ratio of 16:9, and the arrangement pitch of the three color phosphor layers is approximately 0.5 to 0.6 m.
Since the beam has been miniaturized to 30 m, the beam landing margin is as small as 30 to 40 μm. Therefore, in such a color picture tube, even if an internal magnetic shield is disposed, landing deviation is likely to occur due to the influence of earth's magnetism, etc., and color purity is likely to deteriorate.

[0016]

As described above, color picture tubes have conventionally been provided with internal magnetic shields to shield electron beams from external magnetic fields such as terrestrial magnetism. However, the conventional internal magnetic shield cannot sufficiently shield unnecessary magnetic fields in the electron beam passage region, resulting in landing deviation. In particular, in recent high-quality ultra-large color picture tubes, the beam landing margin has become smaller, so even if an internal magnetic shield is provided, there is a problem in that the deterioration of color purity becomes more noticeable.

The present invention has been made in view of the above-mentioned problems, and is intended to reduce landing errors caused by external magnetic fields such as earth's magnetism, and to improve not only ordinary color picture tubes but also high-quality ultra-large color picture tubes. The aim is to reduce the landing deviation when installed facing north or south without deteriorating the landing deviation when installed facing east or west, and to construct a color picture tube with good color purity regardless of the installation direction. shall be.

[Configuration of the invention]

[0019]

[Means for Solving the Problem] A shadow mask is arranged opposite to a fluorescent screen formed on the inner surface of a panel constituting an envelope, and this shadow mask is a mask body having a large number of electron beam passage holes. and a mask frame that supports the mask main body and is formed into an L-shaped cross section and includes a side surface that is approximately parallel to the tube axis and an inner protrusion that extends in the direction of the tube axis. In a color picture tube equipped with an internal magnetic shield that shields the electron beam generated from an external magnetic field, there is a portion between the horizontally extending side surface end and the inner protrusion end of the mask frame. A magnetic field control plate was placed to magnetically couple with.

[0020]

[Operation] As described above, magnetically connects the horizontally extending side and inner projecting ends of the L-shaped cross-sectional mask frame that supports the mask body of the shadow mask. When a color picture tube is installed facing north or south, the magnetic field control plate directs the tube axis component of the earth's magnetic field Bz toward the magnetic field control plate, increasing the vertical axis component, and increasing the vertical axis component in the +Y direction. In the +By and -Y directions, -By can be increased, canceling out the landing shift of counterclockwise rotation that occurs when there is no magnetic field control plate, and improving color purity.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings.

FIG. 1 shows a color picture tube which is one embodiment of the present invention. This color picture tube has an envelope consisting of a substantially rectangular glass panel 1 and a funnel-shaped glass funnel 2 integrally joined to the panel 1. The inner surface of the panel 1 has blue, green, A phosphor screen 3 made of a three-color phosphor layer that emits red light is formed, and a substantially rectangular shadow mask 4 is arranged inside the phosphor screen 3, facing the phosphor screen 3. Further, an electron gun 9 that emits three electron beams 8 is arranged within the neck 7 of the funnel 2. Further, inside the funnel 2, a hollow trapezoidal interior is attached directly or indirectly to the shadow mask 4 to shield the three electron beams 8 emitted from the electron gun 9 from external magnetic fields such as earth's magnetism. A magnetic shield 11 is arranged.

As shown in FIG. 2, the shadow mask 4 includes a substantially rectangular mask body 5 in which a large number of electron beam passage holes are formed, and a substantially rectangular mask body 5 attached to the periphery of the mask body 5. It consists of a mask frame 6. The mask frame 6 has an L-shaped cross section, which is composed of a side surface 20 that is substantially parallel to the tube axis and an inner protrusion 21 that is bent at the end of the side surface 20 on the electron gun 9 side and protrudes in the tube axis direction. It is formed. The internal magnetic shield 11 is connected to the mask frame 6
It is attached to the inner protrusion 21 of the.

Furthermore, in this color picture tube, a magnetic field is formed between the ends of the side surface portion 20 extending in the horizontal direction of the mask frame 6 and the ends of the inner projecting portion 21, which magnetically couple with these ends. A control plate 22 is attached by welding.

By the way, by arranging the magnetic field control plate 22 as described above, the color picture tube can be installed facing north or south without deteriorating the landing shift when the color picture tube is installed facing east or west. Therefore, the color picture tube can reduce the landing deviation when the camera is installed, and can display an image with good color purity regardless of the installation direction.

That is, as shown in FIG. 3, when the color picture tube is installed facing north, the internal magnetic shield 11
The magnetic field 24 in the tube axis direction cannot be completely shielded, and a leakage magnetic field 25 exists in the electron beam passage region inside the internal magnetic shield 10. However, when the magnetic field control plate 22 is arranged as described above, the leakage magnetic field 25 is attracted to the absorbed magnetic field 26.
Then, the vertical axis component By increases. That is, +
+By increases in the Y direction, and -By increases in the -Y direction. As a result, as shown in Figure 4, at the top of the screen,
In the right direction indicated by arrow 27a, at the bottom of the screen, arrow 27b
A landing shift in the left direction as shown in FIG. Similarly, when the color picture tube is installed facing south, a magnetic field is generated that offsets the landing shift if the magnetic field control plate 22 is not arranged.

That is, by arranging the magnetic field control plate 22 as described above, the color picture tube can be oriented north or south without deteriorating the landing deviation when the color picture tube is installed facing east or west. When installed, the leakage magnetic field 25 inside the internal magnetic shield 11 is shaped,
Increase the vertical axis component By, and +By in the +Y direction
, -By is increased in the -Y direction, and the magnetic field control plate 2
Offsetting the landing deviation when 2 is not placed,
A color picture tube that displays images with good color purity can be obtained.

As a specific example, in the case of a 34-inch 110-degree color picture tube, when a magnetic field control plate with a plate thickness of 0.15 mm is installed, compared to a color picture tube of the same size without a magnetic field control plate, the direction of the picture tube facing east or When installed facing west, the landing deviation was the same, but when installed facing north or south, the landing deviation could be reduced by about 50%.

The thickness of the magnetic field control plate can be set arbitrarily, and it is also possible to mold it integrally with the mask frame.

[0030]

Effects of the Invention: A magnetic field is controlled between the horizontally extending side and inner projecting ends of a mask frame having an L-shaped cross section that supports the mask main body of a shadow mask and is magnetically coupled to these ends. When the plate is placed, when the color picture tube is installed facing north or south, the tube axis component Bz of the geomagnetic field is oriented in the direction of the magnetic field control plate, increasing the vertical axis component, and +By and - in the +Y direction. -By in the Y direction
can be increased, canceling out the counterclockwise landing deviation that occurs when there is no magnetic field control plate, and making it possible to obtain a color picture tube with good color purity regardless of the installation direction.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a color picture tube that is an embodiment of the present invention.

FIG. 2 is a diagram showing the arrangement of a magnetic field control plate with respect to the shadow mask.

FIG. 3 is a diagram for explaining the effect of the magnetic field control plate on the magnetic field in the tube axis direction in a color picture tube in which the magnetic field control plate is arranged.

FIG. 4 is a diagram for explaining the movement of the beam landing of the color picture tube in which the magnetic field control plate is arranged.

FIG. 5 is a diagram showing the configuration of a conventional color picture tube.

FIG. 6 is a diagram showing the basic structure of the internal magnetic shield of the conventional color picture tube.

FIG. 7(a) is a diagram for explaining landing deviation due to the tube axis direction component of magnetic flux density, and FIG. 7(b) is a diagram for explaining landing deviation due to the vertical direction component of magnetic flux density. .

FIG. 8 is a diagram showing the structure of a conventional improved internal magnetic shield.

FIG. 9 is a diagram for explaining the movement of the beam landing of the color picture tube using the improved internal magnetic shield.

[Explanation of symbols]

1...Panel 3... Fluorescent screen 4...Shadow mask 5...Mask body 6...Mask frame 9...electron gun 11... Internal magnetic shield 20...Side part 21...Inner overhang 22...Magnetic field control board

Claims (1)

[Claims] Claim 1: A shadow mask is arranged opposite to a phosphor screen formed on the inner surface of a panel constituting an envelope, and this shadow mask is connected to a tube axis and a mask body in which a large number of electron beam passage holes are formed. It consists of a mask frame that is formed into an L-shaped cross section and that includes substantially parallel side parts and an inner overhang part that extends in the direction of the tube axis, and that supports the mask main body, and the electron beam emitted from the electron gun is attached to the mask frame. In a color picture tube equipped with an internal magnetic shield that shields the mask frame from an external magnetic field, a magnetic field is formed between the ends of the horizontally extending side surface and the inner protrusion of the mask frame. A color picture tube characterized in that a coupling magnetic field control plate is arranged.