JPH03205741A - Color picture tube - Google Patents

Abstract

PURPOSE:To improve the magnetic shielding effect and decrease the landing drift due to the outside magnetic field to the extent that there is practically no problem by providing protruded pieces made of a ferromagnetic substance and erected outward along the side face near four corners of a magnetic shield body. CONSTITUTION:Protruded pieces 22 made of a ferromagnetic substance and erected outward along the side face near four corners of a magnetic shield body 21 are provided. The protruded pieces 22 draw the horizontal component Bx of the magnetic field crossing a color picture tube in the horizontal axis direction to improve the magnetic shielding effect. The inside barrel-shaped magnetic field deformed by the magnetic shield body 21 is form-shaped by the magnetic field passing through the protruded pieces 22, the vertical component By of the magnetic field near the four corners is sharply reduced, and the landing drift due to geomagnetism can be reduced to the extent that there is practically no problem. The magnetic shielding effect of the magnetic shield body 21 is improved, the landing drift due to geomagnetism is decreased, and the deterioration of color purity can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) This invention relates to a color picture tube, and more particularly to a color picture tube in which the magnetic shielding effect of a magnetic shield is improved.

(Prior Art) Generally, a color picture tube has a panel (
1) and an envelope consisting of a funnel-shaped funnel (2) integrally joined to this panel (1), and on the inner surface of the panel (1), three-color phosphors that emit light in blue, green, and red are provided. A phosphor screen (3) consisting of layers is formed, and a shadow mask (4>) having a large number of electron beam passing holes formed inside thereof is attached opposite to and close to this phosphor screen (3). .

Furthermore, an electron gun <6> that emits three electron beams is disposed within the neck (5>) of the funnel (2).
The three electron beams emitted from the electron gun (6) are deflected horizontally and vertically by the magnetic field of the deflection yoke (7) attached to the outside of the funnel (2), and the phosphor screen (3) is deflected. It is formed in a structure that displays a color image by horizontal and vertical scanning.

In such a color picture tube, a phosphor screen (
3) In order to correctly display a color image on the screen, the three-color phosphor layer constituting the phosphor screen (3) and the electron beam passage hole of the shadow mask (4) must be arranged in a matching relationship. However, even if the three-color phosphor layer and the electron beam passage hole of the shadow mask (4>) are properly aligned,
The electron beam actually emitted from the electron gun (6) is affected by an external magnetic field such as the earth's magnetism and does not land correctly on the three-color phosphor layer. Therefore, in order to prevent the influence of this external magnetic field, conventionally one end is directly or indirectly fixed to the shadow mask (4>) inside the cone part (8) of the funnel (2>) in the direction of the electron gun (6). There is a type in which a magnetic shield (9) made of ferromagnetic metal is arranged extending from the top to the bottom.

The magnetic shield shown in FIG. 8 is the most common magnetic shield (9a) placed inside a rectangular funnel. This magnetic shield (9a) has a plate thickness of 0.1 to OJm
It is made of mild steel with a thickness of about 1.5 m, and is formed into a nearly rectangular hollow trapezoidal integral structure.

However, such a magnetic shield (9a) has a limit in shielding from external magnetic fields, and the desired beam landing may not be obtained in some cases. To solve this problem, it is necessary to make the direction of the magnetic field match the trajectory of the electron beam as much as possible, or to convert the magnetic field component into a direction that does not affect beam landing.

To explain the magnetic shielding effect of the magnetic shield (9), the magnetic field components that affect beam landing will be described as follows.

To simplify the explanation, we will discuss a color picture tube in which the three-color phosphor layer that is most common today consists of a striped phosphor layer parallel to the vertical axis (minor axis) of the screen. In the longitudinal direction of the screen, that is, in the vertical direction of the screen,
Even if landing misalignment occurs, color shift will not occur. However, in the horizontal axis (long axis) direction of the screen, landing deviation occurs as described below, resulting in deterioration of color purity.

Now, assuming that the vertical axis of the screen is y and the tube axis is 2, the magnetic field components that affect beam landing are the vertical axis component By and tube axis direction component Bz of the magnetic flux density IB.

By the way, in general, the Lorentz force IF that a charged particle receives is 1F = g\v x where the charge is g and the velocity is \V.
ll3, and for an electron beam, if the electron charge is e, then IF = -elvxlB.

Therefore, the horizontal axis component of the Lorentzka IF that affects the beam landing in the screen horizontal axis direction is FX, and the vertical axis velocity component and tube axis velocity component of the electron are V y. If v z, then Fx −−e (vy
Bz - vz B)' ), and the vertical axis component By and the tube axis direction component Bz of the magnetic flux density IB interact with the tube axis direction component vz and the vertical axis direction component vy of the velocity, respectively, causing a landing deviation. It turns out.

Therefore, as shown in FIG. 9, if there is a magnetic field that crosses the color picture tube in the horizontal axis direction, the magnetic shield (
In 9a), the magnetic field <11) inside thereof deforms into a barrel shape. Particularly in the case of earth's magnetism, the magnetic field shown in FIG. 9 corresponds to the case where the color picture tube is placed facing east or west. Then, due to the vertical axis direction magnetic field component By of the magnetic flux density IB generated at this time and the tube axis direction velocity component vz of the electrons, the electron beam is subjected to a force in the horizontal axis direction shown by the arrow (12>), and the electron beam is caused to land in a trapezoidal pattern. This landing deviation is particularly noticeable near the diagonal of the screen because the magnetic field (11) is barrel-shaped.

Furthermore, when a color picture tube is installed facing north or south, as shown in Figure 1O (a), due to the tube axis direction component Bz of the magnetic flux density 1B and the vertical axis direction velocity component vy of the electrons,
The electron beam receives a force in the horizontal axis direction shown by arrows (13a) and (13b), causing a counterclockwise landing deviation. Furthermore, as shown in (b), the electron beam is subjected to a force in the horizontal axis direction as shown by the arrow (14) due to the vertical axis direction component By of the magnetic flux density 1B in the northern hemisphere and the tube axis direction component vz of the electrons. , a landing deviation occurs in the direction of the horizontal axis direction arrow (l4).

From this relationship between magnetic flux and electron beam, Japanese Patent Laid-Open No. 58
15061, as shown in Figure 11, a V-shaped notch (
A magnetic shield (9b) in the form of 16> is shown.

Further, Japanese Utility Model Publication No. 55-36928 discloses an example in which magnetic shields are unevenly distributed on the upper and lower sides of the screen.

According to such a magnetic shield, the tube axis direction component Bz of the magnetic flux density IB absorbed by the short side wall (l7) of the magnetic shield (9a) shown in FIG. ), and as a result, the vertical axis magnetic field component By of the magnetic flux density IB is lower than the magnetic shield (9a) shown in FIG.
increases. As a result, the arrow (18a) in FIG. (
As shown in 18b), the beam landing moves to the right at the top of the screen and to the left at the bottom of the screen, creating a right rotation effect. This clockwise rotation effect offsets the landing shift of the counterclockwise rotation shown in FIG. 10(a), and improves color purity when the color picture tube is installed facing north or south.

There are various improvements to this type of magnetic shield. For example, Japanese Patent Application Laid-Open No. 13253/1989 describes a magnetic shield (9c ), but as shown in FIG. 14, Japanese Utility Model Publication No. 55-27957 further includes a magnetic shield (9d) having an opening (19) formed in the long side wall.
Publication No. 178945 discloses a magnetic shield (9e) that combines a V-shaped notch (l6) on the short side and an opening (19) on the long side wall, as shown in Fig. 15. .

However, none of these magnetic shields satisfactorily corrects the landing deviation over the entire screen. Therefore, compared to ordinary color picture tubes, the arrangement pitch of the electron beam passage holes in the shadow mask is small, and the arrangement pitch of the three-color phosphor layers is correspondingly small, making it difficult to use high-definition color picture tubes or shadow masks and phosphor layers. In large color picture tubes with a large distance from the screen, landing shifts due to the earth's magnetic field cannot be ignored, resulting in noticeable color shifts on the screen. In other words, none of the conventional magnetic shields is able to sufficiently correct the landing shift caused by the external magnetic field over the entire screen, which may cause color shift on the screen.

(Problems to be Solved by the Invention) As described above, there have conventionally been color picture tubes in which a magnetic shield is provided inside the funnel in order to prevent the influence of an external magnetic field on the electron beam.

However, with the most common hollow trapezoidal magnetic shield, the magnetic shielding effect is insufficient, and the desired landing of the electron beam may not be achieved. For this reason, some have improved this magnetic shield to have a structure that either aligns the direction of the magnetic field with the trajectory of the electron beam as much as possible, or converts it into a magnetic field component in a direction that does not affect beam landing.

However, none of these improved magnetic shields satisfactorily corrects the landing deviation over the entire screen, especially in high-definition color picture tubes and large color picture receivers with a wide gap between the shadow mask and the phosphor screen. In the case of tubes, landing deviations due to the earth's magnetic field cannot be ignored, causing deterioration of color purity.

This invention was made to solve the above-mentioned problems, and it enhances the magnetic shielding effect of the magnetic shield and converts the earth's magnetism into a magnetic field component in a direction that does not affect beam landing, so that landing due to the earth's magnetic field can be avoided. The purpose is to prevent deterioration of color purity by reducing the deviation to a level that poses no practical problem.

[Structure of the Invention] (Means for Solving the Problems) Attached to a substantially rectangular shadow mask disposed inside the panel, facing a phosphor screen formed on the inner surface of the substantially rectangular panel, In a color picture tube having a substantially rectangular trapezoidal magnetic shield extending inside a funnel integrally joined to the panel, ferromagnetic particles stand outward along the sides near the four corners of the magnetic shield. A protruding piece consisting of the body was provided.

Furthermore, in a similar color picture tube, ferromagnetic pieces were placed on the side surfaces near the four corners of the magnetic shield, separate from the magnetic shield.

(Function) As mentioned above, protrusions made of ferromagnetic material that stand up outward are provided along the side surfaces near the four corners of the magnetic shield, or the magnetic shield is provided on the side surfaces near the four corners of the magnetic shield. When a ferromagnetic piece is placed separately from the body, this protruding piece or ferromagnetic piece attracts the horizontal component Bx of the magnetic field that crosses the color picture tube in the horizontal axis direction, thereby increasing the magnetic shielding effect.
The magnetic field that has passed through the protruding piece or ferromagnetic piece shapes the barrel-shaped magnetic field inside the magnetic shield, which is deformed by the magnetic shield, and greatly reduces the vertical component By of the magnetic field near its four corners. It is possible to reduce the landing deviation due to this to a point where it poses no practical problem.

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

FIG. 1 shows a color picture tube which is one embodiment of the present invention. This color picture tube consists of a substantially rectangular panel (1) and a funnel-shaped funnel (1) integrally joined to this panel (1).
2), on the inner surface of the panel (1),
A phosphor screen (3) consisting of three color phosphor layers that emit light in blue, green, and red is formed, and this phosphor screen (3)
A shadow mask (4) having a large number of electron beam passage holes formed inside the mask is mounted opposite to and close to the mask. Further, an electron gun (6) that emits three electron beams is disposed within the neck (5) of the funnel (2). The electron beam emitted from this electron gun (6〉) is transmitted through the funnel (
The electron beam is deflected horizontally and vertically by the magnetic field of the deflection yoke (7) mounted on the outside of the electron beam (2), and scans the phosphor screen (3) horizontally and vertically through the electron beam passage hole of the shadow mask (4). .

In addition, an internal conductive film (2) is applied from the inner surface of the cone (8) of the funnel (2) to the inner surface of the adjacent part of the neck (5).
0) is formed. One end of the cone (8) is directly or indirectly fixed to the shadow mask (4) so as to surround the passage area of the electron beam emitted from the electron gun (6). A magnetic shield (2l) extending in the > direction is arranged.As shown in FIG. In particular, protruding pieces (22) made of ferromagnetic metal also stand up outwards near the four corners, preferably along the long sides.The magnetic shield (2l) 22> is formed and arranged in such a size that it does not come into contact with the internal conductive film (20) formed on the inner surface of the cone portion (8).

Although the drawings show that the protruding piece (22) is molded integrally with the main body part, this protruding piece may be formed separately from the main body part and attached by welding or the like.

More specifically, the magnetic shield (2) has a plate thickness of 0.
．． The projecting piece (22) is made of mild steel of about 25 mm, and the distance from the center of the magnetic shield (2l) to the short side (23) is L, as shown in Fig. 3 (a), and the mounting position is from the corner to the short side (23). When the distance to the magnetic shield (21) is g, it is installed at a position where g≦L/4, and as shown in FIG. It is attached so that 0≦θ≦90° with respect to the standard, and the protrusion length (width) d is formed to be 5 degrees or more.

By the way, when the magnetic shield (2l) is formed as described above, when the color picture tube is installed facing east or west, the earth's magnetism crosses the color picture tube in the horizontal axis direction, as shown in Figure 4 (a). As such, part of the magnetic field (26〉) is
It is attracted to the protrusion piece (22>), enters the magnetic shield (21) from this protrusion piece (22), passes through the long side of the magnetic cotton shield (21), and goes outward from the other protrusion piece (22). Therefore, when the above-mentioned magnetic shield (21) is used, the magnetic shielding effect is enhanced compared to the conventional magnetic shield, and at the same time, in the case of the conventional magnetic shield, the radiation is emitted as shown in FIG. As shown in , the magnetic field (11) inside the magnetic shield has a barrel shape, and the magnetic field (27) near the four corners has a certain part B in the vertical axis direction.
A landing shift occurred due to y, but by shaping the barrel-shaped magnetic field (11) inside it, a nearly parallel magnetic field <28>
This reduces landing slippage in the horizontal axis direction.

In other words, when the protruding piece (22) is provided as described above, the magnetic flux density inside the magnetic shielding body (21) is reduced, and the magnetic flux passing inside the magnetic shielding body (21) is converted into a horizontal axis component that does not affect beam landing. This makes it possible to reduce landing deviation due to the earth's magnetic field when the color picture tube is installed facing east or west.

For example, in the case of a 32-inch color picture tube,
When a magnetic field of ±30 μT is applied in the horizontal axis direction, a landing movement of 50 μm occurs in a color picture tube without a magnetic shield, but with the magnetic shield (2L) in this example, the landing movement is reduced to 40 μm. We were able to reduce the amount of landing movement by approximately 20%.

Therefore, the conventional magnetic shield can be applied to high-definition color picture tubes and large color picture tubes where color shift occurs, and the influence of geomagnetism can be minimized to the point where there is no problem. Furthermore, it can be effectively applied to color picture tubes for use in vehicles and aircraft, where it is necessary to keep the absolute amount of landing deviation due to earth's magnetic field small.

Note that if the size of the protruding piece (22) that produces this effect is too small, the above effect will hardly be obtained, and unless it comes into contact with the internal conductive film (20>) on the inner surface of the cone part (8), it will not be possible. The bigger the better, 5mm as mentioned above.
It is necessary to do more than that.

Furthermore, if the projection piece (22) of the magnetic shield (2l) is applied to the magnetic shield having the opening shown in FIG. 15, an even better magnetic shielding effect can be obtained. For example, in the case of a 32-inch color picture tube, the amount of landing deviation is 30μ.
It can be reduced to m.

Next, FIG. 5 shows another magnetic shield. This magnetic shield (2l) is the magnetic shield of the above embodiment (see Fig. 2).
In this case, protruding pieces (22) that stand outward along the side surfaces near the four corners are provided, while magnetic pieces (29) made of ferromagnetic metal are provided on the long sides near the four corners. They are placed in close contact with each other.

When the magnetic material pieces (29) are closely placed on the long sides near the four corners in this way, as shown in FIG. 15, the color picture tube is When installed facing east or west, the earth's magnetism crosses the magnetic shield (2l) in the horizontal axis direction, and a part of the magnetic field (2B) is attracted to the magnetic piece (29) and
29>, enters the magnetic shield (21), passes through the magnetic shield (21), and is radiated outward from another magnetic piece (29>).
The magnetic shield (21) in which 29) is arranged also enhances the magnetic shielding effect, and shapes the barrel-shaped magnetic field generated inside the conventional magnetic shield to form a nearly parallel magnetic field (28). A color picture tube can be constructed in which the landing shift in the horizontal axis direction can be reduced, and which has the same effect as the magnetic shield (21) provided with the protruding pieces.

In addition, when the magnetic material piece (29> of this magnetic shield (21>) is applied to the magnetic shield having the opening shown in FIG. 15,
As in the case of the magnetic shield provided with the protruding pieces, an even better magnetic shielding effect can be obtained.

[Effects of the Invention] A magnetic shield in the shape of a rectangular trapezoid is attached to a substantially rectangular shadow mask placed inside the panel facing the phosphor screen of the color picture tube and extends inside the funnel. Protruding pieces made of ferromagnetic material that stand up outward along the sides near the four corners of the magnetic shield are provided, or pieces of ferromagnetic material are placed separately from the magnetic shield on the sides near the four corners of the magnetic shield. , this protruding piece or ferromagnetic piece attracts the magnetic field component that crosses the color picture tube in the horizontal axis direction,
At the same time as increasing the magnetic shielding effect, the barrel-shaped magnetic field that is deformed by the magnetic shield and generated inside it is shaped by the magnetic field that passes through the protruding piece or the ferromagnetic piece, and the vertical component near the four corners of the magnetic field is shaped. By can be significantly reduced, and the landing deviation caused by an external magnetic field can be reduced to a level that poses no practical problem.

[Brief explanation of drawings]

1 to 6 are explanatory diagrams of embodiments of the present invention, in which FIG. 1 is a diagram showing the configuration of a color picture tube as an embodiment, FIG. 2 is a perspective view of the magnetic shield, and FIG. Figures 3 (a) and (b) are diagrams for explaining the position and mounting angle of the protruding piece of the magnetic shield, respectively, and Figures 4 (a) and (b)
) is a diagram showing the effect of a magnetic shield provided with the protrusion on a magnetic field applied in the horizontal axis direction, and the effect of a conventional magnetic shield shown in order to explain the effect on a magnetic field applied in the horizontal axis direction. 5 is a perspective view of a different magnetic shield, FIG. 6 is a diagram showing the effect of the magnetic shield on a magnetic field applied in the horizontal axis direction, and FIG. 7 is a diagram showing the configuration of a conventional color picture tube. , Figure 8 is a perspective view of the most common magnetic shield, Figure 9 is a diagram showing the effect of the magnetic shield on the magnetic field applied in the horizontal axis direction, and Figures 10 (a) and (b) are respectively Diagram 1 showing the direction of movement of the beam landing due to the magnetic field inside the magnetic shield.
Fig. 1 is a perspective view of a conventional improved magnetic shield, Fig. 12 is a diagram showing the effect of the magnetic shield on a magnetic field applied in the horizontal axis direction, and Figs. 13 to 15 are a perspective view of a conventional improved magnetic shield. FIG. 3 is a perspective view of another magnetic shield. 1...Panel 2...Funnel 3...
- Phosphor screen 4...Shadow mask l9...Aperture 22...Protrusion piece 6...Electron gun 2l...Magnetic shield 29...Magnetic material piece

Claims (2)

[Claims] (1) The inside of a funnel that is attached to a substantially rectangular shadow mask that is placed inside the panel, facing a phosphor screen formed on the inner surface of the substantially rectangular panel, and that is integrally joined to the panel. In a color picture tube having a substantially rectangular trapezoidal magnetic shield extending over the area, protrusions made of a ferromagnetic material are provided extending outward along the side surfaces near the four corners of the magnetic shield. A color picture tube featuring (2) The inside of a funnel that is attached to a substantially rectangular shadow mask that is placed inside the panel, facing a phosphor screen formed on the inner surface of the substantially rectangular panel, and that is integrally joined to the panel. A color picture tube having a substantially rectangular trapezoidal magnetic shield extending over the area, characterized in that a ferromagnetic piece is arranged on the side surface of the magnetic shield near the four corners in addition to the magnetic shield. color picture tube.