JPH06162946A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a color cathode-ray tube having high color purity by reducing the dislocation of landing due to external magnetic field such as earth magnetism. CONSTITUTION:This color cathode-ray tube has a shadow mask 4 of approximately rectangular form comprising a mask body 5 faced to a phosphor screen 3 laid on the internal surface of a panel 1 of approximately rectangular form, and a mask frame 6 mounted along the periphery of the mask body 5. In addition, the mask frame 6 is fitted with a hollow magnetic shield body 20 of approximately rectangular trapezoid at a position inside the expanded section 13 of a funnel 2. In this case, the short side of the magnetic shield body 20 is made larger than the long side thereof, and the side end of the small diameter opening of the short side is formed in such a way as projected toward the extension direction of the short side.

Description

Detailed Description 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 capable of reducing the influence of an external magnetic field such as the earth's magnetism and obtaining good landing characteristics.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5, a color picture tube includes an envelope including a substantially rectangular glass panel 1 and a funnel-shaped glass funnel 2 integrally joined to the panel 1. On the inner surface of the panel 1, there is formed a phosphor screen 3 composed of a phosphor layer of three colors which emits blue, green and red, and facing the phosphor screen 3, a substantially rectangular shadow is formed inside thereof. Mask 4 is placed. The shadow mask 4 is composed 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 attached to the peripheral portion of the mask body 5. On the other hand, in the neck 7 of the funnel 2, an electron gun 9 for emitting a three electron beam 8 is arranged. And this electron gun 9
The 3 electron beam 8 emitted from the device is deflected by the magnetic field generated by the deflection yoke 10 mounted outside the funnel 2, and the phosphor screen 3 is horizontally and vertically scanned to reproduce a color image. Has been formed.

Usually, the shadow mask 4 has a predetermined alignment relationship with the phosphor screen 3 so that the three electron beams 8 passing through the electron beam passage holes of the mask body 5 land correctly on the three-color phosphor layer. However, the beam landing on the three-color phosphor layer is still affected by an external magnetic field such as the earth's magnetism, and the Lorentz force bends the orbit of the electron beam 8 so that it does not land correctly on the predetermined phosphor layer. It causes deterioration of color purity. Therefore, conventionally, an inner magnetic shield 12 that shields the three electron beams 8 emitted from the electron gun 9 from an external magnetic field such as the earth's magnetism is attached to the mask frame 6 and arranged inside the large-diameter portion 13 of the funnel 2. There is.

The internal magnetic shield 12 has a plate thickness of 0.1 to
It is made of a ferromagnetic material such as a mild steel plate having iron as a main component of about 0.3 mm, and as shown in FIG. 6, an integrally formed hollow rectangular trapezoidal shape has a basic structure. However, with this internal magnetic shield 12, the magnetic shield action is limited, and sufficiently good beam landing cannot be obtained.

Here, in order to simplify the description of the geomagnetic beam landing, the magnetic shielding action will be described for a color picture tube in which the phosphor screen is composed of a vertically elongated striped three-color phosphor layer.

Generally, the deviation of the beam landing in the color picture tube is determined by the angle of the electron beam after passing through the electron beam passage hole of the shadow mask, and coincides with the direction of the Lorentz force which the whole electron beam receives by the magnetic field. Therefore, the beam landing direction (shift direction) matches the Lorentz force direction.

In the color picture tube in which the stripe-shaped three-color phosphor layer extends in the vertical direction, the color purity does not deteriorate even if the beam landing shifts in the vertical direction. Therefore, the magnetic field that affects the beam landing is the vertical axis (y-axis) direction component By of the magnetic flux B and the tube axis (z-axis) direction component Bz. Then, the tube axis direction velocity component vz and the vertical axis direction velocity component vy of the electron beam act on the vertical axis direction component and the tube axis direction component By and Bz, respectively, and a beam landing shift occurs.

In FIG. 7 (a), the deviation of the beam landing due to the tube axial component Bz of the magnetic flux B is shown by an arrow 14a. This is actually a deviation of the beam landing due to the tube axis direction component Bz of the geomagnetism and the vertical axis direction velocity component vy of the electron beam due to the vertical deflection when the color picture tube is installed in the north direction. When the color picture tube is installed in the south direction, the beam landing is displaced in the direction opposite to the arrow 14a shown in FIG. 7 (a). Further, FIG. 7B shows the deviation of the beam landing due to the vertical component By of the magnetic flux B by an arrow 14b. This is the deviation of the beam landing due to the vertical component By of the geomagnetism By in the northern hemisphere and the velocity component vz of the electron beam in the tube axis direction.

As described above, since the magnetic shielding effect of the internal magnetic shield 12 shown in FIG. 6 is limited, in a color picture tube having such an internal magnetic shield, the inside of the internal magnetic shield is In the electron beam passage area, there is a leakage magnetic field having the above-mentioned geomagnetic field component Bz in the tube axis direction and component By in the vertical axis direction, and the landing shift shown in FIGS. I was letting it.

Conventionally, in order to reduce the deviation of the beam landing shown in FIG. 7 (a), as shown in FIG. 8, a substantially rectangular trapezoidal hollow having V-shaped cuts 16 formed in its short sides. The internal magnetic shield 12a is disclosed in JP-A-53-15061.

In this internal magnetic shield 12a, when the color picture tube is installed in the north direction, the magnetic flux in the tube axial direction is forced in the direction toward the long side extending in the horizontal direction of the internal magnetic shield 12a. . Therefore, with this coercion, the vertical component of the geomagnetic field By increases, and + By in the + Y direction,
Also, -By increases in the -Y direction. As a result, the beam landing moves to the right in the upper part of the screen, and the right landing shifts to the left in the lower part of the screen. this is,
The deviation of the left-handed beam landing indicated by the arrow 14a in FIG. 7 (a) is corrected to prevent the deterioration of color purity when the color picture tube is installed in the north or south direction.

However, when the color picture tube is installed in the east or west direction, the component Bx in the horizontal axis direction of the geomagnetism from the V-shaped cut 16 easily enters the electron beam passage area inside the inner magnetic shield 12a. The magnetic flux in the electron beam passage region increases and the magnetic field shape becomes more barrel-shaped. That is, for example, when a color picture tube is installed in the east direction, the shape of the stray magnetic field becomes more barrel-shaped as shown by the broken line 17 in FIG. 9 (a), and as shown in FIG. The vertical axis component By of the geomagnetism increases as it approaches the corner portion of 18. As a result, a trapezoidal beam landing deviation shown by arrow 19 in FIG. 10 occurs. Further, when the color picture tube is installed in the west direction, the deviation of the beam landing in the direction opposite to the arrow 19 in FIG. 10 occurs.

The strength of the barrel-shaped magnetic field shown in FIG. 10 varies depending on the cut amount of the V-shaped cut 16 of the internal magnetic shield 12a. Therefore, by optimizing the depth of cut of the V-shaped notch 16, the deviation of the beam landing when the color picture tube is installed in the north or south direction and the landing deviation when the color picture tube is installed in the east direction or the west direction are equalized. By doing so, the deviation of the beam landing is minimized as a whole, and the color purity can be improved.

However, in the recently developed ultra-large color picture tube, the aspect ratio of the phosphor screen is 16 :.
Since the screen is horizontally long at 9, the deflection angle in the diagonal direction is closer to the horizontal axis as compared with a normal color picture tube having an aspect ratio of 4: 3. As a result, in this super-large color picture tube, the amount of deflection in the vertical axis direction becomes relatively smaller than in a normal color picture tube, and the vertical velocity component vy of the electron beam shown in FIG. 7A becomes smaller. , Basic left rotation beam landing deviation is reduced. However, when the internal magnetic shield 12a having the V-shaped notch 16 formed on the short side shown in FIG. 8 is used in this super-large color picture tube, the distance from the electron gun to the phosphor screen is the same as the conventional one. Since the size is almost the same as that of the color picture tube, the trapezoidal beam landing deviation shown in FIG. 10 remains.
On the other hand, even if the internal magnetic shield without the V-shaped notch 16 is used, the deviation of the trapezoidal beam landing cannot be eliminated. Therefore, even if the rotation component of the landing is equal to that of the platform, it is impossible to totally minimize the deviation of the beam landing.

The ultra-large color picture tube having a horizontally long screen having an aspect ratio of 16: 9 is intended for a high-definition television, and the arrangement pitch of the phosphor layers of the phosphor screen is 0.5 to 0. The size is reduced to 0.6 mm, and the landing margin of the electron beam is extremely small at 30 to 40 μm. Therefore, for this high-definition ultra-large color picture tube with a horizontally long screen, even if an internal magnetic shield is placed, the electron beam will not land correctly on a given phosphor layer unless the effect of geomagnetism is minimized. , The color purity is greatly deteriorated.

The influence of the external magnetic field such as the earth's magnetism on the beam landing increases as the size of the color picture tube increases. For example, in the case of an ultra-large tube of about 36 inches, the distance from the electron gun to the phosphor screen or the distance from the center of the screen to the outermost circumference is about 1.6 times that of the 21-inch color picture tube. The amount of beam movement is about 2.5 times. Further, the distance between the phosphor screen and the shadow mask is increased, and the movement of the electron beam is further increased accordingly.

Actually, in Japan, as a result of measuring the deviation of the beam landing of a 36-inch type color picture tube in which an internal magnetic shield is arranged, when the color picture tube is oriented from south to north, it is about 50 μm and west. It was observed that the color purity was significantly deteriorated by moving about 60 μm in the east direction.

[0018]

As described above, in the conventional color picture tube, since the electron beam is shielded from the external magnetic field such as the earth magnetism, the inner magnetic shield is arranged inside the large diameter portion of the funnel. There is. However, the internal magnetic shield having a substantially rectangular trapezoidal basic structure cannot sufficiently shield the external magnetic field such as the earth's magnetism, resulting in deviation of the beam landing. In particular, with regard to a horizontally long, ultra-large high-definition color picture tube whose aspect ratio of the phosphor screen is 16: 9, the influence of the external magnetic field is different from that of the conventional color picture tube with an aspect ratio of 4: 3, and Since the landing margin is extremely small, there is a problem that the color purity is significantly deteriorated even if the internal magnetic shield is arranged.

The present invention has been made in view of the above problems, and reduces the deviation of the beam landing due to an external magnetic field such as the earth's magnetism so that not only a normal color picture tube but also the aspect ratio of the phosphor screen can be improved. It is an object of the present invention to obtain good landing characteristics even for a super large high-definition color picture tube that is large and has a small beam landing margin.

[0020]

SUMMARY OF THE INVENTION A mask main body and a mask main body having an envelope composed of a substantially rectangular panel and a funnel-shaped funnel, facing a phosphor screen formed on the inner surface of the panel. A substantially rectangular shadow mask consisting of a mask frame attached to the peripheral part of the is disposed, and a substantially rectangular trapezoidal hollow magnetic shield located inside the large diameter part of the funnel is attached to the mask frame. In a color picture tube, the length of the short side of the magnetic shield is longer than that of the long side, and the small-diameter opening-side end of the short side is extended in the direction of extension of the short side. It was formed in a protruding structure.

[0021]

As described above, the length of the short side portion of the substantially rectangular trapezoidal hollow magnetic shield is made longer than the length of the long side portion so that the small-diameter opening-side end portion of the short side portion is When projected in the direction of extension of the short side, when the color picture tube is installed in the east or west direction, the short side protrudes toward the small-diameter opening side, causing the electron beam to pass through the barrel inside the magnetic shield. The magnetic field shape is weakened. As a result, the vertical axis component By of the magnetic flux B can be reduced, and the vertical axis component By of the magnetic flux B can be reduced.
The deviation of the trapezoidal beam landing due to the velocity component vz of the electron beam in the tube axis direction can be reduced.
On the other hand, when installed in the north or south direction, the component B y of the magnetic flux B in the vertical axis becomes small, and the correction for the basic left or right rotation beam landing deviation becomes small, but the aspect ratio of the phosphor screen is In a large color picture tube, correction for its basic left or right rotating beam landing offset is less necessary. As a result, a color picture tube with a small deviation of the beam landing is obtained as a whole, and the color purity can be improved.

[0022]

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

FIG. 1A shows a color picture tube which is an 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 is blue, green or green. A phosphor screen 3 composed 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 so as to face the phosphor screen 3. The shadow mask 4 is composed of a substantially rectangular mask body 5 in which a large number of electron beam passage holes are formed, and a substantially rectangular mask frame 6 having an L-shaped cross section attached to the peripheral portion of the mask body 5. . On the other hand, in the neck 7 of the funnel 2, an electron gun 9 for emitting a three electron beam 8 is arranged. Further, inside the large-diameter portion 13 of the funnel 2, an internal magnetic shield 20 for shielding the three-electron beam 8 emitted from the electron gun 9 from an external magnetic field such as geomagnetism is arranged.

As shown in FIG. 1 (b), the internal magnetic shield 20 is formed in a substantially rectangular trapezoidal shape, and its large diameter opening side is directly or indirectly attached to the mask frame.
The small-diameter portion opening 21 side is located on the electron gun side. In particular, in the internal magnetic shield 20 of this example, the length of the short side portion 22 located in the horizontal axis (x axis) direction is the long side portion located in the vertical axis (y axis) direction.
Longer than 23, the end portion of the short side portion 22 on the small diameter portion opening 21 side protrudes in the extension direction of the short side portion 22 to form a protruding portion 24.

By the way, when the internal magnetic shield 20 is constructed as described above, in both cases where the color picture tube is installed in the east or west direction and in the north or south direction, The landing deviation can be reduced, and the color picture tube can display an image with good color purity regardless of the installation direction.

That is, when the color picture tube is installed in the east or west direction, as shown in FIG. 2 (a), of the horizontal component of the geomagnetism, as shown by a broken line 25, the short length of the internal magnetic shield 20 is short. Small-diameter part opening 21 of side part 22 Projection part 24 on the end side
The magnetic flux B passing through is attracted to the protrusion 24 and is emitted to the inside of the internal magnetic shield 20. Since the discharge position is apart from the long side portion 23, the discharge position goes straight without being attracted to the long side portion 23. Therefore, the vertical component By of the magnetic flux By
Becomes almost zero, and the deviation of the trapezoidal beam landing due to the vertical component By of the magnetic flux and the tube axial component vz of the electron beam can be eliminated.

When the color picture tube is installed northward or southward, most of the tube axial component Bz of the magnetic flux B is the protruding portion of the short side portion 22, as shown in FIG. 2B. It is forced in the direction of 24 (x-axis direction) and is not attracted to the long side portion 23. On the other hand, the horizontal component Bx of the magnetic flux B does not affect the deviation of the beam landing. Therefore, if the vertical component By of the magnetic flux B is reduced, the deviation of the left or right rotation beam landing due to the tube axis component of the electron beam can be almost eliminated. In this case, the basic left or right landing displacement due to geomagnetism is small because the vertical deflection amount is small and the vertical velocity component vy of the electron beam is small when the aspect ratio of the phosphor screen is horizontally long. Become. When the landing displacement of the left or right rotation is reduced in this way, the margin of design and manufacture is increased, and as a result, a color picture tube with good color purity can be obtained.

Next, another embodiment will be described.

In the above embodiment, the tip edge of the projecting portion at the small diameter opening side end portion of the short side portion of the internal magnetic shield is formed into a straight line parallel to the vertical axis. The body 20 is such that the center of the opening side end portion of the small-diameter portion 21 of the short side portion 21 is long-projected in the extension direction of the short-side portion 21, and the tip of the projecting portion 24 is triangular.

When such an internal magnetic shield 20 is used,
If the color picture tube is installed facing north or south,
Similar to the above embodiment, but when installed in the east direction, for example, as shown in FIG. 4, of the horizontal component Bx of the geomagnetism, the short side portion of the internal magnetic shield 20 is indicated by the broken line 25.
The magnetic flux passing through the protruding portion 24 at the end portion of the small diameter portion opening 21 side is attracted to the top portion of the protruding portion 24, is emitted to the inside of the internal magnetic shield 20, and the pin cushion is provided on the small diameter portion opening side. Form a magnetic field of shape. This pincushion type magnetic field has a function of canceling out the barrel type magnetic field inside the internal magnetic shield 20, totally reduces the vertical component By of the magnetic flux B, reduces the deviation of the trapezoidal beam landing, and reduces the color. A color picture tube with good purity can be obtained.

[0031]

[Effects of the Invention] The substantially rectangular shape which is attached to the mask frame of the substantially rectangular shadow mask arranged so as to face the phosphor screen formed on the inner surface of the substantially rectangular panel and is located inside the large-diameter portion of the funnel. In the trapezoidal hollow magnetic shield, the length of the short side is longer than the length of the long side, and the small-diameter opening-side end of the short side is the extension direction of the short side. When the color picture tube is installed eastward or westward, the protruding portion weakens the barrel-shaped magnetic field shape inside the magnetic shield through which the electron beam passes. As a result, the vertical axis component By of the magnetic flux density B
It is possible to reduce the deviation of the trapezoidal beam landing due to the vertical component By and the electron beam velocity component vz of the electron beam. On the other hand, when it is installed northward or southward, the component B y of the magnetic flux B in the vertical axis becomes small, and the correction for the basic landing displacement of left or right rotation becomes small, but the aspect ratio of the phosphor screen is large. In a picture tube, correction for its basic left or right rotation landing offset is less necessary. As a result, the landing deviation can be reduced as a whole, and a color picture tube with good color purity can be obtained.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing a configuration of a color picture tube which is an embodiment of the present invention, and FIG. 1 (b) is a diagram showing a structure of an internal magnetic shield thereof.

FIGS. 2A and 2B are views for explaining the action of the internal magnetic shield.

FIG. 3 is a diagram showing the structure of an internal magnetic shield of another embodiment of the present invention.

FIG. 4 is a view for explaining the action of the internal magnetic shield.

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

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

7 (a) and 7 (b) are views for explaining the action of the internal magnetic shield.

FIG. 8 is a view showing a structure of a conventional internal magnetic shield in which a V-shaped cut is formed on a short side portion.

9 (a) and 9 (b) are views for explaining the action of the internal magnetic shield.

FIG. 10 is a diagram illustrating a landing shift that occurs in the case of a conventional internal magnetic shield having a V-shaped cut formed in a short side portion.

[Explanation of symbols]

 1… Panel 2… Funnel 3… Phosphor screen 4… Shadow mask 5… Mask body 6… Mask frame 9… Electron gun 20… Internal magnetic shield 21… Small diameter opening 22… Short side 23… Long side Part 24 ... Projection

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoyuki Makino 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Electronics Engineering Co., Ltd.

Claims (1)

[Claims] 1. An envelope having a substantially rectangular panel and a funnel-shaped funnel, which faces a mask screen and a peripheral portion of the mask body facing a phosphor screen formed on the inner surface of the panel. A color picture tube in which a substantially rectangular shadow mask consisting of an attached mask frame is arranged, and a substantially rectangular trapezoidal hollow magnetic shield located inside the large diameter part of the funnel is attached to the mask frame. In the above-mentioned magnetic shield, the length of the short side portion is longer than the length of the long side portion, and the small-diameter opening-side end portion of the short side portion projects in the extension direction of the short side portion. Color picture tube characterized by.