JP2000165902A - Degaussing method for color picture tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degaussing method for color picture tube capable of uniform and stable degaussing without complicating a degaussing device. SOLUTION: Concerning the degaussing method for color picture tube with which the magnetization of a magnetic member is removed by supplying an alternative attenuated waveform current to a degaussing coil 40, the alternative attenuated waveform current is supplied to the degaussing coil 40 while relatively moving the degaussing coil 40 and a color picture tube so that the degaussing coil 40 can cross on the front face of a panel 3 in the direction orthogonal to a tube axis, and the alternative attenuated waveform current is supplied to the degaussing coil 40 so that the alternative attenuated waveform current can become the minimum value at the position where the central axis of this degaussing coil 40 is closest to the tube axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for degaussing a color picture tube, and more particularly to a method for degaussing a color picture tube which is effective when applied to a process for manufacturing a color picture tube.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a color picture tube has a panel 3 provided with a skirt portion 2 around an effective portion 1, and a funnel-shaped panel joined to the skirt portion 2 of the panel 3. It has a vacuum envelope composed of a funnel 4 and deflects three electron beams 7B, 7G, 7R emitted from an electron gun 6 disposed in a neck 5 of the funnel 4 to a deflection mounted outside the funnel 4. It is deflected by the magnetic field generated by the yoke 8 and horizontally and vertically scans a phosphor screen 9 composed of a three-color phosphor layer provided on the inner surface of the effective portion 1 of the panel 3 to form a structure for displaying a color image. ing.

In such a color picture tube, an opening is formed inside the panel 3 so as to oppose and approach the phosphor screen 9 to select the three electron beams 7B, 7G, 7R incident on the three-color phosphor layer. Mask body 11 and this mask body 1
A shadow mask 13 composed of a mask frame 12 attached to the periphery of the mask frame 12 is supported by engaging an elastic support 14 attached to the mask frame 12 with a stud pin 15 provided on the panel 3. I have. Further, an internal magnetic shield 16 for shielding geomagnetism is attached to the mask frame 12 and disposed inside the funnel 4. Further, on the outside of the skirt portion 2 of the panel 3,
A reinforcing band 17 for preventing implosion of the vacuum envelope is attached. Usually, the shadow mask 13, the internal magnetic shield 16, and the reinforcing band 17 are made of a magnetic material.

Therefore, even if the color picture tube is manufactured with high accuracy as designed, the magnetic members disposed inside and outside the envelope are magnetized by an external magnetic field such as terrestrial magnetism, so that the three electron beams 7B and 7G are emitted. , 7R, the beam landing on the three-color phosphor layer shifts, and the color purity deteriorates.

[0005] In order to eliminate the deviation of beam landing due to the magnetization of the magnetic member, the color picture tube is usually used at the time of inspection for inspecting various characteristics after manufacturing or when the color picture tube is assembled into a set. Is demagnetized to remove the magnetization.

As a typical demagnetizing method, there is the following method.

One of them is, as shown in FIG. 4, a demagnetizing coil 20 provided on the front of the panel 3 with respect to the color picture tube 19.
Is fixed to the degaussing coil 20, as shown in FIG.
This is a method in which an alternating decay waveform current 21 in which an alternating current whose polarity changes gradually attenuates so as to have a symmetrical waveform as much as possible is supplied, and the alternating decay waveform current 21 is supplied to demagnetize by a magnetic field generated by the degaussing coil 20.

The other is to dispose a degaussing coil 20 on the front surface of the panel 3 and supply an alternating current 22 having a constant waveform to the degaussing coil 20 as shown in FIG.
In this method, the magnetic field generated by the degaussing coil 20 with respect to the color picture tube 19 is gradually demagnetized by gradually moving the degaussing coil 20 toward the front of the panel 3 as shown by 3.

As a specific application example of such a degaussing method, FIG. 7 shows a method performed before or during an inspection in a color picture tube manufacturing process. Color picture tube 1
In the manufacturing process, a check is made as to whether the device operates normally while being conveyed by the conveyor 25, and the degaussing coil 20 is mounted on the panel of the color picture tube 19 that moves continuously or in a continuous manner. 3 is installed on the front side of the panel 3 so as to be substantially parallel to the demagnetizing coil 2.
0 is supplied by supplying the alternating decay waveform current 21 shown in FIG.

In the degaussing performed while the color picture tube 19 is conveyed in this manner, degaussing is performed when the color picture tube 19 comes to the position where the degaussing coil 20 is installed. Inspection of such as becomes possible. Therefore, as shown in FIG. 8, the polarity of the alternating magnetic field 26 generated by the supply of the alternating attenuated waveform current changes so as to have a symmetrical waveform as much as possible, and the alternating magnetic field 26 attenuates with the attenuation of the alternating attenuated waveform current. Αt (demagnetization time) until the waveform and magnetic field strength become minimum
In contrast, it is necessary to make the slope β of the attenuation of the waveform of the alternating magnetic field 26 as gentle as possible. That is, in order to perform sufficient demagnetization, it is necessary to set the demagnetization time αt to be long.

[0011]

As described above, a color picture tube has a magnetic member disposed inside and outside an envelope.
These magnetic members are magnetized by an external magnetic field such as terrestrial magnetism and change the trajectory of the electron beam. The beam landing on the three-color phosphor layer shifts and the color purity deteriorates. When assembling, demagnetization is performed to remove the magnetization of the magnetic member. The degaussing method is to fix a degaussing coil to the front of the panel of the color picture tube, and to supply an alternating attenuated waveform current in which the alternating current whose polarity changes gradually to the degaussing coil as much as possible has a symmetrical waveform. There is a method of arranging a degaussing coil on the front side of the panel and gradually moving the degaussing coil away from the front side of the panel while supplying an alternating current having a constant waveform to the degaussing coil.

However, such a degaussing method has the following problems. That is, as shown in FIG. 9, the magnetic field 26 generated by the degaussing coil 20 becomes weaker as the distance from the degaussing coil 20 increases. Therefore, when the degaussing coil 20 is arranged in front of the panel, a strong magnetic field is generated near the periphery of the panel near the degaussing coil 20, but a relatively weak magnetic field is generated near the center 30 of the panel far from the degaussing coil 20. In addition, the magnetic members disposed inside and outside the envelope of the color picture tube cannot be uniformly or sufficiently demagnetized, making it difficult to accurately inspect the color purity and the like. In addition, if the demagnetization time is set to be long in order to perform sufficient demagnetization, there is a problem that the index of the manufacturing process is reduced and the productivity is affected.

As a method for solving this, there are methods for increasing the demagnetizing current and improving the shape of the degaussing coil. In particular, for improving the shape of the degaussing coil, as shown in FIG. 10, a method of drawing the degaussing coil 20 near the center of the panel 3 of the color picture tube 19 to strengthen the magnetic field near the center of the panel can be considered.

However, if the demagnetizing current is increased and the shape of the degaussing coil is complicated as shown in FIG. 10, an alternating magnetic field having an asymmetric component is easily generated from the degaussing coil. Magnetize magnetic members disposed inside and outside the envelope of the color picture tube. FIG.
In the case where the degaussing coil 20 is routed as shown in FIG. 0 and degaussed while transporting the color picture tube 19 as shown in FIG. 6, for example, the degaussing coil 20 is moved toward the back side (outer surface of the funnel) of the color picture tube 19. The arrangement is not suitable, and even if it is arranged on the front side of the panel, there is a problem that it hinders visual inspection of the screen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made without complicating the degaussing device.
An object of the present invention is to provide a color picture tube degaussing method capable of stably performing uniform and sufficient degaussing.

[0016]

SUMMARY OF THE INVENTION A degaussing coil is arranged outside the envelope of a color picture tube comprising a panel and a funnel-shaped funnel joined to the panel, and an alternating decaying waveform current is supplied to the degaussing coil. In the method of degaussing a color picture tube, which removes the magnetization of magnetic members disposed inside and outside of the envelope by performing the above operation, the degaussing coil and the color image receiving device are arranged such that the degaussing coil crosses the front surface of the panel in a direction orthogonal to the tube axis. An alternating-decay waveform current is supplied to the degaussing coil while moving relatively to the tube, and the alternating-current decaying waveform current is minimized at a position where the center axis of the degaussing coil is closest to the tube axis. Was removed.

Further, a degaussing coil is arranged outside the envelope of a color picture tube composed of a panel and a funnel-shaped funnel joined to the panel, and an alternating attenuated waveform current is supplied to the degaussing coil to provide an external coil. In a method of degaussing a color picture tube, which removes the magnetization of a magnetic member disposed inside and outside the enclosure, the degaussing coil and the color picture tube are positioned so that the degaussing coil crosses the front surface of the panel in a direction perpendicular to the tube axis. Supplies the alternating decaying waveform current to the degaussing coil while moving, and stops the relative movement at the position where the center axis of the degaussing coil is closest to the tube axis. Thus, the magnetization of the magnetic member was removed.

[0018]

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

FIG. 1 shows a demagnetization method which is carried out before the inspection in the color picture tube manufacturing process, which is one mode of the invention. In the inspection step, the color picture tube 19 is carried by a conveyor 25 driven intermittently, and the degaussing coil 40 is moved by the color picture tube 1 carried by the conveyor 25.
9 is installed on the front side of the panel 3 so as to traverse in a direction orthogonal to the tube axis and to be substantially parallel to the panel 3. The degaussing is performed by supplying the degaussing coil 40 with an alternating attenuated waveform current 41 in which an alternating current whose polarity changes gradually as much as possible as shown in FIG.

In this embodiment, in particular, the supply of the alternating decaying waveform current 41 to the degaussing coil 40 is performed with respect to the center position S0 of the degaussing coil 40, as shown in FIGS. Is closest, and the tube axis comes to the center position S0 of the degaussing coil 40, where Δt is the time until the tube axis (Z axis) (coincident with the center of the panel 3) comes to the center position S0 of the degaussing coil 40. The energization of the alternating attenuated waveform current 41 is started from the position S-Δt in front, and the conveyor 25 is stopped when the tube axis reaches the center position S0 of the degaussing coil 40 after the time Δt, and the alternating attenuated waveform current 41 is generated. A decaying operation is performed by supplying an αt alternating decay waveform current 41 for a time required for the decay to reach a minimum value.

The position S-.DELTA.t at which the supply of the alternating attenuated waveform current 41 is started is preferably set before the tube axis of the color picture tube 19 crosses the rear coil portion 42 in the moving direction of the color picture tube 19. Is done.

The magnitude of the alternating attenuated waveform current 41 flowing through the degaussing coil 40 when the tube axis of the color picture tube 19 reaches the center position S0 of the degaussing coil 40 depends on the color picture tube 1
The size is set so that the magnetization of the magnetic members disposed inside and outside the envelope 9 can be sufficiently removed.

When the demagnetization is performed by supplying the alternating decaying waveform current 41 to the degaussing coil 40 as described above, a strong magnetic field cannot be applied conventionally, and the strong magnetic field distribution also occurs near the center of the panel 3 having a weak magnetic field distribution. can do. And panel 3
A strong magnetic field can also be applied near the periphery of. Therefore, by performing degaussing as described above, uniform and sufficient degaussing can be stably performed without complicating the degaussing device, such as the power supply for supplying the degaussing coil 40 and the alternating attenuated waveform current 41.

In the above embodiment, the degaussing performed before the inspection of the color picture tube manufacturing process has been described. However, in the present invention, the color picture tube is conveyed by the conveyor for the inspection of the color picture tube manufacturing process. The present invention can also be applied to a case where degaussing is performed during the transportation.

The present invention can be applied not only to the stage before and during the inspection of the color picture tube manufacturing process, but also to any case where degaussing is performed while being transported by a conveyor.

[0026]

As described above, the alternating decaying waveform current is supplied to the degaussing coil while relatively moving the degaussing coil and the color picture tube so as to cross the direction perpendicular to the tube axis of the color picture tube. When degaussing is performed by supplying an alternating decaying waveform current to the degaussing coil so that the center axis of the degaussing coil is closest to the tube axis and the alternating decaying waveform current becomes the minimum value,
Conventionally, a strong magnetic field cannot be applied, and a strong magnetic field can also be applied near the center of a panel having a weak magnetic field distribution. In addition, a strong magnetic field can be applied near the periphery of panel 3. As a result, uniform and sufficient degaussing can be stably performed without complicating the degaussing device.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a degaussing method performed in a stage prior to an inspection in a color picture tube manufacturing process according to an embodiment of the present invention.

FIG. 2 is a diagram showing an alternating attenuated waveform current supplied to a degaussing coil installed on a conveyor for conveying a color picture tube in the inspection of the color picture tube manufacturing process.

FIG. 3 is a diagram showing a configuration of a color picture tube.

FIG. 4 is a layout diagram of a degaussing coil shown for explaining a typical degaussing method for a color picture tube.

FIG. 5 is a diagram of an alternating attenuated waveform current supplied to a degaussing coil used in one of the typical degaussing methods for a color picture tube.

FIG. 6 is a diagram of an alternating current supplied to another degaussing coil used in another typical degaussing method for a color picture tube.

FIG. 7 is a view for explaining a conventional degaussing method performed before or during an inspection in a color picture tube manufacturing process.

FIG. 8 is a diagram of an alternating magnetic field generated by a degaussing coil due to the supply of the alternating decay waveform current.

FIG. 9 is a diagram for explaining a problem of a conventional degaussing method.

FIG. 10 is a diagram showing an improved shape of a degaussing coil that solves the problems of the conventional degaussing method.

[Explanation of symbols]

 3: Panel 19: Color picture tube 40: Degaussing coil 41: Alternating attenuation waveform current

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masakuni Kosoegawa 1-9-2 Harara-cho, Fukaya-shi, Saitama Prefecture Inside the Toshiba Fukaya Electronics Factory (72) Inventor Yoshio Suzuki 1-9-9, Harara-cho, Fukaya-shi, Saitama No. 2 F-term in Toshiba Fukaya Electronics Factory (reference) 5C060 CM04 CN03 CP04 CP11

Claims (2)

[Claims] 1. A degaussing coil is arranged outside an envelope of a color picture tube comprising a panel and a funnel-shaped funnel joined to the panel, and an alternating-decay waveform current is supplied to the degaussing coil. A degaussing method for a color picture tube for removing the magnetization of a magnetic member disposed inside and outside of an envelope, wherein the degaussing coil and the color image receiving device are arranged such that the degaussing coil crosses the front surface of the panel in a direction orthogonal to the tube axis. An alternating decay waveform current is supplied to the degaussing coil while relatively moving the tube, and the alternating decay waveform current is minimized at a position where the center axis of the degaussing coil is closest to the tube axis. A degaussing method for a color picture tube, comprising: removing magnetization of a magnetic member. 2. A degaussing coil is arranged outside an envelope of a color picture tube comprising a panel and a funnel-shaped funnel joined to the panel, and an alternating decaying waveform current is supplied to the degaussing coil. A degaussing method for a color picture tube for removing the magnetization of a magnetic member disposed inside and outside of an envelope, wherein the degaussing coil and the color image receiving device are arranged such that the degaussing coil crosses the front surface of the panel in a direction orthogonal to the tube axis. An alternating decay waveform current is supplied to the degaussing coil while moving relatively to the tube, and the relative movement is stopped at a position where the center axis of the degaussing coil is closest to the tube axis. A degaussing method for a color picture tube, wherein the magnetization of the magnetic member is removed so that the waveform current becomes a minimum value.