JPH10257512A - Method and device for degaussing cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate undesired magnetization of a cathode ray tube to which magnetic transfer is applied, while maintaining the correcting effect of a deviated orbit of a cathode ray so as not to lose or fluctuate the effect due to degaussing when a cathode ray tube monitor set is in use. SOLUTION: An AC attenuation magnetic field with an optional strength in an optional direction is applied to a cathode ray tube 7 by two pairs of coaxial coils 8A, 8B and 9A, 9B in an optional sequence to conduct degaussing. The AC attenuation magnetic field with an optional strength in an optional direction is applied to the cathode ray tube 7 which is degaussed through the above procedures as required by small sized coils 10A, 10B, 10C, 10D arranged in an optional position to conduct partially degaussing only to a specific member in the cathode ray tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube degaussing method and apparatus for efficiently degaussing members in a cathode ray tube in order to control the trajectory of a cathode ray in the cathode ray tube.

[0002]

2. Description of the Related Art FIG. 2 is a structural view of an internal metal member of a cathode ray tube having an aperture grill as a color selection electrode.
In the figure, 1 is an aperture grill, 2 and 3 are frames supporting the aperture grill 1, 2 is an H member,
3 are called V members. 4A, 4B, 4
C and 4D are springs for fixing the H member 2 and the V member 3 inside the face plate panel having the fluorescent screen, 5A, 5B, 5C and 5D are clips for correcting thermal expansion of the aperture grill member, and 6 is an internal magnetic shield. It is.

In a cathode ray tube, an internal magnetic shield 6 is provided in order to prevent a position at which the cathode ray reaches the fluorescent screen from being shifted from an initial target position by an external magnetic field. But,
In addition to the external magnetic field, the cathode ray trajectory may be shifted even in a zero magnetic field due to, for example, a mechanical displacement of the aperture grill 1 or a thermal deformation of the glass tube. Usually, a cathode ray tube in which the position of arrival of a cathode ray is deviated from a target position has a problem that color shift or reduction in luminance occurs.

On the other hand, in order to correct the deviation of the cathode ray from the target position to reach the fluorescent screen, the completed cathode ray tube is degaussed by applying a bias magnetic field by a ring coil surrounding the vicinity of the color selection electrode. A magnetic transfer method in which an alternating-current attenuating magnetic field is provided by a coil has been proposed (see JP-A-62-290034).

[0005]

As a method for correcting the deviation of the cathode ray from the target position to reach the phosphor screen, there are the following methods.
In addition to the above-mentioned example, there has been proposed a method of correcting a more complicated orbital deviation or a local orbital deviation by magnetizing a member of a cathode ray tube with an arbitrary bias magnetic field (Japanese Patent Laid-Open No. Hei 6-223724). Gazette).

[0006] By the way, it is possible to correct the displacement of the cathode ray trajectory at the stage of the cathode ray tube manufacturing process by magnetic transfer. However, when a set of cathode ray tube monitors is used, in order to enhance the external magnetic field shielding effect of the internal magnetic shield 6, Normally, demagnetization is performed. If the magnetization of the magnetic transfer is removed by this, the correction of the cathode ray trajectory shift becomes insufficient. Therefore, conventionally, the magnetization removed by demagnetization at the time of using the set had to be removed in advance during the process. That is, a demagnetization step for simulating demagnetization at the time of using the set is included in the magnetic transfer process, and the magnetizing operation has to be performed in consideration of obtaining a desired cathode ray trajectory correction effect after the demagnetization step.

[0007] Usually, in the degaussing method when using a cathode ray tube monitor set, a hand degauss is performed in which a person moves while passing an alternating current through a bar-shaped coil, and an alternating-current attenuating magnetic field is applied by a coil built in the set. There is Autodegauss. On the other hand, in the magnetic transfer process, as a demagnetization method that simulates these, a method of automatically moving the rod-shaped coil, a method of applying an AC attenuating magnetic field with a coil of the same type as Autodegauss, and a method of combining these methods Was used.

However, there has been a problem that the cathode ray trajectory fluctuates greatly due to demagnetization during use of the set, and that a desired magnetic transfer correction cannot be obtained. Here, the hand degauss mainly degausses the frame H member 2 of the aperture grill, and the auto degauss degauss the V member 3. However, the method of moving the rod-shaped coil and the method using the same type of coil as the autodegauss, which have been performed in the conventional magnetic transfer process, are insufficient in the demagnetization of the H member 2 and the V member 3, and the metal member has The above problem has arisen because the flow of the magnetic flux is different from that after demagnetization when the set is used.

The springs 4A, 4B, 4C and 4
If the coercive force of members that are not necessary for the desired magnetic transfer correction, such as D and the clips 5A, 5B, 5C, and 5D, is relatively large, the cause is that the local magnetization of these members is insufficiently removed. In some cases, the above problem occurred.

The present invention makes it possible to remove extra magnetization in a cathode ray tube without impairing the effect of correcting a cathode ray orbit shift caused by magnetic transfer.

[0011]

According to a method of degaussing a cathode ray tube according to the present invention, a metal member including a color selection electrode inside a cathode ray tube is applied with a magnetic field generator to apply an AC attenuating magnetic field in two or more arbitrary directions. , And demagnetize the metal member.

Further, the strength of the AC attenuation magnetic field is arbitrarily and independently changed.

Further, the AC attenuating magnetic field is applied in the left-right direction and the up-down direction toward the surface of the cathode ray tube.

In addition, an alternating-current attenuating magnetic field in an arbitrary direction is applied to a specific portion of the cathode-ray tube by a magnetic-field generation device comprising one or more small coils different from the above-described magnetic-field generation device. It is something to give.

[0015] Further, the portion for applying the AC attenuation magnetic field by the plurality of small coils is arbitrarily and independently changed.

Further, the strength of the AC attenuation magnetic field generated by the plurality of small coils is arbitrarily and independently changed.

Further, the degaussing apparatus for a cathode ray tube according to the present invention includes an alternating current attenuation magnetic field generating coil arranged around the cathode ray tube so as to provide two or more arbitrary alternating current attenuation magnetic fields.
And a small coil arranged near the cathode ray tube so as to apply an AC attenuation magnetic field different from the magnetic field of these coils to a specific metal member inside the cathode ray tube.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIG. In FIG. 1, a degaussing device for a cathode ray tube includes coils 8A and 8B arranged above and below the cathode ray tube 7 so as to apply an alternating-current attenuating magnetic field in a vertical direction toward the tube surface of the cathode ray tube 7; The coils 9A and 9B arranged on the left and right sides of the cathode ray tube 7 so as to apply an AC attenuation magnetic field in the left and right directions, and further, an arbitrary AC attenuation magnetic field is applied from the outside of the cathode ray tube to the vicinity of a spring or clip inside the cathode ray tube 7. Small coil 10A arranged,
It consists of 10B, 10C and 10D.

Here, coils 8A and 8B and coil 9A,
The order in which the AC attenuation magnetic field is applied by 9B and the respective magnetic field strengths, the location of the coils 10A, 10B, 10C, and 10D and the strength and direction of the AC attenuation magnetic field by them are determined, and demagnetization is performed. As a result, unnecessary magnetization of the metal member inside the cathode ray tube 7 is removed without impairing the effect of the magnetic transfer correction.

Here, the cathode ray tube 7 which has been subjected to magnetic transfer under the following conditions is used. This is, as shown in FIG. 3, a solid line 11 which is a target position of the cathode ray reaching the phosphor screen.
On the other hand, this is a condition for the purpose of correcting a state in which the cathode ray trajectory is displaced in the opposite direction above and below the tube surface as indicated by a broken line 12. DC bias magnetic field Tube axis direction, direction from electron gun to face panel 2 mT AC attenuating magnetic field 70 mT in vertical direction toward tube surface

The cathode ray tube 7 is demagnetized according to the following procedure and conditions. Procedure 1 An AC attenuated magnetic field of 10 mT is applied in the left-right direction toward the tube surface. Procedure 2 Apply an AC attenuation magnetic field of 10 mT in the vertical direction toward the tube surface.

As a result, the position at which the cathode ray reaches the phosphor screen in the cathode ray tube 7 changes as shown in Table 1 before magnetizing by magnetic transfer.

[0023]

[Table 1] Position on the phosphor screen Variation of the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right corner 7 μm rightward toward the tube surface Upper left corner 6 μm rightward toward the tube surface 5 μm to the left and lower left 7 μm to the left toward the tube surface

When hand degauss and auto degauss are performed on the cathode ray tube 7 in the state shown in Table 1, the position of the cathode ray reaching the phosphor screen in the cathode ray tube 7 is smaller than that before magnetization by magnetic transfer. It looks like 2.

[0025]

[Table 2] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right corner 5 μm rightward toward the tube surface Upper left corner 6 μm rightward toward the tube surface 7 μm to the left and lower left 6 μm to the left toward the tube surface

As shown in Tables 1 and 2, in the present embodiment, the degaussing at the time of using the cathode ray tube monitor set, that is, the cathode ray as shown in FIG. It is possible to sufficiently correct the orbital deviation. Also, it can be seen that the fluctuation of the cathode ray trajectory before and after the degaussing at the time of using the set is very small. Here, the above procedure 1 involves hand degauss,
Although it can be said that the procedure 2 simulates an autodegauss, in order to stably obtain a desired cathode ray trajectory, the order in which the AC attenuating magnetic field is applied and the combination of their strengths are important.

Embodiment 2 FIG. Next, a second embodiment to which the apparatus of FIG. 1 is applied will be described. Here, the cathode ray tube 7 has been subjected to magnetic transfer under the same conditions as in the first embodiment, but the coercive force of the spring material is larger than that used in the first embodiment.

The cathode ray tube 7 is demagnetized in the following procedure and under the same conditions as in the first embodiment. Procedure 1 An AC attenuated magnetic field of 10 mT is applied in the left-right direction toward the tube surface. Procedure 2 Apply an AC attenuation magnetic field of 10 mT in the vertical direction toward the tube surface.

Further, as a procedure 3, the small coil 10A,
10B, 10C, and 10D are arranged on the tube surface at a position near the tip of the spring, and these give an AC attenuating magnetic field of 60 mT in the tube axis direction.

As a result, the position at which the cathode ray reaches the phosphor screen in the cathode ray tube 7 changes as shown in Table 3 as compared with before the magnetization is performed by magnetic transfer.

[0031]

[Table 3] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right corner 6 μm rightward toward the tube surface Upper left corner 6 μm rightward toward the tube surface 7 μm to the left and lower left 5 μm to the left toward the tube surface

When hand degauss and auto degauss are performed on the cathode ray tube 7 in the state shown in Table 3, the position of the cathode ray reaching the phosphor screen in the cathode ray tube 7 is smaller than that before magnetization by magnetic transfer. It looks like 4.

[0033]

[Table 4] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right corner 6 μm rightward toward the tube surface Left upper edge 5 μm rightward toward the tube surface 7 μm to the left and lower left 6 μm to the left toward the tube surface

As shown in Tables 3 and 4, also in this embodiment, regardless of whether or not to perform degaussing when using the cathode ray tube monitor set, that is, whether to perform hand degauss and auto degauss, a cathode ray as shown in FIG. It is possible to sufficiently correct the orbital deviation. Also, as in the first embodiment,
The fluctuation of the cathode ray trajectory before and after degaussing when using the set is very small. Here, the procedure 3 is a local demagnetization performed because the coercive force of the spring is large and the magnetization of this portion is difficult to remove only by the procedures 1 and 2. When the clip is made of a high coercive force material, the same demagnetizing effect can be obtained by setting the coil arrangement position on the tube surface near the clip in step 3.

Next, conditions required for the AC attenuation magnetic field generated in the present invention will be described. Table 5 shows that the order in which the AC attenuating magnetic field is applied is reversed from that in the above-described first embodiment, that is, in the vertical direction and the left-right direction with respect to the tube surface, and the other conditions are the same as those in the first embodiment. In FIG. 7, the position of the cathode ray reaching the phosphor screen is compared with that before magnetization by magnetic transfer.

[0036]

[Table 5] Position on the phosphor screen Amount of change in the arrival position of the cathode ray on the phosphor screen before magnetic transfer and after demagnetization Upper right upper right 7 μm to the right toward the tube surface Left upper left 2 μm to the left toward the tube surface 1 μm to the left, lower left 5 μm to the left, toward the tube surface

As shown in Table 5, in this case, the demagnetization when using the cathode ray tube monitor set, that is, the correction of the cathode ray trajectory deviation as already seen in FIG. 3 before the hand degauss and the auto degauss are performed is impossible. It is in a state. Further, in the first embodiment, the procedure 2 is not performed, that is, an AC attenuating magnetic field is applied only in the left-right direction toward the tube surface, and the other conditions are the same as in the first embodiment. Becomes

Next, the procedure 1 is not performed in the first embodiment, that is, the AC attenuation magnetic field is applied only in the vertical direction toward the tube surface, and the other conditions are the same as those in the first embodiment. Table 6 compares the position of the cathode ray reaching the phosphor screen with that before the magnetization by magnetic transfer.

[0039]

[Table 6] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right right 13 μm rightward toward the tube surface Left upper end 13 μm rightward toward the tube surface 9 μm to the left and lower left 10 μm to the left toward the tube surface

When hand degauss and auto degauss are performed on the cathode ray tube 7 in the state shown in Table 6, the position of the cathode ray reaching the phosphor screen in the cathode ray tube 7 is smaller than that before magnetization by magnetic transfer. It looks like 7.

[0041]

[Table 7] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right corner 6 μm rightward toward the tube surface Left upper corner 6 μm rightward toward the tube surface Left 5μm Left bottom 5μm Left

From the comparison between Table 6 and Table 7, the difference between the two is clearly large. That is, since the fluctuation of the cathode ray trajectory before and after the degaussing is performed when the set is used, this method is unsuitable as the degaussing method in the magnetic transfer process.

Next, in the first embodiment, only the intensity of the AC attenuation magnetic field is changed, and other conditions are the same as those in the first embodiment.
The same case as described above will be described. Here, considering the cathode ray trajectory correction amount fluctuation rate due to magnetic transfer before and after performing the hand degauss and the auto degauss based on the values before the execution, the case of the first embodiment is as follows.
%, The variation is very small and stable. Table 8 shows the results of examining the same fluctuation rate when only the intensity of the AC attenuation magnetic field is changed in the first embodiment as described above. However, the intensity of the AC attenuation magnetic field is as shown below. Condition 1 AC attenuated magnetic field 5mT on the tube surface, 5mT in the vertical direction of the tube condition 2 AC attenuated magnetic field 5mT in the horizontal direction on the tube surface, 10mT in the vertical direction of the tube condition 3 AC attenuated magnetic field 15mT on the tube surface, 5mT in the vertical direction of the tube Condition 5 AC attenuated magnetic field 5mT on the tube surface, 5mT in the vertical direction

[0044]

[Table 8] Condition The variation rate of the amount of correction of the cathode ray trajectory due to magnetic transfer before and after the execution of hand degauss and auto degauss Condition 1 94% Condition 2 70% Condition 3 66% Condition 4 42% Condition 5 54%

From Table 8, it can be seen that in any of the methods in this case, the fluctuation of the cathode ray trajectory before and after the demagnetization during use of the set is large. Further, if the AC attenuation magnetic field strength is further reduced than the above condition, the demagnetization becomes insufficient, and if it is increased, the magnetic transfer correction becomes insufficient.

As described above, the magnetic flux density in the frame H member and the V member is controlled by the combination of the order in which the AC damping magnetic field is applied and the strength, whereby the flow of the magnetic flux in the entire metal member, that is, the pattern of magnetic transfer correction is determined. You can see that. Further, both the H member and the V member need to be demagnetized evenly, but the strength of the AC attenuation magnetic field must not be too strong or too weak. Therefore, the conditions described in the first embodiment can be said to be the optimum demagnetizing conditions.

Next, in the case where the procedure 3 is not performed in the second embodiment, and the other conditions are the same as those in the second embodiment, the arrival position of the cathode ray on the fluorescent screen of the cathode ray tube 7 is determined before the magnetization by the magnetic transfer. Table 9 shows a comparison with.

[0048]

[Table 9] Position on the phosphor screen The amount of change in the arrival position of the cathode ray on the phosphor screen before and after magnetic transfer and after demagnetization Upper right right 10 μm rightward toward the tube surface Left upper end 13 μm rightward toward the tube surface 8 μm to the left, lower left 5 μm to the left, toward the tube surface

In this case, the magnetic transfer correction effect varies depending on the position on the tube surface. In this case, the fluctuation of the cathode ray trajectory before and after the degaussing is performed when the set is used is large. Therefore, when the spring or the clip is made of a material having a high coercive force, the method of the second embodiment is appropriate.

Further, in the first embodiment, by changing the direction and strength of the AC attenuating magnetic field and the procedure for providing the same, effective demagnetization can be performed according to the purpose of magnetic transfer correction and the type of cathode ray tube. It is possible.

In the second embodiment, the purpose of the magnetic transfer correction and the cathode ray tube are improved by changing the size, shape, number, location, and the AC attenuation magnetic field strength of the small coils used for the local demagnetization in the procedure 3. The required demagnetizing effect can be obtained irrespective of the type, spring material and clip material.

[0052]

As described above, according to the method and apparatus for degaussing a cathode ray tube according to the present invention, the effects of magnetic transfer correction and unnecessary magnetization removal, which were conventionally difficult to achieve, can be achieved by the purpose of magnetic transfer and It can be obtained easily and simultaneously regardless of the type of cathode ray tube. This can be used to stabilize the effect of correcting the cathode ray trajectory by magnetic transfer.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a degaussing device according to the present invention.

FIG. 2 is a perspective view showing a metal member inside the cathode ray tube.

FIG. 3 is a diagram showing a state of a shift of an arrival position of a cathode ray on a tube surface which requires orbit control.

[Explanation of symbols]

1 aperture grille, 2 frame H members, 3
Frame V member, 4A, 4B, 4C, 4D spring, 5A, 5B, 5C, 5D clip, 6 internal magnetic shield, 7 cathode ray tube, 8A, 8B, 9A, 9B
AC attenuation magnetic field generating coils, 10A, 10B, 10C, 1
0D Small coil that generates an AC attenuation magnetic field.

Claims (7)

[Claims] 1. A magnetic field generator that applies an AC attenuating magnetic field in two or more arbitrary directions to a metal member including a color selection electrode inside a cathode ray tube in an arbitrary order to demagnetize the metal member. Characteristic method of degaussing a cathode ray tube. 2. The degaussing method for a cathode ray tube according to claim 1, wherein the intensity of the AC attenuation magnetic field is arbitrarily and independently changed. 3. The degaussing method for a cathode ray tube according to claim 1, wherein the alternating-current attenuating magnetic field is applied in the left-right direction and the up-down direction toward the tube surface of the cathode ray tube. 4. A magnetic field generator comprising one or more small coils different from the magnetic field generator of claim 1 for a cathode ray tube degaussed by the method according to claim 1. A method of degaussing a cathode ray tube, wherein an alternating-current attenuating magnetic field in an arbitrary direction is applied to a specific portion of the cathode ray tube. 5. The degaussing method for a cathode ray tube according to claim 4, wherein a portion for applying an AC attenuation magnetic field by a plurality of small coils is arbitrarily and independently changed. 6. The degaussing method for a cathode ray tube according to claim 4, wherein the intensity of the AC attenuation magnetic field generated by the plurality of small coils is changed arbitrarily and independently. 7. An AC attenuating magnetic field generating coil disposed around a cathode ray tube so as to provide an AC attenuating magnetic field in two or more arbitrary directions, and an AC attenuating magnetic field different from the magnetic fields of these coils is applied to the inside of the cathode ray tube. And a small coil disposed in the vicinity of the cathode ray tube so as to apply the specific metal member to the cathode ray tube.