KR100232138B1 - Manufacture of inner shield for color crt - Google Patents

Abstract

The present invention relates to the manufacture of a magnetic shield (INNER SHIELD) suitable for preventing the color purity degradation of the cathode ray tube generated by an external magnetic field in the color cathode ray tube, after forming a magnetic shield by forming a thin plate made of aluminum-killed steel The present invention relates to a method for producing a magnetic shield for a color cathode ray tube, characterized by annealing above a recrystallization temperature and subjecting to blackening.

Description

Manufacturing method of magnetic shield for color cathode ray tube (INNER SHIELD)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shield for color cathode ray tubes (INNER SHIELD), and more particularly to a method for manufacturing a magnetic shield suitable for preventing color purity degradation of cathode ray tubes caused by an external magnetic field.

In the color cathode ray tube, as shown in FIG. 1, a panel 1 having a fluorescent film formed on its inner surface and a funnel 2 coated with conductive graphite on its inner surface are sealed with a fusion glass in a furnace at about 450 ° C. An electron gun 3 for generating an electron beam 9 is mounted on the neck portion 7 of the funnel. A shadow mask 5, which is a color-selective electrode, is supported by the frame 6 inside the panel. A deflection yoke 8 is mounted on the outer circumferential surface to deflect the electron beam from side to side.

The color CRT configured as described above receives hot electrons from the cathode of the electron gun when the image signal is input to the electron gun, and the emitted electrons are accelerated and focused toward the panel by the voltage applied from each electrode of the electron gun.

At this time, the electrons are adjusted by the magnetic field of the deflection yoke 8 mounted on the neck of the panel, and the adjusted electron beam is scanned by the deflection yoke 8 to the inner surface of the panel. Color selection is performed while passing through the slots of the shadow mask coupled to the side frame, and the selected electron beam collides with each fluorescent film on the inner surface of the panel to emit light to reproduce the image signal.

When the electron beam passes through the slot of the shadow mask and reaches the fluorescent film, the geomagnetic shielding body (inner shield; INNER SHIELD) is located at the back of the frame where the shadow mask is combined to prevent deflection of the electron beam due to the influence of geomagnetism. 6) is attached.

The electron beam emitted from the electron gun 3 is deflected under the influence of the geomagnetism, and a phenomenon in which the electron beam 3 deviates from the original orbit occurs.

However, it is difficult to block the influence of the earth's magnetic field (hereinafter referred to as the "magnetic field") on the screen tube axis direction of the color cathode ray tube.

That is, the electron beam passing through the MASK lacks the correspondence to the horizontal magnetic field of the axial component, and thus the image beam is deteriorated due to the deviation of the electron beam from the orbit.

In order to solve this problem, the inner shield is attached to the back of the frame combined with the shadow mask when viewed from the panel side. As the shield material, a thin metal plate having soft magnetic current is used, and the thin inner shield is bonded to the frame. It is joined by a fixing pin.

At this time, since the inner shield 6 formed at a predetermined interval against the panel is made of a magnetic material, an external magnetic field flowing into the cathode ray tube flows through the inner shield as shown in FIGS. 2A and 2B to be generated inside the cathode ray tube. Reduce the external magnetic field

The inner shield is hot-rolled and cold-rolled by aluminum casting steel (AK steel) having a reduced carbon content with aluminum, followed by decarbonization to obtain a thin plate.

The color cathode ray tube manufacturer purchases the above-mentioned thin plate and manufactures an inner shield by drawing or forming.

Since the aluminum-kilted steel is pure iron, the magnetic permeability of magnetic flux flow within the inner shield is within 3000 and the coercive force is 1.5 Oe or less.

Since the degree of magnetic shielding is determined by the permeability, there is a limit to the characteristics of the inner shield that shields the external magnetic field.

As described above, due to the limitation of magnetic properties of the inner shield, the cathode ray tube is influenced by an external magnetic field so that the external magnetic field flowing into the cathode ray tube is concentrated at the corner portion as shown in FIG. 2A, and the magnetic field focused at the corner portion flows into the three-dimensional space. Because of the deflection of the electron beam is generated from the mis-resist, there is a problem that deteriorates the cathode ray tube color purity.

In addition, the inner shield manufactured by drawing or forming an integral form with a thin aluminum alloy steel sheet has severe mechanical deformation at the inner part of the inner shield, so that the magnetic properties at the deformed portion of the inner shield are greatly reduced. In addition, the magnetic properties of the inner shield as a whole are non-uniform, so that the deflection of the electron beam from the electron gun is better, causing misresistance, and as a result, the cathode ray tube color purity is further deteriorated.

The present invention has been made in order to solve the above-mentioned problems, and after drawing or forming a thin plate made of aluminum-kilted steel to produce an inner shield, annealing at a temperature higher than the recrystallization temperature to improve the non-uniform magnetic distribution and the surface The purpose of the present invention is to prevent a decrease in color purity by applying a blackened film to the magnetic properties to prevent magnetic resist caused by an external magnetic field, which has been a problem in the past.

1 is a cross-sectional view showing a conventional color cathode ray tube structure

Figure 2a is a state diagram showing the external magnetic flow flowing into the cathode ray tube

FIG. 2B is a detailed enlarged view of a portion “A” in FIG. 2A

Figure 3 is a state diagram showing the position of each part in the evaluation of the magnetic properties of the present invention

4 is a graph showing the amount of misresist according to the present invention.

* Description of the symbols for the main parts of the drawings *

6: magnetic shield

The present invention for achieving the above object is to produce an inner shield using a thin plate made of aluminum-kilted steel and then annealing in a high-temperature reducing atmosphere above the recrystallization temperature and coating the black cathode film, the inner shield of the color cathode ray tube It consists of a manufacturing method.

When described in more detail with respect to the present invention.

First, a soft magnetic sheet made of aluminum-kilted steel is drawn or formed into a desired inner shield, and then annealed.

At annealing treatment, the atmosphere is carried out under vacuum or in a hydrogen atmosphere using hydrogen gas or a mixture of hydrogen and nitrogen or a mixture of hydrogen and ammonia.

If oxygen enters during annealing, oxidation occurs at a high temperature, causing the soft magnetic surface to be oxidized, and the desired magnetic properties cannot be obtained.

Since the recrystallization temperature of aluminum-kilted steel is 500 degreeC, the annealing heat treatment is performed at the temperature higher than this, Preferably it is 700 degreeC or more and 1000 degrees C or less.

If the annealing treatment is performed below the recrystallization temperature, some rearrangement of the crystal may occur inside the inner shield, but crystal grain growth does not occur, and it is difficult to expect a change in magnetic properties due to diffusion of impurities contained in the shield. .

However, when the annealing is performed at a temperature above the recrystallization temperature, not only recrystallization easily occurs, but also after the recrystallization occurs, grains grow continuously, causing a change in magnetic properties.

The higher the annealing temperature, the faster the grain growth occurs, the higher the magnetic permeability, the smaller the coercive force, the higher the magnetic order characteristics of the inner shield. It has been found that the magnetic properties are improved.

In the present invention, the annealing heat treatment time is performed for 1 minute or more.

If it is within 1 minute, even a thin sheet cannot receive crystal heat and cause crystal growth after recrystallization occurs.

When annealing the inner shield in which deformation occurs after forming processing as a single body as in the present invention, the magnetic properties are improved as well as the magnetic properties to improve the shielding performance against the external magnetic field and thus affect the color purity of the cathode ray tube. Mistress of the tube is reduced.

The same principle applies to the X, Y, and Z axis directions of the cathode ray tube.

As described above, the annealing treatment restores the tissue deformation at the deformation site during the manufacture of the inner shield (drawing or forming) and grows the crystal grains so as to have desired magnetic properties.

The following is described according to the embodiment.

Pure iron, a soft magnetic aluminum-kilted steel, was purchased by continuous casting, hot rolling, cold rolling, and decarbonized annealing, and then drawn and heat treated under the conditions shown in Table 1 to evaluate magnetic properties at the sites shown in FIG. The results are shown in Table 2.

In the inner shield manufactured by drawing as in Comparative Example from Table 2, the magnetic properties are different from those of the long side portion (a) or the short side portion (c) due to mechanical deformation at the corner part (b) of the nose. As in the annealing heat treatment, not only the magnetic properties are uniform but also improved.

TABLE 1

TABLE 2

Figure 4 is a measure of the mis-resistance while varying the geomagnetic field in the trend after manufacturing the cathode ray tube.

In the case of the inner shield manufactured by drawing from FIG. 4, the amount of misresistance is large due to mechanical deformation at the corner of the nose part. However, when the annealing heat treatment is performed as in the present invention, the amount of misresistance is significantly reduced even if the magnetic field is varied. It can be seen that this is improved.

As described above, in the case of manufacturing an inner shield by drawing an integral form with a pure aluminum sheet of aluminum-kilted steel, the magnetic properties of the deformed portion by severe mechanical deformation in the corner portion of the inner shield where the long side and the short side of the inner shield meet. Not only is this greatly reduced, but the magnetic properties of the inner shield as a whole are not uniform, so that the deflection of the electron beam from the electron gun is better and the misresistance is increased. However, as in the present invention, the soft magnetic sheet is processed into an inner shield and then annealed. When the inner cathode shield is made and the color cathode ray tube is manufactured, the magnetic characteristics are not only uniform in the front of the inner shield, but the magnetic shielding characteristics are improved, and the magnetic shielding performance is improved, so that not only the center portion of the cathode ray tube but also the nose portion of the cathode ray tube The image quality is reduced because the misresist affects the color purity The effect is that the characteristics are improved.

Claims (5)

A method of manufacturing a magnetic shield for a color cathode ray tube, characterized in that by forming a thin plate made of aluminum-kilted steel to produce a magnetic shield, and then annealing at a recrystallization temperature or higher and blackening the film. The method of claim 1, A method for producing a magnetic shield for color cathode ray tubes, characterized by annealing in an oxygen-free atmosphere. The method of claim 2, A method for producing a magnetic shield for a color cathode ray tube, characterized in that the vacuum atmosphere or annealing using hydrogen gas or a mixed gas of hydrogen and nitrogen or a mixed gas of hydrogen and ammonia to create an oxygen-free atmosphere. The method according to any one of claims 1 to 3, A method for producing a magnetic shield for a color cathode ray tube, characterized in that the annealing time is 1 minute or more. The method of claim 1, A method of manufacturing a magnetic shield for a color cathode ray tube, characterized by producing a magnetic shield by drawing or forming a thin plate.

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