KR100252940B1 - Method for making inner-shield in a color brain-tube - Google Patents

Abstract

PURPOSE: A method for making a magnetic inner shield for a color cathode ray tube is provided to improve a shield performance against an outer magnetic field by growing a crystal grip. CONSTITUTION: A thin film is brewed and rolled by an aluminum solid steel. The thin film is treated an annealing over the temperature for recrystallizing. The temperature for recrystallizing in the aluminum solid steel is about 500°C. A thermal treatment is performed to the temperature of over 500°C. The annealing process uses of a hydrogen gas, a gas for mixing hydrogen with nitrogen, a gas for mixing hydrogen with ammonia. An inner shield is made by drawing and forming process which is mounted at the flame by means of a fixing fin. The inner shield is continually brewed the aluminum solid steel. The outer magnetic field is introduced into the cathode ray tube, and then flowed along to the inner shield.

Description

Method for manufacturing magnetic shield for color cathode ray tube {Method for making inner-shield in a color brain-tube}

The present invention relates to a magnetic shield of a color cathode ray tube (INNER SHIELD), and more particularly to a method of manufacturing a magnetic shield suitable for preventing the color purity of the cathode ray tube 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.

In order to prevent the electron beam from deflecting under the influence of geomagnetism, the electron beam passes through the slot of the shadow mask and reaches the fluorescent film. 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 direction of the tube axis 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 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. The notes are joined by a pin.

At this time, since the inner shield 6 formed at a predetermined interval against the panel is made of a magnetic material, the 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 reduced carbon content of pure iron with aluminum, and decarbonized to obtain a thin plate.

These thin plates are manufactured by the color cathode ray tube manufacturer to manufacture the inner shield by drawing or forming the thin plates.

However, since the aluminum-kilted steel is pure iron, a magnetic permeability of less than 3000 and a coercive force of 1.5 Oe or less is used to determine the strength of magnetic flux flow into the inner shield.

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

As such, due to the limitations of the magnetic properties of the inner shield, the cathode ray tube generates misresistance because the magnetic field affected by the external magnetic field flows into the three-dimensional space, causing the electron beam to be deflected from the electron gun, resulting in deterioration of the cathode ray tube color purity. There is a problem.

The present invention has been made to solve the above-described problems, the soft magnetic thin plate made of aluminum-kilted steel is annealed above the recrystallization temperature to grow crystal grains to improve the shielding performance against the external magnetic field to improve the color purity of the cathode ray tube It is an object of the present invention to provide an inner shield which is suitable for reducing mis-resistance of cathode ray tubes affecting the

1 is a state diagram 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 magnetic field distribution in the cathode ray tube

4 is a state diagram showing the amount of miss resist in a cathode ray tube;

Explanation of symbols for main parts of the drawings

6: magnetic shield

In order to achieve the above object, the present invention provides a thin plate formed by casting and rolling aluminum-kilted steel and decarbonization annealing, wherein the thin plate is subjected to annealing treatment after recrystallization temperature or higher, or recrystallized after bending the thin plate. Inner shield manufacturing method of the color cathode ray tube characterized in that the annealing (annealing) above the temperature.

Since the recrystallization temperature of the aluminum-kilted steel is 500 ° C., heat treatment is performed at a temperature of 500 ° C. or higher.

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

Therefore, when annealing at a temperature higher than the recrystallization temperature, not only recrystallization easily occurs, but also after the recrystallization occurs, the grains grow continuously, causing a change in magnetic properties.

As the annealing temperature increases, grains grow faster, the magnetic permeability is greatly improved, and the coercivity becomes smaller, and the magnetic shielding property of the inner shield is greatly improved. It has been found that the magnetic properties are improved.

And annealing is performed in the atmosphere without oxygen.

Hydrogen gas or a mixed gas of hydrogen and nitrogen or a mixed gas of hydrogen and ammonia is used for annealing in order to make the atmosphere free of oxygen.

As described above, as well as the stability of the magnetic properties as well as the magnetic properties are improved, the shielding ability to the external magnetic field is improved to reduce the mis-resist of the cathode ray tube affecting the color purity of the cathode ray tube.

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

The following is described according to the embodiment.

3 is a computer simulation of the magnetic field distribution in the 17-inch color cathode ray tube, a is a case of a cathode ray tube manufactured with the inner shield of the prior art, b is 900 of the gas atmosphere mixed with hydrogen and ammonia according to the present invention. This is the case of cathode ray tube fabricated inner shield after heat treatment at 10 ℃ for 10 minutes.

As can be seen, it can be seen that the magnetic field distribution in the cathode ray tube is much lower when heat-treated in a reducing atmosphere above the recrystallization temperature.

Figure 4 is a measure by measuring the amount of the mis-resist in the cathode ray tube manufactured by the above method, a is an inner shield of the prior art, b is a cathode ray tube with an inner shield according to the present invention.

As can be seen, when the heat treatment is performed in a reducing atmosphere, it can be seen that the misresist affecting the color purity is smaller at the corners as well as at the center of the cathode ray tube.

As described above, according to the present invention, the magnetic field distribution is lowered by applying the inner shield formed by heat treatment of the soft magnetic thin plate to the recrystallization temperature or higher to the cathode ray tube, and the misresist that affects the color purity is also small at the corners including the center portion of the cathode ray tube. As a result, the color cathode ray tube can be obtained.

Claims (3)

Fabrication of a thin plate made of aluminum-kilted steel by annealing at a recrystallization temperature of 500 ° C. or higher, or annealing at a recrystallization temperature of 500 ° C. or higher after bending the thin plate. Way. The method of claim 1, A method for producing a magnetic shield for color cathode ray tubes (INNER SHIELD), characterized in that the annealing treatment is carried out in an oxygen-free atmosphere. The method of claim 2, An annealing process for producing a color negative electrode tube (INNER SHIELD) characterized in that the annealing treatment using a hydrogen gas or a mixed gas of hydrogen and nitrogen or a mixed gas of hydrogen and ammonia.

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