JPH04315738A - Cathode-ray tube and method of demagnetizing it - Google Patents

Abstract

PURPOSE:To make a cathode-ray tube less affected by geomagnetism so as to uniform demagnetization of the tube by forming from a ferromagnetic material of high magnetic permeability and low coercive forces a magnetic metallic material constituting one part of a vacuum envelope, and also using a ring- shaped demagnetizing coil. CONSTITUTION:A front metallic envelope 1 and a back metallic envelope 2 are both made of a permalloy and a metal funnel is also made of the permalloy. To demagnetize a flat cathode-ray tube, a ring-shaped demagnetizing coil is used. Because a ferromagnetic material of high magnetic permeability and low coersive forces such as a permalloy is thus used as the metallic material from which the envelopes 1,2 of a vacuum envelope 4 are made, magnetization due to geomagnetism is reduced to such an extent as being negligible and mislanding due to magnetization does not occur. Also the magnetic metallic material constituting the envelope 4 and being magnetized can uniformly be demagnetized by using the ring-shaped demagnetizing coil.

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 in which a portion of the vacuum envelope is formed of a magnetic metal material, and a degaussing method.

0002

2. Description of the Related Art FIG. 1 is a longitudinal cross-sectional view showing the structure of a flat cathode ray tube in which a part of the vacuum envelope is made of iron-based metal material. Back metal envelope, 3
1 is a screen glass, 11 is a glass window, and 1 to 3 and 11 constitute a vacuum envelope 4. 5 is a cathode section, 6 is an electron beam extraction section, 7 is an electron beam control electrode, 8 is a support member, and 9 is a phosphor layer, which are formed on the inner surface of the screen glass 3. Reference numeral 10 denotes a getter container, which is provided for heating the getter container 10 by irradiating the getter container 10 with a laser beam from the outside.

FIG. 2 is a longitudinal cross-sectional view of a shadow mask type cathode ray tube, in which 12 is a metal funnel made of iron-based metal material, 13 is a neck glass, and 3, 11 to 13 are vacuum envelopes 4. 14 is an electron gun, and 15 is a shadow mask (color selection electrode).

0004

[Problem to be Solved by the Invention] If a part of the vacuum envelope 4 is made of iron-based magnetic metal material, it will be magnetized by the earth's magnetism, and the trajectory of the electron beam will be bent by the magnetic flux, so that colors will appear on the screen. A deviation (hereinafter referred to as "mislanding") occurs. Furthermore, a stick-shaped demagnetizer has conventionally been used to demagnetize a magnetized vacuum envelope, but it has been difficult to perform uniform demagnetization.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a cathode ray tube that is less affected by earth's magnetic field. Moreover, the invention of claim 2 aims to obtain a demagnetization method that can perform uniform demagnetization.

[0006]

[Means for Solving the Problem] According to the invention of claim 1, the magnetic metal material constituting a part of the vacuum envelope is made of a ferromagnetic material having high magnetic permeability and small coercive force, such as permalloy. It is characterized by the following points. Further, the invention according to claim 2 is characterized in that the cathode ray tube is demagnetized using a ring-shaped degaussing coil.

[0007]

[Embodiment] An embodiment of the invention according to claim 1 will be described. In this embodiment, the front metal envelope 1 and the rear metal envelope 2 shown in FIG. 1 are made of permalloy. Also,
The metal funnel 12 in FIG. 2 is made of permalloy. In this way, if the metallic part of the vacuum envelope 4 is made of a ferromagnetic material with high magnetic permeability and low coercive force, such as permalloy, the magnetization caused by the earth's magnetic field becomes almost negligible. Since mislanding is also reduced, there is no need to demagnetize the vacuum envelope 4.

Next, an embodiment of the invention according to claim 2 will be described. FIG. 3 is a diagram showing the degaussing coil used in this example, and 16 is a ring-shaped degaussing coil (hereinafter referred to as "degaussing coil").
17 is a power supply device that supplies a demagnetizing current to the demagnetizing coil 16.

FIG. 4 is a diagram showing the movement locus of the degaussing coil 16 when the flat cathode ray tube is demagnetized using this degaussing coil 16. The degaussing coil 16 is moved in the direction of the arrow so that the vacuum envelope 4 passes through it.

FIG. 5 is a diagram showing another movement locus of the degaussing coil 16. In this embodiment, the outer circumference of the vacuum envelope 4 is
The degaussing coil 16 is rotated once in the direction of the arrow while keeping its orientation constant.

When degaussing is performed with the degaussing coil 16 along a trajectory as shown in FIG. 4 or 5, the front and back metal envelopes 1
, 2 can be uniformly demagnetized.

The metal funnel 12 of the shadow type cathode ray tube shown in FIG. 2 can also be degaussed by moving the degaussing coil 16 along the locus shown in FIGS. can be uniformly demagnetized.

[0013]

According to the invention as claimed in claim 1, since the metal material constituting the vacuum envelope is made of a ferromagnetic material such as permalloy with high magnetic permeability and low coercive force, magnetization by earth's magnetism is prevented. The size is almost negligible, and mislanding due to magnetization does not occur. Further, according to the invention of claim 2, since the ring-shaped demagnetizing coil is used to demagnetize the magnetic metal material constituting the vacuum envelope, the magnetization can be uniformly demagnetized. Can be done.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a flat cathode ray tube having a vacuum envelope partially made of a magnetic metal material.

FIG. 2 is a longitudinal sectional view of a shadow mask type cathode ray tube having a metal funnel.

FIG. 3 is a diagram showing a degaussing device equipped with a ring-shaped degaussing coil used in the present invention.

FIG. 4 is a diagram showing a movement locus of a degaussing method using a ring-shaped degaussing coil.

FIG. 5 is a diagram showing another movement locus of a degaussing method using a ring-shaped degaussing coil.

[Explanation of symbols]

1 Front metal envelope 2　Back metal envelope 3 Screen glass 4 Vacuum envelope 12 Metal Funnel 16 Ring-shaped degaussing coil

Claims (2)

[Claims] 1. A cathode ray tube in which a part of the vacuum envelope is made of a magnetic metal material, characterized in that the magnetic metal material is a ferromagnetic material having high magnetic permeability and small coercive force. Cathode ray tube. 2. A cathode ray tube in which a part of the vacuum envelope is formed of a magnetic metal material is demagnetized by the earth's magnetism using a ring-shaped degaussing coil. How to demagnetize a cathode ray tube.