JPH04181637A - In-line type electron gun body structure - Google Patents

Abstract

PURPOSE:To prevent magnetic field loss due to eddy current generated by a deflection magnetic field with the function of an original magnetic field control element retaining by dividing annular magnetic shielding elements into plural and concentric stage states. CONSTITUTION:Two concentric stage-like parts 24a and 24b are formed in annular magnetic shielding elements 24 composed of a high-permeability magnetic body, and the surface of the element 24 is divided into three stages. In this case, the whole surface area of the element 24 is made same as that of a single element having no different level. The surface of the element 24 is divided into three stages, consequently an eddy current circuit, generated on the surface by a horizontal deflection magnetic field, becomes a condition in which the eddy current circuit is cut compared with the case of a single plane. Therefore an area, interlinking a horizontal deflection magnetic field which is a cause for producing an eddy current, is reduced, and magnetic field loss, due to the eddy current produced by the deflection magnetic field, can be prevented with the original function of a magnetic field control element retaining.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron gun assembly that can improve the convergence characteristics of a color cathode ray tube.

[Conventional technology]

FIG. 5 is a longitudinal sectional view of a color cathode ray tube using a self-convergence type in-line electron gun which is generally widely used. Two outer and central electron beams Bs emitted from the in-line electron gun 1 in the same plane
, Bc, and Bs are deflected horizontally and vertically by a deflection yoke 5 disposed in the funnel-shaped part of the glass envelope 2 maintained in a high vacuum. A scanning screen 6 is formed on a phosphor screen 4 on which a plurality of phosphor pixels that emit light in different colors are deposited, through a shadow mask 3 placed opposite to the phosphor screen 4. In order to realize self-convergence, the horizontal and vertical deflection magnetic field distributions of the deflection yoke 5 are shaped into a pincushion shape and a barrel shape, respectively. Further, on the bottom surface 13 of the bottomed cylindrical shielding magnetic pole 10 having the side portion 12 attached to the electron beam exit tip of the electron gun 1, a hole is formed around the outer electron beam aperture 11S as shown in FIG. An annular magnetic shielding element 14 made of a high magnetic permeability magnetic material is arranged with a magnetic enhancement element 15 arranged at a symmetrical position with respect to the central electron beam aperture 11C on a perpendicular bisector connecting the centers of both side apertures 11S. Book electron beam Bs
, Bc, and Bs are superimposed over the entire area on the phosphor screen 4 to obtain a scanning screen 6. Below, the annular magnetic shielding element 1
4. The magnetic enhancement elements 15 are collectively referred to as magnetic field control elements.

The static correction device 7 is a 4-pole, 6&
This correction device is composed of a bipolar magnetized annular body and is mounted outside the neck of the cathode ray tube.

Generally, when there is no magnetic field control collector, the scanning screen 6 on the phosphor screen 4 has a horizontal deflection magnetic field or a pincushion type, and the vertical deflection magnetic field has a barrel-shaped distortion magnetic field distribution, so the scanning screen of the electron beam B5 outside the wound will match. Alternatively, the central electron beam Bc passes through a weaker magnetic field than the external electron beam B5, and its deflection sensitivity is lower than that of the external electron beam BS, and the scanning screen formed by the central electron beam BC is horizontally and vertically co-lateral. A concentration error occurs due to so-called coma aberration, which is smaller than that of the electron beam.

In order to correct this concentration error, the annular magnetic shielding element 14 bypasses and weakens the horizontal and vertical magnetic fields 5H and 5V on the path of both outer electron beams Bs, as shown in FIG. A vertical magnetic field 5■ is concentrated and strengthened on the passage.
On the other hand, the magnetic enhancement element 15 is the central electron beam B. A horizontal deflection magnetic field of 5 V is concentrated on the path of the magnetic field to perform an intensifying effect. As a result, the three electron beams are superimposed over the entire area on the phosphor screen 1, making it possible to obtain a scanning screen 6 without concentration errors.

[Problem to be solved by the invention]

In addition to TV applications, color cathode ray tubes are used as display tubes for various information display devices with high resolution characteristics.In particular, recently, in order to improve the display quality and achieve high density display, the horizontal deflection frequency has been changed for TV use. 15.75
High-speed scanning is now performed by increasing the frequency from KHz to 64KH2 or higher. in this case,
As shown in FIG. 8, misconvergence HCR, HC-L, which is an asymmetric concentration shift of the scanning screen 6 at the left and right ends of the fluorescent screen 4, of the central electron beam Bc and the external electron beam Bs, which can be ignored at TV frequencies, is caused. It's becoming noticeable.

The reason for this is thought to be as follows. That is, the electron beam is horizontally deflected from the left end of the phosphor screen to the right end when viewed from the phosphor screen 4 side, and the direction of the horizontal deflection magnetic field 5H is from bottom to top within the bottom surface of the shielding magnetic pole in FIG. 6 when viewed from the phosphor screen side. Head over. Eddy currents are generated in the annular magnetic shielding element 14 by the high-speed horizontal deflection magnetic field, and as a result, residual magnetic fields whose phase lags behind the main horizontal deflection magnetic field 5H are generated in both outer electron beam holes 11s. Therefore, the electron beam Bs outside the wound is the center electron beam Bs.
It is slightly deflected further to the right than c. In particular, the slow phase magnetic field due to the eddy current generated by the time differential value of the horizontal deflection magnetic field is larger at the end of the deflection than at the beginning of the deflection, and furthermore, when deflecting the middle point, that is, the center of the phosphor screen, as shown in Figure 7. As shown in FIG. 2, the scanning screen of the electron beam outside the wound has an asymmetric concentration shift that is generally shifted to the right from the center electron beam, and the shift HC is maximum at the center of the screen. Since this deviation HC at the center of the screen can be corrected by the silence correction device 7, the phosphor screen 4
As shown in Fig. 8, the above scanning screen has an asymmetrical concentration deviation amount HCL, )ICR of the central electron beam Bc with respect to the external electron beam B5 at the left and right ends of the phosphor screen 4, and asymmetric coma aberration. This causes misconvergence. According to experiments, for example, in a 20-inch display tube, when the horizontal deflection frequency is 64 KHz, HCL and HCR are as high as 0.3 to 0.7 mm, and the misconvergence can no longer be ignored, significantly deteriorating the display quality. I will let you do it. Note that the magnetic enhancement element 15 generally has a smaller surface area than the annular magnetic shielding element 14, and the influence of eddy current loss on magnetic field changes can be ignored.

The present invention has been made in view of the above-mentioned drawbacks, and is designed to prevent asymmetric misconvergence at the left and right ends of the screen, regardless of the horizontal deflection frequency, in a color cathode ray tube using a self-convergence type in-line electron gun. The purpose of the present invention is to provide an in-line type electron gun elliptical body.

[Means to solve the problem]

The present invention relates to an in-line electron gun ellipse having a bottomed cylindrical shielding magnetic pole made of a non-magnetic material at the tip of the electron beam exit side, and annular magnetic shielding elements attached around both outer electron beam passage openings. , the annular magnetic shielding element is divided into a plurality of steps, or is divided into a plurality of concentric steps with a plurality of radial slits formed in one of the steps, or has a plurality of annular thin plates. Are they formed by overlapping each other?
It is characterized by being formed by stacking a plurality of concentric thin plates.

With this configuration, it is possible to prevent magnetic flux loss due to eddy currents induced by the deflection magnetic field while maintaining the original function of the magnetic field control element with respect to the deflection magnetic field, and even when the horizontal deflection frequency is increased. First, it is possible to eliminate asymmetrical misconvergence due to comatic aberration of the scanning screen formed by the central and both outer electron beams, and the in-line electron gun can be made into an electron gun structure capable of displaying high-density video information.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

1(a) and 1(b) respectively show a bottom view (viewed from the phosphor screen) of a shielding magnetic pole 10 and a perspective view of an annular magnetic shielding element 24 according to a first embodiment of the present invention. In the following, for the purpose of simplifying the explanation, the same components as those in the prior art are given the same reference numerals as above.

The annular magnetic shielding element 24 made of a high magnetic permeability magnetic material has two concentric stepped portions 24a and 24b, and its surface is divided into three steps. In this case, the total surface area of the annular magnetic shielding element 24 is set to be the same as the surface area of a single annular magnetic shielding element 14 used conventionally.

Since the surface of the annular magnetic shielding element 24 is divided into three stages, the eddy current circuit generated on this surface by the horizontal deflection magnetic field 5H is more disconnected than in the case of a single plane. Therefore, the area interlinked with the horizontal deflection magnetic field that causes the generation of eddy current is reduced, the generation of eddy current can be prevented, and the magnetic field control function for the horizontal deflection magnetic field 5H is maintained.

Therefore, by making the annular magnetic shielding element 24 concentrically stepped, the occurrence of asymmetric concentration errors as shown in FIG. , HCR becomes smaller,
The concentration error can be practically ignored.

According to experiments, in a 20-inch color display tube, the amount of asymmetric coma aberration H for a horizontal deflection frequency of 64 KHz
The amount of coma aberration can be reduced from about 03 to 0671 in the conventional untreated tube to about 0.1 to 02 by the embodiment of the present invention, which is practically negligible.

FIG. 2 is a perspective view of an annular magnetic shielding element 34 showing a second embodiment of the present invention. The difference from FIG. It is divided into two stages, and the uppermost stage has a plurality of slits 34S in the radial direction. As a result, even if the step portion is small, the eddy current generation surface is divided by the slit, making it difficult for eddy current to be generated in response to a high-speed horizontal deflection magnetic field.

It goes without saying that the number of stages of the concentrically stepped annular magnetic shielding element is not limited to the above example, and may be two or more.

3(a) and 3(b) respectively show a bottom view (viewed from the phosphor screen) of the shielding magnetic pole 10 and a perspective view of the annular magnetic shielding element 44 according to the third embodiment of the present invention. For simplification, the same components as in the past are given the same reference numerals as above.The annular magnetic shielding element 44 made of a high magnetic permeability magnetic material includes an annular thin plate 44a of the same diameter made of a high magnetic permeability magnetic material,
44b, 44. It is formed by overlapping C. In this case, the total surface area of the annular magnetic shielding element 44 is set to be the same as the surface area of a single annular magnetic shielding element 14 used conventionally.

Generally, the smaller the thickness of the metal plate, the less likely eddy current loss caused by a high-frequency magnetic field will occur. Therefore, since the annular magnetic shielding element 44 is made up of three thin plates with a thickness of 0.05 to 0.1 mm, the eddy current generated on the surface of this element by the horizontal deflection magnetic field 5H is smaller than that of a single plate. This can be prevented from occurring, and the magnetic field control function for the horizontal deflection magnetic field 5H is maintained.

According to experiments, a 20-inch color display tube has an asymmetric coma aberration amount for a horizontal deflection frequency of 64 KHz)
The ICL and HCR can be reduced from about 03 to 071 with conventional untreated pipes to about 01 to 0.2 mm with this embodiment.
It was possible to make the amount of coma aberration negligible in practical terms.

FIG. 4 is a perspective view of an annular magnetic shielding element 54 showing a fourth embodiment of the present invention. The difference from FIG. 3 is that the annular magnetic shielding element 54 has a concentric thin plate 54a.

54b and 54c are stacked and bonded to form a stepped surface. Since the surface is thus divided into steps, eddy currents are less likely to be generated in response to a high-speed horizontal deflection magnetic field than in the third embodiment. It goes without saying that the number of thin plates in the concentric annular magnetic shielding element is not limited to the above example, but may be two or more. Furthermore, it goes without saying that the present invention is applicable not only to annular magnetic shielding elements but also to magnetic field control elements having other shapes.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to maintain the original function of the magnetic field control element with respect to the deflection magnetic field, to prevent magnetic field loss due to vortices with a simple configuration, and to increase the horizontal deflection frequency. Regardless, it is possible to obtain an in-line electron gun ellipse in which left-right asymmetrical misconvergence due to coma aberration of the scanning screen formed by the central and both outer electron beams is eliminated.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a bottom view of a shielding magnetic pole and a perspective view of an annular magnetic shielding element according to a second embodiment of the present invention, and FIG. 2 is an annular magnetic shielding according to a second embodiment of the present invention. A perspective view of the element; FIGS. 3A and 3B are a bottom view of a shielding magnetic pole and a perspective view of an annular magnetic shielding element according to a third embodiment of the present invention; FIG. 4 is a perspective view of a fourth embodiment of the present invention. Perspective view of example annular magnetic shielding element, No. 5
The figure is a vertical cross-sectional view of a color cathode ray tube using a conventional in-line electron gun, Figure 6 is a bottom view of the shielding magnetic pole seen from the phosphor screen, and Figure 7 is the phosphor screen when static concentration correction is not performed. The above figure shows the scanning screen, and FIG. 8 shows the scanning screen on the phosphor screen after static concentration correction. 1... In-line electron gun, 2... Glass envelope, 3
・Shadow mask, 4. Fluorescent screen, 5. Deflection yoke,
6... Scanning screen, 7... Silence correction device, 1o... Shielding magnetic pole, IIC, 11S... Center and outer electron beam aperture, 13... Bottom surface of shielding magnetic pole, 14. ．． 24.44°54... Annular magnetic shielding element, 15... Magnetic enhancement element,
24a, 24b, 34a - Stepped part, 34 S-slit, 44a, 44b, 44cm - Annular thin plate, 54a, 5
4b, 54c... Concentric thin plates.

Claims (1)

[Claims] 1. An in-line electron gun having a bottomed cylindrical shielding magnetic pole made of a non-magnetic material at the tip of the electron beam exit side, and annular magnetic shielding elements attached around both outer electron beam apertures. An in-line electron gun structure, wherein the annular magnetic shielding element is divided into a plurality of steps. 2. In an in-line electron gun structure having a bottomed cylindrical shielding magnetic pole made of a non-magnetic material at the tip of the electron beam exit side, and annular magnetic shielding elements attached around both outer electron beam apertures, the annular magnetic An in-line electron gun assembly characterized in that the shielding element is divided into a plurality of concentric steps, and at least one of the steps has a plurality of slits formed in the radial direction. 3. In an in-line electron gun structure having a bottomed cylindrical shielding magnetic pole made of a non-magnetic material at the tip on the electron beam exit side, and annular magnetic shielding elements attached around both outer electron beam apertures, the annular magnetic This is an in-line electron gun structure in which the shielding element is formed by stacking a plurality of annular thin plates. 4. In an in-line electron gun structure having a bottomed cylindrical shielding magnetic pole made of a non-magnetic material at the tip of the electron beam exit side, and annular magnetic shielding elements attached around both outer electron beam apertures, the annular magnetic An in-line electron gun structure characterized in that the shielding element is constructed by stacking a plurality of concentric thin plates.