JPS5846558A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a cathode-ray tube pressenting good resolution and characteristics of saturation and colorimetric purity, by fully reducing a beam diameter in the scanning direction of a beam. CONSTITUTION:The first electrode G1 of current control, forming a prefocus lens of an electron gun EG, is equipped with an aperture A of aspect ratio smaller than aspect ratio of a desired beam spot (section of a beam irradiated onto a fluorescent screen). The fourth electrode G4 is provided in a rear stage of the third electrode G3, and an electrostatic field lens L1 of bipotential system is formed by the third and fourth electrodes G3, G4, while a magnetic field lens M0, formed by a magnetic field generated from a circular annular permanent magnet, is provided in a rear stage of the lens L1. An electron beam is emitted from a triode part 2, if the beam is incident to the electrostatic field lens L1, a spread of the electron beam, emitted from the triode part 2, is suppressed by the electrostatic field lens L1, and an electron beam of small beam diameter is incident to the magnetic field lens M0, then the electron beam through the magnetic field lens M0 can be focused on the fluorescent screen.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a cathode ray tube suitable for a single-beam color television receiver, etc., and in particular, the beam diameter in the beam scanning direction is sufficiently narrowed down to achieve good resolution and saturation. The purpose is to obtain a cathode ray tube exhibiting characteristics of color purity and color purity.

In a Beam Intex color television system as an example in which the aSS tube of the present invention is suitably used, if the spot diameter of the electron beam on the fluorescent surface becomes wider than the width of each of the red, edge, and - stripes, Even at the timing when one phosphor stripe should be irradiated, adjacent phosphor stripes are irradiated at the same time, reducing the saturation of the color that should be emitted at that timing and reducing color purity. The color quality deteriorates significantly.

Therefore, it is required to significantly reduce the beam spot diameter and improve the luminous efficiency of the phosphor.

In order to obtain a particularly narrow electron beam, various cathode ray tube electron guns have been proposed.The conventional cathode ray tube electron gun, which uses two electrostatic field type lenses to obtain a narrow electron beam, is as shown in Figure 1. , a first electrode 11i (Gl) for current control is provided after the cathode ([), and a second electrode (G2) for an acceleration electrode is provided after the first electrode (G). 1. The second electrode (01C (G2)) constitutes a triode section (2) which is a cathode section.The electron beam emitted from this triode section (2) is transmitted to the second electrode (G2). The fourth electrode (G3) is installed after the third electrode (G3) and the fifth electrode (G3). It can be suppressed.

The electron beam whose spread is suppressed by the first electrostatic field type lens (L) is transmitted to the fourth electrode (G4) and the fifth electrode (G5) provided after the fourth electrode (G4).
5] Electrons incident on the second electrostatic field lens (L-ray) of the unipotential type consisting of the sixth electrode (G6) provided at the rear stage. At this time, electrons incident on the second electrostatic field-type lens (L-ray The beam hexagram of the beam is formed by the first electrostatic field type lens (L
Since the electron beam is made smaller due to the spherical aberration of the second electrostatic field lens (L), the spreading of the electron beam due to the spherical aberration of the second electrostatic field lens (L) is suppressed. The beam diameter is the first electrostatic field type lens (L
The electron beam diameter (beam diameter indicated by the dashed line) is smaller than that in the case of no rays, and a narrow electron beam is obtained.The beam spot diameter of the electron beam on the fluorescent screen is smaller than without.

In addition, both electrostatic field type lenses
or sixth electrode Ca3) I(Gsu, (G5J I(G6
), that is, the focusing voltage is obtained by dividing the high voltage for accelerating the electron beam, the focal length of both electrostatic field lenses (L and to be adjusted.

An electron beam focusing device using such an electrostatic lens (L-type lens) works relatively well by itself, but as the neck of the cathode ray tube becomes narrower due to lower power consumption, the electrostatic focusing electrode including the electron gun Since the inner diameter of the electrostatic lens and therefore the aperture of the electrostatic lens are restricted, it is difficult to increase the diameter of the electron beam spot.

Furthermore, in principle, there is a limit to the improvement of spherical aberration, and this has been the key to improving the color saturation characteristics and color purity characteristics of cathode ray tubes. The present invention aims to solve these various drawbacks of the conventional example, and solves these problems by defining the cross-sectional shape and shape of the beam and by using an electrostatic lens and a magnetic field lens in combination.

The details of the cathode ray tube of the present invention will be explained below with reference to FIGS. 2 and 5 showing different embodiments.

One embodiment shown in FIG. 2 is intended to be used in a beam index type television receiver, and the width in the scanning direction, that is, the short axis is narrower than the width of the fluorescent stripes on the fluorescent surface. The width in the direction perpendicular to the direction, that is, the major axis is selected to be approximately twice the minor axis, in order to reduce the current load on the cathode while maintaining the luminous efficiency of the phosphor.

The electron gun (PEA) used in this cathode ray tube consists of a cathode 113, a current control (first) electrode (01) forming a prefocus lens, and a beam extraction (second) electrode (G
2) and acceleration (fifth and fourth) electrodes (G6) (consisting of an electrostatic lens formed of G rim) and a magnetic field type lens (consisted of M rim).

The current control electrode (G1) controls the desired beam spot (
The aspect ratio (cross section of the beam irradiated onto the fluorescent surface) (Example 3:
1) with an aperture A having a smaller aspect ratio (Example 2:1). (The reason for this will be explained later.)Excluding this aperture configuration, the difference between Fig. 2 and Fig. 1 is that the third
A fourth electrode (G) is provided after the electrode (G5), and the third and fourth electrodes (G3).

(Due to the G, the pi-potential type electrostatic field type lens (
An electrostatic field type lens (a magnetic field type lens (Mo) formed by a magnetic field generated from an annular permanent magnet is provided after the L line), and a triode part (2
) When the electron beam emitted from the triode section (2) is incident on the electrostatic field lens (L), the spread of the electron beam '' emitted from the triode section (2) is suppressed by the electrostatic field lens (L), as described above. An electron beam with a small beam diameter is incident on the magnetic field lens (M).
The electron beam through Mo) is focused onto a fluorescent screen.

Taking a 6-type beam index tube electron gun as an example of such an electron gun configuration, the dimensions of the rectangular aperture tA+ of the first (G1) electrode are α2×0.4%, the second
(02) The circular aperture diameter of the electrode is 0.6-0.7%
Summer, 5th (03) The circular aperture diameter of the electrode is 2.0
% summer, the distance between the cathode IK) and the first (o) electrode is 11%, the first second ((11) (G2) the distance between both electrodes is 0.1%, the third, fourth (G3) , (G4) The distance between both electrodes is 4%.

With this configuration, when a DC voltage of 5 KV is applied to the G3 electrode (12 KV to the i4 electrode), both electrodes form a so-called pi-potential lens L1 as described above.

The embodiments of the above-mentioned magnetic field type lens (Mo) can be roughly divided into two types.
It can be divided into an external magnetic field method as shown in the figure and an external magnetic field method as shown in FIG.

The aforementioned external magnetic field type magnetic field lens (M) is a donut-shaped ferrite magnet l connected to an annular thin iron plate (2) (13
1, and is fixed and fixed to the neck part (Nl) of the cathode ray tube.

Although this external magnetic field type lens is advantageous in terms of cost, it is impossible to completely eliminate the misalignment between the center axis of each electrode of the electron gun and the center axis of the magnet, resulting in deformation of the cross-sectional shape of the beam. I can't deny the drawback of doing so. In the embodiment shown in FIG. 913, the same elements as in FIG. 1 are given the same reference numerals.

The external magnetic field type magnetic field lens disclosed as an embodiment in FIG. The lens is arranged in front of the 04 electrode so as to be concentric with the center axis of each electrode G1 to G4.

The spacer 183 is arranged outside the cathode ray tube and in front of the fourth electrode (G4). It is an annular body with low magnetic permeability. Specific materials include vinyl chloride, etc.
Li, a metal with low magnetic permeability such as aluminum, stainless steel, or glass is used.

When glass is used, the neck part may be molded in advance (uniformly and integrally), or it may be welded later.The thickness of this spacer (8), that is, the thickness of the annular body (D-d )teeth,
It is selected in consideration of the desired aperture of the magnetic field lens. This spacer (31 is an annular magnet (Mo) forming a magnetic field lens)
By being interposed between the magnetic field lens and the neck tube (N), the magnetic field lens functions as a large-diameter lens, converges the electron beam near its tip axis, and achieves low spherical aberration.

With this configuration, the electron beam lbJ generated in the electron emission region of the cathode (K) is transmitted through the current control electrode (near the aperture (AJ) of An elliptical electron beam with
! This results in a directional crossover. Due to the spherical aberration of the lens, the crossover in the Y direction is more cathodic (N
Occurs on the l side.

The electron beam passing through the 01.02 electrode is 05. After the diameter of the pi-potential lens (L) formed by the G4 electrode is narrowed down, the electron beam enters the subsequent magnetic field type lens (M). Cross-over in the direction is that the image is formed in front of the fluorescent screen of the cathode ray tube.As a result, the beam cross section becomes more vertically elongated on the fluorescent screen.Comparatively, the crossover in the X direction is It is located on the optical surface side, and its beam diameter defines the beam spot diameter in the beam scanning direction on the fluorescent surface screen, so the magnetic field lens is (The strength of the magnetic field and the mounting position of the magnet 11 (or 21) that constitutes the magnet must be adjusted.

Therefore, the aperture (^] of the current limiting electrode (G1)
The aspect ratio of the beam spot must be designed to be smaller than the aspect ratio of the beam spot diameter on the fluorescent screen.

As mentioned above, the advantages of adopting a configuration in which a vertically elongated beam is focused by a magnet ring lens made of a permanent magnet are: (a) Compared to an electrostatic lens, spherical aberration is small and a beam spot with a small diameter can be formed. .

- Even if the beam rotates along the magnetic field lines, when it is incident on the magnet ring and transmitted through it, it will eventually rotate in the opposite direction, so the overall rotation angle of J-mu will be zero. Become.

It is.

According to Takaaki Moto, the beam, which has a vertical cross section, passes through a vertically long aperture provided in the current control electrode, first passes through an electrostatic lens, and then passes through a large-diameter magnetic field lens. Since the beam is focused without being affected by spherical aberration while the change in beam focusing degree due to fluctuations in the high pressure for beam acceleration has been corrected, an extremely narrow electron beam can be obtained as shown in the equivalent optical system diagram in Figure 4. For example, when applied to a 6-inch beam index tube that does not use a shadow mask, a very good beam spot diameter can be obtained. Furthermore, if a bedding material is used, it is possible to form a beam spot with a small diameter and accurate width in the width direction of the electron beam along the scanning direction of the electron beam on the flourescent screen, making it suitable for beam index type televised forging machines. In addition to being able to provide a cathode ray tube with a good color surface image as a cathode ray tube, since an aperture is provided in tjIIlii (G1), it can also be driven with a small signal and can produce high color quality with good color saturation and color purity. It is possible to provide a cathode ray tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part of the prior art of the present invention. 2FIIJ and jI3 are both related to the present invention, and FIG. 2 is a cross-sectional view of the main part of an embodiment employing an external magnetic field lens,
FIG. 3 is a sectional view of a main part of another embodiment employing an external magnetic field lens, and FIG. 4 is a diagram showing an equal polarization optical system.

Claims (1)

[Claims] (A ring magnet is attached to the neck of a cathode ray tube equipped with an electron gun in which a prefocus lens and an electrostatic lens are sequentially arranged behind a 11-current 1 control electrode via a ring-shaped spacer with low magnetic permeability. A cathode ray tube comprising a large-diameter magnetic field lens. (2) A cathode ray tube according to claim 1, wherein the electrostatic lens is a pi-potential lens. (3) The annular magnet is permanently attached to the cathode ray tube. A cathode ray tube according to claim 1 or jI2, which is a magnet.