JP2003092071A - Electron gun for color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron gun which maximizes action of a VM coil acting by synchronizing with derivative signals of image signals. SOLUTION: With the electron gun including a cathode 3 emitting electron beams toward a phosphor screen, an anode 9 of the screen side, and focus electrodes 8 of the cathode side, and a cathode-ray tube including a VM coil 18 mounted on a neck of the cathode-ray tube and acting in synchronization with image signals of a circuit, the focus electrodes 8 on which fixed focus voltage is impressed are composed of a set of not less than two electrodes continuously arrayed. Provided the length of the focus electrodes is 'L,' and total of distances of each two electrodes is 'g,' (g×100)/L=5 to 30(%) is satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun used for a color cathode ray tube, and more particularly to a color cathode ray tube having an improved electrode structure and shape in order to reduce a spot diameter which affects the focus of an electron beam. Related to electron guns for tubes.

[0002]

2. Description of the Related Art FIG. 1 is a schematic diagram of a conventional cathode ray tube. Referring to FIG. 1, a large number of electrodes are formed on an in-line type electron gun for a cathode ray tube. The electrode 1 controls the electron beam generated at the cathode 3 with a constant intensity and
In order to reach 7, the electron beams 13 are positioned at regular intervals so as to be perpendicular to the passage path of the electron beam 13.

More specifically, three cathodes 3 which are independent of each other, a first electrode 4 which is a common grid of the three cathodes 3 which are arranged at a certain distance from the cathodes, and a certain distance from the first electrode The second electrode 5, the third electrode 6, the fourth electrode 7, the fifth electrode 8 and the sixth electrode 9 arranged in this order are configured in this order.

A shield cup 10 having a BSC 11 attached to the sixth electrode 9 serves to fix the electron gun on the neck of the tube while electrically connecting the electron gun to the tube. The in-line type electron gun comprised in order of.

The operation of the electron gun will be described. In the electron gun, electrons are emitted from the stem pin 1 of the heater 2 built in the cathode 3, and the electron beam 13 is controlled by the first electrode 4 of the control electrode. , The electron beam 13 is accelerated by the second electrode 5 of the acceleration electrode, and the second electrode 5, the third electrode 6,
The electron beam is partially focused and accelerated by the focusing lens at the tip formed between the fourth electrode 7 and the fifth electrode 8.

Also, in order to form a quadrupole lens for compensating the astigmatism generated by the deflection yoke, a part of the electrode forming the main lens is called a focus electrode and is synchronized with the deflection signal. By the sixth electrode 9 to which a variable voltage is applied and the seventh electrode 10 called an anode electrode,
The electron beam mainly focuses and accelerates, passes through the shadow mask 15 formed inside the fluorescent screen 16, collides with the fluorescent screen 16, and emits light.

A deflection yoke 12 for deflecting the electron beam 13 emitted from the electron gun to the entire surface of the screen 17 is positioned outside the electron gun to embody a screen.

The conventional cathode ray tube equipped with an electron gun has a neck (VM) (Vel) which operates in synchronization with the video signal of the circuit.
18 is attached. The coil is applied for reducing the spot diameter, which is the main aspect of the present invention.

Conventionally, lens magnification, space charge repulsion and spherical aberration characteristics of the main lens are factors that influence the spot diameter on the screen in the design characteristics of the electron gun.

The operation of the above characteristics and the like will be described in more detail. The influence of the lens magnification on the spot diameter (D _x ) is such that the basic voltage condition, the focal length, the length of the electron gun, etc. have been determined, so there are few parts that can be utilized as design elements in the electron gun. The effect is also small.

The influence of the space charge repulsive force is a phenomenon of expanding the spot diameter due to mutual repulsion and collision between electrons in the electron beam, and the spot diameter (D
_In order to reduce the expansion of _st ), it is advantageous to design so that the traveling angle of the electron beam (hereinafter, referred to as divergence angle; α) becomes large.

The influence of the spherical aberration characteristic of the main lens is the expansion development of the spot diameter (D _ic ) due to the difference in focal length between the electrons passing through the paraxial axis and the electrons passing through the far axis of the lens. Contrary to the charge repulsion, the smaller the divergence angle of the electron beam incident on the main lens, the smaller the spot diameter can be realized on the screen.

As explained above, the spot diameter on the screen
(D _t ) is generally expressed by the sum of three types of elements as in the following equation.

In particular, it is best to enlarge the diameter of the main lens as a method for reducing the spherical aberration while reducing the space charge repulsion force.

By enlarging the diameter of the main lens, even if an electron beam with a large divergence angle is incident, the expansion of the spot due to spherical aberration can be reduced, and the space charge repulsive force after passing through the main lens portion can also be reduced. It is possible to realize a small spot in.

FIG. 2 shows the experimental results showing the above contents.
The change in spot diameter depending on the main lens diameter is shown.

As can be seen from the graph shown in FIG. 2, the larger the main lens diameter is, the smaller the enlargement of the spot diameter due to the spherical aberration of the main lens is, so that the spot diameter on the screen can be reduced.

And, in general, a fifth voltage to which a high voltage is applied.
The electrode and the sixth electrode to which a variable voltage is applied in synchronization with the deflection signal are collectively called the focus electrode, and the length of the focus electrode is an important factor that determines the voltage ratio (%: focus / high voltage) of the electron gun. Is. Inclusion of the sixth electrode may compensate astigmatism of the deflection yoke, but the sixth electrode is used when there is little need to improve relatively high resolution and sharpness of the peripheral portion of the screen. Sometimes I don't.

As a method of enlarging the main lens portion, a method of mechanically enlarging the hole diameter of the main lens forming electrode and a method of increasing the depth of the electrostatic field control electrode body for performing the lens correcting action have been presented.

[0020]

However, it is necessary to mechanically expand the hole diameter of the electrode by φ29.1 mm.
Since it is almost impossible because of the limiting factor of the neck diameter, there is a difficulty in improving the focus quality.

Therefore, in order to reduce the spot diameter on the screen and improve the resolution, the chassis (Chassis)
Operate the circuit driving the cathode ray tube installed in
A differential signal of a video signal for scanning an electron beam on a screen is applied in synchronization with a coil installed at the neck of a cathode ray tube with an electron gun. As a result, the electron beam is modulated at a speed at which it is uniformly deflected by the deflection magnetic field of the deflection yoke, so that the resolution and sharpness on the screen can be improved.

FIG. 3 schematically shows the operating principle of the VM coil. In order to maximize such a circuit-like resolution improving method, the total length of the electrodes to which the conventional fixed focus voltage is applied is sufficiently short, and the velocity modulation magnetic field due to the current applied in synchronization with the video signal of the coil is generated. There is a problem that a sufficient space must be formed to effectively invade.

The structure of the conventional electron gun is not suitable for maximizing the effect of the coil as described above.

Normally, the center of the magnetic field generated by the coil is located in the vicinity of the fixed fifth electrode to which a relatively high voltage is applied, but the length of the electrode is adjusted to match the voltage ratio required for design. Is generally long.

Increasing the length of the electrode has the advantages of cost reduction and simplification of the production process as compared with the case where small parts are continuously installed.

However, the structure of the electron gun having such a simplified long electrode acts as an element that weakens the speed modulation effect by the magnetic field of the coil and hinders the improvement of resolution.

An object of the present invention is to solve the problems of the prior art, in which a focus electrode to which a fixed focus voltage is applied is composed of two or more electrodes arranged in series, and the fixed focus voltage is applied. An object of the present invention is to provide an electron gun that maximizes the action of a VM coil that operates in synchronization with a differential signal of a video signal by maintaining an appropriate distance between focus electrodes.

[0028]

An electron gun for a color cathode ray tube according to the present invention includes an electron gun that emits an electron beam toward a phosphor screen, an anode electrode on the screen side, and a focus electrode on the cathode side. , And a fixed focus voltage is applied in a cathode ray tube including a VM coil mounted on the neck portion of the cathode ray tube with the position of the focus electrode being the center of the magnetic field and acting in synchronization with the video signal of the circuit. If the focus electrode is composed of a set of two or more electrodes arranged continuously, and the total length of the focus electrodes is'L 'and the total distance between the electrodes is'g', then (g × 100) / L = 5-30 (%)
Is satisfied.

According to the present invention, the size of the screen spot diameter in the horizontal direction can be reduced by 15 to 30% to improve the screen resolution.

[0030]

DETAILED DESCRIPTION OF THE INVENTION An electron gun for a color cathode ray tube according to the present invention will be described in detail below with reference to the accompanying drawings. First, in order to maximize the circuit resolution improvement method of the VM coil, the length of the focus electrode, to which a fixed focus voltage at which the center of the magnetic field generated by the VM coil is located, is applied, is increased to match a high voltage ratio. There is a need to.
In addition, a sufficient gap between the electrodes should be formed so that the velocity modulation magnetic field due to the current applied in synchronization with the video signal of the VM coil effectively penetrates.

Therefore, the electron gun main lens structure of the present invention is similar to the conventional electron gun structure as shown in FIG. 1 and has electrodes having openings common to three electron beams and three electron beams. It is composed by stacking a plate-shaped electrostatic field control electrode body having a through hole and a gap-shaped electrode, and since the electrodes are electrically connected through a welding process etc., they are synchronized with the high voltage and the deflection signal. Variable voltage is applied.

Of the main electrodes conventionally composed of the anode electrode on the screen side and the focus electrode on the cathode side, the focus electrode is classified into an electrode for applying a variable focus voltage and an electrode for applying a fixed focus electrode. It

Among them, the fixed focus electrodes for applying the fixed focus voltage are divided into two or more and arranged.

FIGS. 4A and 4B are structural views of a conventional electron gun, and FIG. 4C is a structural view of the electron gun according to the present invention, in which a focus electrode to which a fixed focus voltage is applied. 28 is an electron gun structure in which they are continuously arranged.

FIG. 4D is a structural view of the electron gun according to the present invention, in which a focus electrode 31 to which a variable focus voltage is applied and a focus electrode 28 to which a fixed focus voltage is applied are continuously arranged. The structure of the electron gun is shown.

FIG. 4C shows a cathode 23 to which a video signal is applied, a second electrode 25 which attracts electrons emitted from the cathode so as to gather and progress in the screen direction, and an electron beam is applied to the cathode. A first electrode 24 that stops the emission of electrons when a voltage corresponding to a video signal of a certain level or more is not applied is disposed, and a third electrode 26 that applies a relatively high voltage and a relatively low voltage are applied. A fourth electrode 27 for applying and a focus electrode 28a for applying a relatively high fixed voltage,
28b and 28c.

Then, the ninth electrode 29 to which a high voltage is applied forms a main lens so as to scan an electron beam on the screen to form a screen of the cathode ray tube.

FIG. 4D shows a structure similar to that of FIG. 4C, in which a focus voltage which is varied in synchronization with the deflection signal of the deflection yoke is applied and the astigmatic difference generated by the deflection yoke magnetic field is applied. The eighth electrode 31 forming a quadrupole lens is further arranged so as to compensate for

The eighth electrode 31 and the ninth electrode to which a high voltage is applied
With the electrode 29, a main lens is formed on the screen so as to scan the electron beam, and the screen of the cathode ray tube is formed.

FIG. 6 shows the structure of an electron gun having a focus electrode for applying a fixed focus voltage according to the present invention.

The main electrode is composed of an anode electrode 29 and a focus electrode 28.
Is composed of an electrode 31 for applying a variable focus voltage and an electrode 28 for applying a fixed focus voltage.

Among them, two or more focus electrodes 28 for applying a fixed focus voltage are continuously arranged together with the focus electrodes 28a, 28b and 28c of FIGS. 4c and 4d, and the total length L of the focus electrodes 28 continuously arranged is L. It has a value of 4 mm or more and 30 mm or less.

At this time, if the total of the intervals g1 and g2 between the continuously arranged focus electrodes 28 is g, then
Make sure that (g × 100) / L = 5 to 30 (%) is satisfied.

Experimental results for the focus electrode 28 to which a fixed focus voltage satisfying the above expression is applied are shown in the graph of FIG.

FIG. 5 shows a change in the spot diameter of the screen by the focus electrode to which a fixed focus voltage is applied and the coil which operates in synchronization with the differential signal of the video signal.

FIG. 5A shows the number of intervals between the electron gun electrodes, in particular, the focus electrodes positioned at the center of the working magnetic field of the coil and to which the fixed focus voltage is applied, that is, the fifth electrode 28a and the sixth electrode in FIG. 28b is a graph showing numbers for forming an interval such as 28b and the seventh electrode 28c and the reduction amount of the screen spot due to the velocity modulation magnetic field of the coil, and it can be seen that the effect increases as the number of intervals increases.

FIG. 5B shows the length of the space between the focus electrodes 28 and the reduction amount of the screen spot due to the velocity modulation magnetic field of the coil. When the space is about 0.6 to 1.2 mm. It can be seen that the effect of the coil is maximized.

Further, FIG. 5C is a graph showing the relationship between the total length of the electron gun and the velocity modulation magnetic field of the coil, and it can be seen that there is a section proportional to the electron gun inserted in the cathode ray tube.

Therefore, when analyzing the data of FIG. 5 as described above, the number of intervals between the focus electrodes 28 is 1
The number of focus electrodes 28 should be at least 0.6, and the width of the space between the focus electrodes 28 is most effective at a level of 0.6 to 1.2 mm. The longer the total length of the electron gun is, the more advantageous it is. Not very effective.

[0050]

As a result of manufacturing and evaluating the sample under the above conditions, the size of the spot on the screen has a reduction effect of about 15 to 30% in the horizontal direction corresponding to the conventional electron gun.

By applying the structure of the electron gun according to the present invention, in order to reduce the spot diameter which has a great influence on the focus, the total length of the focus electrode to which the fixed focus voltage is applied is maintained as it is. The same voltage is applied to the electrodes divided into more than one, and the interval between the electrodes is set to 0.
By forming 6 to 1.2 mm, the size of the screen spot diameter in the horizontal direction can be reduced by 15 to 30%.

Further, since it is applicable at a low cost and in a short period of time, it is possible to improve the quality of focus at an early stage.

[Brief description of drawings]

FIG. 1 is a schematic view of a general cathode ray tube.

FIG. 2 is a graph showing a change in spot diameter depending on the main lens diameter.

FIG. 3 is a diagram showing an operating principle of a VM coil.

FIG. 4 is a diagram for comparing and explaining a structure of a conventional electron gun and a structure of an electron gun according to the present invention.

FIG. 5 is a diagram illustrating a change in the spot diameter of a screen by a focus electrode to which a fixed focus voltage is applied and a coil that operates in synchronization with a differential signal of a video signal.

FIG. 6 is a diagram showing the structure of an electron gun according to the present invention.

[Explanation of symbols]

1… Stem pin 2 ... heater 3, 23 ... Cathode 4, 24 ... First electrode 5, 25 ... Second electrode 6, 26 ... Third electrode 7, 27 ... Fourth electrode 8 8 ... Fifth electrode 9, 29 ... Sixth electrode 10 ... Shield cup 11 ... BSC 12 ... Deflection yoke 13 ... Electron beam 15 ... Shadow mask 16 ... Phosphor screen 17 ... Screen 28 ... Focus electrode

Claims (4)

[Claims] 1. An electron gun including a cathode that emits an electron beam toward a phosphor screen, an anode electrode on the screen side, and a focus electrode on the cathode side, and the position of the focus electrode is the center of the magnetic field. In the cathode ray tube including a VM (Velocity Modulation) coil mounted on the neck portion of the cathode ray tube and operating in synchronization with the video signal of the circuit; the focus electrodes to which a fixed focus voltage is applied are continuously arranged. If the total length of the focus electrodes is “L” and the total distance between the electrodes is “g”, the total length of the focus electrodes is (g × 100) / L =
An electron gun for a color cathode ray tube, characterized by satisfying 5 to 30 (%). 2. The electron gun for a color cathode ray tube according to claim 1, wherein the L satisfies 4 mm <L <30 mm. 3. The electron gun for a color cathode ray tube according to claim 1, wherein the g satisfies 0.6 mm <g <1.2 mm. 4. The electron gun for a color cathode ray tube according to claim 1, wherein the focus electrodes are a set of three or more.