KR20020021477A - Electron gun for color cathode ray tube - Google Patents

Abstract

PURPOSE: An electron gun for a color cathode ray tube is provided to minimize asymmetry feature of electron beam shape in deflection of R and B electron beams by changing lens depending on scanning locations of the electron beams by applying dynamic focus voltage to electrodes of the electron gun. CONSTITUTION: An electron gun for a color cathode ray tube comprises triple cathodes(21), a control electrode(22) and a screen electrode(23) arranged in line, a first to a fourth focus electrodes(24-27) for forming at least two quadruple lens and auxiliary lens for focusing and accelerating an electron beam, and a final acceleration electrode(28) adjacent to the fourth focus electrode(27) for forming a main lens. An anode voltage is applied to the final acceleration electrode(28). A dynamic focus voltage is applied to the fourth focus electrode(27). A voltage that is lowered from the dynamic focus voltage by a resistor(30) is applied to the second focus electrode(25). A voltage that is lower than the dynamic focus voltage is applied to the first and the third electrodes(24,26).

Description

Electron gun for color cathode ray tube

The present invention relates to an electron gun device, and more particularly, to an electron gun for a color cathode ray tube having an improved wiring structure of voltage applied to an electrode constituting the electron gun.

A conventional colored cathode ray tube utilizing the principle of a triode is shown in FIG. 1. Referring to the drawings, the cathode ray tube is a panel 11 having a fluorescent film having a predetermined pattern formed on an inner surface thereof, and a neck portion 13a and a deflection yoke, in which an electron gun 16 is coupled to be sealed to the panel 11. It consists of a funnel 13 having a cone portion 13b provided with 17). At the end of the neck portion 13a, a lead pin 18 for applying a predetermined voltage to each electrode of the electron gun 16 is provided.

In the cathode ray tube configured as described above, the electron beam emitted from the electron gun 16 is selectively deflected by the horizontal deflection field and the vertical deflection field formed by the deflection yoke 17 to excite the phosphor of the fluorescent film to form an image. do. In this process, when the electron beam emitted from the electron gun 16 is deflected horizontally by the deflection yoke 17, the horizontal cushion magnetic field of the pincushion type focuses the electron beam in the vertical direction to make the cross section crosswise. . In addition, when the electron beam is deflected in the vertical direction by the deflection yoke 17, the barrel-type vertical deflection magnetic field emits the electron beam to make the cross section crosswise. The transverse distortion of the cross section of the electron beam is intensified toward the periphery of the screen surface of the panel 11 to form a halo around the focal point of the electron beam. Therefore, the shape of the electron beam landing on the fluorescent film becomes uneven and the focus characteristic is deteriorated, so that the resolution of the image is reduced. In particular, among the three electron beams (hereinafter referred to as R, G, and B electron beams) irradiated from the inline electron gun, the electron beams on both sides are different in size when they are deflected to the left and right of the screen surface.

In order to solve such a problem, a conventional electron focus electron gun has been developed. That is, the dynamic focus electron gun includes a plurality of focus electrodes and forms a quadrupole lens between the final acceleration electrode and the focus electrode adjacent to the final acceleration electrode or between the focus electrodes, and the quadrupole By applying a dynamic focus voltage synchronized with the deflection signal to at least one focus electrode forming the lens, distortion of the electron beam cross section due to the nonuniform magnetic field of the deflection yoke is compensated.

An example of such a dynamic focus electron gun is disclosed in US Pat. No. 4,945,284. The electron gun includes at least two focusing electrodes electrically connected by a resistance element to form an electron lens, and a predetermined AC voltage is applied to one of the focusing electrodes from a flyback transformer which is a voltage generator. Therefore, the AC voltage reduced by the resistance element is applied to the other focusing electrode connected by the resistance element.

Another example of a conventional dynamic focus electron gun is disclosed in US Pat. No. 5,519,290 and shown in FIG. As shown in the drawing, the cathode K, which is an electron emission source, and the first to seventh grids G1-G7 that are sequentially installed from the cathode K to form an electron lens are provided. Each of the grids G1 to G7 has electron beam through holes arranged in a row, and the elongated electron beam through holes H1 and the elongated electron beams are formed on opposite surfaces of the fifth and sixth grids G5 and G6. Passing holes H2 are formed, respectively. The dynamic focus voltage Vf synchronized with the deflection signal is applied to the third and sixth grids G3 and G6, and the voltages applied to the sixth grid G6 are the resistors R and fifth and sixth. It is efficiently reduced in pressure using the capacitance between the grids G5 and G6 and applied to the fifth grid G5.

The dynamic focus electron gun as described above may change the capacitance between the electrodes and the inherent characteristics of the resistor connecting the fifth and sixth grids during the electron gun manufacturing process, which makes it difficult to control the pressure reduction of the voltage and deteriorates the focus characteristic. For example, the variation of the electrode surface area during electrode manufacturing by the mold or the gap between the electrodes during the manufacturing process of the electron gun is a factor of changing the capacitance. In addition, since only a simple dynamic focus voltage is applied, variations in the electron beam cross-section due to deflection to the periphery of the screen surface of the R and B electron beams are severe.

The present invention has been made to solve the above problems, by applying a dynamic focus voltage applied to the electrode of the electron gun to change the lens according to the dice of the electron beam, the electron beam shape when the R, B electron beam is deflected to the periphery of the screen surface The purpose is to provide an electron gun for color cathode ray tube that can minimize the asymmetry of the.

1 is a cross-sectional view of a common color cathode ray tube,

2 is a cross-sectional view of a conventional color cathode ray tube showing a voltage application state.

Figure 3 is a perspective view of an electron gun for a color cathode ray tube according to the present invention showing a voltage applied state.

The present invention to achieve the above object,

First, second, third, and four focus electrodes forming an electron emission source, at least two quadrupole lenses focusing and accelerating the electron beam emitted from the electron emission source, and adjacent to the fourth focus electrode A final acceleration electrode forming a lens,

A predetermined focus voltage is applied to the first and third focus electrodes, a dynamic focus voltage synchronized with a deflection signal is applied to the fourth focus electrode, and the dynamic focus voltage is decompressed to the second focus electrode by a resistor. Characterized in that it is applied.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The electron gun for the color cathode ray tube according to the present invention forms a three-pole portion, as shown in FIG. 3, three cathodes 21 arranged inline, a control electrode 22, a screen electrode 23, and an electron beam. First, second, third, and four focus electrodes 24, 25, 26, and 27 forming at least two quadrupole lenses and auxiliary lenses for focusing and accelerating the light; And a final accelerating electrode 28 installed adjacent to the main lens. Here, each electrode constituting the electron gun is formed with three electron beam through holes for forming an electron lens or a large diameter electron beam through hole through which three electron beams emitted from the respective cathodes 21 pass. An elongated electron beam through hole 25bh is formed in the emission side surface 25b of the second focus electrode 25 to form at least two quadrupole lenses. In addition, a circular electron beam through hole 26ah is formed at the incident side surface 26a of the third focus electrode 26, and an elongated electron beam through hole is formed at the emission side surface 26b of the third focus electrode 26. 26bh) is formed. A circular electron beam through hole 27ah is formed in the incident side surface 27a of the fourth focus electrode 27. The shape of the elongated electron beam through hole may be formed in the shape of a rectangle or a key groove, but is not limited thereto. On the exit side of the fourth focus electrode 27 and on the incidence side of the final acceleration electrode 28, large-diameter electron beam through holes are formed to form a main lens, and internal electrodes having three small-diameter electron beam through holes are formed therein. Can be.

As described above, a predetermined voltage is applied to each electrode constituting the electron gun, which will be described in detail as follows.

First, the final accelerating electrode 28 is supplied with an enwood voltage VE of 25 to 30 kV applied to the internal conductive film, and the fourth focus electrode 27 is synchronized with a deflection signal and is about 28% of the enwood voltage. The dynamic focus voltage VF is applied, and the voltage Vd1 obtained by depressurizing the dynamic focus voltage VD using the resistor 30 is applied to the second focus electrode 25. In addition, a focus voltage VF lower than a predetermined dynamic focus voltage is applied to the first and third focus electrodes 24 and 26. A predetermined constant voltage VS1 (VS2) is applied to the control electrode and the screen electrode, respectively. The resistor 30 for reducing the dynamic focus voltage may be located inside the neck portion of the cathode ray tube or installed at the end of the neck portion, and may be installed between the lead pins for applying a voltage to each electrode.

In the electron gun for the color cathode ray tube configured as described above, when a predetermined voltage is applied to the electron emission source 21, each electrode and the deflection yoke 17 (see Fig. 1) of the device, an electron lens is formed between the electrodes. . In particular, a dynamic quadrupole lens is formed between the second and third focus electrodes 25 and 26 and the second and fourth focus electrodes 26 and 27, and the fourth focus electrode 27 and the final Between the acceleration electrodes 28, a main lens whose magnification is adjusted according to the change of the dynamic focus voltage is formed. Therefore, the electron beam emitted from the cathode 21 is multi-focused by the quadrupole lenses formed between the focus electrodes, and the cross section of the electron beam is elongated by the quadrupole lens effect, so that the deflection magnetic field of the deflection yoke. The distortion of the multi-sided electron beam is compensated for.

The effect of the application of the reduced voltage using the resistor is obtained from the following equation.

δd = a ln {(h / V) * (1 / f) * (1 / R)}

Where δd is the amount of decrease in the waveform by the interelectrode capacitance and the resistor of the electron gun, a is a constant determined by the interelectrode capacitance, f is the frequency of the dynamic focus voltage, h is the amplitude of the dynamic focus voltage, and R is the resistance of the resistor. The resistance, V, represents the dynamic focus voltage.

From the above equation, it can be seen that as the amplitude of the applied focus voltage increases, the effect of reducing the voltage by the resistance increases. That is, when the electron beam is deflected to the periphery of the screen, the waveform of the supplied dynamic focus voltage has a large amplitude, and the voltage is caused by the capacitance between the resistor 30 and the second and third focus electrodes 25 and 26. The amount of descent also increases.

Accordingly, as the degree of deflection of the electron beam increases, the voltage difference between the second and third focus electrodes 25 and 26 increases, thereby improving the focus characteristic of the electron beam passing through the quadrupole lens.

The electron gun for the color cathode ray tube according to the present invention can reduce the distortion of the cross section and the deviation of the electron beam size due to the deflection of the three electron beams. Such an electron gun is applicable to a cathode ray tube for a monitor or a television.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and may be modified by those skilled in the art within the technical scope of the present invention.

Claims (1)

First, second, third, and four focus electrodes forming an electron emission source, at least two quadrupole lenses focusing and accelerating the electron beam emitted from the electron emission source, and adjacent to the fourth focus electrode A final acceleration electrode forming a lens, A predetermined focus voltage is applied to the first and third focus electrodes, a dynamic focus voltage synchronized with a deflection signal is applied to the fourth focus electrode, and the dynamic focus voltage is decompressed to the second focus electrode by a resistor. Electron gun for color cathode ray tube, characterized in that applied.