JP2006164921A - Color cathode-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color cathode-ray tube equipped with an electron gun assembly capable of obtaining excellent image characteristics on a whole area of a phosphor screen. <P>SOLUTION: A main lens part formed on the electron gun assembly 7 is provided with a first asymmetric field lens, a field lens with large diameter, and a second asymmetric field lens in electron beam traveling direction in this sequence. The first asymmetric field lens has a diverging action in lateral direction and a converging action in vertical direction relatively. The second asymmetric field lens has a converging action in lateral direction and a diverging action in vertical direction relatively. The field lens with large diameter has an aperture larger than that of the first asymmetric field lens and the second asymmetric field lens, and aperture diameter in lateral direction is relatively larger than that in vertical direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color cathode ray tube. In particular, the present invention relates to a color cathode ray tube equipped with an in-line type electron gun structure that emits three electron beams on the same horizontal plane.

  In recent years, a self-convergence in-line type color cathode ray tube in which three electron beams arranged in a straight line in the horizontal direction are self-concentrated over the entire area of the phosphor screen has been widely put into practical use.

  In such a color cathode ray tube, a demand for higher resolution is increasing.

  The diameter of an electron beam spot (hereinafter simply referred to as “spot”) on the phosphor screen, which is a major factor that determines the resolution, is determined by the focusing performance of the electron gun assembly that emits the electron beam. This focusing performance is generally determined by the aperture of the main lens unit, the virtual object point diameter with respect to the main lens unit, the magnification of the main lens unit, and the like. That is, the larger the aperture of the main lens portion, the smaller the virtual object point diameter, and the smaller the magnification of the main lens portion, the smaller the spot diameter can be and the resolution can be improved.

  For example, in order to enlarge the diameter of the main lens portion, Patent Document 1, Patent Document 2, and the like disclose an electron gun structure that forms an electric field superposition type lens. Further, Patent Document 3, Patent Document 4, and the like disclose an electron gun structure that forms an electric field expansion type lens.

  As shown in FIG. 3, the electric field superimposing lens 13 includes three openings respectively corresponding to three electron beams arranged on a straight line in the horizontal direction, and each of the two electrodes 11 a and 11 b arranged adjacent to each other. It is formed by providing cylindrical outer peripheral electrodes 12a and 12b having one opening common to the three electron beams having the long axis in the horizontal direction on the side facing the counterpart. The electric field superimposing lens 13 is an electric field lens that acts in common on the three electron beams passing through the three openings of the electrodes 11a and 11b. The lens aperture is enlarged by forming the electric field superimposing lens 13.

  The electric field superposition type lens 13 can increase the lens diameter in the horizontal direction due to its structure, but cannot increase the lens diameter in the vertical direction as much as the horizontal direction. For this reason, a difference occurs in the lens aperture between the horizontal direction and the vertical direction, and the focal length becomes shorter in the vertical direction than in the horizontal direction. Therefore, the electric field superimposing lens 13 has a negative astigmatism, and the electron beam that has passed through the electric field superimposing lens 13 is underfocused in the horizontal direction and overfocused in the vertical direction. For this reason, in general, in order to compensate for such negative astigmatism, the three openings formed in the electrodes 11a and 11b disposed at positions retracted from the opposing ends of the outer peripheral electrodes 12a and 12b have a vertical diameter. Is a vertically long shape larger than the horizontal diameter.

  However, if the three apertures through which the three electron beams respectively pass are formed in a vertically long shape, the distance between the edge of the aperture and the electron beam bundle in the horizontal direction is reduced, and local aberration occurs. For this reason, even if an attempt is made to increase the lens aperture of the electric field superposition type lens 13 by increasing the length in the tube axis direction of the outer peripheral electrodes 12a and 12b, the outer peripheral electrode is actually due to the above-mentioned local aberration in the horizontal direction. Expansion of the length of 12a, 12b is restricted, and it is difficult to realize a desired lens aperture.

  On the other hand, as shown in FIG. 4, the electric field expansion type lens 25 applies a medium-high voltage between a focus electrode 21 to which a medium voltage is applied and an anode electrode 23 to which a high voltage is applied. It is formed by arranging the intermediate electrode 22 to be formed. In general, the voltage obtained by dividing the voltage Eb applied to the anode electrode 23 via the resistor 24 is applied to the intermediate electrode 22 in consideration of withstand voltage characteristics. The electric field expansion type lens 25 is formed so as to widen the lens region between the focus electrode 21 and the anode electrode 23 in the tube axis direction, and forms a state equivalent to that of an apparently large-diameter lens. , Enlarge the lens aperture.

  However, the electrode forming the electric field expansion type lens 25 has three openings corresponding to the three electron beams, and there is an upper limit on the diameter of each opening. Accordingly, when the diameter of the electron beam bundle incident on the electric field expansion lens 25 is increased as in a high current, local aberrations occur, so that it is difficult to obtain sufficient lens characteristics.

  There is also known an electron gun assembly in which such an electric field expansion type lens is formed, and furthermore, quadrupole lenses having opposite polarities are arranged on the converging side and the diverging side thereof. As shown in FIG. 5, the electron gun assembly has three cathodes K arranged in-line in the horizontal direction, a control electrode 31, an acceleration electrode 32, a first focus electrode 33, a second focus electrode 34, and a first intermediate electrode 35. The second intermediate electrode 36, the anode electrode 37, and the convergence cup 38 are provided in this order. The control electrode 31 is grounded, the acceleration voltage V2 is applied to the acceleration electrode 32, and the first focus voltage Vf1 is applied to the first focus electrode 33. A dynamic focus voltage Vf2 + Vd in which an AC voltage component Vd synchronized with the deflection magnetic field is superimposed on the second focus voltage Vf2 is applied to the second focus electrode 34. An anode voltage Eb is applied to the anode electrode 37 and the convergence cup 38. One end of the resistor 39 is connected to the convergence cup 38, and the other end is grounded via the variable resistor VR. The first intermediate electrode 35 and the second intermediate electrode 36 are applied with voltages obtained by resistance division of the anode voltage Eb with the resistor 39, respectively.

  Such an electron gun assembly has a relatively divergent action in the horizontal direction and a focusing action in the vertical direction between the second focus electrode 34 and the first intermediate electrode 35 to which a dynamic focus voltage is applied. A first quadrupole lens is formed, and a second quadrupole lens having a focusing action in the horizontal direction and a diverging action in the vertical direction is formed between the second intermediate electrode 36 and the anode electrode 37. It is formed. That is, a double quadrupole lens configuration in which two quadrupole lenses are formed in an electric field expansion lens formed by the second focus electrode 34, the first intermediate electrode 35, the second intermediate electrode 36, and the anode electrode 37. A main lens portion is formed.

  In the main lens portion having such a double quadrupole lens configuration, the horizontal focusing action and the vertical divergence of the second quadrupole lens formed between the second intermediate electrode 36 and the anode electrode 37 are provided. The action cancels out the asymmetric lens component having a diverging action in the horizontal direction and a focusing action in the vertical direction, which is formed by a deflection magnetic field when the electron beam is deflected around the screen. The ellipticity of the spot shape can be improved (that is, the spot shape is made closer to a circle).

  The first quadrupole lens formed between the second focus electrode 34 and the first intermediate electrode 35 when the dynamic focus voltage applied to the second focus electrode 34 changes in synchronization with the deflection magnetic field. Since the diverging action in the horizontal direction and the focusing action in the vertical direction are changed, the distortion of the spot shape around the screen can be appropriately corrected when the electron beam is deflected around the screen.

  However, in such a lens configuration, the horizontal diverging action and the vertical focusing action of the first quadrupole lens formed between the second focus electrode 34 and the first intermediate electrode 35 are mainly used. The cross-sectional shape of the electron beam bundle incident on the lens unit is changed horizontally. However, the lens between the first intermediate electrode 35 and the second intermediate electrode 36 and the lens between the second intermediate electrode 36 and the anode electrode 37 through which the laterally elongated electron beam bundle passes thereafter are: Since both are lenses corresponding to three electron beams on a one-to-one basis, the lens aperture is relatively small. Accordingly, local aberration occurs in these lens regions, and there is a problem that the spot diameter in the horizontal direction is difficult to be reduced at the periphery of the screen.

  In addition, since the second focus electrode 34, the first intermediate electrode 35, the second intermediate electrode 36, and the anode electrode 37 that form the main lens portion each have three openings through which three electron beams pass, The capacitance formed between the electrodes adjacent in the tube axis direction is the same. That is, an alternating voltage of 66% of the dynamic focus voltage is superimposed and applied to the first intermediate electrode 35, and an alternating voltage of 33% of the dynamic focus voltage is superimposed and applied to the second intermediate electrode. Such a superimposed voltage particularly weakens the horizontal focusing action and the vertical diverging action of the second quadrupole lens formed between the second intermediate electrode 36 and the anode electrode 37. As a result, since the action of canceling out the asymmetric lens component due to the deflection magnetic field is weakened, there is a problem that the effect of improving the ellipticity of the spot shape around the screen cannot be obtained as much as expected.

  Further, Patent Document 5 and the like disclose an electron gun assembly that forms an electric field superposition expansion type lens. As shown in FIG. 6, the electron gun assembly includes three cathodes K arranged in-line in the horizontal direction, a first electrode 41, a second electrode 42, a third electrode 43, a fourth electrode 44, a fifth electrode 45, A focus electrode 46, an intermediate electrode 47, an anode electrode 48, and a convergence cup 49 are provided in this order. The first electrode 41 is grounded, and the acceleration voltage V <b> 2 is applied to the second electrode 42 and the fourth electrode 44. A dynamic focus voltage Vf + Vd in which an AC voltage component Vd synchronized with the deflection magnetic field is superimposed on the focus voltage Vf is applied to the third electrode 43 and the focus electrode 46. An anode voltage Eb is applied to the anode electrode 48 and the convergence cup 49. One end of the resistor 50 is connected to the convergence cup 49, and the other end is grounded via the variable resistor VR. A voltage obtained by dividing the anode voltage Eb by the resistor 50 is applied to the fifth electrode 45 and the intermediate electrode 47, respectively.

  On the opposite sides of the focus electrode 46 and the intermediate electrode 47 and on the opposite sides of the intermediate electrode 47 and the anode electrode 48, cylindrical outer peripheral electrodes having one opening common to the three electron beams are respectively formed. Yes. Therefore, an electric field superposition type lens is formed between the focus electrode 46 and the intermediate electrode 47 and between the intermediate electrode 47 and the anode electrode 48 as in FIG.

  Each of the focus electrode 46, the intermediate electrode 47, and the anode electrode 48 includes a plate-like electrode having three openings through which three electron beams pass. A voltage lower than the anode voltage Eb applied to the anode electrode 48 is applied to the intermediate electrode 47. Therefore, the focus electrode 46, the intermediate electrode 47, and the anode electrode 48 form an electric field expansion type lens as in FIG.

  Therefore, the main lens portion formed in the electron gun structure of FIG. 6 is called an electric field superposition expansion type lens because it has the characteristics of an electric field superposition type lens and an electric field expansion type lens.

  In this electric field superposition expansion type lens, since the electric field superposition type lens is formed between the focus electrode 46 and the intermediate electrode 47 and between the intermediate electrode 47 and the anode electrode 48, the lens aperture can be enlarged. . Furthermore, since the electric field expansion type lens is formed by the focus electrode 46, the intermediate electrode 47, and the anode electrode 48, the lens region can be enlarged in the tube axis direction. As a result, it is possible to form a main lens portion having an extremely large diameter.

  However, the electric field superposition type lens between the focus electrode 46 and the intermediate electrode 47 and the electric field superposition type lens between the intermediate electrode 47 and the anode electrode 48 are similar to the case of the electric field superposition type lens shown in FIG. The three openings formed in the plate electrodes inside each of the focus electrode 46, the intermediate electrode 47, and the anode electrode 48 need to have a vertically long shape whose vertical diameter is larger than the horizontal diameter. Therefore, the distance between the edge of the aperture and the electron beam bundle in the horizontal direction is reduced, and local aberration is generated.

  Further, since the electric field superposition expansion type main lens portion is an ultra-large aperture lens, it is necessary to set the focus voltage applied to the focus electrode 46 to be low. This focus voltage is also applied to the third electrode 43 disposed in the vicinity of the electron beam forming portion. When the voltage applied to the third electrode 43 decreases, the action of the prefocus lens formed by the second electrode 42 and the third electrode 43 decreases. Originally, the prefocus lens has a function of further accelerating and appropriately focusing the electron beam generated and accelerated by the electron beam forming unit including the cathode K, the first electrode 41, and the second electrode 42. Yes. When the action of the prefocus lens is reduced due to a decrease in the voltage applied to the third electrode 43, the divergence angle of the electron beam generated by the electron beam forming unit is increased, and the object point diameter is increased. Therefore, there is a problem that the effect of using the main lens portion as an electric field superposition expansion type ultra-large aperture lens is not sufficiently exhibited, and the focus characteristic is deteriorated in the entire screen.

Further, the lens formed between the focus electrode 46 and the intermediate electrode 47 is a large-diameter electric field superposition type lens, and does not have a dynamic focus effect like the double quadrupole lens described in FIG. In addition, the dynamic focus sensitivity deteriorates. In order to obtain the required dynamic focus effect, it is necessary to increase the applied voltage, and there is a problem that the cost of the drive circuit increases.
JP-A-57-103246 JP 59-215640 A JP 60-136133 A JP-A-62-136738 Japanese Patent Laid-Open No. 9-73867

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a color cathode ray tube including an electron gun assembly capable of obtaining good image characteristics over the entire phosphor screen. It is to provide.

  A color cathode ray tube according to the present invention includes a phosphor screen, an electron gun assembly that emits three electron beams toward the phosphor screen, and a deflection magnetic field that deflects the three electron beams in a horizontal direction and a vertical direction. A deflection yoke. The electron gun assembly includes three cathodes and a plurality of electrodes, and forms and emits the three electron beams, and the three electron beams from the electron beam forming unit emit the fluorescence. A main lens unit for focusing on the body screen.

  In the first color cathode ray tube of the present invention, the main lens unit includes a first asymmetric electric field lens, a large-aperture electric field lens, and a second asymmetric electric field lens in this order along the traveling direction of the three electron beams. Prepare. The first asymmetric electric field lens is an asymmetric lens having a diverging action in a relatively horizontal direction and a focusing action in a vertical direction, and the second asymmetric electric field lens has a focusing action in a relatively horizontal direction. The large-aperture electric field lens has a larger opening than the first asymmetric electric field lens and the second asymmetric electric field lens, and the horizontal opening diameter is a vertical opening. It is a lens that is relatively larger than the aperture.

  In the second color cathode ray tube of the present invention, the main lens portion includes at least a first electrode, a second electrode, a third electrode, and a fourth electrode along the traveling direction of the three electron beams. Prepare in order. A medium focus voltage is applied to the first electrode, and a high anode voltage is applied to the fourth electrode. Three independent openings through which the three electron beams pass are respectively formed on the second electrode side end surface of the first electrode and the third electrode side end surface of the fourth electrode, The second electrode and the third electrode are opposed to each other, and one common opening through which the three electron beams pass is formed on the side facing the respective counterparts.

  According to the present invention, it is possible to provide a color cathode ray tube including an electron gun assembly capable of obtaining good image characteristics over the entire phosphor screen.

  Hereinafter, an embodiment of a color cathode ray tube of the present invention will be described with reference to the drawings.

  FIG. 1 is a horizontal sectional view schematically showing the structure of a color cathode ray tube according to an embodiment of the present invention. As shown, the tube axis of the color cathode ray tube is the Z axis, the horizontal axis orthogonal to the Z axis is the X axis, and the vertical axis orthogonal to the Z axis and the X axis is the Y axis.

  This color cathode ray tube has an envelope in which a panel 1 and a funnel-shaped funnel 2 are integrally joined. On the inner surface of the panel 1, there is formed a phosphor screen 3 composed of a stripe or dot three-color phosphor layer that emits blue (B), green (G), and red (R). A shadow mask 4 is mounted on the inner wall surface of the panel 1 so as to face the phosphor screen 3. A large number of apertures are formed in the shadow mask 4.

  An in-line type electron gun assembly 7 is disposed in the neck portion 5 which is the finest detail of the funnel 2. The electron gun assembly 7 is composed of a center beam 6G and a pair of side beams 6B, 6R on both sides thereof, and three electron beams 6B, 6G, 6R arranged in a line in the horizontal direction toward the phosphor screen 3 along the Z axis. And exit. The electron gun structure 7 is formed by decentering the center position of the opening through which the side beams 6B and 6R pass, which are formed in the low-voltage side grid and the high-voltage side grid constituting the main lens unit, respectively. The three electron beams 6B, 6G, and 6R are self-converged at the central portion on the body screen 3.

  A deflection yoke 8 is mounted on the outside of the funnel 2. The deflection yoke 8 generates an inhomogeneous deflection magnetic field that deflects the three electron beams 6B, 6G, and 6R emitted from the electron gun assembly 7 in the horizontal direction and the vertical direction. This non-uniform deflection magnetic field is formed by a pin cushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field.

  The three electron beams 6B, 6G, and 6R emitted from the electron gun assembly 7 are each focused on the corresponding color phosphor layer on the phosphor screen 3 while being self-converged toward the phosphor screen 3. At this time, the three electron beams 6B, 6G, and 6R are scanned in the horizontal direction and the vertical direction of the phosphor screen 3 by an inhomogeneous deflection magnetic field. In this way, a color image is displayed.

  As shown in FIG. 2, the electron gun assembly 7 applied to the color cathode ray tube includes cathodes KB, KG, KR, a first grid G1, a second grid G2, and a third grid G3 arranged in a line in the horizontal direction. , Fourth grid G4, fifth grid G5, sixth grid (focus electrode) G6, first intermediate electrode GM1, second intermediate electrode GM2, seventh grid (anode electrode) G7, and convergence cup G8. The three cathodes KB, KG, KR, the nine grids, and the convergence cup G8 are arranged in this order along the traveling direction of the electron beam, and are supported and fixed by an insulating support (not shown). The convergence cup G8 is fixed by being welded to the seventh grid G7.

  The convergence cup G8 is provided with a plurality of contacts (not shown) for establishing electrical continuity with an internal conductive film deposited on the inner surface from the large diameter portion of the funnel 2 to the neck portion 5. Yes.

  A voltage of about 30 to 200 V is applied to the three cathodes KB, KG, and KR. The first grid G1 is grounded. An acceleration voltage V2 having a low potential of about 500V to 800V is applied to the second grid G2 from the outside of the cathode ray tube.

  The third grid G3 and the fifth grid G5 are connected in the tube, and a constant first focus voltage Vf1 of about 6 to 9 kV is supplied from outside the cathode ray tube.

  The sixth grid G6 has a dynamic focus voltage Vf2 + Vd in which an AC voltage component Vd synchronized with a deflection magnetic field generated by the deflection yoke is superimposed on a second focus voltage Vf2 substantially equal to the first focus voltage Vf1 from the outside of the cathode ray tube. Applied.

  The seventh grid G7 and the convergence cup G8 are supplied with an anode voltage Eb of about 25 to 30 kV from the outside of the cathode ray tube.

  In the vicinity of the electron gun assembly 7, a resistor R1 is disposed as shown in FIG. One end a of the resistor R1 is connected to a convergence cup G8 (or the seventh grid G7), and the other end c is grounded via a variable resistor VR outside the tube (may be directly grounded). . The resistor R1 includes voltage supply terminals b1 and b2 for supplying a voltage to the grid of the electron gun assembly 7 in the middle thereof.

  The fourth grid G4 and the first intermediate electrode GM1 are connected in the tube, and are connected to the voltage supply terminal b1 on the resistor R1 in the vicinity of the first intermediate electrode GM1. A voltage obtained by resistively dividing the anode voltage Eb, for example, a voltage of about 40% of the anode voltage Eb, is applied to the fourth grid G4 and the first intermediate electrode GM1 via the voltage supply terminal b1. The

  The second intermediate electrode GM2 is connected to the voltage supply terminal b2 on the resistor R1 in the vicinity thereof. A voltage obtained by resistance-dividing the anode voltage Eb, for example, about 60 to 65% of the anode voltage Eb is applied to the second intermediate electrode GM2 via the voltage supply terminal b2.

  Each of the first grid G1 and the second grid G2 is a thin plate-like electrode, and is formed by drilling the plate surface. Has an opening.

  The third grid G3 is formed by joining a pair of cup-shaped electrodes. The end face of the cup-shaped electrode facing the second grid G2 is provided with three openings each having a slightly larger three-electron beam having a diameter of about 1 mm to 1.5 mm. Further, the end face of the cup-shaped electrode facing the fourth grid G4 is provided with three circular openings through which three electron beams each having a diameter of about 3 mm to 6 mm pass.

  The fourth grid G4 is formed by joining a pair of cup-shaped electrodes. The end face of each cup-shaped electrode has three circular openings through which three electron beams each having a diameter of about 3 mm to 6 mm pass.

  The fifth grid G5 is formed by joining a plurality of cup-shaped electrodes. The surface facing the sixth grid G6 has three vertically long non-circular openings with the major axis direction as the vertical direction through which the three electron beams pass. The non-circular opening is formed in a rectangular shape having a long side in the vertical direction, for example. The other end face of each cup-shaped electrode is provided with three circular openings through which three electron beams having a diameter of about 3 mm to 6 mm pass.

  The sixth grid G6 is formed by joining a plurality of cup-shaped electrodes. The surface facing the fifth grid G5 is provided with three horizontally long non-circular openings with the major axis direction as the horizontal direction through which the three electron beams respectively pass. For example, the non-circular opening is formed in a rectangular shape having a long side in the horizontal direction. In addition, the surface facing the first intermediate electrode GM1 includes three horizontally long non-circular openings with the major axis direction as the horizontal direction through which the three electron beams pass.

  The first intermediate electrode GM1 is formed by one cup-shaped electrode. The surface of the first intermediate electrode GM1 facing the sixth grid G6 is provided with three circular openings through which three electron beams each having a diameter of about 3 mm to 6 mm pass. On the second intermediate electrode GM2 side of the first intermediate electrode GM1, a cylindrical outer peripheral electrode having one common opening through which three electron beams pass is provided.

  The second intermediate electrode GM2 is formed by one cup-shaped electrode. The surface of the second intermediate electrode GM2 facing the first intermediate electrode GM1 is provided with a cylindrical outer peripheral electrode having one common opening through which three electron beams pass. The surface of the second intermediate electrode GM2 facing the seventh grid G7 is provided with three circular openings through which three electron beams having a diameter of about 3 mm to 6 mm pass.

  The seventh grid G7 is formed by joining a plurality of cup-shaped electrodes. The surface of the seventh grid G7 facing the second intermediate electrode GM2 has three horizontally long non-circular openings with the major axis direction as the horizontal direction through which the three electron beams pass.

  The convergence cup G8 has a cup shape and is welded to the seventh grid G7. The end face welded to the seventh grid G7 of the convergence G8 is provided with three circular openings through which three electron beams each having a diameter of about 3 mm to 6 mm pass.

  The first grid G1 and the second grid G2 are arranged to face each other with a very narrow space of 0.5 mm or less. The second grid G2 to the seventh grid G7 are arranged to face each other with an interval of about 0.5 to 1 mm between grids adjacent in the Z-axis direction.

  In the electron gun assembly 7 configured as described above, the cathodes KB, KG, KR, the first grid G1, and the second grid G2 form an electron beam forming unit that forms and emits three electron beams. The second grid G2 and the third grid G3 form a prefocus lens for prefocusing the electron beam generated from the electron beam forming unit. The third grid G3, the fourth grid G4, and the fifth grid G5 form a sub lens that further pre-focuses the pre-focused electron beam.

  Between the fifth grid G5 and the sixth grid G6, a quadrupole lens whose lens intensity is changed by a dynamic focus voltage Vd that varies with the deflection amount of the electron beam is formed.

  The sixth grid G6, the first intermediate electrode GM1, the second intermediate electrode GM2, and the seventh grid G7 form a main lens unit that finally focuses the electron beam on the phosphor screen. The main lens portion is configured by partially combining an electric field superposition type lens and an electric field expansion type lens.

  As shown in FIG. 2, the main lens unit has a large-aperture electric field lens L1 that acts in common with respect to three electron beams between the first intermediate electrode GM1 and the second intermediate electrode GM2. The electric field lens L1 is formed by an outer peripheral electrode provided on the side of the first intermediate electrode GM1 and the second intermediate electrode GM2 facing each other. The vertical opening diameter of the outer peripheral electrode is larger than the horizontal opening diameter. Therefore, the horizontal direction opening diameter of the electric field lens L1 is relatively larger than the vertical direction opening diameter. The electric field lens L1 has an opening larger than those of a first asymmetric electric field lens L2 and a second asymmetric electric field lens L3 described later.

  The main lens portion includes three first asymmetric electric field lenses L2 that individually act on each of the three electron beams between the sixth grid G6 and the first intermediate electrode GM1, which are on the focusing region side. Have. The asymmetry of the first asymmetrical electric field lens L2 is due to the fact that the three apertures through which the three electron beams formed in the sixth grid G6 respectively pass have an asymmetric shape with the major axis direction as the horizontal direction. The first asymmetric electric field lens L2 has a relatively diverging action in the horizontal direction and a focusing action in the vertical direction.

  Further, the main lens portion includes three second asymmetric electric field lenses L3 that individually act on each of the three electron beams between the second intermediate electrode GM2 and the seventh grid G7, which are on the divergence region side. Have. The asymmetry of the second asymmetric electric field lens L3 is due to the fact that the three apertures through which the three electron beams formed in the seventh grid G7 respectively pass have an asymmetric shape with the major axis direction as the horizontal direction. The second asymmetric electric field lens L3 has a focusing action in the horizontal direction and a diverging action in the vertical direction.

  According to the above-described electron gun assembly 7 of the present invention, the first asymmetry having a diverging action in the horizontal direction and a focusing action in the vertical direction between the sixth grid G6 and the first intermediate electrode GM1. An electric field lens L2 is formed, and a large-aperture electric field lens L1 acting in common with respect to the three electron beams is formed between the first intermediate electrode GM1 and the second intermediate electrode GM2, and the second intermediate electrode GM2 and the seventh intermediate electrode GM2 are formed. A second asymmetrical electric field lens L3 having a focusing action in the horizontal direction and a diverging action in the vertical direction is formed between the grid G7.

  Thereby, the following effects are acquired.

  A deflecting magnetic field is formed when the electron beam is deflected to the periphery of the screen by the second asymmetrical electric field lens L3 having a focusing action in the horizontal direction and a diverging action in the vertical direction at a position close to the deflection magnetic field. The asymmetric lens component having a diverging action in the horizontal direction and a focusing action in the vertical direction can be effectively canceled out. Therefore, the ellipticity of the spot shape around the screen can be effectively improved.

  Further, the dynamic focus voltage applied to the sixth grid G6 changes in synchronization with the deflection magnetic field, so that the first asymmetric electric field lens L2 formed between the sixth grid G6 and the first intermediate electrode GM1 Since the diverging action in the horizontal direction and the focusing action change in the vertical direction, the dynamic focus can be effectively acted and the dynamic focus voltage can be reduced.

  Each opening of the first intermediate electrode GM1 and the second intermediate electrode GM2 forming the large-aperture electric field lens L1 immediately after the first asymmetric electric field lens L2 is one opening common to the three electron beams, and is arranged in the horizontal direction. It has a relatively large opening diameter. Therefore, the first asymmetric electric field lens L2 has three apertures corresponding to each of the three electron beams even if the cross-sectional shape of the electron beam bundle is horizontally long due to the diverging action in the horizontal direction and the focusing action in the vertical direction. The local aberration that occurs in the conventional electric field expansion type lens (see FIG. 5) does not occur. Therefore, the electron beam bundle can be sufficiently diverged in the horizontal direction by the first asymmetric electric field lens L2, and as a result, the horizontal spot diameter around the screen can be reduced.

  In addition, each opening of the first intermediate electrode GM1 and the second intermediate electrode GM2 forming the large-aperture electric field lens L1 is one opening common to the three electron beams, so the first intermediate electrode GM1 and the second intermediate electrode GM2 Is made smaller than the capacitance between the sixth grid G6 and the first intermediate electrode GM1 and the capacitance between the second intermediate electrode GM2 and the seventh grid G7. Can do. As a result, it is possible to suppress the phenomenon of dynamic focus voltage superimposition to the second intermediate electrode GM2 via the capacitance, and thus the second asymmetric electric field formed between the second intermediate electrode GM2 and the seventh grid G7. The focusing action in the horizontal direction and the diverging action in the vertical direction of the lens L3 are not weakened as in the conventional electric field expansion lens (see FIG. 5). Therefore, the action of canceling the asymmetric lens component having a diverging action in the horizontal direction and having a focusing action in the vertical direction formed by the deflection magnetic field does not weaken even when the electron beam is deflected to the periphery of the screen. Therefore, the ellipticity around the screen can be effectively improved.

  In addition, since three openings corresponding to each of the three electron beams are formed on the end surface on the first intermediate electrode GM1 side of the sixth grid G6 and the end surface on the second intermediate electrode GM2 side of the seventh grid G7, Unlike the conventional electric field superposition expansion type main lens portion (see FIG. 6), the gentle main lens portion electric field formed in the region from the sixth grid G6 to the seventh grid G7 is different from the conventional electric field superposition extended type main lens portion (see FIG. 6). Does not penetrate into G7. For this reason, the main lens portion does not have an extremely large aperture, and the center of the main lens portion does not move toward the cathodes KB, KG, KR, so that it is not necessary to extremely reduce the focus voltage. . Therefore, the action of the prefocus lens formed between the second grid G2 and the third grid G3 is not extremely weakened, the divergence angle of the electron beam emitted from the electron beam forming unit is reduced, and the object point It is possible to enter the main lens portion while keeping the diameter small. Therefore, it is possible to easily avoid a situation in which the focus is deteriorated as in the conventional electric field superposition expansion type main lens portion (see FIG. 6).

  Further, the balance between the first asymmetric electric field lens L2 between the sixth grid G6 and the first intermediate electrode GM1 and the second asymmetric electric field lens L3 between the second intermediate electrode GM2 and the seventh grid G7 is changed. Thereby, the negative astigmatism component produced | generated by the outer peripheral electrode formed in the opposing surface side with each other partner of 1st intermediate electrode GM1 and 2nd intermediate electrode GM2 can be negated easily. Therefore, it is not necessary to form the three openings respectively formed in the vertically long shape on the end face of the first intermediate electrode GM1 on the sixth grid G6 side and the end face of the second intermediate electrode GM2 on the seventh grid G7 side. Therefore, the problem that local aberrations are generated by making the three apertures corresponding to the three electron beams into a vertically long shape, which has been a problem in the conventional electric field superimposing lens and the electric field superimposing expansion lens, is avoided. be able to.

  The field of application of the present invention is not particularly limited, and can be widely used for color cathode ray tubes such as a television or a computer display.

1 is a horizontal sectional view schematically showing the structure of a color cathode ray tube according to an embodiment of the present invention. 1 is a horizontal sectional view schematically showing the structure of an electron gun assembly applied to a color cathode ray tube according to an embodiment of the present invention. FIG. 6 is a horizontal sectional view schematically showing a configuration of an electric field superposition type lens in a conventional electron gun assembly. FIG. 5 is a horizontal sectional view schematically showing a configuration of an electric field expansion type lens in a conventional electron gun structure. It is a vertical direction sectional view showing roughly the composition of the conventional electron gun structure which combined the electric field expansion type main lens part and two quadrupole lenses. It is a horizontal direction sectional view showing roughly the composition of the conventional electron gun structure which forms an electric field superposition expansion type main lens part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Panel 2 ... Funnel 3 ... Phosphor screen 4 ... Shadow mask 5 ... Neck part 6B, 6G, 6R ... Electron beam 7 ... Electron gun structure 8 ... Deflection yokes KB, KG, KR ... cathode G1 ... first grid G2 ... second grid G3 ... third grid G4 ... fourth grid G5 ... fifth grid G6 ... 6th grid (focus electrode)
GM1 ... 1st intermediate electrode GM2 ... 2nd intermediate electrode G7 ... 7th grid (anode electrode)
G8 ... Convergence cup R1 ... Resistor L1 ... Large-aperture electric field lens L2 ... First asymmetric electric field lens L3 ... Second asymmetric electric field lens

Claims (9)

A phosphor screen; an electron gun assembly that emits three electron beams toward the phosphor screen; and a deflection yoke that generates a deflection magnetic field that deflects the three electron beams in a horizontal direction and a vertical direction. A color cathode ray tube,
The electron gun assembly includes three cathodes and a plurality of electrodes, and forms and emits the three electron beams, and the three electron beams from the electron beam forming unit emit the fluorescence. A main lens unit for focusing on the body screen,
The main lens unit includes a first asymmetric electric field lens, a large-aperture electric field lens, and a second asymmetric electric field lens in this order along the traveling direction of the three electron beams.
The first asymmetric electric field lens is an asymmetric lens having a diverging action in a relatively horizontal direction and a focusing action in a vertical direction;
The second asymmetric electric field lens is an asymmetric lens having a focusing action in a relatively horizontal direction and a diverging action in a vertical direction;
The large-aperture electric field lens has a larger opening than the first asymmetric electric field lens and the second asymmetric electric field lens, and the horizontal opening diameter is relatively larger than the vertical opening diameter. Color cathode ray tube. A phosphor screen; an electron gun assembly that emits three electron beams toward the phosphor screen; and a deflection yoke that generates a deflection magnetic field that deflects the three electron beams in a horizontal direction and a vertical direction. A color cathode ray tube,
The electron gun assembly includes three cathodes and a plurality of electrodes, and forms and emits the three electron beams, and the three electron beams from the electron beam forming unit emit the fluorescence. A main lens unit for focusing on the body screen,
The main lens unit includes at least a first electrode, a second electrode, a third electrode, and a fourth electrode in this order along the traveling direction of the three electron beams,
A medium focus voltage is applied to the first electrode,
A high anode voltage is applied to the fourth electrode,
Three independent openings through which the three electron beams pass are respectively formed on the second electrode side end surface of the first electrode and the third electrode side end surface of the fourth electrode,
The second electrode and the third electrode are opposed to each other, and a common opening through which the three electron beams pass is formed on the opposite surface side of each counterpart. Color cathode ray tube.   The first electrode and the second electrode are opposed to each other, and three first asymmetrical electric field lenses that respectively act on the three electron beams are formed between the first electrode and the second electrode. The color cathode ray tube according to claim 2.   The third electrode and the fourth electrode face each other, and three second asymmetric electric field lenses that respectively act on the three electron beams are formed between the third electrode and the fourth electrode. The color cathode ray tube according to claim 2.   4. The color cathode ray tube according to claim 3, wherein the first asymmetric electric field lens is an asymmetric lens having a diverging action in a relatively horizontal direction and a focusing action in a vertical direction.   5. The color cathode ray tube according to claim 4, wherein the second asymmetric electric field lens is an asymmetric lens having a focusing action in a relatively horizontal direction and a diverging action in a vertical direction.   3. The color cathode ray tube according to claim 2, wherein the three openings formed on the second electrode side end face of the first electrode have an asymmetric shape with a major axis direction as a horizontal direction. 4.   3. The color cathode ray tube according to claim 2, wherein the three openings formed in the third electrode side end face of the fourth electrode have an asymmetric shape with a major axis direction as a horizontal direction. A voltage obtained by resistance-dividing the anode voltage applied to the fourth electrode with a resistor disposed in the vicinity of the electron gun structure is applied to the second electrode and the third electrode. The color cathode ray tube according to claim 2.

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