EP1209718A1

EP1209718A1 - Color picture tube

Info

Publication number: EP1209718A1
Application number: EP00125213A
Authority: EP
Inventors: Toshihiko Tanaka
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2000-11-22
Filing date: 2000-11-22
Publication date: 2002-05-29

Abstract

A color picture tube having a panel (1) whose outer surface is approximately flat and a shadow mask (5) having a curvature, wherein to increase the curvature of the shadow mask, two electromagnetic quadruple lenses (14, 15) which change the effective dimension s to determine the curvature of the shadow mask are provided. Both of these two electromagnetic quadruple lenses are arranged at the cathode side of an electron gun (9) rather than at a horizontal deflection coil of a deflection yoke (10).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inline type color picture tube.

2.Description of the Related Art

For the purpose of ensuring the favorable visibility of a screen and preventing the glare due to the reflection of external light and for achieving other purposes, a color picture tube having a flat panel outer surface has been developed. As means to realize these purposes, there has been known a method which gives a curvature to the panel inner surface while maintaining the flat panel outer surface. This method has an advantage that the method allows a shadow mask to have a curved surface so that the conventional shadow mask manufacturing technique is available. On the other hand, it becomes necessary to give an excessively large curvature to the inner surface of the panel compared to the outer surface of the panel and hence, the thickness of glass at the periphery of the panel becomes excessively thick compared to the thickness of glass at the center of the panel. This gives rise to problems such as the difference of brightness between the center and the periphery of a phosphor screen and the deterioration of feeling of flatness caused by the influence of the curved surface of the panel inner surface. Accordingly, when the panel outer surface is flat, the curvature of the panel inner surface is preferably as small as possible. On the other hand, the shadow mask can be manufactured easier when the curvature thereof is large. As a method to solve the problem, there has been proposed a method which makes the curvature of the shadow mask greater than the curvature of the panel inner surface by effectively making the dimension s of the distance between electron beams at the periphery of a screen smaller than the dimension s of the distance between electron beams at the center of the screen. As a literature which describes such a technique, a report of IDW (International Display Workshop)'98, pages 412-416 is named. This literature describes a principle which effectively reduces the dimension s at the periphery by using two electromagnetic quadruple lenses. In this literature, two electromagnetic quadruple lenses, that is, the first and second electromagnetic quadruple lenses are used, wherein the second electromagnetic quadruple lens which is close to a phosphor screen is arranged in the deflection magnetic field. That is, the literature discloses a constitution in which the dimension s is largely changed in the deflection magnetic field. However, when the dimension s is largely changed in the deflection magnetic field, it becomes difficult to control the convergence and the color purity.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a color picture tube with improved convergence and color purity.
This object is achieved by the color tube as set out in claims 1 and 9, respectively. The dependent claims refer to preferred embodiments of the invention.
The first invention also changes the dimension s at the center of a screen and at the periphery of the screen corresponding to a deflection current using two electromagnetic quadruple lenses. In the first invention, two electromagnetic quadruple lenses are arranged at a side closer to a cathode of an electron gun than a horizontal deflection coil. Due to such a constitution, two electromagnetic quadruple lenses are substantially arranged outside the deflection magnetic field. Accordingly, it is unnecessary to largely change the dimension s in the deflection magnetic field and hence, the control of the convergence and the purity can be performed easily. According to the first invention, it becomes possible to largely change the dimension s which substantially determines the curvature of the shadow mask while maintaining the level of convergence and purity. Accordingly, even when the outer surface is flat, it becomes possible to give a relatively large curvature to a shadow mask and hence, the shadow mask can maintain the practical strength.
According to the second invention, when electron beams scan a central portion of the screen, the first electromagnetic quadruple lens has a function of moving the side electron beams away from the center electron beam and the second electromagnetic quadruple lens has a function of making the side electron beams parallel to the center electron beam. Along with the increase of the deflection angle, the first electromagnetic quadruple lens weakens the function of moving the side electron beams away from the center electron beam and the second electromagnetic quadruple lens maintains the function of making the side electron beams parallel to the center electron beam. Accordingly, the dimension s at the periphery of the screen can be substantially made smaller than the dimension s at the center of the screen so that the curvature of the shadow mask can be increased. According to this second invention, in the periphery of the screen where the control of convergence and purity is difficult, since the change of dimension s can. be made small, the second electromagnetic quadruple lens may be arranged in the deflection magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a color picture tube of the present invention.
Fig. 2 is an explanatory view showing the arrangement of slots formed in a shadow mask.
Fig. 3 is a detailed view of a panel.
Fig. 4 is an explanatory view of a prior art where the dimension s is substantially changed.
Fig. 5 is an explanatory view of the present invention.
Fig. 6 and Fig. 7 are explanatory views showing the first embodiment of the present invention.
Fig. 8 is a detailed view of an essential part of the present invention.
Fig. 9, Fig. 10 and Fig. 11 are detailed views of an electromagnetic quadruple portion of the present invention.
Fig. 12 and Fig. 13 are explanatory views showing the second embodiment of the present invention.
Fig. 14 and Fig. 15 are explanatory views showing the third embodiment of the present invention.
Fig. 16 is a view showing an example of an electron gun.
Fig. 17 is a perspective view showing an example of a main lens portion of the electron gun.
Fig. 18 is a view showing an example of a shadow mask used is a display tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is explained in detail hereinafter in conjunction with embodiments shown in attached drawings.
Fig. 1 is a schematic view showing a color cathode ray tube having a flat outer surface. A panel 1 has a flat outer surface and a curved inner surface. The panel inner surface is provided with a curvature to give a curvature to a shadow mask 5 which faces the panel inner surface in an opposed manner. A neck 2 mounts an electron gun 9 arranged in an inline array therein and is contiguously connected with the panel 1 by way of a funnel 3. A crossing point 32 where a reference line 31 and a tube axis cross each other is defined as a deflection center. An angle made by a line which connects a point where an electron beam 91 impinges on a phosphor surface 4 and the deflection center 32 and a tube axis is defined as a deflection angle . This reference line 32 becomes a basis in designing the color picture tube and is set at a position closer to the panel side than a seal portion defined between the neck 2 and the funnel 3. Here, the maximum deflection angle means a doubled value of an angle made by a line which connects a diagonal axis end portion of an effective screen of the panel inner surface and the deflection center 32 and the tube axis. The maximum deflection angle in this embodiment is set to approximately 110 degrees. A phosphor in a stripe pattern is formed on the phosphor screen 4. The shadow mask 5 is provided with a large number of slot apertures and is supported by means of a support frame 6. The support frame 6 is mounted on the panel 1 by way of springs 8. Fig. 2 shows an example of the slot aperture arrangement of the shadow mask 5. Pm indicates a horizontal pitch of the slots 51. An inner magnetic shield 7 is mounted on the support frame 6. A deflection yoke 10 which deflects electron beams is mounted on a cone portion 33 of the funnel 3. An essential part of the deflection yoke 10 is comprised of a horizontal deflection coil 101, a separator 102, a vertical deflection coil 103 and a core 104. Rod-like magnets 11 which adjust the raster distortion and convergence are mounted above and below the horizontal deflection coil 101. With a magnet assembly 12, the adjustment of the convergence or the purity of the electron beams is performed. A tension band 13 prevents an implosion of the bulb. The coils forming a first electromagnetic quadruple lens 14 (first electromagnetic quadruple coils) and the coils forming a second electromagnetic quadruple lens 15 (second electromagnetic quadruple coils) are arranged between the deflection yoke 10 and the magnet assembly 12.
The outer surface of the panel 1 is made flat or has an extremely large radius of curvature. The curved surface of the panel is generally obtained by determining a coefficient A1 or A8 in an equation Z = A1X2 + A2X4 + A3Y2 + A4 X2Y2 + A5 X4Y2 + A6Y4 + A7 X2Y4 + A8 X4Y4 wherein Z is a drop amount from the panel center. An example of the panel curved surface obtained by applying the present invention to a 36V type CPT is shown in following tables.

Outer surface:

A1 0.1156035E-04 A5 -0.1309278E-19

A2 0.1545012E-14 A6 0.9600291E-14

A3 0.2125280E-04 A7 -0.3875353E-19

A4 -0.2866930E-10 A8 0.4856608E-25

Inner surface:

A1 0.3839346E-04 A5 -0.5680002E-17

A2 0.5662136E-13 A6 0.3385039E-11

A3 0.1499420E-03 A7 -0.2802914E-16

A4 -0.4172959E-09 A8 0.6708166E-22
In the panel having such panel surfaces, the radii of curvature are different depending on the locations. As an evaluation of the flatness of the panel, the equivalent radius of curvature which is based on the drop amount in the diagonal direction shown in Fig. 3 can be employed. In this case, by setting the half of the effective diameter in the diagonal direction as Dd and the drop amount as Zd, the equivalent radius of curvature Rd in the diagonal direction can be expressed as Rd = (Dd² + Zd²)/2Zd as shown in Fig. 3. Even when the radius of curvature is same, the influence to the flatness differs depending on the dimension of the screen. Accordingly, as an expression method which normalizes the flatness of the panel surface, there has been proposed a method which uses Ro = 42.5V + 45.0 mm for the outer surface and Ri = 40.0V + 40.0 mm for the inner surface as the reference (1R) and expresses the flatness based on how many times the radius of curvature is greater compared to the reference (1R). Here, V indicates a numerical value showing the diagonal effective diameter in inch. It has been known that when the radius of curvature of the outer surface is 10R, the outer surface appears substantially flat. If the color picture tube is of the 36V type, the radius of curvature equivalent to 10R is 15750 mm. Further, when the radius of curvature of the outer diameter is 20R, the outer surface appears substantially perfectly flat. In this case, if the color picture tube is of the 36V type, the radius of curvature equivalent to 20R is 31500 mm. The above-mentioned panel outer surface substantially corresponds to these radii of curvature.
In the above-mentioned panel, the inner surface has the larger curvature than the outer surface. In general, the curved surface of the shadow mask becomes a curved surface substantially equal to the inner surface of the panel. The dimension q which is the distance between the shadow mask and the inner surface of the panel is expressed by an equation q = L × Pm/3s. Here, L is the distance from the deflection center to the shadow mask, Pm is the horizontal pitch of the mask and s is the effective beam distance on the deflection center. As can be understood from this equation, by decreasing the dimension s, the dimension q can be increased. That is, by decreasing the dimension s in the periphery of the screen, the dimension q can be increased in the periphery of the screen so that the curvature of the shadow mask can be increased. Fig. 4 shows a conventional example which adopts this principle. In Fig. 4, numeral 911 indicates an electron beam which scans the center of the screen and numeral 912 indicates an electron beam which scans the periphery of the screen. Respective parameters q, L, s have their values expressed by q0, L0, s0 at the center of the screen and by q1, L1, s1 at the periphery of the screen. In Fig. 4, using two electromagnetic quadruple lenses, the dimension s1 in the periphery of the screen is made smaller than the value s0 at the center of the screen so that the dimension q in the periphery of the screen is increased whereby the curvature is given to the shadow mask. The problem that this method has is that, in the deflection region of electron beams including the deflection center, the actual dimension s is largely changed so that the control of the convergence and the purity on the screen becomes difficult. That is, both of the convergence and the purity are largely changed depending on the dimension s in the vicinity of the deflection center.
Fig. 5 shows the present invention. Respective symbols are identical with symbols in Fig. 4. In the present invention, the first electromagnetic quadruple lens 14 and the second electromagnetic quadruple lens 15 are arranged at a side closer to a cathode of the electron gun than the horizontal deflection coil of the deflection yoke 10. Due to such a constitution, when the electron beams advance into the deflection region of electron beams including the deflection center, three electron beams establish an approximately parallel relationship relative to the tube axis of the cathode ray tube. Since three electron beams can be made substantially parallel to the tube axis in a sensitive region called the deflection region, the control of the convergence and the purity can be performed easily. Fig. 6 and Fig. 7 are schematic views showing the surrounding of the deflection yoke 10 of the present invention. Fig. 6 shows a case in which electron beams are not deflected. No electric current is supplied to a pair of electromagnetic quadruple coils 14, 15 so that the electron beams advance linearly. Fig. 7 shows a case in which electron beams are deflected. An electric current proportional to the deflection current is supplied to the first electromagnetic quadruple coils 14 and the second electromagnetic quadruple coils 15. Fig. 8 is a detailed view of a portion where the electromagnetic quadruple coils 14, 15 are mounted. In this embodiment, the electromagnetic quadruple coils 14, 15 are mounted in the vicinity of a shield cup of the electron gun 9. The electromagnetic quadruple coils 14,15 may preferably be mounted between the rear end of the horizontal deflection coil 101 and the main lens of the electron gun 9. Since the electromagnetic quadruple lenses 14, 15 change the dimension s, by arranging the electromagnetic quadruple lenses 14,15 at a position which three electron beams reach after passing the main lens of the electron gun 9, the influence given to focusing by the electromagnetic quadruple lenses 14, 15 can be reduced. Fig. 9 is a cross-sectional view of a shield cup 50 of this embodiment. Numeral 51, 52 indicate pole pieces for forming the electromagnetic quadruple lens. Fig. 10 and Fig. 11 are operational views. In Fig. 10, in the vicinity of the cross section A-A of Fig. 9, the coils forming the first quadruple lens 14 are mounted and they are operated so as to decrease the dimension s of the electron beams. In Fig. 11, in the vicinity of the cross section B-B of Fig. 9, the coils forming the second quadruple lens 15 are mounted and they are operated so as to make both side electron beams approximately parallel to the tube axis of the cathode ray tube. Pole pieces 51, 52 are not always necessary. In this case, it is not always necessary to position the coils forming the quadruple lens 14, 15 in the vicinity of the shield cup 50. By integrating the coils forming the quadruple lens 14, 15 with the deflection yoke 10, the adjustment can be performed easily. Further, the coils of the electromagnetic quadruple lens 14, 15 may be integrally formed with the magnet assembly 12. Further, the coils forming the first electromagnetic quadruple lens 14 may be integrated with the magnet assembly 12 while the coils forming the second electromagnetic quadruple lens 15 may be integrated with the deflection yoke 10.
Fig. 12 and Fig. 13 show the second embodiment of the present invention. Contrary to the first embodiment, this embodiment increases the dimension s by supplying an electric current to the coils of the electromagnetic quadruple lens in the vicinity of the center of the screen. In this case, an electric current which generates a magnetic field for increasing the dimension s is supplied to the coils of the first quadruple lens 14 and an electric current which generates a magnetic field for making electron beams parallel to the tube axis of the cathode ray tube is supplied to the coils of the second quadruple lens 15. Then, as shown in Fig. 13, when the electron beams are deflected toward the periphery of the screen, for example, the diagonal ends of the screen, an electric current is not supplied to the coils forming the electromagnetic quadruple lens so that the dimension s is held unchanged. In this case, since the distance q between the shadow mask 5 and the panel inner surface is made small at the center so that the curvature of the shadow mask 5 can be increased. Such a constitution is advantageous in a case which employs the electron gun of a type with the small dimension s. Further, in this constitution, since the dimension q at the periphery of the screen is not increased extremely, it brings about an advantageous effect that failures such as a landing error caused by earth magnetism at the periphery of the screen can be reduced. In this second embodiment, since there exists no change of the dimension s in the periphery of the screen where the control of the convergence and the purity is difficult, the second electromagnetic quadruple lens 15 may be arranged in the deflection magnetic field.
Fig. 14 and Fig. 15 show the third embodiment of the present invention. In this embodiment, at the center of the screen, an electric current which effectively increases the dimension s is supplied to the coils forming the electromagnetic quadruple lens 14, 15 and, at the periphery of the screen, for example, at the diagonal end of the screen, an electric current which effectively decreases the dimension s is supplied to the coils forming the electromagnetic quadruple lens 14, 15. An advantage of this embodiment lies in that at the center of the screen and at the periphery of the screen, without extremely changing the magnitude of the dimension s, it becomes possible to give a large curvature to the shadow mask 5. In this third embodiment, since the change of the dimension s can be made small in the periphery of the screen where the control of the convergence and the purity is difficult, the second electromagnetic quadruple lens 15 may be arranged in the deflection magnetic field.
Fig. 16 shows an example of an electron gun employed in the present invention. Fig. 16 is a longitudinal cross-sectional view of the electron gun. In Fig. 16, numeral 40 indicates cathodes and three cathodes are arranged in a direction perpendicular to this paper surface at an interval of 5.5 mm. A center electron beam and two side electron beams are irradiated from three cathodes 40. Numeral 41 indicates control electrodes G1 and numeral 42 indicates an acceleration electrode G2. A front-stage lens is constituted by electrodes 43, 44 and 45. A static focusing voltage Vfs is applied to the electrodes 43 and 45 while a voltage identical to a voltage applied to the acceleration electrode 42 is applied to the electrode 44. A so-called UPF lens is constituted by these three electrodes. Although all electrodes 46, 47, 48 respectively constitute focusing electrodes, they are divided to form a lens having dynamic characteristics. A dynamic focusing voltage which elevates a voltage corresponding to a deflection angle is applied to the electrode 46 and the electrode 48, while a static focusing voltage is applied to the electrode 47. An aperture formed in a portion 451 of the electrode 45 is laterally elongated while an aperture formed in a portion 461 of the electrode 46 is longitudinally elongated. Due to such a constitution, an electrostatic quadruple lens is formed together with an application of a dynamic voltage. Numeral 462 indicates a horizontal-plate-like electrode and numeral 472 indicates a vertical-plate-like electrode. Another electrostatic quadruple lens is formed of these two electrodes. Longitudinally elongated apertures are respectively formed in portions 471, 481 of the electrodes 47, 48. Due to these elongated apertures, the lens intensity is changed along with the application of the dynamic voltage and a lens which elongates the electron beams longitudinally is formed. An anode voltage which is a maximum voltage is applied to an anode electrode 49 and a main lens is formed between the electrode 48 and the electrode 49. The lens intensity of this main lens is decreased along with the elevation of the dynamic voltage. Numeral 482 indicates a plate-like electrode having a longitudinally elongated aperture which is disposed in the inside of the focusing electrode 48 and numeral 491 indicates a plate-like electrode having a longitudinally elongated aperture which is disposed in the inside of the anode electrode 49. Fig. 8 is a detailed view of the main lens portion. The inner electrodes 482, 491 respectively have three longitudinally elongated apertures, apertures may be formed only in the central portions of the inner electrodes 482, 492. When the phosphor screen is flat, although the focusing is deteriorated particularly at the periphery of the phosphor screen, the deterioration of the focusing can be reduced with the use of the dynamic focusing. Further, with the use of the large lens electron gun described in the present embodiment, the deterioration of focusing at the large current can be reduced. Pole pieces 51, 52 for the electromagnetic quadruple lens are mounted on a shield cup 50.
The explanation has been made with respect to the cathode ray tube having the phosphor screen of stripe type heretofore, the present invention is also applicable to a cathode ray tube which has a phosphor screen of dot type, a shadow mask having circular apertures and an electron gun in an inline array. Such a cathode ray tube is used as a high definition display tube whose dot pitch on a phosphor screen is small. In this case, the apertures formed in the shadow mask are arranged as shown in Fig. 18. In the high definition tube, as shown in Fig. 18, the horizontal pitch Ph on the shadow mask is set to not more than 0.41 mm at the center of the screen. In such a case, the shadow mask aperture has a diameter of approximately  0.11 mm. Considering the relationship with the aperture diameter, the plate thickness of the shadow mask which has a large influence on the shadow mask strength may be of the thin thickness of approximately 0.14 mm in view of etching. Accordingly, unless the sufficient curvature is given to the shadow mask, it becomes difficult to ensure the shadow mask strength. The present invention is particularly advantageous in such a high definition display tube.

Claims

A color picture tube comprising a panel (1) having a phosphor screen (4) formed on an inner surface thereof, a neck (2) having an electron gun (9) in the inside thereof and a funnel (3) connecting said neck and said panel, wherein
a deflection yoke (10) having a horizontal deflection coil (101) and a vertical deflection coil (103) for scanning electron beams is mounted in the vicinity of a connecting portion between said neck and said funnel,
said electron gun includes three cathodes (40) arranged in an inline array to generate a center electron beam and two side electron beams and a plurality of electrodes (46, 47, 48) for focusing said electron beams and a shield cup (50),
an equivalent radius of curvature Rd (mm) in the diagonal direction of an outer surface of said panel has a relationship Rd (mm) ≥ 10R (mm) when the numerical value which expresses the effective diagonal diameter in inch is set as V, R is expressed in mm and R = 42.4V + 45.0 is set, and
said color picture tube includes, with respect to the deflection angle of said electron beams, a first electromagnetic quadruple lens (14) having a function of moving said side electron beams toward or away from said center electron beam and a second electromagnetic quadruple lens (15) having a function which acts in the direction to make said two side electron beams become parallel to said center electron beam, wherein said first electromagnetic quadruple lens and said second electromagnetic quadruple lens are arranged at a position closer to a cathode side of said electron gun than said horizontal deflection coil of said deflection yoke.
A color picture tube according to claim 1, wherein along with the increase of the deflection angle, said first electromagnetic quadruple lens (14) has a function of directing said two side electron beams in the direction toward said center electron beam and said second electromagnetic quadruple lens (15) has a function in the direction which is capable of making said two side electron beams become parallel to said center electron beam.
A color picture tube according to claim 2, wherein when said electron beams scan the center of a screen, the intensity of said first electromagnetic quadruple lens (14) and said second electromagnetic quadruple lens (15) is set to zero.
A color picture tube according to claim 1, wherein when said deflection angle is zero, said first electromagnetic quadruple lens (14) has the function of moving said two side electron beams away from said center electron beam and said second electromagnetic quadruple lens (15) has the function in a direction to make said two side electron beams become parallel to said center electron beam, and along with the increase of said deflection angle, the function of said first electromagnetic quadruple lens to move said two side electron beams away from said center electron beam is weakened and said second electromagnetic quadruple lens has the function in a direction to make said two side electron beams parallel to said center electron beam.
A color picture tube according to claim 4, wherein when said electron beams scan diagonal ends of said screen, the intensity of said first electromagnetic quadruple lens (14) and said second electromagnetic quadruple lens (15) is set to approximately zero.
A color picture tube according to claim 4, wherein when the electron beams scan diagonal ends of said screen, said first electromagnetic quadruple lens (14) has the function of directing said two side electron beams toward said center electron beam and said second electromagnetic quadruple lens (15) has the function in a direction to make said two side electron beams become parallel to the center electron beam.
A color picture tube according to claim 1, wherein the relationship between said Rd and said R is set to Rd (mm) ≥ 20R (mm).
A color picture tube according to claim 1, wherein a magnet assembly (11) for adjusting the convergence or the purity is mounted on said neck (2) and coils (14) which form said first electromagnetic quadruple lens and coils (15) which form said second electromagnetic quadruple lens are arranged between said horizontal deflection coil (101) of said deflection yoke and said magnet assembly (11).
A color picture tube comprising a panel (1) having a phosphor screen (4) formed on an inner surface thereof, a neck (2) having an electron gun (9) in the inside thereof and a funnel (3) connecting said neck and said panel, wherein
a deflection yoke (10) having a horizontal deflection coil (101) and a vertical deflection coil (103) for scanning electron beams is mounted in the vicinity of a connecting portion between said neck and said funnel,
said electron gun includes three cathodes (40) arranged in an inline array to generate a center electron beam and two side electron beams and a plurality of electrodes (46, 47, 48) for focusing said electron beams and a shield cup (50),
an equivalent radius of curvature Rd (mm) in the diagonal direction of an outer surface of said panel has a relationship Rd (mm) ≥ 10R (mm) when the numerical value which expresses the effective diagonal diameter in inch is set as V, R is expressed in mm and R = 42.4V + 45.0 is set, and
the color picture tube includes a first electromagnetic quadruple lens (14) having a function of moving said two side electron beams away from said center electron beam and a second electromagnetic quadruple lens (15) having a function which acts in the direction to make said two side electron beams become parallel to said center electron beam when said deflection angle is set to zero, and along with the increase of said deflection angle, the function of said first electromagnetic quadruple lens to move said two side electron beams away from said center electron beam is weakened and said second electromagnetic quadruple lens has the function in a direction to make said two side electron beams become parallel to said center electron beam.
A color picture tube according to claim 9, wherein when said electron beams scan diagonal ends of the screen, the intensity of said first electromagnetic quadruple lens (14) and said second electromagnetic quadruple lens (15) is set to approximately zero.
A color picture tube according to claim 9, wherein when said electron beams scan diagonal ends of the screen, the intensity of said first electromagnetic quadruple lens (14) has the function of directing said two side electron beams toward said center electron beam and said second electromagnetic quadruple lens (15) has the function in a direction to make said two side electron beams become parallel to said center electron beam.
A color picture tube according to claim 9, wherein said first electromagnetic quadruple lens (14) is arranged at a position closer to a cathode side of said electron gun (9) than said horizontal deflection coil (101) of said deflection yoke (10).
A color picture tube according to claim 9, wherein the relationship between said Rd and said R is set to Rd (mm) ≥ 20R (mm).