reference will now be made in detail to the preferred embodiments of the present invention , examples of which are illustrated in the accompanying drawings . the electron gun in a color cathode ray tube of the present invention basically includes a plurality of cathodes for emission of electron beams , a control electrode for controlling amounts of emission of the electron beams , an acceleration electrode for accelerating the electron beams , a pre - focusing electrode for pre - focusing the electron beams , and an anode and a focusing electrode for forming a main focusing electrostatic lens for focusing the electron beams . particularly , in the first and second embodiments of the present invention , the focusing electrode is divided into two . that is , the focusing electrode consists of a first focusing electrode and a second focusing electrode for formation of a dynamic quardrupole lens by a voltage difference to the first focusing electrode . a system of the electron gun of the present invention has the same system with the related art electron from the cathodes up to the first focusing electrode . the electron gun of the present invention is characterized in the second focusing electrode and the anode which form the main focusing electrostatic lens according to a voltage difference . the present invention has a system identical to the related art from the cathodes to the first focusing electrode , which will be omitted , and the second focusing electrode and the anode only will be explained . fig5 illustrates a half section of an electron gun in a color cathode ray tube in accordance with a first preferred embodiment of the present invention . referring to fig5 the electron gun in a color cathode ray tube in accordance with a first preferred embodiment of the present invention includes a first focusing electrode 12 , a second focusing electrode 13 for forming a dynamic quardrupole lens according to a voltage difference to the first focusing electrode 12 , and an anode 14 for having a positive voltage applied thereto . the second focusing electrode 13 includes a first cup formed electrode 131 having an opened one end to the screen , and the other end with three electron beam pass through holes 13 la formed therein , a second cup formed electrode 132 having one end fixed to the other end of the first cup formed electrode with three electron beam pass through holes 132 a formed therein and the other end opened to the cathodes , a first plate electrode 133 fixed to the one end of the first cup formed electrode 131 having single electron beam pass through hole 133 a of a horizontally elongated track form for passing of the three electron beams formed therein , and a fifth plate electrode 134 having one side fixed to the other end of the second cup formed electrode 132 and three electron beam pass through holes 134 a . the anode 14 includes a third cup formed electrode 141 having one end opened to the cathodes , and the other end with three electron beam pass through holes 141 a formed therein , a fourth cup formed electrode 142 having one end fixed to the other end of the third cup formed electrode 141 with three electron beam pass through holes 142 a formed therein , and the other end opened to the screen , and a second plate electrode 143 fixed to the one end of the third cup formed electrode 141 having single electron beam pass through hole 143 a of a horizontally elongated track form for passing of the three electron beams . an abut portion of the first and second cup formed electrodes 131 and 132 and an abut portion of the third and fourth cup formed electrodes 141 and 142 act as the electrostatic field control electrodes 132 and 142 in the electron gun of the related art color cathode ray tube shown in fig3 and 4 , respectively . an outer part of an inner circumference of the first and second plate electrodes 133 and 143 are smoothly tapered by pressing enough to prevent occurrence of discharge between the second focusing electrode 13 and the anode 14 . in the first embodiment electron gun of the present invention , there is a horizontal electrode 134 b fitted to upper side and lower side of each of the electron beam pass through holes 134 a in the other side of the fifth plate electrode 134 , to form a dynamic quardrupole lens between the first and second focusing electrodes 12 and 13 by a voltage difference between the first focusing electrode 2 and the second focusing electrode 13 and the horizontal electrodes 134 b . and , there are flanges 133 c , 143 c and 134 c on upper side and lower side of the first , second and fifth plate electrodes 133 , 143 , and 134 buried in and fixed to bead glass 17 . however , particularly , the flanges 133 c and 143 c can receive a possible vertical pressures which may be formed in burying the flanges 133 c and 143 c into the bead glass 17 as they are , to deform the first and second plate electrodes 133 and 143 . moreover , there is a possibility of discharge occurrence as areas of facing surfaces of the plate electrodes 133 and 143 are increased by areas of the flanges 133 c and 143 c . those drawbacks of the first embodiment of the present invention can be overcome by the second embodiment of the present invention , which will be explained hereafter . fig6 illustrates a half section of an electron gun in a color cathode ray tube in accordance with a second preferred embodiment of the present invention . referring to fig6 alike the first embodiment of the present invention , the electron gun in a color cathode ray tube in accordance with a second preferred embodiment of the present invention includes a second focusing electrode 13 , and an anode 14 . the second focusing electrode 13 includes a first cup formed electrode 131 having one end opened to the screen , and the other end with three electron beam pass through holes 131 a , a third plate electrode 135 having one side fixed to the other end of the first cup formed electrode 131 and three electron beam pass through holes 135 a , a second cup formed electrode 132 having one opened end fixed to the other side of the third plate electrode 135 and the other end with three electron beam pass through holes 132 a , and a first plate electrode 133 fixed to the one end of the first cup formed electrode 131 having single electron pass through hole 133 a of a horizontally elongated track form for passing of the three electron beams . the anode 14 includes a third cup formed electrode 141 having one end opened to the cathodes , and the other end with three electron beam pass through holes 141 a , a fourth plate electrode 144 having one side fixed to the other end of the third cup formed electrode 141 and three electron beam pass through holes 144 a formed therein , a fourth cup formed electrode 142 having one opened end fixed to the other side of the fourth plate electrode 144 and the other end with single electron beam pass through hole 142 a , and a second plate electrode 143 fixed to one end of the third cup formed electrode 141 and single electron beam pass through hole 143 a of a horizontally elongated track form for passing of the three electron beams . in this instance , the other end of the first cup formed electrode 131 , the third plate electrode 135 , and the other end of the third cup formed electrode 141 act the same as the electrostatic field control electrodes 132 and 142 in the electron gun of the related art color cathode ray tube shown in fig2 and 3 . and , there is a horizontal electrode on the other side of upper side and lower side of each of the electron beam pass through holes 132 a , to form a dynamic quardrupole lens between the first and second focusing electrodes 12 and 13 by a to voltage difference between the first focusing electrode 12 and the second focusing electrode 13 and the horizontal electrodes 132 b . there are flanges 135 c and 144 c on upper side and lower side of the third and fourth plate electrodes 135 and 144 buried in and fixed to bead glass 17 . alike the first embodiment of the present invention , though the second embodiment of the present invention is provided with the first and second plate electrodes 133 and 143 of horizontally elongated track forms for passing of the three electron beams in common , the second embodiment of the present invention is provided with flanges on upper side and lower side of the first and second plate electrodes 133 and 143 . therefore , even when the flanges 135 c and 144 c are buried in the bead glass 17 , the first and second plate electrodes 133 and 143 receive no vertical pressure from the bead glass , resulting in no deformation . eventually , the main focusing lens formed between the second focusing electrode 13 and the anode 14 is very accurate , to permit an improvement in the focusing on the screen . and , as there are no flanges provided to the first and second plate electrodes 133 and 143 in the second embodiment of the present invention , the facing areas between the first and second plate electrodes 133 and 143 can be minimized , leading to a reduction of a possibility of discharge occurrence . moreover , as shown in fig7 c , the smooth taper at an outer side of the inside circumference of the first and second plate electrodes 133 and 143 done by separate pressing process can prevent occurrence of discharge between the second focusing electrode 13 and the anode 14 , more positively . in the meantime , in the first and second embodiments of the present invention , the first and second plate electrodes 133 and 135 mounted opposite to the second focusing electrode 13 and the anode 14 have a thickness of 0 . 7 ˜ 2 . 0 mm for providing an adequate strength against deformation in fabrication of the electron gun . if the thickness is less than 0 . 7 mm , rims of the first and second plate electrodes 133 and 134 may deform in fabrication of the electron gun , and if the thickness is greater than 2 . 0 mm , a life time of a mold can be shortened in the pressing . in the first and second embodiments of the present invention , the rim part hole diameters of the first and second plate electrodes 133 and 143 can be enlarged to 20 . 5 mm ( h 2 ) in the horizontal direction and to 10 . 5 mm ( v 2 ) in the vertical direction by individual pressing of the first and second plate electrodes 133 and 143 , corresponding to the opposite surfaces of the second focusing electrode 13 and the anode 14 respectively , at first , and fixing the first and third cup formed electrodes 131 and 141 thereto , respectively . table 1 shows a comparison of the rim part hole diameters of the first and second plate electrodes 133 and 143 fixed opposite edges to the anode 14 and the second focusing electrode 13 respectively versus the diameter of the main focusing electrostatic lens . as shown in table 1 , it can be known that the greater the rim part hole diameters of the first and second plate electrodes 133 and 143 , the greater the diameter of the main focusing electrostatic lens , to an extent of 19 % in the horizontal direction and 20 % in the vertical direction . as has been explained , the electron gun in a color cathode ray tube of the present invention has the following advantages . first , the dimensional enlargement of the rim parts which form the main focusing electrostatic lens to the maximum permits enlargement of lens diameters compared to the same to of the related art by 19 % in a horizontal direction and 20 % in a vertical direction . second , the increased thickness of the plate electrode which form the rim part from 0 . 4 mm in the related art to 0 . 7 mm in the present invention permits to prevent deformation of the first and second plate electrodes caused by the vertical pressure from the bead glass in fabrication of the electron gun , that allows to provide an accurate main focusing electrostatic lens . third , the smooth taper at the outer side of the inside circumference of the plate electrode by separate pressing permits to prevent discharge between the second focusing electrode and the anode . it will be apparent to those skilled in the art that various modifications and variations can be made in the electron gun in a color cathode ray tube of the present invention without departing from the spirit or scope of the invention . thus , it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents .