COLOR CATHODE RAY TUBE AND ENVELOPE FOR USE WITH THE COLOR CATHODE RAY TUBE

Abstract: A metal plate (48, 88) is interposed between a panel section (42, 82) and funnel sections (50, 90) of an envelope (40, 80) which is provided with plural neck sections(52, 92). The length of the envelope can be thus made shorter in the direction of the tube axis. The structure of the envelope can be made simpler and its productivity can be enhanced accordingly. Further, it can be made lighter in weight.

Description: The present invention relates to a color cathode ray tube and, more particularly, it relates to the structure of an envelope provided with plural necks and a color cathode ray tube provided with this envelope. The envelope according to the first part of Claim 1 is known from EP-A-0 201 098 which corresponds to JP-A-61-256551 mentioned below. EP-A-0 201 098 also discloses a color cathode ray tube comprising such an envelope, and further comprising : a phosphor screen disposed on the inner surface of the face plate; a shadow mask disposed near the phosphor screen; and a plurality of electron gun assemblies, each of the electron gun assemblies being arranged in the neck sections, respectively. The conventional color cathode ray tube provided with plural necks is shown in Fig. 1. As disclosed in Japanese Patent Disclosure No. Sho 61-256551, this color cathode ray tube 1 includes envelope 11 comprising panel section 2 provided with substantially rectangular face plate 4 and skirt 6 extending from the circumferential rim of face plate 4, funnel section 8 connected to panel section 2, and plural neck sections 10 continuous from funnel section 8. The inside of cathode ray tube 1 is kept vacuum by panel, funnel and neck sections 2, 8 and 10. Electron gun assembly 12 for shooting three electron beams is housed in each of plural neck sections 10. Funnel and neck sections 8 and 10 are provided, on the outer surface thereof, with deflection means 14 for generating magnetic field to deflect the electron beams in horizontal and vertical directions. Phosphor screen 16 is formed on the inner surface of face plate 4 at panel section 2. Substantially rectangular shadow mask 18 is arranged inside the tube, facing phosphor screen 16 with a certain interval interposed between them. Shadow mask 18 is made by a thin metal plate and provided with a plurality of slit apertures 20. Frame 22 is attached to the circumferential rim of shadow mask 18. Three electron beams shot from each of electron guns 12 are deflected by deflection means 14. Fig. 1 shows only those areas where the three electron beams are deflected. The electron beams thus deflected are converged on phosphor screen 16. The electron beams thus converged are introduced onto phosphor screen 16 to emit three colors of red, green and blue. Phosphor screen 16 which is scanned by the electron beams shot from electron guns 12 is sectioned to correspond to each of electron guns 12. In the case of the envelope having the above-described structure to be used as the color cathode ray tube, the distance extending from the face plate to the neck can be made shorter as compared with another envelope, same in size, but having only one neck section. This is because that area of the phosphor screen which is scanned by the electron gun housed in the neck section can be made smaller and the distance between the electron gun and the phosphor screen can be thus made shorter. As the envelope is made larger in size, the effect of making this distance shorter can be enhanced further and further. In the case where the panel, funnel and neck sections are all made of glass, however, they cannot be made so sharply-curved as to make the distance curved as to make the distance between the electron gun and the phosphor screen shorter because the material of which they are made is glass. The envelope all of which is made of glass has therefore a limitation in making the distance shorter. The envelope having the above-described arrangement to be used as the color cathode ray tube has an extremely more complicated shape as compared with the other envelopes which are intended for the common color cathode ray tubes. This envelope is made of glass. It is therefore quite difficult to process glass to the complicated shape of this envelope. This makes it difficult to put this envelope on mass production line. This envelope is made to resist atmospheric pressure so as to keep its inside vacuum. When it is large in size, quite large force is added to it because of atmospheric pressure. It is therefore needed that the thickness of the glass funnel section is substantially same as that of the glass panel section. However, a distortion of the glass neck section by the pressure is relatively small. It is therefore unnecessary to make the thickness of the glass neck section large but the glass neck section may be about 1mm thick, for example. The thickness of glass thus changes sharply from the funnel to the neck section and this changes heat capacity sharply at this portion shifting from the funnel to the neck section. The envelope to which heat is applied at plural processes in the manufacturing course thus increases its thermal distortion. The envelope is made likely to be broken because of its thermal distortion, and this makes it difficult to put the envelope on mass production line. Further, the thickness of the funnel section is made substantially same as that of the panel section When the envelope is large in size, therefore, it becomes quite heavy. When it is heavy, it increases the weight of the color cathode ray tube for which it is intended. The object of the present invention is to provide an envelope having plural neck sections and a color cathode ray tube which uses this envelope, said envelope enabling the depth to be made shorter, and said color cathode ray tube enabling the distance between the electron gun and the phosphor screen to be made shorter, its weight to be made lighter and its mass production to be made easier. According to the present invention as defined in Claim 1, there can be provided a vacuum envelope for a cathode ray tube comprising a plurality of funnel sections each having a front and a rear side, a plurality of neck sections, one neck section being arranged on each rear side of the funnel sections, a panel section including a face plate having an inner surface, and a skirt extending from a peripheral edge of the face plate, and a metal connecting means for connecting each front side of the funnel sections to the skirt of the panel section, the metal connecting means having a main surface substantially parallel to the inner surface of the face plate, an outer face, and a plurality of openings on the main surface corresponding to the front sides of the funnel sections. Dependent Claims 2 to 9 concern particular embodiments of the invention. According to the present invention, the envelope is provided with a metal connecting means (a rear plate made of metal). The distance between the phosphor screen and the electron gun in the envelope can be thus made shorter. In addition, the envelope can be made lighter in weight. Further, the envelope can be made more suitable for mass production. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a sectional view showing the conventional color cathode ray tube provided with plural neck sections; Fig. 2 is a perspective view showing a first example of an envelope according to the present invention; Fig. 3 is a sectional view taken along a line A - A in Fig. 2 to show the envelope in Fig. 2; Fig. 4 is an enlarged sectional view showing a portion of the envelope in Fig. 3; Fig. 5 is a sectional view showing a variation of the first embodiment; Fig. 6 is a sectional view showing a color cathode ray tube in which the first example of the envelope is employed; Fig. 7 is an enlarged sectional view showing a portion of the tube in Fig. 6; Fig. 8 is a sectional view showing an envelope of a second embodiment according to the present invention; Fig. 9 is an enlarged sectional view showing a portion of the envelope in Fig. 8; Fig. 10A is an enlarged sectional view showing a portion I in Fig. 9; Fig. 10B is an enlarged sectional view showing a portion II in Fig. 9; Fig. 11 is a perspective view showing a first variation of the first insertion members; Fig. 12 is a sectional view showing the first variation of the first insertion members; Fig. 13 is a perspective view showing a second variation of the first insertion members; Fig. 14 is a sectional view showing the second variation of the first insertion members; Fig. 15 is a perspective view showing a third variation of the first insertion members; Fig. 16 is a sectional view showing the third variation of the first insertion members; Fig. 17 is a sectional view showing a color cathode ray tube in which the envelope of the second embodiment is employed; Fig. 18 is an enlarged sectional view showing a portion of the tube in Fig. 17; Fig. 19A is an enlarged sectional view showing a portion III in Fig. 18; and Fig. 19B is an enlarged sectional view showing a portion IV in Fig. 18. Some embodiments of the present invention will be described with reference to the accompanying drawings. A first example of the envelope according to the present invention and having plural necks is shown in Figs. 2 and 3. This envelope is used for the color cathode ray tube. Envelope 40 comprises panel section 42 provided with substantially rectangular face plate 44 and skirt 46 extending from the peripheral edge of face plate 44, rear plate 48 (metal connecting means) arranged substantially parallel to face plate 44 and bonded to skirt 46 of panel section 42, plural funnel sections 50 bonded to rear plate 48, and plural neck sections 52 continuous from funnel sections 50. The inside of envelope 40 is kept vacuum by panel section 42, rear plate 48, funnel sections 50 and neck sections 52. Each of plural neck sections 52 is provided with plural stem pins 54. Plural reinforcing plates 56 are attached to the outer face of rear plate 50 to enable rear plate 50 to resist atmospheric pressure. Envelope 40, a portion of which is also shown in Fig. 4, is used for the color cathode ray tube of 20 inches (508,0mm), for example. A phosphor screen, 304.8mm long and 406.4mm broad, can be formed on the inner surface of face plate 44 in envelope 40. The length of skirt 46 is 85mm. Rear plate 48 is made of sealing alloy which includes 50% of nickel, and it is formed like a plate, 2mm thick. It is perpendicular to the tube axis, it is shaped to match the outer circumference of skirt 46, and it is provided with plural openings 58 each communicated with its corresponding one of funnel sections 50. Skirt 46 and rear plate 48 are bonded to each other with frit glass (for example crystalline lead borate glass) 49 interposed between them. An oxidation layer is formed on that surface area of rear plate 48 to which frit glass 49 is bonded so as to enhance the bonding strength of frit glass 49. Thermal expansion coefficient of the alloy of which rear plate 48 is made is 99.0 (10⁻⁷/°C). Twelve funnel sections 50 which are separated from adjacent ones by a certain interval are bonded to rear plate 48. Each of twelve openings of rear plate 48 to which each of the front sides of funnel sections 50 is bonded is shaped like a substantially rectangle, 30mm wide and 25mm long. Neck section 52 having an outer diameter of 22.5mm is continuous from each of the rear sides of funnel sections 50. Four neck sections 52 are located in the longitudinal direction of the panel while three neck sections 52 in the lateral direction thereof, totaling to twelve neck sections. Rear plate 48 and each of funnel sections 50 are bonded to each other with frit glass 51 interposed between them. Thermal expansion coefficient of glass, of which funnel and neck sections 50 and 52 are made, is 100.0 (10⁻⁷/°C). Eight stem pins 54 are projected outside from the end of each of neck sections 52. Each of plural reinforcing plates 56 attached to the outer face of rear plate 48 is made by an L-shaped mild steel. Reinforcing plate 56 is 2.0mm thick and 20mm high. These reinforcing plates 56 are spot-welded to rear plate 48. The envelope having the above-described arrangement enables the skirt and the funnel sections to be surely bonded to the rear plate by the frit glass. The thermal expansion coefficient of the alloy, of which the rear plate is made, is substantially equal to that of the glass of which the funnel sections are made, thereby preventing distortion from being caused by heat. The rear plate made of metal is interposed between the panel and the funnel sections in the case of this envelope, thereby making it unnecessary to use glass to make the panel continuous to the funnel sections. Although glass could not be sharply curved because of properties characteristic of glass, the envelope can be shaped to have sharply-curved-portions when metal is used. The envelope can be thus made shorter in the direction of tube axis. Therefore, the distance between the face plate and the neck sections (or depth of the envelope) can be made shorter, as compared with the conventional envelope which is all made of glass. The thickness of glass of that portion which shifts from the panel to the funnel sections is conventionally about the same as that of the panel and quite large. However, that portion which shifts from the panel to the funnel sections is formed by metal instead of glass. The envelope can be thus made lighter in weight. Further, the funnel sections have no thick portion. This can reduce the thermal distortion of the envelope caused in the manufacturing course. Furthermore, the panel, rear plate, funnel and neck sections can be made independently of the others. This can make the manufacturing cost lower and make the envelope more suitable for mass production. The rear plate of this embodiment is made of the above-mentioned sealing alloy which contains 50% of nickel. In addition, it may be made of sealing alloy which contains 52% of nickel and 6% of chrome. It is formed in a plane plate, but it may be shaped to match the curvature of the face plate. The reinforcing plate which is spot-welded to the outer face of the rear plate is L-shaped, but when one of other welding manners such as arc and plasma weldings is employed, it is not needed that the reinforcing plates are L-shaped. When the rear plate is made 5mm thick, for example, the envelope can resist atmospheric pressure, thereby making it unnecessary to use the reinforcing plates. Fig. 5 shows a variation of the envelope in which the rear plate is different in shape from the one used in the first embodiment of the present invention. The other components of the envelope are same except the shape of this rear plate. Therefore, description on these same components will be omitted. Step 59 is formed between this peripheral rim portion of rear plate 58 which is bonded to skirt 46 and that portion thereof which is bonded to funnel sections 50. This step 59 is intended to further separate funnel sections 50 from face plate 44. When rear plate 58 is provided with this step 59, it can be made stronger enough to resist atmospheric pressure, as compared with the case where it is formed like a plate. This variation can achieve same merits as those attained by the first example of the envelope. This first example of the envelope and its variation can be applied to various kinds of the cathode ray tubes. A color cathode ray tube in which the above-described envelope is employed is shown in Figs. 6 and 7. Envelope 40 for this color cathode ray tube 60 comprises panel section 42 provided with substantially rectangular face plate 44 and skirt 46 extending from the peripheral edge of face plate 44, rear plate 48 arranged substantially parallel to face plate 44 and bonded to skirt 46 of panel section 42, a plurality of funnel sections 50 bonded to rear plate 48, and a plurality of neck sections 52 each continuous from its corresponding one of funnel sections 50. The inside of envelope 40 is kept vacuum by panel section 42, rear plate 48, funnel and neck sections 50 and 52. Each of plural neck sections 52 is provided with plural stem pins 54. Plural reinforcing plates 56 are attached to the outer face of rear plate 48. Twelve electron guns 62 are housed in plural neck sections 52, respectively, in the case of this color cathode ray tube 60. Stem pins 54 are connected to each of electron guns 62. Phosphor screen 64 is formed on the inner surface of face plate 44. Three electron beams shot from each of electron guns 62 are landed onto phosphor screen 64 to emit three colors of red, green and blue. Shadow mask 66 is located in envelope 40 to face phosphor screen 64 and provided with a plurality of apertures. Mask frame 68 is attached to the circumferential rim of shadow mask 66 and kept supported in panel section 42. In the case of the color cathode ray tube of 20 inches (508,0mm), for example, phosphor screen 64, 304.8mm long and 406.4mm broad, is formed on the inner surface of face plate 44. Skirt 46 is made 85mm long. Rear plate 48 is made of sealing alloy which contains 50% of nickel and it is formed like a plate having a thickness of 2mm. It is perpendicular to the tube axis, it is shaped to match the circumferential contour of skirt 46 and it is provided with a plurality of openings 58 each communicated with its corresponding one of funnel sections 50. Skirt 46 and rear plate 48 are bonded to each other with frit glass (for example crystalline lead borate glass) interposed between them. That surface area of rear plate 48 to which frit glass 49 is bonded has an oxidation layer formed thereon to enhance the bonding strength of frit glass 49. Thermal expansion coefficient of the alloy of which rear plate 48 is made is 99.0 (10⁻⁷/°C). Each of the front sides of funnel sections 50 which is bonded to rear plate 48 is formed in a substantially rectangle having a length of 30mm and a width of 25mm. Each of the rear sides of neck sections 52, which has an outer diameter of 22.5mm, is continuous from its corresponding one of funnel sections 50. Four neck sections 52 are arranged in the longitudinal direction of the panel section while three neck sections 52 in the lateral direction thereof, totaling to twelve neck sections 52. Rear plate 48 and each of funnel sections 50 are bonded to each other with frit glass 51 interposed between them. Thermal expansion coefficient of the glass of which funnel and neck sections 50 and 52 are made is 100.0 (10⁻⁷/°C). Eight stem pins are projected outside from the end of each of neck sections 52. Each of reinforcing plates 56 attached to the outer face of rear plate 48 is made by an L-shaped soft steel plate. Reinforcing plate 56 is made 2.0mm thick and 20mm high. Reinforcing plates 56 are spot-welded to rear plate 48. Color cathode ray tube 60 having the above-described arrangement includes twelve electron guns 62. These electron guns 62 shoot electron beams relative to their respective areas on the phosphor screen. Namely, the phosphor screen is divided into twelve areas, each of which is shot by its corresponding electron gun. The phosphor screen emits three colors of red, green and blue at its respective areas responsive to the electron beams shot by the electron guns. In the case of the above-described color cathode ray tube, the area of the phosphor screen which is scanned by one electron gun is quite smaller, as compared with conventional color cathode ray tubes. The electron beams shot by the electron guns can thus travel a shorter distance to reach the phosphor screen, thereby reducing the possibility of causing the electron beams to wrongly land onto the phosphor screen. As the result, the picture quality of this color cathode ray tube can be kept extremely high. According to the color cathode ray tube of the present invention, the skirt and the funnel sections can be reliably bonded to the rear plate by the frit glass. In addition, the thermal expansion coefficient of the alloy, of which the rear plate is made, is substantially same as that of the glass of which the funnel sections are made. This prevents the envelope from being distorted by heat. In the case of the above-described color cathode ray tube according to the present invention, the rear plate made of metal is arranged between the panel section and the funnel sections. It is not needed therefore that glass is used to form connection between them. Glass could not be made sharply-curved because of the properties characteristic of glass. When metal is employed, however, the envelope can be shaped to have sharply-curved portions. The length of the color cathode ray tube can be thus made shorter in the direction of its tube axis. Therefore, the distance between the face plate and the neck sections (or depth of the color cathode ray tube) can be made shorter, as compared with the conventional envelope which was all made of glass. That portion of glass which shifts from the panel section to the funnel sections was substantially same in thickness as the panel section and quite thick in the case of the conventional envelope. This portion of glass can be replaced by a thin metal plate, thereby making the color cathode ray tube lighter in weight. Further, it is not necessary to make the funnel section thick at any portion, thereby reducing the thermal distortion of the envelope caused in the manufacturing course. Furthermore, the panel section, rear plate, funnel and neck sections can be made independently of the others and then assembled to make the color cathode ray tube. This can make the manufacturing cost lower. In addition, the color cathode ray tube can be made more suitable for mass production. A second example of the envelope according to the present invention is shown in Fig. 8. This envelope 80 is intended for cathode ray tubes. Envelope 80 comprises panel section 82 having substantially rectangular face plate 84 and skirt 86 extending from the peripheral edge of face plate 84, rear plate 88 arranged substantially parallel to face plate 84 and bonded to skirt 86 of panel section 82, a plurality of funnel sections 90 bonded to rear plate 88, and a plurality of neck sections 92 each continuous from its corresponding one of funnel sections 90. The inside of the envelope 80 is kept vacuum by panel section 82, rear plate 88, funnel and neck sections 90 and 92. Each of plural neck sections 92 is provided with plural stem pins 94. Plural reinforcing plates 96 are attached to the outer face of rear plate 88. First thin metal plate 98 which is a first insertion means is interposed between rear plate 88 and each of funnel sections 90. Second thin metal plate 100 which is a second insertion means is interposed between rear plate 88 and skirt 86. This envelope is intended for color cathode ray tubes of 20 inches (508,0mm), for example. A phosphor screen, 304.8mm long and 406.4mm broad, can be formed on the inner surface of face plate 84 in the case of envelope 80. Skirt 86 is made 85mm long. Rear plate 88 is made of mild steel, and it is shaped like a plate having a thickness of 2mm. Thermal expansion coefficient of the mild steel of which rear plate 88 is made is 140 (10⁻⁷/°C). It is perpendicular to the tube axis, it is made to match the circumferential contour of skirt 86, and it is provided with a plurality of openings 99 each communicated with its corresponding one of funnel sections 90. As shown in Figs. 9 and 10B, second thin metal plate 100, 0.3mm thick and 20mm wide, made of 50% nickel alloy and shaped like a hollow disk is interposed between skirt 86 and rear plate 88 and bonded to rear plate 88. Frit glass (for example crystalline lead borate glass) 104 is interposed between second thin metal plate 100 and skirt 86. An oxidation layer is formed on the surface of second thin metal plate 100 to enhance the bonding strength of frit glass 104. Thermal expansion coefficient of the alloy of which second insertion means is made is 99.0 (10⁻⁷/°C). Twelve funnel sections 90 are bonded to rear plate 88 through the insertion members and each of the front sides of rear plate 88 is shaped in a substantially rectangle having a diagonal line of about 40mm. Each of the rear sides of neck sections 92, which has an outer diameter of 22.5mm, is made continuous from its corresponding one of funnel sections 90. As shown in Fig. 10A, first thin metal plate 98, 0.3mm thick and 5mm wide, made of 50% nickel alloy and shaped like a hollow disk is interposed between rear plate 88 and each of funnel sections 90 and bonded to rear plate 88. Frit glass 102 is interposed between first thin metal plate 98 and each of funnel sections 90. Thermal expansion coefficient of the glass of which funnel and neck sections 90 and 92 are made is 100.0 (10⁻⁷/°C). Eight stem pins 94 are projected outside from the end of each of neck sections 92. Four neck sections are arranged in the longitudinal direction of panel section 82 while three neck sections in the lateral direction thereof, totaling to twelve neck sections. Each of reinforcing plates 96 attached to the outer face of rear plate 88 is made by an L-shaped soft steel plate. It is 2.0mm thick and 200mm high and it is spot-welded to rear plate 88. It will be described how the above-mentioned members are bonded to one another. Bonding between the thin metal plates which serve as the first and second insertion means and the funnel sections which are made of glass is attained by frit glass. Frit glass is baked at about 450°C for an hour to enable the metal plates and glass to be bonded to each other. Thermal expansion coefficients of the metal plates and glass thus bonded are 99.0 (10⁻⁷/°C) in the case of the insertion means and 100.0 (10⁻⁷/°C) in the case of the glass of which the funnel sections are made. Almost no distortion is therefore left in both of the metal plates and glass bonded. Seam welding is used to get bonding between metal and metal. Bonding between the rear plate which is made of metal and the thin metal plates which serves as the insertion means is attained by seam welding. Welded portions are separated as remote as possible from bonded portions which are attained by frit glass. This is because these bonded portions are deformed by the heat at the welding process to cause the glass seals to peel off from the bonded portions. According the envelope having the above-described arrangement, the rear plate and the skirt as well as the rear plate and the funnel sections can be reliably bonded to each other by frit glass and thin metal plates. The thermal expansion coefficient of the alloy of which the first and second thin metal plates are made is substantially equal to that of the glass of which the funnel sections are made, thereby preventing the envelope from being distorted by heat. In this embodiment, the same advantage as the first embodiment can be obtained. Moreover, since the first and second insertion means are made of sealing alloy and the rear plate is made of mild steel, the glass, the sealing alloy, the mild steel, the sealing alloy, and the glass can be bonded in order, respectively. Therefore, the expensive sealing alloy can be expended as small as possible. Since the rear plate can be made of mild steel, the envelope can be composed easily. Although seam welding has been used to weld metal to metal, other welding manners such as plasma, laser and ultrasonic weldings. Figs. 11 through 16 show other first insertion means which have various kinds of shapes. A first variation of the first insertion means is shown in Figs. 11 and 12. This first insertion means 106 is made of sealing alloy which contains 50% of nickel. Insertion means 106 includes a substantially cylindrical portion and two disk or flange portions projecting outward and horizontally from both ends of the cylindrical portion. Outer faces of these disk portions are bonded to frit glass 102 and rear plate 88. A second variation of the first insertion means is shown in Figs. 13 and 14. This insertion means 108 is made of sealing alloy which contains 50% of nickel. Insertion means 108 includes a substantially cylindrical portion and two disk or flange portions projecting inward and horizontally from both ends of the cylindrical portion. Outer faces of these disk portions are bonded to frit glass 102 and rear plate 88, respectively. A third variation of the first insertion means is shown in Figs. 15 and 16. This insertion means 110 is made of sealing alloy which contains 50% of nickel. Insertion means 110 includes a substantially cylindrical portion and two disk or flange portions, one of which projects inward and horizontally from one end of the cylindrical portion while the other of which projects outward and horizontally from the other end thereof. The outer face of the inward projecting disk portion is bonded to frit glass 102 while that of the outward projecting disk portion to rear plate 88. When the first through third variations of the first insertion means are employed, the rear plate can be separated remoter from the funnel sections, as compared with the case where metal plate 98 is used. Therefore, portions bonded by frit glass can be protected better from the heat caused at the time when the rear plate is welded to the insertion means. The first and second insertion means have been made of alloy which contains 50% of nickel, but they may be made of other alloy which contains 52% of nickel and 6% of chrome. This rear plate has been made like a plate, but it may be curved to have same curvature as that of the face plate. A color cathode ray tube which uses the above-described envelope is shown in Figs. 17 through 19. Envelope 80 for this color cathode ray tube 120 comprises panel section 82 provided with substantially rectangular face plate 84 and skirt 86 extending from the peripheral edge of face plate 84, rear plate 88 arranged substantially parallel to face plate 84 and bonded to skirt 86 of panel section 82, a plurality of funnel sections 90 bonded to rear plate 88, and a plurality of neck sections 92 each continuous from its corresponding one of funnel sections 90. The inside of envelope 80 is kept vacuum by panel section 82, rear plate 88, funnel and neck sections 90 and 92. Each of plural neck sections 92 is provided with plural stem pins 94. Plural reinforcing plates 96 are attached to the outer face of rear plate 88. First thin metal plate 98 which serves as the first insertion means is interposed between rear plate 88 and each of funnel sections 90 to provide bonding between them. Second thin metal plate 100 which serves as the second insertion means is interposed between rear plate 88 and skirt 86 to provide bonding between them. Electron gun 122 is housed in each of plural neck sections 92 in the case of this color cathode ray tube 120. Stem pins 94 are connected to each of electron guns 122. phosphor screen 124 is formed on the inner surface of face plate 84. Phosphor screen 124 is landed by electron beams shot from each of electron guns 122 to emit three colors of red, green and blue. Shadow mask 126 is located in envelope 80 to face phosphor screen 124. Shadow mask 126 is provided with a plurality of apertures. Mask frame 128 encloses shadow mask 126. Mask frame 128 is kept supported in panel section 82. In the case of the 20-inch (508,0mm) color cathode ray tube, for example, phosphor screen, 304.8mm long and 406.4mm broad, is formed on the inner face of face plate 124. Skirt 86 is made 85mm long. Rear plate 88 is made of mild steel, and it is shaped like a plate having a thickness of 2mm. Thermal expansion coefficient of the mild steel of which rear plate 88 is made is 140 (10⁻⁷/°C). It is perpendicular to the tube axis, it is made to match the circumferential contour of skirt 86, and it is provided with plural openings 98 each communicated with its corresponding one of funnel sections 90. Second thin metal plate 100, 0.3mm thick and 200mm wide, shaped like a hollow disk and made of 50% nickel alloy is interposed between skirt 86 and rear plate 88 and bonded to rear plate 88. Frit glass (for example crystalline lead borate glass) 104 is interposed between second thin metal plate 100 and skirt 86. An oxidation layer is formed on that surface area of second thin metal plate 100 to which frit glass 104 is to be bonded so as to strengthen the bonding ability of frit glass 104. Thermal expansion coefficient of the alloy of which second thin metal plate 100 is made is 99.0 (10⁻⁷/°C). Each of the front sides of funnel sections 90 which is to be bonded to rear plate 88 through the insertion means is formed like a substantially rectangle having a diagonal line of about 40mm. Each of the rear sides of neck sections 92 which has an outer diameter of 22.5mm is made continuous from its corresponding one of funnel sections 90. First thin metal plate 98, 0.3mm thick and 5mm wide, shaped like a hollow disk and made of alloy which contains 50% of nickel is interposed between rear plate 88 and each of funnel sections and bonded to rear plate 88. Frit glass 102 is interposed between first thin metal plate 98 and each of funnel sections 90. An oxidation layer is formed on that surface area of first thin metal plate 98 to which frit glass 102 is to be bonded so as to strengthen the bonding ability of frit glass 102. Thermal expansion coefficient of the glass of which funnel and neck sections 90 and 92 are made is 100.0 (10⁻⁷/°C). Eight stem pins 94 are projected outside from the end of each of neck sections 92. Each of reinforcing plates 96 is made by an L-shaped soft steel plate. It is 2.0mm thick and 20mm high and spot-welded to rear plate 88. The color cathode ray tube having the above-described arrangement includes twelve electron guns 122. Each of these electron guns 122 shoots electron beams to emit three colors of red, green and blue at its corresponding area on the phosphor screen. More specifically, the phosphor screen is divided into twelve areas to correspond to the twelve electron guns. The phosphor screen emits three colors of red, green and blue responsive to the electron beams shot from each of the electron guns. In the case of the above-described color cathode ray tube, that area of the phosphor screen which is scanned by one electron gun is quite smaller, as compared with the conventional color cathode ray tube. Therefore, the electron beams shot from each of the electron guns can travel a shorter distance to reach the phosphor screen, thereby reducing the possibility of causing the electron beams to wrongly land onto the phosphor screen. As the result, the picture quality of the color cathode ray tube can be remarkably enhanced. It will be described how the above-mentioned components are bonded to one another. Frit glass is used to attain bonding between the first and second thin metal plates which serve as the first and second insertion means and the glass of which the funnel sections are made. Frit glass is baked at about 450°C for an hour to establish bonding between the thin metal plates and the glass. Thermal expansion coefficients of the thin metal plates and the glass thus bonded is 99.0 (10⁻⁷/°C) in the case of the insertion means and 100.0 (10⁻⁷/°C) in the case of the glass of which the funnel sections are made. Therefore, no distortion is left in both of the thin metal plates and the glass bonded. An oxidation layer is formed on each of those areas of the thin metal plates to which frit glass is to be bonded so as to strengthen the bonding ability of frit glass. Seam welding is used to connect metal to metal. Resistance seam welding is used to attain bonding between the rear plate made of metal and the thin metal plates which serve as the insertion means. Welded portions are separated as remote as possible from those portions which are bonded by frit glass. This is intended to prevent the frit-glass-bonded portions from being deformed by the heat caused at the welding process and the frit seals from being peeled off from these bonded portions. According to the color cathode ray tube as described above, the rear plate and the skirt as well as the rear plate and the funnel sections can be reliably connected to each other by the frit glass and the thin metal plates. The thermal expansion coefficient of the alloy of which the insertion means is made is substantially same as that of the glass of which the funnel sections are made, thereby preventing the envelope from being distorted by heat. Although seam welding has been used to weld metal to metal, one of other welding manners such as plasma, laser and ultrasonic weldings may be employed. Although the first and second insertion members have been made 50% nickel alloy, they may be made of another alloy which contains 52% of nickel and 6% of chrome. Various kinds of variations which have been mentioned as the first insertion means to describe the envelopes of the present invention may be used. It has been shaped like a plate, but it may be curved to have same curvature as that of the face plate. Each of the reinforcing members is L-shaped, but when one of other welding manners such as arc and plasma weldings is employed, it is unnecessary to make the reinforcing members L-shaped. When the rear plate is made 5 mm thick, no reinforcing member is needed. Namely, no reinforcing member is needed when the rear plate is made thick enough to resist atmospheric pressure.

Claims: A vacuum envelope for a cathode ray tube comprising: a plurality of funnel sections (50) each having a front and a rear side respectively; a plurality of neck sections (52), one neck section being arranged on each rear side of the funnel sections; a panel section (42) including a face plate (44) having an inner surface, and a skirt (46) extending from a peripheral edge of the face plate; characterized by comprising: a metal connecting means (48) for connecting each front side of the funnel sections to the skirt of the panel section, the metal connecting means having a main surface substantially parallel to the inner surface of the face plate, an outer face, and a plurality of openings (58) on the main surface corresponding to the front side of each of the funnel sections. The envelope according to claim 1, and further comprising : a plurality of first insertion means (98) for insertion between each of the funnel sections and the metal connecting means, said plurality of first insertion means having a thermal expansion coefficient lower than a thermal expansion coefficient of the metal connecting means; and a plurality of second insertion means (100) for insertion between the skirt of the panel section and the metal connecting means, said plurality of second insertion means having a thermal expansion coefficient lower than that of the metal connecting means. The envelope according to claim 1 or 2, wherein a plurality of reinforcing members (56) are attached to the outer face of said metal connecting means, said plurality of reinforcing members serving to resist atmospheric pressure. The envelope according to claim 1 or 2, wherein said metal connecting means has a curvature which is the same as a curvature of the face plate, said metal connecting means is separated from the face plate by a certain distance and is arranged perpendicular to the tube axis. The envelope according to claim 1, wherein said metal connecting means has a step (59) between a first portion of said metal connecting means which is bonded to the skirt and a second portion of said connecting means which is bonded to the funnel sections, said second portion which is bonded to the funnel sections is spaced farther from the face plate than said first portion which is bonded to the skirt. The envelope according to claim 2, wherein each of said first insertion means has a cylindrical portion including two ends thereof, and one disk portion projecting outward and horizontally from each end of the cylindrical portion. The envelope according to claim 2, wherein each of said first insertion means has a cylindrical portion including two ends thereof, and one disk portion projecting inward and horizontally from each end of the cylindrical portion. The envelope according to claim 2, wherein each of said first insertion means has a cylindrical portion and a disk portion which projects inward and horizontally from one end of the cylindrical portion while a second disk portion projects outward and horizontally from a second end of the cylindrical portion. A color cathode ray tube comprising: a vacuum envelope according to any one of the preceding claims, and further comprising : a phosphor screen (64) disposed on the inner surface of the face plate; a shadow mask (66) disposed near the phosphor screen; and a plurality of electron gun assemblies (62), each of the electron gun assemblies being arranged in the neck sections, respectively.

Inventors: NISHIMURA, TAKASHI INTELLECTUAL PROPERTY DIVISION, TAKENAKA, SHIGEO INTELLECTUAL PROPERTY DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1989
Main classification: H01J29
IPC codes: H01J31, H01J29