MXPA01003673A - Color picture tube having a tension focus mask - Google Patents

Abstract

A color picture tube (10) comprises an evacuated envelope (11) having an electron gun (26) therein for generating at least one electron beam (28), a faceplate panel (12) having a luminescent screen (22) with phosphor lines on an interior surface thereof, and a tension focus mask (24). The mask has spaced apart first metal strands (40) which are adjacent to an effective picture area of the screen and define a plurality of slots substantially parallel to the phosphor lines. Each of the first metal strands across the effective picture area has a substantially continuous insulator layer (41) on a screen-facing side thereof. The mask also includes a plurality of second metal strands (42) oriented substantially perpendicular to the first metals strands. The second metal strands are spaced from the insulator layer when the tube is not energized and are in contact with the insulator layer when the tube is energized.

Description

COLOR PICTURE TUBE WITH A TENSION FOCUS MASK FIELD OF THE INVENTION The invention relates to color image tubes having voltage masks, and in particular to a color image tube having a tension focusing mask.

BACKGROUND OF THE INVENTION A color image tube includes an electron gun to generate and direct three electron beams towards a screen of the tube. The screen is located on the inner surface of a front face plate of the tube and comprises an array of three elements different color emitting matches. A color selection electrode, which may be a shadow mask or a focus mask, is interposed between the gun and the screen, to allow each electron beam to strike only the phosphor elements associated with the beam. A shadow mask is a thin sheet of metal, such as steel, having the outline to be somewhat parallel to the inner surface of the front plate of the tube. A focus mask comprises double sets of conductive lines that are perpendicular to each other and are usually separated by an insulating layer. 25 U.S. Patent No. 5,646,478, issued to R.W.

Nosker et al., July 8, 1997, and U.S. Patent No. 5,647,653, granted to S.C. Cherukuri, on July 5, 1997 expose focus mask tubes, where the masks are formed by two perpendicular sets of metallic strands. A set of strands is under tension and includes an insulating coating that is applied in two layers of different materials. The second or upper layer is used to join the second group of strands with the first set, by sintering. The second or upper layer 45 is used to join a second set of strands with the first game, by sintering. U.S. Patent No. 5,629,051, issued to E.S. Poliniak, on May 13, 1997, explains a method for applying an insulating coating to the first set of fibers. There are certain problems with the technique to join the two sets of threads. For example, a second insulating layer can be crushed, thereby leaving particles inside the tube. When subjected to some impact, the strands can be displaced from each other, and due to their mutual union, the strands may not be able to return to their original position. The present invention provides a mask structure that eliminates these problems.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a color image tube comprising an evacuated cover having a spray gun. electrons inside it, to generate at least one ray of electron, a front face board that has a luminescent screen with phosphor lines on an inner surface thereof and a tension focus mask. The mask has a first separated metal strands that are adjacent to a effective image area of the screen and define a plurality of slots essentially parallel to the phosphor lines. Each of the first metallic strands through the effective image area has an essentially continuous insulating layer, on a confronting side of the screen. The mask also includes a plurality of second metal strands oriented essentially perpendicular to the first metal strands. The second metallic fibers are separated from the insulating layer when the tube is not energized and are in contact with the insulating layer when the tube is energized. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view, partially in axial section, of a color image tube embodying the invention. Figure 2 is a perspective view of a unit of frame-shadow mask tensioned in the tube of Figure 1. Figure 3 is an isolated view of a vertical fiber in cross section, and a horizontal fiber taken in the circle 3 in Figure 2. Figure 4 is the same as seen in Figure 3, during the 23 tube activation & S? &JSJSfi. jjj .tiA-fcjm- DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a color image EPP 10 having a glass cover 11, which comprises a board 12 of front, rectangular plate 5 and a tubular neck 14 connected by a rectangular funnel 15. The funnel 15 has an internal conductive main coating (not shown), which extends from a first anode button 16 towards the neck 14. A second anode button 17, located on the opposite side to the first button of anode, it's in contact with a second secondary coating, internal conductor, of the funnel 15. The board 12 comprises a front plate 18 of essentially flat view and a flange or peripheral side wall 20, which is sealed with the funnel 15 by a glass layer 21 . A three-color phosphor screen is carried by the inner surface of the faceplate 18. The screen 22 is a line screen with the phosphor lines arranged in thirds, each tertium includes a line of phosphorus, of each of the three colors. The phosphor lines are approximately parallel to the minor axis Y of the tube A tension focus mask 24 is removably assembles in a predetermined spaced relation of the screen 22. An electron gun 26, shown schematically by dotted lines in Figure 1, is mounted centrally within the neck 14 to generate and direct three electron beams in line, a central ray and two external or lateral rays, to along converging paths through mask 24 towards the screen 22. The tube 10 is designed to be used with an external magnetic deflection yoke, such as a yoke 30 shown near the funnel-to-neck junction. When activated, the yoke 30 subjects the three rays to magnetic fields, which cause the rays to be scattered horizontally and vertically in a frame on the screen 22. The tension focus mask 24, shown in Figure 2 , is preferably made of a thin rectangular sheet of about 0.05 mm (2 mil) thick of low carbon steel. The screen is engraved to the strong in a plurality of first metallic strands 40, each with a transverse dimension, or width of approximately 0.3 mm (12 mils), separated by equally spaced grooves, each with a width approximately 0.55 mm (21.5 mils), and approximately parallel to the minor Y axis of the tube. In a colored tube with a diagonal dimension of 68 cm (27V), there are around 600 first metallic strands. A surface of each strand 40 is coated with an insulating layer 41. Preferably, layer 41 is continues along the length of each strand 40. A plurality of second metal strands 42, each having a diameter of about 0.025 mm (1 mil), is disposed essentially perpendicular to the first metal strands 40. The preferred material for second metal strands is wire Invar (TM Reg # 63,970) The separation or vertical space between "^., .., *. ^. * .." ^. ^ I. »^., *, ^" -1 - »-,», .. ^ - -, - ^. S-. ~ ^ ^^? ^ i- a ^^^^ second adjacent 42 strands is approximately 0.41 mm (16 mils). The second relatively thin metal strands 42 cooperate with the first metal strands 40 to provide focus of the electron beams 28. The focus mask, as described herein, provides a mask transmission, in the center of the screen, of approximately 60%. For a conventional shadow mask, the transmission is 18% to 20%. When the tube is energized, the voltage applied to the first metal strands 40 differs from the voltage applied to the second metal strands 42 by less than 1 kV, at an anode voltage of approximately 30 kV. The voltages are applied to the two anode buttons 16 and 17 and conducted to the strands 40 and 42, respectively, by the internal and secondary secondary coatings of the funnel 15. A frame 44 is shown in Figure 2., to support the tension focus mask 24. The frame 44 includes a long rectangular section 46 having two long sides 48 and 50, essentially parallel to the major axis X of the tube and two short sides 52 and 54, parallel to the minor axis Y of the tube. The long sides 48 and 50 have more than twice the height, in the Z direction of the longitudinal axis, of the height of the short sides 52 and 54. The plurality of first metallic strands 40 extends between the long sides 48 and 50 of the section 46 of the frame. Connected to the short sides 52 and 54, by means of springs 56, there are two second thread support sections 58 and 60, respectively. The two sections 58 and 60 are spaced apart and parallel to the short sides 52 and 54. The plurality of second metal strands 42 'are connected and extend between the two sections 58 and 60, with the springs 56 applying slight tension to the strands 42. The second metal strands 42 must be electrically isolated from the first metal strands 40. . There are several ways to achieve the insulation, such as forming springs 56 or sections 58 and 60 of non-conductive materials or forming the components of laminated materials, with one of the non-conductive laminates. In contrast to the tension focusing masks of the previous patents mentioned above, the second metal strands 42 are not permanently joined to the first metal strands 40, by an insulating layer, instead, they are separated from the layers. 41 insulators in the first strands 40 , as shown in Figure 3. However, as shown in Figure 4, when the tube 10 is energized, for example with a difference of five hundred volts between the first and second metal strands 40 and 42, a electrostatic attraction between the two sets of strands, which leads to second metal strand 42 in contact with the insulating layers 41 in the first metal strands 40. Preferably, the insulating layers 41 have a thickness within the range of 0.05 to 0.09 mm (2 to 3 6 mils) through the strands 40. The preferred material for the insulating layers 41 is a glass blowtorch, dephosphorized lead-zinc-borosilicate that melts within the range of 400 ° to 450 ° C and is commercially available as SCC-11, from a variety of suppliers, including SEM-COM, Toledo, Ohio and Corning Glass, New York. The set of metal strands 42, preferably, are separated approximately 0.025 to 0.05 mm (1 to 2 mils) from the insulating layers 41 in the strands 40, when the tube 10 is inactive. An advantage of the construction of the mask described above is that the strands are free to return to their normal positions when their electrical potentials are removed. Therefore, the positions of the strands are not affected by the mechanical impacts, which could otherwise displace them if they were together permanently.

Claims (2)

1. A color image tube, which comprises a cover evacuated with an electron gun thereon to generate at least one electron beam, a front face board having a luminescent screen with phosphor lines on an inner surface of the same, and a tension focusing mask having first separated metal strands, which are adjacent to an effective area of the screen image and which define a plurality of slots essentially parallel to the phosphor lines, each of the first metal strands through the effective image area has a continuous essentially insulating layer on the confronted side of the screen, and a plurality of second metal strands oriented essentially perpendicular to the first metal strands, characterized in that the second metal strands are separated from the layers insulators, when the tube is not energized and are in contact with the insulating layers when or the tube is energized.

2. The color image tube, according to claim 1, characterized in that the second metal strands are separated from the insulating layers a distance that allows the contact of the second metal strands with the insulating layers through an electrostatic attraction when the tube is energized