GB2243945A

GB2243945A - Cathode ray tube having 16 x 9 aspect ratio

Info

Publication number: GB2243945A
Application number: GB9108839A
Authority: GB
Inventors: Alfredo Maresca; Paolo Spina
Original assignee: Videocolor SpA
Current assignee: Videocolor SpA
Priority date: 1990-05-11
Filing date: 1991-04-24
Publication date: 1991-11-13
Anticipated expiration: 2011-04-24
Also published as: CA2039822A1; FR2662021A1; GB2243945B; CN1018968B; TR25115A; GB9108839D0; DE4114606A1; JPH04229534A; CA2039822C; PL290205A1; IT9020271A0; IT9020271A1; CS128391A2; DE9116705U1; FR2662021B1; KR910020789A; KR940010952B1; PL164198B1; JP2611885B2; CZ544U1

Abstract

In a cathode-ray tube 10 with a rectangular faceplate panel 12 having long sides L and short sides S, with an aspect ratio of 16/9, and a major axis X parallel to the long sides and a minor axis Y parallel to the short sides, and having a rectangular viewing screen 22 on the inner surface of the faceplate panel, the long sides of the panel have a radius of curvature, in a plane of the major and minor axes, that is 7 to 10 times longer than a diagonal dimension of the viewing screen, and the ratio of the radius of curvature of the long sides to the radius of curvature of the short sides is in the range of 1.6 to 1.9. A number of specific examples giving numerical dimensions and ratios are disclosed. The disclosed arrangements provide CRT panels which are lighter in weight and require less room in the cabinet than prior art panels. <IMAGE>

Description

1 CATHODE-RAY TUBE HAVING 16 X 9 ASPECT RATIO - This invention relates to

cathode-ray tubes (CRT's) and, particularly, to the peripheral shapes of the faceplate panels of such tubes having approximately 16 x 9 rectangular aspect ratios.

Until now, commercial television cathode-ray tubes have had viewing screens and panels with 4 x 3 aspect ratios., (Aspect ratios are given in width or horizontal dimension to height or vertical dimension.) In the near future, however, cathode-ray tubes having wider aspect ratios will be required when higher definition television systems are introduced into commercial television. Most motion pictures are filmed in an approximate aspect ratio of 22 x 9. However, since a cathode-ray tube having a 22 x 9 aspect ratio would be excessively heavy for its size, the tube industry has standardized on a lower 16 x 9 aspect ratio, as a compromise for the future higher definition systems.

The early development tubes that have been constructed with the 16 x 9 aspect ratio have had faceplate panels that included peripheral sides with relatively large curvature. The purpose of curving the peripheral sides is to provide the panel with sufficient strength to withstand atmospheric pressure when the tube is evacuated. The drawback of a panel having sides with large peripheral side curvature is that additional space must be provided in a television receiver cabinet to accommodate the cathode-ray tube. However, receiver des ' igners would like to keep the size of the cabinets as small and as light as possible.

Making a tube with a panel having straight sides would provide a tube with minimum dimensions, but would require an undesirable increase in glass thickness, and thus also in tube weight. Therefore, there is a need for a cathode-ray tube design that provides a compromise of minimized height and width of the tube panel and minimized tube weight.

The present invention provides an improvement in a cathode-ray tube that includes a rectangular faceplate panel having two peripheral long sides and two Peripheral short sides, wherein the ratio of length of the long sides to the length of the 2 RCA 86,034 short sides is approximately 16/9. The tube includes a major axis which parallels the two long sides and a minor axis which parallels the two short sides. A rectangular viewing screen is located on an inner surface of the faceplate panel. The improvement comprises the long sides of the panel having a radius of curvature in a plane of the major and minor axes that is about 7 to 10 times longer than a diagonal dimension of the viewing screen, and the ratio of the radius of curvature of the long sides to the radius of curvature of the short sides being in the range of about 1.6 to 1.9.

FIGURE 1 is a side view, partly in axial section, of a shadow mask color picture tube incorporating one embodiment of the present invention.

FIGURE 2 is a plan view of the backside of the faceplate of the tube of FIGURE 1.

FIGURE 3 is a composite plan view of the outer periphery of quadrants of a faceplate panel showing a straight side, a prior art curved side and a novel curved side.

FIGURE 1 shows a rectangular color picture tube 10 having a glass bulb or envelope 11 comprising a rectangular faceplate panel 12 and a tubular neck 14 connected by a rectangular funnel 15. The funnel 15 has an internal conductive coating (not shown) that extends from an anode button 16 to the neck 14. The panel 12 comprises a rectangular viewing faceplate 18 and a peripheral flange or sidewall 20 which is sealed to the funnel 15 by a glass frit 17. A three-color phosphor screen 22 is carried by the inner surface of the faceplate 18. The screen 22 preferably is a line screen with the phosphor lines arranged in triads, each triad including a phosphor line of each of the three colors. Alternatively, the screen can be a dot screen, and it may or may not include a light-absorbing matrix. A multi-apertured color selection electrode or shadow mask 24 is removably mounted in predetermined spaced relation to the screen 22. An electron gun 26, shown schematically by dashed lines in FIGURE is centrally mounted within the neck 14 to generate and direct three electron beams 28 along convergent paths through the 24 to the screen 22.

3 RCA 86,034 The tube of FIGURE I is designed to be used with an external magnetic deflection yoke, such as the yoke 30 shown in the neighborhood of the funnel-to-neck junction. When activated, the yoke 30 subjects _the, three beams 28 to magnetic fields which cause the beams to scan horizontally and vertically in a rectangular raster over the screen 22. The initial plane of deflection (at zero deflection) is at about the middle of the yoke 30. Because of fringe fields, the zone of deflection of the tube extends axially from the yoke 30 into the region of the gun 26.

For simplicity, the actual curvatures of the deflected beam paths in the deflection zone are not shown in FIGURE 1.

As shown in FIGURE 2, the rectangular faceplate panel 12 includes two orthogonal axes, a major axis X and a minor axis Y, and two diagonals D. The two long sides, L, of the periphery of the faceplate panel 12 substantially parallel the major axis X, and the two short sides, S, substantially parallel the minor axis Y. Preferably, both the long and short sides of the faceplate are curved in the X, Y and D plane, with the ratio of the radius of curvature of a long side to the radius of curvature of a short side being in the range of about 1.6 to 1.9. Furthermore, the ratio of the radius of curvature of a long side to the diagonal dimension of the screen is in the range of about 7 to 10. These ranges represent an optimum design for a tube having a 16 x 9 aspect ratio.

Table I presents dimensions and ratios for three 16 x 9 faceplate panels that are within the scope of the present invention [(I) to 3)], two 16 x 9 faceplate panels that are indicative of the prior art [(4) and (5)] and three 4 x 3 faceplate panels [(6) to (8)], for comparison purposes.

4 RCA 86,034 TABLEI

Screen Long Side Short Side Tube Diagonal Radius Radius Long/Short Long/Diag.

Type (MM) (MM) (MM) Radius Ratio Ratio New 16x9 (1) 863.6 7691.06 4280.33 1.797 8.906 (2) 762 6450.15 3504.73 1.840 8.465 (3) 660.4 5001.21 2999.41 1.667 7.573 Prior 16x9 (4) 863.6 3003 2683 1.119 3.477 (5) 762 2652 2370 1.119 3.480 Prior 4x3 (6) 889 5522 5434 1.016 6.211 (7) 787.4 4837.39 4703.71 1.028 6.143 (8) 685.8 5408.96 3941.42 1.372 7.887 FIGURE 3 illustrates a composite of the long side curvatures for three types of 16 by 9 aspect ratio faceplate panels: a panel with straight sides 32, a prior art panel with greater curved sides 34 and a novel panel with lesser curved sides 36. From an aesthetics and space point of view, the panel having the straight sides 32 is the most desirable. However, the stresses in the panel with straight sides are relatively high, thereby necessitating a substantial increase in the thickness and weight of the panel over that of a prior art panel. Although the prior art panel design permits use of thinner and lighter glass, the greater curvature of the sides of the panel requires a larger space in a television receiver cabinet, thereby resulting in a bulkier product. A faceplate panel constructed in accordance with the present invention requires less room in a receiver cabinet and is slightly lighter in weight than the prior art panel. Finite element calculations performed on the novel panel indicate that the stresses within the glass of the novel panel are higher than that found in the prior art panels, but that when the novel panels are

1 1 RCA 86,034 assembled into tubes with implosion protection means thereon, the tubes with the novel panels show no increase in implosion possibility over the prior art tubes.

6 RCA 86,034

Claims

1. A cathode-ray tube including a rectangular faceplate panel having two long sides and two short sides, the ratio of the length of said long sides to the lengths of said short sides being approximately 16/9, said tube including a major axis which parallels said two long sides and a minor axis which parallels said short sides, and said tube including a rectangular viewing screen on an inner surface of said faceplate panel, comprising said long sides of said panel having a radius of curvature in 0 a plane of said major and minor axes that is about 7 to 10 times longer than a diagonal dimension of said viewing screen, and the ratio of the radius of curvature of said long sides to the radius of curvature of said short sides being in the range of about 1.6 to 1.9.

2. The tube as defined in claim 1, wherein, when the diagonal dimension of said viewing screen is about 864 mm, said long sides of said panel have a radius of curvature of approximately 7691 mm, and said short sides have a radius of curvature of approximately 4280 mm.

1 1 k

3. The tube as defined in claim 1, wherein the ratio of said long sides to said diagonal is about 8.9, and the ratio of the radius of curvature of said long sides to the radius of curvature of said short sides is about 1.8.

& 1 1 0 7 RCA 86,034

4. The tube as defined in claim 1, wherein when the diagonal dimension of said viewing screen is about 762 mm, said long sides of said panel have a radius of curvature of approximately 6450 mm 5 and said short sides have a radius of curvature of approximately 3504 mm.

5. The tube as defined in claim 1, wherein the ratio of said long -sides to said diagonal is about 8.5 and the ratio of the radius of curvature of said long sides to the radius of curvature of said short sides is about 1.8.

6. The tube as defined in claim 1, wherein when the diagonal dimension of said viewing screen is about 660 mm, said long sides of said panel have a radius of curvature of approximately 5001 mm and said short sides have a radius of curvature of approximately 2999 mm.

7. The tube as defined in claim 1, wherein the ratio of said long sides to said diagonal is about 7.6 and the ratio of the radius of curvature of said long sides to the radius of curvature of said short sides is about 1.7.

8. A cathode ray tube substant-ially as hereinbefore described withreference to the accompanying drawings.

Published 1991 at The Patent office. Concept House. Cardiff Road, Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch, Unit 6, Nine Mile Point, Cwinfelinfach. Cross Keys, Newport, NPI 7HZ. Printed by Multiplex techniques ltd, St Mary Cray, Kent.