JPH0449218B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube (CRT), and more particularly to the surface shape of a faceplate panel of a cathode ray tube.

[Behind the invention]

There are two basic faceplate panel profiles available and used for rectangular CRTs with screens larger than approximately 23 cm diagonally: spherical and cylindrical. A planar profile is also possible, but is undesirable because it increases the thickness and weight of the faceplate panel required to provide the same envelope strength. moreover,
If the flat face plate CRT is a shadow mask color picture tube, it is not preferable because the shadow mask suitable for this becomes heavy and complicated.

Recently, it has been proposed that spherical faceplate panels be improved by increasing the radius of curvature of the panel by a factor of 1.5 to 2. When the radius of curvature is increased, the face plate
The curvature of the panel is reduced so that the picture tube screen can be viewed off-axis with satisfactory results. Such cathode ray tubes with a large radius of curvature can provide improved viewing conditions, but
There is a demand for even flatter face plates or cathode ray tubes that appear flatter.

In 1983, a new way of thinking about the contours of faceplates and panels that gave them a flat-like feel was introduced in 1983.
Mr. Ragland (FR Ragland, Jr.) dated May 25th
US Patent Application No. 469772 (corresponding to Japanese Patent Application No. 59-34113) and US Patent Application No. 469774 (corresponding to Japanese Patent Application No.
No. 59-31321), U.S. Patent Application No. 469775 of RJD'Amato et al., filed February 25, 1983.
(corresponding to Japanese Patent Application No. 59-31320). The contour shape has curvature along both the major and minor axes of the faceplate panel, but is not spherical. In the preferred embodiments shown in each of these patent applications, the peripheral border of the picture tube screen is a flat plate. In such picture tubes, the face plate is designed to suitably harmonize the different curvatures extending from the long and short axes.
It is important to define the outline of the panel. In the picture tube shown in the above-mentioned U.S. Pat. It is taken.

SUMMARY OF THE INVENTION The present invention is directed to an improved cathode ray tube that includes a rectangular face plate having an outer surface with curvature along both the major and minor axes. A cathode ray tube also has a cathode ray luminescent screen on its inner surface. At least in the center of the face plate, the curvature along the short axis is at least 10 percent greater than the curvature along the long axis.
In the improved cathode ray tube, a point on the outer surface near the major axis at the edge of the screen lies in a first plane perpendicular to the longitudinal axis passing through the center of the tube, and a point on the outer surface near the major axis at the edge of the screen A point on the outer surface near the edge lies in a second plane parallel to and remote from said first plane, and a point on the outer surface near the diagonal end of the rectangular face plate at the edge of the screen lies in said first plane parallel to said first plane and remote from said plane; It lies in a third plane parallel to the first plane and remote from this plane. The three faces are spaced apart from the center of the face plate in the following order: second face, first face and third face.

The present invention proposes a faceplate panel profile that appears flatter than the longer radius picture tubes described above, yet does not require the use of thicker glass to maintain strength.

[Description of preferred embodiments]

FIG. 1 shows a rectangular cathode ray tube (CRT) in the form of a color picture tube 10 having a glass envelope 11 consisting of a rectangular faceplate panel 12 and a tubular neck 14 joined by a funnel 16.
shows. The panel is a face plate for observation 18
and the funnel 16 by the glass frit 17.
a peripheral flange or sidewall 20 sealed to the flange or sidewall 20; A rectangular tricolor cathodoluminescent phosphor screen 22 is supported by the inner surface of faceplate 18. Preferably, the screen is a linear screen with lines of phosphor extending substantially parallel to the short axis Y-Y of the tube (perpendicular to the plane of Figure 1), but dot screens are preferred. It's okay. A porous color selection electrode or shadow mask 24 is removably mounted within the faceplate panel 12 at a predetermined distance from the screen 22. In FIG. 1, an in-line electron gun 26, shown schematically by dotted lines, is connected to
The electron gun 2
6 generates three electron beams 28 and directs them along a coplanar convergent path through a mask 24 and towards a screen 22. The electron gun may be triangular or delta shaped.

The picture tube 10 in FIG. 1 has a network 14 and a funnel 1.
It is designed for use with an external magnetic deflection yoke, such as the yoke 30 shown schematically near these junctions, surrounding the three beams 28 and By applying magnetic flux, the beam is scanned horizontally in the major axis XX direction and perpendicularly in the minor axis Y-Y direction so as to draw a rectangular raster over the entire screen 22.

FIG. 2 shows the front side of faceplate panel 12. FIG. The perimeter of the panel 12 forms a rectangle with slightly curved sides. Screen 22
The boundaries of are indicated by dotted lines. The boundary of this screen is a rectangle with straight sides and right angle corners.

Cross-sections of a particular panel along the minor axis Y--Y, the major axis X--X, and the diagonal are shown in Figures 3, 4, and 5, respectively. Face plate panel 12
The outer surface of is curved along both the major and minor axes, with the curvature along the minor axis being greater than the curvature along the major axis, at least in the central portion of the faceplate panel 12. For example, at the center of the face plate, the ratio of the radius of curvature of the outer surface profile along the major axis to the radius of curvature along the minor axis is greater than 1.1 (ie, greater than a 10% difference). Points on the panel contour from a plane P perpendicular to the longitudinal axis Z-Z passing through the center of the picture tube and touching the center of the panel 12 to another plane parallel to this plane P (for example, P1, P2 or P3) The "sagittal height" was measured. The sagittal heights SH1, SH2, and SH3 relative to points on the outer surface of face plate 18 near each end of the minor axis, major axis, and diagonal are shown in FIGS. 3, 4, and 5, respectively. There is a relationship of SH1<SH2<SH3 between these three sagittal heights.

FIG. 6 is a superimposed view of the contours of the outer surface of the panel along the major axis, minor axis, and diagonal. Each contour shape terminates at the edge of the screen. The long axis profile ends in a first plane P1 perpendicular to the longitudinal axis Z--Z of the picture tube. The short axis contour is the first
ends in a second plane P2 parallel to and remote from the plane P1. The diagonal contour is parallel to the first surface P1 and a third surface P3 distant from this surface.
It ends with The three surfaces are spaced apart from the central portion of the face plate in the following order: second surface P2, first surface P1, and third surface P3. A point on the outer surface near the long axis end at the end of the screen lies within the first plane P1. A point on the outer surface near the minor axis end at the end of the screen lies within the second plane P2.
Points on the outer surface near the ends of the diagonals at the edges of the screen lie within the third plane P3. Second side P
2 and a plane P in contact with the center of the face plate, measured along the central longitudinal axis of the picture tube;
The ratio of the distance between the third surface P3 and the surface P is larger than the value obtained by dividing the length of the short axis of the screen to the square of the length of the screen to the power of the diagonal length of the screen, and It is smaller than 1. For a picture tube with an aspect ratio of 4:3, the lower limit of this spacing ratio is approximately 9/25. For a picture tube with a 5:3 aspect ratio, the lower limit of this spacing ratio is approximately 9/34. In order to accurately calculate the contour shape of the face plate, it is necessary to introduce other detailed factors.
Therefore, the above ratios are to be considered only as approximations. Similarly, the ratio of the distance between the first surface P1 and the surface P and the distance between the third surface P3 and the surface P is
greater than the square of the major axis of the screen divided by the square of the diagonal of the screen, and 1
It is smaller. For a picture tube with a 4:3 aspect ratio, the lower limit of this spacing ratio is about 16/25. For a picture tube with an aspect ratio of 5:3, the lower limit of the long axis spacing ratio is 25/34. In either case, the upper limit of 1 lies outside of this range, since a ratio of 1 indicates a flat edged faceplate. Alternatively, the distance between the second surface P2 and the third surface P3 is equal to the square of the short axis dimension of the screen divided by the square of the diagonal dimension of the screen.
is substantially equal to the distance between P and P multiplied by the distance between P and P.

Figure 7 shows lines 3-3 (minor axis) in Figure 2, A-A,
Short axis Y- cut along B-B and C-C
The outline of the outer surface parallel to Y is shown. Each profile is a curve in which the radius of curvature of each cross section increases with increasing distance from the minor axis.

The outer surface of one embodiment of the face plate is the eighth
As shown in the figure, there is symmetry in the quadrants with respect to the reference plane, and the variables are drawn according to two polynomials with a quartic even function that provides a smooth surface. The curve of the surface along the minor axis is a circular curve with radius of curvature Ro.
The curve of the side surface of the face plate parallel to the minor axis and at the edge of the screen is also a circular curve, but with a radius of curvature Re. The curve of the surface of the cross section parallel to the short axis between the short axis and the side edge of the screen is a circular curve, and its radius of curvature is
It is Ri. The radius of curvature Ri is a function of the distance along the long axis from the short axis, and the relationship Ro<Ri<Re holds true. The curve of the surface at the top and bottom of the face plate at the edge of the screen, parallel to the long axis, is a circular curve with radius of curvature Rl. The curve of the surface along the long axis is a slightly more complex function of distance from the short axis H(x). Basically, this long axis curve is a circular curve with a radius of curvature R near the center of the face plate, but the curvature increases near the sides of the face plate. This increase in curvature near the sides of the face plate can be thought of as a perturbation (causing a small variation in the function) with respect to the fundamental radius of curvature.

The following table shows the dimensions of a picture tube constructed as described herein and having a viewing screen with diagonal dimensions of 69 cm (27 inches).

Table SH1......18mm SH2......22mm SH3......26mm Ro......1150mm Re......5126mm Ri......>1150mm and >5126mm Rl......4574mm H(X)......1673 cover Perturbation R On the screen surface inside the face plate,
As is known, suitable wedges are added to the glass for strengthening purposes and improve the profile in the form of a two-variable polynomial.

9 to 12 compare the contour shapes of the surface of the face plate in the major axis, short axis, and diagonal directions indicated by the dotted lines with the four contour shapes of the face plate constructed by the solid lines. FIG. All picture tubes have a viewing screen diagonal dimension of 69 cm (27 inches).

FIG. 9 shows the outline of a spherical face plate with a standard radius of 1R. An example of a standard radius for a picture tube with a diagonal dimension of approximately 635 mm is approximately 1034 mm.
It is. Since the 1R face plate is a spherical surface, the contour shapes of the major axis and minor axis are on the diagonal contour shape. For the 1R face plate,
The sagittal height measured between the parallel plane passing through the diagonal ends and the center of the faceplate is 52mm
It is. The sagittal height difference between the long axis end and the short axis end is about 15 mm, and the sagittal height difference between the long axis end and the diagonal end is about 19 mm.

The sagittal height (26 mm) at the diagonal end of the profile of the novel faceplate according to this invention is the sagittal height (52 mm) of the standard 1R faceplate.
mm), but the curvature of the profile shape along the short axis of the new face plate is similar to that of the 1R face plate. Such curvature along the short axis of the novel faceplate allows the glass to have the necessary strength without significantly increasing its thickness, and can withstand external pressures when the picture tube is evacuated. The next two spherical faceplates, which have larger radii of curvature, provide the necessary strength by using relatively thicker glass, thus making the picture tube heavier.

FIG. 10 shows the profile of a reduced curvature spherical face plate with a radius of curvature that is 1.5 times the radius of curvature of the standard 1R face plate shown in FIG. 9, or about 1500 mm. The sagittal height of the 1.5R face plate is approximately 39mm. The sagittal height difference between the long axis end and the short axis end is approximately 11
mm, the sagittal height difference between the long axis end and the diagonal end is approximately 15 mm.

Figure 11 shows a radius of curvature twice that of the standard 1R face plate in Figure 9, that is, approximately 2000.
The profile of a spherical face plate with a smaller radius of curvature of mm is shown. The sagittal height for the 2R faceplate is 26mm, the same as that of the new faceplate profile. The sagittal height difference between the long axis end and the short axis end is 8 mm, and the sagittal height difference between the long axis end and the diagonal end is about 9 mm.

Spherical faceplates with even larger radii of curvature than 2R faceplates are theoretically possible, but the required weight on the faceplate glass and the additional complexity of the shadow mask design pose economic and commercial challenges. The above disadvantages arise. However, it is an object of the present invention to provide a new face plate and a picture tube that eliminate the above-mentioned drawbacks while giving the advantage that a picture tube with a flat face plate has in terms of viewing the display. I can do it. In a picture tube with a diagonal dimension of 69 cm, the perimeter of the new faceplate 18 at the edge of the screen varies only ±4 mm from the plane passing through the edge of the long axis profile. These changes are so slight that the edges of the screen appear substantially flat to the viewer. With such flat edges of the screen, even if the faceplate is curved,
Gives the feeling as if the screen is flat.
As illustrated by the sagittal height differences for each of the 1R, 1.5R, and 2R spherical faceplate examples, such a flat feel is not obtained with these spherical examples.

FIG. 12 shows the major axis, minor axis, and diagonal profile of the face plate for a flat edged face plate as described in the opening part of this specification. Such a profile presents a truly flat screen perimeter, but generally
If the diagonal profile of the flat edged face plate is formed with a considerable curvature, some surface distortion will be observed. This invention is
This forms a smooth faceplate surface without any undesirable surface distortion.

A preferred embodiment of a picture tube with a diagonal of 69 cm has a sagittal height difference of 4 mm between the first surface P1 and the second surface P2, and the sagittal height difference between the first surface P1 and the third surface P3.
Although the sagittal height difference between It is. Furthermore, the invention is not limited to any particular type of cathode ray tube screen or electron gun.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a part of a shadow mask color picture tube cut along the axis using an embodiment of the present invention, and FIG. 2 is a plan view of the part of FIG. 3, 4 and 5 are cross-sectional views taken along lines 3-3, 4-4 and 5-5 of FIG. 2, respectively, and FIG. 6 is a front view of the face plate panel of the picture tube. is a composite diagram showing the long axis, short axis, and diagonal outlines of the faceplate panel of the picture tube shown in Figure 1, superimposed on each other;
Composite diagram showing the contours of the faceplate panel along lines A-A, B-B and C-C overlaid; FIG. 8 is a quadrant of the faceplate panel of the invention showing the radius of curvature and function; Figure 9 showing
Figure 10 shows the major axis, minor axis and diagonal profile of a faceplate panel of the present invention compared to a standard radius spherical panel; Figure 11 shows the major, minor axes and diagonal profiles of the faceplate panel of the present invention compared to a double standard radius spherical panel; 12 is a diagram showing the major axis, minor axis, and diagonal profile of the faceplate panel of the present invention compared to an aspheric flat edge panel; FIG. 10...Cathode ray tube, 18...Face plate, 2
2... Cathode ray luminescent screen, P1... First surface, P
2...Second surface, P3...Third surface, P...Fourth surface,
X-X...Long axis, Y-Y...Short axis, Z-Z...Diagonal line.

Claims (1)

[Scope of Claims] 1. A cathode ray tube comprising a rectangular face plate having an outer surface having a curvature along both a short axis and a long axis, the face plate having a cathode ray luminescent screen on its inner surface. , a curvature along the minor axis at least at the center of the face plate is at least 10 percent greater than a curvature along the major axis; a point is in a first plane perpendicular to the longitudinal axis passing through the center between the cathode rays, and a point on the outer surface near the end of the short axis at the edge of the screen is from the first plane. a point on the outer surface near a diagonal end of the rectangular face plate at an edge of the screen is in a second plane spaced apart and parallel to the first plane; and the first
is in a third plane parallel to the plane of the face plate, and the first, second, and third planes are parallel to the first, second, and third planes and are in contact with the central portion of the face plate. The second surface, the first surface, and the third surface are spaced apart in this order from the surface of No. 4, and further, the curvature of the outer surface along the short axis is away from the center of the face plate It is essentially a circular curve towards the surface of
The curvature of the outer surface along the longitudinal axis is essentially circular near the center of the face plate, with increasing curvature toward the first surface near both sides of the face plate. cathode ray tube.