Space-saving cathode ray tube

Abstract
A cathode ray tube includes an electron gun directing electrons towards a faceplate having an electrode biased at screen potential. The electron beam is magnetically deflected to scan across the faceplate to impinge upon phosphors thereon to produce light depicting an image or information. A neck electrode near the tube neck is biased at or below screen potential and a second electrode between the neck electrode and the faceplate is biased at or above screen potential. As a result, the electrons are deflected over a greater total angle than is obtained from the magnetic deflection. A third electrode proximate the faceplate is biased at or below screen potential to direct electrons towards the faceplate, thereby to increase the landing angle of the electrons thereon. A metal and ceramic support includes a resistive voltage divider to which ones of the electrodes connect.
Description




The present invention relates to a cathode ray tube and, in particular, to a cathode ray tube including one or more deflection aiding electrostatic fields.




Conventional cathode ray tubes (CRTs) are widely utilized, for example, in television and computer displays. One or more electron guns positioned in a neck of a funnel-shaped glass bulb of a CRT direct a corresponding number of beams of electrons toward a glass faceplate biased at a high positive potential, e.g., 30 kilovolts (kV). The faceplate usually has a substantially rectangular shape and is generally planar or slightly curved. Together, the glass bulb and faceplate form a sealed enclosure that is evacuated. The electron gun(s) are positioned along an axis that extends through the center of the faceplate and is perpendicular thereto.




The electron beam(s) is (are) raster scanned across the faceplate so as to impinge upon a coating or pattern of phosphors on the faceplate that produces light responsive to the intensity of the electron beam, thereby to produce an image thereon. The raster scan is obtained by a deflection yoke including a plurality of electrical coils positioned on the exterior of the funnel-shaped CRT near the neck thereof. Electrical currents driven in first coils of the deflection yoke produce magnetic fields that cause the electron beam(s) to deflect or scan from side to side (i.e. horizontal scan) and currents driven in second coils of the deflection yoke produce magnetic fields that cause the electron beam(s) to scan from top to bottom (i.e. vertical scan). The magnetic deflection forces typically act on the electrons of the beam(s) only in the first few centimeters of their travel immediately after exiting the electron gun(s), and the electrons travel in a straight line trajectory thereafter, i.e through a substantially field-free drift region. Conventionally, the horizontal scan produces hundreds of horizontal lines in the time of each vertical scan to produce the raster-scanned image.




The depth of a CRT, i.e. the distance between the faceplate and the rear of the neck, is determined by the maximum angle over which the deflection yoke can bend or deflect the electron beam(s) and the length of the neck extending rearward to contain the electron gun. Greater deflection angles provide reduced CRT depth.




Modern magnetically-deflected CRTs typically obtain a ±55° deflection angle, which is referred to as 110° deflection. However, such 110° CRTs for screen diagonal sizes of about 62 cm (about 25 inches) or more are so deep that they are almost always provided in a cabinet that either requires a special stand or must be placed on a floor. For example, a 110° CRT having a faceplate with an about 100 cm (about 40 inch) diagonal measurement and a 16:9 aspect ratio, is about 60-65 cm (about 24-26 inches) deep. Practical considerations of increasing power dissipation producing greater temperature rise in the magnetic deflection yoke and its drive circuits and of the higher cost of a larger, heavier, higher-power yoke and drive circuitry make increasing the maximum deflection angle so as to decrease the depth of the CRT is disadvantageous.




A further problem in increasing the deflection angle of conventional CRTs is that the landing angle of the electron beam on the shadow mask decreases as deflection angle is increased. Because the shadow mask is as thin as is technically reasonable at an affordable cost, the thickness of the present shadow mask results in an unacceptably high proportion of the electrons in the electron beam hitting the side walls of the apertures in the shadow mask for low landing angles. This produces an unacceptable reduction of beam current impinging on the phosphor and a like decrease in picture brightness for low landing angles, e.g., landing angles less than about 25°.




One approach to this depth dilemma has been to seek a thin or so-called “flat-panel” display that avoids the large depth required by conventional CRTs. Flat panel displays, while desirable in that they would be thin enough to be hung on a wall, require very different technologies from conventional CRTs which are manufactured in very high volume at reasonable cost. Thus, flat panel displays are not available that offer the benefits of a CRT at a comparable cost. But a reduced-depth cathode ray tube as compared to a conventional CRT need not be so thin that it could be hung on a wall to overcome the disadvantage of the great depth of a conventional CRT.




Accordingly, there is a need for a cathode ray tube having a depth that is less than that of a conventional CRT having an equivalent screen-size.




To this end, the tube of the present invention comprises a tube envelope having a faceplate and a screen electrode on the faceplate adapted to be biased at a screen potential, a source of a beam of electrons directed toward the faceplate, wherein the source is adapted for magnetic deflection of the beam of electrons, and phosphorescent material disposed on the faceplate for producing light in response to the beam of electrons impinging thereon. At least first and second electrodes are interior the tube envelope, each defining a respective aperture through which the beam of electrons passes, wherein the first electrode is proximal the source and distal the faceplate and is adapted to be biased at a potential less than the screen potential, and wherein the second electrode is between the first electrode and the faceplate and is adapted to be biased at a potential not less than the screen potential. A third electrode is between the first electrode and the faceplate and is adapted to be biased at a potential not exceeding screen potential.




According to another aspect of the invention, a display comprises a tube envelope having a faceplate and a screen electrode on the faceplate biased at a screen potential, a source within the tube envelope of a beam of electrons directed toward the faceplate, a deflection yoke proximate the source of a beam of electrons for magnetically deflecting the beam of electrons, and a phosphorescent material disposed on the faceplate for producing light in response to the beam of electrons impinging thereon. At least first and second electrodes are within the tube envelope, each defining a respective aperture through which the deflected beam of electrons passes, wherein the first electrode is proximal the source and distal the faceplate and is biased at a first potential less than the screen potential, and wherein the second electrode is between the first electrode and the faceplate and is biased at a second potential not less than the screen potential. A third is between the second electrode and the faceplate and is biased at a potential not exceeding the screen potential. A source of potential provides the first, second, third and screen potentials.











BRIEF DESCRIPTION OF THE DRAWING




The detailed description of the preferred embodiments of the present invention will be more easily and better understood when read in conjunction with the FIGURES of the Drawing which include:





FIGS. 1 and 2

are cross-sectional schematic diagrams of an exemplary embodiment of a cathode ray tube in accordance with the present invention;





FIG. 3

is a graphical representation of the potential in the cathode ray tube of

FIG. 2

;





FIG. 4

is a cross-sectional diagram of the tube of

FIG. 2

illustrating the electrostatic forces therein;





FIG. 5

is a partial cross-sectional diagram of the yoke funnel region of another exemplary tube in accordance with the invention which tube includes a modification of the tube of

FIG. 2

;





FIG. 6

is a graphical representation illustrating the performance of the cathode ray tube of FIG.


2


and/or

FIG. 5

;





FIGS. 7A-7D

are cross-sectional diagrams showing a method of forming an electrode structure in a cathode ray tube according to the invention;





FIG. 8

is a partial cross-sectional diagram of an alternative exemplary structure providing appropriately positioned electrodes within a cathode ray tube in accordance with the invention;





FIGS. 9A and 9B

are a side cross-sectional and a front view diagrams, respectively, of an alternative exemplary structure providing appropriately positioned electrodes within a cathode ray tube in accordance with the invention.;





FIG. 10

is a partial cross-sectional diagram of another alternative exemplary structure providing appropriately positioned electrodes within a cathode ray tube in accordance with the invention;





FIG. 11

is a diagram of a support useful in the tube structure shown in

FIG. 10

;





FIG. 12

is a partial cross-sectional diagram of an alternative exemplary structure providing appropriately positioned electrodes within a cathode ray tube in accordance with the invention; and





FIG. 13

is a cross-sectional diagram of a further alternative exemplary structure providing appropriately positioned electrodes within a cathode ray tube in accordance with the invention.











In the Drawing, where an element or feature is shown in more than one drawing figure, the same alphanumeric designation may be used to designate such element or feature in each figure, and where a closely related or modified element is shown in a figure, the same alphanumerical designation primed may be used to designate the modified element or feature. Similarly, similar elements or features may be designated by like alphanumeric designations in different figures of the Drawing and with similar nomenclature in the specification, but in the Drawing are preceded by digits unique to the embodiment described. For example, a particular element may be designated as “xx” in one figure, by “1xx” in another figure, by “2xx” in another figure, and so on.




DESCRIPTION OF THE PREFERRED EMBODIMENTS




In a cathode ray tube according to the present invention, the electrons of the electron beam(s) are further deflected after leaving the influence of the magnetic deflection yoke, i.e. in what is referred to as the “drift region” of a-conventional CRT through which the electrons travel in substantially straight lines. In a conventional CRT, the electrons are at the screen or anode potential at the time they leave the gun and deflection regions and, not being under the influence of any electric or magnetic field, travel in straight lines to the screen or faceplate thereof. Such cathode ray tube may find application, for example, in television displays, computer displays, projection tubes and other applications where it is desired to provide a visual display.





FIG. 1

is a cross-sectional diagram of a cathode ray tube


10


according to the present invention in its simplest form. It is noted that unless otherwise specified, such cross-sectional diagrams may be considered to illustrate either the horizontal or the vertical deflection orientation because both appear similar in such diagrams.




In exemplary cathode ray tube


10


of

FIG. 1

, electrons produced by electron gun


12


located in tube neck


14


are directed towards faceplate


20


which includes a screen or anode electrode


22


which is biased at a relatively high positive potential. The electrons forming electron beam


30


produced by electron gun


12


are deflected by magnetic fields produced by deflection yoke


16


to scan across the dimension of faceplate


20


. Tube


10


is illustrated in

FIG. 1

in a somewhat theoretical way with two infinite parallel flat plates


20


′,


40


′ separated by a distance “L” representing the distance between flat backplate


40


′ and flat faceplate


20


′. Backplate


40


is also biased to a relatively high positive potential, but preferably less than the potential of screen electrode


22


, to which lesser potential the ultor of gun


12


is also biased for avoiding unusual electron-injection effects. Under the influence of electrostatic forces produced by the relatively high positive potential bias of backplate


40


and the magnetic field produced by deflection yoke


16


, electron beam


30


is deflected over a total deflection angle. A coating of phosphorescent material


23


is disposed on faceplate


20


for producing light in response to the beam of electrons


30


impinging thereon, thereby providing a monochromatic display, or a pattern of different phosphorescent materials


23


is disposed thereon for producing different colors of light in response to the beam of electrons


30


impinging thereon through apertures in a shadow mask (not shown), thereby providing a color display.




Further control of the bias potentials on the backplate of the tube to create a particular electrostatic and/or electrodynamic field may be employed in accordance with the invention to control the trajectories of the electrons of the electron beam


30


, thereby to reduce the required distance between the faceplate


20


and backplate


40


of an exemplary tube


10


, as shown in

FIG. 2

, and to change the landing angle of the electron beam


30


therein. Tube


10


includes a gun


12


in neck


14


generally symmetrically located substantially at the center of a backplate


40


to direct a beam of electrons


30


towards faceplate


20


which includes a screen electrode


22


biased at a relatively high positive potential. Faceplate


20


and backplate


40


are of similar size and are joined by an annular end plate


48


to form a sealed container that can be evacuated. Deflection yoke


16


surrounds neck


14


in the region of its juncture with backplate


40


for magnetically deflecting electrons generated by gun


12


as they proceed out of gun


12


and toward faceplate


20


to impinge upon the phosphor(s)


23


thereon. While tube


10


is illustrated as having a substantially rectangular in cross-section in

FIG. 2

, the glass envelope


40


-


42


of a typical glass tube


10


will more closely follow the shape of the widest trajectories


30


,


30


′ and so will resemble the shape of a conventional CRT, but be shorter in depth, and the cross-section perpendicular to the central Z axis is preferably more rectangular which tends to reduce the power required to drive magnetic deflection yoke


16


.




Electrostatic fields are established within tube


10


by a number of conductive electrodes located on or close to backplate


40


and biased at respective positive potentials, i.e. at potentials of like polarity to that of the screen or anode electrode


22


. A first electrode


44


surrounding the outlet of gun


12


in the vicinity of neck


14


is biased at a positive potential that is preferably less than the potential at screen electrode


22


. The electrostatic field produced by electrode


44


results in the electrons of the electron beam


30


being slower moving proximate yoke


16


, and therefore more easily deflected by yoke


416


. The result of the cooperation between electrode


44


and yoke


16


may be utilized to realize either a reduction of yoke power, and therefore a smaller, lighter, less expensive and likely more reliable deflection yoke


416


, or a greater deflection angle with the same yoke power and yoke.




A second electrode


46


also surrounding the outlet of gun


12


, but spaced away from the vicinity of neck


14


, is biased at a positive potential that is preferably greater than the potential at screen electrode


22


. The electrostatic field produced by second electrode


46


causes the electrons of beam


30


(and of its opposite extreme


30


″) to travel in a parabolic path that bends their trajectories away from faceplate


20


, thereby increasing the deflection angle from that produced by magnetic deflection yoke


16


alone, and also decreasing the landing angle of electron beam


30


. It is desirable that electrode


46


be positioned so that the action of the electrostatic field of electrode


46


not act on the electrons of electron beam


30


until after they have been substantially fully acted upon by deflection yoke


16


.




The landing angle is the angle at which the electron beam


30


impinges upon screen electrode


22


, and in a color CRT, the shadow mask proximate thereto. As may be seen in

FIG. 2

by comparing electron beams


30


,


30


′ which impinge upon faceplate


20


near its periphery and electron beam


30


″ that impinges thereon near its center, the landing angle becomes smaller as the distance from the central or Z axis of tube


10


becomes greater and/or as the deflection angle of the electron beam


30


increases. Because the shadow mask has a finite non-zero thickness, if the landing angle is too small, e.g., less than about 25°, too many of the electrons will hit the sides of the apertures in the shadow mask instead of passing therethrough, thereby reducing the intensity of the electron beam reaching the phosphor on the faceplate


20


and of the light produced thereby.




Advantageously, electrode


48


is located distal the central or Z axis of tube


10


and near the periphery of faceplate


20


where the landing angle is smallest. A third electrode


48


also surrounding the outlet of gun


12


but substantially at the periphery of backplate


40


is biased at a positive potential that is preferably less than the potential at screen electrode


22


to direct the electrodes of beams


30


and


30


″ back towards faceplate


20


for increasing the landing angle of electron beams


30


,


30


′ near the periphery of faceplate


20


. Electrode


48


may be biased to a potential less than the potential at neck electrode


44


where desired to provide greater reduction of landing angle. Thus, the electrostatic fields created by electrodes


46


and


48


complement each other in that electrode


46


increases the deflection angle which decreases the landing angle at the periphery of faceplate


20


, and electrode


48


, which has its strongest effect near the periphery of faceplate


20


, acts to increase the landing angle in the region where it might otherwise be undesirably small.




The relationship and effects of the electrostatic fields described above cooperate in a tube


10


that is shorter in depth than a conventional CRT and yet operates at a comparable and/or reasonable deflection yoke power level. An exemplary potential distribution over the depth of tube


10


along its Z axis is illustrated in FIG.


3


. Potential characteristic


60


is plotted on a graph having distance from the exit of gun


12


along the ordinate and bias potential in kilovolts along the abscissa. Electrode


22


located at a distance L from gun


12


and represented by region Z


22


is biased at a relatively high positive potential V


22


represented at point


62


. In order from gun


12


at Z=0 are neck electrode


44


located proximate gun


12


and represented by electrode region Z


44


that is biased at an intermediate positive potential V


44


, electrode


46


located intermediate gun


12


and faceplate


20


and represented by electrode region Z


46


that is biased at a relatively high positive potential V


46


that is preferably higher than the screen potential V


22


, and electrode


48


located more proximate to faceplate


20


and represented by electrode region Z


48


that is biased at an intermediate positive potential V


48


that is preferably lower than screen potential V


22


(but could be equal thereto) and could preferably be lower than gun ultor potential V


44


.




Electrodes


44


,


46


,


48


,


22


and bias potentials V


44


, V


46


, V


48


, V


22


thereon produce the potential characteristic


60


that has a portion


64


in region A rising towards the screen potential V


22


thereby tending to slow the acceleration of electrons towards faceplate


20


to provide additional flight time during which the subsequent electrostatic fields act upon the electrons. Characteristic


60


has a portion


66


in region B in which the potential peaks at a level relatively higher than the screen potential V


22


thereby to cause the electrons to move along trajectories that depart further from central axis Z of tube


10


to increase the deflection angle and a portion


68


in region C in which the potential bottoms at a level lower than the screen potential V


22


and the gun potential V


44


thereby to cause the electrons to move along trajectories that turn toward faceplate


20


of tube


10


to increase the landing angle of the electron beam near the edges of faceplate


20


.




It is noted that the location of the gap between electrodes


44


and


46


can strongly affect the operation of tube


10


. If electrode


46


having a relatively very high positive potential bias extends too close to the exit of gun


12


(and/or neck electrode


44


does not extend sufficiently far therefrom), then the electrons emitted from gun


12


are accelerated and additional magnetic deflection effort is required of deflection yoke


16


(e.g., additional yoke


16


power, field and/or size) to provide the desired magnetic deflection. On the other hand, if neck electrode


44


extends too far beyond the exit of gun


12


, then the electrons spend too much time in region A in which electrostatic forces act counter to the deflection sought to be produced by magnetic deflection yoke


16


, thereby also increasing the power, field and/or size required of yoke


16


to deflect the electron to the corners of faceplate


20


, even with the beneficial effect of yoke amplifier


50


. Because electrode


46


in tube


10


acts to amplify the total deflection of electron beam


30


above that produced by yoke


16


, it may be referred to as a “yoke amplifier” and identified as


50


.




The particular values of bias potential are selected in accordance with a particular tube


10


to obtain, for example, a suitable balance of reduced tube depth and reasonable yoke power in consideration of the effects of each of the bias potentials. For example, as the bias potential V


44


of the ultor of gun


12


is increased, the required deflection power of yoke


16


increases and the depth of tube


10


decreases, indicating that a bias potential of intermediate value is desirable. Thus, a 165° tube with V


22


=30 kV and V


44


=20 kV is about 13.5-15 cm (about 5.4-6 inches) shorter than a conventional 110° CRT. A constant bias potential V


46


on electrode


46


causes the electrons to follow a substantially parabolic trajectory toward faceplate


20


in region B, however, increasing the bias potential V


46


reduces the electrostatic forces pulling electrons towards faceplate


20


, so that a bias potential V


46


that is near or greater than the screen potential V


22


is advantageous to cause the electrons to travel in a more nearly straight line trajectory or to curve away from faceplate


20


, thereby to increase the deflection angle and reduce the depth of tube


10


. Thus, a bias potential V


46


of about 30 -40 kV is desirable, but, for safety, should be kept below the potential at which X-rays that could penetrate the envelope of tube


10


could be generated, i.e. below about 35 kV. Finally, bias potential V


48


is preferably a low positive potential to provide an electrostatic force that turns the electrons deflected to the edge regions of faceplate


20


more toward faceplate


20


to increase the landing angle, preferably to above 25°. This field accelerates the electrons towards faceplate


20


subsequent to their being deflected by yoke


16


and the electrostatic field forces produced by bias potential V


46


and electrode


46


.




It is anticipated that the depth of tube


10


in accordance with the invention can be reduced in depth by about a factor of two as compared to a conventional 110° CRT, to provide a 100-cm (about 40-inch) diagonal 16:9 aspect ratio tube


10


having a total depth of about 35-36 cm (about 14 inches) including the neck


14


. Further reduction of about 5 cm (about 2 inches) can obtain if a bent gun that does not project directly rearward from backplate


40


is employed. It is noted that shaping backplate


40


(i.e. the glass funnel of tube


10


) to more closely conform to the trajectories of the furthest deflected electron beams


30


,


30


′ improves the effectiveness of the electrostatic forces produced by electrodes


44


,


46


,


48


, thereby to reduce the depth of tube


10


. In addition, the gradual potential change over distance illustrated in

FIG. 3

enables a larger diameter electron beam


30


where electron beam


30


exits gun


12


, thereby reducing space charge dispersion within electron beam


30


to provide a desirably smaller beam spot size at faceplate


20


. The spot size and divergence of electron beam


30


is controlled by the particular electron gun and the convergence of the desired yoke.





FIG. 4

is an exemplary embodiment of tube


10


(only half of tube


10


being illustrated because tube


10


is symmetrical about the Z axis, i.e. in what could be designated the X plane and the Y plane) of the sort mentioned above having a backplate shaped similarly to the most extremely deflected electron beams


30


,


30


′ and having electrodes


22


,


44


,


46


,


48


biased as described above to produce a potential distribution as in FIG.


3


. In

FIG. 4

, however, the electron beams


30


are not illustrated, but arrows are shown directed either towards or away from faceplate


20


representing the net electrostatic force acting on the electrons of beam


30


as they pass through the regions A, B and C as described above. In region A, the net electrostatic force directs the electrons towards faceplate


20


under the influence of the relatively high positive bias potential V


22


of screen electrode


22


and the intermediate positive bias potential V


44


on neck electrode


44


. In region B, the net electrostatic force deflects the electrons away from faceplate


20


under the influence of the relatively very high bias potential on backplate electrode


46


which exceeds the relatively high positive bias potential V


22


on screen electrode


22


. In region C, the net electrostatic force again directs the electrons towards faceplate


20


under the influence of the screen electrode


22


relatively high positive bias potential as assisted by the low positive bias potential V


48


on electrode


48


.




It is particularly noted that by virtue of the effect of the electrostatic force produced by the relatively very high bias potential on backplate electrode


46


(i.e. higher than the bias potential V


22


of screen electrode


22


), electrode


46


increases the deflection of the.electron beam


30


beyond that produced by the magnetic deflection of yoke


16


. Thus, electrode


46


in tube


10


acts to amplify the total deflection above that produced by yoke


16


, and so is referred to as a “yoke amplifier” and identified as


50


. In particular, note that the deflection amplification produced by the yoke amplifier


50


is directly proportional to the deflection of any particular electron by yoke


16


. In other words, electrons moving towards faceplate


20


along or near the Z axis (i.e. those undeflected or little deflected by yoke


16


) are not affected by the yoke amplifier


50


. Those electrons deflected by yoke


16


to land intermediate the Z axis and the edge of faceplate


20


are additionally deflected by yoke amplifier


50


because they pass through a portion of region B in which yoke amplifier


50


acts. Those electrons deflected by yoke


16


to land near the edge of faceplate


20


are additionally deflected an even greater amount by the yoke amplifier


50


because they pass through the entirety of region B in which yoke amplifier


50


acts and so are more strongly affected thereby. Yoke amplifier


50


may also be considered to include neck electrode


44


which, when biased at a potential less than the screen potential, beneficially reduces the effort or power required by deflection yoke


16


to obtain a given deflection of electron beam


30


.




It is also noted that tube


10


may also be advantageous because it “looks like a conventional CRT” with a shaped glass bulb and neck, and a planar or slightly curved faceplate, and so may utilize similar manufacturing processes as are utilized for conventional CRTs. The issues of space charge effects expanding the electron beam are also similar to those in conventional CRTs and so the spot size variation with a smaller spot at the center of the faceplate and a somewhat larger spot size at the edges and corners is similar to that of the conventional CRT, although the structure and operation of tube


10


is very different therefrom. While the inventive tube


10


substantially reduced the front-to-back tube depth, the improvement is in the conical section of the glass bulb. In addition, the length of the tube neck


14


necessary to contain electron gun


12


, typically less than about 23-25 cm (about 9-10 inches), can be reduced if a shorter electron gun


12


is employed.





FIG. 5

is a partial cross-sectional diagram of an alternative embodiment of tube


10


identified as tube


10


′ in which electrode


46


of tube


10


is replaced by an alternative electrode


46


′ comprising a plurality of electrodes each having a particular value of bias potential applied thereto. Electrode


46


′ includes, for example, six electrodes


46




a


,


46




b


,


46




c


,


46




d


,


46




e


and


46




f


spaced apart along a section of tube backplate


40


forward of gun


12


, neck


14


and magnetic deflection yoke


16


. Electron beam


30


exits gun


12


directed towards faceplate


20


(not visible) and is magnetically deflected by an angle α, a high value of which is represented by dashed line


17


, typically up to an angle of ±55° with a conventional yoke


16


for a 110° tube. In addition, electron beam


30


is deflected up to an additional angle β under the action of the yoke amplifier


50


effect produced by the electrostatic fields produced by the relatively high positive bias potentials of electrode


46


′ to have a total deflection angle Θ with respect to Z axis


13


.




It is noted that electrode


46


, whether a single electrode


46


or plural sub-electrodes


46




a


,


46




b


, . . . , may be referred to as a “yoke amplifier,” a “deflection amplifier” or an “electrostatic deflection amplifier”


50


because it increases the deflection of electron beam


30


beyond the deflection produced by deflection yoke


16


. In particular, the amount of increase in the deflection of electron beam


30


increases as the angle of deflection produced by yoke


16


increases. For example, electron beam


30


when directed along central axis


13


or only slightly deflected therefrom, e.g., by about 20° or less, continues to travel in a straight trajectory unaffected by electrode


46


.




In tube


10


′ the electrodes


46




a


-


46




f


are preferably biased at different relatively high positive potentials so as to more precisely shape the potential characteristic thereof (similar to characteristic


60


of

FIG. 3

) while not accelerating the electrons of electron beam


30


towards faceplate


22


. Each of electrodes


46




a


-


46




f


is preferably a ring electrode proximate tube backplate


40


and typically having a “generally rectangular shape” surrounding Z axis


13


along which is electron gun


12


. Typical bias potentials for electrodes


46




a


-


46




f


are, for example, 30 kV, 32 kV, 34 kV, 35 kV, 33 kV and 31 kV, respectively, with each of gun


12


and screen electrode


22


(not visible) biased to 30 kV, although the bias potential for gun


12


could be lower than that of screen electrode


22


.




As used herein, “generally rectangular shape” or “substantially rectangular” refers to a shape somewhat reflective of the shape of faceplate


20


and/or the cross-section of tube envelope


40


when viewed in a direction along Z axis


13


. A generally rectangular shape may include rectangles and squares having rounded corners as well as concave and/or convex sides, so as to be suggestive of dog-bone shapes, bow-tie shapes, racetrack shapes, oval shapes and the like. It is noted that by so shaping electrodes


44


,


46


and/or


48


, the required waveform of the drive current applied to yoke


16


may be simplified, i.e. made closer to a linear waveform. Electrodes


44


,


46


,


48


may be oval in shape or even almost circular, particularly where the cross-section of tube envelope


40


is of such shape, as is often the case at the rearward portions thereof, such as those proximate neck


14


and yoke


16


.




The total deflection angle Θ obtained is the sum of the magnetic deflection angle α and the additional electrostatic deflection angle β. The magnetic deflection angle α is directly proportional to the deflection current applied to yoke


16


as illustrated by dashed line


17


of FIG.


6


and the additional electrostatic deflection angle β is greater for greater magnetic deflections, as described above in relation to tube


10


, producing line


31


representing the total deflection angle Θ. The deflection amplifying effect results from the action of the electric fields produced by electrodes


46




a


-


46




f


on the electrons of electron beam


30


to produce a net electrostatic force (integrated over the electron path) that pulls the electrons away from centerline


13


of tube


10


′, thereby increasing the total deflection angle Θ. This effect is aided by the bias potential on at least some or all of electrodes


46




a


-


46




f


being greater than the potential of screen electrode


22


.




The structure of plural electrodes


46


′ may be of several alternative forms. For example, electrodes


46




a


-


46




f


may be shaped metal strips printed or otherwise deposited in a pattern on the inner surface of the funnel-shaped glass backplate


40


of tube


10


′ and connected to a source of bias potential by conductive feedthrough connections penetrating the glass wall of funnel backplate


40


. The shaped metal strips can be deposited with a series of metal sublimation filaments and a deposition mask that is molded to fit snugly against the glass wall or backplate


40


. If a large number of strips


46




a


,


46




b


, . . . are employed, each of the strips


46




a


,


46




b


, . . . need only be a few millimeters wide and a few microns thick, being separated by a small gap, e.g., a gap of 1-2 mm, so as to minimize charge buildup on the glass of backplate


40


. A smaller number of wider strips


46




a


-


46




f


of similar thickness and gap spacing could also be employed. Deposited metal strips


46




a


,


46




b


, . . . are on the surface of glass backplate


40


thereby maximizing the interior volume thereof through which electron beam


30


may be directed.




Although bias potential could be applied to each of strips


46




a


,


46




b


, . . . by a separate conductive feedthrough, having too large a number of feedthroughs could weaken the glass structure of backplate


40


. Thus, it is preferred that a vacuum-compatible resistive voltage divider be employed within the vacuum cavity formed by backplate


40


and faceplate


20


, and located in a position shielded from electron gun


12


. Such tapped voltage divider is utilized to divide a relatively very high bias potential to provide specific bias potentials for specific metal strips


46




a


,


46




b


, . . .




One form of suitable resistive voltage divider may be provided by high-resistivity material on the interior surface of glass tube envelope


40


, such as by spraying or otherwise applying such coating material thereto. Suitable coating materials include, for example, ruthenium oxide, and preferably exhibit a resistance is in the range of 10


8


to 10


10


ohms. The high-resistivity coating is in electrical contact with the metal electrodes


44


,


46


,


48


for applying bias potential thereto. The thickness and/or resistivity of such coating need not be uniform, but may be varied to obtain the desired bias potential profile. Beneficially, so varying such resistive coating may be utilized for controllably shaping the profile of the bias potential over the interior surface of tube envelope


40


, for example, to obtain a bias potential profile such as illustrated in FIG.


3


. Thus, the complexity of the structure of electrodes


44


,


46


, and/or


48


may be simplified and the number of conductive feedthroughs penetrating tube envelope


40


may be reduced. In addition, such high-resistivity coating may be applied in the gaps between electrodes, such as electrodes


44


,


46


,


48


to prevent the build up of charge due to electrons impinging thereat.




An alternative to the masked deposition of metal strips


46




a


,


46




b


, . . . described above, the process illustrated in simplified form in

FIGS. 7A -7D

can be utilized. A mold


80


has an outer surface


82


that defines the shape of the inner surface of the funnel-shaped glass bulb


40


″ of a cathode ray tube


10


′ and has raised patterns


84




a


,


84




b


,


84




c


thereon defining the reverse of the size and shape of the metal strips


46




a


,


46




b


,


46




c


, as shown in FIG.


7


A. Upon removal from mold


80


, glass bulb


40


″ has a pattern of grooves


86




a


,


86




b


,


86




c


in the inner surface thereof of the size and shape of the desired metal stripes


46




a


,


46




b


,


46




c


, as shown in FIG.


7


B. Next, metal such as aluminum is deposited on the inner surface of glass bulb


40


″ sufficient to fill grooves


86




a


,


86




b


,


86




c


, as shown in FIG.


7


C. Then, the metal


88


is removed, such as by polishing or other abrasive or removal method, to leave metal strips


46




a


,


46




b


,


46




c


in grooves


86




a


,


86




b


,


86




c


, respectively, of glass bulb


40


″, with gaps


92




a


,


92




b


therebetween, as shown in FIG.


7


D. Conductive feedthroughs


90


provide external connection to metal strip electrodes


46




a


,


46




b


,


46




c


through glass bulb


40


″. Optionally, high resistivity material may be applied as a coating in the gaps


92




a


,


92




b


, between electrodes


46




a


,


46




b


,


46




c.






Other arrangements of exemplary structures providing appropriately positioned electrodes within a cathode ray tube are described in relation to the partial cross-sectional diagrams of

FIGS. 8 and 9

.

FIG. 8

is a partial cross-sectional diagram of one half of a cathode ray tube


110


on one side of its central axis


113


about which it is symmetrical. Cathode ray tube


110


has a funnel-shaped glass bulb


140


having a rearward projecting neck


114


in which is mounted electron gun


112


that produces electron beam


130


. The forward end of glass bulb


140


is sealed to glass faceplate


120


to form a container that can be evacuated. A first or neck electrode


144


is formed of a conductive coating surrounding and proximate the juncture of neck


114


, such as a deposited metal electrode pattern, that receives bias potential via conductive feedthrough


145


penetrating the wall of glass bulb


140


.




Electrode


148


having a generally rectangular ring-like shape is supported at its outer periphery or edge by a plurality of glass beads


154


attached to glass sidewall


142


of glass bulb


140


. Glass beads


154


also electrically insulate electrode


148


from conductive coating


152


on the inner surface of sidewall


142


, which coating is at screen potential. The other end of electrode


148


is attached to the inner surface of glass bulb


140


more proximate to neck


114


so that it is in electrical contact with conductive coating


144


to receive neck bias potential therefrom. Electron gun


112


includes flexible tabs connected to its ultor electrode that also contact coating


144


to receive neck bias potential therefrom. Preferably electrode


148


is formed of a ferromagnetic material so as to also serve as a magnetic shield within tube


110


to reduce the effect of the earth's magnetic field and other unwanted fields on the deflection of electron beam


130


. Because conductive coating


152


on the inner surface of glass bulb


140


lies behind electrode


148


, electrode


148


electrostatically shields electron beam


130


from the electrostatic field produced by the bias potential on coating


152


. Conductive coatings


144


and


152


are electrically isolated, such as by a physical gap therebetween in the region behind electrode


146


, and are preferably formed of a deposited metal such as aluminum, graphite, carbon or iron oxide.




Intermediate or field -shaping electrode


146


of generally rectangular ring-like shape is preferably made from stamped sheet metal, such as titanium, steel or aluminum. Electrode


146


is spaced apart from the rear wall of glass bulb


140


and is supported by a plurality of support struts


149


attached thereto. One or more of supports


149


is electrically conductive and in contact with feedthrough


147


penetrating the wall of glass bulb


140


to apply the potential on feedthrough


147


as bias potential to intermediate electrode


146


. Field-shaping electrode


146


is biased to provide an electrostatic field that increases the deflection of the electrons of beam


130


further away from central axis


113


in like manner to that described above, thereby having the effect of a yoke amplifier


150


. Other supports (not visible) of an insulating material support the portions of electrode


146


overlying conductive coating


144


and are located behind electrode


146


so as to be shielded thereby against charging.




Faceplate


120


has a shadow mask


124


spaced slightly apart therefrom and attached to faceplate near their respective peripheries by shadow mask mounting frame


126


. Shadow mask


124


has a pattern of apertures through which electron beam


130


passes to impinge upon a pattern of color phosphors (not visible) deposited on the inner surface of faceplate


120


to produce light to reproduce an image or information on faceplate


120


that is visible to a viewer looking thereat. Conductive coating


122


on the inner surface of faceplate


120


is electrically coupled to shadow mask


124


at shadow mask mounting frame


126


and to conductive coating


152


from which conductive coating


122


and shadow mask


124


receive bias potential. Conductive coating


152


, such as a deposited metal coating, receives bias potential via feedthrough


151


penetrating the glass wall of bulb


140


. Shadow mask frame


126


is shaped, such as by having one or more conductive projections, to provide an electrostatic shield for each of glass beads


154


to avoid charging of beads


154


. Alternatively, a separate shield for beads


154


can be employed, and can be attached to mask frame


126


.




A coating of phosphorescent material


123


is disposed on faceplate


120


for producing light in response to the beam of electrons


130


impinging thereon, thereby providing a monochromatic display, or a pattern of different phosphorescent materials


123


is disposed thereon for producing different colors of light in response to the beams of electrons


130


impinging thereon through apertures in shadow mask


124


, thereby providing a color display.




Desirably, field-shaping electrode


146


is positioned and shaped so that when biased as described above, in cooperation with the bias potentials applied to neck electrode


144


, magnetic shielding electrode


148


, shadow mask


124


and screen electrode


122


, the shaped electrostatic fields produced thereby increase the deflection of electrons in electron beam


130


beyond that obtained from a magnetic deflection yoke (not visible).




In addition, an evaporable getter material


156


, such as a barium getter material, may be mounted to the back surface of electrode


148


and/or the inner surface of glass bulb


140


in the space therebetween from where it is evaporated onto the back surfaces of electrodes


148


and/or


146


and/or the inner surface of glass bulb


140


. The getter material


156


is positioned so as to not coat any important insulating elements, e.g., glass beads


154


or the gap isolating conductive coatings


144


and


152


or the insulating supports, if any, for electrode


146


.





FIG. 9A

is a side cross-sectional diagram of cathode ray tube


210


and

FIG. 9B

is a front view diagram of cathode ray tube


210


(with faceplate


220


removed) illustrating an alternative exemplary structure providing appropriately positioned electrodes


244


,


246


,


248


within cathode ray tube


210


in accordance with the invention. Each of the electrodes


244


,


246


,


248


has a generally rectangular ring-like shape of respectively larger dimension to form an array of spaced apart ring electrodes


244


,


246


,


248


symmetrically disposed within the interior of funnel-shaped glass bulb


240


of cathode ray tube


210


. The electrodes are preferably stamped metal, such as steel, of generally rectangular shape with a generally rectangular aperture, and are mounted within glass bulb


240


by a plurality of mounts, such as elongated glass beads


249


, although clips, brackets and other mounting arrangements may be employed.




Assembly is quick and economical where the rectangular metal electrodes


244


,


246


,


248


are substantially simultaneously secured in their respective relative positions in the four glass beads


249


with the glass beads


249


positioned, for example, at four locations such as the 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock (i.e. 0°, 90°,


180


° and 270°) positions as shown, thereby to form a rigid, self-supporting structure. The assembled electrode structure is then inserted, properly positioned and secured within glass bulb


240


, and faceplate


220


is then attached and sealed.




Appropriate electrical connections of predetermined ones of electrodes


244


,


246


,


248


are made to bias potential feedthroughs


290


penetrating the wall of glass bulb


240


. Electrical connections between ones of feedthroughs


290


and predetermined ones of rectangular electrodes


244


,


246


,


248


are made by welding or by snubbers on the electrodes that touch the feedthrough


290


conductors. Feedthroughs


290


need be provided only for the highest and lowest bias potentials because intermediate potentials are obtained by resistive voltage dividers connected to the feedthroughs


290


and appropriate ones of rectangular electrodes


244


,


246


,


248


. High positive potential from feedthrough


290




d


is conducted to screen electrode


222


by deposited conductor


252


and to gun


212


. For example, the following bias potential values could be utilized:

















Feedthrough





Electrode






Potential




Electrode




Potential












212 (gun)




20 kV






290a = 20 kV




244a




20 kV











244b




22 kV











244c




26 kV











246a




28 kV






290b = 30 kV




246b




30 kV











246c




27 kV











248a




24 kV






290c = 18 kV




248b




18 kV











248c




22 kV











248d




26 kV






290d = 30 kV




222 screen




30 kV














Rectangular electrodes


244


,


246


,


248


can be made of a suitable metal to provide magnetic shielding, such as mu-metal, steel, or a nickel-steel alloy, or one or more magnetic shields could be mounted external to glass bulb


240


. Electron gun


212


, faceplate


220


, screen electrode


224


and phosphors


223


are substantially like the corresponding elements described above.





FIG. 10

is a partial cross-sectional diagram of a cathode ray tube


310


showing an alternative mounting arrangement for a set of generally rectangular electrodes


344


,


346


,


348


having generally rectangular apertures mounted within the interior of funnel-shaped glass bulb


340


to deflect electron beam


330


as described above. Electron gun


312


, neck


314


, faceplate


320


, phosphors


323


, shadow mask


324


and frame


326


, glass bulb


340


are disposed symmetrically relative to centerline


313


, and may include a getter material in the space between glass bulb


340


and electrodes


344


,


346


,


348


, all of the foregoing being substantially as described above.




Electrodes


344


,


346


,


348


are formed as a set of generally rectangular loops of ascending dimension and are positioned symmetrically with respect to tube central axis


313


with the smallest proximate neck


314


and the largest proximate faceplate


320


. Plural support structures


360


are employed to support electrodes


344


,


346


,


348


, such as four supports


360


disposed 90° apart, only one of which is visible in FIG.


10


. Each support structure


360


is generally shaped to follow the shape of glass bulb


340


and is mounted between and attached to two insulating supports


349


, such as glass beads or lips, one proximate shadow mask frame


326


and one proximate neck


314


. Each of electrodes


344


,


346


,


348


is electrically isolated from the other ones thereof, unless it is desired that two or more of electrodes


344


,


346


,


348


be at the same bias potential. Electrodes


344


,


346


,


348


are preferably of stamped metal, such as titanium, steel or aluminum, and are preferably of a magnetic shielding metal such as mu-metal or a nickel-steel alloy to shield electron beam


330


from unwanted deflection caused by the earth's magnetic field and other unwanted fields.




Each support strip


360


is formed of a layered structure of a metal base


362


, such as a titanium strip, for strength, a ceramic or other insulating material layer


364


on at least one side of the metal base


362


, and spaced weldable contact pads


368


including a weldable metal, such as nickel or nichrome, to which the electrodes


344


,


346


,


348


are welded, as shown in the expanded inset of FIG.


10


. Weldable pads


368


are electrically isolated from each other and from metal base


362


by ceramic layer


364


, so that different bias potentials may be established on each of generally rectangular electrodes


344


,


346


,


348


.




Preferably, one or more of support strips


360


includes a high-resistivity electrical conductor


366


, such as ruthenium oxide, preferably formed in a serpentine pattern on ceramic layer


364


to provide resistors having a high resistance, e.g., on the order of 10° ohms, that together form a resistive voltage divider that apportions the bias potentials applied at feedthroughs


390


to develop the desired bias potential for each one of electrodes


344


,


346


,


348


. A ceramic layer


364


may be placed on one or both sides of metal base strip


362


, and a resistive layer


366


may be formed on either or both of ceramic layers


364


. A portion of one side of an exemplary support structure having serpentine high-resistance resistors


366


between weldable contact pads


368


on ceramic insulating layer


364


is illustrated in FIG.


11


. Electrical connections may be made from selected appropriate ones of contact pads


368


to gun


312


and to screen electrode


322


for applying respective appropriate bias potentials thereto. Support strips


360


are preferably formed of fired laminates of the metal base and ceramic insulating and ceramic circuit layers, such as the low-temperature co-fired ceramic on metal (LTCC-M) process described in U.S. Pat. No. 5,581,876 entitled “Method of Adhering Green Tape To A Metal Substrate With A Bonding Glass.”




Electrodes


344


,


346


,


348


and support strips


360


are assembled together into an assembly having sufficient strength to maintain its shape (owing to the strength of each component thereof) and the assembled electrodes are inserted into the interior of glass bulb


340


to the desired position, and the assembly is held in place by clips or welds (not visible) near the shadow mask frame


326


and support


349


near neck


314


. The assembled structure of electrodes


344


,


346


,


348


and support strips


360


preferably conforms approximately to the interior shape of glass bulb


340


and is slightly spaced away therefrom. However, the structure of electrodes


344


,


346


,


348


and support strips


360


is positioned outside the volume through which electron beam


330


passes at any position in its scan including the extremes of deflection produced by the magnetic deflection yoke (not shown) and the amplified deflection produced by the electrostatic forces resulting from the bias potentials applied to electrodes


344


,


346


. Electrodes


344


,


346


,


348


are preferably shaped so as to shield objects behind them, such as support strips


360


and uncoated areas of the inner surface of glass bulb


340


, and getter materials, from impingement of electrons from electron beam


330


.





FIG. 12

is a partial cross-sectional diagram of an alternative exemplary structure providing appropriately positioned electrodes


446




a


,


446




b


,


448


within a cathode ray tube


410


in accordance with the invention. Faceplate


420


and glass tube bulb


440


are joined together to form an evacuable tube envelope having a neck


414


containing electron gun


412


directing electrons towards screen electrode


422


and phosphors


423


on faceplate


420


., which electrons are deflected up to ±55° from central axis


413


by magnetic deflection yoke


416


. Shadow mask


424


is spaced apart from faceplate


420


supported by shadow mask frame


426


and is biased at the same potential as is screen electrode


422


, e.g., 30 kV.




Neck electrode


444


sprayed or deposited on the interior surface of tube envelope


440


is biased at a potential not exceeding the screen potential, and preferably less than the screen potential, e.g., typically 10-20 kV and typically 15 kV. A plurality of electrostatic deflection electrodes


446




a


,


446




b


,


448


adapted to be biased at different potentials are spaced away from the wall of tube envelope


440


supported on support member


460


to which they are attached by respective welds


468


. A high positive potential, e.g., 35 kV, is applied via feedthrough


447


and electrically-conductive support


445


to electrode


446




a


for increasing the deflection of electrons highly deflected by deflection yoke


416


. Support member


460


includes a voltage divider as described above to develop different bias potentials for electrodes


446




b


and


448


. Electrode


448


is typically biased to a potential less than the screen potential, e.g., 0 -20 kV and typically 10 kV, while electrode


446




b


may be biased to either the potential of electrode


446




a


or that of electrode


448


, e.g., 35 kV and 10 kV, respectively. A getter material


456


is positioned at convenient locations behind electrodes


446




a


,


446




b


,


448


and support


460


. Preferably electrode


448


is biased at a low positive voltage with respect to screen electrode so as to decrease the landing angle of electrons coming under the influence of the electric field produced by the bias potential thereon.





FIG. 13

is a cross-sectional diagram of a further alternative exemplary structure providing appropriately positioned electrodes


544


,


546


,


548


within a display tube


510


in accordance with the invention. In particular, tube


510


is an exemplary 757-mm (about 32-inch) diagonal 16:9 aspect format cathode ray tube having a viewable area of 660 mm (about 26 inch) width and 371 mm (about 14.6 inches) height. As a result of the reduction in tube depth attainable with the present invention, tube


510


has a depth D of about 280 mm (about 11 inches).




As before, tube


510


includes a tube envelope formed by joining faceplate


520


and tube envelope


540


. Electron gun


512


in tube neck


514


directs a beam of electrons toward faceplate


520


, screen electrode and phosphors


523


, through apertures in shadow mask


524


, subject to deflection over ±55° responsive to yoke


516


. Yoke


516


may be a 110° or a 125° saddle-saddle type yoke including of a horizontal coil, a vertical coil, a ferrite core and a pair of permeable metal shunts for shaping vertical deflection for self convergence. With the larger deflection-angle 125° yoke, the diameter of tube neck


514


may be reduced, thereby to allow a smaller yoke


516


that requires a lower drive power.




Cathode ray tube


510


employs a combination of electrodes including conductive coatings on tube enclosure


540


and metal electrodes supported within tube envelope


540


. Neck electrode


544


surrounding the outlet of electron gun


512


and tube neck


514


is formed of a conductive coating on the wall of tube envelope


540


and is biased at a bias potential that does not exceed the screen bias potential and is applied via feedthrough


545


penetrating the wall of tube envelope


540


. The low bias potential of neck electrode


544


, e.g., 10-20 kV and typically about 15 kV, tends to slow the electrons down thereby increasing the effectiveness of magnetic deflection yoke


516


. Deflection enhancing electrode


546


surrounds neck electrode


544


, is formed of a conductive coating and is biased at a bias potential that exceeds the screen potential and is applied via feedthrough


547


penetrating the wall of tube envelope


540


. Thus, the bias potential applied to deflection enhancing electrode


546


, e.g., 35 kV, produces an electric field that acts on the electrons of the electron beam after substantially all of the deflection thereof by yoke


516


is accomplished to increase the deflection of the electron beam from electron gun


512


beyond that provided by deflection yoke


516


.




Third electrode


548


is formed of a piece of metal having an “L”-shaped cross-section and is biased at a potential that is applied via feedthroughs


549


penetrating the wall of tube envelope


540


. Electrode


548


is biased at a potential that is less than the screen potential and preferably less than the neck electrode


544


potential, e.g., 0-20 kV and typically about 10 kV, thereby to produce an electric field that directs the electrons reaching the peripheral regions of faceplate


520


towards faceplate


520


, thereby to decrease the landing angle thereof. Because tube


510


is much shorter in the vertical dimension than in the horizontal dimension (illustrated in FIG.


13


), electrode


548


need not be rectangular as described above so as to act on electrons directed toward the top and bottom edges of the viewable area of faceplate


520


, but may be two straight L-shaped metal electrodes


548




a


,


548




b


receiving bias potential via feedthroughs


549




a


,


549




b


, respectively, to act only on those electrons directed towards the left and right vertical edges of tube


510


. Electrodes


548




a


,


548




b


are attached to feedthroughs


549




a


,


549




b


, respectively for physical support, such as by a weld or a glass to metal attachment, e.g., a conductive glass frit material.




Shadow mask


524


is supported by shadow mask frame


526


and receives screen electrode


522


bias potential via feedthrough


525


penetrating the wall of tube envelope


540


. Screen potential is, e.g., 30 kV. Getter material


556


is placed at convenient locations, such as behind shadow mask frame


526


and electrode


548




a


,


548




b.






In any of the foregoing embodiments, where a conductive coating or electrode is on the surface of the tube envelope, such as a faceplate


20


,


120


,


220


,


320


,


420


and so forth, such coating or electrode is preferably a sprayed, sublimated, spin coated or other deposition or application of graphite or carbon-based materials, aluminum or aluminum oxide or other suitable conductive material. Where electrodes, such as electrodes


46




a


-


46




f


,


146


,


148


,


244




a


-


244




c


,


246




a


-


246




c


,


248




a


-


248




d


,


344




a


. . .


348




c


, and so forth, are spaced away from the wall of tube envelope


40


,


140


,


240


,


340


,


440


and so forth, such electrodes are preferably formed of a suitable metal such as a titanium, Invar alloy, steel, stainless steel, or other suitable metal.




While the present invention has been described in terms of the foregoing exemplary embodiments, variations within the scope and spirit of the present invention as defined by the claims following will be apparent to those skilled in the art. For example, the present cathode ray tube can be a monochrome tube having a phosphor coating on the inner surface of the faceplate thereof or may be a color tube having a pattern of color phosphors thereon and a shadow mask having a pattern of apertures corresponding to the pattern of color phosphors, whether described herein as having or not having a shadow mask. Where a higher efficiency shadow mask is available, such as a shadow mask that enables a larger proportion of the electrons of electron beam to pass through the apertures thereof, such high-efficiency shadow mask could be employed in cathode ray tubes of the present invention, thereby resulting in one or more of increased brightness, reduced spot size or reduced gun diameter (and the benefit of increased deflection angle or reduced yoke power associated therewith).




Bias potentials developed by voltage dividers may be developed by resistive voltage dividers formed of discrete resistors, blocks of high-resistivity material, coatings of high-resistivity material and other suitable voltage dividers. While the bias potential applied to the peripheral electrode


48


,


148


,


248


is preferably less than the screen potential, it may be equal thereto, may be less than the bias potential of neck electrode


44


,


144


,


244


, and may even be at zero or ground potential or negative.



Claims
  • 1. A tube comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, wherein said faceplate is substantially rectangular having two longer edges and two shorter edges, and having a screen electrode on the faceplate for biasing at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck and is adapted for magnetic deflection of said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; at least first and second electrodes on an interior surface of the funnel portion of said tube envelope, each said electrodes defining a respective aperture through which the at least one beam of electrons passes, wherein said first electrode is proximal said source and distal said faceplate and is for biasing at a potential less than the screen potential, and wherein said second electrode is between said first electrode and said faceplate and is for biasing at a potential not less than the screen potential; and a third electrode comprising two formed metal electrodes mounted to said tube envelope and between which the at least one beam of electrons passes, wherein one of said formed metal electrodes is proximal each of the two shorter sides of said faceplate between said second electrode and said faceplate and is for biasing at a potential not exceeding the screen potential.
  • 2. The tube of claim 1 wherein at least one of said first and second electrodes includes a conductive material deposited on the interior surface of the funnel portion of said tube envelope.
  • 3. The tube of claim 1 wherein the apertures defined by said first and second electrodes are substantially rectangular.
  • 4. The tube of claim 1 wherein said third electrode is biased at a potential less than the potential at which said first electrode is biased.
  • 5. The tube of claim 1 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials on said faceplate that emit different color light in response to the at least one beam of electrons impinging thereon through the apertures of said shadow mask.
  • 6. The tube of claim 1 wherein at least one of said first and second electrodes includes a plurality of sub-electrodes adapted to be biased at different potentials.
  • 7. The tube of claim 6 wherein said plurality of sub-electrodes are mounted to a plurality of supports attached to the interior of the funnel portion of said tube envelope and at least one of said sub-electrodes is electrically connected to a conductor penetrating said tube envelope.
  • 8. The tube of claim 7 further comprising a resistive voltage divider on at least one of said supports and adapted for receiving a bias potential for developing at least one of the potentials at which at least one of said first, second and screen electrodes are adapted to be biased.
  • 9. A tube comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, and having a screen electrode on the faceplate adapted to be biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck and is adapted for magnetic deflection of said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby.
  • 10. The tube of claim 9 wherein said resistive voltage divider is electrically connected to at least one of a conductor penetrating said tube envelope and said screen.
  • 11. The tube of claim 9 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials on said faceplate that emit different color light in response to the at least one beam of electrons impinging thereon through the apertures of said shadow mask.
  • 12. A tube comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, and having a screen electrode on the faceplate adapted to be biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck and is adapted for magnetic deflection of said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby, wherein said supports comprise a metal layer and a ceramic layer on said metal layer, wherein said first and second electrodes attach to said ceramic layer.
  • 13. A tube comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, and having a screen electrode on the faceplate adapted to be biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck and is adapted for magnetic deflection of said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby, wherein said at least one support comprises a metal layer and a ceramic layer oil said metal layer, wherein said resistive voltage divider includes a high-resistivity material on said ceramic layer, and wherein said first and second electrodes electrically connect to said high-resistivity material on said ceramic layer.
  • 14. A display comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, wherein said faceplate is substantially rectangular having two longer edges and two shorter edges, and having a screen electrode on the faceplate biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck; a magnetic deflection yoke proximate said source of at least one beam of electrons for magnetically deflecting said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; at least first and second electrodes on an interior surface of the funnel portion of said tube envelope, each said electrodes defining a respective aperture through which the at least one beam of electrons passes, wherein said first electrode is proximal said source and distal said faceplate and is biased at a potential less than the screen potential, and wherein said second electrode is between said first electrode and said faceplate and is biased at a potential not less than the screen potential; a third electrode comprising two formed metal electrodes mounted to said tube envelope and between which the at least one beam of electrons passes, wherein said third electrode is between said second electrode and said faceplate and is biased at a potential not exceeding the screen potential and wherein one of said formed metal electrodes is proximal each of the two shorter sides of said faceplate; and a source of bias potential for said first, second, third and screen electrodes.
  • 15. The display of claim 14 herein at least one of said first and second electrodes includes a conductive material deposited on the interior surface of the funnel portion of said tube envelope.
  • 16. The display of claim 14 wherein said third electrode is biased at a potential less than the potential at which said first electrode is biased.
  • 17. The display of claim 1 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials on said faceplate that emit different color light in response to the at least one beam of electrons impinging thereon through the apertures of said shadow mask.
  • 18. The display of claim 14 wherein at least one of said first and second electrodes includes a plurality of sub-electrodes mounted to a plurality of supports attached to the interior of the funnel portion of said tube envelope and biased by said source of bias potential at different potentials.
  • 19. The display of claim 18 wherein said source of bias potential comprises a resistive voltage divider on at least one of said supports and receiving a potential for developing at least one of the potentials at which at least one of said sub-electrodes are biased.
  • 20. A display comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, and having a screen electrode on the faceplate biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck; a magnetic deflection yoke proximate said source of at least one beam of electrons for magnetically deflecting said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; a source of bias potential including the screen potential; a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon coupled to said source of bias potential for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby.
  • 21. The display of claim 20 wherein said resistive voltage divider is electrically connected to at least one of a conductor penetrating said tube envelope and said screen.
  • 22. The display of claim 20 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials on said faceplate that emit different color light in response to the at least one beam of electrons impinging thereon through the apertures of said shadow mask.
  • 23. A display comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, and having a screen electrode on the faceplate biased at a screen potential; a source of at least one beam of electrons directed toward said faceplate, wherein said source is in said tube neck; a magnetic deflection yoke proximate said source of at least one beam of electrons for magnetically deflecting said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; a source of bias potential including the screen potential; a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon coupled to said source of bias potential for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby, wherein said supports comprise a metal layer and a ceramic layer on said metal layer, and wherein at least one of said supports includes said resistive voltage divider comprising a high-resistivity material on said ceramic layer, and wherein said first and second electrodes electrically connect to said high-resistivity material on said ceramic layer.
  • 24. A cathode ray tube comprising:a tube envelope having a funnel portion, generally flat faceplate and a screen electrode on the faceplate adapted to be biased at a screen potential, and having a tube neck opposite said faceplate; in said tube neck, a source of at least one beam of electrons directed toward said faceplate, wherein said source is adapted for magnetic deflection of said at least one beam of electrons; a deflection yoke around said tube neck for deflecting the at least one beam of electrons from said source over a predetermined range of deflection angles, whereby the deflected at least one beam of electrons impinge upon a given area of the screen electrode; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; and at least first and second electrodes on an interior surface of the funnel portion of said tube envelope, each of said electrodes defining a respective aperture through which the at least one beam of electrons passes, wherein said first electrode is proximal said source and distal said faceplate and is adapted to be biased at a potential less than the screen potential, and wherein said second electrode is between said first electrode and said faceplate and is adapted to be biased at a potential not less than the screen potential; and a third electrode of formed metal defining an aperture through which the at least one beam of electrons passes, wherein said third electrode is between said second electrode and said faceplate and is adapted to be biased at a potential not exceeding the screen potential, whereby the deflected at least one beam of electrons further deflected by at least said second deflection electrode impinge on an area of said screen electrode that is larger than the given area thereof.
  • 25. The cathode ray tube of claim 24 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at said screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials that emit different respective colors of light in response to said at least one beam of electrons impinging thereon.
  • 26. A cathode ray tube comprising:a tube envelope having a funnel portion, a generally flat faceplate and a screen electrode on the faceplate adapted to be biased at a screen potential, and having a tube neck opposite said faceplate; in said tube neck, a source of at least one beam of electrons directed toward said faceplate, wherein said source is adapted for magnetic deflection of said at least one beam of electrons; a deflection yoke around said tube neck for deflecting the at least one beam of electrons from said source over a predetermined range of deflection angles, whereby the deflected at least one beam of electrons impinge upon a given area of the screen electrode; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; and a plurality of supports attached to the interior of the funnel portion of said tube envelope, at least one of said supports including a resistive voltage divider thereon for providing at least two different potentials; and at least first and second electrodes mounted to said plurality of supports, each said electrode defining a respective aperture through which the at least one beam of electrons passes, wherein said first and second electrodes are connected to said resistive voltage divider for being biased at the two different potentials provided thereby, whereby the deflected at least one beam of electrons further deflected by at least one of said first and second electrodes impinge on an area of said screen electrode that is at least as large as the given area thereof.
  • 27. The cathode ray tube of claim 26 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask adapted to be biased at said screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials that emit different respective colors of light in response to said at least one beam of electrons impinging thereon.
  • 28. The cathode ray tube of claim 26 further comprising an electrically-conductive coating disposed on an interior surface of the funnel portion of said tube envelope at least proximate the tube neck.
  • 29. A cathode ray tube comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, wherein said faceplate is substantially flat and rectangular with two longer edges and two shorter edges, and a screen electrode on the faceplate for biasing at a screen potential; a source of at least one beam of electrons directed toward the screen electrode on said faceplate, wherein said source is in said tube neck and is adapted for magnetic deflection of said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; at least a first electrode comprising a conductive coating on an interior surface of the funnel portion of said tube envelope, said first electrode defining an aperture through which the at least one beam of electrons passes, wherein said first electrode is for biasing at a potential not less than the screen potential; and a second electrode comprising two formed metal electrodes mounted to said tube envelope and between which the at least one beam of electrons passes, wherein one of said formed metal electrodes is proximal each of the two shorter sides of said faceplate between said first electrode and said faceplate and is for biasing at a potential not exceeding the screen potential.
  • 30. The cathode ray tube of claim 29 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, said shadow mask for biasing at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials that emit different respective colors of light in response to said at least one beam of electrons impinging thereon.
  • 31. A display comprising:a tube envelope having a tube neck, a funnel portion and a faceplate, wherein said faceplate is substantially flat and rectangular with two longer edges and two shorter edges, and having a screen electrode on the faceplate biased at a screen potential; a source of at least one beam of electrons directed toward the screen electrode on said faceplate, wherein said source is in said tube neck; a magnetic deflection yoke proximate said source of at least one beam of electrons for magnetically deflecting said at least one beam of electrons; phosphorescent material disposed on said faceplate for producing light in response to the at least one beam of electrons impinging thereon; at least a first electrode comprising a conductive coating on an interior surface of the funnel portion of said tube envelope, said first electrode defining an aperture through which the at least one beam of electrons passes, wherein said first electrode is proximal said source and distal said faceplate and is biased at a potential not less than the screen potential; a second electrode comprising two formed metal electrodes mounted to said tube envelope and between which the at least one beam of electrons passes, wherein said second electrode is between said first electrode and said faceplate and is biased at a potential not exceeding the screen potential and wherein one of said two formed metal electrodes is proximal each of the two shorter sides of said faceplate; and a source of bias potential for said first, second and screen electrodes.
  • 32. The display of claim 31 further comprising a shadow mask proximate said faceplate having a plurality of apertures therethrough, wherein said shadow mask is biased at the screen potential, and wherein said phosphorescent material includes a pattern of different phosphorescent materials that emit different respective colors of light in response to said at least one beam of electrons impinging thereon.
Parent Case Info

This Application is a division of U.S. patent application Ser. No. 09/559,809 filed Apr. 26, 2000 which claims the benefit of U.S. Provisional Applications Serial No. 60/131,919 filed Apr. 30, 1999 and No. 60/160,654 filed Oct. 21, 1999, and further claims the benefit of U.S. Provisional Application Serial No. 60/160,772 filed Oct. 21, 1999.

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Foreign Referenced Citations (5)
Number Date Country
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Provisional Applications (3)
Number Date Country
60/131919 Apr 1999 US
60/160654 Oct 1999 US
60/160772 Oct 1999 US