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Патент USA US3043985

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July 10, 1962
Filed Aug. 5, 1957
4 Sheets-Sheet 1
July 10, 1962
Filed Aug. 5, 1957
4 Sheets-Sheet 2
Cu mm Urn
July 10, 1962
Filed Aug. 5, 1957
4 Sheets-Sheet 3
H6. 5.
July 10, 1962
Filed Aug. 5, 195'?
4 Sheets-Sheet 4
' F \G.7.
GLEN A.'suR-mc\<
United States Patent ice
Patented July 10, 1962
, 2
tern has a prescribed relationship relative to the distance
' between the center of the associated spot pattern and ad
joining spot patterns. An exposure device and manufac
Glen A. Burdick, Waterloo, N.Y., assignor, by mesne a_s
turing process are providedto produce a screen having a
plurality of discrete display areas‘, the location of each
discrete area being positioned in a prescribed relationship
to the impinging beam positions vfora given de?ection
' s'ignments, to Sylvania Electric Products Inc., Wil
ming'ton, Del., a corporation of. Delaware
Filed Aug. 5, 1957, Ser. No. 676,331
2 Claims. (Cl. 313-92)
For a better understanding of the-invention, reference
This invention relates to image display devices and
more particularly to cathode ray tubes of the type adapted 10 is made to the following description, taken in conjunction
with the accompanying drawings in which:
to be employed in color television apparatus.
FIG. 1 is a plan view of a typical cathode ray tube
One of the chief problems encountered in the produc
adapted for the reproduction of color images; '
tion of screens for image display color tubes such as those
FIG. 2 illustrates the manner in which the electron
used in television apparatus involves “matching” of the
light optics employed in the screen forming process with 15 beams are dynamically converged in the-tube; .
FIG. 3 shows a portion of an image-display structure
the electron optics existent in the ?nished tube. Unless
the discrete image display elements on the screen are posi- ' illustrating one embodiment ofthe invention;
1 ‘FIG. '4 illustrates the spatial relationship between beam
tioned so that the scanning electron beam or beams will
correctly register therewith, an impure or otherwise un
acceptable color image will result.
Some of these reg
impinging spot patterns formed in accordancexwith one
aspect of the invention;
FIG. 5 shows a portion of acathode ray tube screen;
. FIG. 6 illustrates the optical system employed in the
istration problems and their solutions, along with light
optical structures and processes for forming the screen,
are discussed in detail in the co-pending application, S.N.
screen forming process;
FIG. 7 is an enlarged view of a portion of. the discrete
595,144, entitled “Cathode Ray Tube Structure and Proc
ess,” Glen A. Burdick, which is assigned to the same 25 image display con?gurationsvshowing the beam imping
ing spots located thereon; and
, FIG. 8 illustrates the relationship between the image
assignee as the present invention. This invention is con
cerned in part, with that portion of the registration prob
lem createdby dynamic convergence of the electron beams
employed in the tube.
It is the present practice in television art to use a con
display areas and the electron vbeam impinging positions;
Referring to the drawings, FIG. 1 shows a typical plural
30 beam shadow mask type cathode ray tube. Disposed with
in envelope 11 are three electron emitters 12 positioned
approximately 120° apart to provide three electron‘ beams .
with a multiple beam color tube so that the beams can
13 which may be de?ected by coils 15 over the raster
be moved relative to each other in the de?ection region
area and converged at mask 17 to impingeiupon screen
in’accordance with the de?ection angle and direction of
the beam or beams at a given instant. The mask or grid 35 19. The screen comprises a large number of triads, each
rtriad consisting of, discrete areas or elements of red,
utilized in the tube generally has a spacing from the screen
green and blue color ?uorescing ‘materials which are posi
such that the electron beams will cross one another at the
tioned at the intercepting points‘of', the appropriate one
mask and impinge upon the screen without overlap. This
of the electron beams 13‘ employed in the tube. Although
mask is constructed so that the spacing from the center
of the‘ mask to the screen is less than the spacing between 40 a tri-gun shadow mask tube is shown in FIG. *1, it will
be apparent that the invention described herein is also
these structures along their edges. However, with such a
tinuously varying beam convergence ?eld in conjunction
applicable to other plural beam types of image reproduc
construction, the beam impinging spots for any given
pattern are separated by agreater distance over certain
tion devices.
In order to have the electron beams 13 ‘converge at the
apertures in grid 17 over the entire screen, dynamic con
tain a reasonable semblance of color purity in the tube,
vergence magnets 21 are conventionally employed. Two
the discrete image display elements or areas are so posi
of the three beams used in a shadow mask cathode ray
tioned that at least a small portion of each display area
tube are shown in FIG. 2 to illustrate the dynamic con‘
will cover the associated electron beam impinging spot
on the screen. The image display so produced is not 50 vergence e?ect-s. The static convergence beam paths pass
through points ‘a and b in the de?e'ction‘region and pro’;
uniform in appearance nor does it give good'color uni
lceed toward mask 17 and screen :19 at an angle. to the
formity. Due to the critical design, manufacturing tol
tube axis to converge at point g: ‘When the beams 13
erances are extremely rigid and the tube operational set
are de?ected to some-angle alpha (ix) withoutthe aid'of
up requires a variety of controls and is very costly ‘and
areas of the screen than over other areas. In order to ob
65 dynamic convergence ?elds supplied by-coils 21, the beams
appear to ‘originate from- p'oints a" and b’ and intersect at
point c. ‘This situation is highly‘ unsatisfactory. In prac@
tice, the coils 21 provide'rna-gnetic' ?elds which move
tirnum display area with good electron beam registration, .
improved color uniformity, and a uniform'appearing - the beams 13‘ radially outward inlthede?ection region to
time consuming.
Accordingly, an object of. this invention is to reduce
the aforementioned disadvantages and to-provide an op
screen for an image display device.
A further object is to reduce the necessityv for critical
control of manufacturing tolerances in the fabrication of
60 cause beams 13 to appear to come fromzpoints' e and f
to provide the desired convergence at point gf ‘within an
aperture in mask 17. The points ve and f designate posi
image displays and to increase the operational set-up e?i
tions which-are approximately on‘the locus of motion of
ciency for such devices.
the apparent center of de?ection for each beam 13 as more
Another object is to fabricate improved image display 65 fully described in the above mentioned Burdick applica
screens and tubes.
It has been the practice to use a mask' 17 which has a
The foregoing objects are achieved in one aspect of
the invention by the provision of an image display tube
spacing dllat the center/of the mask betweenjthe mask
and screen 19 which is less than the‘ spacing d; at the
in which the electron beam impinging spot pattern asso
ciated with a given image display pattern is such that 70 edge of the mask. This construction, in conjunction with
the average distance between the center of a given beam
impingingspot and the center of the associated spot pat
dynamic convergence,'may produce an electron beam and
?uorescent dot registration of the type shown in FIG. '2'
' displaced from the screen. The electron beams 13' may
be separated by a considerable distance at the edges of
less than the radial dimension, it is used as a basis for the
the screen,_as shown, or they may be separated or pulled
triad pattern should “?t” into the smallest beam triad
pattern so that there will not be an overlap of phosphor
entire mask toward'orraway from the screen in a manner
well understood inthe art. In any event, a tube having
this'type of structure produces a-beam pattern» which
dots on the screen.
beam spot and phosphor dot patterns. The phosphor dot
together at other lpreésele'ctedvpositions vby moving the
FIG. 5 illustrates the derivation of the‘ average beam
spots centers, R, B, G, R’, B’, and G" shown in ,FIG. 4.
has given areas’ wherein the beams are undesirably sep
arated‘ or pulled’ together.- This situationtcauses the
Three locations on screen 19 are indicated at 3 o’clock,
7 o’clock and 11 o’clock for a de?ection angle of 33
beams to impinge upon ther?uorescent dots very close to 10 degrees. The sum of 12 numbers of B-O distances, i.e.
their borderseat those locations on the screen where the
beams.v are adversely affected to the greatest extent.
by. n. is
+ . . .equal
to one-third
+ .
. the
tangential dis
tance between the centers of adjoining triads, e.g. dimen
i In order'to improve the beam landing position pattern
uniformity over the“ screen and the spacing between the
sion O7—O7I.' This relationship exists for all R, B and
beamimpinging positions in a given triad, it has been 15 G beam spots located on each de?ection radius over the
entire screen to provideanimproved beam spot pattern;
found that the mask curvature should‘be such that the
spacing'sl', FIGJ3, along the tube axis or central portion,
It has been found that for a 22 inch 70 degree de?ec-e
tion shadow mask color tube, a spacing s1 equal to .530
inch varying to an edge spacing of 52 of .491 inch pro
structure takesinto account the non-linearity of the ?elds 20 vides the pattern illustrated in FIG. 5. Such a spacing
should be greater than the spacing s2 at the edges or pe
riphe‘ral. portions of the grid 17.‘ This grid or mask
provided‘ by yoke coils 21, the amount of beam displace
mentneededf in the ‘tube for dynamic convergence, and
may be ‘achieved by forming the mask 17 with'a radius
of curvature substantially equal to the 26‘ inch radius used
the geometric con?gurations and spatial relationships of
forlthe screen surface.
Generally, the center of the mask
radius is positioned farther from the screen than the cen-"
the gun electrodes 12, screenI19,‘ etc. Since the grid or
maskl17>and screen 19 are generally curvilinear in form, 25 ter of the screen radius so that even if the ‘mask and
this spacing may be such that the'grid to screen distance
screen have the same or a slightly smaller or larger radi
measured along the electron beam path varies inversely to
us, the peripheral portions of the mask will be- closer'to,
the7distance-between' the apparent source of the electron
the screen than the central portions. ‘7
beams, e.g. points e and f, and the‘ tube axis. To satisfy
An optical exposure device such as that shown in FIG.
thiscondition, the structural relationship between the grid
and ‘screen should be such that their surfaces will inter
30 6 is used to produce an image display screen wherein
the discrete fluorescent dots or areas have maximum cov
erage without overlap, i.e. minimumspace between areas,
A grid to screen spacing of the type shown in FIG. 3 l ; while also providing a maximum border of?uorescent
material around each beam impinging position or spot
will providea unique pattern of'beam spots over'the en
sect-if projected. .
- the screen. ‘To illustrate this pattern, FIG. 4 shows two 35 when thelspot patternis of the type shown in FIG. 5.
Although the above mentioned Burdick application ex-lv
adjoining average triads spaced from one another in a
' tangential direction“ The individual average beam po
sitions in an'average triad at a given de?ection angle rela
'tive tov the center ,ofthe» triad,'and the relationship be- '
tweeniadjoiuing average triads may be expressed‘in terms
plains in detail the method of forming a ?uorescent-screen
by a photo-printing process, it will. be discussed here
briefly.v In this process, a light hardenable photo-sensi
tive material such, as polyvinyl alcohol sensitized with
- ammonium dichromate and an appropriate ?uorescent
ofv distances measured from the triad centers 0 and 0'.
This beam spot pattern is such that for any given triad _. _ material such as the 'red phosphor, zinc phosphate, are de
de?ection angle, the average distance from a given beam
posited on the glass panel 25. Discrete areas of this coat
spot to the center of its associated beam spot triad is ap
ing are then exposed to light rays radiated from a point
proximately one-third the tangential distance between the 45 source light transmitter 27 through the lens 29 and
through‘ apertures in a'negative or grid 17. The areas 23
center of the.‘ associatedtriad and the center of an ad
been used to designate the averagecenters of two groups
of the ‘sensitized-‘coating which are exposed to light be
come hardened and adhere to’ the glass envelope While the
of impinging spots provided by the red, green‘ and blue
unexposed portions arepremoved by a developing ?uid
joining triad. ' In' FIG. 4, the letters R, B and G have > -
chroma modulatedbeams representingall locations on 50 such as deionized water. The above process is then re
peated using the blue and green phosphors, with proper
the screen de?ned by one de?ection angle.‘ For instance,
at ca 331degreede?ectioniangle for triad ‘T, the distance - . oif-setting of the transmitterand lens with each exposure‘
B—'—O is: approximately equal to‘ one-third the tangential
operation to provide the complete image display screen.
distance>'O—,-O’. This ‘relationship is also true for the
Zinc ortho-silicate'is one example-of an acceptable green
‘ R-0 and G-O distances in. triad T in additionto the 55 phosphor‘material while zinc sul?de is at present consid;
ered to be a satisfactory blue phosphor;
' "
shows an optica-lsystem associated with one
' used
Theto tangential
de?ne the relative
distance triadpositions
between beamsince
spotit triads
is a less
beam position‘ ofa multiple beam tube which is capable
constant dimension over jthe*'screen than the radial 'di-‘
of positioning the discrete screen elements 23 at the locai
mension and since it-may-be expressed in terms of a 60 tion where the beams 13 will land by substantially supere
simple relationship. 1 FIGS. 1, 2 .and 3 illustrate the
' imposing‘ in space the locusrof motion of apparent light
manner in which the‘ electron beams are converged at an '
ray origin upon the locus of motion of apparent center
aperture in mask 17 to cross one another and impinge
upon screen 19 to form a triad of beam spots; The rela-'
tive positions of adjoining triads are therefore dependent, 65
in part, upon the relative positions of-the-apertures in
mask 17. ‘It is wellfknown that vthe mask "is stretched ' ;
‘of de?ection} of thelelectron beam. This relationship is
accomplished‘ by cit-setting light source 27 from the tube
non-uniformly in a tangential direction during fabrica
‘utilized in the‘screen forming process is’ located in. space
tion, \with the distance‘ ‘between adjoining maskrapertures
"axis a distance p and ‘elf-setting lens :29 a distance 'r and
an angle beta ( 13) fromthe axis of the transmitter. With
this arrangement, "the locus 32 of apparent light ray origin
at substantially the same position relative to the screen
,decreasingfpro'gressively ‘toward the mask‘ periphery.‘ 70 and mask as is the locus 33 of the electron beam apparent
Consequently, the beam spot triad distances also tend" to
center of de?ection in the operating tube. Although the
decrease in this direction; However, mask stretch‘ does ' light rays 26 originated from the tip of transmitter 27,
not have an appreciable ‘non-uniform, effect upon‘the ra
they appear‘to comerfrom apoint on locus 33, when
dial dimensions between mask apertures or spot triads,‘
viewedfrom' the screen, since they are refracted by the
and, since the tangential distance is usually equal to or 75 plano-concave symmetrical lens 29. The amount of off
that an increase in o?set will allow a reduction in tilt
and vice versa to achieve similar results. In addition,
mask con?guration has been illustrated in FIG. 3 to pro
vide a more symmetrical and uniform beam impinging
spot pattern as illustrated in FIGS. 4 and 5. In addition,
although a symmetrical planoconcave lens is shown, other
types of lens elements could be employed in conjunction
with the correct positioning of transmitter 27 and the
6 is adapted to form a phosphor dot pattern (FIGS. 7
and 8) which registers with the beam spot pattern to
duce the improved phosphor dot pattern for this tube.
port having discrete light emitting areas arranged thereon
‘by the optical system shown in FIG. 6,‘ when it has the
ideal combination of tilt and off-set, that the discrete
spaced from one another radially outwardly from the
center of said curved support and disposed substantially
set and tilt of lens 29 are inter-related in such a manner
a process and exposure device such ‘as that shown in FIG.
provide a highly satisfactory image display.
lens 29 relative to one another and to the mask 17 and
Although several embodiments of the invention have
the axis of the tube to achieve the desired results. For
been shown anddescribed, it will be apparent to those
instance, an asymmetrical and/ or an aspherical lens
could be used in this system with little or no tilt, if de 10 skilled in the art that various changes and modi?cations
may be made therein without departing from the scope
sired. It has been found that for a 22 inch shadow
of the invention as de?ned by the appended claims.
mask tube of the type described above, the application
What is claimed is:
of a 90 millimeter diameter plano-concave lens 29 with
1. A cathode ray tube of the type adapted to employ
a center thickness of .45 centimeter and a radius of curva
ture equal to 23.55 centimeters spaced from transmitter 15 a plurality of dynamically converged electron beams
directed to'be de?ected over and impinge upon an image
27 a distance of 1.875 inches, offset a distance r of .265
display screen, said screen comprising a curvilinear sup
inch and tilted an angle beta (,8) of 3 degrees will pro
to form a plurality of patterns located in radial and tan
Referring to FIG. 7 it can be seen that the discrete
image display phosphor areas or dots 23 are so positioned 20 gential relationships with one another, said patterns being
tangent with one another in a tangential direction extend
areas are substantially tangent in a tangential direction
to provide maximum coverage of the panel 25 in addition ‘
ing normal to the radial direction, said patterns varying
to substantially increasing the uniformity of brightness 25 in spacing from each other in said radial direction to
locate each discrete area substantially coincident with the
and quality of the reproduced image while providing
average location of the center of the impinging beam at
color pattern uniformity with a minimum amount of
color impurity. The relationship between the beam im
pinging spots or positions 13 and the discrete phosphor
each de?ection angle.
2. A cathode ray tube of the type adapted to employ
on the screen located at a given radius from the axis of
display screen, said screen comprising a curvilinear sup
dots 23 on the screen is clearly shown in FIGS. 7 and 8. 30 a plurality of dynamically converged electron beams
‘directed to be de?ected over and impinge upon an image
For any given de?ection angle, i.e. for those positions
port having discrete light emitting areas arranged thereon
form a plurality of triad patterns located in radial and
substantially coincident with the location of the average
centers y of the impinging beam spots \13. The beam 35 tangential relationships with one another, said triad pat
terns being spaced from one another radially outwardly
positions shown by solid lines in FIG. 8 indicate one
from the center of said curved support and disposed sub
location on the screen, e.g. a 36 degree de?ection angle
stantially tangent with one another in a tangential direc
at 3 o’clock. Disposed exactly opposite (in dotted lines)
tion extending normal to the radial direction, the radial
to the positions shown by the solid lines would be the
location of the beam spots ‘13 at a 36 degree de?ection 40 spacing between triad patterns increasing with increased
the screen, the centers as of the areas 23 are positioned
angle and at 6 o’clock. Therefore, it can be seen that the
centers x of discrete phosphor areas 23 are substantially
coincident with the average centers y of the spots 13 at
all locations on a given screen radius or for a given de
?ection angle. Such an arrangement provides improved 45
registration over the entire screen and minimizes the
rescent dots 23 is shown to consist of red, green and blue 50
?uorescing dot triads which are substantially contiguous
in a tangential direction and are separated from one an
other in the radial direction for reasons explained more
fully in conjunction with FIGS. 4 and 5. That is, if a
line is drawn from the center of the screen radially out
with increasing de?ection angle whereas the adjacent
References Cited in the ?le of this patent
possibility of color impurity in the reproduced image.
Referring particularly to FIG. 7, the pattern of ?uo
ward, the successive triads which the line intercepts will
be separated from one another by increasing amounts
radial distance from the center of said screen, said triad
patterns being formed to locate each discrete area sub
stantially coincident with the average location of the cen
ter of the impinging beam at each de?ection angle.
Kallmann ______________ __ Feb. 18,
Van Ormer ___________ _.. May 15,
Morrell ______________ __ June 11,
Epstein ______________ _.. June 11,
Nunan ________________ __ July 30,
Epstein ______________ __ Dec. 24,
Heuer _______________ __ Feb. 11, 1958
Morrell _______________ __ Oct. 7, 1958
Epstein ______________ __ May 12, 1959
triads lying along a line tangent to the radial line will
be substantially contiguous to one another. This type 60 RCA Publication, Recent Improvements in the
of phosphor pattern achieves maximum coverage of face
21AXP22 Color Kinescope, by R. B. J-anes, L. B. Head
plate 25 without overlap.
It is apparent from the foregoing description that a
rick, and J. Evans, printed June 195 6.
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