Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
The present invention relates to cathoc~ ray tubes
and more particularly to triad phosphor array ty~e color
~isplay picture tubes. In general such tubes use an apertured
shadow mask for registering the electron beam wit~ the
phosphor areas. In such tubes, primary color video informa-
tion is carried by electron beams which pass through the
apertures of a shadow mask which is closely spaced from the
tube faceplate. The display is generated by the electron
beam excitation of triad arrays of primary color emissive
phosphors disposed in predetermined positions upon the
interior surface of the tube faceplate.
The manufacturing process for such conventional
color television picture tubes is a multi-step photo-
exposure and deposition process. The display screen is
fabricated on the faceplate which is later joined to the
tube funnel prior to sealing the electron guns in place.
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The display screen of triad array patterns of cathodo-
luminescent phosphors is fabricated by successively exposing
polymerizable coatings upon the faceplate interior, to light
through the apertures of the shadow mask which is mounted in
the faceplate. ~he light is successively positioned at the;~
respective primary color electron beam origins to register
the phosphor areas with the operational electron beam landing
areas. The shadow mask must be ~oined to and removed from
the faceplate during successive photo-exposures, panel -- ;
washing, and deposition steps, and thus the shadow mask must
be tracked with the speciflc faceplate panel during all the
color screen processing steps. In order to produce high
~uality tubes, it is essential that the relatively large
area thin walled mask maintain its shape during the entire
process and that its position relative to the faceplate
panel when mounted in place be the same after successive
mounting and removal operationsO Mounting inaccuracies and
shadow mask damage can result in less than optimum tubes or
scrapping of the tubes during the production process~
The cathodoluminescent phosphor materials used in
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conventional color television soreens are typically inorganic
phosphors whlch are excited to luminescence by the elec~ron
beam. Such inorganic phosphors are generally not ef~i¢ien~l~
excitable by ultraviolet or visible radiations~
Organic fluorescent materials are well known in
the art, and have been used for some time as pigment additiYes
for paints and inks. The organic luminescent materials are
typically excited by ultraviolet or short wavelength visible -
radiation, and can emit in relatively narrow primary color~ ;
emission bands. -2-
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Cathode ray tubes with fiber optic faceplates are
known in the art ~nd are typ~cally used ~or high resolution
specialty displays. In such systems, the phosphor is typi-
cally disposed on the interior slde o~ the fiber optic
~aceplate. In U.S. Patent 3,826,944 is~ued July 30, 1974 to
Kenneth Cooper, assigned to Westinghouse Electric Corporatlon~
a high contrast, high resolution cathode ray tube i~ described
whlch utilizes a cathodoluminescent, ultra-violet emissive
phosphor dlsposed on the interior ~urface o~ a fiber optic ~ace-
plate. An ultraviolet absorptive organic phosphor which emit~~islble light is di~posed on the exterior surface of the ~iber
optic faceplate. The ~nternal phosphor-external phosphor
combination proposed by the aforementloned patent was comblned
with selectively transmissive filter layers to minimize the
reflection of ambient light o~f Or the phosphor layer disposed
on the interior surface of the ~lber optlc faceplate. In
thi~ way, the contrast of the de~ice can be improved by
a~oidlng scattering o~ ambient light in the phosphor material.
As has already been mentioned, the basic ~abrica-
tion process for color televlæion plcture tubes is a photo-
exposure process. It is extremely important that the phosphor
areas on the faceplatc be located or regi~tered with the
ultimate operatlonal electron beam landing area to achieve
good color purlty and rendition. Such per~ect registration
cannot be achieved, slnce light u~ed for photo-exposure
necessarily tra~als ln a straight path, while the operational
electron beam which is deflected and ~ocused electromagnetl_
cally travels in a cur~ed path, me l~ght used in the
photo-exposure process i~ made to simulate the slectron beam
path by complicated and expensive correcting len~es which
rerract the light to approximate the electron beam p~th.
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SUMMARY OF THE INVENTION
:
A color television picture tube of the triad phos-
phor array type in which the color display screen is signifi- -
cantly modified. The picture tube comprises an evacuated,
hermetio~lly sealed vitreous tube envelope having a faceplate
display portion. At least one electron beam generating
electron gun is disposed within the tube envelope for gener-
ating an electron beam of video color signal informationO
Means are provided for re~istering the electron beam with
the desired phosphor area, and generally comprises an aper~
tured shadow mask. The electron beam impinges selected
portions of the faceplate. An electron beam absorptive,
radiation emissive layer is disposed upon the entlre interior
surface of the faceplate portion. Radiation collimating
means are associated with the faceplate. When a specific
primary color video signal electron beam is swept across the
faceplate, the emltted collimated radiatlon impinges a
predetermined primary color area on the exterior surface o~ ~
the faceplate. At least two other primary color emissive ~ -
phosphors are dispose~ on selected portions of the exterior
surface faceplate, which phosphor materials have absorption
bands which encompass the collimated radiation~
BRIEF DESCRIPTION OF THE DRAWINGS -
Figure 1 is an enlarged elevational view partly in ;--
seçtion of a color television picture tube in the embqdiment
of the present invention. -~
Fig. 2 is an enlarged view of a portion of the
faceplate of the picture tube shown in Fig. 1.
Fig. 3 is a partial view of another embodiment
faceplate which utilizes a fiber optic colllmating means.
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Fig. 4 ~s another embodiment in whlch a laser
emission coating is provided on the interior surface face-
plate, as the collimating means.
Fig. 5 is a schematic representation of another
embodiment of the present invention.
Fig. 6 is an enlarged view of the faceplate portion
of the embodiment of Figo 5~
Flg. 7 is an enlarged view of a portion of the
faceplate of yet another embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS ~~
- In the embodiment seen in Fig. 1, color television
- picture tube 10 comprises a neck portion 12, a funnel portion
14, a faceplate portion 16. In this embodiment, 3 in-line
electron guns 17, 18 and 19 disposed within the neck portion
- .. . ~.
12 of the picture tube to provide the respective primary
:,
color video signal in~ormationO An apertured shadow mask 20
is closely spaced from the faceplate portion 16 within the
.
tube. The shadow mask apertures are elongated slots or may be
a grill type aperture mask. An electron beam absorptive radla~
tion emissive layer 22 is disposed across the entire interior
surface of the faceplate portion. A conventional thin ~ -
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aluminum film Z4 is disposed atop the radiation emisslve l~yer
Z2, whieh aluminum film 24 serves as the anode of the tube.
As seen more clearly in Fig~ 2, the faceplate
portion 16 of the tube is formed of a plurality of individual
vitreous thin glass sheets 26 which are laminated together
into a single unitary faceplate member~ The thin sheets
which are laminated together in a plane transverse to the -~-
general plane o~ the faceplate serve as a radiation collimat- ~-
30 ing means. A first primary color emissive phosphor material
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is.disposed in a series of parallel spaced apart stripes 28
on the exterior surface o~ the faceplate~ A second primary
. color emissive phosphor material is likewise disposed in a
plurality o~ parallel stripes 30 disposed on the exterior
surface o~ the faceplate. The externally dlsposed phosphor
-stripes are by way of example about 10 mils wide and the
- . thickness may be widely varied~ In the preferred embodiment
. o~ the invention,.the radiation emissive layer 22 d~sposed
on the interior surface of the faceplate is a blue emitting
cathodoluminescent phosphor which is preferably zinc sulfide ~
activated by silver and chlorine, and ls termed a Pll phos- :
phor. This blue emitting inorganic cathodoluminescent phos-
. phor has a peak emiss.ion at about 4600 Angstroms. In this -
embodiment, the blue-emitting phosphor excites green and red
emitting organic phosphors which are respectively disposed .
as phosphor stripes 28 and 30 on the exterior surface of the
. glass faceplate. The triad array of the three primary
: colors needed to form a balanced display is produced.by :
providing beside the red and the green organlc phosphors on ~ '`J'~
.. 20 the exterior of the. faceplate a clear parallel stripe space .:
. to permit the blue emission of the internally-disposed ph~sphor
to pass through the faceplate and form a stripe of blue
light which is proximate each red and green phosphor stripe.
The blue emitted 11ght of the internally disposed phosphor
excites`the red and green organic phosphors to luminescence.
A suitable green organic phosphor strlpe can be produced by
mixing fluorescent dye pigments trade number 202-18 a product
~ of the Day Glow Company of Cleveland, Ohio with a suitable
. organic binder, such as polyvinyl alcohol and the red phosphor
30 stripe can be produced by mixing red fluorescent dye pigments
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such as number 202-1~, also available from the Day Glow
Company. me peak emission wave lengths of these respective
green and red phosphors are at about 5180 Angstroms and 6120
Angstroms, respectively. me half power bandwidth for each
such organic emitter is approx~mately 400 Angstroms, These
pho~phors, as well as the blue emitting internally disposed
phosphor closely match the colors used in present color
television displays using standard inorganlc phosphors which
are internally disposed. me time constant o~ the organic
phosphors is typically one or two microseconds 80 that per-
sistence i8 not a problem for produclng a clear image. m e
laminated glass sheets 26 which form the faceplats serve to
collimate the blue eml~sion of the internally-disposed phos-
phor, 90 that when the blue video information excites a
speci~ic portion of the internally-disposed phosphor~ the
blue light wlll pass through a clear portion of the faceplate~
W~ile ~or green video in~ormation, the green electron beam
will ~lrst lmpinge the lnternally-disposed blue emitting
phosphor $n an area which is aligned with one of the green
emlttlng organic phosphor~ ~n the external surface of the
~aceplate, Likewise the red organic phosphor i8 activated
in the same way. The laminated sheets of glass maklng up
the faceplate ser~e to pre~ent dlsperslon of the blue emission
in pasOEin@ through the Paceplate.
me organic fluorescent pigments are formed by
di~solvlng an organic dye at a concentration o~ about 0.1 to
2 percent by wei~ht into a sultable resin system such as the
toluene-sulfonamide resins per the teachlng of U,S, Patent
2,938,873 lssued May 1960 to Kazemas. 'rhe resin-dye mix
~0 is dried and ground up to form the finely divided pigment.
m e pigment i8 then deposited
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using c~nventional photo-exposure techniques with a suitable
polymerizable binder and light sensitizer.
The organic phosphors can be selected ~rom a wide
variety of materials. For the red emitting material, members
- of the rhodamine dye family, such as Rhodamine B, Sulforha-
damlne B are examples. Also the oxazine dye family are good
-. red emitters, such as cresyl violet perchlorate and cresyl
. . violet acetate. - - ~ -
It ls also possible to use a mixture of organ~c
dyes to improve the absorption characteristic of the m~xtureO-
~
Thus, a green emitter may be mixed with the red emitter, ~
where the green emitter is more highly exclted by blue ~:
. radiation, and the green emission is absorbed by the red
. emitter and re-radiated to yield a high net red emission~
For green emitting organic materials one can
select a member of the napthalamide dye family, such as
. . Fluoral 7GA, or brillian~ sulfoflanine. Other dye families .-
: whlch include typically good green emitters are the coumarin
dye family3 fluorescein.dye, and rhodamine family~
.. 20 In another embodlment of the invention, an ultra-
violet emissive phosphor material rather than the blue
. emissive material can be disposed upon the interior surface
.. of the faceplate. Such an.ultraviolet emissive phosphor is
. a P16 which is calcium-magnesium-silicate activated by.
. c.er~u~.. In th$s embodiment, a blue organic phosphor stripe
ls also provided on the exterior surfac.e of the faceplate,
and the ultraviolet emission generated at the interior ~.
surface of the ~aceplate is used to pump or activate each o~
the respective prlmary color organic phosphors disposed on
the external surface of the faceplate.
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In another embodiment of the invention, as seen in
Figure 3, the ~aceplate is formed of a fiber optlc collimat-
ing means faceplate 32.
Such fiber optic faceplates are well known in the
art, and comprise a plurality of fused together small
diameter glass rods having a cladding about each rod of
different refractive index glass. Each individual fiber or -
rod 34 acts as a light pipe to collimate the input lighto
The phosphor areas in this embodiment are again phosphor
stripes on the exterlor surface o~ the faceplate activated
by the internally disposed phosphor layer. It is also
possible to provide phosphor dot patterns on the exterior
surface of the fiber optic faceplate. In an embodiment with
phosphor dots the shadow mask would have circular apertures -
as is well known,
In order to eliminate the need for alignment ~ -
between the apertures of the shadow mask with the collimating
means be it an lndividual sheet of the laminated stack of
glass sheets, or the individual fibers of a fiber optic
faceplate, the dimension of the sheet or ~lber should be
small compared to the phosphor area on the external surfaceO
The pho$phor area corresponds generally in areas with the
shad~w mask aperture. For ten mil wide phosphor stripes
each glass sheet of the laminated stack should be about 1-2
mils. The dimenslonal ratio of phosphor area to thickness
of laminated sheets or fiber optic rod diameter is preferred
at about 10 to 1.
The ma~or advantage of the present color picture --
tube is the signi~icant simplification of manufacture. The
tube is essentially fabricated llke a monochrome piçture
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tube with the ultraviolet emissive or blue emissive cathodo-
luminescent phosphor deposited over the entire internal
surface of the faceplate. The shadow mask is inserted and
the electron guns lnserted, and the tube hermetically sealed,
The external phosphor areas are defined by applying first a
coating over the external surface of the faceplate, which
coating contains a photosensitive mixture of primary color
emissive organic phosphor and a suitable photopolymerizable -
material such as polyvinyl alcohol. The primary color
1~ electron gun is operated to direct a scanning electron beam
which passes through the apertures o~ the shadow mask to
excite the internally disposed cathodoluminescent phosphor
~he emission ~rom this phosphor is collimated in passlng
through the faceplate and Polymerizes the desired phosphor
pattern on the exterior surface of the faceplate. The non~
exposed, unpolymerized portions of the coating can be washed
off and the operation repeated until all the primary color
external phosphors are provided.
Slnce the operational electron beam is used to
define the phosphor areas, the beam registratlon with the
phosphor areas is perfect, which produces an improved white
field purity and general hlgh quality color performance~
In yet another embodiment as seen in Fig, 4, a
conventional glass faceplate 40 can be used with the collimat- -
ing means comprising a thin film of material 42 on the
internal surface of the faceplate which produces coherent
blue laser emission when excited by high energy electron
excitation. A thin film of zinc selenide may be used as the
laser material. A thin aluminum electrode layer 44 is
disposed over the laser material~ The phosphor triads are
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then disposed on the exterior surface of the faceplate 40 as
explained with respect to Flg. 2.
Yet another embodiment of the present invention is
illustrated in Figs. 5 and 6. In this embodiment the colli~
mating means comprises a novel tube facepiate. In contrast
to the standard thick glass faceplate, or the fiber optic
faceplate of Fig. 3~ the faceplate in Flg. 5 is formed like
a honeycomb structure. A plurality of small diameter hollow
light pipes 50 are disposed between a curved glass interior
wall 52, and a matching curved glass exterior wall 54 The
hollow light pipes 50 ~unction to collimate the light gene- ~-
rated by the internally disposed pumping phosphor 56 which -~
is dlsposed on the-interior of interior wall 52. The llght
pipes also structurally support and strengthen the interior
~all 53 and the exterior wall 54 to permit the faceplate
structure to wlthstand the significant force of atmospher~c
pressure pre'sent on the exterior surface ol the faceplate, '
with the tube interior being evacuated to a very low pressure.
~he external phosphor stripes-58~ 60 are disposed on the
exterior surface of exterior wall 54.
The hollow light pipes 50 may be metal or insulator
such as glass. This structure avoids the problem o~ a ~iber
optic ~aceplate where it is dif~icult to avoid vacuum leaks
.
and is not as costly. The faceplate structure is also much
lighter 'than a fiber optic '~aceplate or the present conven-
' tlonal thick glass ~aceplate.
In yet another embodiment, seen in Fig. 7 the
faceplate structure is further modified. In this embodiment
.
the faceplate is ~ormed of a thin inner wall laminated sheet
30 62 comparable to Iaminated sheet 16 of Fig. 2 except much - '-
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thinner. An outer glass faceplate 64 is spaced from the
inner wall laminated sheet 62 and the space between them is
partially evacuated. The internal pumping phosphor layer 66
is disposed on the interior sur~ace of inner wall 62, and
the phosphor stripes 68, 70 are disposed on the exterior
sur~ace of inner wall 62. The laminated structure of inner
wall 62 serves as the collimating means, and the display `~
image is formed on the exterior surface of inner wall 62.
The outer glass faceplate 64 provides the structural inte-
grity to withstand the pressure difference between atmos~ ~``; `
pherlc pressure and the tube interior. This structure does
not requlre as thick a laminated faceplate sheet as in the
- Fig, 2 embodiment. The spacing between the inner wall 62
and outer wall 64 should be minimized for display clarity~
It is apparent that in each of the embodiments of
- the invention the contrast o~ the display can be enhanced by
the provision o~ an opaque matrix material between the indi-
vidual color phosphor elements. The externally disposed
phosphor elements also need not be continuous stripes, but
; 20 can be any triad phosphor array pattern including phosphor
dots or rectangles.
The present invention also has application to beam
indexing color picture tubes which make use of triad phosphor
areas ~or the display. Such indexing tubes are well known
,
and dispense with the apertured shadow mask.
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