CA1060078A - Color television tube with phosphors on exterior surface of faceplate - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A color television picture tube of the triad phosphor array type in which a single layer of cathodo-luminescent absorptive radiation emissive material is disposed on the interior surface of the tube faceplate. Radiation collimating means are associated with the tube faceplate, and at least two different primary color emissive materials are disposed on the exterior surface of the faceplate. The exterior disposed primary color emissive materials are absorptive of the radiation emitted by the internally-disposed material and excited to emission thereby.

Description

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.

46, 119 ~60078 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 .,~ - .
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-' "

106(~078 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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46~119 106~)78 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.

46,119 f 106~)078 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 ~ -. . ~ .
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 ~ ' ' .
, '.
... .. , .~ .

46,].19 ~ ` .
' 106~)078 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 --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 46,119 1060~78 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.
. . . -8-~ ' ,' .

46,119 `~ 1061)078 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 _g_ .

46, 119 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 ..... ,., ..... . ., . .. , . . - . .. . .

46,119 t~ ~:

10~i0078 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 - '-'' ' - ` ' ~ '~

''' ' , .

46,119 , :

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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Claims (22)

CLAIMS:

1. A color television picture tube of the triad phosphor array type where the color display is produced by mixing primary color outputs from three adjacent primary color phosphor areas comprising an evacuated, hermetically sealed vitreous tube envelope having a faceplate display portion, with at least one electron beam generating electron gun disposed within said envelope for directing an electron beam of video color signal information upon the faceplate display portion, means for registering the electron beam with the primary color phosphor areas, and wherein a cathodo-luminescent phosphor layer is disposed upon the interior surface of the faceplate display portion, radiation collimat-ing means are associated with the faceplate so that when a specific primary color video signal is swept across said faceplate the emitted collimated radiation from the cathodo-luminescent phosphor layer is directed to a predetermined primary color area on the exterior surface of the faceplate, and wherein at least two other primary color emissive organic phosphor materials are disposed on the exterior surface of the faceplate, which organic phosphor materials have absorp-tion bands which overlap the emission from the cathodo-luminescent phosphor.

2. The color television picture tube specified in claim 1, wherein the organic phosphor materials are arrayed on the faceplate exterior surface such that a triad array of the three primary colors is regularly produced across the faceplate area.

3. The color television picture tube specified in claim 1, wherein the cathodoluminescent phosphorus ultraviolet emissive and three primary color organic phosphors are disposed upon the faceplate exterior surface in triad array patterns.

4. The color television picture tube specified in claim 3, wherein the ultraviolet emissive cathodoluminescent phosphor is 2 CaO - SiO2 - MgO:Ce.

5. The color television picture tube specified in claim 3, wherein the cathodoluminescent phosphor emission is one of the primary colors, and the other two primary colors are provided by primary color organic phosphors disposed upon the faceplate exterior surface in an array pattern such that a triad array of the three primary colors is regularly produced across the faceplate area.

6. The color television picture tube specified in claim 5, wherein the cathodoluminescent phosphor is a blue emitting phosphor, and the exteriorly disposed organic phos-phors are green and red emitters respectively.

7. The color television picture tube specified in claim 6, wherein the blue emissive cathodoluminescent phos-phor is zinc sulfide activated by silver and chlorine.

8. The color television picture tube specified in claim 1, wherein the collimating means comprises a fiber optic faceplate.

9. The color television picture tube specified in claim 8, wherein the area of the individual fiber optic element is substantially less than the electron beam area.

10. The color television picture tube specified in claim 1, wherein the collimating means comprises a face-plate formed of laminated together sheets of vitreous light transmissive material which are aligned transverse to the plane of the faceplate.

11. The color television picture tube specified in claim 10, wherein the width of the laminated sheets is less than the electron beam diameter.

12. The color television picture tube specified in claim 11, wherein the ratio of phosphor area to thickness of laminated sheets is about 10:1.

13. The color television picture tube specified in claim 11, wherein a slot-type aperture mask with elongated generally rectangular apertures is closely spaced from the interior of the faceplate for registering the electron beam with individual and phosphor areas, and the collimating means comprises a faceplate formed of laminated together sheets of vitreous material which are aligned transverse to the plane of the faceplate and with the elongated apertures, and wherein the width ratio of the elongated apertures to the width of an individual laminated vitreous sheet is about 10:1.

14. The color television picture tube specified in claim 1, wherein the means for registering the electron beam includes an apertured shadow mask.

15. The color television picture tube specified in claim 1, wherein the faceplate comprises an inner and outer wall portion with small diameter hollow light pipes extending the inner and outer wall portions as the radiation collimating means, with the cathodoluminescent phosphor disposed on the interior surface of the inner wall, and the other primary color emissive organic phosphor materials are disposed on the exterior surface of the outer wall portion.

16. The color television picture tube specified in claim 1, wherein the faceplate comprises a thin inner wall of laminated together section of vitreous, light trans-missive material which are aligned transverse to the plane of the faceplate and the cathodoluminescent phosphor is disposed on the interior surface of the inner wall, and wherein the other primary color emissive organic phosphor materials are disposed on the exterior surface of the inner wall, and wherein a thick outer wall portion is spaced from the inner wall with the space therebetween being evacuated.

17. The color television picture tube specified in claim 1, wherein the cathodoluminescent phosphor layer is disposed as a uniform layer on the interior surface of the faceplate, and wherein the primary color emissive organic phosphor materials are disposed as continuous stripes on the faceplate exterior.

18. A color display tube of the triad phosphor array type comprising an evacuated, hermetically sealed vitreous tube envelope having a faceplate display portion, at least one electron beam generating electron gun disposed within said envelope for generating an electron beam of video color signal information, means for registering the electron beam with the individual phosphor areas of the phosphor array pattern, with an electron beam absorptive radiation emissive layer disposed upon the interior surface of the faceplate portion, radiation collimating means asso-ciated with the faceplate so that when a specific primary color video signal electron beam is swept across the face-plate the emitted collimated radiation impinges a predeter-mined primary color area on the exterior surface of the faceplate, and wherein at least two other primary color emissive phosphor materials are disposed on selected portions of the exterior surface of the faceplate, which phosphor materials have absorption bands which encompass the colli-mated radiation.

19. The color display tube specified in claim 18, wherein the interiorly disposed radiation emissive layer is a cathodoluminescent inorganic phosphor, and the externally disposed phosphors are organic phosphors.

20. The color display tube specified in claim 18, wherein the interiorly disposed radiation emissive layer is a cathodoluminescent phosphor which emits blue light, and the externally disposed Phosphors are green and red emitting organic phosphors.

21. The color display picture tube specified in claim 18, wherein an apertured shadow mask is closely spaced from the faceplate portion as means for registering the electron beam with individual phosphor areas.

22. The color display tube specified in claim 18, wherein the electron beam absorptive radiation emissive layer is a laser emission coating on the interior surface of the faceplate, which laser emission coating also serves as the collimating means.