US3904502A - Method of fabricating a color display screen employing a plurality of layers of phosphors - Google Patents

Method of fabricating a color display screen employing a plurality of layers of phosphors Download PDF

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Publication number
US3904502A
US3904502A US337966A US33796673A US3904502A US 3904502 A US3904502 A US 3904502A US 337966 A US337966 A US 337966A US 33796673 A US33796673 A US 33796673A US 3904502 A US3904502 A US 3904502A
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Prior art keywords
phosphor layer
phosphor
color
layer
layers
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US337966A
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English (en)
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Donald M Phillips
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Priority to US337966A priority Critical patent/US3904502A/en
Priority to JP49019556A priority patent/JPS49121473A/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/26—Luminescent screens with superimposed luminescent layers

Definitions

  • This invention is related to the method of fabricating a color display screen and more particularly to such a screen of the type which produces light of different colors in response to impinging electrons of different energies.
  • Most of the state of the art type of devices utilize a two layer voltage dependent screen which consists of a front phosphor screen, an electron barrier layer, and a second phosphor screen.
  • the barrier layer acts as a buffer zone for blocking low voltage electrons thus preventing electron beam excitation of the front screen during the low voltage operation of the tube, while at the same time permitting light from the rear screen to pass through both the buffer layer and the front screen.
  • This barrier layer may be composed of silicon monoxide or magnesium oxide for example. In both of these materials, the barrier layer provides a buffer and a filter between two relatively rough surfaces of the front and rear screen. If the barrier layer were not present, the surfaces of the two screens would intermesh into one another at their interface, thereby preventing good clear separation and purity with respect to the front and rear phosphor screen. A barrier layer such as magnesium oxide will result in considerable light from the rear screen being lost due to the opacity of the layer.
  • the layer In the case of silicon monoxide, the layer must be thin enough to permit passage of high voltage electrons and be free of voids which would permit passage of low voltage electrons.
  • a cathode ray display device and method of producing same, is disclosed which produces light of varying color in response to electron excitation of varying energy.
  • the display screen of the device comprises a plurality of distinct thin phosphor layers. Each phosphor layer comprises a material with a diverse color output from the other phosphor layer.
  • the distinct layers have a very high uniformity of average thickness.
  • the phosphor layers are successively deposited upon the substrate by an electrophoretic process, which provides the high uniformity of layer thickness, which is the key to high resolution and color discrimination.
  • FIG. 1 shows a partially sectionalized cathode ray tube in connection with which the present invention may be usefully utilized
  • FIG. 2 is an enlarged sectional view of a portion of the screen of the tube shown in FIG. 1;
  • FIGS. 3 through 5 inclusive are enlarged views, in section, illustrating various steps in the process embodying the invention.
  • FIGS. 1 and 2 A color television tube is illustrated in FIGS. 1 and 2.
  • the tube includes an envelope 10 having an enlarged flared portion 12, a neck portion 14 and a faceplate portion 16.
  • An electron gun 20 is provided within the evacuated envelope and within the neck portion 14 for generating an electron beam which is directed onto the faceplate 16.
  • the faceplate 16 provides a substantial transparent window to the radiations emitted by a cathodoluminescent screen 24.
  • the screen 24 is comprised of a plurality of distinct thin layers of cathodoluminescent phosphors illustrated as layers 23 and 25.
  • Phosphor layer 23 is deposited on the inner surface of the faceplate portion 16 and is termed the front phosphor layer.
  • the second phosphor layer 25 is deposited on the rear surface of the layer 23.
  • a thin electrically conductive layer 26 of a suitable material such as aluminum is provided on the inner surface of the luminescent layer 25 for both improving the light output from the screen 24, as well as preventing ion burn of the material in the layers 23 and 25.
  • a suitable deflection system 28 may also be provided for deflecting the electron beam across the screen 24.
  • the front layer 23 may be of any suitable phosphor, which is for example P-l zinc silicate activated by manganese and emits a green color.
  • the second layer 25 may be a suitable phosphor, which is for example, P-22R, yttrium oxide activated by europium, which emits a red color.
  • the tube will emit in response to low energy excitation the color of the second layer 25, and in response to higher energy excitation will emit a combination of the colors from the two layers.
  • a glass panel of suitably transmissive glass is first provided with a thin electrical conductive transparent film 30.
  • the conductive film 30 illustrated in FIG. 3 comprises a plurality of conductive metal layers 32, 34 and 36, which may be applied by several techniques such as outlined in aforementioned U.S. Pat. No. 3,525,679. It is necessary that it have a resistivity of about ohm centimeter.
  • the glass is first cleaned by a suitable standard procedure such as treating with hydrofluoric acid.
  • the individual conductive layers 32, 34 and 36 can now be deposited on the faceplate.
  • the layers 32, 34 and 36 are by way of example respectively aluminum, gold and indiurn.
  • the faceplate 16 is then positioned in a vacuum system which is at a pressure of about 10' Torr. With the faceplate 16 having a diameter of about 5 inches, 5 milligrams of aluminum are positioned within an open crucible at a distance of about 19 inches from the faceplate 16, and the aluminum is evaporated to provide a layer 32 of a few angstroms in thickness. The aluminum layer 32 is illustrated in FIG. 3 and provides better adherence of the gold layer 34. After the coating 32 is applied, a crucible containing about 100 milligrams of gold is positioned within the evacuated chamher and..about 19 inches from the faceplate 16. The layer 34 of gold isevaporated onto the layer 32.
  • the gold layer 34 is also only a few angstroms inthickness, but is thicker than the 'layer32.
  • a protective coating 36 of a suitable material such as indium is evaporated onto the gold layer 34, by placing about 3 milligrams of indium in a crucible about 19 inches from the faceplate 16.
  • the indium layer 36 protects the gold layer 34 and makes it thermally stable.
  • a reading of the transmission of the radiations of wavelength of about 5000 angstroms through the conductive layers 32, 34 and 36 and the faceplate 16 is about 75%.
  • the resistivity of this resulting substrate of layers 32, 34 and 36 is about 100 ohm centimeter, and provides an excellent conductive electrode for the deposition of the luminescent layers 23 and 25.
  • the conductively coated faceplate seen in FIG. 3, is then ready for electrophoretic deposition of the phosphor layers thereon.
  • the faceplate is immersed in a phosphor bath which contains the finely divided zinc silicate front phosphor, in an amount sufficient to provide-the desired layer thickness for a given faceplate size.
  • the zinc silicate phosphor particles have an average particle diameter of less than about 1.5 microns.
  • the phosphor bath contains for example about grams of the phosphor, about 200 milligrams of a suitable electrolyte such as thorium nitrate, and about 900 milliletersof alcohol.
  • This mixture is elutriated for a given period of time, for example four hours, for the purpose -'o'f.obtaining the necessary small particle size of phosphor in suspension.
  • the suspension is gently agitated during the deposition of phosphor onto the substrate.
  • the conductive film 30 is connected to a source of potential.
  • the phosphor bath container is typically stainlesssteel which serves as the anode which is also connected to the source of potential.
  • the electrophoretic deposition is effected in about ten seconds by applying about 150 volts d.c. across the anode and film 30.
  • the time can be readily varied to vary the phosphor layer thickness, and the article will then be as seen in FIG. 4., with the front phosphor layer being preferably from about 3 to 5 microns thick.
  • the faceplate with front phospor layer 23 deposited thereon is thereafter introduced into a second phosphor containing bath to effect electrophoretic deposition of phosphor layer 25 in the same manner as already specified above for front phosphor layer 23.
  • the other phosphor layer 25 is for example europium activated yttrium oxide having an average particle diameter of less than about 1.5 microns, and the preferred thickness of layer 25 is from about 5-8 microns.
  • each phosphor layer is from about 3 to 8 microns in thickness.
  • the screened panel is then removed from the bath.
  • the conductive film 30, may remain.
  • the conductive substrate may be removed as more fully described in US. Pat. No. 3,525,679.
  • the faceplate 16 may. then be assembled in the cathode ray tubescen in FIG. 1 and sealed by methods well known in the art.
  • the bulb may also be provided with an aluminum coating 26 and may be applied in a well known manner by organic film technique. The organic film may be removed from beneath the aluminum during the normal bake-out tube which is about 10 minutes at 410C.
  • cathodolu- 1 minescent phosphors can be used in practicing the present invention. It should also be understood , that three or more thin phosphor layers of distinct materials can be so deposited to provide even a greater emission color variation dependent upon the excitation energy.
  • While the method of the present invention generally light transmissive substrate with the individual layers being in intimate contact with the adjacent layer, which method comprises:
  • a front phosphor layer upon the thin conductive film which is maintained at a predetermined electrical potential, which front phosphor emits visible radiation of a predetermined color'when electron excited, and which front phosphor layer substantially passes the emission from the other phosphor;
  • the thin conductive film comprises individual thin films, one atop the other, of aluminum over the substrate, gold over the aluminum, and indium over the gold.
  • front phosphor layer and the other phosphor layer are each of uniform thickness of from about 3 to 8 microns, with the variation from the average thickness being less than about :t 0.5 microns.
  • a finely divided front phosphor layer upon the thin conductive film which is maintained at a predetermined electrical potential, which front phosphor layer is deposited in a uniform thickness of from about 3 to 8 microns, which front phosphor layer emits visible radiation of a predetermined color when electron excited, and which front phosphor layer substantially passes the emission from the other phosphor;

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  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US337966A 1973-03-05 1973-03-05 Method of fabricating a color display screen employing a plurality of layers of phosphors Expired - Lifetime US3904502A (en)

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JP49019556A JPS49121473A (enrdf_load_stackoverflow) 1973-03-05 1974-02-20

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4130472A (en) * 1978-03-28 1978-12-19 Zenith Radio Corporation Process for making color television screens by electrophoretic deposition
US4204136A (en) * 1978-03-17 1980-05-20 Westinghouse Electric Corp. Dual layer phosphor screen for cathode ray tube
US4242371A (en) * 1976-06-25 1980-12-30 Thomson-Csf High-luminance color screen for cathode-ray tubes and the method for manufacturing the same
US5531880A (en) * 1994-09-13 1996-07-02 Microelectronics And Computer Technology Corporation Method for producing thin, uniform powder phosphor for display screens
US5582703A (en) * 1994-12-12 1996-12-10 Palomar Technologies Corporation Method of fabricating an ultra-high resolution three-color screen
US5667655A (en) * 1996-04-15 1997-09-16 Zenith Electronics Corporation Method of making color screens for FED and other cathodoluminscent displays
US6319381B1 (en) * 1998-06-11 2001-11-20 Micron Technology, Inc. Methods of forming a face plate assembly of a color display

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6042253U (ja) * 1983-08-30 1985-03-25 関西日本電気株式会社 陰極線管

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3314871A (en) * 1962-12-20 1967-04-18 Columbia Broadcasting Syst Inc Method of cataphoretic deposition of luminescent materials
US3554889A (en) * 1968-11-22 1971-01-12 Ibm Color cathode ray tube screens

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3525679A (en) * 1964-05-05 1970-08-25 Westinghouse Electric Corp Method of electrodepositing luminescent material on insulating substrate

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3314871A (en) * 1962-12-20 1967-04-18 Columbia Broadcasting Syst Inc Method of cataphoretic deposition of luminescent materials
US3554889A (en) * 1968-11-22 1971-01-12 Ibm Color cathode ray tube screens

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4242371A (en) * 1976-06-25 1980-12-30 Thomson-Csf High-luminance color screen for cathode-ray tubes and the method for manufacturing the same
US4204136A (en) * 1978-03-17 1980-05-20 Westinghouse Electric Corp. Dual layer phosphor screen for cathode ray tube
US4130472A (en) * 1978-03-28 1978-12-19 Zenith Radio Corporation Process for making color television screens by electrophoretic deposition
US5531880A (en) * 1994-09-13 1996-07-02 Microelectronics And Computer Technology Corporation Method for producing thin, uniform powder phosphor for display screens
US5582703A (en) * 1994-12-12 1996-12-10 Palomar Technologies Corporation Method of fabricating an ultra-high resolution three-color screen
US5667655A (en) * 1996-04-15 1997-09-16 Zenith Electronics Corporation Method of making color screens for FED and other cathodoluminscent displays
US6319381B1 (en) * 1998-06-11 2001-11-20 Micron Technology, Inc. Methods of forming a face plate assembly of a color display
US6383696B2 (en) 1998-06-11 2002-05-07 Micron Technology, Inc. Methods of forming a face plate assembly of a color display
US6406603B2 (en) 1998-06-11 2002-06-18 Micron Technology, Inc. Methods of forming a face plate assembly of a color display
US6458260B2 (en) 1998-06-11 2002-10-01 Micron Technology, Inc. Methods of forming a face plate assembly of a color display

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JPS49121473A (enrdf_load_stackoverflow) 1974-11-20

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