Abstract: The photosensitive resin which exhibits stickiness by photo-reaction is added with a binder which does not substantially raise dark reaction, and a resultant mixture is applied onto the inner surface of face panel of the color picture tube to form a film. Portion of the film where powdery material is going to be applied is exposed to light and rendered sticky. Phosphor powder, when used as the powdery material, is applied to the sticky portion and adhered thereto to form a fluorescent screen.

Abstract: Pigment coated phosphors comprising a europium activated yttrium oxysulfide phosphor having a europium activator value within a range of 0.04 gram atom to 0.066 gram atom per 1 mol of yttrium oxysulfide having adhered thereto red colored pigment particles such as cadmium sulfoselenide pigment particles, rouge pigment particles or red lead pigment particles, in respective amounts of 0.1 to 2.0 wt %, 0.05 to 2.0 wt % or 0.1 to 12 wt %, based upon the europium activated yttrium oxysulfide phosphor; and a cathode ray tube for high contrast color television using as a red emitting phosphor at least one of the three pigment coated phosphors.

Abstract: Filter phosphors consist of phosphor particles coated with a filter material. A phosphor which shows a red emission when excited by cathode rays may be coated with red iron oxide by producing a thin layer of pyrite on the phosphor particles and thereafter converting the said layer into hematite. Thus, the surface of the phosphor particles is evenly coated with a uniform, dense pigment layer of extreme adherence. The filter phosphors thus obtained are used in cathode ray tubes and especially in color picture tubes.

Abstract: In forming a fluorescent screen for a cathode ray tube, an undercoat layer is first coated on the inner face of the panel. The undercoat layer contains at least polystyrene particles with a film weight of 0.002 to 0.04 mg/cm.sup.2. Coated on the undercoat layer is phosphor slurry.

Abstract: An intensifying screen having high physical durability and chemical resistance in which a curable resin is used as a resinous binder of a radioluminescent phosphor can easily be manufactured by employing an ultraviolet radiation-curable resin composition as the resinous binder. A dispersion comprising the ultraviolet radiation-curable resin composition and the radioluminescent phosphor dispersed in the composition is applied to the surface of a support to form a coating on the support, and the coating is cured by exposure to ultraviolet radiation to form a fluorescent layer on the support.

Abstract: A method is disclosed for providing an electrically conductive bridge between the high-voltage charged shadow mask of a color picture tube and the aluminum film deposited on the faceplate to ensure that the aluminum film is charged with the same high voltage present on the shadow mask. A paintable solution is provided which essentially comprises a mixture of substantially equal parts of glass frit particles and graphite particles in the micron-sized range. The particles are in solution in an evaporable solvent including a thickening agent in an amount sufficient to provide a paintable viscosity.

Abstract: Disclosed is a method for surface treatment of phosphor particles which comprises forming a continuous film of silicon dioxide on the surface of each phosphor particle by treating the phosphor particle with a solution containing an aqueous solution of organic alkali and silicon dioxide dissolved therein.

Abstract: A phosphor for color television surface-treated with zinc hydroxide so that zinc hydroxide attaches thereto in an amount below 0.7 part by weight per 100 parts by weight of the phosphor.Phosphor slurries for production of phosphor screens prepared from the phosphor have improved light-exposure sensitivity at the formation of and produced from these slurries phosphor screens showing less color mixing.

Abstract: A method for coating a selected portion of the internal surface of the neck of a CRT having a beaded electron-gun mount assembly housed therein. The method comprises providing in the neck at least one source of chromium metal spaced from and within line-of-sight of at least a portion of the neck surface opposite each bead. The CRT is evacuated to a low gas pressure and then chromium metal vapor is released from each source towards the neck surface, whereby chromium metal deposits on the neck surface.

Abstract: In a method of manufacturing a color picture tube of the type comprising the steps of coating phosphors of three primary colors on the inner surface of the face plate of the color picture tube to form dots or stripes of the phosphors, applying an acrylic resin emulsion on the dots or stripes of the phosphors to form an acrylic resin film, vapor depositing metal onto the film to form a metallic reflecting film, subjecting the acrylic resin film to a pyrolysis for decomposing it into gases, and removing the gases, the acrylic resin emulsion comprises a plurality of emulsions respectively containing conventional acrylic resin and normal butyl methacrylate resin. The normal butyl methacrylate resin is mixed with the conventional acrylic resin at a ratio of 5 to 40% by weight.

Abstract: A layer of an aqueous solution containing polyvinyl alcohol and a zirconyl compound is applied to a clean glass surface and dried to produce a precoating thereon. A subsequently-applied phosphor-photobinder coating thereon is exposed to a light image and then developed with a turbulent aqueous liquid. The phosphor-photobinder coating exhibits improved adherence to the surface during the developing step due to the presence of the precoating.

Abstract: A process for forming a phosphor screen of a color picture tube comprising forming a thin layer using a photosensitive composition which contains an aromatic diazonium salt as a photosensitive component and produces tackiness by exposure to actinic light on the surface of the substrate and contacting the tackified thin layer after exposure to light with phosphor particles to form each phosphor layer for emitting color is improved by using as the phosphor particles those coated with at least one surface coating material selected from the group consisting of Zn(OH).sub.2, Zn.sub.3 (PO.sub.4).sub.2 and AlPO.sub.4 in shortening the contact time between the thin layer and the phosphor particles.

Abstract: A method of producing material patterns in which at least one substrate is fixed together with a mask to a substrate holder, and an evaporated film of desired substances is formed on the surface of the substrate by means of evaporation sources provided to confront the substrate. The mask is fabricated to have a plurality of reinforcing bridges formed in the desired portions of the mask openings of desired shape formed in the mask. The mask is held spaced from the substrate by a small distance during the evaporation, so that the evaporation may be effected at least through two pattern openings defined at both sides of each bridge.

Abstract: A method of manufacturing a fluorescent screen for color picture tubes comprises applying to the tube front plate a continuous sensitized filter layer and exposing it, applying a continuous sensitized fluorescent layer and exposing it through a mask and removing the unexposed parts of the fluorescent layer and the filter layer therebeneath by washing.

Abstract: In the manufacture of a striped phosphor screen for a black matrix type color picture tube, a pattern of stripes of a light-absorbing material is first formed on the faceplate of a glass envelope to define transparent striped windows thereon by a known process and then phosphor materials are applied to the striped windows by the use of a nozzle assembly having at least one nozzle capable of discharging a phosphor material, without owing to the photolighography. The coating apparatus comprises a nozzle assembly including one or more nozzles, drivers for effecting relative movement between the nozzle and the faceplate of the glass envelope in a first direction in the plane of the faceplate and perpendicular to the stripes, in a third direction perpendicular to the faceplate and in a second direction longitudinal of the stripes, sensors for detecting the position of the nozzle, generators for producing a positional error signal and control for controlling the position of the nozzle.

Abstract: An europium activated oxysulfide phosphor represented by the formulaLn.sub.2 O.sub.2 S:Eu,(Sm)wherein Ln is at least one element selected from the group consisting of yttrium, gadolinium, lanthanum, lutetium and scandium is colored into red by mixing therewith a proper amount of calcium salt solely or together with strontium salt, and firing the resulting mixture at a temperature within the range of 1000.degree. to 1500.degree. C. By the firing, a CaS:Eu,(Sm) phosphor or a (Ca,Sr)S:Eu,(Sm) phosphor having a red body color is produced in an external portion of the Ln.sub.2 O.sub.2 S:Eu,(Sm) phosphor particle. The red colored phosphor thus obtained is used as a red emitting phosphor of a high contrast cathode ray tube for color television.

Abstract: A process is provided for producing electroluminescent powders for use in information display panels of the type in which a monoparticle layer of electroluminescent powder is embedded in a high dielectric constant resin between two electrodes. The powders are zinc sulfide powders coactivated with aluminum and capable of emitting white light, as well as light of various colors. In the production of these powders they are treated to form an impermeable inorganic surface coating on the powder particles. The coating may be zinc phosphate or glass.

Abstract: A method for the manufacture of multi-colored microlithographic displays especially fluorescent screens for cathode ray tubes is provided in which a film of a positive phototackifiable polyacetylene sulfone polymer is applied to the substrate of the display. The film is then exposed in predetermined areas with a sufficient amount of radiation to tackify the exposed areas. The exposed areas are then contacted with a pigment or phosphor which is desired to be applied to the exposed area and it selectively adheres to the exposed areas. The exposure and dusting are repeated for each application of different color pigments, toners or phosphors.

Abstract: A method for the manufacture of multi-colored microlithographic displays especially fluorescent screens for cathode ray tubes is provided in which a film of an olefin sulfone polymer is applied to the substrate of the display. The film is then exposed in predetermined areas with a sufficient amount of radiation to depolymerize and lower the melting point of the polymer in the exposed areas. The film is then heated to a temperature above the softening point of the exposed polymer but below the softening point of unexposed polymer and contacted with the pigment or phosphor which is desired to be applied which selectively adheres to the exposed areas. The exposure and dusting are repeated for each application of different color pigments, toners or phosphors.

Abstract: To coat the inner surface of the viewing window of a faceplate panel for a cathode-ray tube, of the type having a peripheral sidewall or flange around the window, dispense onto the surface a quantity of slurry in excess of what is required for the desired coating, spread the dispersed slurry over the surface, wet the uncoated inner surface of the sidewall with an aqueous medium, pass the excess portion of the slurry over the wet sidewall surface for removal from the panel, and then remove particulate material from the inner sidewall surface.

Abstract: An improved method of forming a multicolor cathode-ray tube display screen to minimize phosphor contamination. A light-absorbing matrix is first formed on the inner surface of a CRT faceplate, preferably by photoetching of a substantially black metallic layer. Then, multiple color dot patterns are deposited in the matrix openings by (a) depositing a layer of positive photoresist on the matrix and any previously-deposited dot pattern; (b) exposing the resist through a shadow mask to light from a point source positioned to simulate an electron gun; (c) developing the resist to form an integral mask containing a pattern of holes aligned with the matrix openings for one color phosphor; (d) coating the developed resist layer with a photohardenable phosphor slurry; (e) exposing the slurry coating through the faceplate to light from a diffuse source; (f) developing the slurry to remove the unexposed portions, leaving a pattern of dots of one color; and (g) stripping away the photoresist masking layer.

Abstract: In a method of forming a fluorescent screen on the inner surface of a face plate of a color picture tube wherein a film of photosensitive composition consisting essentially of a diazonium salt, the portions of the films to be deposited with phosphors are exposed to light through a color selection electrode so as to impart sticky property to the portions by a photoreaction and moisture in atmosphere and then a powder of phosphors is deposited by utilizing the sticky property, a photosensitive binder is incorporated into photosensitive film which undergoes a cross-linkage reaction with the photosensitive composition, thus rendering the mixture insoluble in water.

Abstract: A method for forming patterned screens for cathode ray tubes wherein a multiplicity of viewing areas are spaced in accordance with and dimensionally smaller than openings of a mask member comprising the steps of coating the inner surface of a viewing panel with polyvinyl alcohol photosensitized with dichromate; exposing the viewing panel at a first positional location to radiant energy beamed through the mask openings; moving the viewing panel to a second positional location and exposing the viewing panel to radiant energy beamed through the mask openings; developing to remove the unexposed coating from the viewing panel; treating the exposed viewing panel with a dilute organic etching composition to erode the coating exposed to the radiant energy at one of the first and second positional locations; and washing the viewing panel to remove the etching composition and eroded coating leaving polymerized coating of a dimension smaller than the openings of the mask member.

Abstract: A method of making a display screen for a color television display tube in which a photoconductive layer on the window portion of the tube is provided with a uniform charge which may be either positive or negative. A charge pattern is then formed on that layer by scanning it with an electron beam passing through an apertured color selection electrode. The energy of the beam is such that the average depth of penetration of the electrons is greater than the thickness of the photoconductive layer so that the charge disappears at the regions struck by the beam. The remaining charge pattern is developed with a suspension of charged phosphor particles. By repeating this process, patterns of red, green and blue luminescent phosphor particles can be successively provided to form the display screen. It is also possible to scan the layer simultaneously or successively by three electron beams and to develop the resultant charge pattern with a light-absorbing pigment.

Abstract: A slurry comprised of particulated glass-forming substances, with or without particulated relatively clear or light-colored metal oxides, dispersed in a photolacquer is applied as a uniform layer on a surface of a color image screen. Such layer is then developed via conventional photoforming techniques to produce sites or windows for phosphor dots and the resultant window-containing layer is heated, prior or subsequent to application of phosphor dots in such windows, at a temperature in the range of about 350.degree. to 500.degree. C. In instances where metal oxide particles are present in the slurry, the resultant layer becomes opaque or dark upon tempering and in cases where only pure glass-forming substance particles are in the slurry, the resultant layer becomes opaque or dark upon tempering in a reducing atmosphere. Electrical conductivity may be imparted to the light-absorbing coating by addition of selective conductive materials to the initial slurry.

Abstract: A method is disclosed for producing a pigment coating on a substrate. A hardenable polymer coating is initially provided on the substrate, followed by an excess of hardening agent. This produces a first hardened coating with sufficient hardening agent remaining to harden a second polymer coating, containing suspended pigment, which is deposited on top of the first coating. The polymer is then pyrolyzed, leaving a coating of pigment on the substrate.

Abstract: Luminescent materials are adhered to TV color picture screens or image display device screens by coating the inner surface of a glass screen substrate with a conductive or non-conductive C.sub.1 to C.sub.4 alcoholic or carboxylic solution containing oxygen-rich organic materials selected from the group consisting of silicon salts of relative low molecular weight carboxylic acids, tin salts of relatively low molecular weight carboxylic acids (which can be optionally doped to render them conductive, if desired) or mixtures thereof or a doped tin compound, at least partially drying such coating, as at a temperature of about 150.degree. C., applying a select pattern of luminescent materials onto such partially dried coating and curing or tempering the resultant structure, as at a temperature of about 500.degree. C. so that the luminescent material is firmly embedded within the conductive/non-conductive coating.

Abstract: The screen comprises superimposed layers of phosphor crystals having fluorescences of different colors separated by an inert layer having a substantially uniform thickness. In one example, the layers are of green phosphor P1 (J.E.D.E.C.) (.lambda.=550 nm) and red phosphor yttrium vanadate activated with europium (.lambda.=610 nm), in a proportion of 3 to 4 mg/cm.sup.2 and 0.15 mg/cm.sup.2 respectively. The inert layer is silicon sesquioxide (Si.sub.2 O.sub.3), and has a thickness of 1.2 .mu.m. High luminances are obtained throughout the range of colors, for operating voltages ranging between 10 kV and 17 kV.

Abstract: A method for preparing a screen structure for a cathode-ray tube comprising(a) exposing a water-soluble photopolymeric film on a surface to a light image to insolubilize selected portions of the film,(b) flushing the exposed film with an aqueous medium that is free from borate ions to remove only the still-soluble portions of the film, thereby producing a stencil on the surface,(c) rinsing the stencil with an aqueous solution containing borate ions to prevent further removal of material from said stencil,(d) then overcoating the stencil and the surface not covered by the stencil with pigment particles,(e) and then removing only the stencil and the overcoating thereon.

Abstract: Pigment-coated phosphors which may be used in the production of a cathode-ray tube of a high contrast for a color television receiver can be produced by adding a pigment and an anionic polymer emulsion to an aqueous suspension of a phosphor and then making the system neutral or weakly acidic or adding a cationic polymer emulsion or carrying out both of these steps so that the phosphor and the pigment may be coated with the polymer.

Abstract: This invention relates to improvements in the art of aluminizing the phosphor screens of image display devices such as television cathode ray picture tubes. An improved method comprises the application of a highly alkaline aqueous dispersion of a siliceous coating agent and a surfactant prior to aluminizing. The solution includes an acidic pH-lowering substance in an amount sufficient to adjust pH to a neutral range.

Abstract: An absorbing coating consisting of three layers sequentially deposited on e aluminized phosphor screen of an electro-optical device such as an image intensifier. The layers are: a transparent dielectric layer with a thickness of about one quarter wavelength of radiation to be absorbed, a thin metal semitransparent layer, and an aluminum oxide protective layer for the thin metal layer. The coating is transparent to electrons bombarding the phosphor, but absorbs radiation which might pass through the photocathode and be reflected from the phosphor aluminum coating back to the photocathode. Such reflected radiation can cause spurious output electrons from the photocathode.

Abstract: A method for manufacturing a phosphor screen for a color picture tube is disclosed which comprises the steps of transferring an ink pattern contained on an intaglio having a surface comprising ink receiving portions with a depth of 10.mu. or more, said ink containing 15 to 90% by volume of phosphor powder, by rotatably moving at a first speed a transcriber having a cylindrical surface covered with a layer of a soft material along the surface of the intaglio in order to apply the ink pattern onto the cylindrical surface of the transcriber and transcribing said ink pattern from said transcriber onto an object to be printed for a color picture tube by rotatably moving the transcriber at a second higher speed along the surface of said object.

Abstract: A pigment-coated phosphor having good finish sieve passability and capable of forming a fluorescent film with excellent properties can be produced from a process characterized by:(1) the first step of adding to a water suspension of a phosphor and a pigment an anionic polymer emulsion which has a minimum film forming temperature of less than 30.degree. C.;(2) the second step of adding a cationic polymer emulsion which has a minimum film forming temperature of 30.degree. C. or lower;(3) the thrid step of adding an anionic polymer emulsion which has a minimum film forming temperature of 30.degree. C. or higher; and(4) the fourth step of making the mixture system neutral or weakly acidic.

Abstract: This invention relates to improvements in the art of aluminizing the phosphor screens of image display devices such as television cathode ray picture tubes. A solution for rewetting a phosphor-bearing image display faceplate prior to aluminizing comprises a highly alkaline aqueous dispersion of a siliceous coating agent and a surfactant. The solution according to the invention includes an acidic pH-lowering substance in an amount sufficient to adjust pH to a neutral range.

Abstract: A process is provided for producing electroluminescent powders for use in information display panels of the type in which a monoparticle layer of electroluminescent powder is embedded in a high dielectric constant resin between two electrodes. The powders are zinc sulfide powders coactivated with aluminum and capable of emitting white light, as well as light of various colors. In the production of these powders they are treated to form an impermeable inorganic surface coating on the powder particles. The coating may be zinc phosphate or glass.

Abstract: In a method for preparing a luminescent screen which includes depositing a light-absorbing matrix upon a support, depositing a phosphor-particle layer on the matrix and support, and then coating the phosphor-particle layer with a film of organic polymeric material, the steps for salvaging the support and matrix substantially undisturbed, while substantially entirely removing the overlying material. In the method, the overlying material is contacted with an alkaline aqueous solution until the organic polymeric film is at least partially solubilized. Then, the overlying material is substantially entirely flushed away.

Abstract: A window part for a color CRT is coated with a photosensitive layer which is exposed through the apertures of a shadow mask to a rotating light source having a direction of greatest light intensity directed to the center of rotation.

Abstract: On the surface of a phosphor, pigment particles are uniformly adhered by a layer of a gelatin-gum arabic mixture. A process for manufacturing such a pigment coated phosphor includes the steps of preparing an aqueous solution of gelatin and an aqueous solution of gum arabic, allowing the phosphor to disperse homogeneously into one of these aqueous solutions, allowing the pigment particles to disperse homogeneously into the other aqueous solution, and mixing the so obtained phosphor and pigment dispersions.

Abstract: A process for fabricating matrix cathode ray tubes having phosphor receiving areas smaller than the areas exposed through an apertured mask includes the steps of coating the inner surface of a viewing panel with a first film of photo-sensitive resist material; exposing the first film through an apertured mask to provide insolubilized areas of a given size; depositing a second film of resist material onto said first film; removing the second film, soluble areas of the first film, and portions of the insolubilized areas of the first film to provide insolubilized areas of the first film of a size smaller than said given size; overcoating with an opaque film, removing the overcoated insolubilized areas of a size smaller than the given size; and depositing phosphors in place of the removed insolubilized areas of a size smaller than said given size.

Abstract: A method for coating with a liquid the window panel of a display tube by means of at least one brush mounted for rotation in a reservoir containing the liquid. As the partially submerged brush is rotated about its axis, drops of liquid picked up by the brush hairs are flung against the window panel. This method results in continuous mixing of the coating material and the return of the excess coating liquid back into the reservoir so that losses of the coating material are minimized.

Abstract: In a process for producing a color television picture tube which comprises at least the step of coating phosphor slurries onto the inner surface of a panel to form a phosphor layer, the step of forming two layers each consisting of an aqueous filming emulsion containing an acrylic resin, the step of forming a metal film on the second layer, and the step of baking out the organic substances, a color television picture tube having a metal film which contains a few pores and cracks and no blister can be produced by using said phosphor slurries containing an acrylic resin and using the first aqueous filming emulsion containing an acrylic resin having an elongation of 10% or more and using the second aqueous filming emulsion containing an acrylic resin having an elongation of less than 10%.

Abstract: This invention relates to light absorbing inhomogeneous films and their use in luminescent display devices such as cathode ray tubes and electroluminescent panels to achieve high contrast ratio and minimal halation effect, and more particularly to an inhomogeneous film having a composition varying continuously from metal oxide to metal, and the method of making same. The metal is selected from the group consisting of tantalum and vanadium.

Abstract: A pigmented phosphor comprises a core of a phosphor particle having a light modifying layer thereon. The light modifying layer is comprised of a co-precipitated mixture of silica or pyrophosphate and a pigment which modifies the light output of the energized phosphor. The phosphor is coated by first preparing an unique pigment stock suspension containing the pigment, water, and a polyacrylamide dispersant. The stock solution is then diluted and phosphor particles are added thereto and the mixture is vigorously stirred. The pH of the mixture can be adjusted to about 5 by the addition of acetic acid and then a small amount of positively charged colloidal silica or pyrophosphate is added. After mixing, the pH is raised to about 9 by the addition of a base or a salt which causes a gel to form and the silica or pyrophosphate and the pigment to co-precipitate out upon the phosphor particles.

Abstract: In a process for the production of color television picture tubes which comprises at least the step of forming a phosphor layer on the inner surface of a panel, the step of coating said inner surface of the panel including said phosphor layer with an aqueous emulsion of a water-insoluble film-forming resin to form a volatilizable substrate layer, the step of forming a metal film on the substrate layer and the step of volatilizing the organic substances, a color television picture tube in which the blister or separation of the metal film can be prevented in said volatilization step and the undecomposed resin does not remain and which has an improved brightness can be produced by forming said substrate layer from at least two layers each of an emulsion, adding colloidal silica, an aqueous ammonium oxalate solution and aqueous hydrogen peroxide to the first layer emulsion, and adding polyvinyl alcohol-boric acid complex and a small amount of ammonium hydroxide to the emulsion of the layer contacting directly wit

Abstract: A method for metallizing a phosphor screen for a cathode ray tube including the steps of forming a volatilizable substrate on the surface of the phosphor screen and depositing a metal layer on the substrate, followed by heating for volatilizing the substrate, said substrate comprising a laminate of superposed layers respectively representing different organic materials having different thermal decomposition points. This disclosed method is advantageous in that the substrate can be volatilized without causing blistering of the metal layer and the formed metal layer is enabled to reflect light more effectively.

Abstract: A display device includes a layer of electroluminescent material which is capable of conducting electric current. The electroluminescent material is sandwiched between a pair of electrodes to which a voltage is to be applied to excite the electroluminescent material to luminescence. The display device is manufactured by disposing on an assembly comprising a substrate with one of the said electrodes thereon, two masks in which are formed aligned apertures defining a region in which the electroluminescent material is to be provided. The electroluminescent material is disposed in the apertures, and, after that material has solidified one of the masks is removed, the other of the electrodes then being formed on the exposed surface of the electroluminescent material and within slots in the remaining mask and the mask is removed.

Abstract: The mosaic image screen of a shadow mask color tube has a plurality of sets of elemental screen areas, each of which areas includes a phosphor for emitting light of one of three primary colors and a filter which is transmissive of that color but otherwise is essentially a visible light attenuator. The color filter for the first set is formed by applying a thin film of a metallic resinate of a particular color onto the faceplate, directing a laser beam to the elemental screen areas for the other two primary colors to liquify the film and to withdraw the liquefied film from these areas, and heating the entire film to raise the energy threshold at which liquefaction occurs. Second and third metallic resinate films of the other two colors are similarly processed, and then all three films are heated to volatilize their respective organic material to form the color filters.

Abstract: A cathode ray storage tube provided with a storage target having a multiplicity of segments of the collector electrode extending through the dielectric layer of the storage target. These segments comprise dots or continuous or broken protrusions of conductive particles that have been photo-deposited into position onto the collector electrode and then the storage dielectric layer is applied thereover which has proper thickness so that the segments extend above the dielectric thereby providing collector areas for collecting secondary emitted electrons from the dielectric.

Abstract: Cathode ray phosphor compositions that are resistant to photodeposition slurries consist essentially of discrete particles of a phosphor material having a core of silver-activated zinc sulfide and a coating over a substantial amount of the external surfaces of a composition represented by the formula, Mg.sub.2 P.sub.2 O.sub.7 :Al.sub.4 (P.sub.2 O.sub.7).sub.3 . xSiO.sub.2 wherein the coating is at a sufficient level on the surfaces to provide a PO.sub.4 content of the composition of from about 0.05% to about 0.2% by weight and the SiO.sub.2 content sufficient to impart flowability. The coating composition is formed by a slurry process that enables a uniform and adherent coating to be deposited on the surfaces of the particles of silver-activated zinc sulfide.