HUT72017A - Luminescent materials prepared by coating luminescent compositions onto substrate particles - Google Patents

Description

According to the invention, oxalic acid may be added to the slurry instead of metal chelates and a luminescent sulfite composition may be prepared.

Also included within the scope of the invention are fluorescent tubes, light emitting devices, fluorescents, plasma displays, and a paste composition comprising a luminescent powder composition.

Represented by ^Κ8 »1,.,

DANUBIA Patent and Trademark Office Ltd.

Budapest

Luminescent powder composition, articles containing this powder composition and process for producing such powder composition

E.I. DU PONT DE NEMOURS AND COMPANY, Wilmington, DE, US

inventors:

BRUNO Salvatore Anthony SWANSON Donald Keith

Wilmington, DE, US Wilmington, DE, US

The international filed on: 08/12/1993 PRIORITY: 12/18/1992 (07 / 995,647, US) 6/6/1993 (08 / 067.402, US) 11/5/1993 (08 / 148,734, US)

The international

International filing number: filing number

PCT / US93 / 11701

WO 94/14920

File number: 81549-7340 / VO / LZs

The present invention relates to a novel luminescent powder composition which can be obtained at a favorable cost and to a process for the preparation of such a composition. The invention also relates to articles containing this powder composition.

Luminescent materials or fluorescent materials contain a substrate which, together with one or more activators, converts the absorbed energy into radiant energy. and oxides, oxysulfides, phosphates, vanadates and silicates of yttrium, gadolinium or lantene. Commonly used activators include rare earth ions such as europium (II) -, europium (II) -, terbium (II) -, cerium (II) - and tin (II). The chemicals containing the starting material and the activators are usually mixed by mechanical means, such as grinding or micronization, and then calcined to produce a light powder of relatively uniform composition. For many applications, these powders can be applied as a coating to a substrate such as glass, typically.

Rare Earth Oxide (REO) -activated fluorescent lamps are used, inter alia, in trichromatic bulbs, cathode ray tubes, color television sets and high definition television picture tubes. Most rare earth oxides are very costly, limiting their use to some applications. By combining three narrow spectral bandwidths of light, blue-violet, orange-red and green, conventional fluorescent lamps at three wavelengths emit white natural light. Barium Magnesium Aluminum or Eu Activated with European (II) Ions • ·

- 3 strontium chloropatite activated with rhodium (11) ions can be used as blue powder, yttrium oxide activated with europeium (III) ions can be used as red powder, and magnesium aluminum activated with cerium / terbium ions can be used as green powder. Compared to white-light sources, such lamps have a higher color rendering, lifetime and energy efficiency. However, the sales of these fluorescent lamps on the market were hindered by their high cost due to the need to use expensive rare earth oxides.

CS 266 856 B1 discloses a luminescent composition comprising a silica core having a surface coated with a luminescent layer of mixed rare earth oxides. The aim of the solution according to the cited document is to reduce the amount of expensive rare earth light powders while maintaining the required lighting parameters. The compositions of the above document are prepared by using a rare earth salt solution / oxalic acid / diethyl ether system to deposit rare earth oxalates on the surface of activated silica particles and then calcining the oxalates to give an oxide-type powder. Examples of the cited document disclose coated silica particles in which the rare earth light powder layer has a weight of 60-95% by weight of the composition. The coating thicknesses described in the examples quoted allow for a minimal reduction in the use of expensive rare earth metals.

Accordingly, the present invention relates to a cost effective luminescent composition comprising a fine-grained, intact nucleus, wherein the surface of the particles is coated with a substantially luminescent material which is dispersed in a substantially chemically homogeneous coating on the surface of the particles. The average diameter of the core particles is generally 0.5 to 20 microns, usually from 1.0 to 10 pm, and the coating weight of the total composition is generally from 2 to 30 weight ⁰ / ».

The invention also relates to processes for preparing the above composition. In one process, the chelate solution of the luminescent precursor is decomposed in the presence of relatively high pH dispersed core particles, thereby coating the core particles at least partially with the water-containing metal oxides of the luminescent precursor. The coated core particles can be recovered, generally washed free of soluble materials, dried and calcined to convert the precursor, i.e., water-containing metal oxides, to a luminescent material.

In another embodiment of the invention, oxalate precursors of the luminescent composition are formed by adding aqueous solutions of oxalic acid and at least one metal salt of the luminescent composition to the stirred aqueous slurry of the core particles. The coated core particles are recovered, washed in the usual manner, free of solutes, dried and calcined to form and activate the luminescent material.

The process of the present invention can also be carried out by decomposing the above chelate solution in the presence of relatively high pH dispersed core particles, treating the aqueous oxide coating with a sulfite coating, recovering the product, washing it free from conventionally calcined in an oxidizing atmosphere, such that it is calcined in an essentially non-oxidizing atmosphere with an overlay salt, including sodium chloride, to activate the luminescent material.

The composition of the invention can be used as a cost effective material to replace conventional light powders such as rare earth light powders. The composition of the invention may be applied, inter alia, to a substrate such as a glass substrate. In some cases, the composition may be a component of one or more layers adhering to a substrate. Such coated substrates are useful, inter alia, in trichromatic bulbs, cathode ray tubes, color television and high-definition television screens, flat panel displays, such as plasma displays.

The present invention solves the difficulties associated with known luminescent materials by improving the utilization of the manufacturing costs of the rare earth components of the luminescent materials so that the luminescence coating is achieved by using luminescent coating instead of homogeneous material particles.

To date, relatively small particles, such as less than 5 µm, are less effective as luminescent materials. Contrary to this view, the luminescent material of the present invention may have an average crystal size of less than 5 µm, i.e. less than 0.5 µm, in the core particle, and still have relative intensity values (R (l) j, such as R l) values can be achieved. Accordingly, the invention relates to conventional luminescent

- Provides surprising and unexpected results compared to 6 cents.

To illustrate the invention, drawings are attached hereto.

Figure 1 is a commercially available photograph of a homogeneous phosphor under optical microscope at 600x magnification.

Figure 2 is a view of the product of Example 1 with an optical microscope at 600x magnification.

Figure 3 is a view of the product of Example 1 under an optical microscope at 1000x magnification.

Figure 4 is a view of the product of Example 2 under a 600 microscope optical microscope.

Figure 5 is a view of the product of Example 3 under an optical microscope at 1000x magnification.

Fig. 6 is a graphical representation of Figs. Example 1 and the relative intensities R (1) of the commercial product shown in Figure 1.

Figure 7 is a view of the product of Example 4 under an optical microscope at 1000x magnification.

Figure 8 is a graphical representation of the relative intensities of the product of Example 4 and commercially available uniform fluorescent R (1).

Figure 9 is a view of the product of Example 6 taken with an optical microscope at 600x magnification.

Figure 10 is a view of the product of Example 6 taken with an optical microscope at 600x magnification.

··· • · · · · · · ·

Figure 11 is a graphical representation of the relative intensities of the product of Example 6 and the commercially available product R (1) of Figure 1.

Figure 12 is a view of the product of Example 7B taken under an optical microscope at 600x magnification.

Figure 13 is a vertical sectional view of a plasma display.

Based on the foregoing, the present invention provides a luminescent powder composition comprising particles of an inert core and at least one luminescent coating thereof, wherein the combined coating is 2 to 30% by weight of the total composition, wherein the inert core is alkaline earth metal sulfate, alkaline earth metal phosphate, containing at least one ingredient selected from the group consisting of calcium oxide, calcium carbonate and magnesium oxide.

The invention further provides a process for preparing a luminescent composition comprising:

a) preparing an aqueous or aqueous / organic slurry containing one or more inert particles,

b) adding to said slurry a stable solution containing at least one metal chelate,

c) raising the pH of the slurry to above 9,

d) increasing the temperature of the slurry to at least 50 ° C and maintaining the slurry at this temperature on at least part of the surface of the granules with at least one water-containing metal oxide,

e) recovering the granules, and

f) calcining the particles at a temperature suitable for activating the water-containing metal oxide on their surface to give a luminescent composition.

By "activation" we mean that the coated particles (i.e. the calcined coating on the particles become at least partially luminescent when excited by a suitable source of energy).

The invention further provides a process for preparing a luminescent sulfide composition comprising:

a) preparing an aqueous or aqueous / organic slurry containing one or more inert particles,

b) adding to said slurry a stable solution containing at least one metal chelate,

c) raising the pH of the slurry to above 9 and depositing at least a part of the surface of the granules with at least one water-containing metal oxide,

d) adding a solution containing at least one sulfide salt to the slurry, and heating the slurry containing the salt to convert the aqueous metal oxide on the surface of the inert particles to sulfide,

e) recovering the granules, and

f) calcining the recovered particles and forming a luminescent sulfide composition on their surface to form a luminescent sulfide composition.

Another embodiment of the invention is a process for the preparation of a luminescent composition comprising:

a) preparing an aqueous or aqueous / organic slurry of one or more inorganic particles of alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, alkaline earth metal fluoride or metal titanate,

- 9 b) adding oxalic acid to the resulting slurry,

c) adding to the slurry an acidic or aqueous / organic solution of at least one metal,

d) heating the slurry to a temperature sufficient to separate at least one metal oxalate salt on the surface of the inert particles,

e) recovering the granules, and

f) calcining the particles at a temperature suitable for activating the salt on their surface to obtain a luminescent composition.

The invention further provides a process for preparing a luminescent composition. According to this variant of the process of the invention

(a) mixing metal oxalate salts with particles containing at least one of inorganic alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, alkaline earth metal fluoride and metal titanate, and

b) calcining the mixture at a temperature suitable for the formation of the activated luminescent material on the surface of the particles to form a luminescent composition.

The core particles may also be coated by a suitable vapor deposition process. This involves exposing the core particles to a vapor containing a precursor of a luminescent material, which is deposited on at least a portion of the surface of the core particles. The vapor precursor of the luminescent material may, inter alia, be passed through a chamber containing core particles. In some cases, the volatile precursor, such as a vapor precursor

- 10 precursor degradable materials can be used. Although any suitable vapor precursor for the luminescent material may be used, the best results are obtained with a vapor precursor that does not react with the core particles and does not adversely affect the further processing of the coated core particles.

The novel composition of the present invention is a luminescent composition having a favorable manufacturing cost and typically comprising particles or cores having an average diameter of 0.5-20 μηι, usually 1.0-10.0 μηι. The surface of the core particles is suitably coated, at least in part, with a luminescent material which is distributed in a substantially chemically homogeneous layer on the particle, whereby, based on the total weight of the composition,

2-30% by weight, usually 5-20% by weight. Although it is not necessary for the luminescent material to completely cover the entire surface of the core particles, the amount of luminescent material should provide an R (l) spectrum substantially equivalent to conventional fluorescent dyes, thus providing an R (l) Reach 50-90%. Thus, at least a portion of the luminescent material may comprise a layer of generally coherent or dispersed luminescent crystals.

Although the composition of the luminescent coating is typically substantially homogeneous, the composition of the individual luminescent crystals may be partially different, so that the concentration of the activator within the crystal may vary. In some cases, the surface of the crystal in one or more activators may be relatively rich, so that the Eu / Y ratio on the surface of the Eu: Y ₂ O ₃ crystal may be greater than at the center of the crystal. Increased surface concentration of one or more activators within the crystal may enhance the efficacy of the luminescent composition.

The luminescent composition of the invention may be characterized by the relative luminescent intensity R (1). By definition, the emission peak R (l) is the number of strokes observed at the peak peak divided by the number of strokes measured on a reference detector for a given spectrometer configuration at the excitation intensity slit size. However, reporting only the R (l) value for a given fluorescent without further information can be misleading, since the R (l) obtained with a given spectrometer is typically specific to that spectrometer. Thus, two different spectrometers can give two different R (1) spectra for the same powder at the same setting values. Better usable R (l) values can be obtained by determining the R (l) spectrum of the test powder against at least one standard comparative luminous composition of similar composition (see details 6, 8 and

11).

To achieve a predetermined intensity, the amount of luminescent material and the activator concentration of the coating on the core particles can be determined. However, the amount of luminescent coating is desirably not greater than 30% by weight of the total composition, since amounts exceeding this may cause agglomeration of the luminescent material and / or the formation of a fine powder. For best results, the coating represents between 5% and 20% by weight of the total composition, providing an optimal combination of raw material cost and luminescence intensity. Megjegyzen-

however, this optimum amount may vary, among other things

1. depending on the size of the core particles,

2. Depending on the relative density of the core and the luminescent coating; and

3. depending on the conditions of end use.

It is important to distinguish between the amount of luminescent material used to achieve the coating of the present invention and the total amount of such material present in conventional fluorescents. The concentration of the luminescent activator in the coating may also exceed that of conventional homogeneous fluorescent light; however, the total weight of the luminescent activator in the compositions of the invention is usually lower than in conventional fluorescent dyes. In some cases, the present invention provides a composition comprising calcined core particles which are coated with an amount of at least one luminescent material which provides an R (1) value of at least 60% of the luminescent material.

The luminescent coating of the present invention may comprise at least one activator which may be, inter alia, a rare earth metal such as cerium or terbium, tin (II), antimony (III), copper, silver or manganese, and at least one suitable base material. Suitable starting materials include Y ₂ O ₃ , YVO ₄ , Sr ₂ P ₂ O ₇ , (Ca, Sr) ₅ (F, Cl) (PO ₄ ) ₃ , ZnS, Y ₂ O ₂ S, MgAI 4 O ₂ g and at least one component of BaMg ₂ Al ₁₆ O ₂₇ .

The properties of the core material or core particles are essential to the invention. The best results are obtained when the core particles are essentially inert. By "inert" is meant that the core particles do not substantially react with the luminescent coating in a manner that adversely affects luminescence. Since many luminescent compositions are typically heated to temperatures above 1000 ° C to activate the luminescent material, it is particularly important that the core material is substantially stable at such temperatures and does not exhibit reactivity. Certain undesirable impurities significantly reduce luminescence even at relatively low concentrations, and for best results the core composition should be substantially free of such impurities, or, if such impurities are present, prevented from entering the luminescent layer.

These unwanted impurities can also cause poisoning, which is the conversion of non-radiant energy into vibrational energy. The ions which have a non-radiant transition to their ground state and which must be avoided in the preparation of the composition of the invention include Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Al ³⁺ , and Si ⁴⁺ . In some cases, the sensitivity of luminescent materials to poisons varies inversely with activator concentration, so that alkaline earth metals may poison certain luminescent materials. Typically, an s-centered phosphor can withstand 100 times a given venom relative to an i-centered phosphor. The s-centered term refers to a substitutional activator, such as Eu atoms replacing Y atoms in the Eu: Y ₂ O ₃ luminescent material, while the i-centered term denotes an interstitial activator, as is the case with ZnS activated with Cu atoms.

Any toxins present in the composition may reduce the luminescent efficacy by:

1. decrease in solubility of the activator compound in the crystals of the parent material during formation of the phosphor,

2. direct absorption and conversion to primary energy of excitation energy,

3. release of excitation energy (as heat) absorbed by the crystal of the parent material and traveling to or from the activator center and captured by the toxic atom;

4. interaction with activator centers, which increases the likelihood of non-radiative transitions, such as lowering the transition point between the excited and ground potential curves of the luminescent composition,

5. receiving excitation energy from nearby activator centers and converting potential luminescent energy to heat by q-overlap energy transfer, and

6. Optical absorption of luminescent radiation as it exits the powder crystal.

The suitability of the core material particles can also be determined, in part, by the composition of the luminescent coating and the possibility of undesirable interaction between the two materials. In some cases, the core material should not absorb light at important frequencies, such as the frequencies of excitation radiation and radiation emitted. However, such absorption may also be desirable if more coatings are provided and / or the coatings have coatings containing more than one luminescent material. The core material is generally expected not to adversely affect the electrical processes involved in the operation of the light emitting device.

Water-soluble materials as a core are generally not suitable for use in the invention, although such materials, if otherwise acceptable, may be used in non-aqueous coating processes. In any case, unsuitable core particles can be made suitable for the purposes of the present invention by coating them with a material that substantially offsets or eliminates the unsuitable property. The materials of non-conforming core particles can be made suitable by applying a suitable core material for the present invention, which serves as an inert barrier coating between the material of the core particles and the luminescent coating. Whether a particular core material or a coated core material is suitable for use in the present invention will depend upon the particular luminescent material applied to the core, and for best results, the material used for the particular luminescent coating is used as the core. Suitable core particles include at least one of the constituents of alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, metal oxides such as aluminum oxide, magnesium oxide (MgO), mixed metal oxides and alkaline earth metal fluoride. The best results are generally obtained with core particles containing at least one of BaSO ₄ , CaO, CaF ₂ and CaSO ₄ .

»··

The core particles generally have substantially uniform dimensions in different directions of space, typically having an average diameter of 0.5 to 20 µm, typically 1.0 to 10.0 µm. It is desirable for the core particles to have a relatively narrow particle size distribution and a small average particle size. It is considered desirable to have a particle size of 90% of the core particles having a diameter between 0.1 D and 10.0 D (where D is the weighted average particle diameter). The narrow particle size distribution is particularly advantageous when the composition of the invention is used in fluorescent lamps, television screens, flat panel displays and the like. Without wishing to be bound by theory, narrow particle size distribution appears to improve particle fill efficiency and small particle size reduces the amount of luminescent material required to effectively coat the substrate.

The average particle size and particle size distribution can be determined by known methods [E. Dahneke, Wiley Interscience, N.Y. 1983]. Microtrac Type II particle analyzer (manufactured by Leeds Northrop and Company) is particularly useful for these procedures.

The outer surface of the core particles is coated with a substantially chemically homogeneous layer containing a luminescent material, which represents from 2 to 30% by weight, typically 5 to 20% by weight, of the total composition. The coating material may be [(base material: activator) form] (Y ₂ O ₃ : Eu), (Y ₂ O ₂ S: Eu), (YVO ₄ : Eu), (La, Ce, Tb) (PO ₄ ) ₃ : (Ce, Tb), (Zn ₂ SiO ₄ : Mn), (BaMg ₂ Al ₁₆ O ₂₇ : Eu), (SrB ₄ O ₇ : Eu), (Ce ₀ , ₆₅ Tb _{0 35} ): MgAI ₁₅ O ₁₉ , (ZnS: Cu), (ZnS: Ag), barium titanium phosphate, MgWO ₄ , alkaline earth metal activated by tin and europium 17

ortho- and -diphosphates, calcium halophosphates activated by tin and / or manganese, mixtures thereof and the like. They are particularly useful as coatings (Y ₂ O ₃ : Eu), (YVO ₄ : Eu), (BaMg ₂ Al ₁₆ O ₂₇ : Eu), (Ceo, ₆₅ Tbo, 35MgAlii ₁₉ ), (ZnS.Cu), (ZnS.Ag). ) and mixtures thereof, which can be used in a variety of industrially manufactured equipment such as light bulbs, TV screens, flat panel displays such as plasma displays. The luminescent material is generally present as interacting or dispersed crystals on the surface of the core particles, while the core particles may be in crystalline and / or amorphous state.

The compositions of the invention can be prepared in a number of ways. One method uses the chelate precursors of the luminescent components as carriers for the deposition of the luminescent precursor as water-containing metal oxide and / or metal oxide on the surface of core particles in slurry form. In another process, the luminescent precursor is deposited as oxalate on the core particles in the slurry. During subsequent calcination, the precipitated water-containing metal oxide, oxalate and the like can be activated on the surface of the core particles to produce a luminescent coating. In some cases, at least one of the components deposited or precipitated on the core particles is present in a solution containing an acid such as hydrochloric acid, so that the luminescent precursor is precipitated by raising the pH.

The luminescent composition of the present invention may also be prepared by admixing previously coated and / or uncoated core particles with a dry or wet state of metal oxalate powder and / or light powder, followed by calcining the pellets. The calcination temperature must be high enough to:

1. a coating of at least partially luminescent material is formed on the surface of the core particles, and

2. Activation of the coated particles.

The calcination temperature is usually 700-1400 ° C, usually

1000-1200 ° C.

According to the invention, it is also possible to coat the core particles by a suitable vapor deposition process. The core particles are exposed to a vapor containing a precursor of a luminescent material which is deposited on at least a portion of the surface of the core particles. The vapor precursor of the luminescent material may be passed through a chamber filled with core particles. In some cases, a volatile starting material may be used to produce the vapor precursor in situ, such as a vapor precursor material upon decomposition upon heating. Any suitable vapor precursor of the luminescent material can be used, however, the best results are obtained with a vapor precursor which does not interact with the core particles and does not adversely affect the further processing of the coated core particles.

In another embodiment of the process of the invention, the luminescent precursor is deposited in the form of a water-containing oxide on at least a portion of the surface of the core particles in the slurry. If desired, the aqueous oxide may be converted to a sulfide by contacting it with an active sulfur-containing material, which may be effected by treatment with a solution containing sulfur-containing salts such as potassium, ammonium and sodium sulfides. The treated water-containing oxide coating can be converted to a sulfide coating by heating to at least 90 ° C. The sulfide coated particles are recovered for further processing, washed to remove soluble materials, dried by heating to 120 ° C, and a second sodium salt, such as sodium chloride, is added to the dried sulfide coated particles. -20% by weight of dry NaCl. A calcination step is then carried out at 800-1000 ° C in a non-oxidizing atmosphere such as nitrogen to form a sulfide-containing luminescent coating on the core particles. Optionally, the second sodium salt may be removed by washing the sulfide coated particles.

In the practice of the present invention, it is also possible to process the core particles at a relatively high temperature, such as above 900 ° C, or at a calcination temperature sufficient to activate the luminescent material. The core particles can, inter alia, be transformed or decomposed to form metal oxide. Any convertible core particles can be used for this,

1. having a transition temperature below the activation temperature of luminescent material; and

2. which are inert or can be rendered inert.

Specific examples of suitable core particles include those containing, inter alia, CaCO ₃ and / or MgCO ₃ . The luminescent compound may be separated on convertible core particles according to one or more of the methods described above for the selected core particles, followed by calcination. During calcination, the convertible core particles are at least partially converted into metal oxide, which can be, among other things, CaO and / or MgO. The convertible core particles are believed to release at least in part CO ₂ during the formation of the metal oxide. The metal oxide may undergo further transformation due to exposure to water and carbon dioxide in the atmosphere. The metal oxide can thus be converted to hydroxide, i.e. CaO to Ca (OH) ₂ . The latter transformation process may be useful for bonding or fixing the luminescent material to the core particles.

US 5,082,811, which is incorporated herein by reference, discloses a particularly useful process for depositing a chemically homogeneous coating on a particulate substrate.

The process of the invention comprises the following steps:

a) preparing a mixed aqueous or aqueous / organic slurry of core particles,

b) adding to the stirred slurry a solution containing metal chelates of luminescent precursors,

c) raising the pH of the slurry to above 9 by adding an alkaline agent,

d) heating the slurry to a temperature ranging from 50 ° C to reflux and maintaining the metal chelates at least partially during 1-8 hours, usually 4-8 hours, thereby coating at least partially the coating of luminescent precursors on the surface of the particles. .

e) recovering the coated granules, washing and drying them in the usual manner, and then

f) calcining the dried powder under suitable conditions to activate the coating on the particles.

The slurry of the core particles as defined above may be prepared by mixing deionized water with at least one water-miscible organic liquid that does not adversely interact with the core particles or the luminescent precursor coating. The water miscible organic liquid may be a straight or branched chain alcohol having 1 to 4 carbon atoms, glycol or a mixture thereof.

A solution is prepared comprising the metal chelate of the luminescent precursor, at least one suitable chelating agent and at least one chelating agent. The term "chelating agent" refers to one or more multigene ligands (s) whose structure allows two or more donor sites to be linked simultaneously to the same metal ion, thereby forming a closed ring structure. A "ligand" can be any atom, ion or molecule that can serve as a donor in one or more coordinate bonds. Chelating agents useful in practicing the present invention include α-hydroxycarboxylic acids such as lactic acid, glycolic acid, malic acid and citric acid, or α-aminocarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), glycine, mixtures thereof and the like. A solvent such as deionized water or mixtures of deionized water with water-miscible solvents such as methanol, ethanol, isopropanol, mixtures thereof and the like are used in preparing the solution of the chelating agent. The solution may optionally contain a small amount of wetting agent 22 or two surfactants to aid in the dissolution of the metal compounds.

The amount of chelating agents must be sufficient to form a solution containing the metal chelates. The appropriate metal compound (s) may be added with stirring to a solution of the chelating agent and solvent described above. The metal compounds can be represented by the general formula MX _{n in} which

M represents a metal cation which may include, but is not limited to, magnesium, aluminum, zinc, copper, silver, calcium, strontium, barium, antimony, manganese, vanadium, tantalum, tungsten, yttrium, lanthanum, terbium, europium or lutetium or mixtures thereof,

X represents an anion or group selected from HCO ₂ ', CH ₃ CO ₂ ', -OH, -OR, NO ₃ 'and Cl' and mixtures thereof, and n represents an integer from 1 to 6 M ^{n +} depends on the valence of the metal cation.

Certain metal oxides soluble in mineral acids can be used as the source of the metal cation, including Y ₂ O ₃ , Eu ₂ O ₃ , ZnO, Sb ₂ O ₃ V ₂ O ₅ and mixtures thereof.

The pH of the solution described above is adjusted to a value in the range of 5 to 10, usually using a strong base such as ammonium hydroxide, tetramethylammonium hydroxide, sodium hydroxide, potassium hydroxide or a mixture thereof. In general, a pH of from 5 to 8 is suitable to obtain a stable solution of the metal chelates. The pH of the solution is an important factor in obtaining a stable solution of the metal chelates. Other important factors are the material quality of the metal compound, the metal compound23 ·

The valence of the metal in the jet and the chelating agent. When the pH of the solution is adjusted appropriately, the chelating agent forms soluble chelates with the metal cations added as the metal compound.

It is desirable that the metal compounds be substantially completely soluble in the solution, and that the amount of chelating agent allow complete dissolution. In some cases, a relatively clear solution is obtained after the chelating agent is added after the metal compounds are added to the solution.

After the solution of the metal chelates is added to the slurry of the core particles, the pH of the slurry is raised to above 9, typically above 10 by addition of a strong base such as potassium hydroxide and / or sodium hydroxide. The slurry is heated to 50 ° C to reflux and maintained at this temperature for up to 8 hours, typically at least 4 hours, to decompose the metal chelates on the surface of the core particles, generally chemically homogeneous. Ammonium hydroxide may also be used as the base. When ammonium hydroxide is used, relatively high temperatures are required to decompose the metal chelates. Typically, the metal chelates are decomposed by heating the slurry of the core particles in an autoclave at 100-200 ° C. If the metal chelate is converted with sodium hydroxide to the corresponding water-containing metal oxides and / or metal oxides, the conversion can be described by the following equation:

C

CH-R + xNaOH + ΧΗ2Ο χ

'' (Ο ο

Μ (0Η) 2Χ + xNa + O- -C-CH-R

I

OH υ

Μ Οχ ΧΗ2Ο + wherein R is _CH3 in case of lactic acid, and malic acid, R is -CH ₂ COONa ^+.

By controlling the reaction conditions, the water-containing metal oxides and / or metal oxides of the luminescent precursor can be deposited on at least a portion of the surface of the core particles. The coated core particles can be recovered by filtration or centrifugation, then any washable organic or inorganic material is removed by conventional washing with deionized water, and the washed particles are dried in air or in a vacuum oven.

The dried coated powder is then calcined at 700-1400, usually 1000-1200 ° C, which is sufficient to activate the luminescent precursor coating. The luminescent material is usually crystalline, and the luminescent coating consists of crystals on the surface of the core, interacting or dispersed.

• · ···

- 25 To activate the luminescent precursor and thus to produce the luminescent material optimally, calcination may require operation under oxidative, reducing or inert conditions. Specific calcination conditions are selected to optimize luminescent intensity and particle size distribution. For each particular composition, the R (l) of the luminescent material is generally a function of the calcination temperature. As a result, the calcination step can be used to influence the properties of the composition of the invention in the desired manner.

It may be advantageous to calculate the core particles, such as BaSO _4, and optionally grind the calcined particles, which can be carried out in a hammer mill or ball mill. The calcined particles are then suitable for coating with the luminescent precursor. By calcining and milling, a final product having a relatively narrow particle size distribution (PSD) is obtained, thereby reducing the average particle size. Prior to application of the luminescent coating, calcination of the core particles is expected to reduce the formation of persistent agglomerates when the core particles coated with the luminescent material are re-calcined to activate the coated particles. The conductivity of calcined / ground BaSO ₄ core particles, washed with an acid to remove acid-soluble undesirable substances in a mineral acid such as hydrochloric acid, may be less than 50 gS, resulting in an increased R (l) of the coated luminescent luminescent composition.

The composition of the coated powders can be determined by X-ray fluorescence analysis or inductively coupled plasma (ICP) analysis. The crystalline core material or the luminescent coating can be determined by X-ray diffraction. The surface coating properties can be examined by optical microscopy, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The specific surface area can be determined with a Micromeritics Flowsorb II 2300 instrument based on a single point BET, and the particle size can be determined with a Microtrac Type II particle size analyzer.

The relative intensity of the coated core R (l) can be determined using a SLM-8000 fluorescence spectrometer. Relative intensity can be determined by placing the coated particles in a quartz cuvette placed in the center of the instrument sample holder. The excitation wavelength commonly used to excite most photoluminescent compositions in fluorescent lamps is about 254 nm, which is the primary wavelength of the mercury vapor lamp. In a fluorescence spectrometer, the excitation wavelength is generally obtained by means of a xenon lamp and a double-lattice excitation monochromator. The R (l) value of each sample is determined by four replicate measurements, whereby one measurement is made on each sheet of the quartz cuvette and the mean value is determined, i.e. the average value minimizes the systematic error caused by the sample holders. Uniform compositions, such as Y ₂ O ₃ : 5 mol% Eu, prepared by the oxalate process described above, are used as standard for some coated particles. • •

Prior to measuring the R (l) value of the 27 particles, the spectrometer is set to a R (l) value of 2.1 for this standard.

Although the foregoing description has particularly emphasized the coating of a single luminescent precursor on core particles, it is to be noted that the invention relates to multiple luminescent coatings, so that the luminescent material may comprise multiple coatings, so applied successively, that absorb the same and / or different colors. and / or emit. In some cases, additional coat (s) may be applied to previously coated core particles to form a composition that emits light of a specified characteristic, so that core coated with red light can be re-coated with green light.

The invention can also be used to provide a mixed luminescent coating, such as a coating comprising at least one layer comprising a plurality of luminescent materials. Following the preparation of the composition of the present invention, the composition can be treated or post-treated to control its properties, which inter alia prevents the degradation of the luminescent coating and protects it from moisture. Thus, the properties of the composition of the invention can be modified by coating with silica, which minimizes the reaction of the composition after it has been used, thus being used as a fluorescent lamp in a fluorescent tube. In some cases, it may be desirable to use, among other properties, a mechanical mixture of particles of different size, composition, coated with luminescent material. Properly selected core material (s), luminescent coating (s), coating (s)

By selecting a process, mixtures of coated materials and optionally post-treatment options, the properties of the luminescent composition of the present invention can be controlled so as to effectively satisfy an unlimited number of end uses.

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.

Example 1

This example describes a process for the preparation of a powder containing barium sulfate coated with 2.04% Eu ₂ O ₃ and 24.86% Y ₂ O ₃ using the chelate process.

A 2 L flask was charged with deionized water and 23.4 g (0.2318 mol) of D, L-malic acid under nitrogen at 23 ° C (540 mL). While stirring in the flask, yttrium oxide (125.4 g, 19.84% Y ₂ O ₃ , 22.69% HCl) in aqueous hydrochloric acid and europium oxide (10.46 g, 19.49% Eu ₂ O _{3 in} aqueous hydrochloric acid) were added. (20.83% HCl) was added. The resulting clear solution was stirred for 30 minutes.

To the above solution was added dropwise 119.4 g of 30% sodium hydroxide solution (0.8955 mol NaOH) dropwise over 35 minutes while maintaining the temperature of the solution at 25 ° C. The resulting colorless solution, pH 9.2, was diluted with deionized water to a total weight of 1200 g.

The diluted colorless solution was combined with a slurry of 73.1 g of barium sulfate (Blanc Fix Micro Grade, precipitated barium sulfate, commercially available from Sachtleben Corp.) in 300 mL of deionized water. The barium sulfate used in this example.

- 29 specific surface area 2.6 m ² / g. The resulting mixture was stirred overnight. A piston pump was added to the slurry over a period of one hour with 21.1 g of 30% w / w sodium hydroxide solution (0.1553 mole NaOH) while maintaining the slurry temperature at 25 ° C. The white slurry, pH 11.4, was then heated at 100 ° C under reflux for 6 hours.

The white slurry was cooled to 25 ° C (pH 10.6), a portion of the slurry was filtered and washed with 1000 mL of deionized water. The filter cake was dried at 120 ° C to give 59.2 g of a white solid with a specific surface area of 6.3 m ² / g. A portion of the resulting white solid was crushed in a mortar and calcined in air at 1100 ° C to give a powder with the following characteristics.

Relative intensity after calcination Particle size before calcination (pm) Inductively coupled plasma (ICP) analysis D90 D50 D10 Y ₂ O ₃ % Eu ₂ O ₃ % Na ₂ O% 1.50 4.8 1.6 0.52 21.81 1.89 0.10

Referring to the drawings, Figure 1 shows a commercially available fluorescent image taken at 600x magnification using an optical microscope. For the measurement of R (l) data in the table above, this light powder was used as a reference standard. The commercially available material corresponds to a homogeneous phosphor containing 5% by weight of Y ₂ O ₃ doped with Eu ₂ O _{3 and} marketed under the trade name Sylvania Type 2340 (manufactured by GTE). Figure 2 is a view of a portion of the powder of Example 1 taken under an optical microscope at 600x magnification, and Figure 3 is a

Figure 2 is a photomicrograph of the powder shown in Figure 2 with an optical microscope at 1000x magnification. The images shown in Figures 1 and 2 were taken with a NIKON type optical microscope equipped with 60X ELWD (wide focal length) lenses, a small sample of powder was placed on a glass plate, and the powder was immersed in a drop of oil of refractive index n = 1.54. A cover glass was placed on each sample and lightly dispersed to disperse the powder. The image shown in Figure 3 was taken with a microscope as described above using a 100x magnification oil immersion lens immersed in an oil droplet on top of the cover glass.

Figure 1 shows a commercially available uniform light powder having a particle size of 2 to 15 µm. 2 and

Figure 3 shows BaSO ₄ particles of 3-20 µm coated with crystals of Eu: Y ₂ O ₃ phosphor. The light contours of the particles shown in Figures 2 and 3 generally correspond to BaSO ₄ , while the relatively dark spots are Eu: Y ₂ O ₃ crystals with which the surface of the BaSO ₄ particles are coated.

Example 2

This example describes a process for the preparation of a powder containing barium sulfate coated with 0.76% Eu ₂ O ₃ and 9.24% Y ₂ O ₃ using the chelate process.

In a 1 L flask under nitrogen atmosphere, at 25 ° C (270 mL) deionized water and 20.4 g (0.1507 mole).

- We bring in 31 D, L-malic acid. While stirring, a solution of yttrium oxide (62.2 g, 20% Y ₂ O ₃ , 22.57% HCl) in aqueous hydrochloric acid and a solution of europium oxide (5.1 g, 20% Eu ₂ O in aqueous hydrochloric acid) was added. ₃ , 20.72% HCl) was added while maintaining the temperature at 25 ° C. The resulting solution was stirred for 10 minutes. Aqueous ammonium hydroxide solution (33.2 g, 29.2% NH ₃ , 0.5692 mol) was then added dropwise over a period of 40 minutes at 25 ° C. A colorless solution is obtained having a pH of 8.0. The solution was then diluted with deionized water to a total weight of 600 g.

In 500 ml deionized water, 90 g of barium sulfate (Blanc Fixe Micro Grade Precipitated Barium Sulphate, commercially available from Sachtleben Corp.), previously calcined at 900 ° C for 1 hour, was converted into a slurry. Aqueous ammonium hydroxide (40 g, 29.2% NH ₃ ) was added to the sulfate slurry with stirring at 25 ° C. The slurry was stirred overnight. The slurry was then heated to 91 ° C and 446.1 g of the colorless solution of yttrium-eurium-chelate described above was added over 2.5 hours. The resulting slurry was refluxed for a further 6 hours at 106 ° C.

After cooling to 0 ° C, a white slurry is obtained having a pH of 8.6. The white slurry was filtered and the filter cake washed with 16 L of deionized water. Drying of the filter cake gave 107.8 g of a white solid having a specific surface area of 1.3 m ² / g and a particle size distribution of D90: 8.49 µm, D50: 3.00 µm and D10: 0.94 µm. pm. A portion of the solid was pulverized in a hammer mill and calcined at 1200 ° C for 1 hour. The resulting white powder had a specific surface area of 0.6 m ² / g and a particle size distribution of D90: 18.1 µm, D50: 7.13 µm and D10: 1.62 µm.

Figure 4 is a portion of the powder of Example 2 taken under an optical microscope at 600x magnification. Figure 4 shows a coating of relatively small powder crystals on BaSO ₄ particles.

Example 3

This example describes a process containing barium sulfate. 0.76% Eu ₂ O ₃ and 9.24% Y ₂ O ₃ coated powder using the oxalate process.

1500 ml of deionized water (90 g) were treated with barium sulfate and the slurry was stirred at 25 ° C for two days. (Barium sulphate, precipitated barium sulphate under the trade name Blanc Fixe Micro Grade, manufactured by Sachtleben Corp.) The slurry is then heated to 91 ° C.

Solution containing yttrium oxide in aqueous hydrochloric acid solution (46.2 g, 20% Y ₂ O ₃ , 22.57% HCl) and solution containing europium oxide in aqueous hydrochloric acid solution (3.79 g, 20% Eu ₂ O ₃ , 20.72 HCl) and 50 mL of deionized water at 25 ° C. Another solution was prepared by dissolving 17.9 g (0.1422 mol) of anhydrous oxalic acid in 46 ml of deionized water at 60 ° C. The barium sulfate slurry is heated to 91 ° C and the two solutions described above are added to the sulfate slurry simultaneously for two hours. The resulting slurry was heated at reflux to 102 ° C and maintained at this temperature for 6 hours.

After cooling to <RTIgt; C, </RTI> a white slurry was obtained which was filtered and the filter cake washed with 10 L of deionized water. The filter cake was dried at 120 ° C to give 106.6 g of a white solid with a specific surface area of 3.1 m ² / g. A portion of the powder was calcined in air at 1100 ° C for 1 hour to give a white powder.

Figure 5 is a photograph of the powder prepared according to Example 3 using an optical microscope at 1000x magnification. Figure 5 shows a BaSO ₄ particle substantially uncoated with light powder crystals and an adjacent particle that is substantially completely covered with light crystals.

Figure 6 is a graphical representation of the R (l) spectra, where R (l) is plotted against the emission wavelength (on the x-axis), the conventional powder shown in Figure 1, and 1-3. . for example powders. The curves A-C of FIG. corresponds to the R (1) spectra emitted by the powders prepared according to Example 1 and the curve D is the typical R (1) of the commercially available fluorescent powder shown in FIG. AR (1) spectra or curves were recorded on an SLM-8000 spectrometer using the following settings: excitation resolution = 4 nm, emission resolution = 4 nm, increment = 0.2 µm, integration time = 0.1 s, measured function = C / B, Channel C gain = 10, C High Voltage = 420, Channel B gain = 100, B High Voltage = 505. The AD curves show that the powders according to the invention exhibit RH values in the range of 65 to 70 % is available «« * 9 9 9 Β 9 «« «•

- 34 significantly less luminescent material.

Example 4

This example describes a process for the preparation of a phosphor containing barium sulfate coated with 0.38% europium and 9.62% YVO ₄ .

A solution of 15.7 g of 37% hydrochloric acid and 2.4 g of deionized water (7.67 g, 0.0566 mol) was dissolved in D, L-malic acid. The solution is heated to 45 ° C and 5.16 g (0.0283 moles of 99.9% V ₂ O ₅ ) vanadium pentoxide are added over a period of 1 hour at 45-70 ° C. a dark blue solution is obtained.

In another beaker, D, L-malic acid was dissolved in 200 mL of deionized water (10.5 g, 0.0775 mol). The solution containing solution comprising yttria almasavoldathoz maintained at 25 ° C with stirring in aqueous hydrochloric acid (31.9 g, 20% Y2O3, 22.57% HCl) and europium oxide in aqueous hydrochloric acid (2.62 g, 20% Eu ₂ O ₃ , 20.72% HCl) is added. The blue vanadium solution described above is poured into the solution with stirring with 40 ml of deionized water. Sodium hydroxide solution (65.1 g, 30% NaOH, 0.4883 mol) was added dropwise to the stirred solution at 25 ° C. This gave a green-blue chelate solution having a pH of 8.0, which was diluted to 600 g with the addition of deionized water.

A portion of the green-blue chelate solution (weighing 500 g) was added to 500 g of deionized water in a slurry containing 90 g of barium sulphate granulate [precipitated barium sulphate, type F]. (Manufactured by Sachtleben Corp.), previously calcined at 200 ° C and treated with 10% hydrochloric acid]. To the resulting slurry was added sodium hydroxide solution (23.3 g, 30 wt% NaOH, 0.1748 mol) at 25 ° C for 30 minutes. The slurry, pH 11.8, was refluxed for 8 hours at 101 ° C. After cooling to 25 ° C, a tan slurry of pH 12.2 is obtained which is filtered and the filter cake is washed with 10 L of deionized water. The filter cake was dried at 120 ° C to give 100 g of a cream-colored solid with a specific surface area of 17.7 m ² / g. A portion of the solid was calcined at 1100 ° C for 30 minutes to give a light yellow powder.

Figure 7 is an optical microscope image of the powder prepared according to Example 4 at 1000x magnification. Figure 7 shows a number of BaSO ₄ particles of various sizes with varying amounts of Eu: YVO _{4 light} crystals deposited.

Figure 8 is a graphical representation of the R (l) spectra, where R (l) is plotted against the emission wavelength (on the x axis), a portion of the powder produced in Example 4, and is commercially available. YVO ₄ containing 4% by weight of Eu ₂ O ₃ (Sylvania 2390, manufactured by GTE). In Figure 8, curve E corresponds to the R (l) values of the powder of Example 4, while curve F corresponds to the R (l) values of the Sylvania 2390 powder. The R (1) values were determined using a SLM-8000 spectrometer, which was used essentially with the setting described in Example 3. Figure 8 shows that the R (1) values for the dust produced in Example 4 correspond to 45-60% of those available for commercially available fluorescent dyes.

Example 5

This example describes a process for the preparation of a Y ₂ O ₃ : Eu phosphor composition on a BaSO ₄ substrate by a dry process.

One of the two essentially dry powders used in this example is BaSO ₄ (Blanc Fixe Micro Grade, commercially available from Sachtleben Corp.), previously calcined at 900 ° C for 1 hour and then milled in a hammer mill. europium doped yttrium oxalate powder, which is prepared essentially by the oxalate process described in Example 3 except that the oxalate powder is not separated into the core particles.

Oxalate (g) is dry mixed with 15 g of BaSO _{4 in an} alumina crucible and calcined at 1200 ° C for 1 hour. The final composition of the resultant fluorescent material is essentially Y ₂ O ₃ : Eu (5) / BaSO ₄ , which corresponds to a 16% by weight, 5 mol%, europium doped yttrium oxide coating on the barium sulfate particles. The R (1) values for the sample of the powder prepared according to Example 5 were determined essentially as described in Example 1, where the resulting peak was 1.64.

Example 6

This example describes the preparation of a powder containing barium sulfate particles in which the particles are oxalate-containing.

coating with 1.48% Eu ₂ O ₃ and 8.52% Y ₂ O ₃ .

In this example, Blanc Fixe Type N (precipitated barium sulfate, manufactured by Sachtleben Corp.) is used as barium sulfate particles. The barium sulfate was calcined at 700 ° C for 1 hour before coating and ground in a hammer mill. The calcined barium sulfate was treated as a slurry in 4% aqueous hydrochloric acid at 60 ° C for 1 hour, then washed with deionized water and dried at 100 ° C.

A sample of dried barium sulfate (90 g) was slurried with 1500 mL of deionized water and stirred overnight at 25 ° C. The slurry is then heated to 90 ° C.

A first solution is prepared by diluting aqueous hydrochloric acid solution (42.6 g, 20% Y ₂ O ₃ , 22.57% HCl) in 50 ml deionized water at 25 ° C and aqueous hydrochloric acid solution (7 38 g, 20% Eu ₂ O ₃ , 20.72% HCl). A second solution was prepared by dissolving 17.3 g (0.1384 mol) of anhydrous oxalic acid in 46 ml of deionized water at 60 ° C. Solutions 1 and 2 are added simultaneously to the barium sulfate slurry described above for two hours while maintaining the temperature of the reaction mixture at 90 ° C. The resulting white slurry was heated at reflux for 6 hours (102 ° C).

After cooling to 0 ° C, the white slurry was filtered and the filter cake was washed with 4 L of deionized water. The filter cake was dried at 120 ° C to give 108.9 g of white color

38 solids were obtained having a specific surface area of 1.2 m ² / g and a particle size distribution of D90: 9.24 pm, D50: 4.99 pm and D10: 1.96 μπι.

A portion of the dried white powder was calcined in air at 1200 ° C for 10 minutes to give a white powder having a specific surface area of 0.32 m ² / g and a particle size distribution of D90: 28.9 µm, D50: 9.91. pm and D10: 2.21 pm.

Figure 9 is a photograph of the powder prepared according to Example 6, with an optical microscope at 600x magnification, under crossed nicol prisms, with an immersion oil having a refractive index of 1.64. Figure 9 shows two large, double-refractive BaSO ₄ grains on a black background with sharp white light. The relatively large particle has a less compact coating consisting of Eu: Y ₂ O _{3 light} crystals, while the smaller particle has a higher density of Eu: Y ₂ O _{3 light} crystals.

Figure 10 is a photograph taken from the powder of Figure 9 using an optical microscope, except that the image of Figure 10 was taken with non-crossed nicol prisms. As the refractive index of the immersion oil is substantially the same as that of BaSO ₄ , in Figure 10 the BaSO ₄ particles are substantially invisible and only relatively small and dark powder crystals are clearly visible. The luminous crystals are more visible in Figure 10, since the refractive index of Eu: Y ₂ O ₃ is significantly greater than 1.64.

The R (l) values of the powder shown in Figures 9 and 10 were determined according to the procedure described in Example 1. Figure 11 shows the powder shown in Figure 9 and Figure 10, and the powder shown in Figure 1.

- A graphical representation of the R (l) spectrum of 39 commercially available powders, depicting R (l) as a function of emission wavelength (on the x-axis) (on the y-axis). The curve H of Fig. 11 is the powder shown in Fig. 1, while the curve G corresponds to the R (l) values of the powder prepared according to Example 6. The R (l) values were determined using the SLM-8000 spectrometer used in the settings described in Example 3.

Figure 11 illustrates that the composition of the present invention achieves a peak R (1) of about 2.0, which is comparable to that of commercially available fluorescents.

Example 7

A) This part of the example illustrates that the powder coated fluorescent powder of the present invention provides improved R (1) values relative to the uncalcined, mechanically prepared mixture of BaSO ₄ and Eu: Y ₂ O ₃ .

A mixture of commercially available BaSO ₄ (g) and 1 g (Sylvania 2340) of Eu: Y ₂ O ₃ (manufactured by GTE) is prepared by dry mixing (shaking in a glass ampoule). It contains 20% by weight of light powder based on the total weight of the powder obtained. Before mixing with the BaSO ₄ powder, the peak R (l) of Eu: Y ₂ O _{3 is} 1.96 and the peak R (l) of the mixed powder is 0.54.

For comparison, a luminescent composition of the invention containing 5 mole% Eu: Y ₂ O ₃ coating on BaSO ₄ powder was prepared as described in Example 1. The coating represents 20% by weight based on the total weight of the coated phosphor. After calcination in air at 1100 ° C for 4 hours, the powder-coated product of the present invention has a peak R (l) of 1.57. Based on the measured values of R (1), the intensity of the calcined composition according to the invention, even in the case of the same mass of the phosphor present in the dry mechanical mixture, is significantly higher than the R (1) value of the technical mixture.

B) This part of the example illustrates the calcination and acid treatment of BaSO ₄ used in a dry, mechanically blended mixture of BaSO ₄ and Eu: Y ₂ O ₃ .

4200 g of a commercially available BaSO ₄ powder (Type N, manufactured by Sachtleben Corp.) was calcined in air at 700 ° C for 1 hour. The calcined powder is then granulated using a Brinkmann-type mill with a 9.8 mm mesh screen. The granulated powder is then washed as a slurry in 10% HCl solution for 1 hour. The slurry powder is washed with deionized water until the conductivity of the filtrate is less than 50 pS.

3.6 g of the above acid-washed BaSO ₄ and 0.4 g of a commercially available powder (type 2340) of Eu: Y ₂ O ₃ (manufactured by GTE) are prepared mechanically. To do this, rotate the small glass vial containing the two powders for 5 minutes. The R (1) value for a mixture containing 10% by weight of Eu: Y ₂ O ₃ is 0.65. This represents a significant improvement over the 20% w / w Eu: Y ₂ O ₃ mixture described in Example 7A, wherein R (1) is 0.54. This part of the example illustrates that calcined and acid washed core particles have a higher R (1) value even when using only half of the Eu: Y ₂ O ₃ -containing fluorescent powder.

A portion of the above mixture is then calcined in air at 1200 ° C for 30 minutes, after which R (1) is 1.38. Commercially available type 2340 (GTE) homogeneous phosphor has an R (l) of 2.0. Figure 12 is a 600-fold optical microscope image showing larger Eu: Y ₂ O ₃ crystals as agglomerates or individual crystals while relatively small (less than 2 µm) crystals are present on the surface of BaSO ₄ particles. embedded. The coating is characterized in that the relatively small, substantially free of crystals BaSO cover uneven or random crystalline coatings on BaSO ₄ particles in amounts greater than ₄ -szemcséktől. In contrast to the previous examples, where calcination of the coated powder is used to crystallize and activate the phosphor, in this example the luminescent material consists of activated crystals and the calcination is used to increase R (1).

Example 8

This example describes a process for preparing a luminescent composition containing 2.04% Eu ₂ O ₃ and 24.86% Y ₂ O ₃ coated with barium sulfate.

In 1500 ml of deionized water (73 g), a slurry of barium sulphate was formed, which was stirred overnight at 25 ° C under a nitrogen atmosphere. In this example, the barium sulfate used is precipitated barium sulfate (Blanc Fixe Micro Grade) from Sachtleben Corp.. The barium sulfate slurry is then heated to 90-95 ° C.

• 42 aqueous hydrochloric acid solution containing yttrium oxide (125.3 g, 19.48% Y ₂ O ₃ , 22.69% HCl) and aqueous hydrochloric acid containing europium oxide (10.46 g, 19.49% Eu ₂ O _3). (20.83% HCl). These solutions were added simultaneously with 82.5 g (0.6189 mol) of a 30% w / w aqueous sodium hydroxide solution to the barium sulfate slurry while maintaining the pH of the slurry at 8.0-8.5. The resulting white slurry, pH 8.2, was refluxed for 6 hours at 100 ° C.

The white slurry was cooled to 25 ° C (pH 9.6), then half of the slurry was filtered and washed with 1000 mL of deionized water. The resulting filter cake was dried at 120 ° C to give 49.8 g of a white solid with a specific surface area of 10.9 m ² / g. A portion of the white solid was pulverized in a mortar and calcined in air at 1100 ° C.

The R (1) value of the powder sample is determined as described above. The peak intensity measured is 1.09.

The other half of the slurry was filtered and washed with 15,000 mL of deionized water. The filter cake was dried at 120 ° C to give 50.8 g of a white solid with a specific surface area of 17.2 m ² / g. A portion of the white solid was pulverized in a mortar and calcined in air at 1100 ° C. The powder sample has a measured R (l) of 1.05.

Example 9

This example describes a process for preparing a luminescent composition containing 1.48% Eu ₂ O ₃ and 8.52% Y ₂ O ₃ coated barium sulfate.

• ·

A 1 L flask was charged with deionized water and 29.6 g (0.2181 mole) of D, L-malic acid under nitrogen (270 mL) and kept at 25 ° C. The flask with stirring kelátoldatot comprising yttrium oxide in aqueous hydrochloric acid (85.2 g, 20% Y2O3, 22.57% HCl) and aqueous hydrochloric acid solution containing europium oxide (14.8 g, 20% Eu ₂ O _3, 20.72 % HCl) was added. The resulting substantially clear solution was stirred at 25 ° C for 15 minutes.

To the above solution was added dropwise aqueous potassium hydroxide solution (146.4 g, 30% KOH, 0.7827 mol) over 40 minutes while maintaining the temperature at 25 ° C. The resulting colorless solution, pH 8.0, was diluted with deionized water to a total weight of 600 g.

Barium sulphate slurry was formed in 483 ml deionized water (87 g) and kept at 25 ° C under a nitrogen atmosphere. Blanc Fixe Micro Grade Barium Sulphate (manufactured by Sachtleben Corp.) was previously calcined at 800 ° C for 1 hour after addition of 30% potassium chloride, extracted with 10% hydrochloric acid, washed with deionized water and dried. To the slurry of barium sulfate was added aqueous potassium hydroxide solution (21.7 g, 30% KOH, 0.12 mol).

A portion (14.5 g) of the above-described yttrium-eurium-chelate solution is added to the slurry over 2 hours at 25 ° C. The slurry was stirred for two days, then heated to 91 ° C and 275.5 g of a solution of yttrium-eurium-chelate was added over 75 minutes. The resulting white slurry was refluxed for 6 hours at 101 ° C.

After cooling to · ° C, a white slurry of pH 12.1 is obtained. The slurry was filtered and the filter cake washed with 17 L of deionized water. The filter cake was dried to give 99 g of a white solid with a specific surface area of 12.7 m ² / g having a particle size distribution of D90: 9.39 µm, D50: 5.99 µm and D10: 4.06 µm.

A portion of the white solid was calcined for 30 minutes at 1200 ° C. The resulting white powder has a specific surface area of 0.75 m ² / g and has a particle size distribution of D90: 10.8 µm, D50: 6.28 µm and D10: 3.05 µm. The R (1) value of the powder sample, measured as described above, is 1.14.

Repeating the above example, except that all operations are carried out in air instead of nitrogen, the resulting white powder has an R (1) value of 1.41.

Example 10

This example describes the preparation of a luminescent composition comprising a Eu: Y ₂ O ₃ coating on a CaO substrate.

The two raw materials used are CaCO ₃ (manufactured by JT Baker) and yttrium oxalate powder doped with europium. 1 g of CaCO ₃ is dry mixed with 0.15 g of yttrium oxalate doped with 0.15 g of europium (containing 5 mole% Eu ₂ O ₃ ) and then calcined in air at 1150 ° C for 30 minutes. The calcined composition is Eu (5): Y ₂ O ₃ / CaO (93), which represents the formation of 7% by weight, 5 mol% of yttrium oxide on CaO surface.

During calcination, CaCO _{3 is} believed to be converted or decomposed into CaO and CO ₂ reaction products. As a result45, the core particles contain CaO. It can also be assumed that when the CaO core particles are exposed to air, the CaO is at least partially converted to Ca (OH) ₂ , which in part leads to the formation of CaCO ₃ .

The R (1) value for the above composition, as determined by the above procedure, is 0.9. The composition has a measured particle size distribution of D10: 2.4 µm, D50: 8.6 µm and D90: 288 µm.

Example 11

This example describes a process for preparing a luminescent composition comprising Eu: Y ₂ O ₃ deposited on CaO core particles.

The two raw materials used are Europium-doped Yttrium Oxalate Powder and CaCO ₃ (manufactured by JT Baker), previously calcined at 900 ° C for 1 hour. As a result of the calcination, most of the CaCO ₃ is likely to undergo conversion or decomposition to form CaO containing trace amounts of Ca (OH) ₂ and CaCO ₃ .

Dry 1 g of calcined CaO in a glass ampoule is mixed with 0.25 g of yttrium oxalate doped with europium (5 mol% Eu ₂ O ₃ ) and calcined in air for 30 minutes at 1150 ° C. The resulting composition is approximately Eu (5): Y ₂ O ₃ / CaO (89), which indicates that the CaO surface produces 11% by weight of a 5% by weight of yttrium oxide coating with europium oxide. The composition has a measured R (l) of 1.2 and has a particle size distribution of D10: 0.94 µm, D50: 0.39 µm and D90: 11.6 µm.

Example 12

This example describes a process for preparing a light composition comprising an Eu: Y ₂ O ₃ coating on a surface of a MgO substrate.

The two raw materials are MgO (manufactured by Alpha Company) and europium-doped yttrium oxalate powder. 0.8 g of MgO is mixed with 0.2 g of yttrium oxalate (5 mole% Eu ₂ O ₃ ) doped with europium oxide in a wet process. The oxalate was prepared according to the procedure described in Example 3. Mix the substances wet with 5-10 g deionized water by shaking in a small glass vial for 5 minutes. The mixture was then placed in an alumina boat and calcined at 1150 ° C for 30 minutes.

The calcined composition is Eu (5): Y ₂ O ₃ / MgO (88.5). The composition corresponds to a coating of 11.5% by weight on MgO core particles, which is 5 mol% of yttrium oxide doped with europium oxide.

The sample prepared as above has an R (l) value of 0.6 and a particle size distribution of D10: 7 μιη, D50: 12 μιη and D90: 22 μιη.

Example 13

This example describes a process for producing a two-component phosphor comprising green phosphor particles coated with a red light emitting powder which, when illuminated by a UV light source, produces visually perceived white light.

The two sources of raw materials (5 mol% Eu ₂ O ₃ ) are yttrium oxalate powder, doped with europium oxide, and commercially available green light type GTE 2291 (Ce.TbjMgAI, 0 ₁₉₎ . Prepared according to the procedure of Example 3. 1.6 g of oxalate are dry mixed with 0.4 g of GTE 2291 powder by shaking in a glass ampoule for 5 minutes.

The powder mixture was placed in an alumina boat and calcined in air for 30 minutes at 1150 ° C. The composition of the calcined mixture was Eu (5): Y ₂ O ₃ / (Ce, Tb) MgAI ₁ · ₁₉ (32.4). The mixture (Ce.TbjMgAl !! θ ₁₉₎ applied to 67.6% by weight, 5 mol% of yttrium oxide coated with europium oxide.

The luminescent properties of the calcined mixture are tested with a commercially available handheld UV lamp which emits low wavelength light. The calcined powder becomes visually visible when illuminated by UV light from a handheld UV lamp.

The resulting powder has a particle size distribution of D10: 1.5 pm, D50: 5 pm and D90: 12 pm, while the GTE 2291 has a particle size distribution of D10: 4.5 pm, D50: 9 pm and D90: 15 pm. The sample prepared as described above has a measured R (l) value of 1.2 at 612 nm, which is the red emission line for the primary Eu: Y ₂ O ₃ and 0.9 at 543 nm, which is the primary emission line for GTE 2291.

Example 14

A) This example illustrates a process for mixing red light emitting coated barium sulfate (Eu: Y ₂ O ₃ / BaSO ₄ ) with green emitting light 48 powder to produce a composite luminescent material that emits visually white light at short wavelength UV light . Calcined and acid washed barium sulfate core particles were prepared according to the procedure described in Example 3 to give Eu (10): Y ₂ 0 ₃ / BaSO ₄ (90). The powder obtained has a measured R (l) of 2.0. This powder serves as the red component of the mixture of the two powders. The green component is a commercially available product GTE 2291 (Ce.TbJ.MgAl !! θ ₁₉₎ .

A dry mixture of 1.8 g of the red component and 0.2 g of the green component is prepared by shaking the two powders in a glass vial for 10 minutes. The resulting dry mixture contained 90% by weight of the red component, corresponding to 1.35% by weight of Eu ₂ O ₃ and 7.65% by weight of Y ₂ O ₃ . According to visual observations, the mixture emits white light when illuminated by a short wavelength UV light from a handheld UV lamp.

B) For comparison, a second dry blend is prepared using the commercially available GTE 2340 light powder (Eu: Y ₂ O ₃ ) as the red component of the blend. The GTE 2340 sample contained 4.6% by weight of Eu ₂ O ₃ and 95.4% by weight of Y ₂ O ₃ according to ICP analysis.

A mixture of 0.5 g of GTE green component and 1.5 g of GTE red component is prepared as described in Part A of this example. The mixture contained 75% by weight of red light powder, corresponding to 3.45% by weight of Eu ₂ O ₃ and 71.55% by weight of Y ₂ O ₃ . The resulting mixture is visually observed under short-wavelength UV illumination to determine that it emits essentially the same white light as that observed in Example 14A.

This example illustrates that a luminescent composition emits essentially the same white light as a coated light emitting red light instead of a homogeneous Eu: Y ₂ O ₃ powder [Eu (10): Y ₂ 0 ₃ / BaSO ₄ (90)]. contain. However, the luminescent composition of the present invention exemplified by this example requires a significantly smaller amount of Eu ₂ O ₃ and Y ₂ O ₃ , so that the coated powder of this example can significantly reduce the cost of the powder. Further cost reduction is achieved by using 15% by weight of Tb ₂ O ₃ green light powder according to Example 14A).

Example 15

In this example, a composition comprising an Eu: Y ₂ O ₃ coating deposited on CaO particles has a cathode luminescence property.

Eu (10): Y ₂ O ₃ / CaO luminescent composition was prepared according to the procedure of Example 11, except that the starting material was 10 mole% of yttrium oxalate doped with the oxalate method of Example 3. port. A slurry of 0.8 g of CaO, 0.2 g of yttrium oxalate doped with europium oxide and 5 ml of deionized water was prepared by rotating the starting materials in a small glass vial for 5 minutes. The resulting slurry was poured into an alumina boat and calcined at 1200 ° C for 30 minutes. The final composition is Eu (10): Y ₂ O ₃ / CaO (89).

Samples of the above-described powder and commercially available fluorescent powder (GTE 2340 Eu: Y ₂ O ₃ ) were placed separately into a 25.4 mm square stainless steel die and pressed for 2 minutes in a Wabash press at 78.5 kN. The pressed powder sample is then used to determine whether it exhibits cathode luminescence. The pressed powder samples are individually mounted on a sample holder and placed in a Philips 515 scanning electron microscope. Each sample is examined with the scanning electron beam set at 25 kV, 400 pA and 100 nm. The cathode luminescence detectors inside the microscope are capable of detecting light in the range of 300-650 nm. For comparative qualitative determination of the cathode luminescence efficiency of the samples, black and white photographs of electron beam scanned samples are used. The degree of whiteness of the photograph is believed to be directly correlated with the red luminescent emission, such as Eu: Y ₂ O ₃ at 611 nm wavelength, which appears to be visually equivalent for different samples.

Example 16

This example discloses a fluorescent (CaF ₂ ) -coated particulate composition comprising a Y ₂ O ₃ coating with a European addition.

• ·

- 51 100 g of commercially available calcium fluoride (99.95% purity) (Johnson Matthey, manufactured) were placed in an alumina boat and calcined at 100 ° C in air for 30 minutes. The calcined powder is granulated and passed through a Brinkmann-type mill using a 0.5 mesh screen. Visual observation indicates that the powder has a slightly gray metallic color, which is obviously due to metal contamination by the granulator.

The granulated and sieved powder was washed with 5% HCl solution for 30 minutes and then with deionized water. The washed powder was dried in an oven at 120 ° C. Upon visual inspection, the dried powder appears to be white and substantially free of agglomeration.

Dry mechanical stirring was carried out using 3.2 g of calcined fluorite and 0.8 g of a homogeneous oxalate having the composition (Eu [10], Y) ₂ (C ₂ O 4) 3, where [10] 10 moles indicates%. The homogeneous oxalate in its material was prepared according to the procedure described in Example 3. Mix the two powders dry by rotating in a glass vial for 15 minutes. The mixed powder was placed in an alumina boat and calcined in air at 1100 ° C for 1 hour.

The composition of the calcined product is Eu (10): Y ₂ O ₃ / CaF ₂ (88.5), which corresponds to 11.5% by weight, 11 mol% of yttrium oxide coating on calcined CaF ₂ core particles. This powder has a measured R (l) value of 1.98.

This example is repeated except that the homogeneous oxalate containing only 5 mol% of Eu ₂ O ₃ -O is used. Eu (5): Y ₂ O ₃ / CaF ₂ (88.5), R (1) found 1.81.

The above examples illustrate that the luminescent composition of the present invention can actually be used for a variety of applications; especially in applications where it is desirable to reduce the cost of light, such as plasma display devices (PDPs). In particular, the composition of the present invention can reduce the cost of the phosphor when used in the PDP processes and apparatus disclosed in U.S. Patent Nos. 08 / 109,974 and 08 / 109,879, which documents are incorporated herein by reference. The above documents refer to variants of PDP which include a plurality of salt-shaped electrodes arranged in a matrix, a point-to-point or pixel region at each intersection of the electrodes, and a fluorescent film formed above each discharge region, wherein the fluorescent film emits light when excited. The luminescent composition of the present invention can be mixed into a paste or slurry, which can be used to form a fluorescent film used in the discharge regions described in the aforementioned patents.

A better understanding of this aspect of the invention is provided in Figure 13. Fig. 13 shows a PDP having its separate glass substrates 1 and 2, its electrodes 3 extending laterally along the inner surface of the substrate 2 and extending longitudinally along the inner surface of the substrate.

- Has 53 electrodes 4. The intersections of the electrodes 3 and 4 form a discharge region. The ribs 5, arranged as a matrix, define pixel ranges whose arrangement provides a space between the substrates 1 and 2. The electrodes 3 are usually arranged on a dielectric layer 6 on the substrate 2. Another dielectric layer 7 placed above the electrodes 3 forms one end of the discharge space 8 which is filled with a suitable gas such as a mixture of neon and xenon. In some cases, a protective layer 9 is provided on the dielectric layer 7. In the grooves 11, a fluorescent film 10 is arranged so as to allow the ultraviolet light to be converted to visible light. While the fluorescent film 10 may be placed in the grooves 11 by any suitable means, the luminescent composition of the present invention may normally be incorporated into the grooves 11 as paste or slurry. Suitable luminescent compositions may include, for example, an effective amount of at least one of Zn ₂ SiO ₄ : Mn, (Y ₂ O ₃ : Eu), BaMg ₂ Al ₁₆ O ₂₇ , MgAI ₂ O ₁₆ (CeJb) and (Y, Gd) BO ₃ Eu. which was applied as a coating on core grains such as barium sulfate. The paste or slurry is prepared by mixing the luminescent composition of the invention with an effective amount of an organic carrier, such as a mixture of one or more commercially available polymers, plasticizers and solvents, such as those described in U.S. Patent Nos. 08/109,874 and 08/109,879. The ratio of the luminescent composition to the organic carrier in the paste should be sufficient to disperse the composition in the carrier and allow the grooves 11 to ·

- applying 54 pastes in substantially uniform layers. The organic component of the paste is removed by formation of a fluorescent film.

Certain aspects of the invention have been described in detail, but one skilled in the art will recognize that further embodiments and variations are possible within the scope of the appended claims.

Claims (33)

Claims Claims 1. A luminescent powder composition comprising particles of an inert core and at least one luminescent coating, wherein the combined coating comprises from 2% to 30% by weight of the total composition, wherein the inert core is alkaline earth metal sulfate, alkaline earth metal phosphate, alkaline earth metal. , calcium oxide, calcium carbonate and magnesium oxide. Composition according to claim 1, characterized in that the luminescent coating (Y ₂ O ₃ : Eu), (Y ₂ O ₂ S: Eu), (YVO ₄ : Eu), (Zn ₂ SiO ₄ : Mn). , (BaMg ₂ Al ₁₆ O ₂₇ : Eu), (SrB ₄ O ₇ : Eu), Ce _{0 65} Tb ₀ ^ MgAI ^ O ^, (ZnS: Cu), (ZnS: Ag), (MgWO ₄ ), barium - contains titanium phosphate, tin and europium activated alkaline earth metal ortho-diphosphates and antimony and / or manganese activated calcium halophosphates and (La, Ce, Tb) (PO ₄ ) ₃ : (Ce, Tb). Composition according to claim 1 or 2, characterized in that the inoculated core contains at least one ingredient selected from the group consisting of barium sulfate, calcium fluoride and calcium sulfate. Composition according to claim 1 or 2, characterized in that the coating comprises 5-20% by weight of the total weight of the composition and the core contains particles having an average diameter of 1.0-10 µm. Composition according to claim 1, characterized in that the core particles comprise a coating on the surface. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · - 56 · The composition according to claim 1, wherein 90% by weight of the core particles have a diameter of 0.1 D to 10.0 D, wherein D represents the average diameter of the particles. The composition of claim 1, wherein the core particles comprise calcium fluoride. A cathode ray tube comprising the luminescent powder composition of claim 1. Fluorescent lamp, characterized in that it comprises a luminescent powder composition according to claim 1. 10. A light emitting device comprising the luminescent powder composition of claim 1. 11. A fluorescent powder containing at least one luminescent material coated, calcined, inoculated core particles, wherein the luminous fluorescent material has at least 60% relative to the luminescent material of the inert core particles of an alkaline earth metal sulfate, an alkaline earth metal phosphate, containing at least one ingredient selected from the group consisting of calcium oxide, calcium carbonate and magnesium oxide. Composition according to claim 1 or 2, characterized in that the at least one coating is selected from the group consisting of cerium, terbium, tin (II), antimony (III), copper, silver or manganese as the activator and Y ₂ O as the starting material. ₃ , YVO ₄ , Sr ₂ P ₂ O ₇ , (Ca, Sr) ₅ (F, Cl) (PO ₄ ) ₃ , ZnS, Y ₂ O ₂ S, MgAI 4 O ₂ g and BaMg ₂ Al ₂ O 7 contains one ingredient. The composition according to claim 1 or 2, wherein the core and the at least one coating are substantially free of poisons. • 57 · The composition of claim 1, wherein the at least one luminescent coating comprises successively applied coatings. 15 powder composition, characterized in that it comprises at least one particulate component alkállföldfém sulfate, alkaline earth metal phosphate, metal oxide and alkaline earth metal fluoride, wherein the particles have a diameter of 0.5 to 10 pm, and the core at least one coating _(Y2 O ₃ : Eu), (Y ₂ O ₂ S: Eu), (YVO ₄ : Eu), (Zn ₂ SIO ₄ : Mn), (BaMg ₂ AI ₁₆ O ₂₇ : Eu), (SrB ₄ O ₇ : Eu) ), Ceo esTbg ^ MgAI ^ O ^, (ZnS: Cu), (ZnS: Ag), (MgWO ₄ ), barium titanium phosphate, tin and europium activated alkaline earth metal ortho- and diphosphates and antimony and / or manganese containing at least one ingredient of activated calcium halophosphates and (La, Ce, Tb) (PO ₄ ) ₃ : (Ce, Tb). 16. A powder composition comprising at least one particulate component of an alkaline earth metal sulfate, an alkaline earth metal phosphate and an alkaline earth metal fluoride having a particle diameter of 0.5 to 10 µm and at least one coating of the core (Y ₂ O ₃ : Eu). ), (Y ₂ O ₂ S: Eu), (YVO ₄ : Eu), (BaMg ₂ Al _ie O ₂₇ : Eu), (SrB ₄ O ₇ : Eu), Ce _{O (65} Tbo, ₃₅ MgAli, Ο ₁₉ , (ZnS: Cu), (ZnS: Ag), (MgW0 ₄ ), barium titanium phosphate, tin and europium activated alkaline earth metal ortho and diphosphates and antimony and / or manganese activated calcium halophosphates and (La, Ce) , Tb) (PO ₄ ) ₃ : Contains at least one component of (Ce, Tb). A composition according to claim 15 or 16, characterized in that the amount of the at least one coating, which is illuminated by an energy source, - 58 · sufficient for 60% relative luminescence of the coating. 18. A plasma plasma display comprising a fluorescent film comprising a luminescent powder composition comprising particles of an inoculated core and at least one luminescent coating, wherein the coating is 2 to 30% by weight of the composition, barium sulfate core; containing at least one of the ingredients consisting of calcium sulfate, magnesium oxide, alumina and calcium fluoride, and having an average particle diameter of 0.5 to 10 µm. 19. A paste composition comprising a luminescent powder composition, wherein the luminescent powder composition comprises particles of an inert core and at least two successive luminescent coatings, wherein the coating is from 2% to 30% by weight, based on the total weight of the composition, 5-10 pm, wherein the paste composition also comprises an organic carrier which disperses the powder composition. 20. A powder composition according to claim 1, wherein the inoculated core comprises at least one ingredient selected from the group consisting of alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, and alkaline earth metal fluoride. 21. The powder composition of claim 1, wherein the luminescent coating comprises (Y ₂ O ₃ : Eu). 22. A powder composition according to claim 1, wherein the inert core barium sulfate and the luminescent coating are Zn ₂ SiO ₄ : Mn, (Y ₂ O ₃ : Eu), BaMg ₂ Al ₁₆ O ₂₇ , - 59 contains at least one ingredient of MgAlnO (fce.Tb) and (Y, Gd) BO ₃ : Eu. 23. The powder composition of claim 1, wherein the inert core barium sulfate and the luminescent coating are Zn ₂ SiO ₄ : Mn, (Y ₂ O ₃ : Eu), BaMg ₂ Al ₁₆ O ₂₇ , Mg Ce.Tb) and (Y, Gd) BO ₃ : Eu contain at least two components. 24. A process for preparing a luminescent composition comprising: a) preparing an aqueous or aqueous / organic slurry containing one or more inert particles, b) adding to said slurry a stable solution containing at least one metal chelate, c) raising the pH of the slurry to above 9, d) increasing the temperature of the slurry to at least 50 ° C and maintaining the slurry at this temperature on at least part of the surface of the granules with at least one water-containing metal oxide, e) recovering the granules, and f) calcining the particles at a temperature suitable for activating the water-containing metal oxide on their surface to form a luminescent composition. 25. A process for preparing a luminescent composition comprising: (a) preparing one or more inorganic slurries of alkaline earth metal sulphate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, alkaline earth metal fluoride or metal titanate, * t · ♦ »• · · · · · ·« ♦ «« - 60 b) adding oxalic acid to the resulting slurry, c) adding to the slurry an acidic or aqueous / organic solution of at least one metal, d) heating the slurry to a temperature sufficient to separate at least one metal oxalate salt on the surface of the inert particles, e) recovering the granules, and f) calcining the particles at a temperature suitable for activating the salt on their surface to obtain a luminescent composition. 26. A process for the preparation of a luminescent sulfide composition comprising: a) preparing an aqueous or aqueous / organic slurry containing one or more inert particles, b) adding to said slurry a stable solution containing at least one metal chelate, c) raising the pH of the slurry to above 9 and depositing at least a part of the surface of the granules with at least one water-containing metal oxide, d) adding a solution containing at least one sulfide salt to the slurry, and heating the slurry containing the salt to convert the aqueous metal oxide on the surface of the inert particles to sulfide, e) recovering the granules, and f) calcining the recovered particles and forming a luminescent sulfide composition on their surface to form a luminescent sulfide composition. • · · · · · · · · 9 a « - 61 27. A process for preparing a luminescent composition comprising: (a) mixing metal oxalate salts with particles containing at least one of inorganic alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, alkaline earth metal fluoride and metal titanate, and b) calcining the mixture at a temperature suitable for the formation of the activated luminescent material on the surface of the particles to form a luminescent composition. 28. A process according to claim 24 or 26, wherein the particles comprising at least one of the alkaline earth metal sulfate, alkaline earth metal phosphate, metal silicate, mixed metal oxides, alkaline earth metal fluoride and metal titanates are used. The method of any one of claims 24, 25 or 27, characterized in that, as activated luminescent material (Y ₂ O ₃ : Eu), (Y ₂ O ₂ S: Eu), (YVO ₄ : Eu), Zn ₂ SiO ₄ : Mn), (BaMg ₂ Al ₁₆ O ₂₇ : Eu), (SrB ₄ O ₇ : Eu), Ce _0i 65Tb ₀ 35MgAI ₁ (ZnS: Cu), (ZnS: Ag), (MgWO ₄ ). , barium titanium phosphate, tin and europium activated alkaline earth metal ortho- and diphosphates and antimony and / or manganese activated calcium halophosphates. 30. A 24-27. A process according to any one of claims 1 to 4, wherein the activated luminescent material has a mean particle size of 1.0 to 10 µm, comprising 5 to 20% by weight of the total weight of the composition. 31. A 24-26. A process according to any one of claims 1 to 3, wherein the slurry containing straight and branched chain alcohol or glycol (s) containing from 1 to 4 carbon atoms containing from 1 to 4 carbon atoms is used as water and water miscible organic liquid. 32. A process according to claim 24 or 25 wherein the chelating agent is α-hydroxycarboxylic acid (s), malic acid, citric acid, α-aminocarboxylic acid (s) and / or glycine. 33. A 24-26. A process according to any one of claims 1 to 3, characterized in that a luminescent composition substantially free of poisons is used.