EP0958244A1 - Compound with base of an alkaline-earth, sulphur and aluminium, gallium or indium, method of preparing same and use as luminophore - Google Patents

Compound with base of an alkaline-earth, sulphur and aluminium, gallium or indium, method of preparing same and use as luminophore

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Publication number
EP0958244A1
EP0958244A1 EP97912275A EP97912275A EP0958244A1 EP 0958244 A1 EP0958244 A1 EP 0958244A1 EP 97912275 A EP97912275 A EP 97912275A EP 97912275 A EP97912275 A EP 97912275A EP 0958244 A1 EP0958244 A1 EP 0958244A1
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EP
European Patent Office
Prior art keywords
compound according
compound
particles
powder
gallium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97912275A
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German (de)
French (fr)
Inventor
Denis Huguenin
Pierre Macaudiere
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhodia Chimie SAS
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Rhodia Chimie SAS
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Filing date
Publication date
Application filed by Rhodia Chimie SAS filed Critical Rhodia Chimie SAS
Publication of EP0958244A1 publication Critical patent/EP0958244A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G15/00—Compounds of gallium, indium or thallium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/68—Aluminium compounds containing sulfur
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G1/00—Methods of preparing compounds of metals not covered by subclasses C01B, C01C, C01D, or C01F, in general
    • C01G1/12—Sulfides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G15/00—Compounds of gallium, indium or thallium
    • C01G15/006—Compounds containing, besides gallium, indium, or thallium, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/62—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing gallium, indium or thallium
    • C09K11/621—Chalcogenides
    • C09K11/625—Chalcogenides with alkaline earth metals
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/64—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing aluminium
    • C09K11/641—Chalcogenides
    • C09K11/643—Chalcogenides with alkaline earth metals
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]

Definitions

  • the present invention relates to a compound based on an alkaline earth metal, sulfur and aluminum, gallium or indium, its preparation process and its use as a phosphor.
  • the fields of luminescence and electronics are currently experiencing significant developments. As an example of these developments, we can cite the development of cathodoluminescent systems for new visualization and lighting techniques.
  • One concrete application is that of replacing current television screens with flat screens. These new applications require phosphor materials with increasingly improved properties. Thus, in addition to their luminescence property, these materials are asked for specific characteristics of morphology or particle size in order to facilitate in particular their use in the desired applications.
  • alkaline earth thiogallates As phosphors, we know the alkaline earth thiogallates. These products are prepared from a mixture of salts or oxides of the various constituents by heating at high temperature in the presence of a fluxing agent. This method of preparation leads to large products with an often very large particle size distribution.
  • the object of the invention is to provide products of this type with a small particle size.
  • the compound of the invention corresponds to the formula AB2S4 (1) in which A represents one or more alkaline earths, B at least one element taken from the group comprising aluminum, gallium or indium, and it is characterized in that it is in the form of a powder with a residual oxygen content of at most 1.5%, more particularly at most 1%.
  • the compound of the invention corresponds to formula (1) and it is characterized in that it is in the form of a powder consisting of whole or unmilled particles, of average size at most 10 ⁇ m.
  • the invention also relates to a process for the preparation of such a compound which is characterized in that it comprises the following stages: - A solution or a suspension is formed comprising salts of elements A and B and optionally of the dopant;
  • the invention relates to the use as a phosphor, in particular in cathodoluminescence, of a compound as described above.
  • FIG. 1 is an RX spectrum of a compound according to the invention.
  • the compound of the invention is in the form of a powder and it corresponds to formula (1) AB2S4.
  • A is an alkaline earth (group Ha of the periodic table).
  • the periodic classification of the elements to which reference is made, here and for the entire description, is that published in the Supplement to the Bulletin of the French Chemical Society No. 1 (January 1966).
  • A may especially be strontium.
  • A can also be magnesium, calcium or barium.
  • B can be aluminum, gallium or indium. B can more particularly be gallium. According to a particular embodiment, the compound of the invention is a strontium thiogallate.
  • the invention also relates to the compounds in which A represents several alkaline earths.
  • B can represent a combination of at least two of the elements aluminum, gallium or indium.
  • the compound of the invention can comprise one or more dopants.
  • dopant is understood here to mean any element which can confer on the compound of formula (1) luminescence properties in a given application of the compound as a phosphor. Without wanting to be limited by a theory, one can think that the dopant comes in substitution for the alkaline-earth. The amount of dopant is usually at most 10 atomic% relative to the alkaline earth element.
  • this dopant can be chosen from divalent manganese, divalent rare earths and the group comprising trivalent rare earths in combination with an alkali.
  • the alkali can more particularly be sodium.
  • rare earth is meant the elements of the group constituted by yttrium and the elements of the periodic classification with atomic number included inclusively between 57 and 71.
  • the dopant can more particularly be europium II, ytterbium II or cerium III in combination with an alkali.
  • the compound of the invention is characterized by its low residual oxygen content.
  • This content is indeed lower than that of the compounds of the prior art.
  • This low residual oxygen level could be one of the reasons for the advantageous luminescence properties of the product of the invention.
  • this residual content is at most 1.5%, more particularly at most 1%. It is expressed by weight of oxygen relative to the total weight of the compound.
  • the compound of the invention is characterized by its morphology.
  • the compound consists of particles of average size of at most 10 ⁇ m.
  • the size and particle size characteristics are measured by the laser diffraction technique using a particle size analyzer of the CILAS HR 850 type (volume distribution).
  • This average size can more particularly be at most 5 ⁇ m and even more particularly at most 4 ⁇ m.
  • the particles whose size has just been given above are unmilled or whole particles.
  • the photos in scanning electron microscopy make it possible to show that these particles do not have the broken or broken appearance that particles which have undergone grinding have.
  • these photos show that these particles do not have, adhering to their surface, particles of much finer size, as may be the case after grinding where fine particles created by grinding can come s '' aggregate to larger particles.
  • the powder constituting the product of the invention may have been simply deagglomerated.
  • the compounds according to the first embodiment can of course have the particle size characteristics which have just been given above in combination with the characteristic of residual oxygen content.
  • those of the second embodiment can also have, in combination with the particle size characteristics, the oxygen content of the compounds of the first embodiment.
  • the compound has a narrow particle size distribution.
  • the dispersion index ⁇ / m is at most 0.7. It can more particularly be at most 0.6.
  • 6 is the particle diameter for which 16% of the particles have a diameter less than d 16 ; - d 50 is the average particle diameter.
  • the compounds of the invention may consist of particles of substantially spherical shape and whose diameter corresponds to the average sizes which have been given above.
  • Another characteristic of the compounds of the invention is that they are in the form of a pure crystallographic phase, this purity being able to be demonstrated by the X-ray diffraction spectra of the compounds.
  • this crystallographic phase is a cubic phase.
  • the process for the preparation of the compounds of the invention consists in forming a solution or a suspension comprising salts of elements A and B and optionally of the dopant.
  • Inorganic salts such as nitrates, sulfates or chlorides or even hydroxides are usually used.
  • Organic salts can optionally be used, but it is preferable in this case to use salts having few carbon atoms, such as carbonates or acetates.
  • the salts are put in a liquid medium, preferably water, to form a solution or a suspension.
  • the next step is to dry the previously prepared solution or suspension.
  • This drying is done by atomization.
  • spray drying is meant spray drying of the mixture in a hot atmosphere (spray-drying).
  • the atomization can be carried out by means of any sprayer known per se, for example by a spray nozzle of the sprinkler apple type or the like.
  • the spray-drying operation by means of a "flash" reactor, for example of the type developed by the Applicant and described in particular in French patent applications no. 2 257 326, 2 419 754 and 2 431 321.
  • the treating gases hot gases
  • the mixture to be dried is injected along a trajectory coincident with the axis of symmetry of the helical trajectories of said gases, which allows the quantity of movement of gases in the mixture to be treated.
  • the gases thus in fact perform a double function: on the one hand the spraying, that is to say the transformation into fine droplets, of the initial mixture, and on the other hand the drying of the droplets obtained.
  • the extremely short residence time (generally less than about 1/10 of a second) of the particles in the reactor has the advantage, inter alia, of limiting possible risks of overheating as a result of too long contact with the hot gases.
  • This consists of a combustion chamber and a contact chamber composed of a bicone or a truncated cone, the upper part of which diverges.
  • the combustion chamber opens into the contact chamber through a reduced passage.
  • the upper part of the combustion chamber is provided with an opening allowing the introduction of the combustible phase.
  • the combustion chamber comprises an internal coaxial cylinder, thus defining inside thereof a central zone and an annular peripheral zone, having perforations lying for the most part towards the upper part of the appliance.
  • the chamber comprises at least six perforations distributed over at least one circle, but preferably over several circles spaced axially.
  • the total surface of the perforations located in the lower part of the chamber can be very small, of the order of 1/10 to 1/100 of the total surface of the perforations of said internal coaxial cylinder.
  • the perforations are usually circular and have a very small thickness.
  • the ratio of the diameter of these to the thickness of the wall is at least 5, the minimum thickness of the wall being only limited by mechanical requirements.
  • a bent pipe opens into the reduced passage, the end of which opens in the axis of the central zone.
  • the gas phase animated by a helical movement (hereinafter called helical phase) is composed of a gas, generally air, introduced into an orifice made in the annular zone, preferably this orifice is located in the lower part of said area.
  • the gas phase is preferably introduced at low pressure into the abovementioned orifice, that is to say at a pressure of less than 1 bar and more particularly at a pressure included between 0.2 and 0.5 bar above the pressure existing in the contact chamber.
  • the speed of this helical phase is generally between 10 and 100 m / s and preferably between 30 and 60 m / s.
  • a combustible phase which can in particular be methane, is injected axially through the aforementioned opening in the central zone at a speed of approximately 100 to 150 m / s.
  • the combustible phase is ignited by any known means, in the region where the fuel and the helical phase are in contact.
  • the imposed passage of the gases in the reduced passage is done according to a set of trajectories confused with families of generators of a hyperboloid. These generators rest on a family of circles, small rings located near and below the reduced passage, before diverging in all directions.
  • the mixture to be treated is then introduced in the form of a liquid through the above-mentioned pipe.
  • the liquid is then divided into a multitude of drops, each of which is transported by a volume of gas and subjected to a movement creating a centrifugal effect.
  • the flow rate of the liquid is between 0.03 and 10 m / s.
  • the ratio between the momentum of the helical phase and that of the liquid mixture must be high. In particular, it is at least 100 and preferably between 1000 and 10000.
  • the amounts of movement at the reduced passage are calculated as a function of the inlet flow rates of the gas and of the mixture to be treated, as well as of the section of said passage. An increase in flow rates leads to a magnification of the drop size.
  • the proper movement of the gases is imposed in its direction and its intensity on the drops of the mixture to be treated, separated from each other in the zone of convergence of the two streams.
  • the speed of the liquid mixture is further reduced to the minimum necessary to obtain a continuous flow.
  • the atomization is generally done with an outlet temperature of the solid between 90 and 150 ° C.
  • the last step of the process consists in sulfurizing the product obtained after drying.
  • This sulphurization is carried out by reacting the product obtained in the previous step with carbon sulphide, hydrogen sulphide or with a mixture of hydrogen sulphide and carbon sulphide.
  • the sulfurization reaction is carried out at a temperature between 600 ° C and 1000 ° C, preferably around 800 ° C.
  • the respective proportions of CS2 and H2S can vary within wide limits.
  • the sulphurizing gas flow (CS2, H2S or CS2 and H2S) is chosen so that the amount of CS2 or H2S injected into the system during the reaction, i.e. between the start of the temperature rise ( start of the thermal cycle) and the end of the high temperature plateau is sufficient to transform all of the precursor into sulfide.
  • a molar ratio [sulfurizing gas] / [A] + [B]
  • the sulfurizing gas can be used with an inert gas such as argon or nitrogen.
  • the reaction time corresponds to the time necessary to obtain the desired sulfide.
  • the compound is in the form of a powder, the particles of which comprise a layer based on at least one transparent oxide.
  • This layer coats the particles, it may not be perfectly continuous or homogeneous.
  • the particles constituting the compound according to this variant comprise a transparent, uniform oxide coating layer of controlled thickness.
  • transparent oxide is meant here an oxide which, once deposited on the particle in the form of a more or less fine film, absorbs little or no light rays in the visible range.
  • oxide which is used for convenience throughout this description concerning this variant, should be understood as also covering oxides of the hydrated type.
  • oxides can be amorphous and / or crystallized.
  • oxides mention may more particularly be made of silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), titanium oxide, silicate zirconium ZrSi ⁇ 4 (zircon) and rare earth oxides.
  • the coating layer is based on silica. Even more advantageously, this layer is essentially, and preferably only, made of silica.
  • the process for preparing a transparent oxide compound according to this variant essentially consists in bringing the initial compound into contact with a precursor of the above-mentioned transparent oxide and in precipitating the transparent oxide.
  • the term “initial compound” is intended to mean the compound as obtained following the preparation and sulfurization process described above and after possible disagglomeration.
  • silica examples of processes will be given below for the different types of transparent oxides.
  • hydrolysis of an alkyl silicate by forming a reaction medium by mixing water, alcohol, the compound which is then suspended, and optionally d a base, an alkali fluoride or an ammonium fluoride which can act as a catalyst for the condensation of silicate.
  • the alkyl silicate is then introduced.
  • a preparation can also be carried out by reaction of the compound, of a silicate, of the alkaline silicate type, and of an acid.
  • the compound, an aluminate and an acid can be reacted, whereby alumina is precipitated.
  • This precipitation can also be obtained by bringing together and reacting the compound, an aluminum salt and a base.
  • alumina can be formed by hydrolysis of an aluminum alcoholate.
  • titanium oxide it can be precipitated by introducing into a hydroalcoholic suspension of the compound a titanium salt on the one hand such as TiCl4, TiOCl2 or TiOS ⁇ 4, and a base on the other hand.
  • a titanium salt on the one hand such as TiCl4, TiOCl2 or TiOS ⁇ 4, and a base on the other hand.
  • zirconium oxide-based layer it is possible to proceed by cohydrolysis or coprecipitation of a suspension of the compound in the presence of an organometallic compound of zirconium, for example a zirconium alkoxide such as 'zirconium isopropoxide.
  • an organometallic compound of zirconium for example a zirconium alkoxide such as 'zirconium isopropoxide.
  • the compound of the invention is in the form of a powder, the particles of which comprise a zinc compound deposited on their surface.
  • This zinc compound may have been obtained by reaction of a zinc precursor with ammonia and / or an ammonium salt.
  • the form in which this zinc compound is present in the product of the invention is not known precisely. In some cases, however, it may be thought that zinc is present in the form of a zinc-ammonia complex of formula Zn (NH3) x (A) v in which A represents an anion like OH " , CI " , the anion acetate or a mixture of anions, x being at most equal to 4 and y equal to 2.
  • the compound containing zinc can be obtained by bringing the initial compound into contact with a precursor of zinc and ammonia and / or an ammonium salt. This bringing into contact makes it possible to precipitate the zinc compound on the particles constituting the initial compound.
  • the zinc precursor can be a zinc oxide or hydroxide which is used in suspension.
  • This precursor can also be a zinc salt, preferably a soluble salt. It can be an inorganic acid salt such as a chloride, or an organic acid salt such as an acetate.
  • the invention also relates to the combination of the variants which have just been described.
  • a compound whose particles comprise an oxide layer with, in addition, zinc can be included in the oxide layer or located on the surface thereof.
  • Different processes can be envisaged for the preparation of compounds whose particles include zinc with an oxide layer.
  • the initial compound is brought into contact, a zinc precursor, ammonia and / or an ammonium salt and a precursor of the transparent oxide, then the zinc compound is deposited on the initial composition. and the transparent oxide is precipitated on the initial compound.
  • the initial compound in a first step, is brought into contact with a precursor of the transparent oxide and the transparent oxide is precipitated on said initial compound then, in a second step, the compound is thus brought into contact obtained with a zinc precursor, ammonia and / or an ammonium salt and the zinc compound is deposited there.
  • the contact between the compound, the zinc precursor, the ammonia and / or the ammonium salt and, where appropriate, the precursor of the transparent oxide takes place in the presence of a alcohol.
  • the alcohol used is generally chosen from aliphatic alcohols such as, for example, butanol or ethanol.
  • the alcohol can, in particular, be provided with the zinc precursor in the form of an alcoholic solution of zinc.
  • the compound, the zinc precursor, the ammonia and / or the ammonium salt and, where appropriate, the precursor of the transparent oxide are brought into contact, in the presence of a dispersant.
  • a dispersant is to avoid agglomeration of the particles of the compound during their suspension for the treatments described above. It also allows you to work in more concentrated environments. It also promotes the formation of a homogeneous layer of transparent oxide on all of the particles.
  • This dispersant can be chosen from the group of dispersants by steric effect and in particular non-ionic water-soluble or organosoluble polymers. Mention may be made, as dispersing agent, of cellulose and its derivatives, of polyacrylamides, of polyethylene oxides, of polyethylene glycols, of polyoxyethylenated polyoxypropylene glycols, of polyacrylates, of polyoxyethylenated alkyl phenols, of long-chain polyoxyethylene alcohols, of polyvinyl alcohols, of alkanolamides, dispersants of the polyvinylpyrrolidone type, xanthan gum-based compounds.
  • dispersing agent of cellulose and its derivatives, of polyacrylamides, of polyethylene oxides, of polyethylene glycols, of polyoxyethylenated polyoxypropylene glycols, of polyacrylates, of polyoxyethylenated alkyl phenols, of long-chain polyoxyethylene alcohols, of polyvinyl alcohols
  • the product obtained at the end of the operations described above can be washed with water or alcohol. It can also be air dried or vacuum dried.
  • the compounds described above or as obtained by the methods which have just been studied can be used as luminophores, in particular in cathodoluminescence, that is to say in applications using excitations of the type electronic.
  • the invention finally applies to the aforementioned devices using cathodoluminescence and comprising a compound according to the invention. Examples will now be given.
  • the particle size was determined according to the aforementioned technique. It is further specified that the measurement was carried out on a dispersion of the product in an aqueous solution at 0.05% by weight of sodium hexametaphosphate and which has previously undergone passage through the ultrasonic probe (probe with tip of 13mm diameter, 20KHz, 120W) for 3 minutes.
  • the chromaticity coordinates are given in the system as defined by the International Lighting Commission and listed in the Collection of French Standards (AFNOR), colorimetric n ° X08-12, (1983).
  • the oxygen content is determined by analysis with a Leco® device.
  • a mixture of cerium III nitrates, gallium, strontium and sodium in the proportions corresponding to those of the desired compound is atomized on a Bùchi® device, the inlet temperature being 210 ° C while the outlet temperature is 110 ° C.
  • the presence of sodium in the material makes it possible to compensate for the excess charge due to the cerium coming in substitution for a fraction of the strontium.
  • the reaction gas mixture consists of argon (50% by volume), CS2 (30%) and d * H2S (20%).
  • the flow rate of the gas mixture is 101 / h.
  • the thermal cycle is as follows: rise to 8 ° C / min from ambient to 800 ° C then leveling for 30 minutes at 800 ° C with H2S / CS2 mixture, then lowering at 8 ° C / min under argon to 'at the temperature of 60 ° C from which the oven can be opened and the product collected.
  • the product is in the form of a phasically pure powder with a cubic crystallographic structure.
  • the average particle size is 4 ⁇ m.
  • the dispersion index is 0.6.
  • the oxygen content of the product is 1.1%.
  • Cerium and sodium doped strontium thiogallate exhibits intense luminescence in blue when it is placed under UV excitation (254 nm) or under electronic excitation.
  • the product is in the form of a phasically pure powder with a cubic crystallographic structure, the RX spectrum of which is given in FIG. 1.
  • the average particle size is 3.3 ⁇ m.
  • the dispersion index is 0.66.
  • the oxygen content of the product is 1.1%.
  • This example relates to the application in low voltage luminescence of compounds of Examples 1 and 2.
  • the products were deposited by screen printing on a transparent substrate with a charge rate of Img / cm ⁇ .
  • This example relates to the preparation of a compound according to the invention comprising a layer of zinc oxide and of silica.
  • the strontium thiogallate doped with 5% europium of Example 2 is used as the initial compound.
  • the treatment for the deposition of the oxide layer is as follows.
  • Polyvinylpyrrolidone (PVP) is dissolved in ethanol.
  • the strontium thiogallate is added to this solution.
  • the suspension obtained is dispersed using ultrasound and then the ammonia solution is added, then the zinc precursor.
  • the ethyl silicate is introduced continuously for two hours. After the end of introduction of the ethyl silicate, a two-hour ripening is carried out.
  • the particles thus obtained are washed with ethanol by filtration and then dried at 50 ° C for twelve hours.
  • the reagents were used in the following proportions:
  • a product encapsulated with a mixed silica / zinc layer is obtained.
  • This example relates to the preparation of a compound according to the invention comprising a layer of silica.
  • a compound according to the invention comprising a layer of silica.
  • the reagents are used in the following proportions:
  • a product encapsulated with a layer of silica is obtained.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Luminescent Compositions (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

The invention concerns a compound with a base of an alkaline-earth, sulphur and aluminium, gallium or indium, method for preparing same and use as luminophore. The compound is of formula AB2S4 in which A represents an alkaline-earth, B aluminium, gallium or indium, and it is characterised in that it is in the form of a powder residual content of oxygen not more than 1.5 % and consists of particles of average size not more than 10νm. This compound is obtained by a method consisting in the following steps: forming a solution or a suspension containing salts of elements A and B, drying the solution or suspension by pulverisation; reacting the product obtained from the preceding step with carbon disulphide or with a mixture of hydrogen sulphide and carbon disulphide. The compound can be used as luminophore, in particular in cathodoluminescence.

Description

COMPOSE A BASE D'UN ALCALINO-TERREUX. DE SOUFRE ET D'ALUMINIUM. DE GALLIUM OU D'INDIUM. SON PROCEDE DE PREPARATION ET SON UTILISATION COMPOUND BASED ON AN ALKALINE EARTH. SULFUR AND ALUMINUM. GALLIUM OR INDIUM. ITS PREPARATION PROCESS AND ITS USE
COMME LUMINOPHORELIKE LUMINOPHORE
RHONE-POULENC CHIMIERHONE-POULENC CHEMISTRY
La présente invention concerne un composé à base d'un alcalino-terreux, de soufre et d'aluminium, de gallium ou d'indium, son procédé de préparation et son utilisation comme luminophore. Les domaines de la luminescence et de l'électronique connaissent actuellement des développements importants. On peut citer comme exemple de ces développements, la mise au point des systèmes cathodoluminescents pour les nouvelles techniques de visualisation et d'éclairage. Une application concrète est celle du remplacement des écrans de télévision actuels par des écrans plats. Ces nouvelles applications nécessitent des matériaux luminophores présentant des propriétés de plus en plus améliorées. Ainsi, outre leur propriété de luminescence, on demande à ces matériaux des caractéristiques spécifiques de morphologie ou de granulométrie afin de faciliter notamment leur mise en oeuvre dans les applications recherchées.The present invention relates to a compound based on an alkaline earth metal, sulfur and aluminum, gallium or indium, its preparation process and its use as a phosphor. The fields of luminescence and electronics are currently experiencing significant developments. As an example of these developments, we can cite the development of cathodoluminescent systems for new visualization and lighting techniques. One concrete application is that of replacing current television screens with flat screens. These new applications require phosphor materials with increasingly improved properties. Thus, in addition to their luminescence property, these materials are asked for specific characteristics of morphology or particle size in order to facilitate in particular their use in the desired applications.
Plus précisément, il est demandé d'avoir des luminophores de taille micronique et, éventuellement, ayant une répartition granulométrique resserrée.More specifically, it is required to have phosphors of micron size and, optionally, having a tight particle size distribution.
Comme luminophores, on connaît les thiogallates d'alcalino-terreux. Ces produits sont préparés à partir d'un mélange de sels ou d'oxydes des différents constituants par chauffage à haute température en présence d'un agent fondant (flux). Ce mode de préparation conduit à des produits de taille élevée avec une répartition granulométrique souvent très étendue.As phosphors, we know the alkaline earth thiogallates. These products are prepared from a mixture of salts or oxides of the various constituents by heating at high temperature in the presence of a fluxing agent. This method of preparation leads to large products with an often very large particle size distribution.
L'objet de l'invention est de procurer des produits de ce type de faible taille de particules.The object of the invention is to provide products of this type with a small particle size.
Dans ce but, le composé de l'invention, un premier mode de réalisation, répond à la formule AB2S4 (1 ) dans laquelle A représente un ou plusieurs alcalino-terreux, B au moins un élément pris dans le groupe comprenant l'aluminium, le gallium ou l'indium, et il est caractérisé en ce qu'il se présente sous forme d'une poudre de teneur résiduelle en oxygène d'au plus 1 ,5%, plus particulièrement d'au plus 1 %.For this purpose, the compound of the invention, a first embodiment, corresponds to the formula AB2S4 (1) in which A represents one or more alkaline earths, B at least one element taken from the group comprising aluminum, gallium or indium, and it is characterized in that it is in the form of a powder with a residual oxygen content of at most 1.5%, more particularly at most 1%.
Selon un second mode de réalisation, le composé de l'invention répond à la formule (1) et il est caractérisé en ce qu'il se présente sous forme d'une poudre constituée de particules entières ou non broyées, de taille moyenne d'au plus 10μm.According to a second embodiment, the compound of the invention corresponds to formula (1) and it is characterized in that it is in the form of a powder consisting of whole or unmilled particles, of average size at most 10μm.
L'invention concerne aussi un procédé de préparation d'un tel composé qui est caractérisé en ce qu'il comporte les étapes suivantes : - on forme une solution ou une suspension comprenant des sels des éléments A et B et éventuellement du dopant;The invention also relates to a process for the preparation of such a compound which is characterized in that it comprises the following stages: - A solution or a suspension is formed comprising salts of elements A and B and optionally of the dopant;
- on sèche par atomisation la solution ou la suspension;- The solution or the suspension is spray-dried;
- on fait réagir le produit obtenu à l'étape précédente avec du sulfure de carbone ou avec un mélange de sulfure d'hydrogène et de sulfure de carbone.- The product obtained in the previous step is reacted with carbon sulfide or with a mixture of hydrogen sulfide and carbon sulfide.
Enfin, l'invention concerne l'utilisation comme luminophore, notamment en cathodoluminescence, d'un composé tel que décrit plus haut.Finally, the invention relates to the use as a phosphor, in particular in cathodoluminescence, of a compound as described above.
D'autres caractéristiques, détails et avantages de l'invention apparaîtront encore plus complètement à la lecture de la description qui va suivre et du dessin annexé dans lequel :Other characteristics, details and advantages of the invention will appear even more completely on reading the description which follows and the appended drawing in which:
- la figure 1 est un spectre RX d'un composé selon l'invention.- Figure 1 is an RX spectrum of a compound according to the invention.
Comme indiqué plus haut, le composé de l'invention se présente sous forme d'une poudre et il répond à la formule (1) AB2S4. Dans cette formule, A est un alcalino-terreux (groupe Ha de la classification périodique). La classification périodique des éléments à laquelle il est fait référence, ici et pour l'ensemble de la description, est celle publiée dans le Supplément au Bulletin de la Société Chimique de France n° 1 (janvier 1966).As indicated above, the compound of the invention is in the form of a powder and it corresponds to formula (1) AB2S4. In this formula, A is an alkaline earth (group Ha of the periodic table). The periodic classification of the elements to which reference is made, here and for the entire description, is that published in the Supplement to the Bulletin of the French Chemical Society No. 1 (January 1966).
A peut être tout particulièrement le strontium. A peut être aussi le magnésium, le calcium ou le baryum.A may especially be strontium. A can also be magnesium, calcium or barium.
B peut être l'aluminium, le gallium ou l'indium. B peut être plus particulièrement le gallium. Selon un mode de réalisation particulier, le composé de l'invention est un thiogallate de strontium.B can be aluminum, gallium or indium. B can more particularly be gallium. According to a particular embodiment, the compound of the invention is a strontium thiogallate.
L'invention concerne aussi les composés dans lesquels A représente plusieurs alcalino-terreux. De même, B peut représenter une combinaison d'au moins deux des éléments aluminium, gallium ou indium. Le composé de l'invention peut comprendre un ou plusieurs dopants. On entend ici par dopant tout élément pouvant conférer au composé de formule (1) des propriétés de luminescence dans une application donnée du composé comme luminophore. Sans vouloir être limité par une théorie, on peut penser que le dopant vient en substitution de l'alcalino-terreux. La quantité de dopant est habituellement d'au plus 10% atomique par rapport à l'élément alcalino-terreux. Plus particulièrement, ce dopant peut être choisi parmi le manganèse divalent, les terres rares divalentes et le groupe comprenant les terres rares trivalentes en combinaison avec un alcalin. Dans le cas des terres rares trivalentes, la présence d'un alcalin est nécessaire pour compenser l'excès de charge dû à la terre rare. L'alcalin peut être plus particulièrement le sodium. Par terre rare on entend les éléments du groupe constitué par l'yttrium et les éléments de la classification périodique de numéro atomique compris inclusivement entre 57 et 71. Le dopant peut être plus particulièrement l'europium II, l'ytterbium II ou le cérium III en combinaison avec un alcalin.The invention also relates to the compounds in which A represents several alkaline earths. Likewise, B can represent a combination of at least two of the elements aluminum, gallium or indium. The compound of the invention can comprise one or more dopants. The term “dopant” is understood here to mean any element which can confer on the compound of formula (1) luminescence properties in a given application of the compound as a phosphor. Without wanting to be limited by a theory, one can think that the dopant comes in substitution for the alkaline-earth. The amount of dopant is usually at most 10 atomic% relative to the alkaline earth element. More particularly, this dopant can be chosen from divalent manganese, divalent rare earths and the group comprising trivalent rare earths in combination with an alkali. In the case of trivalent rare earths, the presence of an alkali is necessary to compensate for the excess charge due to the rare earth. The alkali can more particularly be sodium. By rare earth is meant the elements of the group constituted by yttrium and the elements of the periodic classification with atomic number included inclusively between 57 and 71. The dopant can more particularly be europium II, ytterbium II or cerium III in combination with an alkali.
Selon un premier mode de réalisation, le composé de l'invention est caractérisé par sa faible teneur résiduelle en oxygène. Cette teneur est en effet plus faible que celle des composés de l'art antérieur. Ce faible taux d'oxygène résiduel pourrait être une des raisons des propriétés intéressantes en luminescence du produit de l'invention. Comme indiquée plus haut, cette teneur résiduelle est d'au plus 1 ,5%, plus particulièrement d'au plus 1 %. Elle est exprimée en poids d'oxygène par rapport au poids total du composé.According to a first embodiment, the compound of the invention is characterized by its low residual oxygen content. This content is indeed lower than that of the compounds of the prior art. This low residual oxygen level could be one of the reasons for the advantageous luminescence properties of the product of the invention. As indicated above, this residual content is at most 1.5%, more particularly at most 1%. It is expressed by weight of oxygen relative to the total weight of the compound.
Selon un second mode de réalisation de l'invention, le composé de l'invention est caractérisé par sa morphologie. Selon ce mode, le composé est constitué de particules dé taille moyenne d'au plus 10μm. Pour l'ensemble de la description les caractéristiques de taille et de granulométrie sont mesurées par la technique de diffraction laser en utilisant un granulomètre du type CILAS HR 850 (répartition en volume).According to a second embodiment of the invention, the compound of the invention is characterized by its morphology. According to this mode, the compound consists of particles of average size of at most 10 μm. For the whole of the description, the size and particle size characteristics are measured by the laser diffraction technique using a particle size analyzer of the CILAS HR 850 type (volume distribution).
Cette taille moyenne peut être plus particulièrement d'au plus 5μm et encore plus particulièrement d'au plus 4μm.This average size can more particularly be at most 5 μm and even more particularly at most 4 μm.
Les particules dont la taille vient d'être donnée ci-dessus sont des particules non broyées ou entières. Les photos en microscopie électronique à balayage permettent de montrer que ces particules n'ont pas l'aspect rompu ou brisé que présentent des particules qui ont subi un broyage. De même ces photos montrent que ces particules ne présentent pas, adhérant à leur surface, des particules de taille nettement plus fine, comme cela peut être le cas à l'issue d'un broyage où des particules fines créées par le broyage peuvent venir s'agréger à des particules plus grosses. On notera cependant que la poudre constituant le produit de l'invention peut avoir été simplement désagglomérée. Les composés selon le premier mode de réalisation peuvent bien entendu présenter les caractéristiques granulométriques qui viennent d'être données plus haut en combinaison avec la caractéristique de teneur résiduelle en oxygène. De même, ceux du deuxième mode peuvent aussi présenter, en combinaison avec les caractéristiques de granulométrie, la teneur en oxygène des composés du premier mode de réalisation.The particles whose size has just been given above are unmilled or whole particles. The photos in scanning electron microscopy make it possible to show that these particles do not have the broken or broken appearance that particles which have undergone grinding have. Similarly, these photos show that these particles do not have, adhering to their surface, particles of much finer size, as may be the case after grinding where fine particles created by grinding can come s '' aggregate to larger particles. Note, however, that the powder constituting the product of the invention may have been simply deagglomerated. The compounds according to the first embodiment can of course have the particle size characteristics which have just been given above in combination with the characteristic of residual oxygen content. Likewise, those of the second embodiment can also have, in combination with the particle size characteristics, the oxygen content of the compounds of the first embodiment.
L'ensemble des caractéristiques additionnelles qui vont maintenant être données s'applique aux deux modes de réalisation.All of the additional characteristics which will now be given apply to the two embodiments.
Selon une variante préférée de l'invention, le composé présente une répartition granulométrique resserrée. Ainsi, l'indice de dispersion σ/m est d'au plus 0,7. Il peut être plus particulièrement d'au plus 0,6.According to a preferred variant of the invention, the compound has a narrow particle size distribution. Thus, the dispersion index σ / m is at most 0.7. It can more particularly be at most 0.6.
On entend par indice de dispersion le rapport : σ/m = (d84-d16)/2d50 dans lequel : - d84 est le diamètre des particules pour lequel 84% des particules ont un diamètre inférieur à d84;By dispersion index is meant the ratio: σ / m = (d 84 -d 16 ) / 2d 50 in which: - d 84 is the particle diameter for which 84% of the particles have a diameter less than d 84 ;
- d-|6 est le diamètre des particules pour lequel 16% des particules ont un diamètre inférieur à d16; - d50 est le diamètre moyen des particules.- d- | 6 is the particle diameter for which 16% of the particles have a diameter less than d 16 ; - d 50 is the average particle diameter.
Les composés de l'invention peuvent être constitués de particules de forme sensiblement sphérique et dont le diamètre correspond aux tailles moyennes qui ont été données ci-dessus.The compounds of the invention may consist of particles of substantially spherical shape and whose diameter corresponds to the average sizes which have been given above.
Une autre caractéristique des composés de l'invention est qu'ils se présentent sous forme d'une phase cristallographique pure, cette pureté pouvant être mise en évidence par les spectres de diffraction X des composés.Another characteristic of the compounds of the invention is that they are in the form of a pure crystallographic phase, this purity being able to be demonstrated by the X-ray diffraction spectra of the compounds.
Dans le cas particulier du thiogallate de strontium, cette phase cristallographique est une phase cubique.In the particular case of strontium thiogallate, this crystallographic phase is a cubic phase.
Le procédé de préparation des composés de l'invention va maintenant être décrit. La première étape du procédé consiste à former une solution ou une suspension comprenant des sels des éléments A et B et éventuellement du dopant.The process for the preparation of the compounds of the invention will now be described. The first step of the process consists in forming a solution or a suspension comprising salts of elements A and B and optionally of the dopant.
On utilise habituellement des sels inorganiques comme les nitrates, les sulfates ou les chlorures ou encore les hydroxydes. On peut éventuellement utiliser des sels organiques mais il est préférable dans ce cas d'employer des sels présentant peu d'atomes de carbone, comme des carbonates ou des acétates.Inorganic salts such as nitrates, sulfates or chlorides or even hydroxides are usually used. Organic salts can optionally be used, but it is preferable in this case to use salts having few carbon atoms, such as carbonates or acetates.
Les sels sont mis dans un milieu liquide, de préférence l'eau, pour former une solution ou une suspension.The salts are put in a liquid medium, preferably water, to form a solution or a suspension.
L'étape suivante consiste à sécher la solution ou la suspension préalablement préparée. Ce séchage se fait par atomisation. On entend par séchage par atomisation un séchage par pulvérisation du mélange dans une atmosphère chaude (spray-drying). L'atomisation peut être réalisée au moyen de tout pulvérisateur connu en soi, par exemple par une buse de pulvérisation du type pomme d'arrosoir ou autre. On peut également utiliser des atomiseurs dits à turbine. Sur les diverses techniques de pulvérisation susceptibles d'être mises en oeuvre dans le présent procédé, on pourra se référer notamment à l'ouvrage de base de MASTERS intitulé "SPRAY-DRYING" (deuxième édition, 1976, Editions George Godwin - London).The next step is to dry the previously prepared solution or suspension. This drying is done by atomization. By spray drying is meant spray drying of the mixture in a hot atmosphere (spray-drying). The atomization can be carried out by means of any sprayer known per se, for example by a spray nozzle of the sprinkler apple type or the like. One can also use so-called turbine atomizers. On the various spraying techniques likely to be used in the present process, reference may be made in particular to the basic work by MASTERS entitled "SPRAY-DRYING" (second edition, 1976, Editions George Godwin - London).
On notera que l'on peut également mettre en oeuvre l'opération d'atomisation- séchage au moyen d'un réacteur "flash", par exemple du type mis au point par la Demanderesse et décrit notamment dans les demandes de brevet français n° 2 257 326, 2 419 754 et 2 431 321. Dans ce cas, les gaz traitants (gaz chauds) sont animés d'un mouvement hélicoïdal et s'écoulent dans un puits-tourbillon. Le mélange à sécher est injecté suivant une trajectoire confondue avec l'axe de symétrie des trajectoires hélicoïdales desdits gaz, ce qui permet de transférer parfaitement la quantité de mouvement des gaz au mélange à traiter. Les gaz assurent ainsi en fait une double fonction : d'une part la pulvérisation, c'est à dire la transformation en fines gouttelettes, du mélange initial, et d'autre part le séchage des gouttelettes obtenues. Par ailleurs, le temps de séjour extrêmement faible (généralement inférieur à 1/10 de seconde environ) des particules dans le réacteur présente pour avantage, entre autres, de limiter d'éventuels risques de surchauffe par suite d'un contact trop long avec les gaz chauds.It will be noted that it is also possible to implement the spray-drying operation by means of a "flash" reactor, for example of the type developed by the Applicant and described in particular in French patent applications no. 2 257 326, 2 419 754 and 2 431 321. In this case, the treating gases (hot gases) are driven in a helical movement and flow in a vortex well. The mixture to be dried is injected along a trajectory coincident with the axis of symmetry of the helical trajectories of said gases, which allows the quantity of movement of gases in the mixture to be treated. The gases thus in fact perform a double function: on the one hand the spraying, that is to say the transformation into fine droplets, of the initial mixture, and on the other hand the drying of the droplets obtained. Furthermore, the extremely short residence time (generally less than about 1/10 of a second) of the particles in the reactor has the advantage, inter alia, of limiting possible risks of overheating as a result of too long contact with the hot gases.
En ce qui concerne le réacteur flash mentionné plus haut, on pourra notamment se référer à la figure 1 de la demande de brevet français 2431 321.With regard to the flash reactor mentioned above, reference may in particular be made to FIG. 1 of French patent application 2431 321.
Celui-ci est constitué d'une chambre de combustion et d'une chambre de contact composée d'un bicône ou d'un cône tronqué dont la partie supérieure diverge. La chambre de combustion débouche dans la chambre de contact par un passage réduit.This consists of a combustion chamber and a contact chamber composed of a bicone or a truncated cone, the upper part of which diverges. The combustion chamber opens into the contact chamber through a reduced passage.
La partie supérieure de la chambre de combustion est munie d'une ouverture permettant l'introduction de la phase combustible.The upper part of the combustion chamber is provided with an opening allowing the introduction of the combustible phase.
D'autre part la chambre de combustion comprend un cylindre interne coaxial, définissant ainsi à l'intérieur de celle-ci une zone centrale et une zone périphérique annulaire, présentant des perforations se situant pour la plupart vers la partie supérieure de l'appareil. La chambre comprend au minimum six perforations distribuées sur au moins un cercle, mais de préférence sur plusieurs cercles espacés axialement. La surface totale des perforations localisées dans la partie inférieure de la chambre peut être très faible, de l'ordre de 1/10 à 1/100 de la surface totale des perforations dudit cylindre interne coaxial.On the other hand, the combustion chamber comprises an internal coaxial cylinder, thus defining inside thereof a central zone and an annular peripheral zone, having perforations lying for the most part towards the upper part of the appliance. The chamber comprises at least six perforations distributed over at least one circle, but preferably over several circles spaced axially. The total surface of the perforations located in the lower part of the chamber can be very small, of the order of 1/10 to 1/100 of the total surface of the perforations of said internal coaxial cylinder.
Les perforations sont habituellement circulaires et présentent une épaisseur très faible. De préférence, le rapport du diamètre de celles-ci à l'épaisseur de la paroi est d'au moins 5, l'épaisseur minimale de la paroi étant seulement limitée par les impératifs mécaniques.The perforations are usually circular and have a very small thickness. Preferably, the ratio of the diameter of these to the thickness of the wall is at least 5, the minimum thickness of the wall being only limited by mechanical requirements.
Enfin, un tuyau coudé débouche dans le passage réduit, dont l'extrémité s'ouvre dans l'axe de la zone centrale.Finally, a bent pipe opens into the reduced passage, the end of which opens in the axis of the central zone.
La phase gazeuse animée d'un mouvement hélicoïdal (par la suite appelée phase hélicoïdale) est composée d'un gaz, généralement de l'air, introduit dans un orifice pratiqué dans la zone annulaire, de préférence cet orifice est situé dans la partie inférieure de ladite zone.The gas phase animated by a helical movement (hereinafter called helical phase) is composed of a gas, generally air, introduced into an orifice made in the annular zone, preferably this orifice is located in the lower part of said area.
Afin d'obtenir une phase hélicoïdale au niveau du passage réduit, la phase gazeuse est de préférence introduite à basse pression dans l'orifice précité, c'est-à-dire à une pression inférieure à 1 bar et plus particulièrement à une pression comprise entre 0,2 et 0,5 bar au-dessus de la pression existant dans la chambre de contact. La vitesse de cette phase hélicoïdale est généralement comprise entre 10 et 100 m/s et de préférence entre 30 et 60 m/s. Par ailleurs, une phase combustible qui peut être notamment du méthane, est injectée axialement par l'ouverture précitée dans la zone centrale à une vitesse d'environ 100 à 150 m/s.In order to obtain a helical phase at the level of the reduced passage, the gas phase is preferably introduced at low pressure into the abovementioned orifice, that is to say at a pressure of less than 1 bar and more particularly at a pressure included between 0.2 and 0.5 bar above the pressure existing in the contact chamber. The speed of this helical phase is generally between 10 and 100 m / s and preferably between 30 and 60 m / s. Furthermore, a combustible phase which can in particular be methane, is injected axially through the aforementioned opening in the central zone at a speed of approximately 100 to 150 m / s.
La phase combustible est enflammée par tout moyen connu, dans la région où le combustible et la phase hélicoïdale sont en contact.The combustible phase is ignited by any known means, in the region where the fuel and the helical phase are in contact.
Par la suite, le passage imposé des gaz dans le passage réduit se fait suivant un ensemble de trajectoires confondues avec des familles de génératrices d'un hyperboloïde. Ces génératrices reposent sur une famille de cercles, d'anneaux de petite taille localisés près et au-dessous du passage réduit, avant de diverger dans toutes les directions.Thereafter, the imposed passage of the gases in the reduced passage is done according to a set of trajectories confused with families of generators of a hyperboloid. These generators rest on a family of circles, small rings located near and below the reduced passage, before diverging in all directions.
On introduit ensuite le mélange à traiter sous forme de liquide par le tuyau précité. Le liquide est alors fractionné en une multitude de gouttes, chacune d'elle étant transportée par un volume de gaz et soumise à un mouvement créant un effet centrifuge. Habituellement, le débit du liquide est compris entre 0,03 et 10 m/s.. Le rapport entre la quantité de mouvement propre de la phase hélicoïdale et celle du mélange liquide doit être élevé. En particulier il est d'au moins 100 et de préférence compris entre 1000 et 10000. Les quantités de mouvement au niveau du passage réduit sont calculées en fonction des débits d'entrée du gaz et du mélange à traiter, ainsi que de la section dudit passage. Une augmentation des débits entraîne un grossissement de la taille des gouttes.The mixture to be treated is then introduced in the form of a liquid through the above-mentioned pipe. The liquid is then divided into a multitude of drops, each of which is transported by a volume of gas and subjected to a movement creating a centrifugal effect. Usually, the flow rate of the liquid is between 0.03 and 10 m / s. The ratio between the momentum of the helical phase and that of the liquid mixture must be high. In particular, it is at least 100 and preferably between 1000 and 10000. The amounts of movement at the reduced passage are calculated as a function of the inlet flow rates of the gas and of the mixture to be treated, as well as of the section of said passage. An increase in flow rates leads to a magnification of the drop size.
Dans ces conditions, le mouvement propre des gaz est imposé dans sa direction et son intensité aux gouttes du mélange à traiter, séparées les unes des autres dans la zone de convergence des deux courants. La vitesse du mélange liquide est de plus réduite au minimum nécessaire pour obtenir un flot continu. L'atomisation se fait généralement avec une température de sortie du solide comprise entre 90 et 150°C.Under these conditions, the proper movement of the gases is imposed in its direction and its intensity on the drops of the mixture to be treated, separated from each other in the zone of convergence of the two streams. The speed of the liquid mixture is further reduced to the minimum necessary to obtain a continuous flow. The atomization is generally done with an outlet temperature of the solid between 90 and 150 ° C.
La dernière étape du procédé consiste à sulfurer le produit obtenu à l'issue du séchage.The last step of the process consists in sulfurizing the product obtained after drying.
Cette sulfuration est effectuée en faisant réagir le produit obtenu à l'étape précédente avec du sulfure de carbone, du sulfure d'hydrogène ou avec un mélange de sulfure d'hydrogène et de sulfure de carbone. La réaction de sulfuration est conduite à une température comprise entre 600°C et 1000°C, de préférence vers 800°C.This sulphurization is carried out by reacting the product obtained in the previous step with carbon sulphide, hydrogen sulphide or with a mixture of hydrogen sulphide and carbon sulphide. The sulfurization reaction is carried out at a temperature between 600 ° C and 1000 ° C, preferably around 800 ° C.
Dans le cas d'un mélange de sulfure d'hydrogène et de sulfure de carbone, les proportions respectives de CS2 et de H2S peuvent varier dans de larges proportions. Habituellement, le débit de gaz sulfurant (CS2, H2S ou CS2 et H2S) est choisi de telle sorte que la quantité de CS2 ou H2S injectée dans le système pendant la réaction, c'est à dire entre le début de la montée en température (début du cycle thermique) et la fin du palier haute température soit suffisante pour transformer la totalité du précurseur en sulfure. Généralement, un rapport molaire ( [gaz sulfurant] / [A] + [B] ) supérieur à 4 permet de répondre à cette exigence.In the case of a mixture of hydrogen sulfide and carbon sulfide, the respective proportions of CS2 and H2S can vary within wide limits. Usually, the sulphurizing gas flow (CS2, H2S or CS2 and H2S) is chosen so that the amount of CS2 or H2S injected into the system during the reaction, i.e. between the start of the temperature rise ( start of the thermal cycle) and the end of the high temperature plateau is sufficient to transform all of the precursor into sulfide. Generally, a molar ratio ([sulfurizing gas] / [A] + [B]) greater than 4 makes it possible to meet this requirement.
Le gaz sulfurant peut être mis en oeuvre avec un gaz inerte comme l'argon ou l'azote. La durée de la réaction correspond au temps nécessaire pour l'obtention du sulfure désiré.The sulfurizing gas can be used with an inert gas such as argon or nitrogen. The reaction time corresponds to the time necessary to obtain the desired sulfide.
A l'issue du chauffage, on récupère le sulfure formé.After heating, the sulfide formed is recovered.
Des variantes additionnelles du composé selon l'invention vont maintenant être décrites. Dans le cas de ces variantes, toutes les caractéristiques déjà décrites du composé s'appliquent aussi.Additional variants of the compound according to the invention will now be described. In the case of these variants, all the characteristics already described of the compound also apply.
Selon une première de ces variantes, le composé se présente sous la forme d'une poudre dont les particules comprennent une couche à base d'au moins un oxyde transparent.According to a first of these variants, the compound is in the form of a powder, the particles of which comprise a layer based on at least one transparent oxide.
Cette couche enrobe les particules, elle peut ne pas être parfaitement continue ou homogène. Toutefois, de préférence, les particules constituant le composé selon cette variante comprennent une couche de revêtement d'oxyde transparent, uniforme et d'épaisseur contrôlée .This layer coats the particles, it may not be perfectly continuous or homogeneous. However, preferably, the particles constituting the compound according to this variant comprise a transparent, uniform oxide coating layer of controlled thickness.
Par oxyde transparent, on entend ici un oxyde qui, une fois déposé sur la particule sous la forme d'une pellicule plus ou moins fine, n'absorbe que peu ou pas du tout les rayons lumineux dans le domaine du visible. En outre, il convient de noter que le terme oxyde, qui est utilisé par commodité dans l'ensemble de la présente description concernant cette variante, doit être entendu comme couvrant également des oxydes du type hydraté.By transparent oxide is meant here an oxide which, once deposited on the particle in the form of a more or less fine film, absorbs little or no light rays in the visible range. In addition, it should be noted that the term oxide, which is used for convenience throughout this description concerning this variant, should be understood as also covering oxides of the hydrated type.
Ces oxydes, ou oxydes hydratés, peuvent être amorphes et/ou cristallisés. A titre d'exemple de tels oxydes, on peut plus particulièrement citer l'oxyde de silicium (silice), l'oxyde d'aluminium (alumine), l'oxyde de zirconium (zircone), l'oxyde de titane, le silicate de zirconium ZrSiθ4 (zircon) et les oxydes de terres rares. Selon une variante préférée, la couche enrobante est à base de silice. De manière encore plus avantageuse, cette couche est essentiellement, et de préférence uniquement, constituée de silice.These oxides, or hydrated oxides, can be amorphous and / or crystallized. As an example of such oxides, mention may more particularly be made of silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), titanium oxide, silicate zirconium ZrSiθ4 (zircon) and rare earth oxides. According to a preferred variant, the coating layer is based on silica. Even more advantageously, this layer is essentially, and preferably only, made of silica.
Le procédé de préparation d'un composé à oxyde transparent selon cette variante consiste essentiellement à mettre en contact le composé initial avec un précurseur de l'oxyde transparent précité et à précipiter l'oxyde transparent. On entend par composé initial, le composé tel qu'obtenu à la suite du procédé de préparation et de sulfuration décrit plus haut et après désagglomération éventuelle.The process for preparing a transparent oxide compound according to this variant essentially consists in bringing the initial compound into contact with a precursor of the above-mentioned transparent oxide and in precipitating the transparent oxide. The term “initial compound” is intended to mean the compound as obtained following the preparation and sulfurization process described above and after possible disagglomeration.
Des exemples de procédés vont être donnés ci-dessous pour les différents types d'oxydes transparents. Dans le cas de la silice on peut mentionner la préparation de la silice par hydrolyse d'un alkyl-silicate, en formant un milieu réactionnel par mélange d'eau, d'alcool, du composé qui est alors mis en suspension, et éventuellement d'une base, d'un fluorure alcalin ou d'un fluorure d'ammonium qui peut jouer le rôle de catalyseur de la condensation du silicate. On introduit ensuite l'alkyl-silicate. On peut encore effectuer une préparation par réaction du composé, d'un silicate, du type silicate alcalin, et d'un acide.Examples of processes will be given below for the different types of transparent oxides. In the case of silica, mention may be made of the preparation of silica by hydrolysis of an alkyl silicate, by forming a reaction medium by mixing water, alcohol, the compound which is then suspended, and optionally d a base, an alkali fluoride or an ammonium fluoride which can act as a catalyst for the condensation of silicate. The alkyl silicate is then introduced. A preparation can also be carried out by reaction of the compound, of a silicate, of the alkaline silicate type, and of an acid.
Dans le cas d'une couche à base d'alumine, on peut faire réagir le composé, un aluminate et un acide, ce par quoi on précipite de l'alumine. Cette précipitation peut aussi être obtenue en mettant en présence et en faisant réagir le composé, un sel d'aluminium et une base.In the case of an alumina-based layer, the compound, an aluminate and an acid can be reacted, whereby alumina is precipitated. This precipitation can also be obtained by bringing together and reacting the compound, an aluminum salt and a base.
Enfin, on peut former l'alumine par hydrolyse d'un alcoolate d'aluminium. Pour ce qui est de l'oxyde de titane, on peut le précipiter en introduisant dans une suspension hydroalcoolique du composé un sel de titane d'une part tel que TiCl4, TiOCl2 ou TiOSθ4, et une base d'autre part. On peut aussi opérer par exemple par hydrolyse d'un titanate d'alkyle ou précipitation d'un sol de titane.Finally, alumina can be formed by hydrolysis of an aluminum alcoholate. As regards titanium oxide, it can be precipitated by introducing into a hydroalcoholic suspension of the compound a titanium salt on the one hand such as TiCl4, TiOCl2 or TiOSθ4, and a base on the other hand. One can also operate for example by hydrolysis of an alkyl titanate or precipitation of a titanium sol.
Enfin, dans le cas d'une couche à base d'oxyde de zirconium, il est possible de procéder par cohydrolyse ou coprécipitation d'une suspension du composé en présence d'un composé organométallique du zirconium, par exemple un alcoxyde de zirconium comme l'isopropoxyde de zirconium.Finally, in the case of a zirconium oxide-based layer, it is possible to proceed by cohydrolysis or coprecipitation of a suspension of the compound in the presence of an organometallic compound of zirconium, for example a zirconium alkoxide such as 'zirconium isopropoxide.
Selon une autre variante, le composé de l'invention se présente sous la forme d'une poudre dont les particules comprennent un composé du zinc déposé à leur surface. Ce composé du zinc peut avoir été obtenu par réaction d'un précurseur du zinc avec de l'ammoniaque et/ou un sel d'ammonium. La forme sous laquelle se présente ce composé du zinc dans le produit de l'invention n'est pas connue précisément. Dans certains cas toutefois, on peut penser que le zinc est présent sous la forme d'un complexe zinc-ammoniaque de formule Zn(NH3)x(A)v dans laquelle A représente un anion comme OH", CI", l'anion acétate ou encore un mélange d'anions, x étant au plus égal à 4 et y égal à 2. Le composé contenant du zinc peut être obtenu en mettant en présence le composé initial avec un précurseur du zinc et de l'ammoniaque et/ou un sel d'ammonium. Cette mise en présence permet de faire précipiter le composé du zinc sur les particules constituant le composé initial.According to another variant, the compound of the invention is in the form of a powder, the particles of which comprise a zinc compound deposited on their surface. This zinc compound may have been obtained by reaction of a zinc precursor with ammonia and / or an ammonium salt. The form in which this zinc compound is present in the product of the invention is not known precisely. In some cases, however, it may be thought that zinc is present in the form of a zinc-ammonia complex of formula Zn (NH3) x (A) v in which A represents an anion like OH " , CI " , the anion acetate or a mixture of anions, x being at most equal to 4 and y equal to 2. The compound containing zinc can be obtained by bringing the initial compound into contact with a precursor of zinc and ammonia and / or an ammonium salt. This bringing into contact makes it possible to precipitate the zinc compound on the particles constituting the initial compound.
Le précurseur du zinc peut être un oxyde ou un hydroxyde de zinc que l'on utilise en suspension. Ce précurseur peut être aussi un sel de zinc, de préférence un sel soluble. Ce peut être un sel d'acide inorganique comme un chlorure, ou encore un sel d'acide organique comme un acétate. Bien entendu, l'invention concerne aussi la combinaison des variantes qui viennent d'être décrites. Ainsi, on peut envisager un composé dont les particules comprennent une couche d'oxyde avec en outre du zinc. En particulier, le zinc peut être inclus dans la couche d'oxyde ou situé à la surface de celle-ci. Différents procédés peuvent être envisagées pour la préparation des composés dont les particules comprennent du zinc avec une couche d'oxyde.The zinc precursor can be a zinc oxide or hydroxide which is used in suspension. This precursor can also be a zinc salt, preferably a soluble salt. It can be an inorganic acid salt such as a chloride, or an organic acid salt such as an acetate. Of course, the invention also relates to the combination of the variants which have just been described. Thus, it is possible to envisage a compound whose particles comprise an oxide layer with, in addition, zinc. In particular, zinc can be included in the oxide layer or located on the surface thereof. Different processes can be envisaged for the preparation of compounds whose particles include zinc with an oxide layer.
Dans un premier cas, on met en contact le composé initial, un précurseur du zinc, de l'ammoniaque et/ou un sel d'ammonium et un précurseur de l'oxyde transparent, puis on dépose le composé de zinc sur la composition initiale et on précipite l'oxyde transparent sur le composé initial.In a first case, the initial compound is brought into contact, a zinc precursor, ammonia and / or an ammonium salt and a precursor of the transparent oxide, then the zinc compound is deposited on the initial composition. and the transparent oxide is precipitated on the initial compound.
Dans un autre cas, dans une première étape, on met en contact le composé initial et un précurseur de l'oxyde transparent et on précipite l'oxyde transparent sur ledit composé initial puis, dans une deuxième étape, on met en contact le composé ainsi obtenu avec un précurseur du zinc, de l'ammoniaque et/ou un sel d'ammonium et on y dépose le composé de zinc .In another case, in a first step, the initial compound is brought into contact with a precursor of the transparent oxide and the transparent oxide is precipitated on said initial compound then, in a second step, the compound is thus brought into contact obtained with a zinc precursor, ammonia and / or an ammonium salt and the zinc compound is deposited there.
Selon un autre procédé, la mise en contact entre la composé, le précurseur du zinc, l'ammoniaque et/ou le sel d'ammonium et, le cas échéant, le précurseur de l'oxyde transparent, se fait en présence d'un alcool. L'alcool utilisé est généralement choisi parmi les alcools aliphatiques tel que par exemple le butanol ou l'éthanol. L'alcool peut, en particulier, être apporté avec le précurseur du zinc sous forme d'une solution alcoolique de zinc.According to another method, the contact between the compound, the zinc precursor, the ammonia and / or the ammonium salt and, where appropriate, the precursor of the transparent oxide, takes place in the presence of a alcohol. The alcohol used is generally chosen from aliphatic alcohols such as, for example, butanol or ethanol. The alcohol can, in particular, be provided with the zinc precursor in the form of an alcoholic solution of zinc.
Selon encore un autre type de procédé, on met en contact le composé, le précurseur du zinc, l'ammoniaque et/ou le sel d'ammonium et, le cas échéant, le précurseur de l'oxyde transparent, en présence d'un dispersant. Ce dispersant a pour but d'éviter l'agglomération des particules du composé lors de leur mise en suspension pour les traitements décrits ci-dessus. Il permet aussi de travailler dans des milieux plus concentrés. Il favorise aussi la formation d'une couche homogène d'oxyde transparent sur l'ensemble des particules.According to yet another type of process, the compound, the zinc precursor, the ammonia and / or the ammonium salt and, where appropriate, the precursor of the transparent oxide, are brought into contact, in the presence of a dispersant. The purpose of this dispersant is to avoid agglomeration of the particles of the compound during their suspension for the treatments described above. It also allows you to work in more concentrated environments. It also promotes the formation of a homogeneous layer of transparent oxide on all of the particles.
Ce dispersant peut être choisi dans le groupe des dispersants par effet stérique et notamment des polymères hydrosolubles ou organosolubles non ioniques. On peut citer comme dispersant la cellulose et ses dérivés, les polyacrylamides, les oxydes de polyéthylène, les polyéthylène glycols, les polyoxypropylène glycols polyoxyéthylénés, les polyacrylates, les alkyl phénols polyoxyéthylénés, les alcools à longues chaînes polyoxyéthylénés, les polyvinylalcools, les alkanolamides, les dispersants du type polyvinylpyrrolidone, les composés à base de gomme xanthane.This dispersant can be chosen from the group of dispersants by steric effect and in particular non-ionic water-soluble or organosoluble polymers. Mention may be made, as dispersing agent, of cellulose and its derivatives, of polyacrylamides, of polyethylene oxides, of polyethylene glycols, of polyoxyethylenated polyoxypropylene glycols, of polyacrylates, of polyoxyethylenated alkyl phenols, of long-chain polyoxyethylene alcohols, of polyvinyl alcohols, of alkanolamides, dispersants of the polyvinylpyrrolidone type, xanthan gum-based compounds.
En outre, on peut noter qu'il peut être intéressant de traiter par ultrasons la suspension obtenue à partir du mélange des réactifs. Enfin, le produit obtenu à la fin des opérations décrites ci-dessus peut être lavé à l'eau ou à l'alcool. Il peut être aussi séché à l'air ou encore sous vide.In addition, it can be noted that it may be advantageous to treat the suspension obtained from the mixture of reagents with ultrasound. Finally, the product obtained at the end of the operations described above can be washed with water or alcohol. It can also be air dried or vacuum dried.
On notera que pour les variantes additionelles qui viennent d'être décrites, c'est à dire pour les composés dont les particules comprennent un oxyde transparent et/ou un composé du zinc à leur surface, que les teneurs résiduelles en oxygène données plus haut s'appliquent toujours, non pas au composé global (particules + oxyde transparent et/ou composé du zinc) mais au composé initial, c'est à dire les particules sans oxyde transparent ni composé du zinc.It will be noted that for the additional variants which have just been described, that is to say for the compounds whose particles comprise a transparent oxide and / or a zinc compound on their surface, that the residual oxygen contents given above s '' always apply, not to the overall compound (particles + transparent oxide and / or zinc compound) but to the initial compound, that is to say the particles without transparent oxide or zinc compound.
De par leurs propriétés, les composés décrits plus haut ou tels qu'obtenus par les procédés qui viennent d'être étudiés, peuvent être utilisés comme luminophores, notamment en cathodoluminescence, c'est à dire dans des applications mettant en oeuvre des excitations du type électronique.By their properties, the compounds described above or as obtained by the methods which have just been studied, can be used as luminophores, in particular in cathodoluminescence, that is to say in applications using excitations of the type electronic.
Ils peuvent ainsi être utilisés dans la fabrication de tout dispositif fonctionnant sous ce principe comme les écrans plats FED ou VFD, les écrans à projection, les écrans de télévision. La mise en oeuvre des composés de l'invention dans ce type de dispositifs se fait selon des techniques bien connus, par exemple par dépôt sur les écrans par sédimentation, sérigraphie ou électrophorèse.They can thus be used in the manufacture of any device operating under this principle such as FED or VFD flat screens, projection screens, television screens. The compounds of the invention are used in this type of device using well known techniques, for example by deposition on screens by sedimentation, screen printing or electrophoresis.
L'invention s'applique enfin aux dispositifs précités mettant en oeuvre la cathodoluminescence et comprenant un composé selon l'invention. Des exemples vont maintenant être donnés.The invention finally applies to the aforementioned devices using cathodoluminescence and comprising a compound according to the invention. Examples will now be given.
Dans ces exemples, la granulométrie a été déterminée selon la technique précitée. On précise en plus que la mesure a été effectuée sur une dispersion du produit dans une solution aqueuse à 0,05% en poids d'hexamétaphosphate de sodium et qui a préalablement subi un passage à la sonde à ultra-sons (sonde avec embout de 13mm de diamètre, 20KHz, 120W) pendant 3 minutes. Les coordonnées chromatiques sont données dans le système tel que défini par la Commission Internationale d'Eclairage et répertorié dans le Recueil des Normes Françaises (AFNOR), couleur colorimétrique n° X08-12, (1983). La teneur en oxygène est déterminée par analyse avec un appareil Leco®.In these examples, the particle size was determined according to the aforementioned technique. It is further specified that the measurement was carried out on a dispersion of the product in an aqueous solution at 0.05% by weight of sodium hexametaphosphate and which has previously undergone passage through the ultrasonic probe (probe with tip of 13mm diameter, 20KHz, 120W) for 3 minutes. The chromaticity coordinates are given in the system as defined by the International Lighting Commission and listed in the Collection of French Standards (AFNOR), colorimetric n ° X08-12, (1983). The oxygen content is determined by analysis with a Leco® device.
EXEMPLE 1 ; Synthèse de Nao>oi)Ga2s4EXAMPLE 1 ; Synthesis of Nao > oi) Ga2 s 4
Un mélange de nitrates de cérium III, de gallium, de strontium et de sodium dans les proportions correspondantes à celles du composé recherché est atomisé sur un appareil Bùchi®, la température d'entrée étant de 210°C alors que la température de sortie est de 110°C. La présence de sodium dans le matériau permet de compenser l'excès de charge dû au cérium venant en substitution d'une fraction du strontium.A mixture of cerium III nitrates, gallium, strontium and sodium in the proportions corresponding to those of the desired compound is atomized on a Bùchi® device, the inlet temperature being 210 ° C while the outlet temperature is 110 ° C. The presence of sodium in the material makes it possible to compensate for the excess charge due to the cerium coming in substitution for a fraction of the strontium.
10g de la poudre obtenue sont placés dans une nacelle en carbone vitreux (épaisseur de lit de 1 cm) qui est ensuite introduite dans le four étanche de sulfuration. Le mélange gazeux réactionnel est constitué d'argon (50% en volume), de CS2 (30%) et d* H2S (20%). Le débit du mélange gazeux est de 101/h.10 g of the powder obtained are placed in a glassy carbon basket (bed thickness of 1 cm) which is then introduced into the sealed sulfurization oven. The reaction gas mixture consists of argon (50% by volume), CS2 (30%) and d * H2S (20%). The flow rate of the gas mixture is 101 / h.
Le cycle thermique est le suivant : montée à 8°C/min de l'ambiante jusqu'à 800°C puis palier de 30 minutes à 800°C sous mélange H2S / CS2, puis descente à 8°C/min sous argon jusqu'à la température de 60°C à partir de laquelle le four peut être ouvert et le produit recueilli.The thermal cycle is as follows: rise to 8 ° C / min from ambient to 800 ° C then leveling for 30 minutes at 800 ° C with H2S / CS2 mixture, then lowering at 8 ° C / min under argon to 'at the temperature of 60 ° C from which the oven can be opened and the product collected.
Le produit se présente sous la forme d'une poudre phasiquement pure de structure cristallographique cubique. La taille moyenne des particules est de 4μm. L'indice de dispersion est de 0,6. La teneur en oxygène du produit est de 1 ,1 %. Le thiogallate de strontium dopé cérium et sodium présente une luminescence intense dans le bleu lorsqu'il est placé sous excitation UV (254 nm) ou sous excitation électronique.The product is in the form of a phasically pure powder with a cubic crystallographic structure. The average particle size is 4μm. The dispersion index is 0.6. The oxygen content of the product is 1.1%. Cerium and sodium doped strontium thiogallate exhibits intense luminescence in blue when it is placed under UV excitation (254 nm) or under electronic excitation.
EXEMPLE 2 : Synthèse de (Sroι95Euo,θ5)Ga2s4 Le même protocole expérimental est suivi pour la synthèse de ce composé. Le milieu très réducteur permet d'inclure directement l'europium au degré d'oxydation deux sur le site du strontium.EXAMPLE 2 Synthesis of (Sro ι 95Euo, θ5) Ga2 s 4 The same experimental protocol is followed for the synthesis of this compound. The very reducing medium makes it possible to directly include europium at the oxidation state two at the strontium site.
Le produit se présente sous la forme d'une poudre phasiquement pure de structure cristallographique cubique dont le spectre RX est donné dans la figure 1. La taille moyenne des particules est de 3,3μm. L'indice de dispersion est de 0,66. La teneur en oxygène du produit est de 1 ,1 %.The product is in the form of a phasically pure powder with a cubic crystallographic structure, the RX spectrum of which is given in FIG. 1. The average particle size is 3.3 μm. The dispersion index is 0.66. The oxygen content of the product is 1.1%.
Le thiogallate de strontium dopé europium luminesce dans le vert lorsqu'il est placé sous excitation UV (254 nm) ou sous excitation électronique.The strontium thiogallate doped with europium luminesce in the green when it is placed under UV excitation (254 nm) or under electronic excitation.
EXEMPLE 3EXAMPLE 3
Cet exemple concerne l'application en luminescence basse tension de composés des exemples 1 et 2. Les produits ont été déposés par sérigraphie sur un substrat transparent avec un taux de charge de Img/cm^. On a étudié le rendement du thiogallate dopé cérium de l'exemple 1 sous excitation électronique basse tension (V = 400 V) en fonction de la densité de courant. Dans la gamme de densité de courant étudiée (100-600μA/mm2), on n'observe aucune variation de la réponse du luminophore qui est égale à 1 ,0 Im/W. Il s'agit d'un rendement élevé compte tenu du faible taux de charge des produits sur le substrat. Les coordonnées colorimétriques sont adaptées à la réalisation d'un luminophore bleu : x = 0,124 et y = 0,131. Dans les mêmes conditions d'excitation, le rendement lumineux du produit de l'exemple 2 dopé à l'europium est de 6 Im/W et l'émission verte se caractérise par les coordonnées colorimétriques suivantes : x = 0,25 et y = 0,71. EXEMPLE 4This example relates to the application in low voltage luminescence of compounds of Examples 1 and 2. The products were deposited by screen printing on a transparent substrate with a charge rate of Img / cm ^. The yield of the cerium doped thiogallate of Example 1 was studied under low voltage electronic excitation (V = 400 V) as a function of the current density. In the range of current density studied (100-600μA / mm2), no variation in the response of the phosphor is observed which is equal to 1.0 Im / W. This is a high yield given the low loading rate of the products on the substrate. The color coordinates are adapted to the realization of a blue phosphor: x = 0.124 and y = 0.131. Under the same excitation conditions, the light output of the product of example 2 doped with europium is 6 Im / W and the green emission is characterized by the following color coordinates: x = 0.25 and y = 0.71. EXAMPLE 4
Cet exemple concerne la préparation d'un composé selon l'invention comprenant une couche d'oxyde de zinc et de silice. On utilise comme composé initial le thiogallate de strontium dopé à 5% d'europium de l'exemple 2.This example relates to the preparation of a compound according to the invention comprising a layer of zinc oxide and of silica. The strontium thiogallate doped with 5% europium of Example 2 is used as the initial compound.
Le traitement pour le dépôt de la couche d'oxydes est le suivant.The treatment for the deposition of the oxide layer is as follows.
La polyvinylpyrrolidone (PVP) est dissoute dans l'éthanol.Polyvinylpyrrolidone (PVP) is dissolved in ethanol.
A cette solution est ajouté le thiogallate de strontium. La suspension obtenue est dispersée à l'aide d'ultrasons et on ajoute ensuite la solution d'ammoniaque, puis le précurseur du zinc. Le silicate d'éthyle est introduit de façon continue pendant deux heures. Après la fin d'introduction du silicate d'éthyle, on effectue un mûrissement de deux heures. Les particules ainsi obtenues sont lavées à l'éthanol par filtration puis séchées à 50°C pendant douze heures.To this solution is added the strontium thiogallate. The suspension obtained is dispersed using ultrasound and then the ammonia solution is added, then the zinc precursor. The ethyl silicate is introduced continuously for two hours. After the end of introduction of the ethyl silicate, a two-hour ripening is carried out. The particles thus obtained are washed with ethanol by filtration and then dried at 50 ° C for twelve hours.
Les réactifs ont été utilisés dans les proportions suivantes :The reagents were used in the following proportions:
On obtient un produit encapsulé par une couche mixte silice/zinc.A product encapsulated with a mixed silica / zinc layer is obtained.
EXEMPLE 5EXAMPLE 5
Cet exemple concerne la préparation d'un composé selon l'invention comprenant une couche de silice. On part du même composé initiale que dans l'exemple 4 et on procède de la même manière mais sans utiliser un précurseur du zinc.This example relates to the preparation of a compound according to the invention comprising a layer of silica. We start from the same initial compound as in Example 4 and we proceed in the same way but without using a zinc precursor.
On utilise les réactifs dans les proportions suivantes :The reagents are used in the following proportions:
On obtient un produit encapsulé par une couche de silice. A product encapsulated with a layer of silica is obtained.

Claims

REVENDICATIONS
1- Composé de formule AB2S4 dans laquelle A représente un ou plusieurs alcalino- terreux, B au moins un élément pris dans le groupe comprenant l'aluminium, le gallium ou l'indium, caractérisé en ce qu'il se présente sous forme d'une poudre de teneur résiduelle en oxygène d'au plus 1 ,5%, plus particulièrement d'au plus 1 %.1- Compound of formula AB2S4 in which A represents one or more alkaline earths, B at least one element taken from the group comprising aluminum, gallium or indium, characterized in that it is in the form of a powder with a residual oxygen content of at most 1.5%, more particularly at most 1%.
2- Composé selon la revendication 1 , caractérisé en ce qu'il se présente sous forme d'une poudre constituée de particules entières ou non broyées, de taille moyenne d'au plus 10μm.2- Compound according to claim 1, characterized in that it is in the form of a powder consisting of whole or unground particles, of average size at most 10 μm.
3- Composé de formule AB2S4 dans laquelle A représente un ou plusieurs alcalino- terreux, B au moins un élément pris dans le groupe comprenant l'aluminium, le gallium ou l'indium, caractérisé en ce qu'il se présente sous forme d'une poudre constituée de particules entières ou non broyées, de taille moyenne d'au plus 10μm.3- Compound of formula AB2S4 in which A represents one or more alkaline earths, B at least one element taken from the group comprising aluminum, gallium or indium, characterized in that it is in the form of a powder consisting of whole or unground particles, of average size at most 10 μm.
4- Composé selon la revendication 3, caractérisé en ce qu'il présente une teneur résiduelle en oxygène d'au plus 1 ,5%, plus particulièrement d'au plus 1%.4- Compound according to claim 3, characterized in that it has a residual oxygen content of at most 1.5%, more particularly at most 1%.
5- Composé selon l'une des revendications précédentes, caractérisé en ce qu'il comprend au moins un dopant lui conférant des propriétés de luminescence.5- Compound according to one of the preceding claims, characterized in that it comprises at least one dopant giving it luminescence properties.
6- Composé selon l'une des revendications précédentes, caractérisé en ce que les particules constituant la poudre ont une taille moyenne d'au plus 5μm.6- Compound according to one of the preceding claims, characterized in that the particles constituting the powder have an average size of at most 5 μm.
7- Composé selon l'une des revendications précédentes, caractérisé en ce que les particules constituant la poudre ont une forme sensiblement sphérique.7- Compound according to one of the preceding claims, characterized in that the particles constituting the powder have a substantially spherical shape.
8- Composé selon l'une des revendications précédentes, caractérisé en ce que les particules constituant la poudre présentent un indice de dispersion σ/m d'au plus 0,7.8- Compound according to one of the preceding claims, characterized in that the particles constituting the powder have a dispersion index σ / m of at most 0.7.
9- Composé selon l'une des revendications précédentes, caractérisé en ce qu'il se présente sous forme d'une phase cristallographique pure.9- Compound according to one of the preceding claims, characterized in that it is in the form of a pure crystallographic phase.
10- Composé selon l'une des revendications précédentes, caractérisé en ce que B est le gallium. 11- Composé selon l'une des revendications précédentes, caractérisé en ce que A est le strontium.10- Compound according to one of the preceding claims, characterized in that B is gallium. 11- Compound according to one of the preceding claims, characterized in that A is strontium.
12- Composé selon les revendications 10 et 11 , caractérisé en ce qu'il se présente sous forme d'une phase cristallographique pure cubique.12- Compound according to claims 10 and 11, characterized in that it is in the form of a pure cubic crystallographic phase.
13- Composé selon l'une des revendications 5 à 11 , caractérisé en ce que le dopant est choisi parmi le manganèse divalent, les terres rares divalentes et le groupe comprenant les terres rares trivalentes en combinaison avec un alcalin, le dopant pouvant être plus particulièrement l'europium II, l'ytterbium en combinaison avec un alcalin.13- Compound according to one of claims 5 to 11, characterized in that the dopant is chosen from divalent manganese, divalent rare earths and the group comprising trivalent rare earths in combination with an alkali, the dopant possibly being more particularly europium II, ytterbium in combination with an alkali.
14- Composé selon l'une des revendications précédentes, caractérisé en ce qu'il se présente sous la forme d'une poudre dont les particules comprennent une couche à base d'au moins un oxyde transparent.14- Compound according to one of the preceding claims, characterized in that it is in the form of a powder, the particles of which comprise a layer based on at least one transparent oxide.
15- Composé selon l'une des revendications précédentes, caractérisé en ce qu'il se présente sous la forme d'une poudre dont les particules comprennent un composé du zinc déposé à leur surface.15- Compound according to one of the preceding claims, characterized in that it is in the form of a powder, the particles of which comprise a zinc compound deposited on their surface.
16- Composé selon la revendication 15, caractérisé en ce que le composé du zinc a été obtenu par réaction d'un précurseur du zinc avec de l'ammoniaque et/ou un sel d'ammonium.16- A compound according to claim 15, characterized in that the zinc compound was obtained by reaction of a zinc precursor with ammonia and / or an ammonium salt.
17- Procédé de préparation d'un composé selon l'une des revendications 1 à 13, caractérisé en ce qu'il comporte les étapes suivantes :17- Process for the preparation of a compound according to one of claims 1 to 13, characterized in that it comprises the following steps:
- on forme une solution ou une suspension comprenant des sels des éléments A et B et éventuellement du dopant;- A solution or a suspension is formed comprising salts of elements A and B and optionally of the dopant;
- on sèche par atomisation la solution ou la suspension;- The solution or the suspension is spray-dried;
- on fait réagir le produit obtenu à l'étape précédente avec du sulfure de carbone, du sulfure d'hydrogène ou avec un mélange de sulfure d'hydrogène et de sulfure de carbone.- The product obtained in the previous step is reacted with carbon sulfide, hydrogen sulfide or with a mixture of hydrogen sulfide and carbon sulfide.
18- Procédé selon la revendication 17, caractérisé en ce qu'on conduit la réaction avec le mélange gazeux précité à une température comprise entre 600 et 1000°C.18- The method of claim 17, characterized in that the reaction is carried out with the aforementioned gas mixture at a temperature between 600 and 1000 ° C.
19- Procédé selon la revendication 17 ou 18, caractérisé en ce qu'on utilise comme sels des nitrates. 20- Utilisation comme luminophore, notamment en cathodoluminescence, d'un composé selon l'une des revendications 1 à 16.19- A method according to claim 17 or 18, characterized in that nitrates are used as the salts. 20- Use as a phosphor, in particular in cathodoluminescence, of a compound according to one of claims 1 to 16.
21- Dispositif mettant oeuvre la cathodoluminescence, caractérisé en ce qu'il comprend un composé selon l'une des revendications 1 à 16. 21- Device implementing cathodoluminescence, characterized in that it comprises a compound according to one of claims 1 to 16.
EP97912275A 1996-10-31 1997-10-28 Compound with base of an alkaline-earth, sulphur and aluminium, gallium or indium, method of preparing same and use as luminophore Withdrawn EP0958244A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9613352 1996-10-31
FR9613352A FR2755122B1 (en) 1996-10-31 1996-10-31 COMPOUND BASED ON AN ALKALINE EARTH, SULFUR AND ALUMINUM, GALLIUM OR INDIUM, METHOD FOR PREPARING SAME AND USE THEREOF AS LUMINOPHORE
PCT/FR1997/001935 WO1998018721A1 (en) 1996-10-31 1997-10-28 Compound with base of an alkaline-earth, sulphur and aluminium, gallium or indium, method of preparing same and use as luminophore

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FR2755122B1 (en) 1998-11-27
KR100355729B1 (en) 2002-10-19
WO1998018721A1 (en) 1998-05-07
JP2000505041A (en) 2000-04-25
TW452594B (en) 2001-09-01
CA2270577C (en) 2002-07-30
CN1238744A (en) 1999-12-15
US6180073B1 (en) 2001-01-30
CA2270577A1 (en) 1998-05-07
US20010002246A1 (en) 2001-05-31
FR2755122A1 (en) 1998-04-30

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