Method of preparing moisture-resistant particles of electroluminescent phosphor

FIELD: luminescent materials.

SUBSTANCE: nitride coating precursor, in particular aluminum-, gallium-, or tin-containing metalloorganic nitride, is charged into reaction vessel 10a filled with electroluminescent phosphor, e.g. ZuS-Cu, and surrounded by heating means 30a using nitrogen as inert gas carrier. Precursor is passed through pipeline 32 open all over its length. Co-reagent, e.g. anhydrous ammonia is fed into lower part of vessel 12a through porous glass disk 12a. When vessel 10a is heated to 150-225°C, nitride coating precipitates on phosphor particles being in fluidized state. Phosphor bearing nonoxide coating is characterized by high brightness after 100 h use at high humidity.

EFFECT: enabled large-scale manufacture of phosphors.

3 cl, 2 dwg

 

The scope of the invention

The invention relates to a method for producing resistant to moisture particles of electroluminescent phosphor, the device for its implementation and the particle of the phosphor. More specifically, the invention relates to the electroluminescent phosphors treated to ensure water-resistant properties. In particular, the invention relates to the electroluminescent phosphors, with a significantly reduced properties water absorption and greatly extended service life and efficiency.

Background of the invention

Treated phosphors are known from U.S. patentsâ„–â„– 4585673; 4825124; 5080928; 5118529; 5156885; 5220243; 5244750 and 5418062. On the basis of some of the above patents, it is known that applying a protective coating can be used to cover the precursor and oxygen. See, for example, U.S. patent No. 5244750 and 4585673. According to certain other of the above patents, the process includes chemical vapor deposition to apply a protective coating by hydrolysis. It also indicates that the chemical vapour deposition at atmospheric pressure can be used for applying thin film coatings from aluminum nitride, obtained from precursors hexacis(dimethylamino)dialanine and anhydrous ammonia, on substrates of silicon, glassy carbon and glass. See, example is, "Application of a film of aluminum nitride by the method of chemical vapour deposition at atmospheric pressure at a temperature of 200-250°", Gordon et al., Journal Material Resources, vol. 6, No. 1, January 1991, "Application of thin films of aluminum nitride by the method of chemical vapour deposition", Gordon et al., Journal Material Resources, vol 7, No. 7, July 1992. Cm. also U.S. patent No. 5139825 and 5178911, Gordon, which also described transition metal nitrides and metal nitrides, for example, gallium and tin, respectively. In U.S. patent No. 5856009 described high-temperature process (e.g., 300-700° (C) for coating the silicon nitride on the pre-deposited on the particles of the phosphor heat-resistant coating. The patent application U.S. S.N. 09/175787 filed 10/20/98 (included in this description by reference), which claimed priority to provisional application S.N. 60/072510 filed 01/12/98, discloses a method of applying a nitride coatings using high reactivity hexacis(dimethylamino)dialuminium, which was difficult to obtain in commercial quantities. Provide a method to obtain water-resistant electroluminescent phosphors would be a significant achievement in this field of technology. Another great achievement was the provision of a method, implemented in the absence of water or water vapor. Further achievement in the area and equipment would increase the efficiency and lifetime of such phosphors, obtained in this way. And the next achievement in the art would be the provision of an electroluminescent phosphor with a non-oxide coating, such as, for example, the nitride coating metal applied directly to the particles of phosphorus at a low temperature, for example about 100°so that the operational characteristics of the phosphorus is not adversely affected. And another achievement in the art would be the provision of a method of using high reactivity materials for phosphorus coated in commercial quantity.

Description of the invention

The invention, therefore, is to eliminate the disadvantages of the prior art.

Another object of the invention is improving moisture phosphors.

Another object of the invention is the provision of a method of obtaining a moisture-resistant phosphors, which does not use water or water vapor, or oxygen.

And another object of the invention is the provision of a method and equipment for production of commercial quantities of phosphors coated with a nitride coating, in such a way and install using materials with high reactivity.

These objectives are achieved in one aspect of the invention by which Holocene particles of phosphorus coated with the nitride coating metal. This coating may be conformal to the surface of the particles. Under conformal mean a coating that conforms to the contour of the surface of the individual particles.

Objectives of the invention are achieved by creating a method of producing water-resistant particles of electroluminescent phosphor which includes the stage of introduction of the inert gas in the reaction vessel, loaded with particles of phosphorus; heating the reaction vessel to the reaction temperature; introducing into the reaction vessel predecessor nitride coating in such a way to avoid limiting reactions; introduction of coreagent in the reaction vessel and maintaining a flow of inert gas flow coreagent and feed precursor in a period of time sufficient to make the particles of phosphorus moisture.

Objectives of the invention are also achieved by creating a method of producing water-resistant phosphors, which includes the introduction phase in the reaction vessel inert gas loading in the reaction vessel, particles of phosphorus; heating the reaction vessel to the reaction temperature; introducing into the reaction vessel predecessor nitride coating in such a way as to avoid limiting reactions; introducing into the reaction vessel coreagent and maintaining a flow of inert gas flow coreagent and feed precursor in the course of time the Yeni, sufficient to coat the particles of phosphorus.

Particles with phosphorus nitride coating obtained in this way have excellent performance and high brightness in the lamp after 100 hours of use in high humidity conditions (e.g., >95%) and can be obtained in real commercial quantities, for example in quantities of 50 kg

Brief description of drawings

Figure 1 represents a diagram of a method of coating the phosphors in accordance with the prior art, and figure 2 presents a diagram of the method according to the invention.

The preferred method of carrying out the invention

For a better understanding of the present invention, together with other and further objectives, advantages and features, reference is made to the following description and the accompanying claims, which should be read in conjunction with the above drawings.

In method embodiments of the invention in the prior art, shown in figure 1, the reaction of the coating was carried out in a reaction vessel with a fluid using a gas layer that includes graboplast glass tube 10 with an outer diameter of 1 inch (2.54 cm), mounted getreceiver the glass disk 12 and is surrounded by a heater 30 to maintain the reaction temperature. Use the range of the phosphorus 16 was an electroluminescent phosphor type 723 (ZnS:Cu), commercially available from the company Osram Sylvania Inc., Towanda PA, and this phosphorus was pseudovirus by injection box of inert gas, such as nitrogen, from the supply 18. Nitride coating (which may contain some amounts of hydrogen and aluminum nitride) was obtained by reacting anhydrous ammonia and hexacis(dimethylamino)dialuminum (Al2(N(CH3)2)6. However, there is no reason to deny that it is possible to use other metal nitrides, especially, for example, those containing gallium or tin. Aluminiumhydride predecessor, which was received from the company Strem Chemicals, Newburyport, MA, included bubbler stainless steel. The bubbler is maintained at a temperature of 100°and predecessor directed into the reaction vessel with the help of the media, is a purified nitrogen from supply 22. Flowing the nitrogen precursor was sent up the dispenser 12 of frettoloso glass lines, supported at a temperature of 20-30°above the temperature of the bubbler. Anhydrous ammonia coreagent 24, commercially available from the firm Matheson Chemicals, Gloucester, MA was passed through the installation of 26 monitoring of mass flow before entering the fluidized bed at a set in the centre of the glass tube 27 having a tip 28 of frettoloso glass. Anhydrous ammonia before his post is warming in the layer was diluted with purified nitrogen. Nitrogen carrier was further purified by passage through purifier Centorr, and then through a scrubber Matheson Nanochem. Ammonia was also passed through the purifier Nanochem.

System for passing gas was made of pipes and fittings made of stainless steel. To connect glass parts of the reactor with parts of the pipeline for gas used seal that connects the glass to the metal.

This method worked well as described, in the installation of small quantities of phosphorus, for example of the order of 40 grams or so. However, attempts to increase the productivity up to the commercial level (when quantities are expressed in kg), there were problems.

The problem was identified as arising due to the high reactivity of the nitride precursor, in this case hexacis(dimethylamino)dialuminum. This material reacts with grabpointer drive from frettoloso glass, nitride coating the inner side of its pores. This is especially the case at higher temperatures the reaction vessel, about 150-225°C. Within a very short period of time, the pores of the disk clogged, stopping the necessary reaction deposition of nitride coatings on suspended particles of phosphorus.

The solution of this problem was carried out by creating a device and method shown in figure 2. is provided in figure 2, the reaction vessel 10A, which can be a vessel of stainless steel with a diameter greater than 10 inches (15,4 cm)surrounded by a suitable heating device 30A to bring the reaction vessel to a temperature of the coating is between 150 and 225°contains the precursor coating is introduced into the vessel so as to avoid limiting reactions. In the illustrated embodiment, this is implemented by capturing predecessor nitrogen from feed 22A and transfer the captured predecessor of the upper part of the reaction vessel 10A through the pipe 32, the open throughout its length and having the tip of frettoloso glass. Coreagent, which in this case diluted with anhydrous ammonia can be fed from the bottom of the vessel 10a and pass through a porous glass disk 12A. The initial supply of inert gas which may be nitrogen and which is used for the initial fluidization of particulate phosphorus can also be done from the bottom of the vessel 10A through the disk 12A.

Thus, by submitting a predecessor nitride coating so as to avoid limiting reactions, get covered with the nitride phosphors in commercial quantities economical way.

Despite what has been shown and described what is at present considered the preferred embodiment of the invention, special the Stam will be clear, there are various changes and modifications without departure from the invention as defined in the attached claims.

1. The method of obtaining resistant to moisture particles of electroluminescent phosphor, including the introduction of inert gas into the reaction vessel, equipped with a porous disc at one end, loading in the reaction vessel, particles of phosphorus, heating the reaction vessel to the reaction temperature and the introduction of nitride coating precursor into the reaction vessel so that he would pass over the disk, and an introduction to this reaction vessel coreagent, and the flow of inert gas, coreagent and the precursor is maintained for a time sufficient to make the particles of phosphorus moisture.

2. A device for obtaining resistant to moisture particles of electroluminescent phosphors with nitride coating in commercial quantities using a fluidized bed, comprising a reaction vessel having a size providing commercial quantities of phosphorus, on the first end of which is porous getreceiver drive for at least the first inert gas supply and initial fluidization of phosphorus, the device is equipped with means for feeding predecessor nitride coating, a sh is at the second end of the reaction vessel at a distance from its first end, and means for feeding media to transfer predecessor and supply coreagent through the disk.

3. Particle phosphor, characterized in that it is obtained by the method according to claim 1.



 

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