MXPA01003696A - Oxynitride encapsulated electroluminescent phosphor particles - Google Patents

Abstract

Encapsulated electroluminescent phosphor particles and a method of making same. Each electroluminescent phosphor particle is encapsulated by a substantially transparent metal oxynitride coating. The coating provides the phosphor particle with reduced sensitivity to humidity accelerated decay.

Description

PARTICLES OF PHOSPHORUS ELECTROLUMINISCENTS ENCAPSULATED IN OXINITRIDE Field of the Invention The present invention relates to electroluminescent phosphorus particles, particularly, to phosphorus particles which are encapsulated in a moisture resistant coating exhibiting a high pollen luminescence and, more particularly, to such encapsulated electroluminescent phosphor particles. with a protective metallic oxynitride coating that has improved electrical, chemical, thermomechanical, or surface characteristics. The present invention also relates to a method for making such encapsulated phosphor particles.

Background of the Invention Phosphorus particles are used in a variety of applications such as flat panel displays and decorations, cathode ray tubes, or lighting devices REF: 128239 fluorescent. The emission of light or luminescence by phosphorus particles can be stimulated by the application of various forms of energy including electric fields (electroluminescence). Electroluminescent phosphorus ("EL") has a significant commercial importance. The luminescent brightness of such phosphors and the "maintenance" of this brightness is of two criteria typically used to characterize phosphor particles.

Luminescent brightness is typically reported as the amount of light emitted by the target phosphorus when excited. Due to the sensitivity of the phosphor emission brightness to vary the excitation conditions, it is often useful to report the brightness of the phosphor as the relative brightness instead of the absolute brightness. "Maintenance" refers to the relation to which the phosphor loses brightness (this is decayed) with the time of operation. The decay ratio is substantially increased if the phosphor particles are subjected to high humidity conditions while being operated. This effect of humidity or high humidity as "decay accelerated by moisture", ' EL phosphorus particles are the most commonly used in thick film constructions. These devices typically include a layer of an organic material having a high dielectric constant that forms a matrix for the charge of phosphorus particles. Such layers are typically coated on a plastic substrate having a transparent front electrode. A posterior electrode is typically applied to the back of the phosphor layer with a dielectric layer interspersed therewith. When an electric field is applied through the electrodes, the near portions of the layer emit light as the phosphor particles are excited in it.

Organic matrices and substrate materials, as well as organic coatings applied to individual particles, are typically ineffective in preventing the decay of brightness caused by diffusion of water vapor to the phosphor particles. For this reason, the electroluminis cent-thick film devices are enclosed in relatively thick envelopes, for example, from 25 to 125 microns, of moisture resistant polymeric materials. However, such wraps are typically expensive, result in unlighted margins, and have the potential to exfoliate, for example, under heat.

To improve its resistance to moisture, the phosphor particles are encapsulated in an inorganic coating, such as a metal oxide coating. Inorganic coating techniques have been used with varying degrees of success. Hydrolysis-based processes for encapsulating EL phosphor particles in an inorganic coating, eg, chemical vapor deposition based on hydrolysis (CVD), have typically been shown to be the most successful. In CVD processes based on hydrolysis, oxide and water precursors are used to form the protective coating. Such CVD processes based on hydrolysis have been able to produce encapsulated phosphorus particles not sensitive to moisture, while minimizing the processes related to the damage to phosphorus and retaining an initial luminescent brightness at the to.

In this way, there are phosphor coatings that provide protection against decay accelerated by moisture, but there is still a need for new coating materials that provide moisture protection, and that provide electrical, chemical, thermomechanical, or electrical characteristics. improved surface.

Brief Description of the Invention The invention provides novel encapsulated phosphor particles, each having a substantially transparent metallic oxynitride coating. Encapsulated phosphorus exhibits reduced sensitivity to decay accelerated by the moisture of the luminescent brightness. Additionally, the present invention involves a method that results in encapsulated particles.

Each of the encapsulated particles of the present invention includes a phosphorus particle of an electroluminescent phosphorus material that exhibits an accelerated decay to moisture in the presence of moisture. The phosphor particle is coated with substantially transparent metallic oxynitride. The metal oxynitride sufficiently encapsulates the phosphor particle to give the particle a reduced sensitivity to decay accelerated by moisture.

Phosphorus particles are generally made of at least one phosphorus based on zinc sulphide, a phosphorus based on calcium sulfide, a phosphorus based on zinc selenide, a phosphorus based on strontium sulfide or a combination of phosphorus compounds. Phosphorus particles are sensitive to decay accelerated by moisture and thermal degradation if exposed to high temperatures.

In accordance with the present invention, a metal oxynitride coating sufficiently encapsulates the phosphor particle to limit phosphorus exposure to moisture or water. The metal oxynitride coating includes one or more layers of a simple metal oxynitride, a mixed metal oxynitride, or a combination of such layers. One or more layers are generally applied in such a way that the total thickness of the metal oxynitride coating is in the range of about 0.03 microns to about 1.0 microns. The metal component in the metal oxynitride is preferably selected from aluminum, boron, silicon, titanium, zirconium, or a combination of the preferred metals. Preferably, the oxmitride coating of the present invention has a nitrogen to oxygen molar ratio in the range of about 4: 1 to about 1: 4.

The metal oxynitride coating of the present invention exhibits reduced sensitivity to chemical degradation caused by exposure to condensed moisture or otherwise liquid water, (i.e., high resistance to corrosion in a liquid water environment). It is desirable for the present metal oxynitride coating to be sufficiently non-porous. The non-porous coating provides a phosphor particle that exhibits reduced sensitivity to moisture. Preferably, the coating is sufficiently non-porous and is also sufficiently resistant to the chemical degradation (ie, corrosion) of the water such that the encapsulated particle can survive an immersion in an aqueous solution of 0.1 molar silver nitrate, with a substantial resistance to shade. Such a silver nitrate test is typically used to confirm the permeability of a phosphor coating. Being more resistant to enable water-induced corrosion, the present metallic oxynitride coating survives for long periods in a liquid water environment. Additionally, the encapsulated particle of the present invention preferably has an initial electroluminescent brightness of about 50% or more of the initial elementary luminescent brightness of the uncoated phosphor particle.

The present invention also provides a novel method for making such particles of phosphorus encapsulated. The method comprises a bed of phosphorus particles, each of which exhibits a decay accelerated by moisture in the presence of moisture; providing one or more precursors comprising a vapor phase metal containing a precursor, a vapor phase nitrogen containing a precursor, and a vapor phase oxygen containing a precursor; and exposing the bed to the precursors in such a way that the precursors react chemically and encapsulate each of the phosphor particles with a coating of metallic oxmitride. One or more of the precursors used in the present invention may include compounds in which the metal component and the nitrogen component are present in a single precursor. Additionally, a simple precursor containing the metal, nitrogen and oxygen component, may be used to form the metal oxynitride coating of the present invention. The resulting coating is substantially transparent and sufficiently encapsulating to provide the phosphor particle with reduced sensitivity to decay accelerated by moisture.

Detailed description of the. < nvention In accordance with the present invention, it has been discovered that a metallic oxynitride coating can be applied to a phosphor particle to protect the particle from decay accelerated by moisture.

The particles used in the present invention are generally phosphor particles that exhibit a luminescence or light emission during stimulation by an electric field. The electroluminescent phosphor particle of the present invention may comprise, for example, a phosphorus based on zinc sulphide, a phosphorus based on calcium sulfide, a phosphorus based on zinc selenide, a phosphorus based on strontium sulfide, or combinations thereof. The phosphorus used in the present invention can be formulated in accordance with conventional practices. For example, phosphorus based on zinc sulphide is well known and commonly includes one or more such compounds as copper sulfide, zinc selenide, and cadmium sulfide in a solid solution within the crystal structure of zinc sulphide or as second phases or domains within the structure of the particle. The phosphor particles used in the present can be of many sizes, typically depending on the size of the desired application extension. Each of the phosphor particles used in the present invention demonstrate the undesirable characteristics of accelerated decay when exposed to moisture or water The metallic oxynitride coating is used to protect the phosphor particles from decay accelerated by moisture. As used herein, a metal oxynitride coating refers to a material made primarily of at least one metal, nitrogen and oxygen. For purposes of the invention, the coating is defined as one or more layers of a single metal oxynitride, a mixed metal oxynitride, or a combination of such layers. The coating is substantially transparent to allow passage of light emitted from the phosphorus. Additionally, the coating is sensitive to Caceration accelerated by moisture. Generally one or more layers are applied in such a way that the total thickness of the metal oxynitride coating is in the range of about 0.03 microns to about 1.0 microns. Coatings that are very thick may tend to lose transparency and result in reduced gloss.

The metal component of the oxmitride coating is preferably selected from the group consisting of aluminum, boron, silicon, titanium, zirconium, or combinations thereof. The molar ratio of the components in the oxynitride coating indicates that the nitrogen is included in the coating at levels exceeding trace amounts and thus is sufficient to increase or improve the electrical, chemical, thermomechanical, or surface characteristics of the coating on a metal oxide coating essentially free of nitrogen. The oxygen content of the coating exceeds the levels of OR? "^ - xáÉÉ ^ i & iiSl - ^ - ^ SS ^ x'-clue that they can present | f |, e in pure nitride coatings In general, the oxygen component of the oxynitride coating provides transparent properties to enable the transmission of visible light and to improve the desired physical properties The transparency of the metallic oxynitride coating is sufficient to allow a useful level of visible light of the phosphorus to pass through the coating.The oxygen nitrogen molar ratio of the oxynitride coating is preferably in the range of about 4: 1 to about 1: 4, more preferably about 3 or 2: 1 to about 1: 2 or 3, and even more preferably about 1: 1. The metal component in a metal oxynitride coating can vary significantly due to the valency of the particular metal used in the coating. s elements and compounds, including those originating in precursor materials or phosphorus particles, which can be generated in the form of coating on the phosphorus particles under conditions that are at least * * * similar to those described herein.

The method of the present invention comprises: providing a bed of phosphor particles, each of which exhibits a decay accelerated by moisture in the presence of moisture; providing one or more precursors comprising a precursor containing a metal in the vapor phase, a precursor containing nitrogen in the vapor phase; and a precursor containing oxygen in the vapor phase; exposing the bed to the precursors in such a way that the precursors react chemically and encapsulate the phosphor particles with a metallic oxymethide coating. One or more precursors include any precursor capable of forming the desired metal oxynitride for the coating. The resulting coating is substantially transparent, resistant to chemical degradation of moisture and water, and sufficiently encapsulating to provide the phosphor particle with reduced sensitivity to decay accelerated by moisture. ? * > fessi The method of the present invention is generally practiced through the use of conventional chemical vapor deposition (CVD) techniques.; For example, the metal oxynitride coating will be applied to the phosphorus particles using CVD at atmospheric pressure or CVD increased by plasma. Alternatively, other conventional coating practices, such as disintegration, can be used to apply the metallic oxynitride coating. The coating process includes exposing the phosphorus particle bed to the precursor gas mixture to coat each of the phosphor particles by a vapor phase reaction of one or more precursors including a vapor phase metal, a precursor that contains nitrogen, and a precursor that contains oxygen. The reaction occurs at a temperature under conditions that minimize at least substantially the thermochemical related damage to the phosphor particles that are encapsulated. By practicing the method of the present invention, the uncoated phosphor particles are placed in a reactor and '"" "" ^ S ^ - ^^ - ^^ T' heat to the appropriate temperature. In order to form coatings that sufficiently encapsulate the phosphor particles, the particles are preferably still agitated in the reaction chamber. Illustrative examples of methods useful for stirring phosphor particles include stirring, vibrating, or rotating the reactor, stirring the particles, or suspending them in a fluidized bed. In such reaction chambers, the particles can be stirred in many different ways such that essentially the entire surface of each of the particles is exposed and the particles and reaction precursors can intermix well. Typically, a preferred reaction chamber is a fluidized bed reactor. Fluids typically tend to effectively prevent agglomeration of the particles, allowing uniform mixing of the reaction precursor particles and materials, and providing more uniform reaction conditions, thereby resulting in highly uniform encapsulation characteristics.

Although it does not require in many instances, when phosphorus particles are used which tend to agglomerate, it is desired to add fluidizing aids, for example, small amounts of SiO 4 vapor. The selection of such auxiliaries and useful amounts thereof can be readily determined by those of ordinary skill in the art.

The desired precursor materials in the vapor phase are then added to the reactor where a vapor phase reaction occurs to form the coating of a metal oxynitride on the surfaces of the phosphor particles. The precursor containing the metal in the vapor phase is generally a metal compound that is capable of reacting with other precursor gas streams to provide the metal component of the metal oxynitride coating. Metal chlorides, for example, are typically used in CVD processes as a metal source. Additionally, organic metal sources can be used to produce the coating of the present invention. For example, alkyl silanes can be used to provide a source for the "silicon" of the metal oxynitride coating. Examples of other volatile metals containing precursor compounds include metal alkyls, metal alkoxides, metal carbonyls, and metal dicetonates. More than one metal precursor can also be used in order to form the mixed metal oxynitride coatings of the present invention.

The nitrogen coating precursor of the present invention is generally any nitrogen compound that is capable of reacting with the other vapor phase precursor stream to form the desired coating. Preferably, ammonia is used as the nitrogen-containing precursor when separately used metal-containing and oxygen-containing precursors are used. The precursor that contains oxygen is usually oxygen or water. However, other conventional sources of oxygen suitable for CVD applications can be used in accordance with the present invention.

Alternatively, metal and nitrogen source, may be provided in at least one sicilic compound. The use of compounds having low temperature CVD reactions allows metal-nitrogen bonding without the use of plasma, thus reducing the thermo-chemical degradation of the phosphor particles. An example of compounds having a metal-nitrogen bond are amino-methyl complexes (eg, tetrakis dimethyl amino titanium), of the preferred metals of aluminum, boron, silicon, titanium, or zirconium. These compounds can be used both as the metal and nitrogen source, or can be used in conjunction with other metal-containing precursors or nitrogen-containing precursors to form the metal oxynitride coating.

The metal oxynitride coating of the present invention can also be produced through the use of precursors from simple sources including metal, nitrogen and oxygen. For example, a vapor phase precursor, containing a metal, alkylamino ligands and oxygen-containing ligands, such as alkoxy or carboxylate groups, may be used in the inventive processes. • The precursor streams are directed to the reaction chamber in the vapor phase. A technique for acquiring the vapor phase precursor materials and adding them to the reaction chamber is the bubbling of gas streams, preferably inert, referred to herein as the carrier gas, through a pure liquid of the precursor material and then in the reaction chamber. Illustrative examples of inert gases that can be used herein include argon and nitrogen. Oxygen and / or air can also be used with the proviso that the desired N / O ratio can still be maintained. However, the introduction of excessive amounts of oxygen into the reactor can prevent the formation of the desired oxynitride coating with the required nitrogen content. Additionally, it may be necessary to release it in a previous diffusion, with an opening of the reactor or to release a nitrogen purge to obtain the desired oxidride coating. An advantage using carrier gas is that the currents of BWKwWpl Carrier / precursor gas can be used to fluidize the phosphor particles in the reaction chamber, thereby facilitating the desired encapsulation process. In addition, such a technique provides means for easily controlling the rate of introduction of the precursor materials into the reactor.

The precursor gas streams are exposed to the phosphorus compounds where they react and form the metal oxynitride coating of the present invention. When the coating is formed, all the currents are transported in the reactor at the same time. When a layered metallic oxynitride coating is formed, the precursor streams for the initial layer are first transported into the reactor until the particles are encapsulated. Subsequent layers are then formed by directing additional precursor streams to the encapsulated particles. It may be desired for the outer layer comprising a metal oxide coating on the metal oxynitride coating. «? * --- ^ -» '^ ^ te? jj ^? jj & & The "flow ratios of the precursor are adjusted to provide an adequate deposition ratio and to provide a metal oxynitride coating of the desired quality and character.The flow ratios are adjusted in such a way that the ratios of precursor materials present in the The reactor chamber promotes the deposition of oxynitride on the surface in the phosphor particles.

Optimum flow rates for a particular application will typically depend in part on the temperature inside the reaction chamber, the temperature of the precursor streams, the degree of particle agitation within the reaction chamber, and the particular precursors that are used . Those skilled in the art will be able to establish useful flow relationships through experimentation. It is desired for the flow ratio of the carrier gas used, to transport the precursor materials to the reaction chamber to sufficiently stir the phosphor particles as desired and also to transport optimum amounts of precursor materials to the chamber.

It is also desired that the precursor materials which deliver sufficiently high vapor pressures for sufficiently large quantities of the precursor material can be transported to the reactor for the coating process to proceed in a conveniently fast relation. Precursor materials that have high vapor pressures typically provide faster deposition ratios than precursor materials that have low vapor pressures, thereby allowing the use of shorter encapsulation times.Precursor sources can be heated to increase the pressure of the precursor. vapor of the material In order to prevent condensation between the heated source and the reactor, they may need to heat the tube or other means used to transport the precursor material to the reactor In many instances, such as those tabulated below, the materials precursors can be formed in pure liquids at room temperature. In some cases, the precursor materials can be enabled with solid solids that can be made up The precursor materials which are most desirable as those1 * which are capable of forming the present coatings at temperatures that are low enough not to cause substantial damage to the phosphor particles. It is desired for the reactor temperature to be maintained at temperatures that help ensure that the coatings are deposited sufficiently encapsulated to provide the desired protection against decay accelerated by moisture, and are resistant to corrosion of liquid water, while avoiding the intrinsic thermal damage or adverse thermochemical reactions on the surfaces of the particles that cause an undesirable loss of the initial brightness. The . The temperatures required to form the oxynitride compounds in CVD reactions tend to be greater than certain reactions to form oxides. Nevertheless, conditions tend to be less strongly oxidizing and reactive precursors, or precursors containing metal-nitrogen bond, can be employed as exemplified herein, to reduce or minimize phosphorus ions. Those that run at temperatures that are very low may tend to result in coatings that do not provide the desired resistance to decay accelerated by moisture. Such coatings are not sufficiently impervious to moisture because they are considered to have a more open structure or a structure containing unreacted or excess trapped precursor components. Encapsulation processes that run at temperatures that are too high may result, for example, in a reduction in the brightness of the roluminiscent ect, undesirable changes or changes in the color of the light emitted by the target phosphorus, or the degradation of the characteristics of intrinsic decay of the subject phosphor material.

The encapsulated phosphor particles of the present invention provide both reduced sensitivity to moisture and improvement in electrical, chemical, thermomechanical, or surface characteristics. The resulting coatings of the present invention are sufficiently non-porous to provide a phosphorus particle with substantial resistance to shadowing when the encapsulated particle is exposed to silver nitrate. Additionally, the encapsulated phosphor particles retain an accepted level of their initial luminescent brightness. Preferably, each of the particles encapsulated has an initial electroluminescent brightness that is equal to or greater than about 50% of the initial troluminiscent brightness of the phosphor particle. More preferably, the initial particle luminescence ect glow encapsulated is equal to or greater than about 80% of the initial electron troluminiscent brightness of the phosphor particle.

The following non-limiting examples further illustrate the present invention. Unless stated otherwise, the following test procedures were used in the examples. The particular materials and amounts recited in these Examples, as well as in other conditions and details, are to be interpreted = ^^^^^^^^ broadly built to restrict the invention in no way.

EXAMPLES Encapsulation process.

The coating process used to prepare the Examples of the present invention was a conventional encapsulation process, similar to that described in U.S. Pat. No. 5,156,885, which is incorporated herein by reference in its entirety. Fluidized bed reactors 40 millimeters in diameter (150 g samples), or 20 mm reactors (smaller samples) each consisting of a porous glass funnel with a simple bottom entry and containing a glass were used. porous of appropriate size (eg, size C or D) in the bottom of the reactor bed (this is porous base glass) and the phosphor particles on the surface of the porous base glass. Each of the reactors was modified to be heated to a desired temperature in a controlled manner (for example, by Saife to immersion in an oil bath P ^ heating with ur, pint of wire). It is a gas tube 58 »separated to introduce each of the precursor vapors in each -one of the reactors. Instead of using a porous glass, the end of each of the inlet tubes was capped to disperse the precursor vapors. Once this was done, the capping was such that the precursor vapors were bubbled from the inlet tubes and into the phosphor particles placed under the porous glass.

For each of the reactors, the gas inlet tubes for the precursors were inserted into the fluidized bed, spread through the phosphor particles to introduce the precursor vapor stream (ie, the carrier gas and the precursor vapors) in the reactor just below the nearby porous glass base or at the bottom of the phosphor particles (this is the reaction form). As an alternative, these inlet tubes can be arranged through one side of the reactor.

They kept everyone around room temperature except as noted. Nitrogen was used as the carrier gas.

Test procedures Brightness tests The initial electroluminescent brightness (B0) and retained from the examples was determined using an oil cell and an oil-grid saturated air test, respectively, similar to those described in U.S. Pat. No. 5,156,885 previously incorporated. The resulting data is reported as a percentage of the initial brightness of the uncoated phosphor or - of the encapsulated particle, respectively for an initial and retained brightness. s- ^ ¡a »< faith?".

The particles of the solution test the porosity of the metallic oxynitride coating. Uncoated phosphor particles may turn dark, black when exposed to pentane nitrate. Encapsulated particles that turn light colors indicate an acceptable result.

N / O ratio. It is estimated from the spectroscopic analysis of the random Auger electron, for which a depth profile is obtained disintegrating through the coatings.

Fiche specifications forums Commercially available phosphor particles of Silvania type 729 are used in the examples. Type 729 phosphorus is a phosphorus based on zinc sulphide.

Examples 1-6 Oxinitride / O Coatings The phosphor particles are encapsulated with a coating of aluminum oxynitride in the encapsulation process previously described. Approximately 150 grams of phosphorus is placed in the reactor at atmospheric pressure. The reactor is maintained at the temperature (° C) indicated in Table 1. Aluminum trichloride is used as the metal-containing precursor. Aluminum trichloride, in powder form, is maintained at a temperature of 150 ° C and evaporated by sublimation. The aluminum trichloride vapor is introduced into the reactor by a flow of nitrogen carrier gas through the source vessel at the indicated ratios (cc / minutes). A separate stream of ammonia is introduced simultaneously into the reactor as indicated in the Table. Air is also introduced into the reactor for some of the runs. The total coating time (hours) is also indicated in Table 1.

TABLE 1 Example Phosphorus A1C13 NH3 > A? Re Temp Time B0 N / 0 (gram) (sccm) (SCCBWSCCIII) (° C) (hrs) (%) 1 150 500 500 0 350 10 2 150 500 500 0 350 10 3 150 500 500 0 500 10 38 4: 1 4 150 500 500 10 500 10 67 150 500 500 50 500 10 15 6 150 700 400 40 550 2.5 38 2: 3 Silver Nitrate Test: Examples 1 and 2 had a poor resistance to silver nitrate. Very high deposition temperatures were needed. Samples 3-6 had a good initial silver nitrate resistance (light brown color), but darkened after several hours to a few days, possibly due to corrosion of the coatings.

Gloss: Examples 3 and 4 showed an increase in brightness corresponding to the use of air in the reaction in addition to a simple black diffusion (which had an N / O ratio of 4: 1). With . ^ tf rffrfMJtfirifffifi based on the two N / 0 ratios measured, sample 4 is expected to be around 1: 1 or slightly higher.

Examples 7-11 Silicon Oxynitride Coatings The Examples were encapsulated in a manner similar to that used for Examples 1-6, except that the metal-containing precursor was tris dimethylamino silane (TDAS). The TDAS remained as a pure liquid at room temperature before being vaporized. The process conditions of the subsequent results are reported in Table 2 TABLE 2 E] ep ?. TDAS NH3 Air Phosphor N2 Temp. Time B0 N / 0 (gram) (sccm) (sccm) (sccm) (sccm) (° C) (hrs) (%) 7 30 11 65 0 350 5.5 45% 1: 3 8 30 11 65 10 350 5.5 51% 1: 3 9 30 11 65 0 500 5.5 53% 1: 1 30 11 65 10 500 5.5 73% 2: 3 * 11 150 400 500 50 (500 500 5.0 80% * is the highest oxygen content near the surface for this example.

Platinum Nitrate Test.?: "All the examples had silver nitrate tests of good to excellent initials and extended (lightly brown coloration for several weeks of exposure) including Examples 7 and 8.

Gloss: Examples 7 and 8 tend to have a moderate brightness despite having a higher oxygen content. Examples 9-11 had higher nitrogen contents, and show an increase in initial brightness of up to 80% for an increased oxygen content despite being under these conditions.

Examples 12-14 CVD Augmented by Plasma In Examples 12-14, silicon oxynitride coatings were deposited by plasma enhanced CVD. The reaction system comprises a quartz tube four inches in diameter (101.6 mm) to which a vitrified quartz tray is fused to retain the phosphor particles. The precursors were trimethylsilane, TMS, NH3 and 02. The conditions of processing of re-report-, < μ Table 3.

Reactor gases were inserted through a TMS gas and the it's oxygen The gases were previously mixed and introduced into the bottom of the quartz tube. The ratio of the gas tubes was adjusted to initiate the fluidization of the phosphor particles on the vitrified quartz tray. The gases were released from the upper part of the quartz tube by means of a pumping line attached to a vacuum pumped pump. The stack is made from a roots blower (200 cfm roots vacuum blower manufactured by Alcatel) placed on the front by a mechanical pump (30 cfm double stage mechanical pump manufactured by Alcatel). A separating particle is installed between the quartz tube and the pumping stack in order to prevent the phosphor particles from being removed from the pumps.

Plasma is generated inside the quartz tube by means of a copper tube cooled by water (a twist of two turns) connected in parallel to a variable vapio capacitor (Jennings capacitor of 2300 pico-Farát) - ,, the variable capacitor is adjusted so that the H'zo of the two turns and the capacitor form a circuit, resonant at 13 Mhz This resonant LC circuit is handled by a class C oscillator (for an explanation of such an oscillator, see for example in ' 'Industrial High frequency Electric Power', by E. May, page 130, Chap an &Hall, London (1949).) The power in the oscillator tray varies between 0.9 and 2.5 kW.The current power released from the plasma was significantly smaller, calculated to be in the range of 0.4-1.0 kW.

The precursors were trimethyl silane, TMS, NH3 and 02. The processing conditions and results are reported in Table 3. Samples collected from the walls of the quartz tube were analyzed by electron auger spectroscopy and the results are reported in the Table 3 TABLE 3 Example Phosphorus TMS NH3, 02 P Time B0 N / 0 (gram) (sccm) (sccm > '(scc) (torr) (hrs) (%) 12 100 5.4 239 184 550 24 86% 6: 100 13 100 11 290 105 390 22.5 84% 7:10 14 100 16.4 211 105 360 18 Examples 15-20 Oxin truro coatings Titanium Samples 15-20 were manufactured in a manner similar to Examples 1-11, but tetrakis dimethylamino titanium was used as the metal-containing precursor. This precursor was heated up to 95 ° C for Examples 18-20, to increase the vapor pressure and the corresponding flow of the precursor. Processing conditions and subsequent results are reported in Table 4.

TABLE 4 Example Phosphorus TDAT NH3 Air Tempe- Time B0 (! N / 0 (gram) (sccm) (sccm) (sccm) ratura (hrs) (° C) 15 15 500 50 300 Ma s 3.5: 1 co r to 16 15 500 50 O 400 5 < 10% 2.0: 1 17 15 500 50? B 400 5.5 22% 1.5: 1 18 150 600 420 100 500 3 21% 19 150 600 420 250 500 3 32% 20 150 500 1000 1000 500 4 33% Resistance to silver nitrate: Examples 15-17, deposited at 300 ° C-400 ° C, had a poor to moderate discoloration resistance. Examples 18-20, placed at 500 ° C, had excellent long term resistance to discoloration. Examples 18-20 were tested to retain the gloss after a 100% RH operation. After 24 hours, they retained 50%, 22% and 63%, respectively, against less than 10% for the uncoated phosphorus.

Br i lio: Examples high in nitrogen had the brown / gold characteristics of titanium nitride and reduced brightness. Example 15 was also a driver for this test. The Examples were coated at 500 ° C with higher air flows that had some improvement in the initial brightness, and based on their appearance, flows, and N / 0 data for the lower temperature samples had similarly N / 0 ratios close bottoms around 1: 1.

The following prophetic Examples, which were not executed, further demonstrate the invention.

Prophetic Example 1 Phosphorus particles are placed in a reactor similar to that used in the previous examples. The reactor contains the phosphorus particles maintained at a temperature within the range of about 400 ° C to about 600 ° C. The metal-containing precursor gas streams separated from a silicon tetrachloride and aluminum tetrachloride were co-carried to the reactor at ratios giving a total flow equivalent to those of Examples 1-4. The air precursor gas and ammonia streams were added simultaneously to the reactor as indicated in Examples 1-4.

This is the encapsulation of the phosphate forum, or a silicon aluminium oxynitride coating. The coating has an oxygen nitrogen ratio of around 1. The coating will be sufficiently non-porous to prevent shadowing of the particle when exposed to silver nitrate.

Prophetic Example 2 Phosphorus particles are placed in a reactor similar to that used in the previous examples.

The reactor containing the phosphor particles is maintained at a temperature in the range of about 300 ° C to about 500 ° C. The precursor gas streams of a dimethylamino aluminum and tris dimethylamino silane at flow ratios that provide equivalent flow per gram of phosphorus as Examples 7-11 are introduced into the reactor. Oxygen is also added to the reactor at a flow rate ^ equivalent to that of Example 12.

The phosphorus is encapsulated by a coating of silicon aluminum oxynitride. The coating will have a nitrogen to oxygen ratio of about 1. The coating will be sufficiently non-porous in order to prevent shadowing of the particle when silver nitrate is exposed.

Prophetic Example 3 Phosphorus particles are placed in a reactor similar to that used in the previous examples. The reactor containing the phosphor particles is maintained at a temperature in the range of about 300 ° C to about 600 ° C. It is directed to a simple precursor gas stream containing silicon, alkyl amino ligands, and oxygen ligands in the reactor at a sufficient flow rate to give a flow equivalent to those reported in Examples 7-11.

The resulting reaction encapsulates the phosphor particles with a coating of silicon oxynitride. The coating should stop a nitrogen-to-oxygen ratio of about 1. The coating should be sufficiently non-porous-or in order to prevent ü¡¡C "-the shadowing of the particle when exposed to silver nitrate.

For the above description of the general principles of the present invention and the foregoing detailed description, those skilled in the art will readily understand various modifications to which the present invention is susceptible. Therefore, the scope of the invention will be limited only by the following claims and equivalents thereof.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (27)

Claims Having described the invention as above, the content of the following claim is claimed as a property.

1. A plurality of encapsulated particles, each of the encapsulated particles characterized in that they compr a phosphorus particle of a luminescent elemental phosphorus material exhibiting a decay accelerated by moisture; and a substantially transparent substrate metallic oxynitride coating that sufficiently encapsulates the phosphor particle to provide the phosphor particle with reduced sensitivity to decay accelerated by moisture.

The encapsulated particles according to claim 1, characterized in that the metal oxynitride coating has a nitrogen to oxygen molar ratio in the range of about 4: 1 to about 1: 4.

The encapsulated particles according to claim 1, characterized in that the metal in the metal oxynitride is selected from the group of aluminum, boron, silicon, titanium, and zirconium or combinations thereof.

4. The encapsulated particles according to claim 1, characterized in that the coating is sufficiently non-porous to give the phosphor particle a substantial resistance to shadowing when the encapsulated particle is exposed to silver nitrate.

5. The encapsulated particles according to claim 1, characterized in that the metallic oxynitride coating has a thickness in the range of about 0.03 microns to about 1.0 microns.

6. The encapsulated particles according to claim 1, characterized in that each of the encapsulated particles includes a coating of metallic oxynitride having a plurality of layers of metallic oxynitride.

7. The encapsulated particles according to claim 1, characterized in that they comprat least one metal oxide coating applied to the metal oxynitride coating. tí ^ ttíí ^ ^ StL? atíSSSXl

8. The en.c & capsule particles according to claim 7, characterized in that the metal oxynitride coating and the metal oxide coating have a combined total thickness in the range of about 0.03 microns up to about 1.0 microns.

9. The encapsulated particles according to claim 1, characterized in that each of the encapsulated particles have an initial electroluminescent brightness that is equal to or greater than about 50% of the initial electroluminescent brightness of the phosphor particle without the coating.

The encapsulated particles according to claim 1, characterized in that each of the encapsulated phosphor particles compr phosphor particles made of at least one phosphorus compound selected from the group consisting of phosphorus based on zinc sulfide, phosphorus based in calcium sulphide, phosphorus based on zinc selenide, a phosphorus based on strontium sulfide and a combination of the same.

11. A method for encapsulating phosphor particles, characterized in that it compr: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; providing one or more precursors comprising a precursor containing metal in the vapor phase, a precursor containing nitrogen in the vapor phase, and a precursor containing oxygen in the vapor phase; and exposing the bed to the phosphorus particles for the precursors in such a way that the precursors react chemically and encapsulate the phosphor particles with a metallic oxynitride coating, wherein the metallic oxynitride coating encapsulates sufficiently to provide the phosphorus particle with a sensitivity reduced to moisture decay.

12. The method according to claim 11, characterized in that the precursors include two or more precursors containing metal in the vapor phase and the metal oxynitride coating comprises a mixed metal oxynitride coating.

The method according to claim 12, characterized in that the metal precursors in the vapor phase include metals selected from the group consisting of aluminum, boron, silicon, titanium, and zirconium or combinations thereof.

The method according to claim 11, characterized in that the chemical reaction of the precursors occurs at a temperature and conditions that substantially minimize the thermochemical related damage of the phosphor particles and retain a high initial luminescent brightness of the phosphor particles.

15. The method according to claim 11, further comprising exposing the bed of phosphorus particles to metal oxide precursors in the vapor phase to form a metal oxide coating on the metal oxynitride coating.

16. The method according to claim 11, characterized in that the nitrogen precursor in the vapor phase is ammonia.

The method according to claim 11, characterized in that one or more precursors include a vapor phase compound having a metal-nitrogen bond in addition to or in place of the vapor phase nitrogen precursor.

The method according to claim 17, characterized in that the compound has a metal-nitrogen bond including methyl amino complexes of aluminum, boron, silicon, titanium, or zirconium.

The method according to claim 11, characterized in that one or more precursors is a simple precursor that provides a metal, nitrogen and oxygen source for the metal oxynitride coating.

20. The method for encapsulating phosphorus particles, characterized in that it comprises: directing one or more precursors comprising a vapor-containing metal-containing precursor, a vapor-containing nitrogen-containing precursor, and a precursor containing oxygen in the vapor phase. vapor in a bed of phosphorus particles such that the precursors chemically react and encapsulate the phosphor particles and a metal oxynitride coating, wherein the metal oxynitride coating is sufficiently encapsulating to give the phosphor particle a reduced sensitivity to the phosphorus particle. decay due to humidity

21. A device, characterized in that it includes the electum roluminescent phosphor particles encapsulated according to claim 1.

22. A method for encapsulating phosphor particles, characterized in that it comprises: providing a bed of electroluminescent phosphor particles, each of which exhibits a decay accelerated by humidity; providing one or more precursors wherein at least one precursor has a metal-nitrogen bond; and exposing the bed of phosphorus particles to the precursors in such a way that the precursors chemically react and encapsulate the phosphor particles with a coating, wherein the coating encapsulates sufficiently providing the phosphor particles with a reduced sensitivity to decay accelerated by moisture .

23. A method according to claim 22, characterized in that the coating includes metal-nitrogen bonds.

24. A method according to claim 22, characterized in that the coating includes nitrogen, oxygen, and at least one metal.

25. The method according to claim 22, characterized in that at least one precursor with metal-nitrogen bond provides at least one simple source of metal and nitrogen for the coating.

The method according to claim 22, characterized in that at least one precursor with metal-nitrogen bond includes methyl to mo complexes of aluminum, boron, silicon, titanium, or zirconium.

27. A plurality of encapsulated particles, each of the encapsulated particles characterized in that it comprises: phosphorus particles of an electroluminescent phosphorus material exhibiting a decay accelerated by moisture; and a substantially transparent coating including nitrogen, oxygen, and at least one metal that sufficiently encapsulates the phosphor particle giving the phosphor particle a reduced sensitivity to decay accelerated by moisture.