JP2009067914A - Manufacturing method of phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of zinc sulfide of high purity homogeneously doped with a substantial amount of manganese by an industrially easy method. <P>SOLUTION: The manufacturing method of manganese-doped zinc sulfide comprises mixing a manganese salt, a zinc salt and a sulfurizing agent in an aqueous solvent, where the sulfurizing agent is a thioamide and/or thiourea and the aqueous solvent has a pH of at least 8.2. Preferably, pH is adjusted using an organic acid salt and an amine, pH is adjusted using an organic acid salt and ammonia, the organic acid salt is ammonium salt of an organic acid and a salt of a doping element other than the manganese salt is further incorporated in the mixing step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for preparing a phosphor containing manganese useful as a phosphor.

As a method for preparing a zinc sulfide phosphor containing manganese, a method of adding a salt containing manganese to zinc sulfide is generally performed. However, since the particle size cannot be controlled or the mixture is solid, Due to problems such as doubt in homogeneity at the time, the dope at the time of forming zinc sulfide has been studied from the viewpoint of making extremely small particles. Therefore, a method of preparing zinc sulfide doped with manganese by mixing a salt containing manganese and a salt containing zinc and mixing and reacting with an alkali metal sulfide such as sodium sulfide (see Non-Patent Document 1). In addition, a method of performing manganese doping using micelles in a liquid phase reaction (Non-patent Document 2) is disclosed. In addition, a method of using a sulfurizing agent that generates hydrogen sulfide by heating with thioacetamide or the like when doping ions such as copper is also disclosed (Non-Patent Document 3).
Material Letters Vol.58, 2004, 3661-3664 Material Letters 58 (2004) 3661-3664 Journal of Luminescence 99 2002 39-45 Journal of Luminescence 99 2002 39-45 Journal of Colloid and Interface Science, Vol. 257, No. 1, 2003, 47-55 Journal of Colloid and Interface Science, Volume 257, Issue 1, 1 January 2003, Pages 47-55

  However, in the method using an alkali metal sulfide such as Non-Patent Document 1, it is inevitable that an alkali metal compound is mixed in the obtained zinc sulfide, and the phosphor purity is low and sufficient fluorescence characteristics cannot be obtained. In the method using micelles such as Non-Patent Document 2, a large number of man-hours are required to remove the chemicals used for micelle formation, which is difficult to implement on an industrial scale. In the method using thioacetamide disclosed in Non-Patent Document 3 and the like, there are problems such as low pH, acidic conditions, high solubility of produced manganese sulfide, and failure to be taken into zinc sulfide.

  Accordingly, an object of the present invention is to provide a method for producing zinc sulfide having a high purity by uniformly doping a considerable amount of manganese with an industrially easy method.

  The present inventors have intensively studied and found that a considerable amount of manganese can be homogeneously doped by carrying out the reaction in an aqueous solution with adjusted pH, and have completed the present invention.

That is, the present invention provides the following.
[1] A method for producing manganese-doped zinc sulfide comprising mixing a manganese salt, a zinc salt and a sulfiding agent in an aqueous solvent, wherein the sulfiding agent is a thioamide and / or thiourea, A method for producing manganese-doped zinc sulfide, wherein the pH is 8.2 or more.

[2] The production method according to [1], wherein the pH is adjusted with an organic acid salt and an amine.
[3] The production method according to [1], wherein the pH is adjusted with an organic acid salt and ammonia.
[4] The production method according to [2] or [3], wherein the organic acid salt is an ammonium salt of an organic acid.

[5] The method according to any one of [1] to [4], wherein in the mixing step, a salt of a doping element other than a manganese salt is further mixed.
[6] Manganese-doped zinc sulfide produced by the method according to any one of [1] to [5].

[7] A method of using the manganese-doped zinc sulfide described in [6] as a phosphor.
[8] A method for producing a manganese-doped zinc sulfide phosphor having high quantum efficiency, comprising firing the manganese-doped zinc sulfide according to [6].

  [9] A manganese-doped zinc sulfide phosphor having a high quantum efficiency produced by the method of [8].

  According to the production method of the present invention, manganese-doped zinc sulfide can be produced with high productivity.

  Examples of the salt containing zinc used in the present invention include halides such as zinc chloride and zinc bromide, mineral salts such as zinc sulfate, zinc sulfite, zinc phosphate and zinc nitrate, or zinc formate, zinc acetate, Organic acid salts such as zinc oxalate can be used. These may be anhydrous salts or hydrated salts. These may be used alone or in combination. Nitrate is preferably used in consideration of reaction rate, counter ion persistence, and availability. The purity of the salt to be used is not particularly limited and is preferably as high as possible. However, it is particularly preferable to use a substance that does not contain metal impurities such as iron, nickel, cobalt, chromium, and tungsten. This is preferable.

  Manganese doped in the present invention is used simultaneously with the zinc salt. The salt of manganese to be used is not particularly limited, and halides such as manganese chloride and manganese bromide, mineral salts such as manganese sulfate, manganese sulfite, manganese phosphate and manganese nitrate, or manganese formate and acetic acid. Organic acid salts such as manganese and manganese oxalate, and complex salts such as manganese acetylacetonate can be used. These may be anhydrous salts or hydrated salts. These may be used alone or in combination. Nitrate is preferably used in consideration of reaction rate, counter ion persistence, and availability. The purity of the salt to be used is not particularly limited and is preferably as high as possible. However, it is particularly preferable to use a substance that does not contain metal impurities such as iron, nickel, cobalt, chromium, and tungsten. This is preferable.

  The amount of manganese in zinc sulfide is not particularly limited, but an excessive amount is not preferable because it decreases the fluorescence yield due to interaction between excitons, and an excessively small amount is an amount of fluorescence that can be extracted. Since it falls, it is not preferable. Therefore, it is preferable to contain in 50-50,000 ppm, Preferably it is 100-30,000 ppm, More preferably, it contains in the range of 300-10,000 ppm.

  In the present invention, zinc sulfide may contain doping elements other than manganese, for example, transition metals such as copper, silver, gold and iridium; indium; rare earth elements such as cerium, praseodymium and europium. These can also be added as a salt simultaneously with zinc. As salts that can be used, they can be added as mineral acid salts such as halogen salts and sulfates, and organic acid salts such as acetates. These can be used alone or in combination. It doesn't matter. The amount to be doped varies depending on the doping amount of manganese, but is usually 5 to 10,000 ppm, preferably 10 to 5,000 ppm, in the range of 20 to 3,000 ppm in consideration of the effect and efficiency of addition. Added.

  As the sulfurizing agent used in the present invention, thioamides such as thioformamide and thioacetamide, thiourea and the like can be used. The amount of these sulfiding agents used is usually in the range of 0.1 to 5 equivalents, 0.5 to 3 equivalents in view of the efficiency of production of sulfides and economics, relative to the zinc salt used. Preferably, 0.8 to 2 equivalents are used.

  The present invention is practiced in water. In order to use the obtained sulfide as a phosphor, it is preferable not to contain other than the required metal. Therefore, it is preferable to use ion-exchanged water as the water to be used. Heavy metals such as iron, nickel and cobalt are each 50 ppm or less, preferably 10 ppm or less, and typical metals such as sodium, potassium, calcium and magnesium are each 500 ppm or less. Preferably, the one with 100 ppm or less is used.

  The amount of water to be used is not particularly limited, and the concentration of zinc, when carrying out the reaction, ranges from 0.01 mol / liter to 3 mol / liter, more preferably 0.1 mol / liter. Adjust to a range of ~ 2 mol / liter.

  The present invention is carried out under basic conditions of pH = 8.2 or higher. Under acidic and neutral conditions, the resulting manganese sulfide is not preferable because it is highly soluble in water and not introduced into zinc sulfide. The pH under basic conditions is usually in the range of 8.2 to 11, and when the pH is too high, decomposition of thioacetamide, thiourea and the like is quick and sulfurization efficiency does not increase. It is in the range of ˜10.5, more preferably in the range of 9 to 10.2.

  In the present invention, the basicity in the reaction system is adjusted with an organic acid salt and an amine and / or ammonia. If only amine and / or ammonia is used, the zinc salt to be used is not dissolved, the efficiency of the reaction is low, and there is a possibility that it will be incorporated into the precipitated zinc sulfide. The acid constituting the organic acid salt to be used is not particularly limited as long as it shows water solubility, and it is possible to use monobasic acids such as formic acid, acetic acid and propionic acid, dibasic acids such as oxalic acid and the like. it can. The amine is not particularly limited as long as it shows water solubility, and methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine and the like can be used. In view of solubility and persistence in precipitated zinc sulfide, it is preferable to use ammonia. Therefore, the use of ammonium salts such as ammonium formate and ammonium acetate is preferable from the viewpoints of availability, effects, and economical efficiency for the basic adjustment.

  The amount of these used is not particularly limited, and may be an amount sufficient to dissolve the zinc salt and manganese salt to be used. Therefore, although it varies depending on the type of zinc salt to be used, it is usually 0.5 to 20 mole times, more preferably 0.6 to 10 mole times with respect to the zinc salt, and the used reagent is homogenized. To do.

  The working atmosphere of the present invention is not particularly limited and may be carried out in the atmosphere, but in view of safety and operability, it may be carried out in an inert gas atmosphere such as nitrogen or argon. preferable.

  In the liquid phase preparation of the present invention, the reaction temperature varies depending on the sulfiding agent used, but if the temperature is too low, the progress of the reaction is extremely slow and undesirable, and if it is too high, the concentration of hydrogen sulfide generated in the liquid will decrease. This is not preferable because the efficiency of the sulfiding agent is lowered. Usually, it is carried out in the range of 5 ° C to 120 ° C, more preferably 10 ° C to 100 ° C. The reaction method is not particularly limited, and either a batch method or a continuous method may be adopted.

  The sulfide obtained in the liquid phase preparation is repeatedly washed with ion-exchanged water while being separated from water by a method such as decantation or centrifugation, and washed until the pH of the washing layer becomes 6-8.

  The washed sulfide can be dried by removing water by a method such as vacuum drying or hot air drying at 150 ° C. or lower. Needless to say, the drying time depends on the amount of water contained, but is usually 1 hour to 50 hours and 1.5 hours to 20 hours in consideration of drying efficiency.

In the present invention, after drying, if necessary, the particles can be pulverized by a method such as crushing to obtain phosphor particles having a required size.
As described above, the manganese-doped zinc sulfide obtained by the method of the present invention can be used as a phosphor. However, it is possible to dramatically increase the quantum efficiency of the phosphor by further firing treatment. It is clear from their research. For example, as shown in the Examples described later, the manganese-doped zinc sulfide after firing has a quantum efficiency as high as 35% or more, particularly as high as 40% to 60%.

  The temperature at which the manganese-doped zinc sulfide obtained by the method of the present invention is calcined is not less than the temperature at which the crystal form of zinc sulfide changes and not more than the temperature at which sublimation occurs. That is, it is carried out at a temperature of 500 ° C. or higher and 1250 ° C. or lower, preferably 550 ° C. or higher and 1000 ° C. or lower, more preferably 600 ° C. or higher and 800 ° C. or lower.

  The rate of temperature rise up to the firing temperature is not particularly limited, but the temperature is usually raised at a rate of 2.0 ° C./min to 40.0 ° C./min. A temperature that is too early is not preferable because it damages the furnace body and the vessel containing zinc sulfide, and a rate that is too slow is not preferable because production efficiency is significantly reduced. From such a viewpoint, it is preferable to carry out at a rate of 2.5 ° C./min or more and 30.0 ° C./min or less.

In the present invention, the atmosphere in which the firing is performed is not particularly limited, and the firing may be performed in any gas atmosphere such as air, inert gas atmosphere, or reducing gas atmosphere.
In the present invention, a flux can be used to promote crystallization and increase the particle size during firing. Usable fluxes include alkali metal salts such as sodium chloride and potassium chloride, alkaline earth salts such as magnesium chloride, calcium chloride and magnesium chloride, ammonium chloride and zinc chloride. These fluxes may be used alone or in combination. The amount to be used is not particularly limited, and it may be 0.1 to 50% by weight, 0.5 to 10% by weight in consideration of operability and economy with respect to zinc sulfide. preferable.

  In the present invention, sulfur alone can be added to supplement sulfur missing during firing. The amount to be added is not particularly limited, and is usually 0.1 to 300 parts by weight, more preferably 1 to 200 parts by weight with respect to 100 parts by weight of zinc sulfide.

  In the present invention, the fired product is washed after the firing. The excess flux added is removed by washing. For washing, neutral water or acidic water can be used. The acid content is not particularly limited, and mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and organic acids such as acetic acid, propionic acid and butyric acid can be used. These can be used alone or in combination. Since zinc sulfide may decompose when it comes into contact with high-concentration acidic substances, it is usually preferable to use an aqueous solution of 0.1 to 20% by weight, more preferably 1 to 10% by weight when using acidic water. % Aqueous solution is used. Furthermore, it is preferable to use acetic acid in consideration of decomposition of zinc sulfide and ion residual property on the surface.

In the present invention, after firing, the washed zinc sulfide can be dried by a method such as vacuum or hot air to obtain a desired phosphor.
The formation of the phosphor can be confirmed by measuring the quantum efficiency. Quantum efficiency is the ratio between the number of photons emitted by excitation by incident light and the number of photons of incident light absorbed by the material, and the larger this value, the higher the doping effect. Quantum efficiency can be measured with a spectrofluorometer.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but it goes without saying that the present invention is not limited to the following examples.
In addition, the measurement conditions of the spectrofluorometer for quantum efficiency measurement were as follows.
Measuring device: FP-6500 manufactured by JASCO Corporation
Excitation wavelength: 350 nm
Excitation bandwidth: 5 nm
Software: Spectra Manager for Windows (registered trademark) 95 / NT Ver1.00.00 2005 manufactured by JASCO Corporation

Example 1
Into a 3 L separable flask equipped with a stirrer, a condenser, and a thermometer, 446.2 g of zinc nitrate hexahydrate, 770.8 g of ammonium acetate, and 3.82 g of manganese nitrate (corresponding to Mn 5000 ppm) were taken, and 25% aqueous ammonia 433 was added. .5 g was added and dissolved. Ion exchange water was added thereto and diluted to 1.5 L (pH = 10 at this time) to obtain a uniform solution. After the inside of the system was replaced with nitrogen, the temperature was raised, and when the internal temperature reached 75 ° C., 169.0 g of thioacetamide was added. The mixture was stirred for 2.5 hours while maintaining the internal temperature at 75 ° C. After a predetermined time, the mixture was cooled to room temperature, the upper layer was removed by decantation, and washed with ion-exchanged water. Washing was repeated until the pH of the aqueous phase became 8 or less, water was separated with a centrifugal separator, and heat-dried with a hot air dryer at 150 ° C. for 12 hours to obtain 142 g of manganese-doped zinc sulfide. When analyzed by ICP emission analysis, the doping amount of manganese was 4800 ppm, and metals other than manganese and zinc were not detected. The obtained manganese-doped zinc sulfide can be used as a phosphor as it is, its emission wavelength was 580 nm, and the quantum efficiency was 4.7%.

  30 g of the manganese-doped zinc sulfide obtained above and 5 g of sulfur were pulverized and mixed in a mortar, and it was confirmed that the sulfur particles were particularly dispersed so that they could not be identified. The mixture was fired at 1000 ° C. The obtained fired product had an emission wavelength of 581 nm and a quantum efficiency of 41.3%.

Example 2
The same procedure as in Example 1 was carried out except that 171.2 g of thiourea was used instead of 169.0 g of thioacetamide, to obtain 138.5 g of manganese-doped zinc sulfide.
The manganese doping amount was 4900 ppm, and metals other than manganese and zinc were not detected. The obtained manganese-doped zinc sulfide can be used as a phosphor as it is, its emission wavelength was 586 nm, and the quantum efficiency was 5.1%.

  30 g of the manganese-doped zinc sulfide obtained above and 5 g of sulfur were pulverized and mixed in a mortar, and it was confirmed that the sulfur particles were particularly dispersed so that they could not be identified. The mixture was fired at 1000 ° C. The fired product obtained had an emission wavelength of 582 nm and a quantum efficiency of 44.1%.

Example 3
The reaction was conducted in the same manner as in Example 1 except that 99.9 mg of diammonium hexachloroiridate was added to obtain 141.5 g of manganese / iridium doped zinc sulfide. The manganese doping amount was 4800 ppm and the iridium doping amount was 196 ppm. The obtained manganese / iridium doped zinc sulfide can be used as a phosphor as it is, and its emission wavelength was 590 nm and the quantum efficiency was 5.3%.

  30 g of the manganese / iridium-doped zinc sulfide obtained above and 5 g of sulfur were pulverized and mixed in a mortar, and it was confirmed that the sulfur particles were particularly dispersed so that they could not be identified. The mixture was fired at 1000 ° C. The fired product obtained had an emission wavelength of 588 nm and a quantum efficiency of 50.3%.

Example 4
Except for adding 0.452 g of indium nitrate trihydrate, the same procedure as in Example 1 was carried out to obtain 142.3 g of manganese / indium doped zinc sulfide. The manganese doping amount was 4800 ppm and the indium doping amount was 860 ppm. The obtained manganese / indium doped zinc sulfide can be used as a phosphor as it is, the emission wavelength was 586 nm, and the quantum efficiency was 7.4%.

  30 g of the manganese / indium-doped zinc sulfide obtained above and 5 g of sulfur were pulverized and mixed in a mortar, and it was confirmed that the sulfur particles were particularly dispersed so that they could not be identified. The mixture was fired at 1000 ° C. The obtained fired product had an emission wavelength of 586 nm and a quantum efficiency of 53.3%.

Example 5
The same procedure as in Example 1 was carried out except that the amount of 25% aqueous ammonia was 314.8 g and the pH was 8.6, to obtain 140.2 g of manganese-doped zinc sulfide. The doping amount of manganese was 4710 ppm. The obtained manganese-doped zinc sulfide can be used as a phosphor as it is, its emission wavelength was 582 nm, and the quantum efficiency was 5.2%.

  30 g of the manganese-doped zinc sulfide obtained above and 5 g of sulfur were pulverized and mixed in a mortar, and it was confirmed that the sulfur particles were particularly dispersed so that they could not be identified. The mixture was fired at 1000 ° C. The obtained fired product had an emission wavelength of 582 nm and a quantum efficiency of 40.4%.

Comparative Example 1
It replaced with thioacetamide and carried out similarly to Example 1 except having added 504.7g of sodium sulfide pentahydrate, and obtained 144.7g of manganese dope zinc sulfide. The doping amount of manganese was 4120 ppm, the doping amount of sodium was 2100 ppm, and a large amount of sodium was contained as an impurity. Sodium is unfavorable because it significantly corrodes carbon and alumina molds during heat molding.

Comparative Example 2
In a 3 L separable flask equipped with a stirrer, a condenser, and a thermometer, 223.2 g of zinc nitrate hexahydrate and 1.91 g of manganese nitrate (equivalent to Mn 5000 ppm) were taken, and 750 g of ion-exchanged water was added and dissolved. Thereto was added 1.5 g of nitric acid (pH = 2) to obtain a uniform solution. After the inside of the system was replaced with nitrogen, the temperature was raised, and when the internal temperature reached 75 ° C., 84.5 g of thioacetamide was added. The mixture was stirred for 2.5 hours while maintaining the internal temperature at 75 ° C. After a predetermined time, the mixture was cooled to room temperature, the upper layer was removed by decantation, and washed with ion-exchanged water. Washing was repeated until the pH of the aqueous phase was 8 or less, water was separated with a centrifuge, and heat-dried with a hot air dryer at 150 ° C. for 12 hours to obtain 67 g of zinc sulfide. When analyzed by ICP emission analysis, the doping amount of manganese in zinc sulfide was 0 ppm.

Comparative Example 3
The same procedure as in Example 1 was carried out except that the amount of 25% aqueous ammonia was 112.5 g, and the pH of the solution was 7.8, to obtain 140.4 g of manganese-doped zinc sulfide. The doping amount of manganese was 211 ppm.

Comparative Example 4
The same operation as in Example 1 was performed except that 25% aqueous ammonia was not used. The pH of the solution was 6.5, and 140.1 g of zinc sulfide was obtained, but the doping amount of manganese was 0 ppm.

  As is clear from the above Examples and Comparative Examples, when the pH of the solution during preparation of manganese-doped zinc sulfide is neutral to acidic, manganese sulfide is hydrolyzed and it is difficult to dope manganese sulfide to zinc sulfide. It can be seen that it is. As described above, according to the method of the present invention, the manganese source can be uniformly dispersed in the solution, and manganese can be doped into the zinc sulfide in the dispersed state. Therefore, the manganese is uniformly doped into the zinc sulfide economically and efficiently. It is extremely useful in industry.

  In addition, the quantum efficiency of the phosphor is preferably 20% or more. However, the phosphors having high quantum efficiency obtained by the method of the present invention have a quantum efficiency far exceeding 20%. Indicated by example results.

Claims (9)

  A method for producing manganese-doped zinc sulfide comprising mixing a manganese salt, a zinc salt and a sulfurizing agent in an aqueous solvent, wherein the sulfurizing agent is a thioamide and / or thiourea, and the pH of the aqueous solvent is 8 A method for producing manganese-doped zinc sulfide, which is 2 or more.   The production method according to claim 1, wherein the pH is adjusted with an organic acid salt and an amine.   The production method according to claim 1, wherein the pH adjustment is performed with an organic acid salt and ammonia.   The production method according to claim 2 or 3, wherein the organic acid salt is an ammonium salt of an organic acid.   The manufacturing method according to any one of claims 1 to 4, wherein a salt of a doping element other than a manganese salt is further mixed in the mixing step.   Manganese-doped zinc sulfide produced by the method according to any one of claims 1 to 5.   A method of using the manganese-doped zinc sulfide according to claim 6 as a phosphor.   A method for producing a manganese-doped zinc sulfide phosphor having high quantum efficiency, comprising firing the manganese-doped zinc sulfide according to claim 6.   A manganese-doped zinc sulfide phosphor having a high quantum efficiency produced by the method of claim 8.