JP5547493B2 - Method for producing iridium-containing phosphor - Google Patents

Description

  The present invention relates to a method for producing a phosphor containing iridium.

  Inorganic compositions mainly composed of compound semiconductors are used in the fields of light emitting materials such as fluorescence and phosphorescence, and phosphorescent materials. Some of these have the property of emitting light by electrical energy, are used as light sources, and are partially used for applications such as display. However, currently known materials have insufficient light conversion efficiency of electric energy, and thus have problems such as heat generation and power consumption, and are limited in application. In particular, the blue phosphor is useful as a white light emitting material as well as a single color.

  In a phosphor mainly composed of a II-VI group compound semiconductor, a blue phosphor that is doped with copper (for example, see Non-Patent Document 1) or a substance that is doped with thulium (Tm) (for example, Non-Patent Document) 2) is known. Moreover, what prepared the II-VI group compound semiconductor under hydrothermal conditions etc. (for example, refer patent document 1) and also used what used praseodymium as a dopant (refer nonpatent literature 3) are known.

  However, the above-mentioned patent documents and non-patent documents disclose a method of doping the emission center in order to bring about various emission colors, but the obtained blue fluorescent material has low energy efficiency and color purity. However, it is difficult to use for light sources and displays, or requires a large amount of expensive rare earth salts, and is not economically suitable.

  On the other hand, in order to further improve the light emission luminance, a method for producing a phosphor doped with iridium has also been proposed (see, for example, Patent Document 2 and Patent Document 3).

However, Patent Document 2 and Patent Document 3 describe a method for adjusting a phosphor using iridium, but there is no special description regarding the iridium compound, and more about the influence of impurities in the iridium compound. There is no description or suggestion.
JP-A-2005-36214 JP 2006-143947 A WO2007 / 043676 A1 Journal of Luminescence 99 (2002) 325-334 Journal Non-Crystalline Solids 352 (2006) 1628-1632 Japanese Journal of Applied Physics Vol44 No.10,2005, p 7694-7697

  Therefore, the problem to be solved is to provide a method for producing a phosphor that has high energy efficiency and high color purity, can be used for light sources and displays, and is economically advantageous.

  As a result of intensive studies, the present inventors have reduced the iron content in an iridium complex salt to 100 ppm or less in a method for producing an iridium-containing phosphor including a step of doping iridium into a II-VI compound semiconductor. The present inventors have found that the above problems can be solved, and have completed the present invention. The present invention provides the following.

  [1] A method for producing an iridium-containing phosphor including a step of doping iridium into a II-VI group compound semiconductor, wherein an iridium complex salt having an impurity iron content of 100 ppm or less is used in the step of doping iridium A method characterized by:

  [2] The method according to [1], which is an iridium complex salt having an impurity iron content of 50 ppm or less.

  [3] The method according to [1], which is an iridium complex salt having an impurity iron content of 10 ppm or less.

  [4] The method according to [1], wherein the iridium complex salt is a hexachloroiridium salt.

It is a fluorescence spectrum of the phosphor obtained in Example 1 (emission peak wavelength: 462 nm). It is a fluorescence spectrum of the phosphor obtained in Example 2 (emission peak wavelength: 464 nm). It is a fluorescence spectrum of the phosphor obtained in Comparative Example 1 (emission peak wavelength: 548 nm).

  The following is a detailed description of the present invention.

  The II-VI group compound semiconductor used as a raw material in the present invention is not particularly limited, and any material such as zinc sulfide, cadmium sulfide, zinc selenide, cadmium selenide may be used. These may be used alone or in combination. The crystal structure constituting the II-VI group compound semiconductor is not particularly limited, and may be a hexagonal crystal, a cubic single body, or a hybrid thereof.

  In the present invention, a complex salt of iridium having an impurity iron content of 100 ppm or less, preferably 50 ppm or less, more preferably 10 ppm or less is used as the iridium compound. Although all commercially available iridium complex salts contain 300 ppm or more of iron as impurities, the present inventors prepared phosphors using iridium complex salts in which the concentration of these irons was reduced to 100 ppm or less. It has been found that an unexpectedly greatly improved phosphor can be obtained.

  The method for reducing the content of iron, which is an impurity from the iridium complex salt, is not particularly limited, and general methods such as washing and recrystallization can be used, but the iron content is around 100 ppm or In order to reduce it to less than that, it is preferable to use recrystallization from the viewpoint of iron compound removal efficiency. By reducing the iron content in the iridium complex salt to 100 ppm or less, the light emission characteristics of the phosphor are improved. When the content is reduced to 50 ppm or less, the light emission characteristics are further improved, and when it is reduced to 10 ppm or less, the light emission characteristics are obtained. Will improve dramatically. As the solvent for recrystallization, water, alcohols such as methanol and ethanol, and organic solvents such as acetone, dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide can be used. From the viewpoint of residues and the like, it is preferable to use water and methanol. By repeating the recrystallization, the iron content can be reduced to the target concentration of iron impurities.

  When commonly available iridium salts such as iridium halide salts such as iridium chloride are used, they are difficult to dissolve in solvents such as water and alcohol, and in addition to using a large amount of water, they are extremely agglomerated. Since it is easy, an iridium salt cannot be uniformly dispersed in a II-VI group compound semiconductor. For this reason, the iridium salt aggregates during heating and baking, and is thermally reduced by heating and difficult to introduce into the II-VI group compound semiconductor. In the present invention, since the iridium complex salt is used, the above-described disadvantages are not caused, and the iridium salt can be uniformly dispersed in the II-VI group compound semiconductor.

  The complex salt of iridium used is not limited, and the valence of iridium is not particularly limited, and trivalent or tetravalent ones can be used. For example, ammonium hexachloroiridium (III), sodium hexachloroiridium (III), potassium hexachloroiridium (III), ammonium hexachloroiridium (IV), diammonium hexachloroiridium (IV), sodium hexachloroiridium (IV) , Potassium hexachloroiridium (IV), hydrogen hexachloroiridium (IV), ammonium hexabromoiridium (III), sodium hexabromoiridium (III), potassium hexabromoiridium (III), hexabromoiridium (IV) Ammonium acid, sodium hexabromoiridium (IV), potassium hexabromoiridium (IV), hydrogen hexabromoiridium (IV), ammonium hexaiodoiridium (III), sodium hexaiodoiridium (III) Potassium hexaiodoiridium (III), ammonium hexaiodoiridium (IV), sodium hexaiodoiridium (IV), potassium hexaiodoiridium (IV), hydrogen hexaiodoiridium (IV), hexaammineiridium (III ) Chloride, potassium hexacyanoiridium (III), pentaamminechloroiridium (III) chloride, and the like. These ammonium salts are preferably used in consideration of availability, safety, and the fact that metal impurities do not remain in the resulting iridium sulfide. That is, it is preferable to use hexachloroiridium salts such as ammonium hexachloroiridium (III), ammonium hexachloroiridium (IV), and diammonium hexachloroiridium (IV).

  The method for introducing these iridium is not particularly limited, and generally, a method of solid mixing with a II-VI group compound semiconductor and heating and firing, or a II-VI group compound semiconductor dispersed in water. Adding an iridium complex salt powder or an iridium complex salt dissolved in water, evaporating water while stirring to obtain an inorganic composition, and heating and firing the inorganic composition; For example, a method in which an iridium complex salt is produced in the coexistence and the obtained composition is heated and fired is used. In order to suppress aggregation of the iridium complex salt and fix it on the II-VI group compound semiconductor, it is preferable to use a method of fixing the iridium complex salt in a dissolved state.

  The amount of water used for fixing is not particularly limited, but usually considering the dispersibility, the slurry concentration of the II-VI group compound semiconductor is 0.1 to 50% by weight, more preferably The fixing is preferably performed in the range of 1 to 30% by weight.

  The method for removing water from the slurry is not particularly limited, but using a method such as decantation is not preferable because iridium complex salt dissolved in the solution is lost. Usually, a method is used in which water is distilled off from the slurry by decompression or heating.

  According to the present invention, the amount of iridium introduced into the II-VI group compound semiconductor is not particularly limited, but too much introduction is not economical with respect to the amount introduced, and concentration quenching is not possible. Concentrations that are too low are undesirable because they do not have enough emission centers to elicit high fluorescence efficiency. Therefore, it is usually preferable to introduce the phosphor in the range of 5 to 5000 ppm, more preferably in the range of 10 to 1000 ppm.

  In the present invention, in order to introduce iridium into the II-VI group compound semiconductor, a method of heating and baking can be used. The firing temperature is not less than the temperature at which the crystal form of the II-VI compound semiconductor 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. Too early temperature is not preferable because it damages the furnace body and the container containing the II-VI group compound semiconductor, and excessively low speed is not preferable because production efficiency is remarkably lowered. From such a viewpoint, it is preferable to carry out at a rate of 2.5 ° C./min to 30.0 ° C./min.

  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 is 0.5 to 10 parts by weight with respect to 100 parts by weight of the II-VI group compound semiconductor in consideration of operability and economy. It is preferred to use parts by weight.

  In the present invention, other elements can be doped at the same time. The method of doping at the same time is not particularly limited, and can be doped by dissolving in water at the same time as the iridium complex salt, followed by baking, and after mixing the iridium complex salt, the salt is mixed into the solid. It is also possible to dope by baking. As the element to be doped, transition metals such as silver, copper and manganese, rare earth elements such as cerium and europium, and gallium can also be doped. These can be mixed as halides such as chloride, bromide, mineral acid salts such as sulfuric acid, phosphoric acid and nitric acid, organic acid salts such as acetic acid and propionic acid, and can be used alone or in combination It doesn't matter.

  According to the present invention, the amount of other elements introduced into the II-VI compound semiconductor is not particularly limited, but too much introduction is not economical with respect to the amount introduced, and the concentration A concentration that is not preferable because it causes quenching, and a concentration that is too low is not preferable because it does not have a sufficient emission center to extract high fluorescence efficiency. Therefore, it is usually preferable to introduce the phosphor in the range of 5 to 5000 ppm, more preferably in the range of 10 to 1000 ppm.

  In the present invention, the group VI element alone can be added to compensate for the group VI element missing during firing. For example, sulfur can be added to supplement the sulfur content. The amount to be added is not particularly limited, and is usually in the range of 0.1 to 300 parts by weight, more preferably 1 to 200 parts by weight with respect to 100 parts by weight of the II-VI group compound semiconductor. Add in.

  In the present invention, the fired product is washed after the firing. By washing, the iridium salt which has not been introduced and the added extra flux are removed. 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 the II-VI compound semiconductor may be decomposed when it comes into contact with a high concentration acidic substance, it is usually preferable to use an aqueous solution of 0.1 to 20% by weight, more preferably, when using acidic water. A 1-10% by weight aqueous solution is used. Furthermore, the use of acetic acid is preferred in consideration of the decomposition of the II-VI group compound semiconductor and the ionic residue on the surface.

  In the present invention, after applying firing or impact, the cleaned II-VI group compound semiconductor 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, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Reference example 1:
2.1 g of diammonium hexachloroiridium (IV) containing 300 ppm of iron was dissolved in 32 g of ion-exchanged water at 45 ° C. The insoluble material was filtered through a 0.2 micron membrane filter, and the aqueous diammonium hexachloroiridium (IV) acid solution was cooled to 5 ° C. The precipitated diammonium hexachloroiridium (IV) acid was filtered off and vacuum dried to obtain 1.4 g of diammonium hexachloroiridium (IV) acid containing 100 ppm of iron. By repeating this operation, diammonium hexachloroiridium (IV) acid having a reduced iron content was obtained. Table 1 shows the iron content and the amount recovered. In addition, Table 2 shows the results of examining the iron content and the recovered amount by changing the amount of water used for recrystallization.

Reference example 2:
Instead of diammonium hexachloroiridium (IV) used in Reference Example 1, diammonium hexachloroiridium (III) containing 366 ppm of iron was used for recrystallization in the same manner as in Reference Example 1, and recrystallization was used. Table 3 shows the results of looking at the amount of water, the amount recovered, and the iron content.

Example 1
A 2 L three-necked flask is equipped with a stirrer, a reflux tube, and a thermometer. Zinc nitrate hexahydrate 223.2 g, copper (II) nitrate trihydrate 90.9 mg, gallium nitrate hexahydrate 2.73 mg Then, 0.078 g of diammonium hexachloroiridium (IV) obtained by recrystallization as in Reference Example 1 (iron content 100 ppm) and 84.5 g of thioacetamide were added and dissolved by adding 750 mL of ion-exchanged water. did. After adding 1.5 g of nitric acid, the inside of the system was replaced with nitrogen, heated to 90 ° C. in an oil bath, and heated. After completion of the temperature increase, the mixture was stirred for 2 hours. The obtained crystals were separated by filtration, washed with ion-exchanged water until the pH became 6, and dried to obtain 63.9 g of solid particles.

  63.9 g of solid particles were placed in a crucible and calcined at 800 ° C. for 4 hours under a nitrogen atmosphere. After calcination, the solid particles were washed with 600 g of a 1% by weight aqueous sodium cyanide solution and further washed with ion-exchanged water until the pH reached 6. Cyan was below the detection limit. The solid particles were dried at 150 ° C. for 15 hours to obtain 60.1 g of a phosphor.

  ICP emission analysis of the obtained phosphor revealed that it contained 564 ppm of Cu, 71.2 ppm of Ga, and 55.9 ppm of Ir.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. FIG. 1 shows the fluorescence spectrum, and Table 4 shows the quantum efficiency.

  To 1.5 g of the obtained phosphor, 1.0 g of a fluorine-based binder (DuPont 7155) was added as a binder, mixed and degassed to prepare a light emitting layer paste. Using a 20 mm square screen plate (200 mesh, 25 μm) on the PET film with ITO, the light emitting layer paste was made into a plate with a film thickness of 40 μm and dried at 100 ° C. for 10 minutes to form a light emitting layer. Further, barium titanate paste (7153 manufactured by DuPont) was made on the upper surface of the light emitting layer using a screen plate (150 mesh, 25 μm), dried at 100 ° C. for 10 minutes, then re-engraved, dried at 100 ° C. for 10 minutes, and 20 μm. A dielectric layer was formed. On the upper surface, a silver paste (461SS made by Acheson) was made as a plate using a screen plate (150 mesh, 25 μm) and dried at 100 ° C. for 10 minutes to form an electrode, thereby constituting a printing EL device. About the obtained element, EL material evaluation was performed by measuring light emission luminance at 200 V and 1 kHz. The results are shown in Table 4.

Example 2
In Example 1, it carried out like Example 1 except having used 0.078g of hexachloro iridium (IV) acid diammonium with an iron content of 10 ppm obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. FIG. 2 shows the fluorescence spectrum, and Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Example 3
In Example 1, it carried out like Example 1 except having used 0.078g of hexachloro iridium (IV) acid diammonium with an iron content of 78 ppm obtained by implementing recrystallization like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The fluorescence spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Example 4
In Example 1, it carried out like Example 1 except having used 0.078 g of hexaammonium iridium (IV) acid diammonium with an iron content of 46 ppm obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The fluorescence spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Example 5
In Example 1, it carried out like Example 1 except having used 0.078 g of 2 ammonium iron hexachloro iridium (IV) acids obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The fluorescence spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Example 6
In Example 1, it carried out like Example 1 except having used 0.080 g of 3 ammonium hexachloro iridium (III) acid of 4 ppm iron obtained by recrystallizing like the reference example 2. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The fluorescence spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Example 7
In Example 1, it carried out like Example 1 except having used 0.080 g of triammonium hexachloro iridium (III) of 12 ppm iron obtained by implementing recrystallization like the reference example 2. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The fluorescence spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Comparative Example 1
In Example 1, it carried out similarly to Example 1 except having used 0.078 g of hexachloro iridium (IV) acid diammonium containing 300 ppm of iron.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. FIG. 3 shows the fluorescence spectrum, and Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Comparative Example 2
In Example 1, it carried out like Example 1 except having used 0.078g of hexachloro iridium (IV) acid diammonium with an iron content of 120 ppm obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The emission spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Comparative Example 3
In Example 1, it carried out like Example 1 except having used 0.078g of hexachloro iridium (IV) acid diammonium with an iron content of 180 ppm obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The emission spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

Comparative Example 4
In Example 1, it carried out like Example 1 except having used 0.078g of hexachloro iridium (IV) acid diammonium with an iron content of 103 ppm obtained by recrystallizing like the reference example 1. FIG.

  The photoexcitation spectrum and quantum efficiency of the phosphor were measured by ultraviolet irradiation. The emission spectrum was the same as in FIG. Table 4 shows the quantum efficiency. Further, using the obtained phosphor, a printing type EL element was produced in the same manner as in Example 1, and the EL material was evaluated. The evaluation results are shown in Table 4.

The measurement conditions of the spectrofluorometer 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

  If the quantum efficiency of the phosphor is 30% or more, it is practical, but all of the phosphors obtained by the method of the present invention have a high quantum efficiency of approximately 40% or more, and thus have excellent emission characteristics. Useful as a phosphor. In fact, it has been found that when an EL device is manufactured using the phosphor obtained by the method of the present invention, the light emission luminance of the EL device is remarkably improved.

Claims (4)

A method for producing an iridium-containing phosphor including a step of doping iridium into a II-VI group compound semiconductor, wherein an iridium complex salt having an impurity iron content of 100 ppm or less is used in the step of doping iridium ,
Disperse II-VI compound semiconductor in water, add iridium complex salt powder or iridium complex salt dissolved in water, evaporate water while stirring to obtain an inorganic composition, and heat-fire the inorganic composition A method characterized by. 2. The method according to claim 1, wherein the iridium complex salt has an impurity iron content of 50 ppm or less. The method according to claim 1, wherein the iridium complex salt has an impurity iron content of 10 ppm or less. The process according to claim 1, wherein the iridium complex salt is a hexachloroiridium salt.

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