JP2009149765A - Manufacturing method for phosphor fine particle, phosphor fine particle, and electroluminescence display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a phosphor fine particle capable of simplifying a manufacturing process and having high brightness. <P>SOLUTION: This manufacturing method for the phosphor fine particle includes a process for forming a gas mixture containing a parent body material and an activator, by passing powder of the parent body material such as zinc sulfide serving as a parent body of a phosphor and the activator such as copper sulfide containing an element serving as a light emitting center of the phosphor under a thermal plasma, and for flocculating atoms in the gas mixture, by cooling the gas mixture. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for producing phosphor fine particles, a phosphor fine particle, and an electroluminescence display device. More specifically, the present invention relates to a method for producing phosphor fine particles suitable for an inorganic electroluminescent element, a phosphor fine particle, and an electroluminescence display device including the phosphor fine particle.

The need for flat panel displays has increased with the advancement of information technology in recent years, and display devices using electroluminescence (EL) elements are attracting much attention as candidates for next-generation flat panel displays. The EL element is roughly classified into an organic EL element using an organic material for a light emitting layer and the like, and an inorganic EL element using an inorganic material such as zinc sulfide (ZnS) as a base material of a phosphor. Research and development has been actively conducted on organic EL elements because a self-luminous and ultra-thin display device can be manufactured.

Inorganic EL elements are resistant to external factors such as moisture and temperature, and have been used for backlights used in display elements of mobile phones. In this inorganic EL element, for example, dispersed phosphor particles are dispersed in a dielectric material, and light is emitted by applying a voltage between electrodes disposed on both sides of the dispersed phosphor.

As a phosphor used in the inorganic EL element, for example, a general formula in which zinc sulfide (ZnS) is used as a base and copper (Cu), manganese (Mn) or the like is introduced as an activator is ZnS: Cu, ZnS: Mn, or the like. Is widely used. The emission color of the phosphor depends on the type of additive in ZnS. For example, blue light emission is obtained when Cu is added, and yellow-orange light emission is obtained when Mn is added. As a method for producing such phosphor fine particles, a solid phase method is generally used in which a base material powder and an activator material powder are mixed, filled in a crucible such as quartz, and fired. (For example, refer to Patent Documents 1 and 2).

By the way, as a method of manufacturing a phosphor using zinc sulfide as a base material by using a solid phase method, a mixture obtained by adding a copper compound and a halogen compound to zinc sulfide is used for the first time for a long time at a relatively high temperature. A process for producing a powdery intermediate phosphor comprising hexagonal crystals by firing, a process for generating distortion by applying an impact force to the intermediate phosphor, and a defect in the crystal, and an intermediate fluorescence in which a crystal defect has occurred And a process of mixing a cubic crystal by a second firing in a short time at a relatively low temperature (for example, see Patent Document 3). Further, in a method for producing a phosphor having gallium arsenide GaAs by reacting activated zinc sulfide ZnS: Cu, Cl, and phosphor with heating in the presence of Mn, the stirred and mixed product is placed in a crucible, A method is disclosed in which a crucible is fired at a temperature of about 650 ° C. for about 3 hours in a nitrogen stream containing about 10% medium sulfur gas to induce a transition to a hexagonal system (see, for example, Patent Document 4).

In addition to the solid phase method, a method using a thermal plasma method, which is one of the vapor phase methods, is disclosed as a method for producing fine particles (see, for example, Patent Document 5). In Patent Document 5, a powder raw material is put in a solvent to form a slurry, the slurry is made into droplets, the slurry made into droplets is introduced into thermal plasma, and the slurry is evaporated to form a gas phase mixture. Fine particles are produced by quenching the vaporized mixture in the vapor phase.
JP 2002-155275 A JP 2004-244479 A Japanese Patent Laid-Open No. 5-152073 JP 2005-336275 A JP-A-2005-170760

However, in Patent Documents 1 and 2, since the phosphor is generated using the solid-phase method, a long-time firing is required to uniformly distribute the added activator in the phosphor fine particles. There was room for improvement from the viewpoint of productivity. In addition, in the production of phosphor fine particles using the solid phase method, it is difficult to reduce the particle size of the phosphor, which is one of the factors that hinder the improvement of the light emission efficiency of display devices using the phosphor fine particles. It was.

In Patent Documents 3 and 4, an attempt is made to produce a phosphor using cubic zinc sulfide as a host material of the phosphor, but two firing steps are required using a solid phase method. Therefore, there was room for improvement from the viewpoint of productivity.

Furthermore, in Patent Document 5, in the method for producing fine particles, since raw material powder is put into a thermal plasma apparatus as a slurry, there is room for improvement in that the number of production steps increases. In addition, when charged as a slurry, the dispersion in which the raw material powder is dispersed may remain in the thermal plasma apparatus and impurities may be mixed into the fine particles.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a method for producing phosphor fine particles having a high luminance by simplifying the production process.

The inventors of the present invention have simplified the manufacturing process and have studied various methods for manufacturing high-luminance phosphor particles, and have focused on the fact that conventional phosphors are formed using a solid phase method. Then, the manufacturing method allows the matrix material powder and the activator powder containing the element serving as the emission center of the phosphor to pass through the thermal plasma through the thermal plasma so that the matrix material and Since the mixed gas containing the activator is then cooled by exiting the thermal plasma from the thermal plasma, molecules in the mixed gas can be aggregated to produce phosphor fine particles. It was found that nano-sized and high-luminance phosphor particles can be obtained. In addition, when zinc sulfide is used as a base material, it has been found that phosphor particles with higher luminance can be obtained by controlling the cooling temperature, and the above problem can be solved brilliantly. The present invention has been achieved.

That is, the present invention is a method for producing phosphor fine particles, wherein the production method includes a powder of a host material that is a host of the phosphor and a powder of an activator that includes an element that is a light emission center of the phosphor. It is a manufacturing method of fluorescent fine particles including a step of passing through thermal plasma.
The present invention is described in detail below.

The present invention is to produce phosphor fine particles. A phosphor is a substance that absorbs energy such as an electron beam, X-rays, ultraviolet rays, and an electric field, and emits (emits) a part of the absorbed energy as light. Is replaced with an element that becomes a luminescent center (constituent element of the activator), and light is generated by the element that constitutes the activator by the energy absorbed by the base material. The phosphor fine particles are fine particles containing a phosphor. The fine particles refer to fine particles having a diameter of about several nanometers to about 100 μm.

The method for producing phosphor fine particles includes a step of passing through a thermal plasma through a powder of a base material that is a matrix of the phosphor and a powder of an activator that contains an element that is an emission center of the phosphor. According to this, the matrix material powder serving as the phosphor matrix and the activator powder containing the element serving as the emission center of the phosphor are introduced into the thermal plasma, so that the matrix material and the activator are obtained. The mixed gas can be contained and cooled as it leaves the thermal plasma. Therefore, the mixed gas is rapidly cooled by exiting from the thermal plasma, and atoms in the mixed gas are aggregated to produce phosphor fine particles. By agglomerating the atoms decomposed to the atomic level in the thermal plasma, for example, the particle size of the phosphor fine particles can be reduced as compared with the case where a solid phase method or the like is used. Can be. By using nano-sized phosphor fine particles, it is possible to achieve high brightness when used in a light-emitting element or the like. When the phosphor fine particles are used in a light emitting device used for a display device or the like, the phosphor fine particles having a smaller particle size emit light more than the phosphor fine particles having a larger particle size in the same volume. Since the surface area used can be increased, the luminance of the light-emitting element can be improved. Moreover, by using nano-sized phosphor fine particles, the surface of the phosphor fine particles is activated and the luminous efficiency can be increased. For example, a conventional dispersion-type EL element (for example, a sheet-type printed EL element) uses phosphor fine particles having a particle diameter of about 20 to 30 μm and is an activator serving as an emission center contributing to light emission. The addition area of Cu, Cl, etc. (area where the activator such as Cu, Cl segregates) is 1 to several places. This is because the addition area of the activator can be increased by 10 to 100 times and the luminous efficiency can be improved. The segregated area is formed by, for example, Cu segregating at the twin interface between hexagonal crystals and cubic crystals. Thereby, a kind of nanowire is formed, and since the nanowire has conductivity, a path for propagating carriers in the ZnS crystal is created, and the efficiency of the light emission mechanism is improved. The mixed gas containing the base material and the activator includes those in which the base material powder and the activator powder are decomposed to an atomic level to be in a gas phase state. May contain other elements. For example, in general, a mixed gas contains a plasma gas for generating thermal plasma. In addition, elements other than the element forming the luminescent center added to the phosphor fine particles may be contained. For example, in order to suppress the afterglow, the element added to the phosphor fine particles in order to improve the luminous efficiency. May contain elements to be added to the phosphor fine particles. In this case, together with the base material and the activator, the raw materials of these additive elements are put into the thermal plasma.

In the method for producing the phosphor fine particles, since the powder is directly introduced into the thermal plasma, the production process can be simplified as compared with the case where the raw material powder is dispersed in a dispersion to form a slurry or the like. In addition, the dispersion liquid used when making the slurry does not remain in the thermal plasma device, so that contamination in the thermal plasma device can be reduced, and contamination of impurities in the manufactured phosphor fine particles is suppressed. can do.

In the above-mentioned passing step, the mixed gas containing the base material and the activator is rapidly cooled by coming out of the thermal plasma, but by controlling the temperature around the thermal plasma in advance, the base material and the luminescent center material It is preferable to control the temperature at which the water is rapidly cooled. The temperature around the thermal plasma can be adjusted, for example, by attaching a heater before and after the plasma chamber (chamber for generating plasma), or by providing a cryostructure that is cooled by circulating water or liquid nitrogen around the thermal plasma device. Can be controlled. For example, when the base material is a substance having a phase transition point, the structure of the phosphor fine particles produced by controlling the temperature so that the base material and the luminescent center material are rapidly cooled to a temperature lower or higher than the phase transition point. Can be controlled.

The method for producing phosphor fine particles using the above thermal plasma is clean and highly productive, can be applied to high melting point materials, and can be easily combined with other mechanisms as compared with other gas phase methods. It has the following advantages. For example, in the case of chemical vapor deposition or the like, an organic metal gas or a highly reactive gas is used. However, in the case of the thermal plasma method, since it is a physical reaction using plasma discharge, it is more than the case of using a chemical reaction. It is also considered that the contamination in the apparatus and the deterioration of the members constituting the apparatus can be reduced, and the influence when combined with other mechanisms is small. In addition, since the phosphor fine particles are manufactured using thermal plasma, the particle diameter can be reduced compared to the case where the phosphor fine particles are synthesized by, for example, a solid phase method. It is suitable as a manufacturing method.

The above-mentioned thermal plasma is a plasma in a thermal equilibrium state, and usually refers to a plasma having substantially the same temperature of ions, electrons, neutral atoms, etc. and those temperatures of 0.5 to 2.0 eV. By using thermal plasma, it is possible to easily heat an object to be heated to a high temperature. In addition, the reaction rate is greatly improved in thermal plasma, and it is possible to easily proceed even with a reaction with high activation energy. The plasma energy can be controlled, for example, by adjusting the voltage of plasma discharge. Further, when discharging is performed with an RF (Radio Frequency) power source, it can be controlled by adjusting the frequency.

Examples of the base material include oxides such as BaMgAl ₁₀ O ₁₇ (BAM), nitrides such as GaN and AlN, ZnS, ZnSe, MgS, BaAl ₂ S ₄ , and three-element compounds such as Ba ₂ SiS ₄ . Examples thereof include sulfides. Examples of the activator serving as the emission center include transition metal elements such as Cu, Mn, Ag, and Ir, and rare earth metal elements such as Ce, Eu, and Tb. In the manufacturing method using thermal plasma, since the base material and the activator material are decomposed to the gas phase state, phosphor fine particles in which the elements forming the emission center are uniformly added to the base material are generated. be able to. From this point of view, it is particularly effective to use a manufacturing method using thermal plasma as a method for manufacturing the phosphor fine particles. From the viewpoint of bringing the base material and the activator into a gas phase state, it is preferable that the center temperature of the thermal plasma is higher than the boiling point or sublimation point of the base material and the activator. Thereby, since the material powder of the phosphor fine particles can be in a gas phase state, the particle size of the phosphor fine particles can be reduced and the luminance can be improved. Further, the phosphor fine particles may contain other elements of the base material and the activator, and are not particularly limited. For example, an element for increasing luminous efficiency may be included, or an element for suppressing afterglow or the like may be included.

The phosphor fine particle production method of the present invention includes other steps as long as it includes a step of passing through a thermal plasma through a powder of a base material that is a base of the phosphor and an activator powder that is a light emission center of the phosphor. The component may or may not be included, and is not particularly limited.
The preferable form in the manufacturing method of the fluorescent fine particles of the present invention will be described in detail below.

The base material is zinc sulfide, and in the passing step, the zinc sulfide and the activator are passed by passing the zinc sulfide powder and the activator powder through a thermal plasma having a center temperature of 1000 ° C. or higher. It is preferable that the mixed gas is contained. Although the sublimation temperature of zinc sulfide at atmospheric pressure is 1180 ° C., the pressure of the thermal plasma device is lower than atmospheric pressure and the sublimation temperature is also low. Zinc powder and activator powder can be decomposed to the atomic level or cluster size into a gas phase. A cluster means a state in which several to several tens of atoms and molecules are gathered. In addition, since the sublimation point of zinc sulfide at atmospheric pressure is 1180 ° C., the passing step is to pass the zinc sulfide powder and the activator powder through a thermal plasma having a center temperature of 1180 ° C. or higher. Preferably, according to this, if the pressure in the thermal plasma apparatus is equal to or lower than the atmospheric pressure, the zinc sulfide powder and the activator powder can be sufficiently brought into a gas phase state. When the temperature of the thermal plasma is lower than the sublimation temperature, the thermal plasma may pass through the thermal plasma without being decomposed to the atomic level. The center temperature of the thermal plasma is preferably 10000 ° C. or less from the viewpoint of the stability of the thermal plasma apparatus. When the temperature is 10000 ° C. or higher, the temperature of the thermal plasma generated in the thermal plasma apparatus may be unstable. Further, from the viewpoint of decomposing the zinc sulfide powder and the activator powder to the atomic level or cluster size, the center temperature of the thermal plasma is more preferably in the temperature range of 1100 to 2000 ° C., and the zinc sulfide sublimation is performed. From the viewpoint that the temperature is 1180 ° C, the center temperature of the thermal plasma is more preferably 1180 to 2000 ° C. From the viewpoint of setting the central temperature of the thermal plasma to 1000 ° C. or higher, it is preferable to discharge the plasma energy of the thermal plasma apparatus with an output of 10 kw or higher, preferably 20 kw or higher. The temperature of the zinc sulfide powder and the activator powder can be set to the temperature of the thermal plasma by allowing the zinc sulfide powder and the activator powder to pass through the thermal plasma.

It is preferable that the said passage process is what cools the mixed gas containing a zinc sulfide and an activator to 100-600 degreeC. According to this, the manufactured phosphor fine particles can be made into zinc sulfide having a cubic structure suitable as a phosphor preferentially. The mixed gas containing the zinc sulfide and the activator is rapidly cooled when exiting the thermal plasma, but may be cooled to a temperature of 100 to 600 ° C. within 5 seconds after exiting the thermal plasma. Preferably, it is more preferably cooled to a temperature of 100 to 600 ° C. within 1 second. If the time for cooling to a temperature of 100 to 600 ° C. exceeds 5 seconds, the production of hexagonal zinc sulfide may be excessively promoted. Zinc sulfide is a material generally used as a phosphor material, and has a structural phase transition point at 1020 ° C. under atmospheric pressure. A hexagonal high-temperature phase is stable at temperatures above 1020 ° C. At a temperature of 1020 ° C. or lower, the cubic low-temperature phase is stable. Therefore, when a phosphor is produced by a solid phase method, if it is fired at a temperature of 1020 ° C. or higher, it tends to be zinc sulfide having a hexagonal crystal structure. In addition, when producing zinc sulfide fine particles to which an activator is added by firing at a temperature of 1000 ° C. or less using a solid phase method, the elements constituting the powder of the activator are not sufficiently diffused, There is a possibility that the luminous efficiency may be lowered. In the present invention, after passing through a thermal plasma with a center temperature of 1000 ° C. or higher, the cubic zinc sulfide suitable for the phosphor is preferentially cooled by quenching to a temperature below the structural phase transition point of 100 to 600 ° C. And the particle size can be reduced. Moreover, it is difficult to set the temperature for rapid cooling to less than 100 ° C., and unnecessary costs for cooling may occur. Moreover, when it exceeds 600 degreeC, there exists a possibility that the content rate of the phosphor fine particle whose crystal system may be a hexagonal system may increase. In addition, although the structural phase transition point of zinc sulfide at normal pressure to which no activator is added is 1020 ° C., an activator such as Cu is added and the pressure is further reduced as in the present invention. In the case, the structural phase transition point may change to around 700 ° C. From this point, it is preferable to rapidly cool to 600 ° C., which is a temperature below the structural phase transition point. The structural phase transition point also changes depending on compressive stress (mainly, strain stress generated at the twin interface due to the difference in the heat shrinkage coefficient between hexagonal and cubic). For this reason, the above-mentioned passing step is to cool the mixed gas containing zinc sulfide and the activator to 100 to 600 ° C., so that the phosphor fine particles having high luminance can be obtained. As the activator, Cu, Mn, chlorine (Cl) or the like can be used. When Cu is used as an activator, Cu _x S _y compound formed at the interface between Cu and ZnS is generally highly conductive, so it is preferable to use Cu as the activator. . What forms an interface is preferable in forming a heterojunction (Cu _x S _y / ZnS) among Cu _x S _y in which x <y. It is particularly preferable to use Cu when the rapid cooling is performed in a temperature range of 100 to 600 ° C. Moreover, it is preferable that the pressure in a thermal plasma apparatus is a vacuum atmosphere with a large mean free process distance. Therefore, the pressure range in the thermal plasma apparatus is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻² Pa, more preferably about 1 × 10 ⁻³ Pa.

It is preferable that the said passage process is what cools the mixed gas containing a zinc sulfide and an activator to 300-500 degreeC. By setting the cooling temperature to 300 to 500 ° C., the proportion of cubic zinc sulfide can be increased, and phosphor particles with higher brightness can be obtained.

The present invention is also a phosphor fine particle produced by using the method for producing a phosphor fine particle. By manufacturing using a thermal plasma apparatus, the particle diameter of the phosphor fine particles can be made finer than when manufactured by a solid phase method or the like, and an EL element using the phosphor fine particles has a high luminance. Can be. From the viewpoint of obtaining high brightness, the particle size is preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 100 nm or less. FIG. 5 is a schematic diagram showing one phosphor particle. When twin crystals of a hexagonal crystal structure 18 and a cubic crystal structure 17 are formed in the phosphor particles 15, twin crystals are formed. There is an interface 16. Thus, it is preferable that the phosphor particles have at least one twin interface in one phosphor particle, and the number of twin interfaces is preferably higher. In addition, the number of twin interfaces can be confirmed by observing a back electron diffraction image (EBSP image) of the phosphor powder. The average particle diameter can be calculated from the diffraction peak width of the X-ray diffraction measurement using the Scherrer formula shown by the following formula (1). In the following formula (1), T is the size of the crystal grain, λ is the wavelength of the X-ray used in the X-ray diffraction measurement, B is the half width of the peak, and θ is the diffraction angle.
T = 0.9λ / (B · cos θ) (1)

The base material is zinc sulfide, and the phosphor fine particles are preferably phosphor fine particles substantially composed of cubic crystals. Here, being substantially composed of cubic crystals means that 50% or more of cubic crystals are contained. In zinc sulfide, there are hexagonal wurtzite crystals that are high-temperature phases and cubic sodium chloride crystals that are low-temperature phases, but when zinc sulfide is used as a phosphor, it is once hexagonal crystals. When the formed ZnS is transferred to a cubic crystal, since the amount of twin interfaces is larger when the amount of cubic crystal is relatively larger than that of hexagonal crystal, the cubic crystal has higher brightness than the hexagonal crystal. Obtainable. The phosphor fine particles may contain a small amount of hexagonal zinc sulfide, but it is preferably cubic zinc sulfide at a ratio of at least 80%, more preferably 90% or more. Zinc sulfide is preferred. The proportion of cubic crystals can be determined from the diffraction intensity ratio of α-ZnS (wurtzite) and β-ZnS (zincblende) by X-ray diffraction (XRD) measurement. In the phosphor fine particles using zinc sulfide as a base material, copper is preferably added as an emission center, and the addition ratio of copper to the base material is more preferably 0.01 mol%. The EL element including the phosphor fine particles can be used as a full-color display, a lighting fixture, or the like.

The present invention is also an electroluminescence display device including phosphor fine particles manufactured by the above manufacturing method. According to this, an EL display device with higher luminance can be obtained by providing phosphor fine particles having a small particle size and high luminance. As an EL display device, for example, a phosphor layer is mixed with a binder material such as a cyano resin or a polyester resin, and a light emitting layer printed in a paste form is sandwiched between electrodes from both sides, and light is emitted by applying a voltage. And the like. In order to extract emitted light to the outside, at least one of the electrodes sandwiched from both sides is preferably a transparent electrode such as indium tin oxide (ITO). In addition, it is preferable to include a driver circuit for controlling light emission.

The present invention is also a method for producing an electroluminescence (EL) display device including the phosphor fine particles produced by the method for producing phosphor fine particles. By using the phosphor fine particles produced by the above production method as a phosphor used in an EL display device, an EL display device with higher luminance can be obtained.

According to the method for producing phosphor fine particles of the present invention, the production process can be simplified, and phosphor particles having a nano-size particle size and high brightness can be produced.

EXAMPLES Although an Example is hung up below and this invention is demonstrated still in detail with reference to drawings, this invention is not limited only to these Examples.

Example 1
FIG. 1 is a schematic view showing a configuration of a thermal plasma apparatus and a method for producing phosphor fine particles. A thermal plasma apparatus (manufactured by Nissin Engineering Co., Ltd.) was used as an apparatus for producing phosphor fine particles. In the thermal plasma apparatus 100, a raw material supply apparatus 106 is connected to a chamber 102 for cooling. The raw material supply apparatus 106 has a pipe 110 connected to plasma gas supply sources 101a and 101b, and a raw material of phosphor fine particles. A pipe for supplying the gas from the outside is connected. In addition, a high-frequency oscillation coil 105 is disposed outside the raw material supply device 106 so as to surround the periphery of the raw material supply device 106, whereby the thermal plasma 14 can be generated inside the raw material supply device 106. A filter 103 for collecting the formed phosphor fine particles is provided in the chamber 102, and a pipe 104 for sucking the gas in the chamber 102 through the filter 103 is provided. Further, more efficient temperature control can be performed by attaching a heater around the chamber 102 of the thermal plasma apparatus 100, or by attaching a pipe for circulating water or liquid nitrogen to circulate water or liquid nitrogen. Can do.

A method for producing zinc sulfide fine particles to which copper serving as a light emission center is added according to Example 1 will be described with reference to FIG. First, the inside of the chamber 102 is evacuated, and then Ar gas or N ₂ gas is introduced into the raw material supply apparatus 106 from the plasma gas supply sources 101 a and 101 b through the pipe 110. Ar gas was 3 cm ³ / min. N ₂ gas is 3 cm ³ / min. To the raw material supply device 106 at a flow rate of At this time, the pressure in the chamber is set to 1 × 10 ⁻³ Pa. Then, thermal plasma 14 is generated with plasma energy of 20 kW. At this time, the temperature of the central portion 14a of the thermal plasma 14 is 2000 ° C., and the temperature of the outer peripheral portion 14b of the thermal plasma 14 is 200 to 500 ° C. In addition, when manufacturing a phosphor material using zinc sulfide as a base material, it is preferable to use Ar gas as a plasma gas, but nitrogen, argon, hydrogen, or the like can also be used.

Next, 50 g of zinc sulfide powder 11 having a particle size of 1 to 5 μm is used as a base material of phosphor fine particles, and 0.5 g of copper sulfide powder 12 is used as an activator serving as a light emission center, from the raw material supply device 106 of the thermal plasma apparatus. throw into. The charged zinc sulfide powder 11 and copper sulfide powder 12 pass through the center 14a of the thermal plasma and are in a gas phase state decomposed to the atomic level. Zinc sulfide and copper sulfide in a gas phase state are drawn into the chamber 102 after a residence time of 10 ms in the thermal plasma 14. The zinc sulfide and copper sulfide in the gas phase are rapidly cooled to 100 to 200 ° C. immediately after passing through the thermal plasma 14. Aggregation occurs due to the rapid cooling, and the phosphor fine particles 13 are generated. The fluorescent fine particles 13 formed by aggregation are collected by the filter 103, and the fluorescent fine particles are carried out by opening the chamber from the portion indicated by the white arrow. At this time, the average particle diameter of the produced ZnS: Cu phosphor fine particles 13 is 97 nm, and nano-sized phosphor fine particles are produced. Further, the proportion of cubic crystals in the produced phosphor fine particles is 60%, and the rest are hexagonal crystals. And the twin interface of a hexagonal crystal and a cubic crystal existed in the ratio of 1-2 places in one fluorescent substance particle. Here, in FIG. 2, the result of having performed X-ray diffraction measurement about the fluorescent substance fine particle produced | generated in Example 1 is shown. The average particle size is calculated using the Scherrer equation from the half-value width of the diffraction peak of the X-ray diffraction measurement. The half-value width of the diffraction peak does not change theoretically even if the half-value width of any peak on the diffraction surface is used, but in order to reduce the measurement error, the peak of the diffraction surface showing the maximum peak value should be used. preferable. For example, it is preferable to use the full width at half maximum of the diffraction plane of β-ZnS (200) for cubic crystals of zinc sulfide and the diffraction plane of α-ZnS (100) for hexagonal crystals.

The phosphor fine particles thus produced can have a small particle size distribution width, a uniform particle size, and a small amount of coarse particles.

The ZnS: Cu fine particles obtained here are mixed with a binder material to form a paste. Then, an inorganic EL panel is manufactured by printing the paste-like ZnS: Cu fine particles. At this time, the inorganic EL panel includes an inorganic EL element configured by sandwiching a light emitting layer containing fine particles in a binder material between an indium tin oxide (ITO) electrode and an electrode made of silver (Ag). Yes.

(Example 2)
In the method for producing zinc sulfide fine particles to which copper serving as an emission center according to Example 2 is added, the amount of copper sulfide powder charged from the raw material supply device of the thermal plasma apparatus is 0.1 g (added with 1% by weight of copper sulfide). This is the same as Example 1. The average particle diameter of the ZnS: Cu phosphor fine particles produced in Example 2 is 10 nm, and nano-sized phosphor fine particles are produced. Further, the proportion of cubic crystals in the produced phosphor fine particles is 50%, and the rest are hexagonal crystals. And the twin interface of a hexagonal crystal and a cubic crystal existed in the ratio of 1-2 places in one fluorescent substance particle. Here, in FIG. 3, the result of having performed the X-ray-diffraction measurement about the fluorescent substance fine particle produced | generated in Example 2 is shown. Similar to Example 1, the average particle diameter is calculated using the Scherrer equation from the half-value width of the diffraction peak of the X-ray diffraction measurement.

(Comparative Example 1)
The method for producing zinc sulfide fine particles according to Comparative Example 1 is the same as that of Example 1 except that no copper sulfide powder is added from the raw material supply device 106 of the thermal plasma apparatus (no copper sulfide is added). . The average particle diameter of the phosphor particles of ZnS produced in Comparative Example 1 is 12 nm, which is larger than that of the phosphor particles produced in Examples 1 and 2. Further, since the copper sulfide powder is not added, the phosphor fine particles are not formed. Here, in FIG. 4, the result of having performed the X-ray-diffraction measurement about the zinc sulfide fine particle produced | generated by the comparative example 1 is shown. Similar to Example 1, the average particle diameter is calculated using the Scherrer equation from the half-value width of the diffraction peak of the X-ray diffraction measurement.

(Comparative Example 2)
In Comparative Example 2, a method for producing zinc sulfide fine particles using a solid phase method will be described. First, 50 g of zinc sulfide powder having a particle diameter of 1 to 5 μm is used as a base material of the phosphor fine particles, and 0.05 g of copper powder is wet mixed as an activator serving as a light emission center and dried. Thereafter, the dried raw material powder is filled in a quartz crucible or the like and fired at 800 ° C. in an inert gas atmosphere. After firing, the copper sulfide adhering to the surface of the phosphor fine particles is washed and classified. The average particle size of the phosphor fine particles thus produced is 10 to 30 μm. Further, the proportion of cubic crystals in the produced phosphor fine particles is 95%, and the rest are hexagonal crystals. And the twin interface of a hexagonal crystal and a cubic crystal existed in the ratio of 1-2 pieces in 10 fluorescent substance particles. The ZnS: Cu fine particles obtained here are mixed with a binder material to form a paste. Then, the paste-like ZnS: Cu fine particles are printed to produce an inorganic EL panel.

It is the schematic which shows the structure of a thermal plasma apparatus, and the manufacturing method of fluorescent microparticles. FIG. 4 is a diagram showing the results of X-ray diffraction measurement of zinc sulfide fine particles according to Example 1. It is a figure which shows the result of the X-ray-diffraction measurement of the zinc sulfide fine particle which concerns on Example 2. FIG. It is a figure which shows the result of the X-ray-diffraction measurement of the zinc sulfide fine particle concerning the comparative example 1. It is a schematic diagram which shows the twin interface in the particle | grains of fluorescent substance.

Explanation of symbols

11: powder of base material 12: activator powder 13: phosphor fine particles 14: thermal plasma 14a: thermal plasma central portion 14b: thermal plasma outer peripheral portion 15: phosphor particles 16: twin interface 17: cubic structure 18 : Hexagonal structure 101a, 101b: plasma gas supply source 102: chamber 103: filter 104: gas suction tube 105: coil for high frequency oscillation 106: raw material supply device

Claims (7)

A method for producing phosphor fine particles, comprising:
The production method includes a step of passing through a thermal plasma a powder of a base material that is a base material of the phosphor and a powder of an activator that contains an element that is a light emission center of the phosphor. Manufacturing method. The base material is zinc sulfide,
In the passing step, the zinc sulfide powder and the activator powder are passed through a thermal plasma having a center temperature of 1000 ° C. or higher to form a mixed gas containing zinc sulfide and the activator. The method for producing phosphor fine particles according to claim 1. The method for producing phosphor fine particles according to claim 2, wherein in the passing step, a mixed gas containing zinc sulfide and an activator is cooled to 100 to 600 ° C. 4. The method for producing phosphor fine particles according to claim 3, wherein in the passing step, the mixed gas is cooled to 300 to 500 ° C. A phosphor fine particle produced using the method for producing a phosphor fine particle according to claim 1. The base material is zinc sulfide,
6. The phosphor fine particles according to claim 5, wherein the phosphor fine particles are substantially composed of cubic crystals. An electroluminescent display device comprising the phosphor fine particles according to claim 5.

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