JP2006232919A - Method for producing core/shell particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing core/shell particles consisting of a desired composition and having a sufficiently thick thickness of the shell, simply and surely. <P>SOLUTION: This method for producing the core/shell particles comprises (1) (misting process) a process of forming mist with dispersion dispersing cores in the solution of a raw material of shell of a crystalline inorganic substance, (2) (drying process) covering the surface of the cores with the raw material of shell of the crystalline inorganic substance by drying the misted dispersion, (3) (first heat-treating process) forming an inorganic substance temporary shell on the surface of the cores by heat-treating at a temperature higher than the decomposition temperature of the raw material of the crystalline inorganic substance shell and (4) (second heat-treating process) forming the crystalline inorganic substance shell on the surface of the core by heat-treating at a temperature for crystallizing or improving the crystallinity of the temporary shell of the crystalline inorganic substance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing core-shell particles, particularly a method for producing core-shell particles that are phosphor particles, and a method for producing core-shell particles that are electroluminescent phosphor particles.

  For the purpose of protecting chemically or physically unstable substances and giving them special functions, the substance that becomes the core (called the core) is changed by the substance that becomes the shell (called the shell) The technique of coating is known. Further, the particles thus manufactured are generally called core-shell particles.

  There are many known uses of core-shell particles, such as silver halide particles in photographic light-sensitive materials and silicon elastomer fine particles in thermosetting resins, but in recent years, phosphor particles, particularly electroluminescent elements in electroluminescent devices. The use as luminescent phosphor particles has been attracting attention.

  The electroluminescence element is expected to be used as a new display element that does not require a separate light source as a surface light source that emits light. There are two types of conventional electroluminescence elements, “dispersion type” and “thin film type”. First, the basic structure, light emission mechanism, and features of each of the conventional dispersion type and thin film type electroluminescence elements described in Non-Patent Document 1 and the like will be schematically described below.

  Typically, in the dispersion type electroluminescent device, a transparent electrode 64 is formed by applying a transparent conductive film on a transparent substrate 62 such as glass or a polyethylene terephthalate (PET) sheet as in the device 60 shown in FIG. In addition, a light emitting layer 66, an insulating layer 68, and a back electrode 70 in which phosphor particles 66a are freely dispersed in a dielectric binder 66b are laminated thereon. Furthermore, an additional layer such as a surface protective layer may be provided. When an AC voltage is applied between the transparent electrode 64 and the back electrode 70, the phosphor particles 66 a inside the light emitting layer 66 exhibit electroluminescence, and the light is extracted through the transparent electrode 64 and the transparent substrate 62.

  The insulating layer 68 is for blocking the current path and applying a stable high electric field to each phosphor particle 66a. However, the above-described free dispersion of the phosphor particles 66a is completely realized, and light emission is achieved. When the current path in the layer 66 is interrupted, the insulating layer 68 may not be provided.

  As the phosphor particles of the dispersion type electroluminescent element, particles in which an activator is added to the phosphor base material are used. A typical example is ZnS: Cu, Cl that emits blue-green light. Depending on the desired emission color, ZnS: Cu, Al (green), ZnS: Cu, Cl, Mn (orange yellow) ) Etc. are used. Here, it is said that the activator needs to contain copper from the following light emission mechanism etc., and the thing put into practical use is only ZnS. It is considered that the particle diameter of about 20 μm is optimal for the phosphor particles of the dispersion type electroluminescence element. When the particle size is reduced, the luminance is significantly reduced.

  The light emission of the dispersive electroluminescent element is due to the fact that the element added as an activator acts as a donor and acceptor and recombination occurs. For example, in the case of the above ZnS: Cu, Cl, Cl acts as a donor and Cu acts as an acceptor.

In addition, this light emission does not occur uniformly throughout the phosphor particles, but Cu ₂ S needle crystals are precipitated along the lattice defects of the ZnS particles, and occur locally at the tip portion thereof. It is believed that.

In the thin film type electroluminescent device, typically, like the device 80 shown in FIG. 6, a transparent electrode 84 is formed on a transparent substrate 82 in the same manner as the dispersion type, and a first insulating layer is formed thereon. 86a, a phosphor light-emitting layer 88 formed in a thin film by a technique such as vacuum deposition or sputtering, a second insulating layer 86b, and a back electrode 90 are laminated. Furthermore, an additional layer such as a surface protective layer or a buffer layer between the light emitting layer and the insulating layer may be provided. Generally, each layer other than the light emitting layer 88 is often formed by a thin film forming technique such as vacuum deposition. The element 80 of FIG. 6 is drawn to a thickness substantially the same as that of the element 60 of FIG. 5 for the sake of explanation, but in practice, the thickness of the thin film type electroluminescent element is 1/100 of that of the distributed type electroluminescent element. Degree. However, recently, a thick dielectric layer having a high dielectric constant is provided by using a printing technique, and the total film thickness is about one-tenth of that of the distributed element. When an alternating voltage is applied between the transparent electrode 84 and the back electrode 90, the light emitting layer 88 exhibits electroluminescence, and the light is extracted through the transparent electrode 84 and the transparent substrate 82. A typical phosphor material used for the light emitting layer 88 is ZnS: Mn in which Mn serving as a light emission center is doped in a base material ZnS, which emits orange-yellow light. In recent years, BaAl ₂ S ₄ : Eu that emits blue light has been developed and attracts attention. In the case of the thin film type, a configuration called “dual pattern method” or “triple pattern method” in which light emitting portions doped with different types of light emission centers corresponding to a plurality of colors are arranged two-dimensionally, Application to a color display or the like is possible by overlapping the structure shown in FIG. 6 corresponding to a plurality of colors.

  Dispersed electroluminescent devices emit light by recombination between donor and acceptor, whereas thin-film electroluminescent devices emit light by collision excitation of emission centers by hot electrons running in the base material. . In the hot electrons, when a voltage is applied, electrons injected into the light emitting layer 88 from the interface between the light emitting layer 88 and the insulating layers 86a and 86b and / or traps in the light emitting layer 88 are accelerated under a high electric field. It is a thing.

  Comparing the dispersion type and the thin film type electroluminescence elements, there are advantages and disadvantages. The advantages of the distributed type are that the manufacturing process can be simplified without vacuum deposition, etc., so that the manufacturing cost is low, the device can be easily increased in size, and flexible. The point which can also manufacture an element is mentioned. Disadvantages are lower brightness than a thin film type, less color diversity, and larger particle size of dispersed phosphor particles, which is not suitable for applications such as high-definition displays. On the other hand, the advantages of the thin film type include that it is brighter and brighter than the dispersion type, that there are many variations of the light emission center that determines the color, that various colors can be expressed, and that high-definition display is possible. Disadvantages include complicated manufacturing processes and high costs. Further, in the thin film type, since most of the emitted light is totally reflected at the interface between the light emitting layer and the insulating layer, the light extraction efficiency is very low, and only about 5 to 10% is a problem. .

  On the other hand, in Patent Documents 1 and 2, etc., the phosphor particles dispersed in the light emitting layer are conventionally used in the light emitting layer of the thin film type element while adopting a dispersion-like structure similar to the structure shown in FIG. An electroluminescence element using a phosphor material that has been made into a particle shape has also been proposed. Further, in Patent Document 1, in place of particles made of only a phosphor, a core-shell particle provided with a phosphor shell covering a dielectric core and a particle provided with a dielectric coating layer covering the phosphor shell are used. There has also been proposed an electroluminescent device having a dispersion-like structure using a phosphor used for a light emitting layer of a conventional thin film type device as a material of a body shell. In the electroluminescence element as described in these Patent Documents 1 and 2, the phosphor portion is formed from the interface between the phosphor portion in the light emitting layer and the surrounding dielectric and / or the trap in the phosphor portion. It is considered that electrons are injected into the interior, and the electrons are accelerated to become hot electrons to excite the light emission center in the phosphor portion, thereby realizing a light emission mechanism similar to that of a conventional thin film type device. Since the basic structure itself is the same as that of a conventional distributed element, the manufacturing cost can be kept low.

Electroluminescence with a dispersive-like structure, whether using a conventional phosphor containing copper or using a phosphor used in the light emitting layer of the thin film element In order to obtain high light emission efficiency in the device and / or to start light emission at a low applied voltage, the voltage applied to the device needs to be efficiently applied to the phosphor particles in the light emitting layer. As a means for that, for example, in the electroluminescent element described in Patent Document 2, a dielectric material having a high dielectric constant such as BaTiO ₃ is used as a binder in the light emitting layer, and phosphor particles are dispersed therein. Yes.

By the way, as a manufacturing method of core-shell particles, various things besides the said patent documents 1 and 2 are proposed. Patent Document 3 discloses a method for producing core-shell particles, in which a phosphor-constituting element compound and an inorganic substance that is not a phosphor are mixed and baked to coat a core made of the phosphor on a core made of the inorganic substance. Thus, there is disclosed a method in which a phosphor constituent element compound is precipitated on the surface of the inorganic substance particles in water, and then dried and fired. Patent Document 4 discloses a method for producing core-shell particles, characterized by using a spray pyrolysis method in which nanoparticles that become shells are dispersed in a raw material solution of core particle constituent elements. Here, the spray liquid is atomized by ultrasonic spraying.
International Publication No. 02/080626 Pamphlet Japanese Patent Publication No. 2000-195664 Japanese Patent Publication No. 2002-180041 Japanese Patent Publication No. 9-309768 Toshio Higuchi, “Electroluminescent Display”, first edition, Sangyo Tosho Co., Ltd., July 25, 1991

  In the above-mentioned core-shell particles, it is important that the core and shell composition of the produced particles are desired in view of the functions required for each application. In addition, although it varies depending on the application, it is generally important to increase the thickness of the shell, particularly in the case where the shell is a phosphor, because of the required luminance.

  In Patent Document 3, since the precipitation rate differs depending on the element, it is difficult to control the composition of a compound having a composite composition. In addition, it is difficult to synthesize compositions (sulfides, nitrides) other than oxides. Furthermore, it is difficult to obtain a thick film shell (100 nm or more).

  In Patent Document 4, since the core is also generated by spray pyrolysis, the shell raw material may enter the core droplet, and the core-shell structure may not be as desired. It is considered that various parameters need to be considered in order to control the nanoparticles to be shells to be deposited on the surface, and it is not easy to obtain core-shell particles having a desired shape and composition.

  Accordingly, an object of the present invention is to provide a method for producing core-shell particles, which is simple and reliable, has a desired composition, and has a sufficiently thick shell.

  The inventor of the present invention atomizes the core particles together with the liquid containing the shell raw material, and applies the steps of drying and heat treatment, so that the solute in the liquid phase and the uniformity of the particles are the solute in each of the mist droplets. Overcoming the drawbacks of the conventional technology that the desired core-shell structure cannot be obtained easily while ensuring the advantage of spray pyrolysis, which is superior in the uniformity of the composition of the resulting product by inheriting the uniformity of the particles. We have found that we can do it and have arrived at the present invention.

The method for producing the first core-shell particles according to the present invention includes:
(1) an atomization step of atomizing a dispersion in which a core is dispersed in a raw material solution of a crystalline inorganic substance shell;
(2) a drying step of coating the raw material of the crystalline inorganic substance shell on the surface of the core by drying the atomized dispersion;
(3) a first heat treatment step of forming an inorganic material temporary shell on the surface of the core by performing a heat treatment at a temperature equal to or higher than a decomposition temperature of the raw material of the crystalline inorganic material shell;
(4) a second heat treatment step of forming the crystalline inorganic material shell on the surface of the core by performing a heat treatment at a temperature at which the crystalline inorganic material temporary shell crystallizes;
It is characterized by having.

The method for producing the second core-shell particles according to the present invention includes:
(1) An atomization step of atomizing a dispersion liquid in which a core, fine particles having the same constituent metal elements as the crystalline inorganic substance shell and sufficiently smaller than the core, and a dispersant are dispersed;
(2) A drying step of coating the surface of the core with fine particles of the crystalline inorganic substance shell by drying the atomized dispersion;
(3) a first heat treatment step of forming an inorganic material temporary shell on the surface of the core by performing a heat treatment at a temperature at which the fine particles of the crystalline inorganic material shell are fused together;
(4) a second heat treatment step of forming the crystalline inorganic material shell on the surface of the core by performing a heat treatment at a temperature at which the inorganic material temporary shell crystallizes;
It is characterized by having.

  In the first and second core-shell particle manufacturing methods of the present invention, the drying step and the first heat treatment step can be performed by the same heat treatment apparatus. Further, the drying step and / or the first heat treatment step and the second heat treatment step can be performed by the same heat treatment apparatus.

In the first and second core-shell particle manufacturing methods of the present invention, the crystalline inorganic substance shell can be a phosphor. The phosphor may be an electroluminescent phosphor, and in particular ZnS: Mn or Zn ₂ SiO ₄ : Mn.

In the first and second core-shell particle manufacturing methods of the present invention, the core can be a dielectric having a high dielectric constant. Here, the dielectric having a large dielectric constant means a dielectric having a relative dielectric constant of about 100. The dielectric can be BaTiO ₃ .

  The combination of the shell and core materials can be selected as appropriate.

  Here, in the present invention, the “core-shell particle” refers to the entire particle, and when used in an electroluminescent device, refers to the entire particle dispersed in the light emitting layer. That is, the light emission by electroluminescence actually occurs in the phosphor portion in the particle. In the present invention, the entire particle including the core, and the dielectric coating layer, the buffer layer, etc. It shall be called “particle”.

  In addition, the electroluminescent phosphor particles produced by the above-described method for producing core-shell particles of the present invention include a core and a phosphor shell provided outside the core. Is shown. For example, an additional layer such as a buffer layer may be provided between the core and the phosphor shell, or a pair of an additional dielectric coating layer and the phosphor shell on the outside of the phosphor shell, or the surface A protective layer or the like may be provided.

  In the present invention, the particle diameters of core-shell particles, core particles, shell raw material particles and the like are defined by the diameter.

  In the method for producing core-shell particles according to the present invention, the fact that the fine particles are “sufficiently smaller than the core” means that the particle size of the fine particles is 1/5 or less of the particle size of the core.

  In the first method for producing core-shell particles according to the present invention, since the step of atomizing the dispersion in which the core is dispersed in the crystalline inorganic substance shell raw material solution is provided, the drying and heat treatment are performed. There is no fear that the core cannot be formed well and the shell raw material is generated in the middle as in the case where the core is formed in the process of spray pyrolysis. Therefore, core-shell particles having a desired shape can be obtained reliably and easily. Further, in spray pyrolysis, a film of a dispersion liquid thicker than the diameter of the core can be attached around the core, and as a result, core-shell particles having a thick film thickness can be obtained even after heat treatment.

  Further, since all the constituent materials other than the core are in solution at the time of atomization, the shell raw material is uniformly distributed on the core surface, and core-shell particles having a uniform shell composition can be obtained.

  In the second method for producing core-shell particles according to the present invention, a step of atomizing a dispersion in which the core and the crystalline inorganic substance shell are dispersed together with fine particles having the same constituent metal element is provided and then dried. -Since the heat treatment is performed, there is no fear that the core cannot be made well as in the case where the core is produced in the process of spray pyrolysis, and the shell raw material is generated in the middle. Therefore, core-shell particles having a desired shape can be obtained reliably and easily. Further, in spray pyrolysis, a film of a dispersion liquid thicker than the diameter of the core can be attached around the core, and as a result, core-shell particles having a thick film thickness can be obtained even after heat treatment.

Moreover, since not only the core but also the shell raw material is atomized in the form of particles, unlike the prior art, there is no concern that the counter anion of the target element in the liquid phase remains in the core-shell particles, and it is easily desired The core-shell particles having the composition can be obtained.
In the first and second core-shell particle manufacturing methods of the present invention, when the drying step and the first heat treatment step are performed by the same heat treatment apparatus, the same effects as described above are obtained. Thus, core-shell particles can be easily obtained with a small number of steps. In addition, when the drying step and / or the first heat treatment step and the second heat treatment step are performed by the same heat treatment apparatus, the number of steps can be reduced while producing the same effect as described above. Thus, core-shell particles can be easily obtained.

  In the first and second core-shell particle production methods of the present invention, when the crystalline inorganic substance shell is a phosphor, the core-shell particles that can be used for a display or the like can be simply and You can definitely get it. When the phosphor is an electroluminescent phosphor, core-shell particles that can be used in an electroluminescent element can be obtained easily and reliably while exhibiting the same effects as described above.

  In the first and second core-shell particle manufacturing methods of the present invention, when the core is made of a high dielectric material, the electroluminescent element and the like can be produced while producing the same effects as described above, and the like. The core-shell particles that can be used in the above can be obtained easily and reliably.

  Moreover, the core-shell particle | grains which can be used more suitably for an electroluminescent element can be obtained by selecting suitably about the combination of the substance of the said shell and core.

  Below, the manufacturing method of the 1st core shell particle | grains of this invention is demonstrated in detail.

[Core dispersion process in shell material solution]
In preparation of the dispersion, a compound, a core particle, and a dispersion solvent which are raw materials for the target crystalline inorganic substance shell are prepared.

  Examples of the shell material that can be used in the present invention include inorganic substances that are soluble in a dispersion solvent and combine with each other by firing to exhibit single-phase crystallinity. In the manufacturing method of an electroluminescent light emitting element, it can select suitably with the fluorescent substance shell compound seed | species of the target electroluminescent fluorescent substance particle. For example, nitrate, acetate or chloride of the element is used as a raw material for the metal element in the phosphor, a sulfur compound such as thiourea or thioacetamide is used as the sulfur source, and a silicon-containing organic compound is used as the silicon source. Can be used.

  What is necessary is just to calculate suitably the weight ratio of a core particle and a shell raw material according to the desired film thickness and desired composition of the target core-shell particle.

  As can be seen from the above, the dispersion solvent can dissolve the shell material, and examples thereof include water and ethanol.

  In order to ensure uniform dispersibility in the dispersion of the compound serving as the raw material for the target crystalline inorganic substance shell, a dispersant may be added to the dispersion. As the dispersant, hydroxycellulose or the like can be used. The dispersant is not necessary when the core-shell particles actually perform their functions, and is decomposed or burned by a heating process described later.

As the phosphor shell compound species of the electroluminescent phosphor particles targeted by the first core-shell particle production method of the present invention, copper such as ZnS: Cu, Cl used in the conventional dispersion type electroluminescence element is used. Examples thereof include phosphors containing phosphors, and phosphors containing emission centers excited by hot electrons conventionally used in thin-film electroluminescent elements, such as ZnS: Mn. When the latter is used, the light emission mechanism itself is similar to a conventional thin film type element, and the total reflection condition is not satisfied due to the shape effect of the phosphor coating layer and the light scattering effect of the entire light emitting layer. Since the light extraction efficiency from the light emitting layer is improved as compared with the conventional thin film type device, there is an advantage that high luminance can be obtained as compared with the conventional dispersion type device and the thin film type device. Examples of such phosphors other than ZnS: Mn include those shown in the following table.

The core material that can be used in the present invention can be selected according to the use of the core-shell particles, but particularly for electroluminescent light-emitting elements, BaTiO ₃ , SrTiO ₃ , HfO ₂ , SiO ₂ , TiO ₂ , Al _2. O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , BaTa ₂ O ₆ , Sr (Zr, Ti) O ₃ , PbTiO ₃ , Si ₃ N ₄ , ZnS, ZrO ₂ , PbNbO ₃ , Pb (Zr, Ti) O ₃ etc. can be used. However, a material having a large dielectric constant is preferable in order to efficiently apply an electric field to the phosphor shell. When a dielectric coating layer is provided, the same material may be used for the dielectric coating layer and the dielectric core, but an electric field is efficiently applied to the phosphor shell while the shielding effect of the dielectric coating layer is kept low. For this purpose, it is preferable to use a material having a higher relative dielectric constant than the dielectric core.

  The core diameter of the dielectric core is preferably 0.05 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3.5 μm or less.

  This is because if the core diameter of the dielectric core is too small, there is a problem that the phosphor coating layer must be made too thin in order to concentrate the electric field on the phosphor coating layer. This is because if the core diameter is too large, the overall size of the luminescent particles becomes large, and problems such as impaired smoothness of the luminescent layer 16 occur. On the other hand, the size of the fine particles of the inorganic material shell raw material is preferably 1 nm or more and 0.1 μm or less.

In addition, although the shell is not a phosphor, the core-shell particles that can be produced by the manufacturing method according to the present invention are filled particles filled in a capacitor, the core is SrTiO ₃ or BaTiO ₃ , and the shell is CuO, MnO. ₂ are listed.

  The core is dispersed uniformly in the shell raw material solution by an ultrasonic vibration device, a magnetic stirrer, or the like.

[Dispersion liquid atomization process]
The dispersion is atomized by spraying. In the present invention, since it is necessary to atomize the core having a relatively large particle size, it is desirable to use a spray having a large atomizing force. For example, a two-fluid spray that actively inhales a gas such as air together with the liquid to be atomized and the like is used.

  In the present invention, by passing through the above-described steps, a mist droplet in which the inorganic material shell raw material solution is thickly attached around the core can be easily obtained.

  FIG. 1 shows an outline of a two-fluid spray. The two-fluid spray 100 includes a liquid supply unit 102 and a gas supply unit 104. The liquid 106 to be atomized is supplied from the liquid supply unit, and the compressed air 108 is supplied from the gas supply unit, for example. As shown in the figure, since the liquid to be atomized collides violently with the compressed air, the atomizing force is relatively large.

[Drying process]
Thereafter, the atomized particles are introduced into a drying chamber to volatilize the solvent portion of the crystalline inorganic substance shell raw material solution adhered around the core.

  The drying chamber is not required to have a special configuration, and a known drying chamber can be used.

  The drying time and temperature range can be determined as appropriate depending on the size of the core and the particle falling time associated with the gas flow rate in the drying chamber, the type of shell raw material and solvent, etc., but the drying time is about 1 second to 1 hour, and the temperature range is 30. C. to 300.degree. C. is preferred.

  As an atmosphere at the time of drying, in addition to normal air, an atmosphere reduced in pressure or substituted with nitrogen gas, Ar gas, or the like may be used.

  As described above, the solvent is removed and the core is coated with the crystalline inorganic material shell raw material, and is collected by, for example, a filter unit provided in the drying chamber.

[First heat treatment step]
The recovered particles are further heated at a temperature of, for example, 450 ° C. to 1000 ° C. to decompose the raw material of the crystalline inorganic material shell.

As an apparatus that can be used in the first heat treatment step, a heat treatment apparatus that can withstand the above-described raw material decomposition temperature is necessary. For example, an electric furnace equipped with a crucible can be used. At this time, when the target inorganic substance shell is made of sulfide, a reducing atmosphere, an inert gas atmosphere (which may contain a sulfur-based gas such as H ₂ S or CS ₂ ), or a vacuum atmosphere is used. When firing in an electric furnace equipped with a crucible in the atmosphere, it is desirable to fill the dummy particles made of particles having a composition close to the sulfide before firing.

  The heat treatment time can be 10 minutes to several days depending on the purpose, if the heat collected by the filter as described above is separately heat treated. Preferably, it is 20 minutes to 24 hours.

  By passing through the first heat treatment step, particles having an inorganic material temporary shell formed on the surface of the core are obtained.

  The obtained material to be heat-treated may be subjected to a loosening process, a sieving process or the like as necessary.

  In addition, as long as the drying chamber used in the said drying process can endure said raw material decomposition temperature, you may perform the said drying process and 1st heat processing process with the same heat processing apparatus. For example, a quartz tube furnace can be used. In this case, it is preferable that the heat treatment is performed within a time period during which the atomized particles do not fall (mostly several seconds to several minutes), and drying and first heat treatment, that is, raw material decomposition are performed. Thereby, the number of processes can be reduced. More preferably, the temperature is raised stepwise from a low temperature to a high temperature, followed by the first heat treatment after drying. Thereby, a denser inorganic substance temporary shell can be easily formed.

  As a heating apparatus capable of performing the above-mentioned stepwise temperature increase, there is a quartz tube furnace shown in FIG. The quartz tubular furnace 120 has a heating passage 122 made of quartz so as to withstand a temperature of 1000 ° C. The mist droplets supplied through the raw material supply port 124 sequentially pass through the heating regions 128a and 128b heated to predetermined temperatures by the heating devices 126a and 126b, respectively, and are sequentially heated to the respective temperatures. The heating devices 128a and 128b are designed so that the temperature of the heating zones 128a and 128b can be controlled independently. The mist droplets heated in this way are collected by a cartridge filter 132 provided in front of the exhaust port 130.

[Second heat treatment step]
What is formed on the surface of the particles obtained as described above is an amorphous or low crystallinity inorganic material temporary shell, and has not yet a structure capable of functioning as a core-shell particle. Therefore, this is further subjected to a second heat treatment step to crystallize or improve the crystallinity of the inorganic substance temporary shell so as to function as core-shell particles.

  When crystallization or crystallinity is improved, heat treatment is performed at a temperature of, for example, 600 ° C. to 1600 ° C., depending on the composition and crystal seed of the target crystalline inorganic substance shell.

As a heat treatment apparatus, a heat treatment apparatus capable of withstanding this temperature is required. For example, an electric furnace equipped with a crucible can be used. At this time, when the target inorganic substance shell is made of sulfide, a reducing atmosphere, an inert gas atmosphere (which may contain a sulfur-based gas such as H ₂ S, CS ₂ ), or a vacuum atmosphere is used. When firing in an electric furnace equipped with a crucible in the atmosphere, it is desirable to fill the dummy particles made of particles having a composition close to that of the sulfide before firing.

  The heat treatment time can be 10 minutes to several days depending on the purpose, if the heat collected by the filter as described above is separately heat treated. Preferably, it is 20 minutes to 24 hours.

  Through the second heat treatment step, core-shell particles in which a crystalline inorganic substance shell is formed on the surface of the core are obtained. The film thickness of the shell is generally in the range of 1 nm to 10 μm, preferably in the range of 10 nm to 5 μm.

  The obtained core-shell particles may be subjected to a loosening process, a sieving process, or the like, if necessary.

  If the drying chamber used in the drying step and / or the heat treatment apparatus used in the first heat treatment step can withstand the crystallization or crystallinity improvement temperature, the drying step and / or the first heat treatment step are used. The heat treatment step and the second heat treatment step may be performed by the same heat treatment apparatus. For example, an alumina tube furnace can be used. In the case where the drying process to the second heat treatment process are simultaneously performed, the heat treatment is performed within a time period during which the atomized particles do not fall (mostly several seconds to several minutes), and the drying, the first heat treatment, that is, the raw material decomposition, and It is preferable to perform the second heat treatment, that is, crystallization simultaneously. Thereby, the number of processes can be reduced. More preferably, the temperature is raised from a low temperature to a high temperature step by step, followed by drying, first heat treatment, and second heat treatment. Thereby, core-shell particles having a denser shell can be easily produced.

  As a heating apparatus capable of performing the above-mentioned stepwise temperature increase, there is an alumina tubular furnace shown in FIG. The alumina tubular furnace 140 has a heating passage 142 made of alumina so as to withstand a temperature of 1600 ° C. The mist droplets supplied through the raw material supply port 144 sequentially pass through the heating regions 148a, 148b and 148c heated to predetermined temperatures by the heating devices 146a, 146b and 146c, respectively, and sequentially heated to the respective temperatures. Is done. Heating devices 148a, 148b and 148c are designed to allow independent control of the temperature of heating zones 148a, 148b and 148c. The mist droplets heated in this way are collected by the cartridge filter 152 provided in front of the exhaust port 150.

  Next, the manufacturing method of the 2nd core shell particle | grains of this invention is demonstrated in detail.

[Dispersing process of core and shell fine particles in dispersion]
In preparation of the dispersion, a target crystalline inorganic substance shell fine particles, a dispersant for ensuring uniform dispersion in the dispersion of the left compound, core particles, and a dispersion solvent are prepared. You may use together the compound used as the raw material of a shell soluble in the dispersion solvent used for the 1st core shell particle manufacturing method of this invention.

  The shell raw material fine particles that can be used in the present invention do not need to be soluble in the dispersion solvent, but need to be made of an inorganic substance that exhibits crystallinity by a solid phase reaction. Particularly for electroluminescent light emitting devices, those mentioned as the phosphor shell compound species of the electroluminescent phosphor particles, which are intended in the method for producing the first core-shell particles of the present invention, can be used. That is, a phosphor containing copper such as ZnS: Cu, Cl or a phosphor containing ZnS: Mn and a luminescent center excited by hot electrons listed in Table 1, and is already in a particle shape. Are preferably used.

  If the said shell raw material microparticles | fine-particles have a commercially available thing, it may be used, and if there exists a thing with a large particle diameter, this may be grind | pulverized and used. The size of the shell raw material fine particles is preferably 1 nm or more and 0.1 μm or less. For convenience of coating efficiency, the particle diameter of the shell raw material fine particles is 1/5 or less of the core particle diameter, but preferably 1/20 or less.

  The weight ratio between the core particles and the shell raw material fine particles may be appropriately calculated according to the desired film thickness of the target core-shell particles.

  Examples of the dispersion solvent include water and ethanol.

  In order to ensure uniform dispersibility in the dispersion of the compound serving as the raw material for the target crystalline inorganic substance shell, a dispersant may be added to the dispersion. As the dispersant, hydroxycellulose or the like can be used. The dispersant is not necessary when the core-shell particles actually perform their functions, and is decomposed or burned by a heating process described later.

In addition, although the shell is not a phosphor, the core-shell particles that can be produced by the manufacturing method according to the present invention are filled particles filled in a capacitor, the core is SrTiO ₃ or BaTiO ₃ , and the shell is CuO, MnO. ₂ are listed.

  The core and shell raw material fine particles are dispersed uniformly in the dispersion solvent using an ultrasonic dispersion device, a homogenizer, a magnetic stirrer, or the like.

[Dispersion atomization process]
The dispersion is atomized by a spray nozzle. In the present invention, since it is necessary to atomize both the core having a relatively large particle diameter and the shell raw material fine particles, it is desirable to use a spray nozzle having a large atomizing force. For example, a two-fluid spray nozzle that actively inhales a gas such as air together with the liquid to be atomized to atomize the liquid.

  In the present invention, a mist droplet in which a solution containing the shell raw material fine particles is attached thickly around the core can be easily obtained through the above-described steps.

[Drying process]
Thereafter, the atomized particles are introduced into a drying chamber to volatilize the solvent portion of the shell raw material fine particle-containing solution attached around the core.

  The drying chamber is not required to have a special configuration, and a known drying chamber can be used.

  The drying time and temperature range can be determined as appropriate depending on the size of the core and the particle falling time associated with the gas flow rate in the drying chamber, the type of shell raw material and solvent, etc., but the drying time is about 1 second to 1 hour, and the temperature range is 30. C. to 300.degree. C. is preferred.

  As an atmosphere at the time of drying, in addition to normal air, an atmosphere reduced in pressure or substituted with nitrogen gas, Ar gas or the like may be used.

  As described above, the solvent is removed, and the core material fine particles coated around the core are collected by, for example, a filter unit provided in the drying chamber.

[First heat treatment step]
The recovered particles are further heated at a temperature of 450 ° C. to 1000 ° C., for example, in order to fuse the fine particles of the crystalline inorganic material shell.

As an apparatus that can be used for the first heat treatment step, a heat treatment apparatus that can withstand the fine particle fusion temperature is necessary. For example, an electric furnace equipped with a crucible can be used. At this time, when the target inorganic substance shell is made of sulfide, a reducing atmosphere, an inert gas atmosphere (which may contain a sulfur-based gas such as H ₂ S or CS ₂ ), or a vacuum atmosphere is used. When firing in an electric furnace equipped with a crucible in the atmosphere, it is desirable to fill the dummy particles made of particles having a composition close to the sulfide before firing.

  The heat treatment time can be 10 minutes to several days depending on the purpose, if the heat collected by the filter as described above is separately heat treated. Preferably, it is 20 minutes to 24 hours.

  By passing through the first heat treatment step, particles having an inorganic material temporary shell made of shell raw material fine particles attached to the surface of the core are obtained.

  The obtained material to be heat-treated may be subjected to a loosening process, a sieving process or the like as necessary.

  Note that the drying step and the first heat treatment step may be performed as the same step as long as the drying chamber used in the drying step can withstand the fine particle fusion temperature. For example, a quartz tube furnace can be used. In this case, it is preferable that the heat treatment is performed within a time period during which the atomized particles do not fall (mostly several seconds to several minutes), and the drying and the first heat treatment, that is, the fine particle fusion, are simultaneously performed. Thereby, the number of processes can be reduced. More preferably, the temperature is raised stepwise from a low temperature to a high temperature, followed by the first heat treatment after drying. Thereby, a denser inorganic substance temporary shell can be easily formed.

[Second heat treatment step]
What is formed on the surface of the particles obtained as described above is an amorphous or low crystallinity inorganic material temporary shell, and has not yet a structure capable of functioning as a core-shell particle. Therefore, this is further subjected to a second heat treatment step to crystallize or improve the crystallinity of the inorganic substance temporary shell so as to function as core-shell particles.

  When crystallization or crystallinity is improved, heat treatment is performed at a temperature of, for example, 600 ° C. to 1600 ° C., depending on the composition and crystal seed of the target crystalline inorganic substance shell.

As a heat treatment apparatus, a heat treatment apparatus capable of withstanding this temperature is required. For example, an electric furnace equipped with a crucible can be used. At this time, when the target inorganic substance shell is made of sulfide, a reducing atmosphere, an inert gas atmosphere (which may contain a sulfur-based gas such as H ₂ S or CS ₂ ), or a vacuum atmosphere is used. When firing in an electric furnace equipped with a crucible in the atmosphere, it is desirable to fill the dummy particles made of particles having a composition close to the sulfide before firing.

  The heat treatment time can be 10 minutes to several days depending on the purpose, if the heat collected by the filter as described above is separately heat treated. Preferably, it is 20 minutes to 24 hours.

  Through the second heat treatment step, core-shell particles in which a crystalline inorganic substance shell is formed on the surface of the core are obtained. The film thickness of the shell is generally in the range of 1 nm to 10 μm, preferably in the range of 10 nm to 5 μm.

  The obtained core-shell particles may be subjected to a loosening process, a sieving process, or the like, if necessary.

  If the drying chamber used in the drying step and / or the heat treatment apparatus used in the first heat treatment step can withstand the crystallization or crystallinity improvement temperature, the drying step and / or the first heat treatment step are used. The heat treatment step and the second heat treatment step may be performed by the same heat treatment apparatus. For example, an alumina tube furnace can be used. In the case where the drying process to the second heat treatment process are simultaneously performed, the heat treatment is performed within a time period in which the atomized particles do not fall (mostly several seconds to several minutes), and the drying, the first heat treatment, that is, the fine particle fusion, The second heat treatment, that is, crystallization or crystallinity improvement is preferably performed simultaneously. Thereby, the number of processes can be reduced. More preferably, the temperature is raised from a low temperature to a high temperature step by step, followed by drying, first heat treatment, and second heat treatment. Thereby, core-shell particles having a denser shell can be easily produced.

  Here, the structure at the time of using the core-shell particle obtained by the manufacturing method of the core-shell particle of this invention for an electroluminescent light emitting element is demonstrated.

A device using electroluminescent phosphor particles is actually composed of a substrate 22, a transparent electrode 24, a light emitting layer 26, an insulating layer 28, a back electrode 30, and a surface protective layer 32, such as the device 20 shown in FIG. It can be set as the structure. The production can be performed, for example, by the following method. First, a PET sheet is used as the substrate 22, and ITO (indium tin oxide) is deposited thereon to form the transparent electrode 24. Next, cyanoethyl cellulose as a dielectric binder material was mixed with N, N′-dimethylformamide as a solvent in a volume ratio of (cyanoethylcellulose) :( N, N′-dimethylformamide) = 3: 7. The electroluminescent phosphor particles obtained by the method for producing core-shell particles of the present invention are dispersed in a cyanoethyl cellulose solution. The dispersion is applied onto the transparent electrode 24 and dried to form the light emitting layer 26. Subsequently, a dispersion obtained by dispersing BaTiO ₃ particles having an average particle size of 0.2 μm in a cyanoethyl cellulose solution similar to that used for the formation of the light emitting layer 26 was applied onto the light emitting layer 26 and dried. An insulating layer 28 having a layer thickness of 5 μm is formed. Finally, aluminum is vapor-deposited on the insulating layer 28 to form the back electrode 30, and a PET sheet is laminated thereon to form the surface protective layer 32.

  By creating an electroluminescent light emitting element in this way, the electric field concentrates on the portion of the phosphor shell sandwiched between the dielectric core and the dielectric binder, and is the same as when only the same amount of phosphor particles are dispersed. Even with an applied voltage, high luminance can be achieved.

  Below, the specific example of the manufacturing method of the core-shell particle of this invention is described.

In an aqueous solution in which Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), thiourea (91.35 g), Mn (NO ₃ ) ₂ · 6H ₂ O (5.17 g), and hydroxypropylcellulose (20.00 g) are dissolved ( 2.00 L) was dispersed BaTiO ₃ particles (72.44 g) having an average particle size of 2.0 μm to obtain a starting material solution.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized with a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and volatile components are removed in a 200 ° C. drying chamber. After distilling off, the particles in which the ZnS: Mn raw material component was coated on the surface of BaTiO ₃ were collected at the filter section.

The particles were transferred to a crucible filled with ZnS dummy particles. This was put in an electric furnace and heated at 600 ° C. for 24 hours to perform a raw material decomposition treatment. Subsequently, BaTiO ₃ / ZnS: Mn core-shell particles were formed by crystallization of ZnS: Mn at 900 ° C. for 2 hours.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), tetraethyl orthosilicate (Si (OC ₂ H ₅ ) ₄ , hereinafter referred to as TEOS) (66.49 mL), Mn (CH ₃ COO) ₂ · 4H ₂ O ( 3.68 g) BaTiO ₃ particles (72.44 g) having an average particle size of 2.0 μm were dispersed in an aqueous solution (2.00 L) in which appropriate amounts of nitric acid and hydroxypropylcellulose (20.00 g) were dissolved to prepare a starting material solution.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized with a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and volatile components are removed in a 200 ° C. drying chamber. After distilling off, particles obtained by coating the surface of BaTiO ₃ with the Zn ₂ SiO ₄ : Mn raw material component were collected in the filter section.

The above particles are subjected to a raw material decomposition treatment by heating at 600 ° C. for 24 hours in the air, and then crystallization of Zn ₂ SiO ₄ : Mn is performed at 1300 ° C. for 2 hours in an Ar atmosphere. As a result, BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were formed.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

In an aqueous solution in which Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), thiourea (91.35 g), Mn (NO ₃ ) ₂ · 6H ₂ O (5.17 g), and hydroxypropylcellulose (20.00 g) are dissolved ( 2.00 L) was dispersed BaTiO ₃ particles (72.44 g) having an average particle size of 2.0 μm to obtain a starting material solution.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40L / min) was used to introduce in a quartz tube furnace that can be stepwise temperature increase to 200 ° C. to 1000 ° C., in the tubular furnace, and drying-material decomposition, ZnS in BaTiO ₃ core surface: Particles coated with the Mn temporary shell were formed and collected at the filter section.

The particles were transferred to a crucible filled with ZnS dummy particles. This was put into an electric furnace and ZnS: Mn was crystallized at 900 ° C. for 2 hours to form BaTiO ₃ / ZnS: Mn core-shell particles.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), TEOS (66.49 mL), Mn (CH ₃ COO) ₂ · 4H ₂ O (3.68 g), appropriate amounts of nitric acid, hydroxypropylcellulose (20.00 g) are dissolved In this aqueous solution (2.00 L), BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm were dispersed to obtain a starting raw material liquid.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into a quartz tube furnace that can be stepwise raised from 200 ° C. to 1000 ° C., dried and decomposed in the tube furnace, and Zn ₂ is deposited on the surface of the BaTiO ₃ core. Particles coated with a SiO ₄ : Mn temporary shell were formed and collected at the filter section.

BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were formed on the particles by crystallization of Zn ₂ SiO ₄ : Mn under an Ar atmosphere at 1300 ° C. for 2 hours.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

In an aqueous solution in which Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), thiourea (91.35 g), Mn (NO ₃ ) ₂ · 6H ₂ O (5.17 g), and hydroxypropylcellulose (20.00 g) are dissolved ( 2.00 L) was dispersed BaTiO ₃ particles (72.44 g) having an average particle size of 2.0 μm to obtain a starting material solution.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min), is introduced into an alumina tube furnace that can be heated stepwise from 200 ° C. to 1200 ° C., and drying, raw material decomposition, crystallization of ZnS: Mn is performed in the tube furnace, BaTiO ₃ / ZnS: Mn core-shell particles were collected at the filter section.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

Zn (NO ₃ ) ₂ · 6H ₂ O (178.49 g), TEOS (66.49 mL), Mn (CH ₃ COO) ₂ · 4H ₂ O (3.68 g), appropriate amounts of nitric acid, hydroxypropylcellulose (20.00 g) are dissolved In this aqueous solution (2.00 L), BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm were dispersed to obtain a starting raw material liquid.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into an alumina tube furnace that can be stepwise heated to 200 ° C. to 1400 ° C., and drying, raw material decomposition, crystallization of Zn ₂ SiO ₄ : Mn in the tube furnace Then, BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were collected at the filter part.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, ZnS: Mn (58.47 g) fine particles having an average particle diameter of 4 nm and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm are dispersed. The starting material solution was used.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized with a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and volatile components are removed in a 200 ° C. drying chamber. After distilling off, particles obtained by coating the surface of BaTiO ₃ with ZnS: Mn particles were collected at the filter section.

The particles were transferred to a crucible filled with ZnS dummy particles. This was put in an electric furnace and heated under conditions of 600 ° C. for 24 hours to carry out fine particle fusion treatment, and then transferred to a crucible filled with ZnS dummy particles. This was put into an electric furnace, and the crystallinity of ZnS: Mn was improved at 900 ° C. for 2 hours to form BaTiO ₃ / ZnS: Mn core-shell particles.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, Zn ₂ SiO ₄ : Mn fine particles (66.86 g) having an average particle diameter of 50 nm, and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm. Dispersed to obtain a starting material liquid.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized with a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and volatile components are removed in a 200 ° C. drying chamber. After distilling off, particles in which Zn ₂ SiO ₄ : Mn particles were coated on the surface of BaTiO ₃ were collected in the filter section.

The above particles are heated in the atmosphere at 600 ° C. for 24 hours, and then subjected to a fine particle fusion treatment, and then in an Ar atmosphere at 1300 ° C. for 2 hours, Zn ₂ SiO ₄ : Mn has excellent crystallinity. By doing so, BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were formed.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, ZnS: Mn fine particles (58.47 g) having an average particle diameter of 4 nm and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm are dispersed. A starting material solution was obtained.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into a quartz tube furnace that can be raised in steps from 200 ° C. to 1000 ° C., dried and fused in a fine particle, and ZnS is formed on the surface of the BaTiO ₃ core. : Particles coated with a Mn temporary shell were formed and collected at the filter section.

The particles were transferred to a crucible filled with ZnS dummy particles. This was put into an electric furnace and ZnS: Mn crystallinity was improved under the conditions of 900 ° C. for 2 hours to form BaTiO ₃ / ZnS: Mn core-shell particles.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, Zn ₂ SiO ₄ : Mn fine particles (66.86 g) having an average particle diameter of 50 nm, and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm. Dispersed to obtain a starting material liquid.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into a quartz tube furnace that can be stepped up to 200 ° C. to 1000 ° C., dried and fused in a fine particle, and Zn on the surface of the BaTiO ₃ core. Particles coated with ₂ SiO ₄ : Mn temporary shell were formed and collected in the filter section.

BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were formed by improving the crystallinity of Zn ₂ SiO ₄ : Mn on the particles at 1300 ° C. for 2 hours.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, ZnS: Mn fine particles (58.47 g) having an average particle diameter of 4 nm and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm are dispersed. A starting material solution was obtained.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into an alumina tube furnace that can be raised in steps from 200 ° C. to 1200 ° C., and drying, fine particle fusion, and ZnS: Mn crystallinity improvement in the tube furnace Then, BaTiO ₃ / ZnS: Mn core-shell particles were collected at the filter part.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 585 nm was observed.

In an aqueous solution (2.00 L) in which hydroxypropylcellulose (20.00 g) is dissolved, Zn ₂ SiO ₄ : Mn fine particles (66.86 g) having an average particle diameter of 50 nm, and BaTiO ₃ particles (72.44 g) having an average particle diameter of 2.0 μm. Dispersed to obtain a starting material liquid.

The raw material liquid is introduced into the atomization chamber using a stock solution injection pump (20 mL / min), atomized by a two-fluid spray nozzle (manufactured by Spraying Nozzle Co., Ltd.), and the resulting mist droplets are added to a carrier gas (N ₂ , 40 L / min) is introduced into an alumina tube furnace that can be stepwise raised from 200 ° C. to 1400 ° C., and in this tube furnace, drying, fine particle fusion, Zn ₂ SiO ₄ : Mn crystal The properties were improved, and BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were collected at the filter section.

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was prepared using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed.

  As mentioned above, although embodiment of this invention was described in detail, it cannot be overemphasized that these embodiment is only an illustration and the technical scope of this invention should be defined only by a claim. Yes.

Illustration of two fluid spray Diagram of quartz tube furnace capable of stepwise temperature rise Diagram of alumina tube furnace capable of stepwise temperature rise Sectional drawing which shows the example of the actual structure of the 1st electroluminescent element which concerns on this invention Sectional drawing which shows the basic structure of the conventional dispersion-type electroluminescent element Sectional drawing which shows the basic structure of the conventional thin film type electroluminescent element

Explanation of symbols

20, 60, 80 Electroluminescent element 22, 62, 82 Substrate 24, 64, 84 Transparent electrode 26, 66, 88 Light emitting layer 66a Phosphor particle 66b Binder 28, 68, 86a, 86b Insulating layer 30, 70, 90 Back electrode 32 Surface protective layer 100 Two-fluid spray 102 Liquid supply unit 104 Gas supply unit 120 Quartz tubular furnace 122 Quartz heating passage 140 Alumina tubular furnace 142 Alumina heating passage 124, 144 Raw material supply ports 126a, 126b, 146a, 146b, 146c Heating device 128a, 128b, 148a, 148b, 148c Heating area 130, 150 Exhaust port 132, 152 Cartridge filter

Claims (12)

A method for producing core-shell particles comprising at least a core and a crystalline inorganic substance shell,
An atomization step of atomizing a dispersion in which the core is dispersed in a raw material solution of the crystalline inorganic substance shell;
A drying step of coating the raw material of the crystalline inorganic substance shell on the surface of the core by drying the atomized dispersion;
A first heat treatment step of forming an inorganic material temporary shell on the surface of the core by performing a heat treatment at a temperature equal to or higher than a decomposition temperature of the raw material of the crystalline inorganic material shell;
A second heat treatment step of forming the crystalline inorganic material shell on the surface of the core by performing a heat treatment at a temperature at which the inorganic material temporary shell crystallizes;
A method for producing core-shell particles, comprising:   The method for producing core-shell particles according to claim 1, wherein the drying step and the first heat treatment step are performed by the same heat treatment apparatus.   The method for producing core-shell particles according to claim 1, wherein the drying step and / or the first heat treatment step and the second heat treatment step are performed by the same heat treatment apparatus. A method for producing core-shell particles comprising at least a core and a crystalline inorganic substance shell,
An atomization step of atomizing a dispersion in which fine particles sufficiently smaller than the core having the same constituent metal elements as the core and the crystalline inorganic substance shell are dispersed;
Drying the atomized dispersion to coat the surface of the core with the fine particles of the crystalline inorganic material shell; and
A first heat treatment step of forming an inorganic substance temporary shell on the surface of the core by performing a heat treatment at a temperature at which the fine particles of the crystalline inorganic substance shell are fused together;
A second heat treatment step of forming the crystalline inorganic material shell on the surface of the core by performing a heat treatment at a temperature at which the inorganic material temporary shell crystallizes;
A method for producing core-shell particles, comprising:   The method for producing core-shell particles according to claim 4, wherein the drying step and the first heat treatment step are performed by the same heat treatment apparatus.   The method for producing core-shell particles according to claim 4, wherein the drying step and / or the first heat treatment step and the second heat treatment step are performed by the same heat treatment apparatus.   The method for producing core-shell particles according to any one of claims 1 to 6, wherein the crystalline inorganic substance shell is a phosphor.   The method for producing core-shell particles according to claim 7, wherein the phosphor is an electroluminescence phosphor.   The method for producing core-shell particles according to claim 8, wherein the electroluminescent phosphor is ZnS: Mn. The method for producing core-shell particles according to claim 8, wherein the electroluminescent phosphor is Zn ₂ SiO ₄ : Mn.   The method for producing core-shell particles according to any one of claims 1 to 10, wherein the core is a dielectric having a large dielectric constant. The method of manufacturing core-shell particles according to claim 11, wherein the dielectric is BaTiO ₃ .

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