JP2006232920A - 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 core/hell particles is provided by (1) mixing the core with fine particles having the same constitutional metal element with the objective crystalline inorganic substance shell and being sufficiently smaller than the core, (2) attaching at least ≥1 layer of the fine particles on the surface of the core by using a mechanochemical reaction to form a temporary shell consisting of aggregates of the fine particles (3) forming the crystalline inorganic substance shell on the surface of the core by heat-treating at a temperature at which the temporary shell performs a solid phase reaction. <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.

  In the dispersion type electroluminescent device, typically, like the device 60 shown in FIG. 3, a transparent electrode 64 is formed on a transparent substrate 62 such as glass or a polyethylene terephthalate (PET) sheet by applying a transparent conductive film. In addition, a light emitting layer 66 in which phosphor particles 66a are freely dispersed in a dielectric binder 66b, an insulating layer 68, and a back electrode 70 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. In addition, ZnS: Cu, Al (green) or ZnS: Cu, Cl, Mn (orange yellow) depending on the desired emission color. ) 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. In addition, it is considered that the particle diameter of about 20 μm is optimal for the phosphor particles of the dispersive 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. 4, 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. 4 is drawn to a thickness substantially the same as that of the element 60 of FIG. 3 for 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. 4 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. 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 for the body covering layer has also been proposed. 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 luminous efficiency in the device and / or to start light emission at a low applied voltage, it is necessary to efficiently apply a voltage applied to the device to the phosphor particles in the light emitting layer. As a means for this, for example, in the electroluminescence element described in Patent Document 2, a dielectric having a high dielectric constant such as BaTiO3 is used as a binder in the light emitting layer, and phosphor particles are dispersed therein. .

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, as one example, a method for producing ceramic particles for electronic parts in which a plurality of elements are supported in layers on the surface of inorganic compound powder particles. A material in which a plurality of elements are supported in a layer form by a chemical reaction is disclosed.
International Publication No. 02/080626 Pamphlet Japanese Patent Publication No. 2000-195664 Japanese Patent Publication No. 2002-180041 Japanese Patent Publication No. Hei 10-1558059 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, the relationship between the shape and composition of the coating layer raw material powder and the generated coating layer is unclear, and the metal elements constituting the coating layer are diffused into the core particles by heat treatment. In the end, the coating layer is not formed to express the function.

  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 adds a shell raw material to the core surface using a mechanochemical reaction, and then adds a step of performing a heat treatment at a temperature at which the shell raw material is sintered. It has been found that core-shell particles having a composition and a sufficiently thick shell can be produced, and the present invention has been achieved.

The method for producing the first core-shell particles according to the present invention includes:
(1) a step of mixing a core and fine particles having the same constituent metal elements as the target crystalline inorganic substance shell and sufficiently smaller than the core;
(2) using a mechanochemical reaction to attach at least one layer of the fine particles to the core surface to form a temporary shell made of an aggregate of the fine particles;
(3) forming the crystalline inorganic substance shell on the surface of the core by performing a heat treatment at a temperature at which the temporary shell undergoes a solid-phase reaction;
It is characterized by having.

Moreover, the method for producing the second core-shell particles according to the present invention includes:
(1) a step of mixing a core and two or more kinds of fine particles sufficiently smaller than the core blended so as to have the same constituent metal element as a target crystalline inorganic substance shell;
(2) Using a mechanochemical reaction, at least one layer of the two or more types of fine particles is uniformly dispersed on the core surface, and the aggregate of the two or more types of fine particles and / or a compound thereof is used. Forming a temporary shell comprising:
(3) forming the crystalline inorganic substance shell on the surface of the core by performing a heat treatment at a temperature at which the temporary shell undergoes a solid-phase reaction;
It is characterized by having.

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”.

  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. It is a thing. 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 fine particles and the like are defined by the diameter.

  In the present invention, the “mechanochemical reaction” means that the mechanical energy is converted into chemical energy by giving large mechanical energy to the particle through collision between the particles, and the particle is reacted.

  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, a step of forming at least one layer of the fine particles on the core surface using a mechanochemical reaction to form a temporary shell made of the fine particle aggregate. Then, since the heat treatment is performed at a temperature at which the temporary shell undergoes a solid phase reaction, the shell composition can be easily controlled by changing the shell raw material, and core-shell particles having a shell having a desired composition can be obtained. Further, core-shell particles having a thick shell can be obtained by the action of a mechanochemical reaction.

  In the second core-shell particle production method of the present invention, at least one or more layers are adhered to the core surface in a state where the two or more kinds of fine particles are uniformly dispersed using a mechanochemical reaction, and the two or more kinds Since the heat treatment is performed at a temperature at which the temporary shell undergoes a solid-phase reaction through a step of forming a temporary shell made of an aggregate of the fine particles and / or the compound thereof, the amount of the two or more kinds of materials The core-shell particles having a desired composition can be easily obtained. Further, core-shell particles having a thick shell can be obtained by the action of a mechanochemical reaction.

  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 production methods of the present invention, when the core is made of a dielectric having a large dielectric constant, the core-shell particle that can be used for an electroluminescence element or the like is obtained while exhibiting the same effect as described above. It 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.

[Mixing process of core and shell fine particles]
Examples of the shell material that can be used in the present invention include those that adhere to the core by a mechanochemical method and that are inorganic substances that exhibit crystallinity by heat treatment. In particular, for an electroluminescence light emitting device, a phosphor containing copper such as ZnS: Cu, Cl used in a conventional dispersion type electroluminescence device may be used, and conventionally, like ZnS: Mn, You may use the fluorescent substance containing the luminescent center excited with the hot electron used with the thin film type electroluminescent element. 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 size ratio and weight ratio between the core and the shell raw material fine particles for mixing may be appropriately determined according to the use of the core-shell particles, but in the mechanochemical reaction, most (99%) of the shell raw material is attached to the core. Therefore, it may be determined by calculating back from the size of the core-shell particles to be finally obtained and the shell film thickness. 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. In the case of an electroluminescent phosphor used for an electroluminescent light emitting device, 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.

  For mixing the core and shell raw material fine particles, a known means such as an agate mortar can be used.

[Mechanochemical reaction process]
The material mixed as described above is subjected to a mechanochemical reaction by means of a planetary ball mill, a lycais machine or the like.

  Thereby, what the temporary shell which consists of shell raw materials adhered to the surface of a core is obtained.

  The planetary ball mill will be described with reference to FIG. In the planetary ball mill 10, the reaction vessel 12 revolves on the revolving table 14 and performs a revolving motion opposite to the revolving direction. In addition to the raw material 16 to be reacted, pulverized balls 18 are placed in the reaction vessel 12. The pulverized ball 18 is vigorously moved under the influence of both the revolving motion and the rotating motion. At this time, the raw material 16 to be reacted is sandwiched between the pulverized ball 18 and the reaction vessel 12, and receives kinetic energy stronger than that of a normal ball mill. This kinetic energy is converted into chemical energy, and the mechanochemical reaction proceeds. It will be.

[Heat treatment process]
In the present invention, it is further desirable to heat-treat the above-described core having a temporary shell made of a shell material attached thereto.

The particles coated on the surface are filled in a heat-resistant container such as a quartz boat, an alumina crucible, or a quartz crucible, and then heat-treated in a core of an electric furnace. The heat treatment temperature varies depending on the compound type of the target inorganic substance shell, but is generally in the range of 600 ° C. to 1600 ° C., preferably in the range of 700 ° C. to 1300 ° C. The heat treatment time varies depending on the compound type and amount of the target inorganic substance shell, but is generally in the range of 10 minutes to 100 hours. The heat treatment atmosphere also varies depending on the type and amount of the surface particles of the compound seed of the target inorganic substance shell. In general, when the inorganic material shell is an oxide, a neutral atmosphere such as a reducing atmosphere (N ₂ / H ₂ , NH ₃ gas, etc.) such as an inert gas atmosphere containing a small amount of hydrogen, or an inert gas atmosphere An atmosphere (He, Ne, Ar, N ₂ or the like), an inert gas atmosphere containing a small amount of oxygen, an oxidizing atmosphere such as air or oxygen (N ₂ / O ₂ or the like), or a vacuum atmosphere is used. In the case of nitride or oxynitride, a neutral atmosphere, a reducing atmosphere, a weak oxidizing atmosphere, or a vacuum atmosphere is used. Reheating treatment may be performed by changing these heat treatment conditions.

Further, 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 heat-treating with a crucible inside, it is desirable to heat-treat after filling dummy particles made of particles having a composition close to the sulfide.

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

  By subjecting the core surface to which the temporary shell is attached to the heat treatment step, the temporary shell can be subjected to a solid phase reaction to be single-phased.

  In this way, core-shell particles in which a shell made of a crystalline inorganic substance is formed on the core surface 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.

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

[Mixing process of core and shell fine particles]
As the shell raw material fine particles, two or more types of fine particles that are sufficiently smaller than the core blended so as to have the same constituent metal elements as the target crystalline inorganic substance shell are prepared. For example, when the shell of the core-shell particle after production is made of a double oxide, an oxide of each element of the double oxide or a precursor thereof may be prepared as two or more kinds of fine particles.

  Also in the second method for producing core-shell particles of the present invention, the size ratio and weight ratio of the core and shell in mixing may be appropriately determined according to the use of the core-shell particles, and the size of the core-shell particles to be finally obtained Now, it may be determined by calculating back from the shell film thickness.

  Other points are the same as in the method for producing the first core-shell particle of the present invention.

[Mechanochemical reaction process]
The material mixed as described above is subjected to a mechanochemical reaction by means of a planetary ball mill, a lycais machine or the like. At this time, due to the action of the mechanochemical reaction, the fine particles, which are shell raw materials, adhere to the core by chemical bonding to form a temporary shell. At this time, the fine particles may partially react to form a compound and then adhere to the core by chemical bonding.

  Other points are the same as in the method for producing the first core-shell particle of the present invention.

[Heat treatment process]
It can carry out similarly to the manufacturing method of the 1st core shell particle | grains of this invention.

  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.

An element using electroluminescent phosphor particles has a structure 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 element 20 shown in FIG. be able to. 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 (cyanoethyl cellulose) :( 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.

ZnS: Mn fine particles (particle size 4 nm, 20 g) and BaTiO ₃ core particles (particle size 2.0 μm, 25 g) are mixed in a planetary ball mill to form an aggregate of ZnS: Mn nanoparticles on BaTiO _3. Particles having a temporary shell were formed.

BaTiO ₃ / ZnS: Mn core-shell particles were formed by subjecting the particles to a heat treatment of ZnS: Mn at 900 ° C. for 2 hours in a crucible filled with ZnS dummy 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 ₂ SiO ₄ : Mn nanoparticles (particle size 50 nm, 25 g) and BaTiO ₃ core particles (particle size 2.0 μm, 25 g) were mixed in a planetary ball mill to form Zn ₂ SiO ₄ : Mn on BaTiO _3. Particles having a temporary shell made of an aggregate of fine particles were formed.

BaTiO ₃ / Zn ₂ SiO ₄ : Mn core-shell particles were formed by subjecting the particles to a heat treatment of Zn ₂ SiO ₄ : Mn under conditions of 1300 ° C. and 2 hours in an Ar atmosphere.

  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.

ZnO fine particles (particle size 40 nm, 16.3 g), SiO ₂ fine particles (particle size 50 nm, 6.0 g), Mn ₃ O ₄ fine particles (particle size 80 nm, 0.5 g), BaTiO ₃ core particles (particle size 2.0 μm, 22.3 g) Were mixed in a planetary ball mill to form particles having a temporary shell made of an aggregate of ZnO fine particles, SiO ₂ fine particles, and Mn ₃ O ₄ fine particles on BaTiO ₃ .

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

  The formed particles had a crystalline shell with an average film thickness of 200 nm. Moreover, when an electroluminescence element was produced using the core-shell particles, an electroluminescence emission spectrum centered on 525 nm was observed, and it was shown that the phosphor composition was uniform.

  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.

(a) Top view of planetary ball mill (b) Overview of planetary ball mill 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

DESCRIPTION OF SYMBOLS 10 Planetary ball mill 12 Reaction container 14 Revolving stand 18 Grinding ball 20, 60, 80 Electroluminescence 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

Claims (8)

A method for producing core-shell particles comprising at least a core and a crystalline inorganic substance shell,
Mixing the core and fine particles having the same constituent metal elements as the crystalline inorganic substance shell and sufficiently smaller than the core;
Using a mechanochemical reaction to attach at least one layer of the fine particles to the core surface to form a temporary shell made of an aggregate of the fine particles;
Forming the crystalline inorganic substance shell on the surface of the core by performing a heat treatment at a temperature at which the temporary shell undergoes a solid phase reaction;
A method for producing core-shell particles, comprising: A method for producing core-shell particles comprising at least a core and a crystalline inorganic substance shell,
Mixing the core and two or more kinds of fine particles sufficiently smaller than the core blended so as to have the same constituent metal elements as the crystalline inorganic substance shell;
Using a mechanochemical reaction, at least one or more layers are adhered to the core surface in a state where the two or more kinds of fine particles are uniformly dispersed to form a temporary shell comprising the aggregate of the two or more kinds of fine particles and / or a compound thereof. Forming a step;
Forming the crystalline inorganic substance shell on the surface of the core by performing a heat treatment at a temperature at which the temporary shell undergoes a solid phase reaction;
A method for producing core-shell particles, comprising:   The method for producing core-shell particles according to claim 1 or 2, wherein the crystalline inorganic substance shell is a phosphor.   The method for producing core-shell particles according to claim 3, wherein the phosphor is an electroluminescence phosphor.   The method for producing core-shell particles according to claim 4, wherein the electroluminescent phosphor is ZnS: Mn. The method for producing core-shell particles according to claim 4, 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 6, wherein the core is a dielectric having a high dielectric constant. The method of manufacturing core-shell particles according to claim 7, wherein the dielectric is BaTiO ₃ .

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