JP2006008806A - Phosphor precursor, electroluminescent phosphor, their production methods and dispersed electroluminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient method for obtaining an EL phosphor particulate with a narrow particle size distribution, and a dispersed EL element which emits highly uniform high-intensity light using the EL phosphor particulate obtained through the method. <P>SOLUTION: The zinc sulfate phosphor precursor comprises secondary particles which comprises an aggregation of primary particles with a median particle size of 1-20 nm, has a median particle size of 0.05-5.0 μm and has at least one chosen from the group consisting of Cu, Mn, Ag, Au and rare-earth elements. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electroluminescent (EL) phosphor containing zinc sulfide as a base material and an activator and a coactivator as the center of light emission, a method for producing the same, and an electro having a light emitting layer in which the phosphor is dispersedly applied. The present invention relates to a luminescence element.

  In the conventional method for producing a zinc sulfide (ZnS) phosphor, as a method of reducing the particle size of the EL phosphor particles, the amount of alkali metal halide or alkaline earth metal halide flux added can be reduced, It was adjusted by lowering the firing temperature. However, this method has a problem that the crystallinity of the obtained phosphor decreases due to a decrease in the amount of flux added or a decrease in the firing temperature, and an activator such as copper ions cannot be uniformly introduced into the matrix. The particle size adjustment range was limited.

  Further, in the conventional manufacturing method, since several μm of precursor particles having a crystallite of about 20 nm are used as a ZnS raw material, the surface activity of the precursor particles is low, and high temperature firing is necessary for crystal growth. It has become. Furthermore, since the activator is added in a solid phase at this time, high temperature firing is similarly required in order to uniformly introduce it into the mother body. Such high-temperature firing consumes a large amount of energy in the production of the phosphor, and causes a problem of increasing point defects such as zinc vacancies and sulfur vacancies in the phosphor.

  As a method different from the conventional production method, a production method using a uniform precipitation method described in Patent Document 1 is disclosed. In this method, the crystallinity of the obtained precursor is increased, and the precursor particles are not crystal-grown in the firing step. In such a method, the frequency of crystal growth and recombination in the firing step is expected to be low, and there is a problem that the density of stacking faults generated with the growth does not reach the amount required for the EL phosphor. .

As another production method, a production method using a spray pyrolysis method described in Patent Document 2 is disclosed. In this method, a method for producing a sulfide with controlled particle size is shown, but introduction of an activator, primary particles (crystallites), re-baking of recovered particles, etc. are not considered. It is not enough to apply to.
JP-A-53-82682 Japanese Patent Laid-Open No. 7-61816

  An object of the present invention is to obtain a fine EL phosphor having a narrow particle size distribution with high efficiency. Another object of the present invention is to obtain a light-emitting dispersed EL element having high brightness and high uniformity using the fine particle EL phosphor.

(1) A primary particle having a central particle size in the range of 1 to 20 nm is aggregated, a central particle size is in a range of 0.05 to 5.0 μm, and is made of Cu, Mn, Ag, Au, and a rare earth element. A zinc sulfide phosphor precursor comprising secondary particles having at least one selected from the group.
(2) General formula; ZnS: M, X
(Wherein M represents at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements, and X represents at least one element selected from the group consisting of halogen elements and aluminum.)
The center particle size is in the range of 0.1 to 15 μm, and is obtained by mixing and firing at least the precursor described in (1) and a compound containing an element represented by X. A characteristic electroluminescent phosphor.
(3) The phosphor has a planar stacking fault, and particles having a stacking fault of 10 layers or more with an interplanar spacing of the stacking fault of 5 nm or less are 30% or more of the total phosphor particles. The electroluminescent phosphor according to item (2), which is present.
(4) The electroluminescent phosphor as described in (2) or (3), wherein the coefficient of variation in particle size is less than 35%.

(5) A primary particle having a center particle size in the range of 1 to 20 nm is aggregated, a center particle size is in a range of 0.05 to 5.0 μm, and is made of Cu, Mn, Ag, Au, and a rare earth element. A method for producing a precursor of a zinc sulfide based phosphor comprising secondary particles having at least one selected from the group,
Preparing a solution in which at least a zinc compound and a compound containing at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements are dissolved; and adding thioacetamide to the solution; Heating the solution to a temperature in the range of 60 to 100 ° C. to hydrolyze thioacetamide to obtain a precipitate of zinc sulfide containing at least one of Cu, Mn, Ag, Au, or a rare earth element; A method for producing a precursor of a zinc sulfide-based phosphor.
(6) The primary particles having a central particle size in the range of 1 to 20 nm are aggregated, the central particle size is in the range of 0.05 to 5.0 μm, and is made of Cu, Mn, Ag, Au, and a rare earth element. A method for producing a precursor of a zinc sulfide based phosphor comprising secondary particles having at least one selected from the group,
Preparing a solution in which at least a zinc compound, a compound containing at least one element selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements, and thioacetamide, thiourea, and derivatives thereof are dissolved; The solution is atomized as fine droplets and introduced into a carrier gas, and the fine droplets introduced into the carrier gas are thermally decomposed by heating to a temperature in the range of 500 to 1000 ° C. to obtain Cu, Mn And a step of obtaining zinc sulfide particles containing at least one of Ag, Au, or a rare earth element.

(7) General formula; ZnS: M, X
(Wherein M represents at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements, and X represents at least one element selected from the group consisting of halogen elements and aluminum.)
A method for producing an electroluminescent phosphor represented by:
A group consisting of a precursor of a zinc sulfide-based phosphor containing at least one of Cu, Mn, Ag, Au, or a rare earth element obtained by the method described in (5) or (6), a halogen element, and aluminum A step of obtaining a mixture by mixing a compound containing at least one element selected from the above, and a step of obtaining phosphor particles by firing the mixture at a temperature in the range of 700 to 1200 ° C. A method for producing an electroluminescent phosphor.
(8) After the firing step, the method includes a step of applying stress to such an extent that the phosphor particles are not crushed and a step of re-baking the stressed phosphor particles at 500 to 1000 ° C. (7 The method for producing the electroluminescent phosphor according to the item).
(9) An electroluminescent element comprising the electroluminescent phosphor according to any one of (2) to (4) in a light emitting layer.
(10) The electroluminescent element as described in (9), wherein the light emitting layer has a thickness of 0.5 to 30 μm.

  The EL phosphor of the present invention exhibits high-efficiency EL emission even though it is a fine particle, and since the particle size distribution is narrow, the dispersibility is good and a uniform light-emitting layer can be formed. In addition, the EL phosphor production method of the present invention can produce fine EL phosphors with high yield and good reproducibility, and can lower the firing temperature, so that the energy consumption associated with the production is small. The impact on the global environment is small. The dispersion type EL element using this EL phosphor exhibits high luminance because the light emitting layer can be made thin. Furthermore, dispersion type EL elements using EL phosphors with fine particles and a narrow particle size distribution have dramatically improved light emission roughness (granularity), making them ideal for high-quality transmission photography and inkjet transmission illumination applications. is there.

  Hereinafter, the precursor of the EL phosphor, the EL phosphor, the production method thereof, and the EL element of the present invention will be described in detail.

[EL phosphor precursor]
In the present invention, the zinc sulfide-based phosphor precursor includes particles (secondary particles) in which particles (primary particles) having a central particle size of 1 to 20 nm are aggregated, and the particles do not contain halogen elements or aluminum. This means a group of particles having 100 or more zinc matrix particles.
The precursor of the ZnS-based EL phosphor of the present invention preferably has a primary particle having a center particle size in the range of 1 to 20 nm in order to obtain surface activity necessary to keep the firing temperature low. The range of 15 nm is more preferable, and the range of 1 to 10 nm is more preferable. Furthermore, in order to make the coefficient of variation of the particle size after firing less than 35%, it is preferable to use secondary particles in which the primary particles are aggregated, and the center particle size of the secondary particles is 0.05 to 5. It is preferably in the range of 0 μm, more preferably in the range of 0.1 to 2.0 μm, and further preferably in the range of 0.2 to 1.0 μm. This is because if a nano-sized precursor is used as it is as a firing material, the surface activity and cohesive force are too strong to make uniform sintering difficult, and the particle size distribution of the resulting phosphor becomes wide. is there. By using the secondary particles in which the primary particles are aggregated, the surface activity and the cohesive force can be adjusted appropriately, the handling characteristics of the particles are improved, and workability such as mixing and filling is also improved.
It is preferable that the secondary particles contain an element that becomes an activator of the EL phosphor. The activator element is at least one element selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements. Among these, Cu and Mn are preferably used. The activator element is preferably contained uniformly on the surface of the primary particle or the surface of the secondary particle, and most preferably contained uniformly within the primary particle. This is because the homogenization by the diffusion of the activator in the baking process becomes easier.

The precursor of the ZnS-based EL phosphor of the present invention can be produced by a uniform precipitation method utilizing hydrolysis of thioacetamide (hereinafter abbreviated as TA). In the ZnS phosphor precursor synthesis by the uniform precipitation method, a reaction mother liquor obtained by dissolving a water-soluble salt such as zinc nitrate, halide, acetate or sulfate in water can be used. Among these, it is more preferable to use zinc nitrate capable of obtaining spherical aggregates by uniform precipitation. In the reaction mother liquor, Cu, Mn, Ag, Au, or a rare earth element water-soluble salt as an activator is added. The amount of these activators to be added varies depending on the added elements, but is preferably about 5 × 10 ^{−5 to} 5 × 10 ⁻³ mol in the case of Cu with respect to 1 mol of ZnS uniformly precipitated. In this case, a range of about 10 ^{−3 to} 5 × 10 ⁻¹ is a preferable range. In this case, the salt concentration is preferably 0.01 M or more in consideration of the yield, and the saturation concentration of the salt to be used can be used. TA that acts as a precipitating agent may be added in a stoichiometric amount or more with respect to zinc, but in order to increase the reaction rate and yield, the range of 2 to 10 times the amount of zinc is preferable. A range of ˜4 times is more preferable. Furthermore, since it is preferable that H ⁺ is present in the reaction mother liquor to promote the initial reaction, the pH is preferably adjusted to a range of 1 to 4. The pH can be adjusted by adding an acid, but nitric acid, hydrochloric acid, acetic acid, etc. can be used, and it is preferable to use the same anion as the zinc salt dissolved in the reaction mother liquor.

  The homogeneous precipitation reaction is initiated by adding TA to an aqueous solution in which the salt is dissolved. At this time, TA may be added as a solid or an aqueous solution. When adding with an aqueous solution, it is preferable to use a syringe pump or the like with high addition accuracy. The reaction mother liquor is preferably stirred so that the precipitate flows uniformly in the solution. Since hydrolysis of TA is started when the temperature of the aqueous solution is 60 ° C. or higher, the reaction mother liquor is preferably kept in the range of 60 to 100 ° C., and in the range of 70 to 90 ° C. in terms of reaction rate and controllability. More preferred. TA may be added to a reaction mother liquor that has been previously added to a reaction mother liquor at 60 ° C. or lower, or may be added to a reaction mother liquor that has been previously heated to 60 ° C. or higher. After adding TA, it is preferable to hold the temperature until the reaction is completely completed. This is because the activator is very small relative to zinc, so that co-precipitation cannot occur. The completion of the reaction is determined by simultaneously detecting the zinc concentration, or the reaction is terminated by taking a sufficient reaction time. The obtained precursor precipitate is sufficiently washed with water and dried so that no by-product remains on the particle surface.

  Furthermore, the precursor can also be produced using a spray pyrolysis method. In the spray pyrolysis method, the phosphor raw material solution is made into fine droplets using an atomizer, and the phosphor precursor is obtained by condensation within the droplets, chemical reaction, or chemical reaction with the ambient gas around the droplets. It is a method of synthesizing the body. As the raw material solution, a solution obtained by dissolving a water-soluble salt such as zinc nitrate, halide, acetate or sulfate in water can be used. To this solution, a water-soluble salt of Cu, Mn, Ag, Au or a rare earth element as an activator and TA, thiourea and their derivatives as a sulfur supply source are added. Examples of the thiourea derivative include N-methylthiourea, N-ethylthiourea, N, N-dimethylthiourea, N, N-diethylthiourea, N-allylthiourea and the like. The concentration of the solution can be used up to a saturated concentration, but is preferably in the range of 0.01 to 5.0M, more preferably in the range of 0.1 to 1.0M in terms of yield and particle size obtained. Although a sulfur supply source should just be more than the stoichiometric amount with respect to zinc, 2-10 times amount is more preferable. This is because the generation efficiency of sulfides is reduced at 2 times or less, and the generation of toxic gas becomes remarkable at 10 times or more. The appropriate amount of activator added is the same as in the uniform precipitation method.

  As an atomizer for generating micro droplets, it is preferable to use a two-fluid nozzle, an ultrasonic atomizer, or an electrostatic atomizer, and an ultrasonic atomizer is more preferable in terms of adjusting the droplet size. Fine droplets generated by the atomizer are introduced into an electric furnace or the like with a carrier gas. As the carrier gas, an inert gas such as nitrogen or argon, or a sulfurized gas such as hydrogen sulfide or carbon disulfide can be used. Carrier gas containing fine droplets is introduced into a quartz tube or the like heated in an electric furnace to dehydrate and condense, and ZnS containing an activator is obtained by a thermal decomposition reaction. The temperature of the electric furnace is preferably in the range of 500 to 1000 ° C, more preferably in the range of 600 to 800 ° C. This is because the thermal decomposition reaction is not sufficiently performed at 500 ° C. or lower, and sulfide decomposition or oxide generation occurs at 1000 ° C. or higher. The residence time of the fine droplets in the electric furnace is preferably in the range of 0.5 seconds to 10 minutes, more preferably 10 seconds to 1 minute. This is because the thermal decomposition reaction is not sufficiently performed for 0.5 seconds or less, and the flow rate of the carrier gas is too low for 10 minutes or more to carry the droplets or the generated precursor. The produced precursor particles are finally collected by a filter.

[EL phosphor]
The EL phosphor of the present invention is represented by the general formula; ZnS: M, X. In the formula, M represents at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements, and X represents at least one element selected from the group consisting of halogen elements and aluminum. M is preferably Cu or Mn, and X is preferably Cl or Al.
In the EL phosphor particles of the present invention, the center particle size is preferably in the range of 0.1 to 15 μm and more preferably 10 μm or less in order to reduce the thickness of the light emitting layer and increase the electric field strength. Since the inside of the particle has a higher EL emission efficiency when it has a structure with many planar stacking faults, the particles having stacking faults of 10 or more layers with a plane spacing of 5 nm or less are the total fluorescence. Preferably, 30% or more of the body particles are present, more preferably 50% or more, and even more preferably 70% or more.

  The EL phosphor of the present invention is a group of zinc sulfide particles for EL having a narrow particle size distribution and a smaller average particle size than conventional particles. In the present invention, the particle size distribution is preferably less than 35%, more preferably 30% or less, even more preferably, with a coefficient of variation (standard deviation of particle size distribution ÷ average particle size × 100%) measured with 100 or more particles. Is 25% or less. Each particle size is expressed in terms of its diameter by converting the volume into a sphere. The particle size may be measured by taking a photograph of the individual particle, the distribution may be measured optically, or the distribution may be determined from the sedimentation velocity.

  The ZnS EL phosphor of the present invention can be produced by firing the precursor. Calcination can be performed by a solid phase reaction. First, a precursor containing an activator, a fluxing agent such as an alkali metal halide or an alkaline earth metal halide that also serves as a supply source of a halogen coactivator, and an Al compound as necessary are mixed. This mixing may be dry mixing using a mortar or the like, or may be further uniformly mixed by adding water once and drying as a suspension. As the flux, it is particularly preferable to use chloride. Examples of the compound include sodium chloride, magnesium chloride, strontium chloride, barium chloride, ammonium chloride and the like. The addition amount of the flux is preferably in the range of 1 to 90% by mass, and more preferably in the range of 10 to 60% by mass. If the amount of the flux is too small, crystal growth may not proceed sufficiently, and if the amount is too large, the particle size becomes too large. The mixture is filled in an alumina crucible and is preferably fired at a firing temperature in the range of 700 to 1200 ° C. The firing temperature is preferably lower in terms of energy consumption and generation of point defects, and more preferably 1100 ° C. or lower. The firing time is preferably in the range of 30 minutes to 12 hours, more preferably 1 to 6 hours in order for crystal growth to proceed sufficiently and the activator to diffuse uniformly into ZnS. The firing atmosphere uses an oxidizing atmosphere such as air, an inert atmosphere such as nitrogen or argon, a reducing atmosphere such as a hydrogen-nitrogen mixed atmosphere or a carbon-oxygen mixed atmosphere, or a sulfurizing atmosphere such as hydrogen sulfide or carbon disulfide. it can.

  The fired mixture is taken out of the crucible, and acid washing and water washing are sufficiently repeated to remove excess flux, reaction by-products, ZnO formed by oxidizing ZnS, and the like. The washed particles are dried to obtain an EL phosphor. Since the particles after firing may be lightly adhered to each other, it is preferable to loosen them with a ball mill or ultrasonic dispersion. In order to remove coarse particles, sieving with a mesh or the like may be performed. In addition, when Cu is added, excess Cu is deposited on the surface of the ZnS phosphor. Therefore, it is preferable to wash with an aqueous solution of a cyanide compound, a Cu chelating agent, or the like.

  The above-mentioned baked phosphor exhibits its performance sufficiently as it is, but when it is baked at a high temperature and has a wurtzite structure, it is necessary to re-fire after applying stress to the phosphor particles. It is more preferable in order to increase. For applying stress to the phosphor particles, a ball mill, ultrasonic waves, hydrostatic pressure, or the like can be used. In any case, it is preferable to apply the stress uniformly to the particles with a load that does not destroy the phosphor particles. The stressed phosphor is preferably refired at a temperature of 500 to 1000 ° C. This partially converts to a zinc blende structure and increases the efficiency of EL emission. For the firing time and atmosphere of refiring, the same conditions as in the above firing can be used.

The phosphor element obtained by the present invention more preferably has a non-light emitting shell layer on the surface of the phosphor particles. The shell layer is preferably formed with a thickness of 0.1 μm or more using a chemical method following the preparation of the semiconductor fine particles serving as the core of the phosphor element. Preferably they are 0.1 micrometer or more and 1.0 micrometer or less.
The non-light emitting shell layer can be formed from an oxide, a nitride, an oxynitride, or a material having the same composition formed on the phosphor base material and containing no emission center. In addition, substances having different compositions can be epitaxially grown on the phosphor matrix material.
As a method for forming the non-light-emitting shell layer, a gas phase method such as laser, ablation method, CVD method, plasma method, sputtering, resistance heating, electron beam method, etc. Sol-gel method, ultrasonic chemistry method, precursor thermal decomposition method, reverse micelle method or combination of these methods with high temperature firing, urea melting method, freeze drying method, liquid phase method or spray pyrolysis method, etc. Can also be used.

The urea melting method and spray pyrolysis method are also suitable for the synthesis of the non-light emitting shell layer.
For example, when a non-light emitting shell layer is attached to the surface of the zinc sulfide phosphor particles, the metal salt serving as the non-light emitting shell layer material is dissolved, and the zinc sulfide phosphor is added to the molten urea solution. Since zinc sulfide does not dissolve in urea, the temperature of the solution is raised as in the case of particle formation to obtain a solid in which the zinc sulfide phosphor and the non-light emitting shell layer material are uniformly dispersed in the urea-derived resin. After this solid is finely pulverized, it is fired while thermally decomposing the resin in an electric furnace. Zinc sulfide phosphor particles having a non-light emitting shell layer made of oxide, sulfide, or nitride on the surface by selecting an inert atmosphere, an oxidizing atmosphere, a reducing atmosphere, an ammonia atmosphere, or a vacuum atmosphere as a firing atmosphere Can be synthesized.

  For example, when a non-light emitting shell layer is attached to the surface of the zinc sulfide phosphor particles by spray pyrolysis, the zinc sulfide phosphor is added to a solution in which a metal salt serving as a non-light emitting shell layer material is dissolved. . By atomizing and thermally decomposing this solution, a non-light emitting shell layer is generated on the surface of the zinc sulfide phosphor particles. By selecting a pyrolysis atmosphere or an additional firing atmosphere, zinc sulfide phosphor particles having a non-light emitting shell layer made of oxide, sulfide, or nitride on the surface can be synthesized.

[EL element]
The phosphor obtained according to the present invention is preferably used for an electroluminescence element, and the electroluminescence element basically has a configuration in which a light emitting layer is sandwiched between a pair of opposing electrodes, at least one of which is transparent, and A dielectric layer is preferably adjacent between the light emitting layer and the electrode.
For the light emitting layer, the phosphor of the present invention dispersed in a dispersant can be used. As the dispersant, a polymer having a relatively high dielectric constant such as a cyanoethyl cellulose resin, or a resin such as polyethylene, polypropylene, polystyrene resin, silicone resin, epoxy resin, or vinylidene fluoride can be used. The dielectric constant can be adjusted by appropriately mixing fine particles having a high dielectric constant such as BaTiO ₃ and SrTiO _{3 with} these resins. The thickness of the light emitting layer is preferably 0.1 to 100 μm, more preferably 0.5 to 60 μm, and particularly preferably 0.5 to 30 μm.
As the dielectric layer, any material can be used as long as it has a high dielectric constant and insulation and has a high dielectric breakdown voltage. These metal oxides are selected from nitrides, for example _{TiO 2, BaTiO 3, SrTiO 3} , PbTiO 3, KNbO 3, PbNbO 3, Ta 2 O 3, BaTa 2 O 6, LiTaO 3, Y 2 O 3, Al ₂ O ₃ , ZrO ₂ , AlON, ZnS or the like is used. These may be installed as a uniform film, or may be used as a film having a particle structure.

The light emitting layer and the dielectric layer can be applied using a spin coating method, a dip method, a bar coating method, a screen printing method, a spray coating method, or the like. In particular, a doctor blade method, a slide coating method, and an extrusion coating method that can be applied continuously are preferable. The coating liquid used for this is a coating liquid containing at least EL phosphor particles or dielectric particles, a binder, and a solvent for dissolving the binder. Here, as the solvent, acetone, MEK, DMF, butyl acetate, acetonitrile, or the like is used. The viscosity of the coating solution at room temperature is preferably in the range of 0.1 Pa · s to 5 Pa · s, particularly preferably in the range of 0.3 Pa · s to 1.0 Pa · s. When the viscosity of the coating solution is too low, uneven coating film thickness is likely to occur, and the phosphor particles may separate and settle over time after dispersion. On the other hand, when the viscosity of the coating solution is too high, it may be difficult to apply at a relatively high speed. The viscosity is a value measured at 16 ° C. which is the same as the coating temperature.
The dielectric film may be prepared by a gas phase method such as sputtering or vacuum deposition. In this case, the thickness of the film is usually in the range of 100 to 1000 nm.

In the electroluminescent element, any transparent electrode material that is generally used is used as the transparent electrode. Examples thereof include oxides such as indium-doped tin oxide, antimony-doped tin oxide, and zinc-doped tin oxide, a multilayer structure in which a silver thin film is sandwiched between high refractive index layers, and π-conjugated polymers such as polyaniline and polypyrrole.
It is also preferred to improve the conductivity by arranging a comb-type or grid-type fine metal wire on these transparent electrodes.
For the back electrode on the side from which light is not extracted, any conductive material can be used. It is selected from gold, silver, platinum, copper, iron, aluminum and other metals, graphite, etc. depending on the form of the element to be created, the temperature of the production process, etc. It may be used.

The electroluminescence element is preferably processed so as to eliminate the influence of humidity from the external environment by finally using an appropriate sealing material. When the element substrate itself has a sufficient shielding property, a shielding sheet is overlaid on the fabricated element, and the periphery is sealed with a curable material such as epoxy.
Such a shielding sheet is selected from glass, metal, plastic film and the like according to the purpose.

In addition, the electroluminescent element of the present invention preferably includes a phosphor in contact with a dielectric material in the light emitting layer, and is a total of an insulating layer including an inorganic dielectric material adjacent to the light emitting layer including the phosphor if necessary. The film thickness is preferably 3 to 10 times the average particle size (average circle equivalent diameter) of the phosphor particles. The contact between the phosphor particles and the dielectric material is preferably that the phosphor particles are completely or partially covered with the non-light emitting shell layer. However, the phosphor particles and the dielectric material may simply be in contact.
For example, electrons are provided from the interface state formed by the contact between the phosphor and the dielectric material, and the electrons introduced into the phosphor are accelerated by a strong electric field and become hot electrons. The accelerating electrons collide and excite the emission center doped in the phosphor crystal, and light emission with high luminance can be obtained.

The lower limit of the element thickness corresponds to the size (average equivalent circle diameter) of the phosphor particles, but in order to ensure the smoothness of the element, the thickness of the element is 3 to 10 with respect to the size of the phosphor particles. It is preferable that it is double. The thickness of the element here refers to the total thickness of the light emitting layer containing the phosphor sandwiched between the electrodes and the inorganic dielectric layer adjacent thereto.
In addition, by coating the phosphor particles so as to cover a part of the upper part of the phosphor particles, that is, a part of the light emitting layer so that the dielectric layer is partially inserted, the contact point is increased and the smoothness of the element surface is also achieved. An effect such as improving the above appears and is preferable.

The dielectric material used in the electroluminescence element may be a thin film crystal layer or a particle shape. A combination thereof may also be used. The dielectric layer containing the dielectric substance may be provided on one side of the light emitting layer, and is preferably provided on both sides of the light emitting layer. In the case of a thin film crystal layer, it may be a thin film formed on a substrate by a vapor phase method such as sputtering, or a sol-gel film using an alkoxide such as Ba or Sr. In the case of a particle shape, it is preferable that the size is sufficiently small with respect to the size of the phosphor particles. Specifically, the size of the phosphor particles is preferably 1/3 to 1/100, more preferably 1/5 to 1/50.
In addition, in the electroluminescence element preferably using the electroluminescence phosphor produced by the production method of the present invention, when the thickness is thin and excitation is performed with a high electric field, the distance between the electrodes sandwiching the electroluminescence element is uniform. It is important to be. Specifically, when the variation in the distance between the electrodes is viewed as the center line average roughness Ra, it is preferably (d × 1/8) μm or less with respect to the light emitting layer thickness d μm. More preferably, it is (d × 1/10) μm or less.

  The use of the electroluminescence element preferably using the electroluminescence phosphor obtained by the present invention is not particularly limited, but considering the use as a light source, the emission color is preferably white. As a method for changing the emission color to white, it is preferable to mix a plurality of emission color phosphors in the emission layer of the electroluminescence element (blue-green-red combination, blue-green-orange combination, etc.). It is also preferable to emit light at a short wavelength, such as blue, and to convert the wavelength of part of the emitted light to green or red to whiten.

  In addition, in the structure of the electroluminescent element using the electroluminescent phosphor manufactured by the manufacturing method of the present invention, a substrate, a transparent electrode, a back electrode, various protective layers, a filter, a light scattering reflection layer, and the like are provided as necessary. be able to. In particular, regarding the substrate, in addition to a glass substrate or a ceramic substrate, a flexible resin sheet can be used for the flexible substrate.

  The phosphor particles obtained in the present invention are preferably combined with the above-described electroluminescence element configuration as appropriate, thereby providing a high-luminance and high-efficiency electroluminescence element.

  Hereinafter, the phosphor precursor, the EL phosphor, the production method thereof, and the EL element of the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

Example 1
[Formation of phosphor precursor]
Based on Table 1, phosphor precursors were synthesized using a uniform precipitation method.

A reaction mother liquor was prepared by adding and dissolving Zn salt, activator and pH adjuster (acid) shown in Table 1 in distilled water, and the reaction mother liquor was accommodated in a 300 ml three-necked flask. The reaction mother liquor was stirred at a rotation speed of 200 rpm using a screw type stirrer of about 40 mmφ. Each reaction mother liquor was adjusted to pH 2 with a pH adjuster. The three-necked flask containing the reaction mother liquor was heated with a mantle heater and heated to 70 ° C. and held.
To the reaction mother liquor maintained at 70 ° C., solid TA in the amount shown in Table 1 was added all at once and reacted for a predetermined time. The resulting precipitate was subjected to solid-liquid separation at 3000 rpm for 20 minutes using a centrifuge, washed with water and decanted three times using 300 ml of distilled water, and then heated at 120 ° C. using a hot air dryer. It was dried for 2 hours to obtain ZnS phosphor precursor particles containing Cu or Mn and Cu. The generated ZnS phosphor precursor particles are composed of secondary particles obtained by agglomerating primary particles.

Example 2
[Formation of phosphor precursor]
Based on Table 2, phosphor precursors were synthesized using a spray pyrolysis method.

The precursor was synthesized using a spray pyrolysis apparatus combining an ultrasonic atomizer, a 5-zone tubular furnace, and a collector. As the ultrasonic atomizer, eight 1.7 MHz ultrasonic oscillators were used. The five zones of the tubular furnace were set to 200 ° C., 400 ° C., 600 ° C., 800 ° C., and 800 ° C., respectively, and each zone was 30 cm. As the core tube inserted into the tubular furnace, a quartz tube having an inner diameter of 50 mmφ and a length of 2 m was used. The collector used a 0.45 μm pore bag filter to keep the collector at 120 ° C. to prevent condensation. N ₂ was used as a carrier gas, and the flow rate was 10 liters / minute.
Reaction solutions shown in Table 2 were prepared and accommodated in an ultrasonic atomizer of a spray pyrolysis apparatus. The ratio of sulfur to zinc in this solution was 2. After introducing the carrier gas, the ultrasonic atomizer was operated to atomize the reaction solution. The spray pyrolysis apparatus was operated for about 2 hours, and the particles deposited on the filter of the collector were collected to obtain ZnS phosphor precursor particles containing Cu or Mn and Cu. The generated ZnS phosphor precursor particles are composed of secondary particles obtained by agglomerating primary particles.

Comparative Example 1
[Formation of phosphor precursor]
A reaction mother liquor in which 7.44 g of zinc nitrate hexahydrate and 0.006 g of copper nitrate trihydrate were dissolved in 250 ml of distilled water was prepared, and the reaction mother liquor was accommodated in a 300 ml three-necked flask. The reaction mother liquor was stirred at a rotation speed of 200 rpm using a screw type stirrer of about 40 mmφ. The three-necked flask containing the reaction mother liquor was heated with a mantle heater and heated to 60 ° C. and held.
A reaction solution prepared by dissolving 6.0 g of sodium sulfide nonahydrate in 25 ml of distilled water was added to the reaction mother liquor maintained at 60 ° C. at a rate of 1 ml / min, and reacted for 1 hour. The resulting precipitate was subjected to solid-liquid separation at 3000 rpm for 20 minutes using a centrifuge, washed with water and decanted three times using 300 ml of distilled water, and then heated at 120 ° C. using a hot air dryer. It was dried for 2 hours to obtain ZnS phosphor precursor particles containing Cu or Mn and Cu. The generated ZnS phosphor precursor particles had a primary particle size of 6.5 nm, but did not show regular secondary agglomerated particles.

Comparative Example 2
Commercially available zinc sulfide was used as the phosphor precursor. This phosphor precursor had a primary particle size of 19 nm and a secondary particle size of 7 μm.

Example 3
[Calcination of phosphor precursor]
The precursors prepared in Examples 1 and 2 above and the following flux were added and mixed in a mortar to obtain a mixture.
・ Phosphor precursor ... 25.0g
・ Sodium chloride: 1.0 g
・ Barium chloride dihydrate ・ ・ ・ 2.1g
・ Magnesium chloride hexahydrate ... 4.25g
The mixture was filled in an alumina crucible, capped and placed in a room temperature muffle furnace. The muffle furnace was heated at a rate of 400 ° C./h, maintained at 900 ° C., and fired in air for 4 hours. After the completion of firing, the mixture was cooled to room temperature and the alumina crucible was taken out. The calcined mixture is taken out from the alumina crucible, acid washed with 500 ml of 0.1M HCl aqueous solution, then washed with water and decantation 5 times with 500 ml of H ₂ O, and heated at 120 ° C. for 2 hours using a hot air dryer. Dried. As a result, ZnS: Cu, Cl intermediate phosphor particles or ZnS: Mn, Cu, Cl intermediate phosphor particles were obtained.

  Furthermore, 5 g of each dried phosphor particle was filled into a 30 ml volume sample bottle together with 20 g of 1 mm alumina balls, ball milled for 20 minutes at a rotation speed of 10 rpm, and then the alumina balls and phosphor particles were separated using a sieve. separated. The separated phosphor particles were filled in an alumina crucible, capped and placed again in a muffle furnace at room temperature. The muffle furnace was heated at a rate of 400 ° C./h, maintained at 700 ° C., and fired in air for 4 hours. After the completion of firing, the mixture was naturally cooled to room temperature, and the alumina crucible was taken out. The fired mixture was taken out from the alumina crucible, washed with 100 ml of 10% KCN aqueous solution, then washed with 500 ml of distilled water five times and decanted, and dried at 120 ° C. for 2 hours using a hot air dryer. As a result, ZnS: Cu, Cl phosphor particles or ZnS: Mn, Cu, Cl phosphor particles were obtained.

Comparative Example 3
[Calcination of phosphor precursor]
The precursors prepared in Comparative Examples 1 and 2 were fired in the same manner as in Example 3 to obtain ZnS: Cu, Cl phosphor particles.

[Evaluation of particles]
The following items were evaluated for the particles obtained in Examples 1 to 3 and Comparative Examples 1 to 3, and the results are shown in Table 3.
・ Center particle size (using median diameter calculated by LA-920 (trade name) manufactured by Horiba, Ltd.)
-Particle size distribution (using coefficient of variation calculated with LA-920 (trade name) manufactured by Horiba, Ltd.)
・ Primary particle size (measured by calculating the half width of (111) plane of powder X-ray diffraction)
・ Particle shape (SEM observation)
-Stacking fault surface spacing (Phosphor particles are polished with a menor mortar, debris is observed with TEM, and the stacking fault surface spacing is measured.
Stacking fault frequency (100 phosphor particles are observed by TEM, stacking fault frequency is measured, 30% or more ○)

Example 4
[Creation of EL element]
An EL device was prepared using phosphors obtained by firing Examples 1-2 and 2-2 (referred to as phosphors A and B, respectively).
An ITO electrode having a surface resistivity of 100Ω / □ is laminated on a 100 μm PET support, and then the phosphor A or B is cyanoresin (manufactured by Shin-Etsu Chemical Co., Ltd .; CR-S (trade name) on the surface of the ITO electrode. The phosphor layer dispersion (using DMF as a solvent, solid content concentration of about 60% by mass) dispersed in ()) was applied with a slide coater to form a light emitting layer with a dry film thickness of 20 μm. Next, a dielectric particle dispersion liquid (using DMF as a solvent, solid content concentration of 58 mass%) in which BaTiO ₃ dielectric particles having a center particle size of 0.2 μm are dispersed in cyanoresin is superimposed on the formed light emitting layer using a slide coater. By coating, a dielectric layer was formed with a dry film thickness of 20 μm. Next, a back electrode layer is formed on the dielectric layer using a silver particle dispersion liquid (butyl acetate as a solvent, solid content concentration 55% by mass) in which silver fine particles are dispersed in a polyester resin in the same area as the dielectric layer. Was formed with a slide coater with a film thickness of 10 μm to obtain a laminate sheet in which a light emitting layer, a dielectric layer, and a back electrode were sequentially laminated on the ITO electrode. Finally, each laminated body was cut out to A4 size, the extraction electrode was attached to the transparent electrode and the back electrode, respectively, and the whole laminated body was sealed with the moisture proof film, and the EL element was obtained. EL elements using phosphor particles A and B in the light emitting layer were referred to as EL element A and EL element B, respectively.

Comparative Example 4
[Creation of EL element]
Using the phosphors obtained by firing the comparative examples 1 and 2 (referred to as phosphors C and D, respectively), EL elements were prepared in the same manner as in Example 4, and EL elements C and D were obtained. It was.

[Evaluation of EL element]
An AC voltage of 1 kHz was applied to the EL element at 200 V, and the EL luminance was measured with a luminance meter (Topcon Co., Ltd .; BM9 (trade name)). The measurement results of luminance are shown in Table 4.

The phosphor particles of the example of the present invention have good stacking fault plane spacing and frequency, while the comparative phosphor particles of the comparative example have insufficient plane spacing and frequency. In addition, the coefficient of variation of the phosphor particles of Comparative Example 1 is extremely large, and it is clear that the size of the secondary aggregated particles is important. Also in EL luminance, the EL element of the example showed higher luminance than the EL element of the comparative example.
As described above, the ZnS phosphor precursor of the present invention and the EL phosphor prepared using the same can obtain high EL luminance even at a firing temperature of 900 ° C. Moreover, the manufacturing method of the ZnS fluorescent substance precursor of this invention can manufacture the above useful ZnS fluorescent substance precursors with a high yield.

Claims (10)

  Selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements in which the central particle size is in the range of 0.05 to 5.0 μm, the primary particles having a central particle size in the range of 1 to 20 nm are aggregated. A zinc sulfide-based phosphor precursor characterized by comprising secondary particles having at least one kind. General formula: ZnS: M, X
(Wherein M represents at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements, and X represents at least one element selected from the group consisting of halogen elements and aluminum.)
The center particle size is in the range of 0.1 to 15 μm, and is obtained by mixing and firing at least the precursor according to claim 1 and a compound containing an element represented by X. An electroluminescent phosphor.   The phosphor has planar stacking faults, and particles having 10 or more stacking faults with a plane spacing of 5 nm or less of the stacking faults are present in 30% or more of all phosphor particles. The electroluminescent phosphor according to claim 2.   4. The electroluminescent phosphor according to claim 2, wherein the coefficient of variation in particle size is less than 35%. Selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements in which the central particle size is in the range of 0.05 to 5.0 μm, the primary particles having a central particle size in the range of 1 to 20 nm are aggregated. A method for producing a precursor of a zinc sulfide-based phosphor containing secondary particles having at least one kind of
Preparing a solution in which at least a zinc compound and a compound containing at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements are dissolved; and adding thioacetamide to the solution; Heating the solution to a temperature in the range of 60 to 100 ° C. to hydrolyze thioacetamide to obtain a precipitate of zinc sulfide containing at least one of Cu, Mn, Ag, Au, or a rare earth element; A method for producing a precursor of a zinc sulfide-based phosphor. Selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements in which the central particle size is in the range of 0.05 to 5.0 μm, the primary particles having a central particle size in the range of 1 to 20 nm are aggregated. A method for producing a precursor of a zinc sulfide-based phosphor containing secondary particles having at least one kind of
Preparing a solution in which at least a zinc compound, a compound containing at least one element selected from the group consisting of Cu, Mn, Ag, Au, and rare earth elements, and thioacetamide, thiourea, and derivatives thereof are dissolved; The solution is atomized as fine droplets and introduced into a carrier gas, and the fine droplets introduced into the carrier gas are thermally decomposed by heating to a temperature in the range of 500 to 1000 ° C. to obtain Cu, Mn And a step of obtaining zinc sulfide particles containing at least one of Ag, Au, or a rare earth element. General formula: ZnS: M, X
(Wherein M represents at least one element selected from the group consisting of Cu, Mn, Ag, Au and rare earth elements, and X represents at least one element selected from the group consisting of halogen elements and aluminum.)
A method for producing an electroluminescent phosphor represented by:
It is selected from the group consisting of a precursor of a zinc sulfide phosphor containing at least one of Cu, Mn, Ag, Au or a rare earth element obtained by the method according to claim 5 or 6, a halogen element and aluminum. An electroluminescence process comprising: a step of mixing a compound containing at least one element to obtain a mixture; and a step of firing the mixture at a temperature in the range of 700 to 1200 ° C. to obtain phosphor particles. A method for producing a phosphor.   8. The method according to claim 7, further comprising a step of applying stress to the extent that the phosphor particles are not crushed after the firing step, and a step of re-baking the stressed phosphor particles at 500 to 1000 ° C. 8. A method for producing an electroluminescent phosphor.   An electroluminescent element comprising the electroluminescent phosphor according to any one of claims 2 to 4 in a light emitting layer. The electroluminescent element according to claim 9, wherein the light emitting layer has a thickness of 0.5 to 30 μm.