JP2010229178A - Inorganic phosphor material and dispersion-type electroluminescence device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion-type electroluminescence device that emits red light, and to provide an inorganic phosphor material useful for production of the dispersion-type electroluminescence device. <P>SOLUTION: The inorganic phosphor material is characterized by including: a base material which is a mixed crystal including at least one or two or more compounds selected from compounds containing at least one element selected from elements in group XII and at least one element selected from elements in group XVI of the Periodic Table, wherein the base material contains at least one element selected from elements belonging to group XIII of the Periodic Table, Cu, and Mn. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dispersive electroluminescent device and an inorganic phosphor material useful for manufacturing a dispersive electroluminescent device.

  A phosphor is a material that emits light when given energy such as light, electricity, pressure, heat, and electron beam from the outside. A phosphor made of an inorganic material is a cathode ray tube because of its emission characteristics and stability. , Fluorescent lamps, electroluminescence (EL) elements, and the like. In recent years, active research has been conducted on LED color conversion materials and low-energy electron beam-excited phosphors in PDPs.

  A phenomenon that emits light when an electric field is applied to a phosphor is referred to as electroluminescence (EL), and a light-emitting element that utilizes this phenomenon is referred to as an electroluminescence (EL) element. There are two types of EL elements: a dispersion type EL element in which phosphor particles are dispersed in a high dielectric constant binder to form a light emitting layer, and a thin film type EL element in which a phosphor thin film is sandwiched between dielectric layers. In particular, the dispersion type EL element does not use a high-temperature process, so that a flexible element using a plastic substrate can be manufactured, and it can be manufactured in a relatively simple and low-cost process without using a vacuum apparatus. It has the feature of being possible. Furthermore, a dispersion type EL device manufactured using phosphor particles can have a thickness of several millimeters or less, is a light source that emits light, and has many advantages such as low heat generation and good luminous efficiency. Applications are expected as road signs, illumination for various interiors and exteriors, light sources for flat panel displays such as liquid crystal displays, and illumination light sources for large areas.

  When the dispersion type EL element is used as a backlight light source or an illumination light source, the emission color is preferably white, but a phosphor that emits white light alone is not known. Therefore, it is necessary to combine several emission colors. For example, white light emission can be obtained by a combination of blue-green light emission-red light emission and blue light emission-yellow light emission. However, there are no promising phosphors for dispersion-type inorganic EL other than ZnS: Cu, Cl that emits blue-green light, and fluorescence that emits red light (emission peak wavelength: 600 nm or more). Little is known about the body.

  Therefore, in the prior art, a ZnS: Cu, Cl phosphor that emits blue-green light by electroluminescence and an organic compound that absorbs the emission color of the ZnS: Cu, Cl phosphor and emits red light are added to the light emitting layer. Then, examination which obtains white light emission by combining both light emission has been made (patent documents 1 and 2). However, these inorganic EL elements were colored by the added organic compound even when no light was emitted. Therefore, although white light emission can be obtained by applying an electric field, it is not suitable for general lighting applications from the viewpoint of appearance when no light is emitted.

On the other hand, materials such as ZnGa ₂ S ₄ : Mn, Ba ₂ ZnS ₃ : Mn have been known for a long time as phosphor materials that emit red light in thin-film inorganic EL (Patent Document 3, Patent Document 4, Non-Patent Document 1). ).

Japanese Patent Laid-Open No. 2-78188 JP 2006-156358 A JP-A-55-147484 JP 2005-162948 A

Journal of Vacuum Science & Technology, Vol. 10, p. 789, 1973

However, even when the present inventors applied these materials to the dispersion-type inorganic EL, red light emission by applying an electric field was not obtained. This is thought to be due to the difference in light emission mechanism between the thin film type and the dispersion type.
The thin-film inorganic EL is emitted from the interface state between the light emitting layer and the insulating layer when an electric field is applied, and electrons (hot electrons) accelerated by the electric field excite the emission center to emit light. On the other hand, in the dispersion-type inorganic EL, an electron generation source (for example, a Cu ₂ S needle-like crystal) exists in the stacking fault inside the phosphor particles, and when an electric field is applied, electrons and holes are emitted therefrom, which are donors. After being captured by the acceptor level and recombined, light is emitted. Alternatively, the recombination energy becomes the excitation energy of another emission center existing inside the particle, and emits light. Therefore, it is considered that even if the thin-film EL phosphor that does not contain an electron generation source is directly used as a dispersion-type inorganic EL, no electrons are generated to excite the emission center, so that no light emission is obtained.
Therefore, an object of the present invention is to obtain a dispersion type electroluminescent device that emits red light and an inorganic phosphor material that is useful for manufacturing a dispersion type electroluminescent device.

  As a result of intensive studies, the inventors have determined that at least one element selected from elements belonging to Group 13 of the periodic table, Cu, and Mn are at least one element selected from Group 12 elements of the periodic table. By adding to a compound composed of at least one selected from Group 16 elements, a novel inorganic phosphor material that exhibits red luminescence by photoluminescence when excited by ultraviolet light and electroluminescence when an AC dispersion type element is formed is found. As a result, the present invention has been achieved.

That is, the present invention is achieved by the following requirements.
[1]
An inorganic phosphor having as a base material at least one selected from compounds consisting of at least one selected from Group 12 elements of the Periodic Table and at least one selected from Group 16 elements, or a mixed crystal consisting of two or more. An inorganic phosphor material, characterized in that the host material contains at least one element selected from elements belonging to Group 13 of the periodic table, Cu, and Mn.
[2]
The inorganic phosphor material according to [1], wherein the element belonging to Group 13 of the periodic table is Al, Ga, or In.
[3]
The phosphor material is phosphor particles, and among the total phosphor particles, 20% or more of the particles are particles containing 10 or more planar stacking faults at intervals of 5 nm or less. The inorganic phosphor material according to [1] or [2].
[4]
The inorganic phosphor material according to [3], wherein the average particle size of the phosphor particles is 20 μm or less, and the coefficient of variation in particle size is 40% or less.
[5]
[1] A dispersion type electroluminescent device comprising the light emitting layer containing the inorganic phosphor material according to any one of [4].

  According to the inorganic phosphor material of the present invention, a dispersion type EL element that emits red light can be obtained. Further, by combining the inorganic phosphor material of the present invention with a conventionally known phosphor exhibiting blue-green EL light emission, a white light-emitting dispersed EL element useful for lighting applications and the like can be obtained.

It is a figure which shows the outline of the structure of the dispersion | distribution type inorganic EL element produced by the Example and the comparative example.

The present invention will be described in detail below.
(Inorganic phosphor material)
The inorganic phosphor material of the present invention is at least one selected from a compound consisting of at least one selected from Group 12 elements of the periodic table and at least one selected from Group 16 elements, or a mixed crystal consisting of two or more. Is a matrix material, and the matrix material contains at least one element selected from elements belonging to Group 13 of the periodic table, Cu, and Mn.

  In addition, the compound which consists of at least 1 type chosen from the 12th group element of a periodic table used as a base material of the inorganic fluorescent material material of this invention and a 16th group element is a 12-16 group compound This is a notation / expression normally used by those having ordinary knowledge in the technical field to which the present invention belongs (a person skilled in the art).

Examples of elements belonging to Group 12 of the periodic table used for the base material of the inorganic phosphor material of the present invention include Zn, Cd, and Hg, but Zn or Cd is preferably used.
Examples of elements belonging to Group 16 of the periodic table include O, S, Se, Te, and Po. S, Se, and Te are preferably used.

  Examples of the base material include ZnS, ZnSe, ZnSSe, ZnTe, CdS, CdSe, CdTe, and the like. More preferred is ZnS, ZnSe, ZnSSe, and even more preferred is ZnS.

The inorganic phosphor material of the present invention contains at least one element belonging to Group 13 of the periodic table, Cu, and Mn. Thereby, when used for a dispersion-type electroluminescence element, an inorganic phosphor material that emits light in the red region can be obtained. For example, a phosphor having Mn in ZnS is generally orange with an emission peak wavelength of around 580 nm, whereas the emission peak wavelength of the inorganic phosphor material of the present invention is longer than that in the red region. It is preferable as a phosphor for dispersed inorganic EL that emits red light. Mn of emission are present in the 3d orbital of ^{Mn 2+} (3d ⁵⁾ due ions in transition, called d-d transition by electron, 3d orbitals strongly influenced by the crystal field for the outermost shell of ^{Mn 2+} ions receive. When an element belonging to Group 13 such as Al or Ga is added to ZnS, the ionic ^bondability of the crystal is increased, and the intensity of the crystal field around Mn ²⁺ is increased. It is assumed that the wavelength becomes longer.

In the thin-film type inorganic EL, such based on the idea ZnGa 2 S _4: Although _Mn and the like have been studied as a fluorescent material emitting red light, the electron generating source therein more particles in the case of the dispersion-type inorganic EL Therefore, even if the aforementioned ZnGa ₂ S ₄ : Mn is used as it is, no light emission can be obtained. In the dispersion type inorganic EL phosphor, for example, when the base material is ZnS, there are two crystal structures, a hexagonal system and a cubic system, and stacking faults occur when the crystal system is converted by applying heat or stress. And Cu ₂ S serving as an electron generation source can be stably present in the stacking fault portion. On the other hand, since ZnGa ₂ S ₄ has only a tetragonal crystal structure, stacking faults cannot be formed like ZnS, and even if Cu is doped, it cannot be present as an electron generation source inside the particle. For this reason, light emission cannot be obtained with the dispersion-type inorganic EL.

In the present invention, at least one element selected from elements belonging to Group 13 of the periodic table, Cu, and Mn are contained in the matrix material of the phosphor particles, thereby using the dispersion type EL element. In this case, an inorganic phosphor material that emits light in a red region having an emission peak wavelength of 600 nm or more can be obtained.
Preferably, by forming a stacking fault in the base material, light emission in a red region having an emission peak wavelength of 600 nm or more can be obtained with the dispersion-type inorganic EL.

The method of incorporating the element belonging to Group 13 of the above periodic table into the base material, that is, the doping method is not limited to any method. For example, when forming the phosphor particles by firing, If it can be melted, sublimated or reacted under firing conditions, it may be mixed in the form of compound crystals. Alternatively, the metal salt may be made into an aqueous solution and added to the suspension of the base material with stirring, and the solvent may be evaporated and then fired and then taken in. Such compounds may be any compounds such as oxides, sulfides, oxysulfides, oxides, halides, nitrates and nitrides, but sulfides, oxides and halides are preferably used. . The dope amount is preferably 1 × 10 ^{−3 to} 5 × 10 ⁻¹ mol, and more preferably 5 × 10 ⁻³ to 1 × 10 ⁻¹ mol, relative to 1 mol of the base material.

  Examples of the elements belonging to Group 13 of the periodic table used in the inorganic phosphor material of the present invention include B, Al, Ga, In, and Tl, and Al, Ga, and In are preferably used.

Even when Cu and Mn are doped into the phosphor particles of the present invention, a method similar to the doping method of the base material of an element belonging to Group 13 of the periodic table can be used. The doping amount is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol, more preferably 5 × 10 ^{−4 to} 5 × 10 ⁻³ mol, with respect to 1 mol of the base material. Moreover, about Mn, 1 * 10 < ^-3 > ^-1 * 10 <^-1> mol is preferable with respect to 1 mol of base materials, and 5 * 10 ^{< -3} > -5 * 10 ^<-2> mol is more preferable.

The phosphor material of the present invention is a phosphor particle, and it is preferable that 20% or more of all phosphor particles contain 10 or more planar stacking faults at intervals of 5 nm or less. . More preferably, 30% or more of the particles contain 10 or more planar stacking faults at intervals of 5 nm or less.
The stacking fault described here refers to a twin plane and a phase interface. Taking ZnS as an example, these planes are usually surface defects perpendicular to the {111} plane. General descriptions of stacking faults are described in detail in Chapters 1 and 7 of “Lattice Defect” (B. Henderson: Author, Masao Doyama: Translation, Maruzen Co., Ltd.). In the case of ZnS, Andrew C. WeightandIanV. F. Viney, PhilosophyMag. B, 2001, Vol. 81, no. 3, p279-p297.

  The stacking fault is evaluated by observing the structure on the stack that appears on the particle side surface (particle surface) when phosphor particles are etched with an acid such as hydrochloric acid. The stacking fault is present at the interface between the layer structure and becomes visible on the stripe on the surface by etching. Such a layer structure exists in one whole particle, and can be clearly counted by SEM or TEM. Further, when the material is pulverized and opened vertically to the stacking fault surface, the layer structure can be clearly observed by TEM. For example, it is possible to directly observe the interval and the number of stacking faults by grinding phosphor particles with an agate mortar and observing the particle fragments by TEM. At least the particles containing 10 or more of this planar laminated structure with an interval of 5 nm or less are the stacking fault particles in the present invention.

  It is known that there is a fine structure with respect to the plane spacing of stacking faults. When a transmission electron microscope image of the fragment particles obtained by pulverizing the inorganic phosphor material of the present invention is observed, it may be observed that 10 or more planar stacking faults are present at intervals of 5 nm or less. The inorganic phosphor material of the present invention preferably has 10 or more planar stacking faults at a high density of 5 nm or less, more preferably 15 or more, and still more preferably 18 or more. It is to have.

The average particle diameter of the particles constituting the phosphor particles is preferably 20 μm or less, and more preferably 18 μm or less. Moreover, 50 nm or more is preferable. This is because the stacking fault is preferably high density. The variation coefficient of the particle size (particle size) in the present invention can be calculated by (standard deviation of volume weighted particle size distribution ÷ average particle size of volume weight × 100%), preferably 40% or less, More preferably, it is 38% or less. Moreover, 15% or more is preferable. If it is this range, it is preferable from a viewpoint on manufacture. 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 picture of the individual particles, the distribution may be measured optically, or the distribution may be determined from the settling velocity.
Here, the average particle size refers to the median diameter.

  In the inorganic phosphor material of the present invention, stacking faults spontaneously occur in the phosphor particles by firing. However, the phosphor particles are fine particles and so that more stacking faults are included in the phosphor particles. More preferably, firing is performed, and the conditions of the first firing and the second firing are appropriately selected.

Further, the density of stacking faults can be obtained without destroying the particles by applying an impact force in a certain range to the phosphor particles, preferably the fired product obtained from the first firing (intermediate phosphor particles). Can be greatly increased.
As a method of applying impact force, a method of bringing phosphor particles into contact with each other, a method of mixing and mixing spheres such as alumina (ball mill), a method of accelerating and colliding particles, a method of irradiating ultrasonic waves, a hydrostatic pressure The method of applying, the method of generating a pressure instantaneously by the impact by explosions, such as explosives, can be used preferably.

As a method for giving an impact, it is preferable to use a ball mill. Hereinafter, a ball mill will be described as an example.
Glass, alumina, zirconia, and the like can be preferably used for the container and ball used for the ball mill, and alumina and zirconia can be more preferably used in terms of contamination by the ball. The ball diameter to be used is preferably in the range of 0.01 to 10 mm, and more preferably 0.05 to 1 mm. By setting the ball diameter to an optimum value, if it is too small, separation from the intermediate phosphor particles after the treatment is facilitated, and the intermediate phosphor particles are prevented from being crushed and uniform stress application is facilitated. It is also preferable to mix two or more kinds of balls having different ball diameters because stress can be uniformly applied to the intermediate phosphor particles.

  The ratio of the intermediate phosphor to the ball is preferably in the range of 1 to 100 parts by mass, more preferably 2 to 20 parts by mass with respect to 1 part by mass of the intermediate phosphor. The filling rate of the mixture of balls and intermediate phosphor is preferably in the range of 10 to 60% by volume with respect to the volume of the container. The rotational speed of the ball mill is appropriately selected depending on the outer diameter of the container, but the linear velocity at this time is preferably in the range of 1 to 500 cm / sec, more preferably 10 to 100 cm / sec, and the mixture of the ball and the intermediate phosphor is It is preferable that the rotation speed is set so that a half-moon-like motion is performed in the container and the tilt angle of the rotating ball is in the range of 5 to 45 °. Although the time of a ball mill changes with said conditions, such as rotation speed, the range of 1 minute-24 hours is preferable and 10 minutes-3 hours are more preferable. These conditions are preferably combined appropriately from the luminance and lifetime of the EL phosphor.

The above is a method in which the ball mill is dry, but in the case of wet, organic solvents such as alcohols and ketones can be used as a solvent in addition to water. The amount of solvent to be added is optimally the amount that just fills the gaps between the balls, but in order to improve the fluidity of the mixture, it is preferable to add a range of 1 to 10 times the volume to be filled. By optimizing the amount of solvent to be added, the fluidity of the mixture is maintained, and uniform stress application is facilitated. In order to improve the fluidity of the mixture, a surfactant, water glass or the like may be added as a dispersant. The other ball mill conditions are preferably in the same range as the dry ball mill.
In the case of applying stress using a ball, a device for forcibly stirring the ball with an impeller, a rotor, or the like, a device for vibrating the container, or the like can also be used.

  Moreover, the probability of occurrence of stacking faults is low simply by applying an impact force, and stacking faults are generated at a high density by further firing thereafter.

The inorganic phosphor material that can be used in the present invention can be formed by a firing method (solid phase method) widely used in the industry except the step of introducing many stacking faults described above.
For example, in the case of zinc sulfide, a fine particle powder (called raw powder) having a particle diameter of 10 nm to 50 nm is prepared by a liquid phase method, and this is used as a primary particle, and an impurity called an activator is mixed into the flux. At the same time, first baking is performed in a crucible at a high temperature of 900 ° C. to 1300 ° C. for 30 minutes to 10 hours to obtain particles. The intermediate phosphor powder obtained by the first firing is repeatedly washed with ion exchange water to remove alkali metal or alkaline earth metal, excess activator and coactivator. In this process, it is preferable to appropriately use the step of introducing the stacking fault described above. Next, second baking is applied to the obtained intermediate phosphor powder. In the second baking, heating (annealing) is performed at a temperature lower than that of the first baking at 500 to 800 ° C. and for a short time of 30 minutes to 3 hours.

<EL element>
Hereinafter, a dispersion-type electroluminescent element (hereinafter also referred to as an EL element of the present invention) using the inorganic phosphor material of the present invention will be described.
The dispersion-type EL element using the inorganic phosphor material of the present invention has, for example, at least one light emitting layer containing the inorganic phosphor material of the present invention between a pair of opposed electrodes, one of which is a transparent electrode. . A dielectric layer such as an insulating layer or a blocking layer is preferably disposed between the light emitting layer and the electrode in order to prevent dielectric breakdown of the EL element and concentrate a stable electric field on the light emitting layer.
Next, a dispersion-type inorganic EL element using the inorganic phosphor material of the present invention will be described.
The dispersion type electroluminescent device (preferably an AC dispersion type EL device) of the present invention comprises at least a dielectric layer, a phosphor layer, and a pair of electrodes sandwiching these layers, at least one of the electrodes being transparent. It is a normal form to use an electrode having a characteristic.

(Transparent electrode)
The surface resistivity of the transparent conductive film preferably used in the present invention is preferably 10Ω / □ or less, more preferably 0.01Ω / □ to 10Ω / □. In particular, 0.01Ω / □ to 1Ω / □ is preferable.
The surface resistivity of the transparent conductive film can be measured according to the method described in JIS K6911.
The transparent conductive film is preferably formed on a glass or plastic substrate and contains tin oxide.

That is, as glass, general glass such as alkali-free glass or soda lime glass is used, but it is preferable to use glass having high heat resistance and high flatness. As the plastic substrate, a transparent film such as polyethylene terephthalate, polyethylene naphthalate, or triacetyl cellulose base is preferably used. Using these as a substrate, a transparent conductive material such as indium tin oxide (ITO), tin oxide, or zinc oxide can be deposited and formed by a method such as vapor deposition, coating, or printing.
In this case, it is preferable that the surface of the transparent conductive film is mainly composed of tin oxide for the purpose of increasing durability.

The preferable adhesion amount of the transparent conductive material constituting the transparent conductive film is 100% by mass to 1% by mass, more preferably 70% by mass to 5% by mass, and still more preferably 40% by mass with respect to the transparent conductive film. -10 mass%.
The method for preparing the transparent conductive film may be a gas phase method such as sputtering or vacuum deposition. Paste-like ITO or tin oxide may be produced by coating or screen printing, or the whole film may be heated or heated with a laser to form a film.
In the EL device of the present invention, any transparent electrode material that is generally used is used for the transparent conductive film. For example, tin-doped tin oxide, antimony-doped tin oxide, zinc-doped tin oxide, fluorine-doped tin oxide, zinc oxide and other oxides, a multilayer structure in which a silver thin film is sandwiched between high refractive index layers, polyaniline, polypyrrole and other conjugated systems Examples include molecules.

  In order to further reduce the resistance, it is preferable to improve the conductivity by arranging, for example, a comb-shaped or grid-shaped mesh or striped metal fine wire. Copper, silver, aluminum, nickel, or the like is preferably used as the metal or alloy thin wire. The thickness of the fine metal wire is arbitrary, but is preferably between about 0.5 μm and 20 μm. The fine metal wires are preferably arranged at a pitch of 50 μm to 400 μm, and a pitch of 100 μm to 300 μm is particularly preferable. Although the light transmittance is reduced by arranging the fine metal wires, it is important that this reduction is as small as possible, and it is preferable to secure a transmittance of 80% or more and less than 100.

For the fine metal wires, the mesh may be bonded to the transparent conductive film, or a metal oxide or the like may be applied and vapor-deposited on the fine metal wires previously formed on the film by mask vapor deposition or etching. Moreover, you may form said metal fine wire on the metal oxide thin film formed previously.
Although this is a different method, a transparent conductive film suitable for the present invention can be obtained by laminating a metal thin film having an average thickness of 100 nm or less with a metal oxide instead of a thin metal wire. The metal used for the metal thin film is preferably a metal having high corrosion resistance such as Au, In, Sn, Cu, and Ni and excellent in spreadability, but is not particularly limited thereto.
These multilayer films preferably realize high light transmittance, specifically, preferably have a light transmittance of 70% or more, and particularly preferably have a light transmittance of 80% or more. The wavelength that defines the light transmittance is 550 nm.
Regarding the light transmittance, monochromatic light of 550 nm can be taken out using an interference filter, and can be measured using an integral light quantity measurement or a spectrum measuring apparatus using a commonly used white light source.

(Back electrode)
For the back electrode on the side from which light is not extracted, any conductive material can be used. It is selected appropriately from metals such as gold, silver, platinum, copper, iron, aluminum, graphite, etc., depending on the form of the device to be produced, the temperature of the production process, etc. Among them, it is important that the thermal conductivity is high. 2.0 W / cm · deg or more is preferable.
It is also preferable to use a metal sheet or a metal mesh in order to ensure high heat dissipation and electrical conductivity in the periphery of the EL element.

(Light emitting layer (phosphor layer))
In the dispersion type electroluminescent device of the present invention, it is preferable to contain an inorganic phosphor material in the light emitting layer.
When an AC dispersion type EL device is produced using the inorganic phosphor material of the present invention, these particles are dispersed in an organic dispersion medium, and the dispersion liquid is applied to form a phosphor layer. As the organic dispersion medium, an organic polymer material or an organic solvent having a high boiling point can be used, but an organic binder mainly composed of the organic polymer material is preferable.
The organic binder is preferably a material having a high dielectric constant, such as a fluorine-containing polymer compound (for example, a polymer compound containing ethylene fluoride, trifluoride monochloride as a polymerization unit), or a polysaccharide having a hydroxyl group cyanoethylated. (Cyanoethyl pullulan, cyanoethyl cellulose), polyvinyl alcohol (cyanoethyl polyvinyl alcohol), phenol resin, polyethylene, polypropylene, polystyrene resin, silicone resin, epoxy resin, vinylidene fluoride, and all or part of them Preferably it comprises. In addition, 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 binders.
The blending ratio of the binder and the luminescent particles is preferably such that the content of the luminescent particles in the phosphor layer is 30 to 90% by mass with respect to the entire solid content, and is 60 to 85% by mass. It is more preferable to set the ratio to%. As the binder, a polymer compound in which the hydroxyl group is cyanoethylated is preferably used in an amount of 20% or more, more preferably 50% or more, in a mass ratio of the organic dispersion medium of the entire luminescent particle-containing layer.

  The thickness of the phosphor layer thus obtained is preferably 1 μm or more and 200 μm or less, more preferably 3 μm or more and 100 μm or less.

  Further, as disclosed in Japanese Patent Application Laid-Open No. 2004-137482, it is also preferable to use the inorganic phosphor material of the present invention by covering it with a non-light emitting shell made of oxide, sulfide, or nitride.

(Dielectric layer)
Moreover, it is preferable that the AC dispersed inorganic EL element of the present invention has a dielectric layer on the side opposite to the transparent electrode as viewed from the phosphor layer. The dielectric layer can be formed using any material as long as it is a dielectric material having a high dielectric constant and insulation and 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 thin film crystal layer, or may be used as a film having a particle structure. A combination thereof may also be used.

(Production method)
In the AC dispersion type EL device of the present invention, the phosphor layer and the dielectric layer are formed by dissolving a forming material in a solvent using a spin coating method, a dip coating method, a bar coating method, a spray coating method, or the like. It is preferable to form by coating. In particular, it is preferable to use a method that does not select a printing surface, such as a screen printing method, or a method that allows continuous application, such as a slide coating method. In the case of using these coatings, it is preferable to prepare and use a coating solution in which an appropriate organic solvent is added to the constituent materials of the phosphor layer and the dielectric layer. Preferred organic solvents include dichloromethane, chloroform, acetone, acetonitrile, methyl ethyl ketone, cyclohexanone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, toluene, xylene and the like. The phosphor layer is particularly preferably formed by continuous coating so that the dry film thickness of the coating film is 5 μm or more and 50 μm or less.
Each layer coated on the support is preferably a continuous process from at least the coating to the drying process. The drying process is divided into a constant rate drying process until the coating film is dried and solidified, and a decreasing rate drying process for reducing the residual solvent of the coating film. In the drying process, it is preferable that the constant rate drying process is carried out gently, and the reduced rate drying process is carried out at a temperature sufficient for the solvent to dry. As a method for slowly performing the constant rate drying step, it is preferable to divide the drying chamber in which the support travels into several zones and increase the drying temperature after the coating step in a stepwise manner.

(Sealing)
It is preferable that the dispersion type EL element of the present invention is finally processed using a sealing film so as to eliminate the influence of humidity and oxygen from the external environment. Details of the sealing are as described in JP-A-2007-12466, [0050] to [0055].

Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to these.
[Example 1]
25 g of zinc sulfide (ZnS) particle powder, gallium sulfide, copper sulfide, and manganese sulfide with respect to zinc: Ga: 5 × 10 ⁻² mol / mol, Cu: 9 × 10 ⁻⁴ mol / mol, Mn: 3 × 10 ^-2 mol / mol added dry powder, NaCl, MgCl ₂ and ammonium chloride (NH ₃ Cl) powder as flux, appropriate amount, magnesium oxide powder 10% by mass with respect to phosphor powder, in alumina crucible The mixture was then fired at 1150 ° C. for 2 hours (first firing), and then the temperature was lowered. After 5g of the fired particles, 20g of 1mmφ alumina balls are filled in a 15mmφ glass bottle and ball milled at a rotation speed of 10rpm for 20 minutes, and then the alumina balls and intermediate phosphor particles are put together using a 100 mesh sieve. separated. Further, 5 g of ZnO and 0.25 g of sulfur were added to prepare a dry powder, which was again put in an alumina crucible and fired at 700 ° C. for 6 hours (second firing). After firing, the particles are pulverized again, dispersed and settled in 40 ° C. H ₂ O, and the supernatant removed, washed, and then added with a 10% by mass hydrochloric acid solution to disperse, settle and remove the supernatant. Salt was removed and dried. Furthermore, a 10 mass% KCN aqueous solution was heated to 70 ° C. to remove oxides such as ZnO on the surface. Further, the surface layer corresponding to 10% by mass of the whole particles was removed by etching with 0.1N hydrochloric acid.
The particles thus obtained were further sieved to take out small size particles.
The phosphor particles thus obtained were observed with an electron microscope, and the particle diameters of the 500 particles were examined. As a result, the average particle diameter was 19 μm and the variation coefficient of the particle diameter was 38%. In addition, the phosphor particles were pulverized in a mortar, and fragments having a thickness of 0.2 μm or less were taken out and observed under an electron microscope condition at an acceleration voltage of 200 kV. As a result, 25% (number of particles) of the observed fragment particles. Included a portion having 10 or more planar stacking faults with an interval of 5 nm or less (described in Table 1 as a high density stacking fault content frequency (number of particles)).

An AC-dispersed inorganic EL element was produced using the inorganic phosphor material produced above. An outline of the structure of the AC dispersion type inorganic EL element is shown in FIG.
On the aluminum electrode (back electrode) (7) having a thickness of 70 μm, the following layers are formed by applying the respective layer forming coating liquids in the order of the first layer and the second layer, and further indium-tin oxide The polyethylene terephthalate film base (thickness 75 μm) (2) sputtered from the object (3) to form a transparent electrode having a thickness of 40 nm is directed to the aluminum electrode (7) side with the transparent electrode (3) side (conductive surface side). In this way, the transparent electrode (3) and the phosphor layer (5) as the second layer were adjacent to each other and pressed with a heat roller at 190 ° C. in a nitrogen atmosphere.

  The additive amount of each layer shown below represents the mass per square meter of the EL element.

First layer: dielectric layer (6) (film thickness 30 nm)
Cyanoethyl pullulan 14.0g
Cyanoethyl polyvinyl alcohol 10.0g
Barium titanate particles (average sphere equivalent diameter 0.05 μm) 100.0 g
Second layer: phosphor layer (5) (film thickness 55 nm)
Cyanoethyl pullulan 18.0g
12.0 g of cyanoethyl polyvinyl alcohol
Inorganic phosphor material (4) produced above 120.0 g

  Each layer was prepared by adding dimethylformamide to prepare a coating solution having a controlled viscosity, and then dried at 110 ° C. for 10 hours.

  As described above, the film (2) with the transparent electrode (3) is pressure-bonded to the coated material thus obtained, and electrode terminals (aluminum plate having a thickness of 60 μm) are applied to the aluminum electrode (7) and the transparent electrode (3), respectively. ), And sealed with a sealing film (polyethylene chlorotrifluoroethylene; thickness 200 μm) (1, 8) to produce an AC dispersed inorganic EL element.

[Example 2]
The production of the inorganic phosphor material was performed in the same manner as in Example 1 except that gallium sulfide was aluminum sulfide.

Example 3
The production of the inorganic phosphor material was performed in the same manner as in Example 1 except that gallium sulfide was changed to indium sulfide.

Example 4
The same procedure as in Example 1 was performed except that gallium sulfide was changed to boron sulfide in the production of the inorganic phosphor material.

Example 5
The same procedure as in Example 1 was performed except that gallium sulfide was changed to thallium sulfide in the production of the inorganic phosphor material.

Example 6
Except that the time of the ball mill was set to 60 minutes, it was performed in the same manner as in the preparation of the inorganic phosphor material. Similarly, when observed with an electron microscope, 32% of the particles contained a portion having 10 or more planar stacking faults at intervals of 5 nm or less.

Example 7
Except that the first firing was performed for 6 hours, the same procedure as in the production of the inorganic phosphor material was performed. When observed with an electron microscope, the average particle size was 29 μm and the particle size distribution was 43%.

[Comparative Example 1]
Except not adding gallium sulfide, it carried out similarly to preparation of the said inorganic fluorescent material.

[Comparative Example 2]
Except not adding copper sulfide, it carried out similarly to preparation of the said inorganic fluorescent material.

[Comparative Example 3]
Except not adding manganese sulfide, it carried out similarly to preparation of the said inorganic fluorescent material.

  Table 1 shows the results of emission wavelength and emission intensity when an alternating electric field of 1 kHz and 100 V was applied to the device manufactured using the obtained phosphor. The EL emission intensity indicates the relative intensity when the emission intensity of Example 1 is set to 100.

In Examples 1 to 7, the emission of Mn ²⁺ was elongated by the addition of the Group 13 element, and showed emission in the red region of 600 nm or more when the dispersion type EL element was formed. In particular, in Example 6, since the stress application time by the ball mill was extended, the frequency of high-density stacking faults of 10 or more planar stacking faults at intervals of 5 nm or less increased, and the EL emission intensity could be increased. . The main reason for this is thought to be that more Cu ₂ S can be present as an electron generation source due to an increase in stacking faults.
In Example 7, the firing time was longer than in Example 1, so that larger particles grew and the size distribution between the particles also expanded. When the particle size is increased, the surface area is decreased, so that the light emitting area is decreased and the emission intensity is decreased.
On the other hand, in Comparative Example 1 in which the Group 13 element was not added, yellow-orange emission of 580 nm was observed when ZnS was doped with Mn. In Comparative Example 2 in which Cu was not added, no EL light was emitted. This is considered because Cu ₂ S serving as an electron generation source does not exist.
Further, in Comparative Example 3 in which Mn was not added, chlorine such as NaCl or MgCl ₂ added as a flux was doped in ZnS, thereby forming a DA pair with Cu and Cl, and emitting blue-green light. showed that.

  As described above, according to the present invention, it is possible to obtain an inorganic phosphor material that emits red light with a dispersed inorganic EL. It is useful for manufacturing a dispersion-type inorganic EL element that emits white light by combining with other phosphors that emit blue-green EL light as well as red.

1, 8 Sealing film 2 Film base (PET)
3 Indium-tin oxide (transparent electrode)
4 Inorganic phosphor material 5 Phosphor layer 6 Dielectric layer 7 Aluminum electrode

Claims (5)

  An inorganic phosphor having as a base material at least one selected from compounds consisting of at least one selected from Group 12 elements of the Periodic Table and at least one selected from Group 16 elements, or a mixed crystal consisting of two or more. An inorganic phosphor material, characterized in that the host material contains at least one element selected from elements belonging to Group 13 of the periodic table, Cu, and Mn.   The inorganic phosphor material according to claim 1, wherein the element belonging to Group 13 of the periodic table is Al, Ga, or In.   The phosphor material is phosphor particles, and among the total phosphor particles, 20% or more of the particles are particles containing 10 or more planar stacking faults at intervals of 5 nm or less. The inorganic phosphor material according to claim 1 or 2.   4. The inorganic phosphor material according to claim 3, wherein the phosphor particles have an average particle size of 20 μm or less and a variation coefficient of the particle size of 40% or less.   A dispersion type electroluminescent device comprising the light emitting layer containing the inorganic phosphor material according to claim 1.

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