JP2010215787A - Inorganic phosphor particle and distributed electroluminescence element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inorganic phosphor particles having a specific particle size and a coefficient of variation of particle size, emitting light at a specific wavelength, having excellent emission brightness, an improved life and useful for distributed EL element and the distributed EL element using the same. <P>SOLUTION: The inorganic phosphor particles useful for distributed electroluminescence comprise zinc sulfide, have an average particle size of ≥1 μm and <20 μm, a coefficient of variation of particle size of ≥3% and <40%. The emission maximum of electroluminescence of the phosphor exists between 480-520 nm. Preferably the inorganic phosphor particles contain Cu as an activator in the concentration of 0.10-0.16 mol%/mol. The distributed electroluminescence element is obtained by using the inorganic phosphor particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dispersion-type EL element (hereinafter also referred to as an EL element) having electroluminescent (EL) powder particles having high luminance and long life and a light-emitting layer on which the dispersion is applied.

The EL phosphor is a voltage excitation type phosphor, and a dispersion type EL device and a thin film type EL device are known in which the phosphor powder is sandwiched between electrodes and used as a light emitting device. The general shape of a dispersion-type EL element consists of a structure in which phosphor powder is dispersed in a binder with a high dielectric constant, and at least one is sandwiched between two transparent electrodes. Light is emitted by applying an electric field. A light-emitting element manufactured using EL phosphor powder can have a thickness of several millimeters or less, is a surface light emitter, has a number of advantages such as low heat generation and good light emission efficiency. Applications are expected for various interior and exterior lighting, light sources for flat panel displays such as liquid crystal displays, and illumination light sources for large areas.
However, light-emitting devices manufactured using phosphor powder have the disadvantages of lower emission luminance and shorter emission lifetime than light-emitting devices based on other principles, and various improvements have been attempted in the past. I came.

  Furthermore, as a method for increasing the emission luminance, a method using phosphor particles having a small size is known (Patent Documents 1 and 2). When an EL device is configured using phosphor particles having a small size, the number of phosphor particles per unit volume in the light emitting layer can be increased, and as a result, the luminance of the EL device can be increased. However, an EL element using phosphor particles having a small size has a disadvantage that luminance is deteriorated quickly.

  Patent Document 3 discloses that an electrolysis having an average particle diameter of 0.5 to 20 μm, 10 or more stacking faults at an interval of 5 nm or less, copper as a light emission center, and gold, cesium, bismuth, and the like. A luminescent phosphor is disclosed.

JP 2002-235080 A JP 2004-265866 A JP 2006-63317 A

However, there has been no report on the emission wavelength and the lifetime of the EL device with respect to the dispersion type electroluminescence device.
Accordingly, the present invention provides inorganic phosphor particles for a dispersed EL element that emits light at a specific wavelength with a specific average particle size and a particle size variation coefficient, has excellent emission luminance, and has an improved lifetime, and uses the same. It is an object of the present invention to provide a distributed EL element.

  As a result of intensive studies by the present inventors, an inorganic phosphor having an average particle size of 1 μm or more and less than 20 μm, a particle size variation coefficient of 3% or more and less than 40%, and an electroluminescence emission maximum between 480 and 520 nm. As a result, it was found that, when introduced into a dispersion-type electroluminescent element, it was possible to achieve a long lifetime with high luminance, and the present invention was achieved.

That is, the present invention is achieved by the following requirements.
(1) Inorganic phosphor particles used for dispersion type electroluminescence, wherein the inorganic phosphor is made of zinc sulfide, the average particle size of the phosphor particles is 1 μm or more and less than 20 μm, and the variation coefficient of the particle size is 3% or more. An inorganic phosphor particle having an electroluminescence emission maximum of less than 40% between 480 and 520 nm.
(2) The inorganic phosphor particles according to (1), wherein Cu is contained as an activator at a concentration of 0.10 to 0.16 mol% / mol.
(3) The phosphor particles described above (1) or (2), wherein 30% or more of the particles contain 10 or more planar stacking faults at intervals of 5 nm or less. Inorganic phosphor particles.
(4) The inorganic phosphor particles according to any one of (1) to (3), wherein the coactivator of the phosphor particles is selected from Cl, Br, and I.
(5) A dispersion type electroluminescent device using the inorganic phosphor particles according to any one of (1) to (4).
(6) The dispersion-type electroluminescence device according to (5), wherein a red conversion material is contained in any of the layers of the dispersion-type electroluminescence device.
(7) The dispersion type electroluminescence device according to (5), wherein phosphor particles that emit red light separately from the phosphor particles are contained in any of the layers of the dispersion type electroluminescence device.
In the present invention, the phosphor particles mean those that emit light when a voltage is applied.

  The inorganic phosphor particles of the present invention and the dispersion-type electroluminescent device using the same are compatible with both high luminance and long life. Moreover, when trying to obtain white light emission in combination with a red material, it exhibits excellent color reproducibility (color rendering).

The present invention will be described in detail below.
<Phosphor particles>
In the present invention, the inorganic phosphor particles having an emission maximum at 480 to 520 nm are zinc sulfide, the average particle size is 1 μm or more and less than 20 μm, and the variation coefficient of the particle size is 3% or more and less than 40%.

The phosphor particles in the present invention can be formed by a firing method (solid phase method) widely used in the industry. For example, zinc sulfide creates a fine particle powder (usually called raw powder) of 10 nm to 50 nm by a liquid phase method, and uses this as primary particles, that is, a base material. There are two types of zinc sulfide, a high-temperature stable hexagonal system and a low-temperature stable cubic system, and any of them may be used or may be mixed. This is fired in a crucible at a high temperature of 900 ° C. to 1300 ° C. for 30 minutes to 10 hours with both impurities called activator and coactivator, and intermediate phosphor particles are obtained. A preferable firing temperature is 950 ° C. to 1250 ° C., more preferably 1000 ° C. to 1200 ° C., in order to obtain phosphor particles having a low average particle size and a variation coefficient of the particle size of the present invention as described above. Moreover, preferable baking time is 30 minutes-6 hours, More preferably, it is 1 hour-4 hours. Moreover, as a flux, it is preferable to use 20 mass% or more. Furthermore, 30 mass% or more is preferable and 40 mass% or more is more preferable. The ratio of the flux here is represented by the ratio (mass%) of the flux = mass of the flux / (mass of the raw material phosphor primary particles + the mass of the flux). For example, in the case where copper, which is an activator, is mixed in the raw powder in advance, such as a copper-activated zinc sulfide phosphor described later, the activator copper is also integrated with the phosphor raw material powder. In such a case, the mass of the phosphor raw material powder including copper is measured. The mass of the flux may differ from the mass at room temperature and the mass at the firing temperature. For example, barium chloride exists in the state of BaCl ₂ · 2H ₂ O at room temperature, but it is considered that water of hydration is lost at the firing temperature and becomes BaCl ₂ . However, the ratio of the flux here is calculated based on the heavy mass of the flux in a stable state at room temperature.

Next, the obtained intermediate phosphor powder is subjected to a second firing. In the second time, heating (annealing) is performed at a temperature lower than that of the first time at 500 ° C. to 800 ° C. and for a short time of 30 minutes to 3 hours. Thereby, an activator can be concentrated on the below-mentioned stacking fault.
Thereafter, the intermediate phosphor is etched with an acid such as hydrochloric acid to remove the metal oxide adhering to the surface, and the activator adhering to the surface is removed by washing with KCN or the like. Subsequently, drying is performed to obtain an electroluminescent phosphor.
By such a method, particles having an average particle size of 1 μm or more and less than 20 μm and a particle size variation coefficient of 3% or more and less than 40% can be obtained.
For the measurement of the average particle size and the particle size variation coefficient of the phosphor particles of the present invention, for example, a method using laser scattering such as a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba, Ltd. can be used. Here, the average particle size refers to the median diameter.

Cu is suitably used as the activator in the present invention, and the Cu source is not limited, but copper sulfate, copper sulfide, copper chloride, copper nitrate, and the like are used. The amount of copper to be added is not particularly limited, but is 1 × 10 ^{−5 to} 5 × 10 ⁻² mol, preferably 1 × 10 ⁻⁴ to 1 × with respect to 1 mol of the base material (zinc sulfide). ^10-2 mol, More preferably, it is 5 * 10 < ^-4 > -8 * 10 <^-3> mol.

When Cu is used as the activator, the Cu concentration in the inorganic phosphor particles of the present invention is preferably 0.10 to 0.16 mol% / mol Zn, and the Cu concentration is 0.16 mol% / mol Zn or less. The problem that Cu that could not be completely doped in the particles is precipitated on the surface of the particles and the surface is colored is preferable. If it is 0.10 mol% / mol Zn or more, the production amount of the luminescence center is sufficient, which is preferable. The content is more preferably 0.11 to 0.15 mol% / mol Zn, and further preferably 0.120 to 0.140 mol% / mol Zn.
About Cu content, it can adjust by adjusting the mixing amount of Cu source mixed with raw flour.
About the measuring method of Cu content, fluorescent substance particle | grains can be melt | dissolved in hydrochloric acid, nitric acid, and aqua regia, and content can be quantified using ICP analysis (induction plasma emission analysis).

  As the coactivator in the present invention, at least one selected from F, Cl, and Br is preferably used, and Cl and Br are particularly preferable. The addition amount of the coactivator is not particularly limited. In particular, in the case of F, Cl, or Br, the flux also functions as a supply source of the coactivator, so that it is not necessary to newly add.

The phosphor material in the present invention is zinc sulfide. For example, when Cu is used as an activator, generally, Cu in the zinc sulfide phosphor becomes an acceptor, and forms a green emission center called G-Cu by pairing with a donor formed by the coactivator. It is known to do. G-Cu has an emission maximum at 480 to 520 nm. Further, a blue emission center called B-Cu formed by Cu existing between lattices of zinc sulfide is similarly formed, and the emission maximum exists between 440 to 470 nm. That is, two types of emission centers are formed in the zinc sulfide by Cu. When forming G-Cu, Cu occupies the lattice position of Zn in ZnS, and coactivators such as F, Cl and Br occupy the lattice position of S. In the case of B-Cu, since Cu exists between lattices in zinc sulfide, the lattice position of Zn becomes a point defect.
On the other hand, it is known that zinc sulfide generally loses part of sulfur and zinc during firing and easily generates point defects, which affects the performance as a light emitting material. The present invention efficiently generates G-Cu without generating B-Cu, and efficiently fills the point defects with Cu or a co-inactivator by setting the emission wavelength to 480 to 520 nm. It has been found that the production of can be suppressed and a high luminance and a long life can be achieved.
In particular, when the average particle size is in the range of 1 to 20 μm, a general EL phosphor is small with respect to 20 to 30 μm, so that the surface area is large and defects are easily generated. Therefore, it was necessary to generate G-Cu more efficiently. The present invention makes it possible to prevent point defects from being generated by appropriately adjusting the firing conditions and the Cu content.

  Furthermore, in this invention, in order to remove the excess activator, coactivator, and flux which are contained in the intermediate | middle fluorescent substance powder obtained by the said baking, it is preferable to wash | clean with ion-exchange water.

A naturally occurring planar stacking fault (twin crystal structure) exists inside the intermediate phosphor particles obtained by firing. Further, by applying an impact force in a certain range, the density of stacking faults can be greatly increased without destroying the particles. Conventionally known methods for applying an impact force include a method in which intermediate phosphor particles are brought into contact with each other, spheres such as alumina are mixed and mixed (ball mill), or particles are accelerated to collide. In particular, zinc sulfide has two crystal systems, cubic and hexagonal, and the former has a close-packed atomic plane ((111) plane) with a three-layer structure of ABCABC... Vertical close-packed atomic planes form a two-layer structure of ABAB. For this reason, when an impact is applied to the zinc sulfide crystal with a ball mill or the like, slip of the close-packed atomic plane occurs in a cubic system, and when the C plane is removed, ABAB hexagonal crystals are partially formed, and edge dislocations occur. In addition, the AB plane may be reversed to form twins. In general, since impurities in the crystal are concentrated in lattice defect portions, when zinc sulfide having stacking faults is heated and an activator such as copper sulfide is diffused, it precipitates in stacking faults. Since the interface between the deposited portion of the activator and the base zinc sulfide is the center of the electroluminescent luminescent material, the phosphor particles of the present invention have a planar stacking fault of 5 nm or less with a particle number of 30% or more. It is preferable that the particles contain 10 or more particles at intervals. The number of particles containing 10 or more planar stacking faults at intervals of 5 nm or less is more preferably 50% or more, and particularly preferably 80% or more.
The crystal structure of the phosphor particles is not particularly limited, and zinc sulfide may have any ratio of the zinc flash structure (cubic crystal) and the wurtzite structure (hexagonal crystal).
A general description of stacking faults is B.I. It is described in detail in Henderson's translation of Masao Doyama, “Lattice Defects”, Chapter 1 and Chapter 7 Maruzen Co., Ltd. In the case of zinc sulfide, Andrew C. WrightandIanV. F. Viney, PhilosophyMag. B, 2001, Vol. 81, no. 3, p279-p297.
The stacking fault is evaluated by observing a stacked structure appearing on the side surface of the particle (particle surface) when phosphor particles are etched with an acid such as hydrochloric acid.

  Other phosphor formation methods include laser ablation, CVD, plasma, sputtering, resistance heating, electron beam, etc. A liquid phase method such as a method, a precursor thermal decomposition method, a reverse micelle method, a method combining these methods with high-temperature baking, a freeze-drying method, a urea melting method, a spray pyrolysis method, or the like can also be used. .

The phosphor particles of the present invention preferably contain at least one metal element belonging to the second transition series from Group 6 to Group 10. Of these, molybdenum, platinum, and iridium are preferable. These metals are preferably contained in zinc sulfide in the range of 1 × 10 ⁻⁷ mol to 1 × 10 ⁻³ mol with respect to 1 mol of zinc sulfide, and 1 × 10 ⁻⁶ mol to 5 × 10 ⁻⁴ mol. More preferably it is included. These metals are added to deionized water together with zinc sulfide fine powder and a predetermined amount of copper sulfate, made into a slurry, mixed well, dried, and then baked with a coactivator and flux to sulfidize. Although it is preferable to make it contain in a zinc particle, it is also preferable to mix the complex powder containing these metals with a flux, and calcinate using this coactivator and a flux, and to make it contain in a zinc sulfide particle. In any case, any compound containing a metal element to be used can be used as a raw material compound when adding a metal. More preferably, a complex in which oxygen or nitrogen is coordinated to a metal or metal ion is used. It is preferable to use it. The ligand may be an inorganic compound or an organic compound. As a result, it is possible to further improve the luminance and extend the lifetime.

  The phosphor particles may have a non-light emitting shell layer on the surface of the particles. Details of the non-light emitting shell layer are as described in JP-A-2005-283911, [0028] to [0033].

<EL element>
Hereinafter, a dispersion-type electroluminescent element using the inorganic phosphor particles of the present invention (hereinafter also referred to as an EL element of the present invention) will be described.
The dispersion type EL element using the inorganic phosphor particles of the present invention has, for example, at least one light emitting layer containing the inorganic phosphor particles 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.

<Light emitting layer>
When an EL device is produced using the phosphor particles of the present invention, the particles are dispersed in an organic dispersion medium, and the dispersion is applied to form a light emitting 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.
As a method for dispersing the phosphor particles in the binder, a homogenizer, a planetary kneader, a roll kneader, an ultrasonic disperser, or the like can be used.
The blending ratio of the binder and the phosphor particles is preferably such that the content of the phosphor particles in the light emitting layer is 30 to 90% by mass with respect to the entire solid content, and is 60 to 85. It is still more preferable to set it as the ratio used as the mass%. Thereby, the surface of the light emitting layer can be formed smoothly.
As the binder, it is particularly preferable to use a polymer compound in which the hydroxyl group is cyanoethylated in a mass ratio of 20% or more, more preferably 50% or more, in the organic dispersion medium of the entire light emitting layer.

  The thickness of the light emitting layer thus obtained is preferably 20 μm or more and less than 80 μm, more preferably 25 μm or more and less than 75 μm. When the thickness is 20 μm or more, favorable smoothness of the surface of the light emitting layer can be obtained, and when it is less than 80 μm, an electric field can be effectively applied to the phosphor particles, which is preferable. In particular, in the case where a blocking layer described later is provided, a decrease in the initial luminance and a sufficient durability effect can be achieved by reducing the thickness of the insulating film described later and increasing the thickness of the light emitting layer. Is preferable. Furthermore, in order to obtain a good initial luminance, the thickness of the light emitting layer is preferably 70 μm or less.

<Blocking layer>
The EL element of the present invention may have a blocking layer between the transparent electrode and the light emitting layer. Details of this blocking layer are as described in JP-A 2007-12466, [0013] to [0020].

<Insulating layer>
As the insulating layer in the EL element of the present invention, any material can be used as long as it is a material having a high dielectric constant and insulating property and a high breakdown voltage. These are selected from metal oxides and nitrides, such as BaTiO ₃ , KNbO ₃ , LiNbO ₃ , LiTaO ₃ , Ta ₂ O ₃ , BaTa ₂ O ₆ , Y ₂ O ₃ , Al ₂ O ₃ , AlON, etc. . These may be installed as a uniform film, or may be used as a film having a particle structure containing an organic binder. For example, Mat. Res. Bull. As described in Volume 36, page 1065, a film composed of BaTiO ₃ fine particles and BaTiO ₃ sol is used.
The film thickness is desirably 10 μm or more and less than 35 μm. More preferably, they are 12 micrometers or more and less than 33 micrometers, and 15 micrometers or more and less than 31 micrometers are still more preferable. If the film thickness is too thin, dielectric breakdown tends to occur, and if it is too thick, the voltage applied to the light-emitting layer is reduced, which is not preferable because the light emission efficiency is substantially lowered.

Examples of organic binders that can be used for the insulating layer include polymers having a relatively high dielectric constant such as cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, and cyanoethyl cellulose resins, polyethylene, polypropylene, polystyrene resins, silicone resins, epoxy resins, Examples thereof include resins such as vinylidene fluoride. The dielectric constant can be adjusted by appropriately mixing fine particles having a high dielectric constant such as BaTiO ₃ or SrTiO _{3 with} these resins. As a dispersion method, a homogenizer, a planetary kneader, a roll kneader, an ultrasonic disperser, or the like can be used.

<Red material>
In the electroluminescence device of the present invention, it is preferable to produce white light emission to widen the application range. For this purpose, a light emitting material that emits red light in addition to the light emission of zinc sulfide particles having a light emission maximum at 480 to 520 nm is used. The red light emitting material may be either an organic material that absorbs the light emission of zinc sulfide and converts it into red or an inorganic material that exhibits red electroluminescence. The former is particularly preferably an organic fluorescent dye or fluorescent pigment, which may be dispersed in the light emitting layer or dispersed in the insulating layer, and between the light emitting layer and the transparent electrode or the light emitting layer relative to the transparent electrode. It may be located on the opposite side. The latter can be contained in the light-emitting layer in the same manner as the zinc sulfide phosphor particles, or introduced as a red inorganic phosphor material layer separately from the layer containing the zinc sulfide phosphor particles between the transparent electrode and the insulating layer. You can also.
As the phosphor particles emitting red light preferably used in the present invention, the base material is composed of a group II element and a group VI element, like the inorganic phosphor particles which are the zinc sulfide phosphor material of the present invention. It is composed of one or more elements selected from the group and one or more elements selected from the group consisting of Group III elements and Group V elements, and is arbitrarily selected depending on the necessary emission wavelength region . Although it does not specifically limit as an activator, For example, co-activators are group VII elements, such as F, Cl, Br, I, Al, Ga, In, from transition metals, such as Cu and Mn. And so on. Furthermore, it is desirable that rare earth such as Ce, Eu, and Sm is also doped. Specifically, ZnS: Cu, In, CaS: Eu, Ce, etc. correspond to it.

Hereinafter, the red color conversion organic material will be described in detail.
In the electroluminescence device of the present invention, the red emission wavelength during white light emission is preferably 590 nm or more and 650 nm or less. In order to obtain a red emission wavelength included in this range, a red conversion material may be contained in the light emitting layer, placed between the light emitting layer and the transparent electrode, or placed on the opposite side of the light emitting layer around the transparent electrode. However, it is most preferable to contain it in the insulating layer. The insulating layer containing the red color conversion material is preferably a layer in which all of the insulating layers in the electroluminescent element of the present invention contain the red color conversion material. However, the insulating layer in the element is divided into two or more, and one of them. More preferably, the part is a layer containing a red color conversion material. The layer containing the red color conversion material is preferably located between the insulating layer not containing the red color conversion material and the light emitting layer, and the insulating layer not containing the red color conversion material is sandwiched between the insulating layers not containing the red color conversion material. It is also preferable to position them in such a manner.

When the layer containing the red conversion material is positioned between the insulating layer not containing the red conversion material and the light emitting layer, the layer containing the red conversion material is preferably 1 μm or more and 20 μm or less, more preferably 3 μm or more and 17 μm or less. is there. The concentration of the red conversion material in the insulating layer to which the red conversion material is added is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass with respect to dielectric particles represented by BaTiO _3. % To 15% by mass. When the layer containing the red conversion material is positioned so as to be sandwiched between the insulating layers not containing the red conversion material from both sides, the layer containing the red conversion material is preferably 1 μm or more and 20 μm or less, more preferably 3 μm or more and 10 μm or less. It is. The concentration of the red conversion material in the insulating layer to which the red conversion material is added is preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 20% by mass or less, based on the dielectric particles. It is. When the layer containing the red conversion material is positioned so as to be sandwiched between the insulating layers not containing the red conversion material from both sides, the layer containing the red conversion material does not contain dielectric particles, and the high dielectric constant binder and the red conversion material It is also preferable to use only a layer.

  The emission wavelength when the red conversion material used here is in a powder state is preferably 590 nm or more and 750 nm or less, more preferably 600 nm or more and 650 nm or less, and most preferably 605 nm or more and 630 nm or less. is there. This red conversion material is added to the electroluminescence element, and the red emission wavelength at the time of electroluminescence emission is preferably 590 nm or more and 650 nm or less, more preferably 595 nm or more and 630 nm or less, and most preferably Is 600 nm or more and 620 nm or less.

  As a binder for the layer containing the red conversion material, a polymer having a relatively high dielectric constant such as cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose resin, polyethylene, polypropylene, polystyrene resin, silicone resin, epoxy resin, Resins such as vinylidene fluoride are preferred.

As the red color conversion material of the present invention, a fluorescent pigment or a fluorescent dye can be preferably used. Compounds having these luminescence centers are preferably compounds having rhodamine, lactone, xanthene, quinoline, benzothiazole, triethylindoline, perylene, triphenine, dicyanomethylene as the skeleton, and other cyanine dyes, azo dyes, polyphenylene vinylenes. It is also preferable to use a polymer, a disilane oligothienylene polymer, a ruthenium complex, a europium complex, or an erbium complex. These compounds may be used alone or in combination. Further, these compounds may be used after further being dispersed in a polymer or the like. As a fluorescent pigment having an emission maximum in the above range, “SEL-1003” manufactured by Sinloihi can be used.
The fluorescent pigment or fluorescent dye can adjust the maximum emission wavelength within this range by using a filter such as a band reflection filter.

<Transparent electrode>
The transparent electrode is not only a glass substrate, but also a transparent film such as polyethylene terephthalate or triacetyl cellulose base, such as indium / tin oxide (ITO), tin oxide, antimony-doped tin oxide, zinc-doped tin oxide, or zinc oxide. It can be obtained by uniformly depositing and forming a transparent conductive material by a method such as vapor deposition, coating or printing.
Alternatively, a multilayer structure in which a silver thin film is sandwiched between high refractive index layers may be used. Furthermore, a conductive polymer such as a conjugated polymer such as polyaniline or polypyrrole can be preferably used.
These transparent conductive materials are described in “Current Status and Future of Electromagnetic Shielding Materials” published by Toray Research Center, Japanese Patent Laid-Open No. 9-147639, and the like.

  As the transparent electrode, a transparent conductive sheet or conductive polymer obtained by attaching and forming the transparent conductive material to the transparent film, a uniform mesh, a comb-shaped or grid-type metal, and the like It is also preferable to use a transparent conductive sheet in which a conductive surface on which a fine wire structure part of an alloy is arranged is formed to improve the conductivity.

In the case of using the fine wires as described above, copper, silver, nickel, and aluminum are preferably used as the material for the fine wires of the metal or alloy, but depending on the purpose, the above-mentioned transparent conductive material may be used instead of the metal or alloy. It may be used. A material having high electrical conductivity and high thermal conductivity is preferable. The width of the thin line is arbitrary, but is preferably between about 0.1 μm and 1000 μm. The fine wires are preferably arranged at a pitch of 50 μm to 5 cm, and more preferably 100 μm to 1 cm.
The height (thickness) of the fine wire structure is preferably 0.1 μm or more and 10 μm or less. Particularly preferably, it is 0.5 μm or more and 5 μm or less. Either the fine wire structure portion or the transparent conductive film may be exposed on the surface, but as a result, the smoothness (unevenness) of the conductive surface is preferably 5 μm or less. From the viewpoint of adhesion, it is preferably 0.01 μm or more and 5 μm or less. Particularly preferred is 0.05 μm or more and 3 μm or less.

Here, the smoothness (unevenness) of the conductive surface indicates the average amplitude of the unevenness when measuring 5 mm square using a three-dimensional surface roughness meter (for example, manufactured by Tokyo Seimitsu Co., Ltd .; SURFCOM 575A-3DF). For a surface roughness meter that does not reach the resolution, smoothness is obtained by measurement using an STM or an electron microscope.
With regard to the relationship between the width, height, and interval of the fine lines, the width of the fine lines may be determined according to the purpose, but typically it is preferably 1 / 10,000 or more and 1/10 or less of the fine line interval.
The height of the fine line is the same, but a range of 1/100 to 10 times the width of the fine line is preferably used.

  The surface resistivity of the transparent electrode used in the present invention is preferably from 0.1Ω / □ to 100Ω / □, more preferably from 1Ω / □ to 80Ω / □. The surface resistivity of the transparent electrode is a value measured according to the measurement method described in JIS K6911.

When a metal and / or alloy fine wire structure is disposed as the transparent electrode, it is preferable to suppress a decrease in light transmittance. It is preferable to ensure a light transmittance of 90% or more by setting the interval, the width and the height of the thin lines within the above-described ranges.
In the present invention, the light transmittance of the transparent electrode is preferably 70% or more, more preferably 80% or more, and most preferably 90% or more with respect to 550 nm light.

  The transparent electrode preferably transmits 80% or more of light in the wavelength range of 420 nm to 650 nm, more preferably 90% or more, in order to improve luminance and realize white light emission. preferable. In order to realize white light emission, it is more preferable to transmit 80% or more of light in a wavelength region of 380 nm to 680 nm. The light transmittance of the transparent electrode can be measured with a spectrophotometer.

<Back electrode>
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. Furthermore, from the viewpoint of improving durability, it is important that the thermal conductivity of the back electrode is high, and it is preferably 2.0 W / cm · deg or more, particularly 2.5 W / cm · deg or more.
It is also preferable to use a metal sheet or a metal mesh as the back electrode in order to ensure high heat dissipation and electrical conductivity in the periphery of the EL element.

<Manufacturing method>
The method for producing the EL device of the present invention is not particularly limited, but a method as described in detail in, for example, [0046] to [0049] of JP-A No. 2007-12466 can be appropriately employed.

<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].

The present invention is particularly effective in an application in which an EL element is used by emitting light with high luminance (for example, 600 cd / m ² or more). Specifically, the present invention is used in a driving condition in which a voltage of 100 V or more and 500 V or less is applied between the transparent electrode and the back electrode of the EL element, or in a condition of driving with an AC power source having a frequency of 800 Hz or more and 4000 KHz or less. It is valid.

  Examples of the dispersion type EL element of the present invention are shown below, but the dispersion type EL element of the present invention is not limited thereto.

Example 1
Each layer shown below is formed on a 70 μm thick aluminum electrode (back electrode) by applying the respective layer forming coating solutions in the order of a first layer (thickness 30 μm) and a second layer (thickness 55 μm). Further, polyethylene terephthalate (thickness 75 μm) sputtered with indium-tin oxide so as to form a transparent electrode having a thickness of 40 nm is formed so that the transparent electrode side (conductive surface side) faces the aluminum electrode side. The two phosphor layer-containing layers (light-emitting layers) were adjacent to each other and pressed with a 190 ° C. heat roller in a nitrogen atmosphere.

The additive amount of each layer shown below represents the mass per square meter of the EL element.
Each layer was prepared by applying dimethylformamide to a coating solution with adjusted viscosity and then dried at 110 ° C. for 10 hours.

First layer: Insulating layer (without red conversion material)
Cyanoethyl pullulan 14.0g
Cyanoethyl polyvinyl alcohol 10.0g
Barium titanate particles (average sphere equivalent diameter 0.05 μm) 100.0 g
Second layer; light-emitting layer 18.0 g of cyanoethyl pullulan
12.0 g of cyanoethyl polyvinyl alcohol
Phosphor particles 120.0g

The production method and characteristics of the phosphor particles are shown below.
Water was added to 150 g of ZnS fine powder (manufactured by Furuuchi Chemical Co., Ltd., purity 99.999%) and stirred to form a slurry, and an aqueous solution containing 0.538 g of CuSO ₄ .5H ₂ O was added and partially replaced with Cu. (Cu1.4 × 10 ⁻³ mol with respect to 1 mol of ZnS) ZnS raw powder (average particle size 100 nm) was obtained. 4.0 g of S powder was added to 25.0 g of the obtained raw powder, and BaCl ₂ · 2H ₂ O; 4.2 g, MgCl ₂ · 6H ₂ O; 11.2 g, SrCl ₂ · 6H ₂ O as a flux. 9.0 g was added, and calcination was performed at 1200 ° C. for 4 hours in an Ar atmosphere to obtain a phosphor intermediate. The phosphor intermediate was washed with ion-exchanged water 5 times and dried. The obtained intermediate was pulverized with a ball mill for 40 minutes and then annealed at 700 ° C. for 6 hours.
The obtained phosphor particles were washed with a 10% KCN aqueous solution heated to 70 ° C. to remove excess copper (copper sulfide) on the surface, and then washed with water five times to obtain phosphor particles A.

Further, the phosphor particles B were added except that the amount of flux added was BaCl ₂ .2H ₂ O; 2.1 g, MgCl ₂ .6H ₂ O; 4.25 g, SrCl ₂ .6H ₂ O; 1.0 g. It produced similarly to the fluorescent substance particle A.
Further, the phosphor particles C were prepared in the same manner as the phosphor particles A except that the amount of CuSO ₄ .5H ₂ O was 0.231 g.
Phosphor particles D. It was produced in the same manner as the phosphor particle B except that the amount of CuSO ₄ .5H ₂ O was 0.384 g.
The phosphor particle E was produced in the same manner as the phosphor particle A, except that the amount of CuSO ₄ .5H ₂ O was 0.614 g.
The phosphor particles F were produced in the same manner as the phosphor particles A except that the amount of CuSO ₄ .5H ₂ O was 0.481 g.
The phosphor particle G was produced in the same manner as the phosphor particle A, except that the amount of CuSO ₄ .5H ₂ O was 0.384 g.
The phosphor particles H were produced in the same manner as the phosphor particles A, except that the amount of CuSO ₄ .5H ₂ O was 0.652 g.

Table 1 shows the average particle size, particle size variation coefficient, and Cu content of each phosphor particle. In addition, about Cu content, the fluorescent substance particle is melt | dissolved in aqua regia, and it has shown by the percentage with respect to Zn by ICP emission analysis. Further, the average particle size and the particle size variation coefficient were measured using a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba.
Furthermore, each phosphor particle is used to form a coating, a film with a transparent electrode is pressure-bonded, and electrode terminals (aluminum plate having a thickness of 60 μm) are wired to each of the aluminum electrode and the transparent electrode, and then relief printing is performed. The EL device was sealed by thermocompression bonding while vacuum degassing with a GX film, which is a moisture-proof film manufactured by the company. The wavelength of the light emission maximum when driven at 120 V 1.4 kHz is shown.

The phosphor particles used in the EL elements 101, 105 to 108 have both a low average particle size and a small coefficient of variation in the particle size, and the emission maximum is within the scope of the present invention, whereas the EL element 102 has the average particle size and particle size. The EL element 103 had a light emission maximum wavelength, and the EL element 104 had an average particle size, a particle size fluctuation coefficient, and a light emission maximum wavelength outside the scope of the present application.
Further, the EL element 101 is finely adjusted so that the relative brightness of the initial brightness of each element and the same brightness as the light emission brightness of 100 obtained when the EL element 101 is driven at 120 V and 1.4 kHz are the same. Table 2 shows the results when the light emission luminance after continuous driving for 150 hours under the conditions is expressed with the initial luminance as 100.

  The EL elements 101, 105 to 108 not only had higher brightness than others, but also had higher light emission brightness after 150 hours. This is because the other elements have low luminance, and in order to achieve the same luminance as the EL element 101, it is necessary to increase the driving voltage, and an excessive load is applied to the particles. In other words, it can be said that the EL element 101 can obtain the necessary luminance with a smaller load, and is therefore the result of suppressing deterioration.

Example 2
The phosphor particles I were obtained in the same manner as the phosphor A fabrication method except that the ball milling was performed for 120 minutes in the phosphor particle A fabrication method.
The phosphor particles thus obtained were etched with 3N-HCl, and the laminated structure appearing on the particle side surface (particle expression) was observed with an electron microscope under an acceleration voltage condition of 200 kV. As a result, the number ratio of the particles including a portion having 10 or more planar stacking faults at intervals of 5 nm or less was 41% for phosphor particles A, whereas 64% for phosphor particles I. Met.
The same evaluation as in Example 1 was performed on the EL element 201 manufactured using the phosphor particles I in the same manner as in Example 1. As a result, the emission maximum was substantially the same wavelength, but the luminance equivalent to that of the EL element 101 was obtained. The voltage necessary for obtaining the voltage was 112 V, the light emission luminance after 150 hours was 89, and it was confirmed that the voltage was lowered and the life was extended.

Example 3
To a dry powder in which 25 g of zinc sulfide (ZnS) particle powder was added with 1.3 × 10 ⁻³ mol / mol of copper sulfate pentahydrate and 2 × 10 ⁻⁴ mol / mol of iridium chloride with respect to zinc, An aluminum nitrate 3 × 10 ⁻³ mol / mol as an activator, an appropriate amount of ammonium chloride (NH ₃ Cl) powder as a flux, and a magnesium oxide powder in a 10% by mass alumina crucible with respect to the phosphor powder, 1150 The temperature was lowered after baking for 2 hours at ° C. After 5g of the baked particles, 20g of 1mm alumina balls are filled in a 15mmφ glass bottle and ball milled at a rotational speed of 10rpm for 60 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 placed in an alumina crucible and baked at 700 ° C. for 6 hours. 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 entire particles was removed by etching with 6N hydrochloric acid, whereby phosphor particles J were obtained.
Instead of not adding aluminum nitrate, except that the addition 12% respectively coactivator (flux) as NaCl and MgCl ₂ material ZnS powder, the phosphor by making similarly to the phosphor particles J Particle K was obtained.
Table 3 shows the average particle size, the variation coefficient of the particle size, the Cu content, and the stacking fault of each phosphor particle. The stacking fault was viewed as the number ratio of particles including a portion having 10 or more planar stacking faults at intervals of 5 nm or less.

In order to evaluate in the same manner as in Example 1, phosphor elements J and K were used to produce EL elements 301 and 302, respectively.
Similarly to Example 1, Table 4 shows the relative values when the initial luminance of the EL element 301 is 100 and the relative luminance after 150 hours.

  It has been found that the use of Cl rather than Al as the coactivator increases the initial luminance and suppresses deterioration.

Claims (5)

  Inorganic phosphor particles used for dispersive electroluminescence, wherein the inorganic phosphor is made of zinc sulfide, the average particle size of the phosphor particles is 1 μm to less than 20 μm, and the variation coefficient of the particle size is 3% to less than 40% An inorganic phosphor particle characterized in that the electroluminescence emission maximum of the phosphor is between 480 and 520 nm.   The inorganic phosphor particles according to claim 1, wherein Cu is contained as an activator at a concentration of 0.10 to 0.16 mol% / mol.   3. The inorganic phosphor particle according to claim 1, wherein the phosphor particle includes 10 or more particles having a planar stacking fault with an interval of 5 nm or less.   The inorganic phosphor particles according to any one of claims 1 to 3, wherein a coactivator of the phosphor particles is selected from Cl, Br, and I.   A dispersion-type electroluminescent element using the inorganic phosphor particles according to claim 1.