JP2006241183A - Electroluminescent phosphor and el element by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL phosphor satisfying an excellent light-emitting efficiency and brightness jointly and achieving a long life. <P>SOLUTION: This electroluminescent phosphor is characterized by containing ZnS as a parent material, at least Au and Cu as activating agents and at least 1 kind selected from Cl, Br, I and Al as a co-activating agent, having 0.1-20 μm mean particle size of the phosphor and <35% coefficient of variation of the particle size, including ≥30% number of particles based on the total number of phosphor particles, having stacking defects of ≥10 layers by intervals between planes of ≤5 nm mean plane interval of the stacking defect at the inside of the phosphor parent material crystal, and also containing 1×10<SP>-7</SP>to 5×10<SP>-4</SP>mol Au based on 1 mol ZnS, and 1×10<SP>-4</SP>to 1×10<SP>-2</SP>mol Cu based on 1 mol ZnS. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ZnS-based electroluminescence (hereinafter referred to as EL) phosphor and an EL element using the phosphor.

  EL elements can be broadly classified into a dispersion type EL element in which phosphor particles are dispersed in a dispersant and a thin film type EL element in which a phosphor thin film is sandwiched between dielectric layers. Dispersion type EL elements do not need to go through a high-temperature process, so a flexible material structure using a plastic as a substrate is possible, and low-cost EL elements can be manufactured in a relatively simple process without using a vacuum device. It is possible to adjust the emission color of the element by mixing a plurality of phosphor particles having different emission colors, and to easily increase the area. For this reason, the development of a dispersion type EL element as a planar light source has been promoted, and with the recent diversification of various electronic devices, application as a display material for decoration as well as an image display element has been actively performed. ing.

The conventional dispersion-type EL element has a problem that when it emits light with high luminance, the light emission efficiency is low and the durability is poor (because it generates a lot of heat). As a technique for achieving high durability, Patent Document 1 describes that gold is contained as a second coactivator. However, in this prior art, both luminance and light emission efficiency are lowered, so that high luminance is insufficient for realizing high light emission efficiency at a level that can withstand practical use, and therefore, durability is insufficient at high luminance. Moreover, as a prior art for achieving high brightness, Patent Document 2 and Patent Document 3 describe reducing the content of an alkaline earth metal element used as a crystal growth agent (flux). That alone is insufficient to achieve both high brightness and luminous efficiency. Patent Document 4 describes a technique for improving the light emission efficiency by controlling the thickness of the light emitting layer in the EL element. However, this alone is not sufficient for achieving both high luminance and light emission efficiency. there were. In the above prior art, it was impossible to achieve both high luminance and luminous efficiency.
Japanese Patent No. 2999458 JP 2000-136381 A JP 2003-201447 A Japanese Patent Laid-Open No. 3-138890

  Therefore, an object of the present invention is to provide an EL phosphor that achieves both excellent luminous efficiency and luminance and achieves a long lifetime.

As a result of intensive studies, we have added a small amount of gold to phosphor particles with a small particle size variation coefficient and a high stacking fault introduction rate, and a large amount of copper as an activator. It has been found that by selecting this region, the luminous efficiency and the luminance can be achieved at the highest level. In particular, it is preferable to add platinum together with gold. Furthermore, it has been found that the EL element using the phosphor particles can achieve the highest luminous efficiency and brightness at the highest level by selecting a region of 40 μm to 100 μm as the thickness of the phosphor layer.
That is, the present invention is as follows.

(1) An electroluminescent phosphor containing ZnS as a base, containing at least Au and Cu as activators, and containing at least one selected from Cl, Br, I and Al as coactivators. The average particle size of the phosphor is 0.1 to 20 μm, the coefficient of variation of the particle size is less than 35%, and the average plane spacing of stacking faults inside the phosphor host crystal is 10 nm or more with a plane spacing of 5 nm or less The number of particles having stacking faults of 30% or more of the total number of phosphor particles, and 1 × 10 ^{−7 to} 5 × 10 ⁻⁴ mol of Au with respect to 1 mol of ZnS, and with respect to 1 mol of ZnS An electroluminescent phosphor containing 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol of Cu.
(2) The electroluminescent phosphor as described in (1) above, wherein the average particle size of the phosphor is 15 to 20 μm.
(3) The electroluminescent phosphor as described in (1) or (2) above, which contains 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol of Pt with respect to 1 mol of ZnS.
(4) The electro according to any one of (1) to (3) above, wherein the total content of alkaline earth metal elements (Mg, Ca, Sr, Ba) is 0.075% by mass or less. Luminescent phosphor.

(5) An electroluminescent device comprising a light-emitting layer containing the electroluminescent phosphor according to any one of (1) to (4) above.
(6) The electroluminescent element as described in (5) above, wherein the thickness of the light emitting layer is 40 μm to 100 μm.
(7) The dispersion type electroluminescent device as described in (5) or (6) above, wherein at least one intermediate layer is provided between the transparent electrode and the phosphor layer.
(8) Any of the above (5) to (7), wherein the intermediate layer is an organic polymer compound, an inorganic compound, or a composite thereof, and the intermediate layer has a thickness in the range of 10 nm to 100 μm. A dispersion type electroluminescent device according to claim 1.

  As a result of various investigations, the present inventors have found that specific phosphor particles, that is, phosphors having a particle size of 0.1 to 20 μm, a small coefficient of variation, and a structure in which the inside of the particle is planar and has many stacking faults. In the particles, by adding gold to the phosphor particles and adding a large amount of copper, it has been found that the effects of high luminous efficiency, high brightness, and long life are greatly improved, and the present invention has been achieved. is there. Furthermore, it has been found that by adding platinum to the phosphor particles, the effects of high luminous efficiency, high luminance, and long life are significantly improved. Furthermore, it has been found that the effect of increasing the light emission efficiency and extending the lifetime is remarkably improved by applying the phosphor particles to an EL element having a light emitting layer thickness of 40 to 100 μm. It has been found that the addition of copper and gold is particularly effective in increasing the luminous efficiency of phosphor particles having a particle size of 15 to 20 μm. Therefore, by combining these techniques, the overall high luminous efficiency and high efficiency can be achieved. It is estimated that each technology contributes very efficiently to brightness and longevity.

  According to the EL phosphor of the present invention, high-efficiency EL emission is exhibited at high luminance, and the durability is remarkably improved. In addition, the EL phosphor with a small size and a narrow particle size distribution according to the present invention has good dispersibility and can form a uniform phosphor layer, so that the roughness of light emission (granularity) is dramatically improved. It is ideal for high-quality transmission photography and inkjet transmission illumination.

Hereinafter, the EL phosphor of the present invention and the EL element using the same will be described in detail.
[EL phosphor]
(ZnS EL phosphor core particles)
The average particle size of the ZnS-based phosphor core particles used in the EL phosphor of the present invention is in the range of 0.1 to 20 μm. Preferably it is 15-20 micrometers. Further, the variation coefficient of the particle size is less than 35%, and more preferably less than 30%. Accordingly, the dispersibility of the EL phosphor particles and the filling rate of the EL phosphor particles in the phosphor layer are improved, and the light emission roughness (granularity) of the EL element can be improved.

  In addition, in the inside of the particles, particles having a stacking fault of 10 layers or more with an average spacing of stacking faults of 5 nm or less are 30% or more of all phosphor particles. Preferably, the particles are present at 50% or more, more preferably 70% or more. It is preferable to have a structure with many planar stacking faults because the EL light emission efficiency can be increased. Further, in the EL phosphor of the present invention, the total content of alkaline earth metal elements (Mg, Ca, Sr, Ba) is 0.075% by mass or less, preferably 0.07% by mass or less, more preferably 0. 0.05% by mass or less, particularly preferably 0.01% by mass or less. The smaller the total content of alkaline earth metal elements, the greater the efficiency of light emission and the longer the lifetime, coupled with the reduction in particle size.

The EL phosphor core particles of the present invention can be obtained, for example, by the following method.
Commercially available high-purity ZnS can be used as a raw material for the EL phosphor. The purity of usable ZnS is preferably 99.9% or more, and more preferably 99.99% or more. As impurities, it is preferable not to contain 10 ppm or more of a metal element such as Fe, Ni, Co, Cr, or the like that forms a deep level in the EL phosphor. Although there is no restriction | limiting in the particle size of ZnS used as a raw material, in order to adjust the particle size of EL fluorescent substance by baking, the range of 0.01-5 micrometers is preferable and 0.05-1 micrometer is more preferable. Furthermore, the crystallite size calculated from the half width of the diffraction peak of X-ray diffraction is preferably in the range of 1 to 50 nm, and more preferably 10 to 30 nm in order to obtain high luminance. Such a ZnS raw material can be obtained by introducing H ₂ S gas into a Zn aqueous solution, and it is desirable to appropriately select conditions such as Zn salt concentration, reaction pH, H ₂ S gas introduction rate, temperature, etc. It is preferable to obtain a ZnS raw material.

In the present invention, at least Cu is added to the ZnS raw material as an activator. The amount of Cu added is preferably in the range of 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol and more preferably 5 × 10 ^{−4 to} 5 × 10 ⁻³ mol with respect to 1 mol of ZnS. In order to add Cu as an activator, for example, a CuS aqueous solution such as CuSO ₄ or Cu (NO ₃ ) ₂ is added to a suspension in which ZnS particles are dispersed in water to add ZnS particle surfaces. A precursor in which Cu _x S is deposited is prepared. In the present invention, Au is further added as an activator. When adding Au, an Au compound such as chloride, chlorate, or the like is added to the suspension. The suspension is preferably stirred with a magnetic stirrer, impeller stirrer, etc. so that all ZnS particles move in the suspension, and the addition of the Cu and Au compound aqueous solution is appropriately performed with a dropper, beaker, etc. Although it can be added, use of a syringe pump, a tube pump, an orifice, or the like capable of controlling the addition rate is more preferable in terms of uniformity of addition of the activator. The suspension after the reaction is preferably washed several times with distilled water or ion-exchanged water in order to remove ZnSO ₄ and Zn (NO ₃ ) ₂ which are by-products. The particles are recovered from the suspension by solid-liquid separation by a method such as decantation, suction filtration, ultrafiltration, and centrifugal separation, and then 80 to 500 in a dryer such as a hot air dryer or a vacuum dryer. It is preferable to dry at a temperature of 0 ° C. for about 0.5 to 24 hours. In order to control the atmosphere in the subsequent firing step, the moisture content of the precursor after drying is preferably 1% by mass or less, and more preferably 0.1% by mass or less. When the amount of water in the raw material is large, H ₂ S, SO _x , O ₂ , etc. are generated by the reaction, decomposition, etc. of the water and the raw material by firing, and it becomes difficult to keep the atmosphere during firing constant.

  Since it is also preferable to use a precursor in which an activator or an additive is uniformly added to the ZnS crystal, a hydrothermal synthesis method, a uniform precipitation method, or a spray pyrolysis method can also be used. In either method, a precursor in which the activator or additive is incorporated into the ZnS is obtained by reacting ZnS from a state where the Zn salt and the activator or additive salt are dissolved in the solvent. Is preferable.

By adding Au, for example, it is presumed that the deterioration of Cu _x S crystal, which is an electron generation source of EL phosphor, can be suppressed, and in combination with the above-mentioned means for increasing the luminous efficiency and lifetime of the present invention, Furthermore, it has been found that it contributes significantly to significantly higher luminous efficiency and longer life. This effect is particularly remarkable in an EL phosphor to which a large amount of Cu is added as an activator.

Further, the effect of Au activation is particularly remarkable when the average particle size of the phosphor is 15 to 20 μm. When the average particle size is 15 to 20 μm, it is possible to increase the amount of Au added as compared with the case where the average particle size is smaller than 15 μm. As a result, the effect of high luminous efficiency and long life due to Au is achieved. Estimated to be significant. On the other hand, when the average particle size of the phosphor is larger than 20 μm, the effect of decreasing the light emission efficiency due to the increase in particle size is greater than the effect of improving the light emission efficiency due to the addition of Au. Presumed.
The addition amount of Au is preferably added in the range of 1 × ¹⁰ -7 ~5 × ^{10 -4} mol of Au relative ZnS1 mol, more preferably 5 × ¹⁰ -7 ~1 × ^{10 -4} mol.

Further, by adding Pt, the effect of further improving luminous efficiency and luminance can be obtained. Pt is preferably contained in zinc sulfide in the range of 1 × 10 ⁻⁷ mol to 1 × 10 ⁻³ mol, more preferably 1 × 10 ⁻⁶ mol to 5 × 10 ⁻⁴ mol per mol of zinc sulfide. It is preferable that a mole is contained.

  In addition to these activators and coactivators, it is also preferable to add Sb, Bi and / or Cs as additives.

  These metals can be added to deionized water together with zinc sulfide powder and a predetermined amount of copper sulfate, mixed in a slurry form, dried, and then fired with flux before being added to zinc sulfide particles. Although it is preferable, it is also preferable that the complex powder containing these metals is mixed with a flux and calcined using this flux to be contained in zinc sulfide particles. 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.

In the present invention, at least one selected from Cl, Br, I and Al is used as the coactivator. The addition amount of the coactivator is preferably the same amount as the activator. These coactivators are introduced from a flux described later, but in the case of Al, it is necessary to add them separately as a compound such as Al (NO ₃ ) ₃ .

  In addition, a phosphor that emits red light by the light emitted from the ZnS phosphor for whitening is included in the ZnS phosphor separately, but blue-green light is suitable for emitting red light by the phosphor emitting red. ing. When gold is contained, the emission wavelength shifts to the blue-green side, so it has been found that the inclusion of gold is effective for improving the color rendering properties of the illuminant.

The EL phosphor can be baked by a solid phase reaction similar to the conventional method. First, ZnS particles containing an activator and additives are mixed with an alkaline earth metal compound such as an alkaline earth metal halide as a flux (crystal growth agent) that also serves as a supply source of the coactivator. If necessary, other fluxes such as alkali metal halides, ammonium halides, zinc halides, and coactivators are mixed with an Al compound. When Cs is introduced as an additive, a halide of Cs is further added and mixed. In the present invention, alkali metal halides and alkaline earth metal halides can be preferably used, and chlorides thereof are more preferable. Specifically, NaCl, MgCl ₂ , SrCl ₂ , BaCl ₂ , and the like are particularly preferable. In order to obtain a small-sized EL phosphor, it is most preferable that at least SrCl ₂ is included in a part of the flux. When Cs is added, a halide of Cs is used as a flux. At this time, since there are many substances that easily absorb moisture, the flux is preferably dried before mixing, and is dried at 80 to 200 ° C. for 0.5 to 24 hours using a hot air dryer or a vacuum dryer. It is preferable. Furthermore, when adding Au, you may mix Au compounds, such as a chloride and a chlorate, here.

  These mixing may be dry mixing using a mortar, turbula mixer, V cone mixer, ball mill, jet mill, etc., or once added with distilled water or ion exchange water to form a suspension or paste, By drying, the precursor and the flux can also be mixed uniformly. The mixing time varies depending on the mixing method, but if it is too short, the mixing becomes insufficient, and if it is too long, the raw material reabsorbs moisture, so 0.2 to 3 hours are preferable. In order to avoid reabsorption, it is also preferable to mix in a dry atmosphere.

The addition amount of the flux is preferably in the range of 1 to 80% by mass of the mixture, more preferably 10 to 70% by mass, and particularly preferably 20 to 60% by mass. Within this range, the crystal growth can be sufficiently advanced without reducing the yield of the EL phosphor or generating a corrosive toxic gas. The mixture is then filled into a crucible. The crucible to be used is preferably a ceramic crucible such as alumina, silica, zirconia, silicon nitride, silicon carbide or the like. Filling the crucible with the mixture is preferably as dense as possible using a tap method or a vibrator, preferably 50 to 100% by volume, more preferably 80 to 95% by volume of the crucible volume. The crucible is preferably covered with a lid, and the contact portion between the crucible and the lid is preferably rubbed to improve confidentiality. In order to stabilize the atmosphere in the crucible, it is preferable to combine a larger crucible on the outside of the crucible filled with the mixture to stabilize the atmosphere in the crucible. In the space formed by the multiple structure, ZnS, carbon, sulfur, etc. It is preferable to arrange an antioxidant, an atmosphere creating substance such as MgCl ₂ , NH ₄ Cl, or a mixture thereof.

  The mixture filled in the crucible is fired using a muffle furnace, a tube furnace, an image furnace, a continuous furnace, or the like using electricity or gas as a heat source. The crucible is arranged in the soaking zone of the furnace, and the soaking zone is preferably in the range of ± 50 ° C., more preferably in the range of ± 20 ° C. with respect to the set firing temperature. The firing temperature is preferably in the range of 900 to 1300 ° C., more preferably 1100 to 1200 ° C., so that crystal growth proceeds sufficiently and the activator and additives are uniformly diffused in ZnS. Similarly, the firing time is preferably in the range of 30 minutes to 12 hours, more preferably 1 to 6 hours. At this time, the temperature rising rate of the furnace is preferably in the range of 100 to 2000 ° C./h, more preferably 300 to 800 ° C./h. The cooling rate is usually performed by natural cooling, but is preferably controlled in the range of 10 to 10,000 ° C./h. When the temperature drop rate is fast, the temperature drop rate can be controlled by introducing cold air into the furnace or water cooling. In order to control firing more precisely, it is also preferable to select a step-like firing pattern. The firing atmosphere is an oxidizing atmosphere such as air or oxygen, an inert atmosphere such as nitrogen or argon, a reducing atmosphere such as a hydrogen-nitrogen mixed atmosphere or a carbon-oxygen mixed atmosphere, hydrogen sulfide, carbon disulfide, or the like. Can be used. When using a tube furnace or the like, a boat-shaped container can be used instead of a crucible.

In order to remove the fired mixture from the crucible and remove excess flux, reaction by-products, ZnO formed by oxidation of ZnS, and the like, it is preferable to sufficiently repeat acid cleaning and pure water cleaning. The acid used for the acid cleaning can be HCl, HNO ₃ , H ₂ SO ₄ , etc., and the acid concentration is preferably in the range of 0.01 to 10M, more preferably 0.05 to 1M. It is preferable that the washing | cleaning liquid used for an acid washing | cleaning and water washing | cleaning uses the quantity of 1-100 times the mass of the mixture to process. The temperature of the cleaning liquid may be room temperature, but it is preferable to keep the temperature in the range of 10 to 90 ° C. The mixture is put into a cleaning solution and stirred with a magnetic stirrer, impeller stirrer, ultrasonic cleaner, etc. so that all particles in the suspension move.
Thereby, the total content of the alkaline earth metal of the present invention can be 0.075% by mass or less, which is preferable.

  The washed particles are solid-liquid separated by suction filtration, ultrafiltration, centrifugation, etc., and then dried at 80 to 500 ° C. for 0.5 to 24 hours using a hot air dryer, vacuum dryer, etc. An intermediate phosphor is obtained in which most of the particles have wurtzite crystals. Since the average particle size of the intermediate phosphor is substantially equal to the average particle size of the EL phosphor, the average particle size of the intermediate phosphor is in the range of 0.1 to 20 μm, and preferably 15 to 20 μm. Similarly, the coefficient of variation of the particle size of the intermediate phosphor is also less than 35%, preferably less than 30%.

  Next, it is more preferable that the fired intermediate phosphor is refired after applying stress to increase the density of stacking faults and increase the luminance. To apply stress to the intermediate phosphor particles, ball milling, ultrasonic waves, hydrostatic pressure, rubber press, etc. can be used, and in any case, apply uniformly to all particles with a load that does not destroy the intermediate phosphor particles. Is preferred. In particular, it is preferable to use a dry or wet ball mill for applying stress. 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. If the ball diameter is too small, separation from the processed intermediate phosphor particles becomes difficult. If the ball diameter is too large, the stress becomes large and the intermediate phosphor particles are crushed or uniform stress application becomes difficult. 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-1 hour are more preferable. These conditions are preferably combined appropriately from the luminance and lifetime of the EL phosphor.

  In the case of a wet ball mill, an organic solvent such as alcohols and ketones can be used in addition to water as a solvent. 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 that is just filled. When the amount of the solvent to be added is small, the mixture does not flow. When the amount is too large, it is difficult to apply uniform stress. 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 a container, or the like can also be used.
Finally, the intermediate phosphor subjected to stress by a ball mill is separated from the ball using a dry sieve, wet sieve, etc., and 0.5 to 80 ° C. using a hot air dryer, vacuum dryer, etc. Dry for ~ 24 hours.

Subsequently, the stressed intermediate phosphor is filled in the crucible in the same manner as in the firing step, and refired in the same furnace as in the firing step. When using a tube furnace, a boat can also be used. At this time, addition of a compound of Sb or Bi is also preferable because it improves the life of the EL phosphor. These additives may be mixed with the intermediate phosphor by a compound such as a halide, or may be separated from the intermediate phosphor and sublimated at a temperature by re-firing to act as an atmosphere. The addition amount is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol with respect to 1 mol of ZnS. In the case of mixing, the same mixing method as in the above baking step can be used. Furthermore, the activator and flux can be added again as necessary. The range of 400-900 degreeC is preferable and, as for the firing temperature of rebaking, 500-800 degreeC is more preferable. The conditions similar to the above-mentioned baking process can be utilized for the baking time of refiring, the temperature increase rate, the cooling rate, and the atmosphere. As a result, 70% by mass or more of the particles are converted to zinc blende type crystals.

Next, it is preferable to perform acid etching in order to remove the ZnO layer on the particle surface generated by refiring and the surface layer having many crystal disturbances and distortions. The acid etching can be performed by the same method as the acid cleaning after the baking step described above, but the acid concentration of the acid cleaning is preferably in the range of 1 to 10M, more preferably 1 to 7M. After the acid etching, washing with water is repeated in the same manner as described above to remove the acid and the dissolved salt. Furthermore, when Cu is used as an activator, excess Cu compounds are precipitated on the particle surface, so that cleaning with a Cu cleaning solution such as acetic acid, cyanide, ammonia, ammonium sulfide, Cu chelating agent, etc. It is preferable to repeat washing with water. The concentration of the Cu cleaning solution is preferably cleaned in an amount larger than the amount (stoichiometric ratio) necessary to dissolve the added Cu, and more specifically 2 to 100 times the amount is more preferable. In order to enhance the cleaning effect, it is also preferable to add an oxidizing agent such as H ₂ O ₂ to the Cu cleaning liquid. The washed particles are subjected to solid-liquid separation in the same manner as described above, and dried at 80 to 500 ° C. for 0.5 to 24 hours using a hot air dryer, a vacuum dryer, or the like.

  Finally, using a dry sieve or the like, the coarse particles and the agglomerated particles are removed, the average particle size is 0.1 to 20 μm, the variation coefficient of the particle size distribution is less than 35%, and the stacking fault with a surface interval of 5 nm or less. ZnS-based EL phosphors having 10% or more of particles containing 30% or more of the total particles can be obtained.

[Formation of coating layer]
The EL phosphor is decomposed by moisture invading from the external environment and moisture remaining in the EL element to cause luminance deterioration, or a transparent electrode layer such as ITO by S ions, Cl ions, etc. eluted from the EL phosphor particles. Therefore, it is preferable to form a coating layer having an average film thickness of 0.01 to 1 μm on the entire particle surface of the EL phosphor, and the average film thickness is 0.05 to 0.5 μm. It is more preferable. A film thickness of 0.01 μm or less is not preferable because moisture resistance and ion barrier properties are low, and it tends to cause a decrease in luminance of the EL phosphor and corrosion of the transparent electrode layer, and an electric field strength to the EL phosphor particles is 1 μm or more. Is not preferable because it tends to cause a decrease in luminance and an increase in the light emission threshold voltage. The ratio of the average film thickness of the coating layer to the average particle size of the particles is preferably in the range of 0.002 to 0.05. The coating layer preferably has a film thickness suitable for the average particle size of the particles. For example, when a 1 μm coating layer is formed on 1 μm particles, it is not preferable because the electric field strength on the particles tends to be significantly reduced. .

As the composition of the coating layer, oxides, nitrides, hydroxides, fluorides, phosphates, diamond-like carbon, organic compounds, and the like can be used. Use of a mixture, mixed crystal, multilayer film, or the like is also preferable. . _{Specifically, SiO 2, Al 2 O 3} , TiO 2, ZrO 2, HfO 2, Ta 2 O 5, Y 2 O 3, La 2 O 3, CeO 2, BaTiO 3, SrTiO 3, PZT, Si 3 N ₄ , AlN, Al (OH) ₃ , MgF ₂ , CaF ₂ , Mg ₃ (PO ₄ ) ₂ , Ca ₃ (PO ₄ ) ₂ , Sr ₃ (PO ₄ ) ₂ , Ba ₃ (PO ₄ ) ₂ , fluorine Resins are preferred.

  Further, the coating layer is preferably continuous without pinholes or cracks in order to obtain sufficient moisture resistance and ion barrier properties. Such a coating layer can be formed by using a liquid phase synthesis method such as a sol-gel method, a precipitation method, etc., but a CVD method using a fluidized bed, a stirring bed, a vibrating bed, a rolling bed, etc., plasma More preferably, it is formed by a CVD method, a sputtering method, a mechanofusion method, or the like, and it is particularly preferable to use a fluidized bed in terms of the continuity of the coating layer.

[EL element]
The EL element of the present invention has a configuration in which at least a transparent electrode, a phosphor layer containing EL phosphor particles, a dielectric layer, and a back electrode are laminated.

[Production of EL element]
The above EL element can be obtained, for example, by the following method.
As an environment for manufacturing the EL element, temperature, humidity, dew point, cleanliness, etc. were controlled in order to prevent deterioration of the initial brightness and life of the EL element due to moisture and deterioration of quality due to mixing of dust, etc. It is preferable to carry out at the place. As temperature, 20-25 degreeC is preferable. The humidity is preferably 58% RH or less at 20 ° C., 44% RH or less at 25 ° C., 10 g / m ³ or less in absolute humidity, and the dew point is preferably less than 10 ° C. The degree of clean is preferably 10000 or less, more preferably 1000 or less.

First, prepare the materials to be used. The EL phosphor particles used for the phosphor layer and the dielectric particles used for the dielectric layer are dried. The dielectric particles are selected from metal oxides and 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 can be preferably used. In particular, BaTiO ₃ and SrTiO ₃ having a high dielectric constant can be preferably used. The dielectric particles preferably have an average particle size smaller than that of the EL phosphor particles, specifically, a range of 1/1000 to 1/10 of the average particle size of the EL phosphor particles, or 0.01 to 1 μm. The range of is preferable. The EL phosphor particles and the dielectric particles are dried at 80 to 500 ° C. for 0.5 to 24 hours using a hot air dryer, a vacuum dryer, etc., and the moisture content is preferably 1% by mass or less, more preferably. Is dried to 0.1% by mass or less. Similarly, the binder used for the phosphor layer and the dielectric layer is dried. As the phosphor layer, a layer in which EL phosphor particles are dispersed in a binder can be used. As the binder, a resin such as polyethylene, polypropylene, polystyrene resin, silicone resin, epoxy resin, vinylidene fluoride can be used. A polymer having a high dielectric constant can be used more preferably. When drying the binder, since the softening temperature is low, vacuum drying at a low temperature is preferably carried out for a long time, and it is preferable to dry at 50 to 150 ° C. for 2 to 24 hours. Organic solvents such as acetone, MEK, DMF, butyl acetate, and acetonitrile that dissolve the binder are preferably dehydrated with molecular sieves. The dried binder is dissolved in a dehydrated organic solvent at a concentration of 5 to 70% by mass using a homogenizer, a planetary kneader, a ball mill, or the like to prepare a binder solution. The binder solution is preferably defoamed by a method such as stationary defoaming, vacuum defoaming, and centrifugal defoaming, and then filtered using a filter cloth or filter paper in order to remove dust, etc. . Further, the binder solution can be stored for a long time in a closed container such as a polyethylene container.

  Next, an EL phosphor particle dispersion and a dielectric particle dispersion are prepared. The EL phosphor particle dispersion is prepared by adding the EL phosphor particles to the binder solution and dispersing with a homogenizer, planetary kneader, roll kneader, ultrasonic disperser ball mill, rotor mixer, or the like. . Since the EL phosphor particles are deteriorated by mechanical stress, it is preferable to select a dispersion method in which the EL phosphor particles and the binder are compatible with the mechanical stress being kept to a minimum. At this time, the ratio of the EL phosphor particles to the binder is preferably in the range of 1 to 20 parts by mass of the EL phosphor particles with respect to 1 part by mass of the binder in order to improve the luminance of the EL element. 10 mass parts is more preferable, and 4-7 mass parts is especially preferable. If the ratio of the EL phosphor becomes too large, voids are easily formed in the phosphor layer, which causes a decrease in luminance and dielectric breakdown, which is not preferable. Furthermore, the dielectric constant can be adjusted by mixing dielectric particles in the range of 0 to 10% by mass with respect to the EL phosphor. The dispersion time varies depending on the amount of the dispersion to be dispersed and the disperser used, but is preferably in the range of 0.5 to 72 hours. Usually, the larger the amount of the dispersion, the longer the dispersion time. The EL phosphor particle dispersion is adjusted in viscosity using the same organic solvent used for the binder solution. The viscosity of the EL phosphor particle dispersion measured at 16 ° C. varies depending on the coating method described later, but is preferably in the range of 0.01 to 10 Pa · s, more preferably 0.1 to 5 Pa · s. When the viscosity of the EL phosphor particle dispersion is too low, film quality deterioration such as coating film thickness unevenness and smoothness is likely to occur, and the EL phosphor particles are separated and settled over time after dispersion. Sometimes. On the other hand, when the viscosity of the EL phosphor particle dispersion is too high, it may be difficult to apply in the high-speed region, so it is preferable to be within the above range. The EL phosphor particle dispersion liquid whose viscosity has been adjusted is preferably degassed and filtered as described above. Similarly, a dielectric particle dispersion is prepared. Since the dielectric particles have a particle size smaller than that of the EL phosphor particles, the dispersion time is preferably longer than that of the EL phosphor particle dispersion.

  The phosphor layer can be formed by applying the EL phosphor particle dispersion. Formed by continuously applying a dry film thickness of the coating film in the range of 0.5 to 100 μm on a transparent electrode layer described later or a laminate obtained by laminating a dielectric layer on a back electrode described later. It is preferable to do. At this time, the film thickness variation of the phosphor layer is preferably 10% or less, and more preferably 5% or less in order to suppress luminance unevenness of the EL element. The thickness of the phosphor layer is preferably 40 μm to 100 μm and more preferably 50 to 80 μm when the phosphor particles are applied to the phosphor layer from the viewpoint of achieving both luminous efficiency and luminous efficiency. With the above phosphor layer thickness, it is possible to reduce the power consumption when driving with the same brightness, so it is possible to reduce heat generation due to light emission, and to suppress deterioration of the EL element due to heat generation, An EL element having excellent durability can be obtained.

  The phosphor layer can be coated with a general coating machine, but it is preferable to use a slide coater, an extrusion coater, a doctor blade coater, a dip coater, or the like. The slide coater, extrusion coater, and dip coater are suitable for applying a dispersion having a relatively low viscosity of 0.01 to 1 Pa · s at a high speed, and the doctor blade coater has a high viscosity of 0.5 to 10 Pa · s. It can also be used for dispersion liquids. The coating speed is preferably in the range of 0.1 to 200 m / min, more preferably 0.5 to 50 m / min, in any of the coating methods. When the coating length is long and the coating time is long, the coater and the liquid reservoir are cooled to 25 ° C. or less by water cooling or the like, more preferably 20 ° C. in order to prevent the dispersion burr in the coater and evaporation of the solvent. It is preferable to cool below or attach a cover around the coater to fill the solvent atmosphere at a high concentration to prevent evaporation of the solvent.

  Each of the aforementioned layers is preferably formed as 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 present invention, since the binder ratio of each layer is high, when it is rapidly dried, only the surface is dried and convection is generated in the coating film, so-called Benard cell is likely to occur, and blister failure occurs due to rapid expansion of the solvent. It becomes easy and the uniformity of a coating film is remarkably impaired. On the other hand, if the final drying temperature is low, the solvent remains in each layer, which affects the subsequent steps for forming an EL element such as a moisture-proof film laminating step. Therefore, it is preferable that the drying step is performed slowly at a constant rate drying step and performed at a temperature sufficient for the solvent to dry. As a method of slowly performing the constant rate drying process, it is preferable to divide the drying chamber in which the base travels into several zones and gradually increase the drying temperature after the coating process is completed. Further, the temperature can be raised to a temperature required for the polymerization and curing of the binder. Specifically, the drying temperature is preferably in the range of 50 to 200 ° C, more preferably 80 to 150 ° C. Finally, the dried laminate is cooled and wound up.

  In the EL device of the present invention, a dielectric layer is provided adjacent to the phosphor layer described above. The dielectric layer is preferably disposed adjacent to the phosphor layer between the phosphor layer and the back electrode. The dielectric layer can be formed using any material as long as it is a dielectric material having a high dielectric constant and insulating properties and a high dielectric breakdown voltage. Such a material may be installed as a thin film crystal layer, or may be used as a film having a particle structure formed by coating. Further, it may be provided on one side of the phosphor layer, and is preferably provided on both sides of the phosphor 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 vacuum deposition, or a sol-gel film using an alkoxide such as Ba or Sr. In this case, the thickness of the film is Usually in the range of 0.1 to 10 μm.

  In the case of a dielectric layer to be applied and formed, a dielectric layer is formed on a back electrode described later or a laminate obtained by laminating a phosphor layer on a transparent electrode layer, and the dry film thickness of the coating film is 0.5 to 50 μm. It is preferable to form by coating continuously so as to be in the range, and more preferably 30 μm or less. At this time, the film thickness variation of the dielectric layer is preferably 10% or less, and particularly preferably 5% or less. The viscosity of the dielectric particle dispersion varies depending on the coating method, but is preferably in the range of 0.01 to 10 Pa · s, more preferably 0.1 to 5 Pa · s. When the viscosity of the dielectric particle dispersion is too low, uneven coating film thickness is likely to occur, and the dielectric particles may separate and settle over time after dispersion. On the other hand, when the viscosity of the dielectric particle dispersion is too high, it may be difficult to apply in a high speed region, so it is preferable to be within the above range. When the dielectric layer is formed by coating, it is preferable to use the same coating method and coating conditions as those for the phosphor layer described above.

  Further, it is also preferable that the phosphor layer and the dielectric layer are continuously applied simultaneously on the transparent electrode layer or the back electrode layer in order to improve the smoothness of the interface between the phosphor layer and the dielectric layer. Simultaneous application can be performed using a multi-stage slide coater, an extrusion coater, or a doctor blade coater. In this case, it is preferable that the liquid specific gravity of the lower layer dispersion is larger than the liquid specific gravity of the upper layer dispersion to improve the smoothness of the coating interface between the two layers.

  As the transparent electrode layer used in the EL element of the present invention, an electrode formed using an arbitrary transparent electrode layer material on one surface of a transparent polymer film is used. As the polymer film, PET, PAR, PES, or the like is used, and the film thickness of the polymer film is preferably in the range of 20 to 200 μm, more preferably 50 to 100 μm. The film thickness variation at this time is preferably 10% or less, more preferably 5% or less with respect to the average film thickness. Examples of the transparent electrode layer material include ITO (indium tin oxide), IZO (indium zinc oxide), ATO (antimony-doped tin oxide), ZTO (zinc-doped tin oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped). Zinc oxide), FTO (fluorine-doped tin oxide), etc., or a coating film coated with conductive ink in which these oxide particles are dispersed in a polymer, a multilayer structure in which a silver thin film is sandwiched between high refractive index layers Examples thereof include π-conjugated polymer films such as a film, polyaniline, and polypyrrole. The surface resistivity of the transparent electrode layer is preferably in the range of 300Ω / □ or less, in that the EL element exhibits high brightness, more preferably in the range of 100Ω / □ or less, and still more preferably in the range of 30Ω / □ or less. The surface resistivity can be measured by the measuring method described in JIS K6911. At this time, the 550 nm transmittance of the transparent electrode layer is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. If the film thickness of the transparent electrode layer is increased, the surface resistivity is decreased, but the light transmittance is decreased. Therefore, the film thickness of the transparent electrode layer is preferably in the range of 5 to 500 nm in terms of balance between conductivity and transmittance. 10 to 300 nm is more preferable.

  In these transparent electrode layers, it is also preferable to dispose metal fine wires such as a mesh type, a comb type, and a grid type in the transparent electrode layer to improve conductivity and transparency. Although the light transmittance is reduced by arranging the fine metal wires, since the film thickness of the transparent electrode layer can be reduced, the light transmittance can be improved more than the reduced amount due to the arrangement of the fine metal wires. As the material of the fine metal wires to be arranged, copper, gold, silver, aluminum, nickel, alloys containing them, and the like are preferably used. A material having high electrical conductivity and high thermal conductivity is preferable. The width of the fine metal wire is preferably between 0.1 and 1000 μm. It is preferable that the space | interval of a metal fine wire is arrange | positioned by the space | interval of 50 micrometers-5 cm, and 100 micrometers-1 cm are more preferable. The height (thickness) of the fine metal wire is preferably in the range of 0.1 to 10 μm, more preferably 0.5 to 5 μm. The width of the fine metal wire is preferably 1/10000 to 1/10 of the fine wire 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. Either the fine metal wire or the transparent conductive film may be exposed on the surface, but the smoothness of the conductive surface is preferably 5 μm or less, more preferably 0.05 to 3 μm. Here, the smoothness of the conductive surface indicates the average amplitude of the concavo-convex portion when measuring 5 mm square using a three-dimensional surface roughness meter (for example, manufactured by Tokyo Seimitsu Co., Ltd .; SURFCOM 575A-3DF). For the surface roughness meter that does not reach the resolution, the smoothness is obtained by measurement with an STM or an electron microscope.

  In order to prevent a voltage drop due to the large area of the EL element, a bus electrode is formed with a conductive paste containing conductive fine particles such as copper, gold, silver, carbon, etc. on the inner peripheral portion on the transparent electrode layer. It is preferable. The area of the bus electrode is 1% or more with respect to the area of the phosphor layer, and more preferably 2% or more in order to efficiently supply power to the phosphor layer. Since the bus electrode needs to be increased in accordance with the increase in the area of the phosphor layer, it is necessary to express the bus electrode as an area ratio with respect to the total area of the phosphor layer. The reason for setting it to 1% or more is to reduce the thickness of the phosphor layer and increase the driving voltage and frequency in order to increase the luminance. However, since the bus electrode area of 10% or more does not affect the performance of the EL element, it is not preferable because the non-light emitting portion is unnecessarily increased or the element area is increased. As a method for forming the bus electrode, a screen printing method, a casting method, or the like can be used.

  The back electrode layer is a side from which light is not extracted, and any conductive material can be used. For example, a metal material such as copper, aluminum, gold, silver, or the like can be used. The metal material to be used is preferably a sheet. It is also preferable to use a graphite sheet instead of the metal sheet. The thickness of the sheet-like back electrode is preferably in the range of 20 to 200 μm, more preferably 50 to 100 μm. The film thickness variation at this time is preferably 10% or less, more preferably 5% or less with respect to the average film thickness. In order to make the heat generated by driving the EL element uniform in the surface of the EL element and efficiently dissipate it, the thermal conductivity of the back electrode layer is preferably 100 W / m · K or more, and 200 W / m. -More preferably, it is K or more. For heat dissipation, it is preferable to move the heat to a metal member or heat sink that fixes the EL element by thermal contact with the back electrode. Further, the back electrode layer may be formed by applying a conductive paste containing conductive fine particles such as copper, gold, silver, and carbon. The thickness of the back electrode layer formed by coating is preferably in the range of 10 to 100 μm, more preferably 20 to 50 μm. In this case, for example, a back electrode layer is applied and formed on a laminate in which a phosphor layer and a dielectric layer are sequentially laminated on a transparent electrode layer. In this case, it is preferable to use the same coating method and coating conditions as those of the phosphor layer and the dielectric layer described above.

  The EL device of the present invention improves adhesion strength between the transparent electrode layer and the phosphor layer to prevent delamination between the transparent electrode layer and the phosphor layer, or by contact between the EL phosphor particles and the transparent electrode layer. To prevent deterioration due to corrosion of the transparent electrode layer and local heat generation at the contact interface between the EL phosphor particles and the transparent electrode layer, at least one intermediate layer is provided between the transparent electrode layer and the phosphor layer. Is preferred. The intermediate layer may be an organic polymer compound, an inorganic compound, or a composite thereof, but preferably has at least one layer containing an organic polymer compound. The thickness of the intermediate layer is preferably in the range of 10 nm to 100 μm, more preferably 100 nm to 30 μm, and particularly preferably 0.5 to 10 μm. The film thickness variation at this time is preferably 10% or less, more preferably 5% or less with respect to the average film thickness.

  When the material forming the intermediate layer is an organic polymer compound, usable polymer compounds include polyethylene, polypropylene, polystyrene, polyesters, polycarbonates, polyamides, polyethersulfones, polyvinyl alcohol, pullulan and saccharose, Polysaccharides such as cellulose, vinyl chloride, fluororubber, polyacrylic acid esters, polymethacrylic acid esters, polyacrylic acid amides, polymethacrylic acid amides, silicone resin, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl saccharose, or Examples thereof include an ultraviolet light curable resin obtained from a polyfunctional acrylate compound, a thermosetting resin obtained from an epoxy compound and a cyanate compound, and the like. The polymer compound used here may be an insulator or a conductor. Of these, those having a softening point of 70 ° C. or higher (more preferably 100 ° C. or higher) are preferable. It is also preferred that a plurality of polymer compounds selected from these are combined. When the organic polymer compound in the intermediate layer has a high softening point (for example, 200 ° C. or higher), the organic polymer compound has a low softening point for the purpose of improving the adhesion to the transparent electrode layer or the luminescent particle-containing layer. It is also preferable to use another intermediate layer containing

  These organic polymer compounds or precursors thereof can be formed by dissolving in a suitable organic solvent and coating on a transparent electrode or a phosphor layer. In that case, it is preferable to use the same coating method and coating conditions as those of the phosphor layer, dielectric layer, electrode layer, and the like. Examples of the organic solvent include dichloromethane, chloroform, acetone, methyl ethyl ketone, cyclohexanone, acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, toluene, xylene, and the like.

  The intermediate layer may have additives for imparting various functions within a range having substantial transparency. As the transmittance of the intermediate layer, the transmittance at a wavelength of 550 nm is preferably 70% or more, more preferably 80% or more. For example, a dielectric such as barium titanate particles, or a conductor such as tin oxide, indium oxide, tin-indium oxide, and metal particles, or a dye, a fluorescent dye, a fluorescent pigment, or an extent that does not lose the effect of the present invention (EL element) Luminescent particles having 30% or less of the total luminance) may be present.

The intermediate layer may be made of an inorganic compound such as SiO ₂ , other metal oxides, and metal nitrides. As a method for forming the intermediate layer with an inorganic compound, a sputtering method, a CVD method, or the like can be employed. When the intermediate layer is formed of an inorganic compound, the film thickness is preferably 10 nm to 1 μm, more preferably 10 nm to 200 nm. It is also preferable that the intermediate layer is composed of a combination of an inorganic compound layer and an organic polymer compound layer.

  In the electroluminescence device of the present invention, a luminescent material that emits red light is used in addition to the zinc sulfide particles that emit blue-green to produce white light emission. The red luminescent material may be dispersed in the luminescent particle layer or in the dielectric layer, and is positioned between the luminescent particle layer and the transparent electrode or on the opposite side of the luminescent particle layer with respect to the transparent electrode. Also good.

  In the electroluminescent device of the present invention, the red light emission wavelength during white light emission is preferably 600 nm or more and 650 nm or less. In order to obtain a red light emission wavelength included in this range, whether the red light emitting material is contained in the light emitting particle layer or between the light emitting particle layer and the transparent electrode, the opposite side of the light emitting particle layer centering on the transparent electrode However, it is most preferable that it be contained in the dielectric layer. The dielectric layer containing the red light emitting material is preferably a layer containing the red light emitting material for all the dielectric layers in the electroluminescence device of the present invention, but the dielectric layer in the device is divided into two or more, It is more preferable that a part of them is a layer containing a red light emitting material. The layer including the red light emitting material is preferably located between the dielectric layer not including the red light emitting material and the light emitting particle layer, and both sides may be positioned so as to be sandwiched between the dielectric layers not including the red light emitting material. preferable.

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

  The emission wavelength when the red light emitting material used here is in a powder state is preferably 600 nm or more and 750 nm or less, more preferably 610 nm or more and 650 nm or less, and most preferably 610 nm or more and 630 nm or less. It is. This luminescent material is added to the electroluminescence element, and the red emission wavelength during electroluminescence emission is preferably 600 nm or more and 650 nm or less as described above, more preferably 605 nm or more and 630 nm or less, and most preferably Is 608 nm or more and 620 nm or less.

  Even when the red light emitting material layer as described above is set in the dielectric layer, the total thickness of the dielectric layer is preferably 5 μm or more and 40 μm or less, more preferably 10 μm or more and 35 μm or less. The dielectric particles used for the dielectric layer containing the red light emitting material can be selected from the same particles as those used for the dielectric layer not containing the red light emitting material. As the dielectric particles, the same particle or different particles may be used for the layer containing the red light emitting material and the layer not containing the red light emitting material. As a binder for a layer containing a red light emitting material, 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 is used. preferable. As a method for dispersing the dielectric material, it is preferable to disperse using a homogenizer, a planetary kneader, a roll kneader, an ultrasonic disperser or the like.

  As the red light emitting 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.

The EL device assembly method of the present invention can be suitably performed by any of the following methods. A method of laminating a transparent electrode layer and a laminate in which a dielectric layer and a phosphor layer are sequentially applied on a back electrode layer such as an aluminum foil, a laminate in which a phosphor layer and a dielectric layer are sequentially applied on a transparent electrode layer Preferred are a method of bonding the body and the back electrode layer, a method of bonding a laminate in which a phosphor layer is applied on a transparent electrode layer, and a laminate in which a dielectric layer is applied on a back electrode layer. The bonding is preferably performed by thermocompression bonding with a heat roller coated with metal or silicon resin. The thermocompression bonding temperature at this time is preferably in the range of 100 to 300 ° C, more preferably 150 to 200 ° C. The thermocompression bonding speed is preferably in the range of 0.01 to 1 m / min, more preferably 0.05 to 0.5 m / min. Thermocompression bonding pressure is preferably in the range of ^{0.01~1MPa / m 2, 0.05~0.5MPa / m} 2 is more preferable. If the thermocompression bonding temperature or pressure is low, sufficient adhesion strength cannot be obtained, causing delamination, and if it is too high, the phosphor layer and dielectric layer are excessively rolled and thinned to cause dielectric breakdown. Or the EL phosphor particles are crushed by pressure, or the binder contained in the phosphor layer or dielectric layer is deteriorated by temperature.

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.
The sealing film that seals the EL element preferably has a water vapor transmission rate of 0.1 g / m ² / day or less at 40 ° C. to 90% RH, which is measured according to the measurement method described in JIS K7129. more preferably not more than 05g ^/ m 2 ^/ day, and particularly preferably 0.01g ^/ m 2 ^/ day. Further, the oxygen permeability at 40 ° C. to 90% RH is preferably 0.1 cm ³ / m ² / day / atm or less, more preferably 0.01 cm ³ / m ² / day / atm or less. As such a sealing film, a polychlorinated trifluoroethylene resin or a laminated film of an organic film and an inorganic film is preferably used.

  When the sealing film is a laminated film, the organic film forming material is preferably a polyethylene resin, a polypropylene resin, a polycarbonate resin, a polyvinyl alcohol resin, and more preferably a polyvinyl alcohol resin. Since polyvinyl alcohol resins and the like have water absorption properties, it is more preferable to use a resin that has been dried in advance by a treatment such as vacuum heating. An inorganic film is deposited by vapor deposition, sputtering, CVD, or the like on these resins processed into a sheet by a method such as coating. As a material for forming the inorganic film to be deposited, silicon oxide, silicon nitride, silicon oxynitride, silicon oxide / aluminum oxide, aluminum nitride and the like are preferably used, and silicon oxide is particularly preferably used. In order to obtain a lower water vapor transmission rate and oxygen transmission rate, and to prevent the inorganic film from cracking due to bending, etc., the formation of the organic film and the inorganic film is repeated, or the organic film on which the inorganic film is deposited is attached to the adhesive layer. It is preferable that a plurality of sheets are laminated to form a multilayer film. The film thickness of the organic film is preferably in the range of 5 μm to 300 μm, and more preferably in the range of 10 μm to 200 μm. The thickness of the inorganic film is preferably in the range of 10 nm to 300 nm, and more preferably in the range of 20 nm to 200 nm. The thickness of the laminated sealing film is preferably in the range of 30 μm to 1000 μm, and more preferably in the range of 50 μm to 300 μm.

A hot melt adhesive is applied to one surface of the sealing film. When the EL cell is sealed with the sealing film, the EL cell is sandwiched between the two sealing films by thermocompression sealing. One sealing film may be folded in half and thermocompression sealed. For the thermocompression bonding, it is preferable to use the above-described heat roller, press-type thermocompression bonding machine, or the like. As the EL cell sealed with the sealing film, only the EL cell may be separately prepared, or the EL cell may be directly formed on the sealing film. In this case, the support can be replaced. The sealing step is preferably performed in a dry atmosphere with vacuum or dew point management. In the case of sealing in a vacuum atmosphere, 10 ⁻² Pa or less is preferable.

  In addition to the above, in order to suppress vibration of the EL element, a buffer material layer made of a polymer material having a high impact absorption capacity or a polymer material foamed by adding a foaming agent, a transparent electrode layer or a back electrode layer It is also preferable to provide a compensation electrode layer provided with an insulating layer interposed therebetween. Furthermore, in order to effectively remove the heat generated from the EL element by driving, it is also preferable to attach a heat dissipation sheet in which a ceramic material is dispersed. Furthermore, an ultraviolet absorbing layer is provided to prevent the fluorescent pigment contained in the image sheet and EL element described later from fading due to ultraviolet rays, and an electromagnetic wave absorbing layer is provided to prevent emission of electromagnetic waves from the EL element. It is also preferable to do.

Usually, an EL element is driven by alternating current using an alternating current power source of 100 Hz and 50 Hz to 400 Hz. When the area is small, the luminance increases almost in proportion to the applied voltage and frequency. However, in the case of an EL element having a large area of 0.25 m ² or more, the capacitance component of the EL element increases, the impedance matching between the EL element and the power source shifts, and the time constant required for charge storage in the EL element increases. For this reason, even if the voltage is increased or the frequency is increased, electric power is not sufficiently supplied. In particular, in an EL element of 0.25 m ² or more, for AC driving of 500 Hz or more, the applied voltage often decreases with an increase of the driving frequency, and the luminance decreases often. On the other hand, the EL element of the present invention can be driven at a high frequency even with a large size of 0.25 m ² or more, and can achieve high luminance. In that case, driving at 500 Hz to 5 KHz is preferable, and driving at 800 Hz to 3 KHz is more preferable.

  Applications of the EL element of the present invention include indoor and outdoor signs and displays. In particular, an image display system in which an EL element and a transmissive image sheet such as a color photographic print or an ink jet print are combined is preferable. In order to ensure the visibility of the image, the density of the transmission image sheet is preferably in the range of 1.5 to 4.5, more preferably 2 to 3. The transmission image sheet is disposed in close contact with the light emitting surface of the EL element. The transmission image sheet may be brought into close contact with pressure, static electricity, or the like, or may be detachably attached to the EL element with an adhesive or the like. It is also preferable to dispose a diffusion plate or the like between the image sheet and the EL element in order to increase the whiteness when no light is emitted. Further, a resin protective plate may be disposed on the surface of the image sheet. In order to sufficiently secure light resistance, impact resistance, and transparency, the protective plate is preferably made of a resin such as acrylic or polycarbonate, or a material obtained by providing an ultraviolet absorbing layer on these resins. The protective plate preferably has a thickness of 1 to 10 mm, and more preferably 2 to 8 mm, in order to ensure rigidity and prevent the EL element from being damaged or electric shock by a sharp metal such as a cutter knife. It is preferable that the image display unit including the EL element, the image sheet, and the protective plate is fixed by a fixing member including a fixing frame and a back plate such as aluminum, resin, and wood. The EL element may be detachably fixed to the fixed frame or the back plate by an adhesive or the like, or may be fixed by pressure or the like. In installation on a curved surface such as a cylinder, it is preferable to fix using a fixing member similar to the curvature of the installation surface. In addition, it is preferable to save the space by providing a space in the fixing member and storing the power source for driving the EL element.

  Hereinafter, the EL phosphors of the present invention, their production methods, and EL elements will be described in more detail based on examples, but the examples of the present invention are not limited to the following examples.

<Preparation of phosphor particles>
[EL phosphor particles A]
ZnS having a crystallite size of 20 nm and an average particle size of 0.1 μm was prepared as a ZnS raw material. 25 g of this ZnS was weighed, placed in a 300 ml beaker with 200 ml of distilled water, and stirred with a magnetic stirrer so that all ZnS particles were dispersed. An aqueous solution in which 0.09 g of CuSO ₄ .5H ₂ O was weighed and dissolved in 5 ml of distilled water was prepared, and the solution was added to the solution in which the ZnS particles were dispersed for about 30 seconds using a burette. Stirring is maintained for 30 minutes from the end of the addition, and after standing, it is left to stand for a period of time until the ZnS particles settle, and the supernatant liquid in which the ZnS particles are completely settled is removed by decantation for the purpose of washing. 200 ml of distilled water was added and dispersed by stirring again. After stirring for 10 minutes, the ZnS particles were allowed to settle and the supernatant was removed by decantation. After this washing operation was repeated three times, it was dried at 120 ° C. for 4 hours with a hot air dryer to obtain Cu-added ZnS.
The following flux was added to the Cu-added ZnS in the following amount and mixed in a mortar to obtain a mixture.

・ Cu ・ (Au) -added ZnS ・ ・ ・ 25g
・ SrCl ₂ · 6H ₂ O 27.3 g
・ BaCl ₂・ 2H ₂ O ・ ・ ・ 4.2g
・ MgCl ₂ · 6H ₂ O ... 11.1 g

  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 800 ° C./h, maintained at 1200 ° C., and first firing was performed in air for 1 hour. After the first baking, the mixture was naturally cooled to room temperature, and the alumina crucible was taken out. The first fired mixture was taken out from the alumina crucible, washed with an aqueous HCl solution and distilled water, and dried at 120 ° C. for 4 hours with a hot air dryer. As a result, ZnS: Cu, Cl intermediate phosphor particles were obtained.

  After filling 5 g of the intermediate phosphor particles and 20 g of 1 mm alumina balls into a 15 mmφ glass bottle and ball milling at a rotation speed of 10 rpm for 20 minutes, the alumina balls and the intermediate phosphor particles were separated using a 100 mesh sieve. . The separated intermediate phosphor particles were 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 700 ° C., and second baking was performed in air for 4 hours. After the second baking, the mixture was cooled to room temperature, and the alumina crucible was taken out. The second fired product was taken out from the alumina crucible, washed with 100 ml of 10% KCN aqueous solution, then washed 5 times with 500 ml of distilled water, and dried with a hot air dryer at 120 ° C. for 4 hours. As a result, ZnS: Cu, Cl EL phosphor particles A having an average particle size of 18 μm were obtained.

[EL phosphor particles B and B ']
In the EL phosphor particle A, when 0.09 g of CuSO ₄ .5H ₂ O was weighed, 0.05 g of HAuCl ₄ .4H ₂ O was further weighed, and the above 5 ml of distillation was simultaneously performed with CuSO ₄ .5H ₂ O Except for preparing an aqueous solution dissolved in water, an EL phosphor particle B of ZnS: Cu, Cl, Au was obtained in the same manner as the EL phosphor particle A described above.

  Further, an EL phosphor particle B ′ of ZnS: Cu, Cl, Au was obtained in the same manner as the EL phosphor B except that the ball mill treatment of the intermediate phosphor particle of the EL phosphor particle B was omitted.

[EL phosphor particles BA]
In the EL phosphor particle B, an EL phosphor particle BA of ZnS: Cu, Cl, Au was obtained in the same manner as the EL phosphor B except that 0.9 g of HAuCl ₄ .4H ₂ O was used.

[EL phosphor particles BB]
In the above EL phosphor particle B, ZnS: Cu, Cl, Au EL phosphor particles BB were used in the same manner as EL phosphor B, except that 2 g of NaCl was used instead of 27.3 g of SrCl ₂ .6H ₂ O. Got.

[EL phosphor particles C]
In the EL phosphor particle A, ZnS: Cu, Cl is exactly the same as the EL phosphor particle A except that, when CuSO ₄ .5H ₂ O is weighed, 0.01 g instead of 0.09 g is weighed. EL phosphor particles C were obtained.

[EL phosphor particles CA]
In the EL phosphor particle A, when CuSO ₄ .5H ₂ O is weighed, the EL of ZnS: Cu, Cl is exactly the same as the EL phosphor particle A except that 1 g instead of 0.09 g is weighed. Phosphor particles CA were obtained.

[EL phosphor particles D]
In the EL phosphor particle A, when 0.09 g of CuSO ₄ .5H ₂ O was weighed, 0.05 g of HAuCl ₄ .4H ₂ O was further weighed, and simultaneously with CuSO ₄ .5H ₂ O, After preparing an aqueous solution dissolved in distilled water and taking a part of the BaCl ₂ · 2H ₂ O and adding 17.5 mg of Na ₂ [Pt (OH) ₆ ] and mixing well, ZnS raw flour Otherwise, the EL phosphor particles D of ZnS: Cu, Cl, Au, Pt were obtained in the same manner as the EL phosphor particles A except that the mixture was obtained by mixing with other fluxes.

[EL phosphor particles J]
A phosphor particle J of ZnS: Cu, Cl having an average particle size of 28 μm was obtained in the same manner as the EL phosphor particle A except that the mixture of the EL phosphor particle A before the first firing was changed to the following composition. .
・ Cu-added ZnS: 25g
・ NaCl ・ ・ ・ 0.5g
・ BaCl ₂・ 2H ₂ O ・ ・ ・ 1.0g
・ MgCl ₂・ 6H ₂ O ・ ・ ・ 2.1g

[EL phosphor particles K, K ']
In the phosphor particles J, when 0.09 g of CuSO ₄ .5H ₂ O was weighed, 0.05 g of HAuCl ₄ .4H ₂ O was further weighed, and the above 5 ml distilled simultaneously with CuSO ₄ .5H ₂ O. Except that an aqueous solution dissolved in water was prepared, EL phosphor particles K of ZnS: Cu, Cl, Au were obtained in the same manner as EL phosphor particles J described above.

<Cleaning of phosphor particles>
In the EL phosphor particles A to K and B ′ obtained above (before washing), the washing after the first firing was performed in an impeller stirrer in 500 ml of a 0.1 mol / L HCl solution kept at 70 ° C. For 30 minutes, or with 500 ml of 0.1 mol / L HCl solution kept at 70 ° C. for 30 minutes using an impeller stirrer, and subsequently in 500 ml of 0.06 mol / L HCl solution. After washing with an ultrasonic cleaner of 28 kHz-100 W for 10 minutes, each was washed five times with distilled water to obtain EL phosphor particles A to K and B ′ (after washing).
In the above washing, EL phosphor particles B ′ (before washing) are washed in the same manner as above using 500 ml of pure water instead of 500 ml of 0.1 mol / L HCl solution, and EL (after washing) Phosphor particles b were obtained.
The phosphor particles as shown in Table 1 were obtained by the above method.

<Evaluation of phosphor particles>
The following items were measured or evaluated for the produced EL phosphor particles.
(1) Average particle size (Horiba, Ltd .; measured using the median diameter calculated by LA-920)
(2) Coefficient of variation of particle size (Horiba, Ltd .; measured using the coefficient of variation calculated by LA-920)
(3) Stacking fault surface spacing (Phosphor particles are polished in a menor mortar, shards are observed with TEM, and the maximum surface spacing and number of stacking faults are measured)
(4) Stacking fault frequency (Measure the stacking fault frequency by TEM observation of the above 100 pieces)
(5) Phosphor composition analysis (Alkaline earth metal, Cu measured by ICP, Au measured by ICP-MAS)

<Creation of EL element>
Using the EL phosphor particles obtained above, an EL device was produced by the method described below. Note that the EL element was manufactured in an environment of a temperature of 20 ° C. and a humidity of 47% RH.

  A transparent electrode film was prepared by laminating an ITO electrode having a surface resistivity of 100Ω / □ on a 100 μm PET support. Next, a solution having a concentration of 14% by mass in which a polyester (Unitika Ltd .; U-100) of bisphenol A and phthalic acid (terephthalic acid and isophthalic acid 1: 1) is dissolved in dichloromethane is applied to the transparent electrode film by a dip coating method. After forming a 2 μm thick layer, a 30 mass% solution of cyanoresin (manufactured by Shin-Etsu Chemical Co., Ltd .; CR-V) dissolved in DMF was added to the 0.5 μm thick layer (this layer was formed by dip coating). (Referred to as “intermediate layer”), and a transparent electrode provided with the intermediate layer was formed. When an intermediate layer was not formed, a transparent electrode film (without an intermediate layer) was used as it was by using a transparent electrode film in which an ITO electrode having a surface resistivity of 100Ω / □ was laminated on a 100 μm PET support.

  Next, barium titanate (manufactured by Cabot Specialty Chemicals: BT-8, average particle size of 120 nm) is used as dielectric particles, and cyanoresin (manufactured by Shin-Etsu Chemical Co., Ltd .; a mixture of CR-S and CR-V in the same mass) is used as a binder. A solution with a concentration of 35% by mass dissolved in DMF is prepared. The following composition was placed in a Teflon wide-mouth bottle and dispersed on a rotating roller at 50 rpm for 30 minutes, and then 280 parts by mass of zirconia particles having an average particle diameter of 2 mm was added and dispersed for another 30 minutes.

  This dispersion was dispersed for 2 hours with a mix rotor (consisting of a parallel multi-stage disc made of alumina). The rotor rotation speed was initially 500 rpm and dispersed while gradually increasing to 2000 rpm. In order to prevent evaporation of the solvent, the periphery of the disperser pot was cooled to about 20 ° C. with water. After this dispersion, 120 parts by mass of a 35% by mass cyanoresin solution and 54 parts by mass of DMF were added to the dispersion and further dispersed for 20 minutes. The dispersion was filtered through a nylon mesh having an opening of 50 μm and defoamed. Disperse the filtered dispersion in a Teflon wide-mouth bottle, disperse it on a rotating roller at 50 rpm for 24 hours, add an appropriate amount of DMF, and disperse the dielectric particles with a viscosity at 16 ° C. of 0.5 Pa · s. A liquid was prepared. Further, the dielectric particle dispersion was passed through a 0.66 μm filter (manufactured by Loki Techno Co.) immediately before coating.

-BT-8 ... 280 parts by mass-Cyanoresin ... 80 parts by mass-DMF ... 25 parts by mass

  Next, a doctor having a bull nose knife in which a clearance is set on an aluminum base having a film thickness of 80 μm (film thickness variation of ± 3 μm) as a back electrode so that the film thickness after drying is 20 μm. Using a blade coater, coating was performed at a coating speed of 0.9 m / min, and drying was performed with a drying unit arranged so as to increase the temperature stepwise from 110 to 130 ° C., and a dielectric layer was laminated on the back electrode. .

  Next, barium titanate (manufactured by Cabot Specialty Chemicals: BT-8, average particle size of 120 nm) is used as dielectric particles, and cyanoresin (manufactured by Shin-Etsu Chemical Co., Ltd .; a mixture of CR-S and CR-V in the same mass) is used as a binder. A solution having a concentration of 30% by mass dissolved in DMF and a red pigment having an emission peak at a wavelength of 620 nm are prepared. The following composition was placed in a Teflon wide-mouth bottle and dispersed on a rotating roller at 50 rpm for 30 minutes, and then 280 parts by mass of zirconia particles having an average particle diameter of 2 mm was added and dispersed for another 30 minutes.

  This dispersion was dispersed for 2 hours with a mix rotor (consisting of a parallel multi-stage disc made of alumina). The rotor rotation speed was initially 500 rpm and dispersed while gradually increasing to 2000 rpm. In order to prevent evaporation of the solvent, the periphery of the disperser pot was cooled to about 20 ° C. with water. After this dispersion, 120 parts by mass of a 30% by mass cyanoresin solution and 54 parts by mass of DMF were added to the dispersion and further dispersed for 20 minutes. The dispersion was filtered through a nylon mesh having an opening of 50 μm and defoamed. Disperse the filtered dispersion in a Teflon wide-mouth bottle, disperse it on a rotating roller at 50 rpm for 24 hours, add an appropriate amount of DMF, and disperse the dielectric particles with a viscosity at 16 ° C. of 0.5 Pa · s. A liquid was prepared. Further, the dielectric particle dispersion was passed through a 0.66 μm filter (manufactured by Loki Techno Co.) immediately before coating.

-BT-8 ... 280 parts by mass-Cyanoresin ... 80 parts by mass-Red pigment ... 17 parts by mass-DMF ... 25 parts by mass

  Next, a doctor having a bull nose knife in which a clearance is set so that the film thickness after drying of the dielectric particle dispersion liquid becomes 10 μm on an aluminum base having a film thickness of 80 μm (film thickness unevenness ± 3 μm) as a back electrode. Using a blade coater, coating was performed at a coating speed of 0.9 m / min, and drying was performed with a drying unit at 110 ° C., and a pigment layer was laminated on the back electrode.

  Next, each EL phosphor and a cyanoresin (manufactured by Shin-Etsu Chemical Co., Ltd .; a mixture in which CR-S and CR-V are mixed in the same mass) as a binder are prepared in a solution having a concentration of 35% by mass in acetonitrile. The following composition is placed in a Teflon wide-mouth bottle, dispersed on a rotating roller at 50 rpm for 16 hours, and then added with an appropriate amount of acetonitrile to disperse EL phosphor particles having a viscosity at 16 ° C. of 0.5 Pa · s. A liquid was prepared. The viscosity of each coating solution was measured at a liquid temperature of 16 ° C. under stirring (rotation speed: 20 rpm) using a viscometer (VISCONIC ELD.R and VISCOMETER CONTROLLER E-200 Rotor No. 71, manufactured by Tokyo Keiki Co., Ltd.). did.

・ EL phosphor ・ 98 parts by mass ・ Cyanoresin 35 mass% solution ・ 70 parts by mass ・ Acetonitrile ・ about 15 parts by mass

  Using a doctor blade coater having a bull nose type knife with a clearance set so that the film thickness after drying is 30 μm and 50 μm on the dried dielectric layer, 0.5 m It was applied at a coating speed of / min and dried with a drying unit arranged so as to increase the temperature stepwise from 110 to 130 ° C. to obtain a laminate in which a back electrode, a dielectric layer and a phosphor layer were laminated.

After attaching the extraction electrode to the phosphor layer of each obtained laminate and the transparent electrode film, using a laminator, the roller temperature is 190 ° C., the feed rate is 0.1 m / min, and the pressure is 0.2 MPa / m. ² for thermocompression bonding. Finally, it cut out to A4 size, the whole laminated body was sealed with the PCTFE moisture-proof film (made by Nitto Denko Corporation), and the EL element was obtained. The structure of an EL element using the transparent electrode film II is shown in FIG.

<Evaluation of EL element>
The luminance, luminous efficiency, and luminance half-life when each EL element obtained as described above was driven with an AC voltage of 100 V-1 kHz were measured. The luminance of the EL element was measured with a luminance meter (Topcon; BM9). Luminous efficiency was obtained by calculating the luminous efficiency by measuring the power consumption when driving the EL element with a power multimeter (NF circuit; 2721). The luminance half-life was determined by measuring the time to decrease to half the initial luminance when continuously driven under the driving condition of 100 V-1 kHz and initial luminance of 300 cd / m ² .
These results are shown in Tables 1 and 2.

  From these results, it can be seen that in the embodiment of the present invention, the relative luminous efficiency and the relative luminance half-life are remarkably improved while maintaining the luminance. In particular, particle size selection (eg, comparison between Example 1 and Comparative Example a), and appropriate amount of copper addition (eg, comparison between Example 1 and Comparative Examples e1, e2), appropriate amount of gold addition (eg, (Comparison between Example 1 and Comparative Examples d1 and d2) makes the above effect more remarkable, and further reduces the content of alkaline earth metal (for example, comparison between Example 1 and Example 3), thereby emitting light. It can be seen that the above effect is further improved by selecting the film thickness of the phosphor layer that increases the efficiency (for example, comparison between Example 1 and Example 4).

FIG. 1 is a schematic explanatory view showing a cross section of an example of the EL element of the present invention.

Explanation of symbols

52. Intermediate layer 53. Phosphor layer 54. Dielectric layer 55. Transparent electrode layer 56. PET support 57. Back electrode layer 58. Moisture barrier film

Claims (8)

An electroluminescent phosphor containing ZnS as a matrix, containing at least Au and Cu as activators, and containing at least one selected from Cl, Br, I and Al as coactivators, The average particle size is 0.1 to 20 μm, the coefficient of variation of the particle size is less than 35%, and the stacking fault of 10 layers or more with the plane spacing of the stacking fault within the phosphor host crystal being 5 nm or less. 30% or more of the total number of phosphor particles, 1 × 10 ^{−7 to} 5 × 10 ⁻⁴ mol of Au with respect to 1 mol of ZnS, and Cu with respect to 1 mol of ZnS An electroluminescent phosphor containing 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol.   2. The electroluminescent phosphor according to claim 1, wherein the average particle size of the phosphor is 15 to 20 [mu] m. 3. The electroluminescent phosphor according to claim 1, wherein Pt is contained in an amount of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol with respect to 1 mol of ZnS.   4. The electroluminescent phosphor according to claim 1, wherein the total content of alkaline earth metal elements (Mg, Ca, Sr, Ba) is 0.075 mass% or less.   It has a light emitting layer containing the electroluminescent fluorescent substance in any one of Claims 1-4, The electroluminescent element characterized by the above-mentioned.   6. The electroluminescent device according to claim 5, wherein the thickness of the light emitting layer is 40 μm to 100 μm.   7. The dispersion type electroluminescent device according to claim 5, wherein at least one intermediate layer is provided between the transparent electrode and the phosphor layer.   The dispersion type according to any one of claims 5 to 7, wherein the intermediate layer is an organic polymer compound, an inorganic compound, or a composite thereof, and the thickness of the intermediate layer is in the range of 10 nm to 100 µm. Electroluminescence element.

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