JP2009140624A - Composition for light-emitting layer, and dispersion type el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion type EL element of high brightness, with dielectric breakage hardly occurring, reduction in thickness being possible, of which manufacturing process is simple. <P>SOLUTION: The composition for a light-emitting layer, being used for forming a light-emitting layer of the dispersion type EL element, is characterized by containing resin component and phosphor powder having a local emission center, having a withstand voltage 0.15 MV/cm or higher. The dispersion type EL element comprises the composition for a light-emitting layer, a transparent conductive layer, the light-emitting layer, a dielectric layer, and a rear side electrode. The light-emitting layer of the dispersion type EL element is made from the composition for the light-emitting layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a composition for a light emitting layer and a dispersion type EL device used for manufacturing a dispersion type EL (Electroluminescence) device.

  There are various types of EL elements depending on the driving method and element structure. Among these, an element that emits light by applying an AC voltage is generally called an inorganic EL element. Inorganic EL elements are roughly classified into a dispersion type EL element using a layer made of phosphor powder and a resin component as a light emitting layer and a thin film type EL element using a phosphor thin film as a light emitting layer, depending on the production method. Inorganic EL elements have been used for LCD backlights, clock dials, various types of lighting, display elements, and the like because of their surface emission characteristics.

  The dispersion type EL element is characterized in that the light emitting layer is made of phosphor powder and a resin component. A general structure of a dispersion type EL element is a structure in which a light emitting layer, a dielectric layer, and a back electrode are sequentially laminated on a transparent electrode. As a phosphor powder of the dispersion type EL element, a so-called donor / acceptor pair (DA pair) type fluorescence in which zinc sulfide is used as a base and an activator such as copper and a coactivator such as chlorine are added. Body powders are widely known. Such a dispersion type EL element is excellent in that it can be produced by a simple coating process such as printing or spraying.

  Patent Document 1 discloses a dispersion type EL element having a light emitting layer containing an inorganic phosphor and a pair of electrodes for applying a voltage to the light emitting layer, wherein the inorganic phosphor has a different average particle diameter. An invention relating to a dispersion-type EL element comprising particles and second inorganic fluorescent particles, wherein the ratio of the average particle diameter of the first inorganic phosphor particles to the average particle diameter of the second inorganic phosphor particles is 2 to 8. It is disclosed. The present invention is excellent in that a dispersion type EL element having relatively high light emission luminance and high weather resistance can be obtained.

  On the other hand, the general structure of a thin-film EL element has a structure in which a light emitting layer, a dielectric layer, and an electrode are sequentially laminated on an electrode as disclosed in the invention of Patent Document 2, and the light emitting layer is It is a thin film formed by vapor deposition or the like. The thin film EL element is excellent in that a thin EL element can be formed.

JP 2007-134121 A JP-A-53-108293

  In recent years, however, the inorganic EL element has been required to be thinner and have a higher light emission luminance. The conventional dispersion type EL element described above has an average particle diameter of the D / A pair phosphor powder used in the light emitting layer. However, since it is generally several tens of μm, it does not satisfy the demand for thinning. In addition, it is not fully satisfied with the demand for higher luminance. Furthermore, when the particle size of the D / A pair phosphor powder is reduced by grinding to reduce the thickness of the dispersion type EL element, the emission luminance of the D / A pair phosphor powder is greatly reduced. It is very difficult to achieve both high luminance and high luminance.

  In addition, the above-described conventional thin film type EL element requires processes such as vapor deposition and sputtering for the production of the light emitting layer, and therefore it is difficult to produce an EL element with a large manufacturing area and a large area. There is a problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dispersive EL element that has high emission luminance, can be thinned, and has a simple manufacturing process. .

  As a result of intensive investigations on the method for solving the above problems, the present inventors have developed a phosphor powder having a localized emission center in a composition for a light emitting layer for forming a light emitting layer of a dispersion type EL element, and The present invention has been completed by using a composition for a light emitting layer containing a resin component and having a withstand voltage of 0.15 MV / cm or more.

  That is, the present invention is a composition for a light emitting layer for forming a light emitting layer of a dispersion type EL device, and contains a phosphor powder having a local light emitting center and a resin component, and the light emitting layer formed is 0. The present invention relates to a composition for a light-emitting layer, which has a withstand voltage of 15 MV / cm or more. The present invention also relates to a dispersion type EL device having a transparent conductive layer, a light emitting layer, a dielectric layer, and a back electrode, wherein the light emitting layer is formed from the composition for light emitting layer.

  The composition for a light emitting layer of the present invention is a composition for a light emitting layer for forming a light emitting layer of a dispersion type EL device, and contains a phosphor powder having a local emission center and a resin component. The light-emitting layer is a composition for a light-emitting layer having a withstand voltage of 0.15 MV / cm or more. Therefore, the dispersion-type EL device of the present invention having a light-emitting layer formed from the composition for light-emitting layer Can have a very high emission luminance, hardly cause dielectric breakdown, can be thinned, and can be obtained by a simpler manufacturing process.

  The composition for a light emitting layer of the present invention is a composition for a light emitting layer for forming a light emitting layer of a dispersion type EL device, and contains a phosphor powder having a local emission center and a resin component. The light-emitting layer composition has a withstand voltage of 0.15 MV / cm or more.

  A phosphor powder having a localized emission center is a phosphor powder having an emission center such as a rare earth or a transition metal ion in a base material, and the emission center is localized. The emission mechanism of a phosphor powder having a localized emission center is that the phosphor powder is placed in an electric field, and when the high-energy electrons accelerated by the electric field collide with the emission center, the ground state of the emission center This is a light emission mechanism in which light is emitted when electrons in are excited to an excited state and then relaxed to the ground state.

On the other hand, the donor-acceptor pair (D / A pair) type phosphor powder used in the light-emitting layer of the conventional dispersion-type EL element emits light by energy transition between the donor and the acceptor, and the emission center is non-localized. Is. The light emission mechanism of the D / A pair phosphor powder is as follows. G. According to Fischer's paper (AG Fischer: J. Electrochem. Soc., 109 (1962) 1043, AG Fischer: J. Electrochem. Soc., 110 (1963) 733), copper activated zinc sulfide. A phosphor (ZnS: Cu, Cl) is taken as an example to estimate the light emission mechanism as follows. In the copper activated zinc sulfide phosphor, a part of copper (Cu) added to zinc sulfide (ZnS) enters the crystal lattice to form an acceptor level, and chlorine (Cl) or the like is an impurity that becomes a donor level. Each level is formed, and the transition between these becomes the emission center. On the other hand, the remaining Cu that does not fully enter the crystal lattice exists as acicular copper sulfide (Cu _x S). When voltage is applied to the phosphor, acicular copper sulfide emits electrons and holes, and the electrons are trapped in the donor and the holes are trapped in the acceptor. Since the donor order is relatively shallow, when the polarity of the electrode is changed, electrons trapped in the donor are ejected and recombined with holes trapped in the acceptor, thereby generating light emission.

  As described above, the light emission mechanism of the phosphor powder having the local emission center is different from the light emission mechanism of the DA pair type phosphor powder used in the conventional dispersion type EL element.

Examples of the phosphor powder having a localized emission center include a phosphor powder having a localized emission center in which at least one element selected from a transition metal and a rare earth element is doped into the base material as an emission center. . Examples of the transition metal include Mn and Cr. Examples of rare earth elements include Ce, Eu, Tb, and the like. Examples of the base material include a sulfide-based base material and an oxide-based base material. Examples of the sulfide-based base material include ZnS, CaS, SrS, BaS, MgAl ₂ S ₄ , CaAl ₂ S ₄ , SrAl ₂ S ₄ , BaAl ₂ S ₄ , ZnAl ₂ S ₄ , MgGa ₂ S ₄ , and CaGa. ₂ S ₄ , SrGa ₂ S ₄ , BaGa ₂ S ₄ , ZnGa ₂ S ₄ , MgIn ₂ S ₄ , CaIn ₂ S ₄ , SrIn ₂ S ₄ , BaIn ₂ S ₄ , ZnIn ₂ S ₄ , MgY ₂ S ₄ , CaY ₂ S ₄ , SrY ₂ S ₄ , BaY ₂ S ₄ , ZnY ₂ S ₄ , Ba ₂ ZnS _{3 and the} like. Examples of the oxide base material include Ga ₂ O ₃ , CaGa ₂ O ₄ , ZnGa ₂ O ₄ , BeGa ₂ O ₄ , Ge ₂ O ₃ , CaGeO ₃ , Ca ₂ Ge ₂ O ₇ , and Zn ₂ GeO _4. MgGeO ₃ , Y ₂ GeO ₅ , Y ₄ GeO ₈ , Y ₂ Ge ₂ O ₇ , CaO, Y ₂ O ₃ , SnO ₂ , Zn ₂ SiO ₄ , Y ₂ SiO _{5 and the} like.

Specific examples of the phosphor powder having a localized emission center include ZnS: Mn, ZnS: Tb, CaS: Eu, CaS: Ce, SrS: Ce, SrS: Cu, BaAl ₂ S ₄ : Eu, _{Ba 2 ZnS 3: Mn, Zn} 2 SiO 4: Mn, ZnGa 2 O 4: Mn , and the like.

  The method for producing the phosphor powder having the localized emission center is not particularly limited. For example, a complex pyrolysis method in which an organic complex containing a predetermined metal is decomposed by heat to produce an oxide-based phosphor powder; a compound that serves as a fuel containing the elements constituting the phosphor powder and an oxidizer Combustion synthesis method using a compound that plays a role as a starting material and making phosphor powder using a high-temperature self-propagation reaction; making phosphor powder by heat-treating a solution containing a metal salt into fine droplets A spray pyrolysis method; a solid phase reaction method in which phosphor powder is prepared by heat treatment after mixing predetermined powder raw materials. Further, liquid phase synthesis methods such as coprecipitation method, sol-gel method and hydrothermal synthesis method; vapor phase synthesis methods such as evaporation condensation (PVD) method and gas phase reaction deposition (CVD) method can also be mentioned.

  The phosphor powder having a localized emission center is preferably prepared through a pulverization step in addition to the above preparation method from the viewpoint of obtaining high emission luminance. The reason why a high emission luminance can be obtained by using a phosphor powder having a localized emission center produced through a pulverization process is not necessarily clear. For the above reasons, the inventors have increased the insulating property of the phosphor powder itself by changing the crystallinity and the like of the surface of the phosphor powder through the pulverization process. Since the light emitting layer formed from the phosphor powder having the localized emission center is difficult to break down even when a high voltage is applied, it is assumed that high light emission luminance can be obtained. The pulverization step may be wet pulverization or dry pulverization, but wet pulverization is preferable from the viewpoint of shortening the process because it can be dispersed in a solvent or the like simultaneously with the pulverization. In the case of wet pulverization, the raw material powder may be mixed with a solvent for wet pulverization, or the raw material powder may be mixed with a solvent and a resin component for wet pulverization. Further, a grinding aid may be used. Examples of the solvent include a solvent described later. Examples of the resin component include a resin component described later.

  The average particle diameter of the phosphor powder having a localized emission center is not particularly limited. Preferably, the 50% average particle size on a volume basis is 0.2 to 2.0 μm, more preferably 0.3 to 0.7 μm. The lower limit of this range is significant in terms of light emission luminance. The upper limit of this range is significant in that the dispersion type EL element can be thinned and the driving voltage of the dispersion type EL element can be lowered. Here, the volume-based 50% average particle diameter (hereinafter sometimes abbreviated as “average particle diameter”) is the median diameter (D50) of the volume-based particle size distribution measured by the laser Doppler method. It can be measured by using Nanotrac UPA-EX250 (manufactured by Nikkiso Co., Ltd., trade name, laser Doppler type particle size distribution measuring device).

  The resin component is not particularly limited. Examples of the resin component include epoxy resins such as bisphenol A type epoxy resin and phenol novolac type epoxy resin; cyanoethylated resins such as cyanoethylated pullulan, cyanoethylated cellulose, cyanoethylated saccharose, cyanoethylated polyvinyl alcohol, and cyanoethylated phenoxy resin; And fluorinated resins such as vinylidene fluoride-propylene hexafluoride copolymer resin and tetrafluoroethylene resin. Moreover, the hardening | curing agent which reacts with the said resin etc. can also be mix | blended as a resin component. Examples of the curing agent include imidazole curing agents, amine curing agents, isocyanate curing agents, and melamine curing agents. It is preferable to add a curing agent from the viewpoint that the layer to be formed is a crosslinked film and a mixed layer with other layers can be suppressed.

  The composition for light emitting layers of this invention can contain a solvent. The solvent is not particularly limited. For example, specifically, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl amyl ketone, ethyl isoamyl ketone, diisobutyl ketone, and methyl hexyl ketone; ethyl acetate, butyl acetate, methyl benzoate, propionic acid Esters such as methyl; ethers such as tetrahydrofuran, dioxane and dimethoxyethane; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate and 3-methoxybutyl acetate; ethyl Examples include alcohols such as alcohol and benzyl alcohol; aromatic hydrocarbons and aliphatic hydrocarbons.

  The composition for a light emitting layer of the present invention may contain a pigment dispersant, a surface conditioner, and the like as other components as long as the performance is not impaired.

The composition for light emitting layer of the present invention is characterized in that the light emitting layer to be formed has a withstand voltage of 0.15 MV / cm or more. The withstand voltage is preferably 0.25 to 0.75 MV / cm. By having this withstand voltage, when the light emitting layer is a thin layer, it is difficult to cause dielectric breakdown even when a high voltage is applied, and high light emission luminance can be obtained. Here, the withstand voltage is a value obtained by dividing the upper limit of the voltage that can be applied to the specimen without causing dielectric breakdown by the film thickness of the specimen. The withstand voltage can be measured by, for example, the following method. A composition for a light emitting layer is applied on a glass substrate (electrode area: 1 cm × 1 cm) on which an ITO electrode is formed so as to have a film thickness of 3 μm and dried to form a light emitting layer film. Subsequently, a gold electrode (electrode area: 1 cm × 1 cm) is formed on the light emitting layer film by vapor deposition so as to overlap with the ITO electrode, thereby producing a capacitor-like test body having an electrode area of 1 cm ² . A terminal is applied to each electrode of the test body and connected to a picoammeter 6487 (product name, current-voltage measuring device, manufactured by Caselay Co., Ltd.), and the current value at that time is increased while increasing the voltage by 1V up to a maximum of 500V. read. The voltage when the current value exceeds 2.5 mA in the middle of increasing the voltage or the voltage when the gold electrode is destroyed and the current cannot be measured is defined as a dielectric breakdown voltage. A value obtained by dividing the dielectric breakdown voltage by the film thickness is a withstand voltage.

  The withstand voltage can be obtained by appropriately selecting and combining the average particle diameter and volume concentration of the phosphor powder having the localized emission center in the light emitting layer to be formed, and the composition of the resin component. Specifically, for example, the 50% average particle diameter based on the volume of the phosphor powder having a localized emission center in the light emitting layer may be appropriately selected from the range of 0.2 to 2.0 μm, or localized in the light emitting layer. The withstand voltage range can be obtained by appropriately selecting the volume concentration of the phosphor powder having the type emission center within the range of 1 to 80%.

  The dispersion-type EL element of the present invention is a dispersion-type EL element having a transparent conductive layer, a light-emitting layer, a dielectric layer, and a back electrode, wherein the light-emitting layer is formed from the composition for light-emitting layer.

  The transparent conductive layer can be used without particular limitation as long as it is a transparent conductive layer usually used in the field. For example, indium tin oxide (ITO), indium oxide, tin oxide, fluorine doped tin oxide (FTO), antimony doped tin oxide (ATO), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), indium doped A thin film made of zinc oxide (IZO) or the like can be given.

  The film thickness of the light emitting layer is not particularly limited. The thickness of the light emitting layer is preferably 0.3 to 3.0 μm, more preferably 0.7 to 2.5 μm. The lower limit of this range is significant in that it is difficult for dielectric breakdown to occur. The upper limit of this range is significant in terms of lowering the drive voltage.

  Further, the light emitting layer preferably contains 1 to 80% by volume of phosphor powder having a localized emission center, and more preferably 15 to 55%. The lower limit of this range is significant in that there is no unevenness in surface light emission and high light emission luminance is obtained. The upper limit of this range is significant in that it is difficult to cause dielectric breakdown.

As the dielectric layer, a dielectric layer generally used in the art can be used. For example, a thin film of a high dielectric material, a layer made of a resin component, a layer made of a high dielectric material and a resin component, and the like can be given. Examples of the high dielectric material include silicon oxide (SiO ₂ ), silicon oxynitride (SiON), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), Barium tantalate (BaTa ₂ O ₆ ), tantalum oxide (Ta ₂ O ₅ ), strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ), lead niobate (PbNb ₂ O) ₆ ) and the like. Examples of the resin component include the same resin components as described in the description of the composition for the light emitting layer.

  The dielectric layer may be a dielectric layer containing conductive fine particles and the resin component. The dielectric layer is preferable from the viewpoint of obtaining high emission luminance at a low voltage. In particular, the dielectric layer preferably has a structure in which conductive fine particles are dispersed in a resin component from the viewpoint of insulation.

  Further, the dielectric layer may contain a high dielectric material in addition to the conductive fine particles and the resin component.

  As the conductive fine particles, conventionally known conductive fine particles can be used. Specifically, indium tin oxide (hereinafter sometimes abbreviated as “ITO”), indium oxide, tin oxide, fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO) Metal oxides such as gallium-doped zinc oxide (GZO) and indium-doped zinc oxide (IZO) are preferred.

  The conductive fine particles are preferably surface-treated. By conducting the surface treatment of the conductive fine particles, the conductive fine particles can be insulated, so that the content of the conductive fine particles in the dielectric layer is increased without impairing the insulating property of the formed dielectric layer. be able to. As a result, a dielectric layer having a high relative dielectric constant can be formed.

  The surface treatment method is not particularly limited, and a conventionally known method can be used. Specifically, for example, a method in which a metal alkoxide such as tetraethoxysilane or tetraisopropoxytitanium is deposited on the surface of the conductive fine particles as a metal oxide by a sol-gel reaction; Method of surface treatment by reacting with coupling agent; Method of surface treatment of conductive fine particles with resin through silane coupling agent; Method of surface treatment by mechanically mixing conductive fine particles and resin; Conductivity Examples of the method include a method of performing surface treatment on the surface of the fine particles by precipitating a silicate such as sodium silicate or an aluminate such as sodium aluminate as a metal oxide by adjusting pH.

  The 50% average particle diameter based on volume of the conductive fine particles is preferably 10 nm to 2000 nm, and more preferably 10 nm to 500 nm.

  In addition, the content of the conductive fine particles is preferably contained in the dielectric layer in a volume concentration range of 5 to 40% from the viewpoint of the insulation and dielectric constant of the dielectric layer to be formed. A range of 30% is more preferable. The content of the surface-treated conductive fine particles is calculated based on the amount of only the conductive fine particles excluding the surface-treated portion.

The capacitance density σ of the dielectric layer is preferably 2 × 10 ⁻⁹ F / cm ² ( ² nF / cm ² ) or more from the viewpoint of light emission luminance, and 4 × 10 ⁻⁹ F / cm ² (4 nF / cm ² ) or more is more preferable. Here, the capacitance density σ is a value obtained by dividing the capacitance value measured under the conditions of AC 5 V and frequency 1 kHz by the electrode area. The capacitance value is, for example, LCR manufactured by Hioki Electric Co., Ltd. It can be measured using HiTester 3532-50.

The relative dielectric constant of the dielectric layer is preferably 20 or more from the viewpoint of light emission luminance, and more preferably 25 or more. Here, the relative permittivity is the capacitance density σ (F / cm ² ), the layer thickness d (m), and the vacuum permittivity e ₀ = 8.82 × 10 ⁻¹² (F / m). Is a value calculated by substituting into the following formula (1).
Relative permittivity = (10,000 × σ × d) / e ₀ formula (1)

  The dielectric layer may be transparent or opaque, but when the dielectric layer is laminated between the transparent conductive layer and the light emitting layer of the present invention, the dielectric layer is transparent. It is preferable that the dielectric layer has the property (hereinafter sometimes abbreviated as “transparent dielectric layer”). The transparent dielectric layer is preferably a transparent dielectric layer composed of the conductive fine particles and the resin component from the viewpoint that high emission luminance can be obtained. In addition, the transparent dielectric layer preferably has a light transmittance of 90% or more in the wavelength range where the light emitting layer emits light from the viewpoint of suppressing a change in hue and a decrease in light emission luminance.

  The film thickness of the dielectric layer is not particularly limited. Preferably it is 0.3-5.0 micrometers, More preferably, it is 0.5-1.5 micrometers. The lower limit of this range is significant in that it is difficult for dielectric breakdown to occur. The upper limit of this range is significant in terms of lowering the drive voltage.

  The back electrode can be used without particular limitation as long as it is a back electrode usually used in the field. For example, a metal sheet such as aluminum; a metal film such as gold or aluminum or a conductive metal oxide deposited film such as ITO or a plastic sheet laminated with the deposited film; a metal powder such as silver or aluminum; or a conductive metal such as ITO Examples thereof include a coating film of a conductive paste in which an oxide is dispersed in a resin or a solvent.

  If the dispersion type EL element of the present invention is a dispersion type EL element having a transparent conductive layer, a light emitting layer, a dielectric layer, and a back electrode of the present invention, the laminated structure of the element is not limited. In the dispersion type EL device of the present invention, the dielectric layer may be only one layer or two layers. Specifically, the dispersion type EL element of the present invention is, for example, (I) a dispersion type formed by sequentially laminating a transparent dielectric layer, a light emitting layer of the present invention, a dielectric layer and a back electrode on a transparent conductive layer. EL element (hereinafter abbreviated as “dispersion type EL element (I)”), (II) The light emitting layer, dielectric layer and back electrode of the present invention are sequentially laminated on the transparent conductive layer. Dispersion EL element (hereinafter may be abbreviated as “dispersion EL element (II)”), (III) A transparent dielectric layer, a light emitting layer of the present invention, and a back electrode are sequentially laminated on the transparent conductive layer. And a dispersion type EL element (hereinafter sometimes abbreviated as “dispersion type EL element (III)”).

  The manufacturing method of the dispersion type EL element of the present invention is not particularly limited. Taking the dispersion type EL element (I) as an example, as a manufacturing method thereof, for example, a manufacturing method in which a transparent dielectric layer, a light emitting layer of the present invention, a dielectric layer and a back electrode are sequentially laminated on a transparent conductive layer. A production method in which a dielectric layer, a light emitting layer of the present invention, a transparent dielectric layer, and a transparent conductive layer are sequentially laminated on the back electrode; up to the transparent dielectric layer and the light emitting layer of the present invention on the transparent conductive layer; And a production method of laminating each of these layers in order and a laminate of a dielectric layer on the back electrode.

  In particular, in the dispersion type EL element (I), a step of forming a transparent dielectric layer on the transparent conductive layer, and the light emitting layer composition is coated and dried on the transparent dielectric layer. The manufacturing method having the steps of forming the step, forming the dielectric layer on the light emitting layer, and forming the back electrode on the dielectric layer in this order is simple in process and the visual recognition of the light emitting layer This is preferable from the viewpoint of the smoothness of the interface on the surface side. This manufacturing method will be described in detail below.

  The transparent conductive layer is preferably formed on a transparent substrate from the viewpoint of handling. The transparent substrate can be used without particular limitation as long as it is a transparent substrate that is usually used in the field. For example, glass, polyethylene terephthalate (PET), an acrylic board, etc. are mentioned. The method for forming the transparent conductive layer on the transparent substrate is not particularly limited, and a known method can be used. Specifically, for example, a method of forming a transparent conductive layer by applying and drying a transparent conductive paste on a transparent substrate, a method of forming a transparent conductive thin film on a transparent substrate by vapor deposition, and the like can be mentioned. .

  The transparent dielectric layer is formed on the transparent conductive layer. The formation method of a transparent dielectric material layer is not specifically limited, A well-known method can be used. For example, a method of forming a transparent dielectric layer by applying and drying a dielectric composition is preferable from the viewpoint of simple steps. Examples of the dielectric composition include a dielectric composition containing the resin component, a dielectric composition containing the conductive fine particles and the resin component, and the like. Moreover, the dielectric composition may contain a solvent, a pigment dispersant, a surface conditioner, etc. as other components as long as the performance is not impaired. As the dielectric composition, a dielectric composition containing the conductive fine particles and the resin component is preferable from the viewpoint of obtaining high luminance. The application method is not particularly limited as long as the film thickness is uniform and a smooth coating surface can be obtained. Specific examples of the application method include air spray coating, spin coating, curtain coating, roll coating, and screen printing. The drying conditions are not particularly limited as long as the dielectric composition contains a solvent and the solvent is sufficiently removed, or the curing condition contains a reaction between the resin and the curing agent. Instead, it can be determined appropriately.

  Then, the composition for light emitting layers of this invention is apply | coated and dried on a transparent dielectric material layer, and a light emitting layer is formed. The application method is not particularly limited as long as the film thickness is uniform and a smooth coating surface can be obtained. For example, air spray coating, spin coating, curtain coating, roll coating, screen printing, and the like can be given. The drying conditions are particularly limited as long as the composition for the light emitting layer contains a solvent, and the conditions for sufficiently removing the solvent, or the curing conditions include a reaction between the resin and the curing agent. It is not a thing and can be determined suitably. Specifically, when the composition for light emitting layers contains the solvent, the drying conditions which dry for 5 to 60 minutes at 40-150 degreeC after apply | coating the composition for light emitting layers are mentioned, for example.

  Subsequently, a dielectric layer is formed on the light emitting layer formed above. The method for forming the dielectric layer is not particularly limited. For example, a method of forming a dielectric layer by applying and drying a dielectric composition can be mentioned. Examples of the dielectric composition include a dielectric composition containing the resin component, and a dielectric composition containing the conductive fine particles and the resin component. A coating method and a drying method are not particularly limited, and for example, a method similar to the method for forming the transparent dielectric layer can be adopted.

  Further, a back electrode is formed on the dielectric layer formed above. The method for forming the back electrode is not particularly limited. Specifically, for example, a method of depositing a metal such as gold or aluminum on a dielectric layer, a method of bonding a metal sheet such as aluminum and a dielectric layer by lamination, or a metal powder such as silver or aluminum or ITO Examples of the method include a method in which a conductive paste in which a conductive metal oxide such as a resin is dispersed in a resin or a solvent is applied on a dielectric layer and then dried.

  In the case of the dispersion type EL element (II), a step of forming the light emitting layer by applying and drying the composition for the light emitting layer of the present invention on the transparent conductive layer, and forming a dielectric layer on the light emitting layer The manufacturing method which has the process of forming and a process of forming a back electrode on a dielectric material layer in this order is preferable from the point of the smoothness of the interface by the side of the visual recognition surface of a light emitting layer with a simple process. The formation method of each layer in this manufacturing method can take the method similar to the formation method explained in full detail in the manufacturing method of dispersion type EL element (I).

  In the case of the dispersion type EL element (III), the step of forming a transparent dielectric layer on the transparent conductive layer, and the light emitting layer composition of the present invention is applied and dried on the transparent dielectric layer to emit light. The manufacturing method which has the process of forming a layer and the process of forming a back electrode on a light emitting layer in this order is preferable from the point of the smoothness of the interface at the side of the visual recognition surface of a light emitting layer. The formation method of each layer in this manufacturing method can take the method similar to the formation method explained in full detail in the manufacturing method of dispersion type EL element (I).

  Since the dispersion-type EL element of the present invention can obtain high emission luminance, it is very useful as an electroluminescence-type dispersion-type EL element that emits light when an alternating voltage is applied.

  Hereinafter, the present invention will be described in more detail with reference to examples. “Part” and “%” indicate “part by mass” and “% by mass” unless otherwise specified.

Production Example 1
Preparation of phosphor powder having localized emission center KX-605A (product name, phosphor powder having localized emission center, ZnS: Mn, average particle size 5 μm) 60 g and ethanol 140 g After mixing and pulverizing with a shaker for 3 hours using a YTZ ball (trade name, manufactured by Nikkato Co., Ltd.) having a diameter of 0.5 mm, drying under reduced pressure was performed to obtain a phosphor powder having localized emission centers (P-1 ) The average particle size of this phosphor powder was 0.40 μm.

Example 1
Production of composition for light emitting layer (L-1) 31 g of a resin solution having a solid content of 20% in which cyanoresin CR-S (manufactured by Shin-Etsu Chemical Co., Ltd., trade name, cyanoethylated pullulan) is dissolved in cyclohexanone, Phosphor powder (P-1) 23.8 g having a typical emission center and 45.1 g of cyclohexanone were mixed and dispersed for 2 hours with a shaker to obtain a composition for light emitting layer (L-1). The withstand voltage of the light emitting layer formed by the obtained composition for light emitting layer (L-1) was 0.27 MV / cm.

Example 2
Production of composition for light emitting layer (L-2) 56.8 g of 20% solid resin solution in which cyanoresin CR-S is dissolved in cyclohexanone, phosphor powder having localized emission center (P- 1) 18.6 g and 24.6 g of cyclohexanone were mixed and dispersed with a shaker for 2 hours to obtain a light emitting layer composition (L-2). The withstand voltage of the light emitting layer formed by the obtained composition for light emitting layer (L-2) was 0.35 MV / cm.

Example 3
Production of composition for light emitting layer (L-3) 76.7 g of a 20% solid resin solution in which cyanoresin CR-S is dissolved in cyclohexanone, phosphor powder having localized emission center (P- 1) 14.7 g and 8.7 g of cyclohexanone were mixed and dispersed with a shaker for 2 hours to obtain a light emitting layer composition (L-3). The withstand voltage of the light emitting layer formed of the obtained composition for light emitting layer (L-3) was 0.50 MV / cm.

Example 4
Production of composition for light emitting layer (L-4) 22.2 g of 20% solid resin solution in which cyanoresin CR-S is dissolved in cyclohexanone, phosphor powder having localized emission center (P- 1) 25.5 g and 52.2 g of cyclohexanone were mixed and dispersed with a shaker for 2 hours to obtain a composition for light emitting layer (L-4). The withstand voltage of the light emitting layer formed of the obtained composition for light emitting layer (L-4) was 0.21 MV / cm.

Example 5
Production of composition for light emitting layer (L-5) 31 g of 20% solid content resin solution of cyanoresin CR-S dissolved in cyclohexanone, 23.8 g of KX-605A and 45.1 g of cyclohexanone were mixed. Then, using a YTZ ball having a diameter of 0.5 mm, the mixture was pulverized and dispersed with a shaker for 3 hours to obtain a composition for light emitting layer (L-5). It was 0.48 micrometer when the average particle diameter of the fluorescent substance powder which has the localization type | mold emission center contained in this composition for light emitting layers (L-5) was measured. The withstand voltage of the light emitting layer formed with the obtained composition for light emitting layer (L-5) was 0.27 MV / cm.

Example 6
Production of composition for light emitting layer (L-6) 31 g of a 20% solid content resin solution of cyanoresin CR-S dissolved in cyclohexanone, 23.8 g of KX-605A and 45.1 g of cyclohexanone were mixed. Then, using a YTZ ball having a diameter of 1.0 mm, the mixture was pulverized and dispersed with a shaker for 3 hours to obtain a light emitting layer composition (L-6). It was 0.92 micrometer when the average particle diameter of the fluorescent substance powder which has the localization type | mold emission center contained in this composition for light emitting layers (L-6) was measured. The withstand voltage of the light emitting layer formed of the obtained composition for light emitting layer (L-6) was 0.25 MV / cm.

Example 7
Production of composition for light emitting layer (L-7) 31 g of a 20% solid resin solution in which cyanoresin CR-S was dissolved in cyclohexanone, 23.8 g of KX-605A and 45.1 g of cyclohexanone were mixed. Then, using a YTZ ball having a diameter of 0.5 mm, the mixture was pulverized and dispersed with a shaker for 12 hours to obtain a composition for light emitting layer (L-7). It was 0.15 micrometer when the average particle diameter of the fluorescent substance powder which has the local type luminescent center contained in this composition for light emitting layers (L-7) was measured. The withstand voltage of the light emitting layer formed by the obtained composition for light emitting layer (L-7) was 0.30 MV / cm.

Example 8
Production of composition for light emitting layer (L-8) 31 g of 20% solid resin solution in which cyanoresin CR-S was dissolved in cyclohexanone, P1-G1 (trade name, localized by Kasei Optonics) Phosphor powder having a luminescent center, Zn ₂ SiO ₄ : Mn) 23.8 g and cyclohexanone 45.1 g are mixed, and pulverized and dispersed with a shaker using a YTZ ball having a diameter of 0.5 mm for 3 hours to emit light A layer composition (L-8) was obtained. It was 0.52 micrometer when the average particle diameter of the fluorescent substance powder which has the local type luminescent center contained in this composition for light emitting layers (L-8) was measured. The withstand voltage of the light emitting layer formed with the obtained composition for light emitting layer (L-8) was 0.26 MV / cm.

Example 9
Production of composition for light emitting layer (L-9) 31 g of a resin solution having a solid content of 20% in which AER ECN-1299 (manufactured by Asahi Kasei Chemicals Corporation, trade name, epoxy resin) was dissolved in cyclohexanone, KX-605A 23.8 g and 45.1 g of cyclohexanone were mixed and pulverized and dispersed with a shaker using a YTZ ball having a diameter of 0.5 mm for 3 hours to obtain a composition for light emitting layer (L-9). It was 0.45 micrometer when the average particle diameter of the fluorescent substance powder which has the local type luminescent center contained in this composition for light emitting layers (L-9) was measured. The withstand voltage of the light emitting layer formed by the obtained composition for light emitting layer (L-9) was 0.30 MV / cm.

Comparative Example 1
Production of composition for light emitting layer (CL-1) 9.2 g of 20% solid content resin solution in which cyanoresin CR-S is dissolved in cyclohexanone, phosphor powder (P-1) having localized emission center 28. 2 g and 62.6 g of cyclohexanone were mixed and dispersed with a shaker for 2 hours to obtain a composition for light emitting layer (CL-1). The withstand voltage of the light emitting layer formed of the obtained composition for light emitting layer (CL-1) was 0.13 MV / cm.

Production Example 2
Manufacture of surface-treated conductive fine particles (a) NanoTek ITO-R (trade name, ITO fine particles, average particle diameter 30 nm) 10 g was mixed in 90 g of deionized water and adjusted to pH 4 with nitric acid, Ultrasonic dispersion was performed for 2 hours. After dispersion, the dispersion was stirred while maintaining at 40 ° C., and 13 g of tetraethoxysilane was slowly added dropwise to the dispersion. After completion of dropping, the mixture was further stirred for 4 hours while being kept at 40 ° C., and then washed with deionized water and acetone and dried under reduced pressure to obtain surface-treated conductive fine particles (a). The obtained surface-treated conductive fine particles (a) were subjected to composition analysis by photoelectron spectroscopy to confirm that silica was surface-treated on the ITO fine particles.

Production Example 3
Production of dielectric composition (D-1) 40.5 g of a 20% solid resin solution in which cyanoresin CR-S was dissolved in cyclohexanone and 6.2 g of surface-treated conductive fine particles (a) were mixed. Then, dispersion was carried out with a shaker for 12 hours to obtain a dielectric composition (D-1).

Production Example 4
Production of dielectric composition (D-2) A resin solution having a solid content of 20% in which cyanoresin CR-S was dissolved in cyclohexanone was prepared as a dielectric composition (D-2).

Example 10
Production of Dispersion EL Element (EL-1) A dielectric composition (D-1) was applied by spin coating on the ITO film surface of a glass substrate (3 cm × 3 cm) on which a transparent conductive layer was formed with an ITO film. And drying on a hot plate at 140 ° C. to form a transparent dielectric layer having a thickness of 1.0 μm. Subsequently, the composition for light emitting layer (L-1) was applied onto the transparent dielectric layer by spin coating, and dried on a hot plate at 140 ° C. to form a light emitting layer having a thickness of 1.0 μm. Subsequently, the dielectric composition (D-1) was applied by spin coating, and dried on a 140 ° C. hot plate to form a dielectric layer having a thickness of 1.0 μm. Furthermore, gold was vapor-deposited on the dielectric layer to produce a dispersion type EL element (EL-1). Table 1 shows the characteristics of the light-emitting layer, the transparent dielectric layer and the dielectric layer of the obtained dispersion type EL element (EL-1) and the light emission luminance of the dispersion type EL element (EL-1).

Examples 11 to 23, Comparative Example 2
Production of dispersion-type EL elements (EL-2) to (EL-14) and (CEL-1) In Example 10, the dielectric composition and the composition for the light emitting layer are those described in Table 1. Dispersion type EL elements (EL-2) to (EL-14) and (CEL-1) were produced in the same manner except that they were changed. In each dispersion-type EL element, the same dielectric composition was used for the transparent dielectric layer and the dielectric layer. Table 1 shows the characteristics of the light emitting layer, the transparent dielectric layer and the dielectric layer of the obtained dispersion type EL element, and the light emission luminance of the dispersion type EL element.

Evaluation test The withstand voltage of the light emitting layer, the capacitance and relative dielectric constant of the dielectric layer, and the light emission luminance of the dispersion type EL element were measured by the following test methods.

Measurement of the withstand voltage of the light emitting layer On the glass substrate (electrode area: 1 cm × 1 cm) on which the ITO electrode was formed, each light emitting layer composition of Examples 1 to 9 was applied with a spin coater so that the film thickness was 3 μm. And it dried on 140 degreeC and the conditions for 30 minutes, and formed the light emitting layer film | membrane. Subsequently, a gold electrode (electrode area: 1 cm × 1 cm) was formed on the light emitting layer film by vapor deposition so as to overlap with the ITO electrode, thereby producing a capacitor-like test body having an electrode area of 1 cm ² . A terminal is applied to each electrode of the test body and connected to a picoammeter 6487 (product name, current-voltage measuring device, manufactured by Caselay Co., Ltd.), and the current value at that time is increased while increasing the voltage by 1V up to a maximum of 500V. I read it. The voltage when the current value exceeded 2.5 mA in the middle of increasing the voltage or the voltage when the gold electrode was destroyed and the current could not be measured was taken as the dielectric breakdown voltage. The breakdown voltage was determined by dividing the dielectric breakdown voltage by the film thickness.

Calculation of Capacitance Density and Dielectric Constant of Dielectric Layer / Creation of Capacitance Measurement Sample On the glass substrate (electrode area: 1 cm × 1 cm) on which the ITO electrode was formed, Production Example 3 and Production Example 4 Each dielectric composition was applied by a spin coater and dried on a hot plate at 140 ° C. to form a dielectric layer having a thickness of 1 μm. Subsequently, gold was deposited on the dielectric layer so as to be paired with the ITO electrode (electrode area: 1 cm × 1 cm), and a sample for measuring capacitance was prepared.
Measurement of capacitance and calculation of capacitance density The capacitance measurement sample prepared above was measured under the conditions of AC 5 V and frequency 1 kHz. For the measurement, LCR HiTester 3532-50 manufactured by Hioki Electric Co., Ltd. was used. Further, the capacitance density σ was calculated by dividing the capacitance value by the electrode area.
The relative dielectric constant of each sample was calculated by the following formula (1) from the value of the capacitance density σ obtained at the calculation destination of the relative dielectric constant and the thickness d (m) of the dielectric layer.
Relative permittivity = (10,000 × σ × d) / e ₀ formula (1)
Dielectric constant e ₀ = 8.82 × 10 ⁻¹² (F / m)

Measurement of emission luminance of dispersion type EL element An AC effective voltage with a frequency of 1 kHz was applied to each of the dispersion type EL elements of Examples 11 to 23, and initial emission luminance at 100V, 125V, 150V, 200V, and 250V was measured. . The luminance was measured using a luminance meter LS-110 manufactured by Konica Minolta Co., Ltd. at a position 5 cm away from the center of the light emitting surface of the dispersion type EL element in the vertical direction.

Claims (10)

A composition for a light emitting layer for forming a light emitting layer of a dispersion type EL device, comprising a phosphor powder having a local emission center and a resin component, and the light emitting layer formed is 0.15 MV / cm or more A light emitting layer composition having a withstand voltage of The composition for a light-emitting layer according to claim 1, wherein the phosphor powder having a local emission center has a 50% average particle size of 0.2 to 2.0 µm based on volume. The dispersion type EL element which has a transparent conductive layer, a light emitting layer, a dielectric material layer, and a back electrode, and a light emitting layer is formed with the composition for light emitting layers of Claim 1 or 2. The dispersion type EL device according to claim 3, wherein the light emitting layer has a thickness of 0.3 to 3.0 μm. The dispersion type EL device according to claim 3 or 4, wherein the light emitting layer contains 1 to 80% by volume of phosphor powder having a localized emission center. The dispersion type EL device according to any one of claims 3 to 5, wherein the dielectric layer contains conductive fine particles and a resin component. The dispersion type EL device according to claim 6, wherein the conductive fine particles are made of a metal oxide. The dispersion type EL device according to claim 6 or 7, wherein the conductive fine particles are surface-treated. The dispersion type EL device according to any one of claims 6 to 8, wherein the dielectric layer contains conductive fine particles in a volume concentration of 5 to 40%. The dispersion type EL element according to any one of claims 3 to 9, wherein the dielectric layer has a relative dielectric constant of 20 or more.