JP2009187770A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element that is driven by low voltage and has a high emission luminance and a long life. <P>SOLUTION: The light-emitting element is provided with a pair of electrodes of which at least one is transparent or translucent, and a luminous layer arranged between the pair of electrodes. The luminous layer is constructed of phosphor compound particles in which the surface of the phosphor particles is covered with a hole transporting material, and conductive nano-particles are interposed in the interface of the luminous layer or one of the electrodes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting device for electroluminescence.

In recent years, electroluminescence elements (hereinafter referred to as EL elements) have attracted attention as light-weight and thin surface-emitting elements. The EL elements are roughly classified to apply a DC voltage to a phosphor made of an organic material, apply an AC voltage to a phosphor made of an inorganic material, and an organic EL element that recombines electrons and holes to emit light. There is an inorganic EL element in which electrons accelerated by a high electric field of ⁶ V / cm collide with a light emission center of an inorganic phosphor to be excited, and the inorganic phosphor emits light in the relaxation process.

  This inorganic EL element includes a dispersion type EL element in which inorganic phosphor particles are dispersed in a binder made of a polymer organic material to form a light emitting layer, and an insulating layer on both sides or one side of a thin film light emitting layer having a thickness of about 1 μm. There is a thin film type EL element provided. Among these, the dispersion-type EL element is attracting attention because it has low power consumption and is easy to manufacture, and thus has an advantage of reducing manufacturing costs.

An EL element 100 called a dispersion type EL element will be described with reference to FIG. A conventional EL element has a layered structure, and includes a substrate 101, a first electrode 102, a light emitting layer 103, an insulator layer 104, and a second electrode 105 in this order from the substrate side. The light emitting layer 103 has a configuration in which inorganic phosphor particles such as ZnS: Mn are dispersed in an organic binder, and the insulator layer 104 has a configuration in which a ferroelectric such as BaTiO ₃ is dispersed in an organic binder. Yes. An AC power source 106 is installed between the first electrode 102 and the second electrode 105, and the EL element 100 emits light when a voltage is applied from the AC power source 106 to the first electrode 102 and the second electrode 105.

  In the structure of the dispersion-type EL element, the light-emitting layer is a layer that determines the luminance and efficiency of the dispersion-type EL element. The inorganic phosphor particles in the light-emitting layer have a particle size of 15 to 35 μm. ing. In addition, the light emission color of the light emitting layer of the dispersion type EL element is determined by the inorganic phosphor particles used in the light emitting layer. For example, when ZnS: Mn is used for the inorganic phosphor particles, orange light is emitted. When ZnS: Cu is used for the particles, blue-green light is emitted.

However, the illuminant used in the EL element has a problem of low emission luminance and short lifetime.
As a method of increasing the light emission luminance, a method of increasing the voltage applied to the light emitting layer can be considered. In this case, there is a problem that the half-life of the light output of the light emitter decreases in proportion to the applied voltage. On the other hand, as a method of increasing the half-life, that is, extending the lifetime, a method of lowering the voltage applied to the light-emitting layer can be considered, but there is a problem that the light emission luminance decreases. Thus, the emission luminance and the half-life are in a relationship in which the other deteriorates when one is improved by increasing or decreasing the voltage applied to the light emitting layer. Therefore, it is necessary to select either emission luminance or half-life. In addition, the half life in this specification is time until the light output of a light-emitting body reduces to the output of half of the original brightness | luminance.

  Therefore, in Patent Document 1, a proposal for driving a light emitting element with a long lifetime and high efficiency has been made. According to this, by dispersing the needle-shaped material having higher conductivity than the phosphor in the organic binder of the light emitting layer, the needle-shaped material becomes a charge supply source, and high-energy electrons are efficiently injected into the phosphor. It is possible to provide a highly efficient and long-life distributed EL.

JP 2002-33193 A

  However, since the above structure is an electroluminescent dispersion type EL, an alternating high voltage needs to be applied between the electrodes in order to emit light. As a result, there is a problem that, in principle, it is difficult to obtain high efficiency at the time of applying a high voltage, and it is difficult to extend the life.

  An object of the present invention is to solve the above-described problems, and to provide a light-emitting element that is driven at a low voltage, has high emission luminance, and has a long lifetime.

The said subject is achieved by the following light emitting elements. That is, the light-emitting element according to the present invention includes a pair of electrodes, at least one of which is transparent or translucent,
A light emitting layer disposed between the pair of electrodes;
With
The light emitting layer is composed of phosphor composite particles in which the surface of the phosphor particles is covered with a hole transport material,
Conductive nanoparticles are interposed at the interface between the light emitting layer and one of the electrodes.

  Conductive nanoparticles may be supported on one electrode interface of the electrode.

  Conductive nanoparticles may be supported on the positive electrode of the electrodes. The conductive nanoparticles supported on the electrode interface on the positive electrode side preferably have a work function of 4.5 eV or more.

  Conductive nanoparticles may be supported on the negative electrode of the electrodes. The conductive nanoparticles supported on the electrode interface on the negative electrode side preferably have a work function of less than 3.5 eV.

  The conductive nano particles may include at least one metal fine particle selected from the group consisting of Ag, Au, Pt, Ni, and Cu. The conductive nanoparticles may include at least one oxide fine particle selected from the group consisting of indium tin oxide, ZnO, and InZnO. Further, the conductive nano particles may include at least one carbon fine particle selected from the group of fullerene and carbon nanotube.

  The average particle size of the conductive nanoparticles is preferably in the range of 1 to 200 nm.

  The light emitting layer may be configured by dispersing phosphor composite particles in which an organic binder is used as a medium and the surface of the phosphor particles is covered with a hole transport material.

The hole transport material may include an organic hole transport material made of an organic material. In addition, the organic hole transport material may further contain components of the following chemical formula 1 and chemical formula 2.

The organic hole transport material may further include at least one component of the group consisting of the following chemical formula 3, chemical formula 4, and chemical formula 5.

  The hole transport material may include an inorganic hole transport material made of an inorganic material.

  The phosphor particles may include particles made of a Group 13-Group 15 compound semiconductor. The phosphor particles may be nitride semiconductor particles containing at least one element of Ga, Al, and In. The phosphor particles preferably have an average particle diameter in the range of 0.1 μm to 1000 μm. The phosphor particles may be selected from light emitting materials composed of nitrides, sulfides, selenides, and oxides.

  According to the present invention, it is possible to increase recombination with electrons by effectively injecting holes into a light emitter, and it is possible to provide a light emitting element with high luminance and high efficiency at a low voltage.

  The best mode for carrying out the invention will be described below.

(Embodiment 1)
<Schematic configuration of EL element>
FIG. 1 is a schematic cross-sectional view showing the configuration of the light-emitting element 10 according to the first embodiment. The light emitting element 10 includes a back electrode 12 as a first electrode, a transparent electrode 16 as a second electrode, and a light emitting layer 13 sandwiched between the pair of electrodes 12 and 16. The light emitting layer 13 is composed of phosphor composite particles in which the surface of the phosphor particles 14 is covered with a hole transport material 15. Further, a DC power source 17 is connected between the back electrode 12 as the first electrode and the transparent electrode 16 as the second electrode. In the light emitting element 10, conductive nanoparticles 23 are supported on the interface of the back electrode 12 on the positive electrode side. When electric power is supplied between the electrodes 12 and 16, a potential difference is generated between the back electrode 12 and the transparent electrode 16, and a voltage is applied. And it is a carrier from the back electrode 12 on the positive electrode side and the transparent electrode 16 on the negative electrode side through the conductive nano particles 23 on the electrode surface on the positive electrode side and the hole transport material 15 covering the surface of the phosphor particles 14. Holes and electrons are injected into the phosphor particles 14 and recombined to emit light. Light emission is taken out from the transparent electrode 16 side.

  Note that the present invention is not limited to the above-described configuration, and changes can be made as appropriate, such as replacing the back electrode 12 and the transparent electrode 16, making both the electrode 12 and the electrode 16 transparent electrodes, or changing the power source to an AC power source. Further, as shown in FIG. 2, the structure of the light emitting layer 13 is a structure in which phosphor composite particles in which the surface of the phosphor particles 14 is covered with a hole transport material 15 are dispersed in an organic binder 41. Also good.

  In the light emitting element 10, the surface of the phosphor particles 14 is covered with the hole transport material 15, and the conductive nanoparticles 23 are supported on the electrode surface on the positive electrode side. High brightness and high efficiency can be obtained with direct current and low voltage.

Hereafter, each structural member of this light emitting element is explained in full detail using FIG.1 and FIG.2.
<Board>
In FIG. 1, a substrate 11 that can support each layer formed thereon is used. Specifically, ceramics such as silicon, Al ₂ O ₃ , and AlN can be used. Furthermore, a plastic substrate such as polyester or polyimide may be used. Moreover, when taking out light from the board | substrate 11 side, it is calculated | required that it is a material which has a light transmittance with respect to the wavelength of the light emitted from a light-emitting body. As such a material, for example, glass such as Corning 1737, quartz, or the like can be used. It may be non-alkali glass or soda lime glass in which alumina or the like is coated on the glass surface as an ion barrier layer so that alkali ions contained in ordinary glass do not affect the light emitting element. These are merely examples, and the material of the substrate 11 is not particularly limited thereto.
Further, in the case of a structure in which light is not extracted from the substrate side, the above-described light transmittance is unnecessary, and a material that does not have light transmittance can be used.

<Electrode>
The electrodes include a back electrode 12 and a transparent electrode 16. Of these two electrodes, the electrode on the light extraction side is the transparent electrode 16 and the other is the back electrode 12.
The material of the transparent electrode 16 on the light extraction side may be any material as long as it has a light transmission property so that the light emitted in the light emitting layer 13 can be extracted, and preferably has a high transmittance in the visible light region. Moreover, it is preferable that it is low resistance, and also it is preferable that it is excellent in adhesiveness with the light emitting layer 13. FIG. Furthermore, it is more preferable that the light emitting layer 13 can be formed at a low temperature so that the light emitting layer 13 is not thermally deteriorated when it is formed on the light emitting layer 13. As a material for the transparent electrode 16, a metal mainly composed of ITO (In ₂ O ₃ doped with SnO ₂ , also referred to as indium tin oxide), InZnO, ZnO, SnO ₂ or the like is mainly used. Examples include oxides, metal thin films such as Pt, Au, Pd, Ag, Ni, Cu, Al, Ru, Rh, and Ir, or conductive polymers such as polyaniline, polypyrrole, PEDOT / PSS, and polythiophene. It is not limited to these. The volume resistivity of the transparent electrode 16 is 1 × 10 ⁻³ Ω · cm or less, the transmittance is 75% or more at a wavelength of 380 to 780 nm, and the refractive index is 1.85 to 1.95. It is desirable to be. For example, ITO can be formed by a film forming method such as sputtering, electron beam evaporation, or ion plating for the purpose of improving the transparency or reducing the resistivity. Further, after film formation, surface treatment such as plasma treatment may be performed for the purpose of resistivity control. The film thickness of the transparent electrode 16 is determined from the required sheet resistance value and visible light transmittance. The transparent electrode 16 may be formed directly on the light emitting layer 13, but the transparent electrode 16 made of a transparent conductive film is formed on a glass substrate and bonded so that the transparent conductive film and the light emitting layer 13 are in direct contact with each other. May be.

The back electrode 12 on the side from which light is not extracted may be any electrode as long as it has conductivity and has excellent adhesion to the substrate 11 and the light emitting layer 13. Suitable examples include metal oxides such as ITO, InZnO, ZnO, SnO ₂ , Pt, Au, Pd, Ag, Ni, Cu, Al, Ru, Rh, Ir, Cr, Mo, W, Ta, and Nb. Metals such as these, laminated structures of these, or conductive polymers such as polyaniline, polypyrrole, PEDOT [poly (3,4-ethylenedioxythiophene)] / PSS (polystyrene sulfonic acid), or conductive carbon Can be used.

  The back electrode 12 may be configured so as to cover the entire surface of the layer, and a plurality of electrodes may be configured in a stripe shape in the layer. Further, the back electrode 12 and the transparent electrode 16 are configured by forming a plurality of electrodes in a stripe shape, and each stripe electrode of the back electrode 12 and all of the stripe electrodes of the transparent electrode 16 have a twist position relationship. In addition, a configuration in which each stripe-shaped electrode of the back electrode 12 is projected onto the light-emitting surface and a projection of all the stripe-shaped electrodes of the transparent electrode 16 onto the light-emitting surface may intersect with each other. . In this case, it is possible to configure a display that emits light at a predetermined position by applying a voltage to each stripe-shaped electrode of the back electrode 12 and each stripe-shaped electrode of the transparent electrode 16. It becomes. The same applies to the configuration of FIG.

<Conductive nanoparticles>
In the light emitting element 10 according to Embodiment 1 of the present invention, conductive nanoparticles 23 are supported on the interface of the electrode 12 on the positive electrode side. Furthermore, as shown in the light-emitting element according to Embodiment 2, conductive nanoparticles 24 may be supported on the electrode interface on the negative electrode side. The conductive nanoparticles 23 and 24 used in the light-emitting element include metal material particles such as Ag, Au, Pt, Ni, and Cu, oxide particles such as indium tin oxide, ZnO, and InZnO, and carbon such as carbon nanotubes. Material particles can be used. The shape of the conductive nanoparticles 23 may be any shape such as granular, spherical, columnar, acicular, or indefinite. The average particle diameter or average length of the conductive nanoparticles 23 is preferably in the range of 1 nm to 200 nm. When the thickness is smaller than 1 nm, the conductivity is deteriorated and the light emission luminance is lowered. On the other hand, if it is larger than 200 nm, electrical conduction between the electrodes increases, but the number of luminescent particles 14 that are not included in the conductive path increases, and the emission luminance and efficiency are greatly reduced.

  Carbon nanotubes are produced by a method such as a gas phase synthesis method or a plasma method, and the electrical characteristics, diameter, length, etc. of the carbon nanotubes can be arbitrarily changed depending on the production conditions. When the carbon nanotube is supported on the electrode interface on the positive electrode side, it is preferable to use the p-type. When carrying on the electrode interface of the negative electrode side, it is preferable to use n type. The p-type can be obtained by adding a group 5 element such as phosphorus to the carbon nanotube. On the other hand, the n-type can be obtained by adding a group 3 element such as nitrogen.

<Light emitting layer>
The light emitting layer 13 is composed of phosphor composite particles in which the surface of the phosphor particles 14 is covered with a hole transport material 15 (FIGS. 1 and 3). The light emitting layer 13 is not limited to this example. The light emitting layer 13 may be configured by dispersing phosphor composite particles in which the surface of the phosphor particles 14 is covered with the hole transport material 15 in the organic binder 41 (FIG. 2, FIG. 4).

<Phosphor particles>
Any material can be used as the phosphor particles 14 as long as the optical band gap has a visible light size. Specifically, a Group 13-Group 15 compound semiconductor such as AlN, GaN, InN, AlP, GaP, InP, AlAs, GaAs, AlSb, or the like can be used. In particular, a group 13 nitride semiconductor represented by GaN is preferable. Moreover, these mixed crystals (for example, GaInN etc.) may be sufficient. Furthermore, in order to control conductivity, one or more elements selected from the group consisting of Si, Ge, Sn, C, Be, Zn, Mg, Ge, and Mn may be included as a dopant.

  Further, nitrides such as InGaN and AlGaN, ZnSe and ZnS, ZnS, ZnSe, GaP, CdSe, CdTe, SrS, CaS, and ZnO are used as a base material, or they are used as they are, or as additives, Ag, Al, Phosphor particles to which one or more elements selected from Ga, Cu, Mn, Cl, Tb, and Li are added can be used. In addition, multi-component compounds such as ZnSSe and thiogallate phosphors can also be used.

  Further, in the phosphor particles 14, the plurality of compositions may form a layered structure or a segregated structure. The particle size of the phosphor particles 14 may be in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.5 μm to 500 μm.

<Hole transport material>
Next, the hole transport material 15 that covers the surface of the phosphor particles 14 will be described. The hole transport material 15 includes an organic hole transport material and an inorganic hole transport material. The hole transport material 15 is preferably a material having a high hole mobility.

<Organic hole transport material>
As this organic hole transport material, it is preferable to include the following structural formula 6 and chemical formula 7.

  It is considered that the effect of the organic hole transport material containing the constituents of the above chemical formulas 6 and 7 is that holes are efficiently injected into the phosphor particles 14.

Further, as the organic hole transport material, any one of the following chemical formula 8, chemical formula 9, and chemical formula 10 may be included as a constituent element.

Organic hole transport materials are roughly classified into low molecular weight materials and high molecular weight materials. Examples of the low molecular weight material having a hole transporting property include N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine (TPD), N, N′-bis (α-naphthyl) -N , N′-diphenylbenzidine (NPD) and the like, and diamine derivatives used by Tang et al., In particular, diamine derivatives having a Q1-GQ2 structure disclosed in Japanese Patent No. 2037475, and the like. Q1 and Q2 are groups separately having a nitrogen atom and at least three carbon chains (at least one of which is aromatic). G is a linking group comprising a cycloalkylene group, an arylene group, an alkylene group, or a carbon-carbon bond. Moreover, the multimer (oligomer) containing these structural units may be sufficient. These include those having a spiro structure or a dendrimer structure. Furthermore, a form in which a low molecular weight hole transport material is molecularly dispersed in a non-conductive polymer is also possible. As a specific example of the molecular dispersion system, there is an example in which TPD is molecularly dispersed at a high concentration in polycarbonate, and its hole mobility is about 10 ⁻⁴ to 10 ⁻⁵ cm ² / Vs.

On the other hand, examples of the high molecular weight material having a hole transporting property include a π conjugated polymer and a σ conjugated polymer, and for example, a material in which an arylamine compound or the like is incorporated. Specifically, poly-para-phenylene vinylene derivative (PPV derivative), polythiophene derivative (PAT derivative), polyparaphenylene derivative (PPP derivative), polyalkylphenylene (PDAF), polyacetylene derivative (PA derivative), polysilane derivative ( PS derivatives) and the like, but are not limited thereto. Furthermore, it may be a polymer in which a molecular structure showing a hole transport property in a low molecular system is incorporated in a molecular chain. Specific examples thereof include polymethacrylamide having an aromatic amine in a side chain (PTPAMMA, PTPDMA). And polyether having an aromatic amine in the main chain (TPDPES, TPPEK). Among them, as a particularly preferable example, poly-N-vinylcarbazole (PVK) exhibits extremely high hole mobility of 10 ⁻⁶ cm ² / Vs. Other specific examples include PEDOT / PSS and polymethylphenylsilane (PMPS).
Furthermore, a plurality of the hole transport materials described above may be mixed and used. Further, it may contain a crosslinkable or polymerizable material that is crosslinked or polymerized by light or heat.

<Inorganic hole transporting material>
The inorganic hole transporting material will be described. The inorganic hole transporting material may be any material that is transparent or translucent and exhibits p-type conductivity. Preferred examples include semi-metal semiconductors such as Si, Ge, SiC, Se, SeTe, As ₂ Se ₃ , binary compound semiconductors such as ZnS, ZnSe, CdS, ZnO, and CuI, CuGaS ₂ , CuGaSe ₂ , CuInSe. _And chalcopyrite type semiconductors such as ₂ , mixed crystals thereof, oxide semiconductors such as CuAlO ₂ and CuGaO ₂ , and mixed crystals thereof. Still further, dopants may be added to these materials to control conductivity.

(Modification 1)
FIG. 2 is a schematic cross-sectional view showing the configuration of the light emitting element 10a according to the first modification of the first embodiment. Compared with the light-emitting element 10 according to Embodiment 1, the light-emitting element 10 a has a light-emitting layer 13 in which the surface of the light-emitting particle 14 is covered with the hole transport material 15 using the organic binder 41 as a medium. Are different in that they are distributed.

<Organic binder>
In the light emitting layer 13 of the light emitting element 10a in the modified example, the organic binder 41 for dispersing the phosphor composite particles in which the surface of the phosphor particles 14 is covered with the hole transport material 15 can be used as long as it is a resin solution or the like. .

Example 1
As Example 1 of the present invention, a method of obtaining the light emitting device of FIG. 1 by a coating method will be described. As an example, a light emitting device as shown in FIG. 1 was manufactured.
(A) First, about 300 nm of a Pt film 12 was formed on the silicon substrate 11 as a back electrode by sputtering.
(B) Next, Fe nanoparticles having an average particle diameter of 1 to 3 nm were formed on the Pt film 12 by the same sputtering method. Then, the substrate was heated to about 800 ° C., and hydrocarbon gas was introduced into the chamber to grow carbon nanotubes 23 as conductive nanoparticles. The obtained carbon nanotubes had a diameter of 1 to 10 nm and a length of 50 to 120 nm.
(C) Next, GaN particles having an average particle diameter of 500 to 1000 nm as the luminescent particles 14 are mixed with the tetraphenylbutadiene T770, which is the hole transport material 15 dissolved in the resin solution, to obtain the luminescent particles 14. The surface of the substrate was coated with a hole transport material 15 and dried. Thus, phosphor composite particles in which the surface of the phosphor particles 14 was covered with the hole transport material 15 were obtained.
(D) Next, phosphor composite particles in which the surface of the phosphor particles 14 is covered with the hole transport material 15 are mixed with a volatile solvent solution to obtain a phosphor paste. After coating on the Pt film 12 carrying 23, it was dried. The thickness of the coating film was about 30 μm. Thus, the light emitting layer 13 made of the phosphor composite particles in which the surface of the phosphor particles 14 was covered with the hole transport material 15 was formed.
(E) A substrate in which an ITO film 16 which is a transparent conductive film was formed on a glass plate by a sputtering method was used as the opposing substrate with a transparent electrode. The film thickness of the ITO film 16 was about 300 nm.
(F) Subsequently, the ITO film 16 was attached so that the surface of the ITO film 16 was in contact with the light emitting layer 13 described above.
Thus, the light emitting element 10 was obtained.

The evaluation was performed by applying a DC voltage between the back electrode 12 and the transparent electrode 16. The luminance measurement was performed using a portable luminance meter. As a result, blue-green light emission was started at a DC voltage of about 4 V, and an emission luminance of about 6000 cd / m ² was obtained at 8 V.
As described above, according to the present invention, a light-emitting element that is direct current, low voltage, and high brightness can be obtained.

<Effect>
The light-emitting elements 10 and 10a according to Embodiment 1 were superior to the conventional light-emitting element in terms of charge injection, and were able to obtain high luminance and long life.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view showing the configuration of the light-emitting element 20 according to Embodiment 2 of the present invention. The light emitting element 20 is different from the light emitting element according to Embodiment 1 in that another conductive nanoparticle 24 is supported on the electrode interface on the negative electrode side. Electrons can be injected into the phosphor particles 14 through the conductive nanoparticles 24 carried on the negative electrode side transparent electrode 16.

(Modification 2)
FIG. 4 is a schematic cross-sectional view showing a configuration of a light emitting element 20a according to Modification 2 of Embodiment 2 of the present invention. Compared with the light emitting element 20 according to the second embodiment, the light emitting element 20a is a phosphor composite particle in which the light emitting layer 13 covers the surface of the phosphor particle 14 with the hole transport material 15 using the organic binder 41 as a medium. Are different in that they are distributed.

(Example 2)
As Example 2 of the present invention, a method for manufacturing the light-emitting element 20 shown in FIG. 3 by a coating method will be described.
(A) First, about 300 nm of a Pt film 12 was formed on the silicon substrate 11 as a back electrode by sputtering.
(B) Next, Fe nanoparticles having an average particle diameter of 1 to 3 nm were formed on the Pt film 12 by the same sputtering method. Then, the substrate was heated to about 800 ° C., and hydrocarbon gas was introduced into the chamber to grow carbon nanotubes 23 as conductive nanoparticles. The obtained carbon nanotubes had a diameter of 1 to 10 nm and a length of 50 to 120 nm.
(C) Next, GaN particles having an average particle diameter of 500 to 1000 nm as the luminescent particles 14 are mixed with the tetraphenylbutadiene T770, which is the hole transport material 15 dissolved in the resin solution, to obtain the luminescent particles 14. The surface of the substrate was coated with a hole transport material 15 and dried. Thus, phosphor composite particles in which the surface of the phosphor particles 14 was covered with the hole transport material 15 were obtained.
(D) Next, the phosphor composite particles in which the surface of the phosphor particles 14 obtained by the DuPont resin solution was covered with the hole transport material 15 were sufficiently mixed to obtain a phosphor paste.
(E) The produced phosphor paste was applied on the Pt film 12 carrying the carbon nanotubes 23 and dried. The thickness of the coating film was about 30 μm.
(F) As the opposing substrate with a transparent electrode, a substrate in which an ITO film 16 as a transparent conductive film was formed on a glass plate by a sputtering method was used. The film thickness was about 300 nm.
(G) Next, ITO nanoparticles 24 as conductive nanoparticles were supported on the surface of the ITO film 16 by the AD method.
(H) Subsequently, the surface of the ITO film 16 carrying the ITO nanoparticles 24 on the surface was pasted so as to be in contact with the phosphor paste.
Thus, the light emitting element 20 was obtained.

The evaluation was performed by applying a DC voltage between the back electrode 12 and the transparent electrode 16. The luminance measurement was performed using a portable luminance meter. As a result, orange light emission was started at a DC voltage of about 4 V, and a light emission luminance of about 5000 cd / m ² was obtained at 12 V.
As described above, according to the present invention, it is possible to obtain a light-emitting element having high luminance with direct current and low voltage.

  Since the light-emitting element of the present invention has high emission luminance, it can be used for LCD backlights, illumination, displays, and the like.

It is a schematic sectional drawing which shows the structure of the light emitting element which concerns on Embodiment 1 of this invention. It is a schematic sectional drawing which shows the structure of the light emitting element which concerns on the modification 1 of Embodiment 1 of this invention. It is a schematic sectional drawing which shows the structure of the light emitting element which concerns on Embodiment 2 of this invention. It is a schematic sectional drawing which shows the structure of the light emitting element which concerns on the modification 2 of Embodiment 2 of this invention. It is a schematic sectional drawing which shows the structure of the conventional light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Substrate 12 Back electrode 13 Luminous layer 14 Luminescent particle 15 Hole transport material 16 Transparent electrode 17 Power supply 23 Conductive nanoparticle A
24 Conductive nanoparticles B
41 Organic Binder 100 Light-Emitting Element 101 Substrate 102 First Electrode 103 Light-Emitting Layer 104 Insulator Layer 105 Second Electrode 106 AC Power Supply

Claims (19)

A pair of electrodes, at least one of which is transparent or translucent,
A light emitting layer disposed between the pair of electrodes;
With
The light emitting layer is composed of phosphor composite particles in which the surface of the phosphor particles is covered with a hole transport material,
Conductive nanoparticles are interposed at the interface between the light emitting layer and one of the electrodes, and the light emitting element.   The light-emitting element according to claim 1, wherein conductive nanoparticles are supported on one electrode interface of the electrode.   The light-emitting element according to claim 2, wherein conductive nanoparticles are supported on the positive electrode of the electrodes.   4. The light emitting device according to claim 3, wherein the conductive nanoparticles supported on the electrode interface on the positive electrode side have a work function of 4.5 eV or more.   The light-emitting element according to claim 2, wherein conductive nanoparticles are supported on a negative electrode of the electrodes.   The light emitting device according to claim 5, wherein the conductive nanoparticles supported on the electrode interface on the negative electrode side have a work function of less than 3.5 eV.   2. The light emitting device according to claim 1, wherein the conductive nanoparticles include at least one metal fine particle selected from the group consisting of Ag, Au, Pt, Ni, and Cu.   2. The light emitting device according to claim 1, wherein the conductive nanoparticles include at least one oxide fine particle selected from the group consisting of indium tin oxide, ZnO, and InZnO.   The light emitting device according to claim 1, wherein the conductive nanoparticles include at least one carbon fine particle selected from the group consisting of fullerene and carbon nanotube.   The light emitting device according to claim 1, wherein an average particle diameter of the conductive nanoparticles is in a range of 1 to 200 nm.   2. The light emitting device according to claim 1, wherein the light emitting layer is configured by dispersing phosphor composite particles in which a surface of a phosphor particle is covered with a hole transport material using an organic binder as a medium.   The light emitting device according to claim 11, wherein the hole transport material includes an organic hole transport material made of an organic material. The light emitting device according to claim 12, wherein the organic hole transport material contains constituents represented by chemical formula 1 and chemical formula 2 below.

The light emitting device according to claim 13, wherein the organic hole transport material further includes at least one component of the group consisting of the following chemical formula 3, chemical formula 4, and chemical formula 5.

  The light emitting device according to claim 11, wherein the hole transport material includes an inorganic hole transport material made of an inorganic substance.   The light emitting device according to claim 1, wherein the phosphor particles include particles made of a Group 13-Group 15 compound semiconductor.   The light emitting device according to claim 16, wherein the phosphor particles are nitride semiconductor particles containing at least one element of Ga, Al, and In.   The light emitting device according to claim 16, wherein the phosphor particles have an average particle diameter of 0.1 μm to 1000 μm.   The light emitting device according to claim 1, wherein the phosphor particles are selected from a light emitting material made of nitride, sulfide, selenide, or oxide.

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