JP2009048961A - Light-emitting element and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element having high brightness and high efficiency by efficiently supplying carriers, especially positive holes to light-emitting particles. <P>SOLUTION: The light-emitting element comprises a first electrode and a second electrode which are installed opposite to each other and of which at least one is transparent or semi-transparent, and a light-emitting layer which is pinched between the first electrode and the second electrode and which is constituted by dispersing the light-emitting particles in a matrix made of positive hole transport materials. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device using an electroluminescence (hereinafter abbreviated as EL) element.

In recent years, among many types of flat-type display devices, expectations have been gathered for display devices using electroluminescent elements. A display device using this EL element has features such as self-luminous property, excellent visibility, wide viewing angle, and quick response. When the EL element is roughly classified, a direct current voltage is applied to a phosphor made of an organic material, an organic EL element that emits light by recombining electrons and holes, and an alternating voltage is applied to the phosphor made of an inorganic material. There is an inorganic EL element that emits light in an inorganic phosphor during the relaxation process, in which electrons accelerated by a high electric field of about 10 ⁶ V / cm collide with the emission center of the inorganic phosphor and are excited.

The organic EL element is a two-layered element in which a hole transport layer and an organic light emitting layer proposed by Tang et al. In 1987 are sequentially stacked (for example, see Non-Patent Document 1) with a driving voltage of 10 V or less. It is said that light emission with a luminance of 1000 cd / m ² or more can be obtained, and this has led to active research and development up to now. However, organic EL elements are still insufficient in terms of compatibility between light emission characteristics such as luminance and long-term reliability, and their use is limited. In the organic EL element, when the luminance is increased, the current density flowing in the driving element increases, and the organic material is deteriorated, aggregated, crystallized, etc. due to Joule heat generation. There is a problem that long-term reliability such as an increase in dark spots is impaired.

  On the other hand, the inorganic EL element shows that the double insulation structure element proposed by Higuchi et al. In 1974 has a high luminance and a long life, and has been put to practical use for a vehicle-mounted display or the like (for example, Patent Documents). 1). In general, an inorganic phosphor is obtained by doping a chemically stable base crystal with an ion or the like serving as a luminescent center, and has excellent long-term reliability. On the other hand, since a high AC voltage is required for driving, there are many problems to use as a high-quality display device, such as inability to perform active driving, inadequate brightness, and efficiency. Not in.

  In recent years, composite light emitting devices that take advantage of both advantages have been proposed. For example, a light-emitting element using inorganic semiconductor ultrafine particles as a light emitter and using an organic hole transporting material or the like has been proposed (for example, see Patent Document 2). FIG. 12 shows a schematic configuration diagram of the light emitting element 110. The light emitting element 110 is configured by laminating an anode 112, a hole transport layer 113, a light emitting layer 114, and a cathode 118 in this order on a substrate 111. The light emitting layer 114 is configured by dispersing semiconductor ultrafine particles 115 having a diameter of about 0.5 nm to 100 nm and an organic hole transport material 116 in a polymer host 117. The anode 112 and the cathode 118 are electrically connected via a power source 129. When a voltage is applied to the power source 129, holes are injected from the anode 112 through the hole transport layer 113 and electrons are injected from the cathode 118 into the light emitting layer 114, respectively, via the polymer host 117 in the light emitting layer 114. The semiconductor ultrafine particles emit light due to the transferred energy. This light emission is extracted from the anode 112 side to the outside of the light emitting element 110.

  In general, in the case of a current excitation type element having an anode and a cathode, such as an organic EL element or a light emitting element 110, in order to obtain highly efficient light emission, a carrier is transferred to a light emitting material (in the case of the light emitting element 110, semiconductor ultrafine particles 115). It is necessary to efficiently inject holes and electrons. However, the above-described conventional example has the advantage of easy area enlargement, but the luminescent material is very small, so it is greatly affected by crystal grain boundaries and surface defects, and generates Joule heat as described above. As a result, deterioration and oxidation are caused, and the luminance and luminous efficiency are significantly impaired. Further, it has been difficult to efficiently inject carriers, particularly holes, into the semiconductor ultrafine particles used as the phosphor particles. As described above, in the above-described conventional example, the advantages of the inorganic light-emitting material cannot be fully utilized, and the level that can be practically satisfied as a display device has not yet been achieved in terms of light emission luminance and light emission efficiency.

Applied Physics Letters, 51, 1987, P913. Japanese Patent Publication No. 52-33491 JP 2004-253175 A

  In view of the above-described problems, the object of the present invention is to form a surface shape relatively easily, and to efficiently supply carriers, particularly holes, to a particulate light emitter. Thus, it is to provide a light-emitting element with high luminance and high efficiency.

  Another object of the present invention is to provide a long-life, high-reliability light-emitting element excellent in oxidation resistance and corrosion resistance of phosphor particles.

  Still another object of the present invention is to provide a display device using the above light emitting element.

A light emitting device according to the present invention is provided opposite to each other, at least one of which is transparent or translucent, a first electrode and a second electrode,
A light emitting layer that is sandwiched between the first electrode and the second electrode, and in which phosphor particles are dispersed in a matrix made of a hole transport material;
It is provided with.

The light emitting device according to the present invention is provided to face each other, at least one of which is transparent or translucent, the first electrode and the second electrode,
A light-emitting layer composed of phosphor particle powder including phosphor particles sandwiched between the first electrode and the second electrode and having at least a part of the particle surface coated with a hole transport material;
It is provided with.

  Furthermore, the light emitting layer may include a binder between the light emitting particles.

さらに、前記有機正孔輸送材料は、下記の化学式３、化学式４、化学式５からなる群の少なくとも一つの構成要素を含んでもよい。

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

Furthermore, the organic hole transport material may 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 may have an average particle diameter of 0.1 μm to 1000 μm.

  You may further provide the positive hole injection layer pinched | interposed between the said 1st electrode and the said light emitting layer.

  You may further provide the support substrate which faces and supports the said 1st electrode or the said 2nd electrode. The support substrate may be a glass substrate or a resin substrate.

  In addition, one or more thin film transistors connected to the first electrode or the second electrode may be further provided.

A display device according to the present invention includes a light emitting element array in which a plurality of the light emitting elements are two-dimensionally arranged,
A plurality of x electrodes extending parallel to each other in a first direction parallel to the light emitting surface of the light emitting element array;
And a plurality of y-electrodes extending in parallel to a second direction orthogonal to the first direction and parallel to a light-emitting surface of the light-emitting element array.

A display device according to the present invention includes a light emitting element array in which a plurality of the light emitting elements are two-dimensionally arranged,
A plurality of signal wires extending in parallel to each other in a first direction parallel to the light emitting surface of the light emitting element array;
A plurality of scanning wirings extending in parallel to a second direction perpendicular to the first direction and parallel to the light emitting surface of the light emitting element array;
One electrode connected to the thin film transistor of the light emitting element array is a pixel electrode corresponding to each intersection of the signal wiring and the scanning wiring, and the other electrode is provided in common for a plurality of light emitting elements. It is characterized by.

  Further, a color conversion layer may be further provided opposite to the first electrode and in front of the light emission extraction direction.

  According to the light emitting element of the present invention, it is possible to form a surface shape relatively easily, and to realize a light emitting element having high luminance, high efficiency, and high reliability and a display device using the light emitting element. can do.

  Hereinafter, a light-emitting element according to an embodiment of the present invention and a display device using the light-emitting element will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(Embodiment 1)
<Schematic configuration of light emitting element>
A light-emitting element 10 according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view perpendicular to the light emitting layer 13 showing a schematic configuration of the light emitting element 10 according to the first embodiment. The light emitting layer 13 containing the phosphor particles 14 is sandwiched between the back electrode 12 that is the first electrode and the transparent electrode 16 that is the second electrode. In order to support them, the substrate 11 is formed adjacent to the back electrode 12. The light-emitting layer 13 is formed by embedding phosphor particles 14 in a hole transport material 15. Further, the back electrode 12 and the transparent electrode 16 are electrically connected via a power source 17. When power is supplied from the power supply 17, a voltage is applied between the back electrode 12 and the transparent electrode 16. At that time, electrons are injected from the back electrode 12 into the phosphor particles 14 in the light emitting layer 13, and holes are injected from the one transparent electrode 16 into the phosphor particles 14 in the light emitting layer 13. The holes and electrons injected into the phosphor particles 14 recombine, and emit light having a wavelength corresponding to the band gap. Light emission passes through the transparent electrode 16 and is extracted outside the light emitting element 10. In the present embodiment, a DC power source is used as the power source 17.

  In addition, it is not restricted to the said structure, It can change suitably, such as providing further the structure which uses the back electrode 12 as a black electrode, and seals all or one part of the light emitting element 10 with resin or ceramics. Furthermore, a modification as shown in FIG. 2 is also possible. The light emitting element 20 shown in FIG. 2 is different from the light emitting element 10 shown in FIG. 1 in that the polarity and arrangement of the electrodes are reversed. Light emitted from the light emitting layer 13 is extracted outside the device through the transparent electrode 16 and the transparent substrate 21. Furthermore, a modification as shown in FIG. 3 is also possible. The light emitting element 30 shown in FIG. 3 is different from the light emitting element 10 shown in FIG. 1 in that a hole injection layer 31 is further provided between the transparent electrode 16 and the light emitting layer 13. As a result, the driving voltage of the light emitting element 30 is lowered, and at the same time, the stability of hole injection from the electrode is improved.

Next, each member which comprises this light emitting element is demonstrated.
<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. 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 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.

<Light emitting layer>
The light emitting layer 13 is configured by dispersing phosphor particles 14 in a hole transport material 15 as a matrix (FIGS. 1, 2, and 3). Note that the light-emitting layer 13 is not limited to this example, and the light-emitting layer 13 is a light-emitting composite in which the entire particle surface of the light-emitting particles 14 is covered with the hole transport material 15 as in the light-emitting layer according to Embodiment 2. A phosphor composite particle 50 (FIG. 6) in which the phosphor particle powder including the particle 50 (FIG. 6A) is formed, or at least a part of the particle surface of the phosphor particle 14 is coated with the hole transport material 15. (B)) may be comprised by the light-emitting body particle powder.

<Phosphor particles>
As the phosphor particles 14, AlN, GaN, InN, AlP, GaP, InP, AlAs, GaAs, and AlSb, which are Group 13-Group 15 compound semiconductors, 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, 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 as a matrix material that covers the surface of the phosphor particles 14 or fills the gaps between the particles 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 transport 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.

<Method for producing light emitting layer>
Next, the manufacturing method of the light emitting layer 13 is demonstrated.
(A) Prepare phosphor particles 14 having a uniform particle size.
(B) The phosphor particles 14 and the organic hole transport material 15 are mixed and stirred.
(C) Thereafter, the organic hole transport material 15 containing the phosphor particles 14 is applied on the back electrode 12, and the phosphor particles 14 are dispersed using the organic hole transport material 15 as a matrix. Layer 13 is formed.
As this coating method, an inkjet method, a dipping method, a spin coating method, a screen printing method, a bar coating method, and other various coating methods can be used. In addition, a spray coating method in which the luminescent particles and the organic hole transport material are sprayed at the same time, an electrostatic coating method, a fluid immersion method, an aerosol deposition method, and the like can be appropriately changed. Furthermore, as another film forming method of the organic hole transport material, a vacuum deposition method or the like may be used.
Alternatively, the light emitting layer 13 may be formed by applying the organic hole transport material 15 after the phosphor particles 14 are fixed on the back electrode 12.

<Hole injection layer>
As shown in FIG. 3, a hole injection layer 31 may be further provided between the light emitting layer 13 and the first electrode 12. As the hole injection layer 31, phthalocyanine, oligoamine, dendrimer amine, polythiophene, vanadium oxide, silicon carbide (SiC), SiO ₂ , amorphous carbon, or the like can be mainly used.

<Features>
Features of the light-emitting element according to the present invention will be described with reference to FIGS. FIG. 4 is a schematic diagram showing a band lineup of the light emitting element 10. Holes are supplied from the transparent electrode (for example, ITO) 16 to the phosphor particles through the HOMO level of the organic hole transport material. On the other hand, from the back electrode (for example, Au) 12, electrons are supplied to the phosphor particles 14 through the LUMO level of the organic hole transport material. The luminescent particles 14 used in the present invention, as represented by GaN, have a larger ionization potential and a larger barrier from the transparent electrode 16 than an organic luminescent material generally used in an organic EL. Therefore, hole injection into the phosphor particles 14 is difficult and an important technical problem. In the present invention, the hole injection property can be improved by embedding the phosphor particles 14 in the organic hole transport material 15. In addition, the phosphor particles 14 grown to a constant particle size have improved crystal grain size and crystallinity, and recombination in a non-light-emitting process is suppressed, and the organic light emission is improved in luminous efficiency. Superior to material. On the other hand, since the electron affinity of the luminescent particles 14 used in the present invention is larger than that of the organic luminescent material generally used in the organic EL, the barrier for the supply of electrons is relatively small. Therefore, the electrons are supplied to the phosphor particles 14 across the barrier between the back electrode 16 and the organic hole transport material 15. Furthermore, the layer thickness of the organic hole transport material 15 coated on the surface of the phosphor particles 14 is thin, and a large electric field strength is applied to this layer made of an organic hole transport material having a higher resistance than the phosphor particles 14. Therefore, in part, electrons are supplied by tunneling. Therefore, an electron transport layer is not particularly required unlike organic EL, and sufficient light emission luminance and light emission efficiency can be realized.

<Effect>
In the light emitting element according to the first embodiment, it is possible to form a surface shape relatively easily, and it is possible to efficiently supply carriers, particularly holes, to the phosphor particles 14. A light-emitting element with high luminance, high efficiency, and high reliability can be realized.

(Example 1)
Luminescent particles mainly composed of GaN and an organic hole transporting material (tetraphenylbutadiene derivative) were mixed and stirred, and then sandwiched with a glass substrate with an ITO electrode together with a spacer to prepare an EL confirmation element. When this device was evaluated by applying a DC voltage, the luminance of emitted light was 220 cd / m ² at 18V. This result was better than the following comparative examples.

(Comparative example)
Using CdSe core / ZnS shell phosphor particles (average particle size 5 nm) synthesized by a hot soap method (for example, described in JP-T-2001-523758), after molecular dispersion in PEDOT / PSS, with ITO electrode It was sandwiched with a spacer on a glass substrate to produce an EL confirmation element. When this device was evaluated by applying a DC voltage, 50 V or more was required for light emission, and the light emission luminance was as low as several tens of cd / m ² .

(Embodiment 2)
<Schematic configuration of light emitting element>
A light-emitting element according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view perpendicular to the light emitting layer showing a schematic configuration of the light emitting element of the second embodiment. Compared with the light emitting element 10 shown in FIG. 1, the light emitting element 40 is configured such that the light emitting layer 13 is made of a phosphor particle powder including the phosphor composite particles 50 shown in FIG. 6A or 6B. Is different. FIG. 6A is a cross-sectional view showing a cross-sectional structure of the phosphor composite particles 50 in which the entire surface of the phosphor particles 14 is coated with the hole transport material 15, and FIG. FIG. 3 is a cross-sectional view showing a cross-sectional structure of phosphor composite particles 50 in which at least a part of the particle surface of particles 14 is coated with a hole transport material 15. The thickness of the coating layer of this hole transport material is in the range of 1 μm to 10 μm, preferably in the range of 2 μm to 3 μm. Further, in this light-emitting element, as compared with the light-emitting element according to Embodiment 1, the phosphor composite particles 50 are disposed between the back electrode 12 and the transparent electrode 16 with the organic binder 41 as a binder. Is different. The feature of the light-emitting element 40 according to Embodiment 2 is that the hole injection property is improved by coating the surface of the phosphor particles 14 with the organic hole transport material 15.

  Note that the present invention is not limited to the above-described configuration, and various modifications may be made as appropriate, such as further including a structure in which the back electrode 12 is a black electrode, and the light-emitting element 40 is entirely or partially sealed with resin or ceramics. Furthermore, a modification as shown in FIG. 7 is also possible. The light emitting element 60 shown in FIG. 7 is different from the light emitting element 40 shown in FIG. 5 in that the polarity and arrangement of the electrodes are reversed. Light emitted from the light emitting layer 13 is extracted outside the device through the transparent electrode 16 and the transparent substrate 21. Furthermore, a modification as shown in FIG. 8 is also possible. The light emitting device 70 shown in FIG. 8 is different from the light emitting device 40 shown in FIG. 5 in that a hole injection layer 31 is further provided between the transparent electrode 16 and the light emitting layer 13. Thereby, the driving voltage of the light emitting element 70 is lowered and the stability of hole injection from the electrode is improved.

<Effect>
In the light-emitting element according to this embodiment, a planar shape can be formed relatively easily, and a light-emitting element with high luminance, high efficiency, and high reliability can be realized.

(Example 2)
The phosphor particles mainly composed of GaN and the organic hole transport material (tetraphenylbutadiene derivative) are mixed and stirred to coat the surface of the phosphor particles with the organic hole transport material, and then further mixed with the organic binder. To paste. This paste was sandwiched with a spacer with a glass substrate with an ITO electrode to prepare an EL confirmation element. When this device was evaluated by applying a DC voltage, the luminance was 250 cd / m ² at 16V. This result was better than the comparative example described above.

(Embodiment 3)
<Schematic configuration of light emitting element>
A light-emitting element according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 9 is a perspective view showing an electrode configuration of the light emitting element 80. The light emitting element 80 further includes a thin film transistor (hereinafter abbreviated as “TFT”; FIG. 9 includes two switching TFTs and two driving TFTs) 85 connected to the pixel electrode 84. A scanning line 81, a data line 82, and a current supply line 83 are connected to the TFT 85. In this light emitting element 80, since light emission is extracted from the transparent common electrode 86 side, the aperture ratio can be increased regardless of the arrangement of the TFTs 85 on the substrate 11. Further, by using the TFT 85, the light emitting element 80 can have a memory function. As this TFT 85, an organic TFT composed of an organic material such as low-temperature polysilicon, amorphous silicon TFT, or pentacene can be used. The TFT 85 may be an inorganic TFT composed of ZnO, InGaZnO ₄ or the like.

(Embodiment 4)
<Schematic configuration of display device>
FIG. 10 is a schematic plan view showing the configuration of the active matrix display device 90 according to Embodiment 4 of the present invention. The display device 90 includes a pixel electrode 84, a common electrode 86, a scanning line 81, a data line 82, a current supply line 83, and a TFT (not shown). The active matrix display device 90 includes a light-emitting element array in which a plurality of light-emitting elements shown in FIG. 9 are two-dimensionally arranged, and extends in parallel to each other in a first direction parallel to the light-emitting surface of the light-emitting element array. A plurality of scanning lines 81, a plurality of data lines 82 extending in parallel to a second direction perpendicular to the first direction and parallel to the light emitting surface of the light emitting element array, and a second direction And a plurality of current supply lines 83 extending in parallel with each other. The TFT on the light emitting element array is electrically connected to the scanning line 81, the data line 82, and the current supply line 83. A light emitting element specified by the pair of scanning lines 81 and data lines 82 is one pixel. Further, in the active matrix display device 90, a current is supplied from the current supply line 83 to the one pixel selected by the scanning line and the data line through the TFT, and the selected light emitting element is driven to obtain the pixel. The emitted light is taken out from the transparent common electrode 86 side.

  In the case of a color display device, the light emitting layer may be formed by color-coding the light emitting particles of each color of RGB. Or you may laminate | stack the light emission unit called an electrode / light emitting layer / electrode for every color of RGB. Furthermore, in the case of a color display device of another example, each color of RGB can be displayed using a color filter and / or a color conversion filter after creating a display device with a single color or two color light emitting layers. For example, by providing a blue light emitting layer with a filter for color conversion from blue to green and from blue to green to red, RGB display is possible.

<Effect>
According to the active matrix display device 90, as described above, the light-emitting layer constituting the light-emitting element of each pixel has the phosphor particles embedded in the organic hole transport material or the phosphor particle surface is the organic hole transport material. Is covered. Thereby, a display device with high emission luminance, high emission efficiency, and high reliability can be realized.

(Embodiment 5)
<Schematic configuration of display device>
A display device according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 11 is a schematic plan view showing a passive matrix display device 100 constituted by a back electrode 12 and a transparent electrode 16 which are orthogonal to each other. The passive matrix display device 100 includes a light emitting element array in which a plurality of light emitting elements are two-dimensionally arranged. A plurality of back electrodes 12 extending parallel to a first direction parallel to the light emitting surface of the light emitting element array; and a first electrode parallel to the light emitting surface of the light emitting element array and orthogonal to the first direction. And a plurality of transparent electrodes 16 extending in parallel to two directions. Further, in the passive matrix display device 100, an external voltage is applied between the pair of back electrodes 12 and the transparent electrode 16 to drive one light emitting element, and the obtained light emission is taken out from the transparent electrode 16 side. In addition, a color display device can be formed in the same manner as the display device in Embodiment 4 described above.

<Effect>
According to this passive matrix display device 100, a display device with high light emission luminance, high light emission efficiency, and high reliability can be realized in the same manner as the display device of the fourth embodiment.

  The light emitting element and the display device according to the present invention can obtain light emission with high light emission luminance and high light emission efficiency and long-term reliability. In particular, it is useful as various light sources used for display devices such as televisions, communication, and illumination.

It is sectional drawing perpendicular | vertical to the light emission surface of the light emitting element which concerns on Embodiment 1 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the modification of the light emitting element which concerns on Embodiment 1 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the modification of the light emitting element which concerns on Embodiment 1 of this invention. It is a figure which shows the energy level in the light emitting element which concerns on Embodiment 1 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the light emitting element which concerns on Embodiment 2 of this invention. (A) And (b) is sectional drawing which shows schematic structure of the light-emitting body composite particle used for the light emitting element which concerns on Embodiment 2 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the modification of the light emitting element which concerns on Embodiment 2 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the modification of the light emitting element which concerns on Embodiment 2 of this invention. It is a schematic perspective view of the light emitting element which concerns on Embodiment 3 of this invention. It is a schematic perspective view of the display apparatus which concerns on Embodiment 4 of this invention. It is a schematic perspective view of the display apparatus which concerns on Embodiment 5 of this invention. It is sectional drawing perpendicular | vertical to the light emission surface of the conventional light emitting element.

Explanation of symbols

10 light emitting element, 11 substrate, 12 back electrode, 13 light emitting layer, 14 phosphor particles,
15 organic hole transport material, 16 transparent electrode, 17 power source, 20 light emitting element,
21 transparent substrate, 30 light emitting element, 31 hole injection layer, 40 light emitting element,
41 organic binder, 50 phosphor composite particles, 60 light emitting element, 70 light emitting element,
80 light emitting elements, 81 scan lines, 82 data lines, 83 current supply lines,
84 pixel electrode, 85 thin film transistor, 86 common electrode, 90 display device,
100 display device, 101 pixel, 110 light emitting element, 111 substrate, 112 anode,
113 hole transport layer, 114 light emitting layer, 115 semiconductive ultrafine particles,
116 hole transport material, 117 polymer binder, 118 cathode, 119 power supply

Claims (17)

A first electrode and a second electrode, provided opposite to each other, at least one of which is transparent or translucent;
A light emitting layer that is sandwiched between the first electrode and the second electrode, and in which phosphor particles are dispersed in a matrix made of a hole transport material;
A light-emitting element comprising: A first electrode and a second electrode, provided opposite to each other, at least one of which is transparent or translucent;
A light-emitting layer composed of phosphor particle powder including phosphor particles sandwiched between the first electrode and the second electrode and having at least a part of the particle surface coated with a hole transport material;
A light-emitting element comprising:   The light emitting device according to claim 2, wherein the light emitting layer includes a binder between the light emitting particles.   The light emitting device according to claim 1, wherein the hole transport material includes an organic hole transport material made of an organic material. 5. The light emitting device according to claim 4, wherein the organic hole transport material contains constituents represented by chemical formula 1 and chemical formula 2 below:

6. The light emitting device according to claim 5, 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 1, 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.   9. The light emitting device according to claim 8, 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 8, wherein the phosphor particles have an average particle diameter in a range of 0.1 μm to 1000 μm.   The light emitting device according to claim 1, further comprising a hole injection layer sandwiched between the first electrode and the light emitting layer.   The light emitting device according to claim 1, further comprising a support substrate that faces and supports the first electrode or the second electrode.   The light emitting device according to claim 12, wherein the support substrate is a glass substrate or a resin substrate.   The light emitting device of claim 13, further comprising one or more thin film transistors connected to the first electrode or the second electrode. A light emitting element array in which the plurality of light emitting elements according to any one of claims 1 to 13 are two-dimensionally arranged,
A plurality of x electrodes extending parallel to each other in a first direction parallel to the light emitting surface of the light emitting element array;
A display device comprising: a plurality of y electrodes that are parallel to a light emitting surface of the light emitting element array and extend parallel to a second direction orthogonal to the first direction. A light emitting element array in which the plurality of light emitting elements according to claim 14 are two-dimensionally arranged;
A plurality of signal wires extending in parallel to each other in a first direction parallel to the light emitting surface of the light emitting element array;
A plurality of scanning wirings extending in parallel to a second direction perpendicular to the first direction and parallel to the light emitting surface of the light emitting element array;
One electrode connected to the thin film transistor of the light emitting element array is a pixel electrode corresponding to each intersection of the signal wiring and the scanning wiring, and the other electrode is provided in common for a plurality of light emitting elements. Display device.   The display device according to claim 15, further comprising a color conversion layer facing the first electrode and in front of the light emission extraction direction.

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