JP2011150821A - Electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroluminescent element having an optical resonance structure in which variation of chromaticity at a low viewing angle in a high viewing angle is controlled. <P>SOLUTION: The electroluminescent element is provided with an resonator 19 composed of two facing reflection mirrors 11, 17 arranged in parallel to a laminated face of a plurality of layers so that light emitted from a light emitting region 15 may be resonated, and there are provided in the resonator 19 particulates having a peak of scattering and/or absorption against a resonator wavelength in a high angle region having an inclination more than 30°against an optical axil A perpendicular to the reflection mirrors 11, 17. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electroluminescence element (electroluminescence element) that emits light by application of an electric field, and particularly relates to an electroluminescence element that achieves high efficiency of light emission.

  An electroluminescence element (EL element) such as an organic EL element, LED (light emitting diode), or semiconductor laser has a structure in which an electrode layer, a light emitting layer, or the like is laminated on a substrate. Is taken out through the transparent electrode. At that time, due to the influence of the refractive index of each layer, light incident at a critical angle or more at the layer interface on the light extraction side is totally reflected and confined in the element and cannot be extracted outside. For this reason, it is difficult to extract emitted light with high efficiency, and it is said that the extraction efficiency is about 20% in the case of the refractive index of a currently used transparent electrode such as ITO.

In an organic EL element, a method using a microcavity effect is known in order to improve luminous efficiency. Non-Patent Document 1 describes that directivity and utilization efficiency (extraction efficiency) can be improved by applying a microcavity structure in an organic EL element.
When the microcavity effect is used in an electroluminescence element, the luminance and chromaticity at a viewing angle of 0 ° (front of the element) perpendicular to the element surface can be improved.

"Sharply directed emission in organic electroluminescent diodes with an optical-microcavity structure" Applied Physics Letters, 65 (15), 10 October 1994, p.1868-1870

However, when the microcavity effect is used, the spectrum when observed from the wide-angle side where the viewing angle is greatly deviated from 0 ° is greatly changed from the spectrum when observed from the viewing angle of 0 °, and the chromaticity is changed. There is a problem.
When the EL element is applied to a display device, the chromaticity shift at a high viewing angle is not preferable, and it is desired to suppress the chromaticity shift at a high viewing angle.
The present invention has been made in view of the above circumstances, and provides an EL element that suppresses the chromaticity shift at a high viewing angle while maintaining the front luminance and chromaticity improvement effects by the microcavity. Objective.

The electroluminescence device of the present invention is an electroluminescence device comprising a light emitting region that emits light by applying an electric field between the electrodes, between a plurality of layers stacked between electrodes,
A resonator composed of two opposing reflecting mirrors arranged in parallel to the laminated surface of the plurality of layers so as to resonate the light emitted from the light emitting region;
Fine particles having scattering and / or absorption peaks with respect to the resonator wavelength in a high angle region having an inclination of more than 30 ° with respect to the optical axis perpendicular to the reflecting mirror are provided inside the resonator. It is a feature.

  Here, the electroluminescence element is a general term for elements that emit light when an electric field is applied, and includes an organic EL element, an inorganic EL element, a light emitting diode (LED), and a semiconductor laser (LD).

  Here, the peak of scattering and / or absorption refers to the peak of the scattering spectrum in the case of fine particles that only cause scattering, the peak of the absorption spectrum in the case of fine particles that cause only absorption, and the case of fine particles that cause scattering and absorption. Means the peak of the disappearance spectrum indicated by the sum of the scattering spectrum and the absorption spectrum.

  In the case of an organic EL element, the plurality of layers are preferably composed of at least an electron transport layer, a light emitting layer, and a hole transport layer, each formed from an organic layer. In the case of an LED or LD, the plurality of layers are preferably each composed of a semiconductor layer, at least a p-type cladding layer, an active layer, and an n-type cladding layer.

  In the EL element of the present invention, it is desirable that at least one of the two opposing reflecting mirrors also serves as one of the electrodes. However, two opposing reflecting mirrors and electrodes may be provided individually.

The fine particles can be composed of metal fine particles or dielectric fine particles.
The metal fine particles are preferably made of at least one selected from the group consisting of Au, Ag, Al, Pt, Cu, and alloys containing these metals as main components. Further, when a dielectric fine particles is preferably a relatively high refractive index, it is preferably made of at least one selected from the group consisting of TiO _2, SiO ₂ and ZnSe.

  The fine particles can be composed of pigments or quantum dots. A dye or quantum dot is an absorber that absorbs a predetermined wavelength, and by dispersing the dye or quantum dot in a binder, a color filter that passes a specific wavelength range of visible light and blocks a specific wavelength range is provided. Can be configured. In other words, a color filter can be provided between the layers constituting the resonator or in the layers. The binder may be an organic layer material constituting an electron transport layer, a light emitting layer, a hole transport layer, or the like, or may be composed of other organic substances, resin, glass, or the like.

  Each of the two opposing reflecting mirrors is preferably made of at least one selected from the group consisting of Al, Ag, Mg, Ca, and alloys containing these metals as main components.

  In the present specification, the “main component” is defined as a component having a content of 80% by mass or more.

  Since the electroluminescent element of the present invention has a resonator formed in the element, the directivity of light emission can be improved and light emission can be enhanced. On the other hand, since the inside of the resonator has fine particles having scattering and / or absorption peaks with respect to the resonator wavelength in a high angle region having an inclination of more than 30 ° with respect to the optical axis perpendicular to the reflecting mirror. The change in chromaticity from the front chromaticity at a viewing angle higher than 30 ° can be suppressed.

The schematic diagram which shows the structure of the EL element concerning 1st Embodiment of this invention. Diagram showing an example of color filter characteristics The schematic diagram which shows the structure of the EL element concerning 2nd Embodiment of this invention. Diagram showing an example of the disappearance spectrum of fine particles

  Embodiments of the present invention will be described with reference to the drawings. In each figure, the scales of the components are appropriately changed from the actual ones for easy visual recognition.

<EL Element of First Embodiment>
FIG. 1 is a diagram schematically showing the structure of an electroluminescence element (EL element) 1 according to a first embodiment of the present invention. The EL element 1 of the present embodiment is an organic EL element in which each layer is composed of an organic layer.

The organic EL element 1 of the present embodiment includes a first reflecting mirror 11, a color filter 12, a cathode 13 made of a transparent material, an electron transport layer 14, a light emitting layer 15, and a hole transport on a transparent substrate 10 made of glass or the like. The layer 16 and the anode 17 made of a translucent metal are laminated in this order.
That is, it has a general organic EL element configuration including a plurality of layers 14 to 16 including at least a light emitting layer between two electrodes 13 and 17, and further, a reflecting mirror 11 for forming a resonator, and a color filter 12 is provided.

  The light emitting layer 15 is a light emitting region that emits light by recombination of electrons and holes injected from the cathode 13 and the anode 17, and is not particularly limited as long as it can be applied as a light emitting layer of an organic EL element. A material may be selected according to a desired emission wavelength.

The anode 17 is made of a translucent metal and serves also as a second reflecting mirror, and constitutes a resonator 19 together with the first reflecting mirror 11 arranged to face the anode 17.
When an electric field is applied between the electrodes 13 and 17, the emitted light generated from the light emitting layer 15 resonates between the two reflecting mirrors 11 and 17, and an anode (second reflecting mirror) 17 that is a semi-transmissive electrode. It is injected from the side.

The reflectance with respect to the emitted light of the anode 17 made of a transflective metal as the second reflecting mirror may be sufficient as long as a standing wave is formed in the resonator 19. For example, the reflectance is about 20 to 60%, and the reflectance of one of the first reflecting mirrors is a high reflectance of about 90% or more.
The first and second reflecting mirrors can be made of a metal such as Al, Ag, Mg, and Ca, an alloy containing them as a main component, or a dielectric multilayer film. When a reflecting mirror is made of metal, the reflectance can be controlled by its thickness.

（ここで、λは共鳴波長、θは反射鏡に垂直な光軸に対する傾き、ｎiは共振器内の層iの屈折率、ｄiは共振器内の層iの厚み、φ_１およびφ_２はそれぞれ第１および第２の反射鏡の反射による位相差、ｍはキャビティ次数である。） In the resonator 19, the resonance condition (Fabry-Perot resonance condition) for producing the microcavity effect is given by the following equation (1).

(Where λ is the resonance wavelength, θ is the tilt with respect to the optical axis perpendicular to the reflector, ni is the refractive index of the layer i in the resonator, di is the thickness of the layer i in the resonator, and φ ₁ and φ ₂ are (The phase difference due to the reflection of the first and second reflecting mirrors, respectively, m is the cavity order.)

As shown in the above formula (1), the resonance wavelength of the microcavity changes depending on the inclination from the optical axis A perpendicular to the reflector (reflection surface) of the resonator, and the resonance wavelength becomes shorter as the inclination θ increases. It shifts to the wavelength side. Here, each layer is designed to have a refractive index and a thickness satisfying the above formula so that a desired wavelength λ ₀ can be obtained in front of the element, that is, at a viewing angle of 0 (θ = 0). In addition, it is preferable from a viewpoint of luminous efficiency improvement to design so that the antinode part of the standing wave which arises in a resonator may correspond with a light emitting layer.

  The color filter 12 has an absorption peak at a resonator wavelength in a high viewing angle region having an inclination of more than 30 ° with respect to the optical axis A perpendicular to the reflecting mirrors 11 and 17, and resonance in the high viewing angle region. The device wavelength is absorbed relatively larger than the resonance wavelength in the low viewing angle region where the inclination from the optical axis A is 30 ° or less. The color filter 12 is formed by dispersing fine particles 12a that absorb a predetermined wavelength in a binder. As the fine particles 12a, various dyes, quantum dots, and the like can be used. As the binder, organic substances, resins, glass and the like can be used.

As is clear from the above equation (1), the resonance wavelength changes depending on the inclination from the optical axis A (that is, the viewing angle). That is, a spectrum having a wavelength λ ₀ as the center wavelength is observed in front of the element, but a spectrum having a center wavelength shorter than the wavelength λ ₀ is observed on the high viewing angle side. The chromaticity is greatly different from the chromaticity at the front.
On the other hand, the resonance strength of the microcavity is quantified by a value called finesse, and the greater the finesse, the greater the resonance effect. The finesse increases as the reflectivity of the reflector increases and as the absorption and scattering loss within the resonator decreases.

  In this embodiment, since the color filter 12 is provided and the resonance wavelength at a viewing angle higher than 30 ° can be greatly absorbed, the change in the resonance finesse at the front is suppressed, and the luminance and chromaticity at the front are maintained. As it is, the finesse at a high viewing angle is lowered, the resonance condition is weakened, and the change in emission spectrum (change in chromaticity) can be reduced.

FIG. 2 shows an example of an ideal refractive index of the color filter 12. In FIG. 2, the left axis shows the real part n of the refractive index, and the right axis shows the imaginary part κ of the refractive index. In the figure, the imaginary part of the refractive index indicated by a broken line is a parameter representing the absorption of the color filter. That is, the example shown in FIG. 2 is a filter that absorbs wavelengths of 510 nm or less and transmits only wavelengths exceeding 510 nm. It is difficult to produce an actual color filter that exhibits ideal characteristics as shown in FIG. Actually, it is sufficient that the absorptance with respect to the center wavelength at a high viewing angle of 30 ° to 80 ° is higher than the absorptance with respect to the center wavelength at a viewing angle of less than 30 °. More specifically, the ratio of the absorptance α ₂ with respect to the central wavelength at a viewing angle of 30 ° to the absorptivity α _{1 with} respect to the central wavelength at a viewing angle of 0 ° may be larger than 1, but preferably 5 or more. is there.

  For example, an element including a resonator having a resonance wavelength at the front = 525 nm, a resonance wavelength = 510 nm at a viewing angle of 30 °, and a resonance wavelength = 495 nm at a viewing angle of 60 ° is less than 510 nm as shown in FIG. Color filters that can absorb wavelengths are preferred. Such a color filter can be produced by dispersing CdSe (cadmium selenide) fine particles having an appropriate size (for example, a particle size of 3 nm or less) in a binder.

In the EL element 1 of the above embodiment, a first reflecting mirror 11 is formed on a substrate 10 by vapor deposition, a color filter 12 is formed on the reflecting mirror 11, a cathode 13 made of a transparent material such as ITO, an electron transport layer. 14, the light emitting layer 15, the hole transport layer 16, and the anode 17 can be formed by sequentially vapor deposition.
In the above embodiment, each layer such as the cathode 13, the electron transport layer 14, the light emitting layer 15, the hole transport layer 16, and the anode 17 can be appropriately selected from various materials known as layers having respective functions. is there. Furthermore, layers such as an electron injection layer, a hole injection layer, a hole block layer, an electron block layer, and a protective layer may be provided.

<EL Element of Second Embodiment>
FIG. 3 is a diagram schematically showing the structure of the electroluminescent element 2 according to the second embodiment of the present invention. The EL element 2 of the present embodiment is also an organic EL element in which each layer is composed of an organic layer.

The organic EL device 2 of the present embodiment includes a transparent substrate 20 made of glass or the like, an anode 21 made of a translucent metal, a hole injection layer 23 containing fine particles 22, a hole transport layer 24, a light emitting layer 25, an electron. The transport layer 26, the electron injection layer 27, and the cathode 28 are laminated in this order.
In the present embodiment, the anode 21 and the cathode 28 serve as two opposing reflecting mirrors to form a resonator 29, and an electric field is applied between the electrodes 21, 28, so that the light emitting layer 25 The generated emitted light resonates between both electrodes (reflecting mirrors) 21 and 28 and is emitted from the anode 21 side which is a semi-transmissive electrode.

  The reflectivity of each reflector, the refractive index of each layer based on the resonance conditions of the resonator, the layer thickness, and the like are the same as in the first embodiment. On the other hand, it is different from the first embodiment in that the fine particle 22 is provided in the hole injection layer 23 instead of the color filter.

The fine particles 22 have scattering and / or absorption peaks at the resonator wavelength in a high angle region having an inclination of more than 30 ° with respect to the optical axis A perpendicular to the reflecting mirrors 21 and 28. When the fine particles 22 cause only scattering in visible light, the peak of the scattering spectrum may be at the resonator wavelength in the high viewing angle region, and when only absorption occurs, the peak of the absorption spectrum has a high field of view. It only needs to be at the resonator wavelength in the corner region. When scattering and absorption occur, the peak of the disappearance spectrum indicated by the sum of the scattering spectrum and the absorption spectrum may be at the resonator wavelength in the high viewing angle region.
The fine particles 22 are metal fine particles made of Au, Ag, Al, Pt, Cu and alloys containing them as main components, or dielectric fine particles made of a high refractive index dielectric such as TiO ₂ , SiO ₂ , ZnSe. . Here, high refraction means that the refractive index is higher than that of the binder in which the fine particles are dispersed.
In the case where the fine particles 22 are metal fine particles, a configuration in which the fine particles are arranged close to the light emitting layer to the extent that light emission is enhanced by plasmon resonance generated on the surface of the fine particles by the emitted light (Japanese Patent Application No. 2009-082790; (Unpublished at the time of filing) is excluded in the present invention. Here, the proximity means that the shortest distance between the fine particles and the light emitting layer is approximately within 30 nm.

  For example, metal fine particles generally exhibit scattering and absorption with respect to wavelengths in the visible light region, and can have an action of suppressing resonance of the resonator wavelength in a high viewing angle region of 30 ° to 80 °. The fine particles exhibiting scattering and absorption need to be examined using an extinction spectrum represented by the sum of the scattering spectrum and the absorption spectrum, and the peak of the extinction spectrum is 30 with respect to the optical axis A as described above. It suffices if the resonator wavelength is in a high angle region having an inclination of more than °.

FIG. 4 shows a simulation result of the disappearance spectrum of Ag fine particles having a particle diameter (diameter) of 30 nm in 2-TNATA-F4-TCNQ used as the hole injection layer.
For example, in an EL device having an element structure in which the front resonance wavelength λ ₀ = 525 nm and the resonance wavelength λ ₃₀ = 510 nm at a viewing angle of 30 °, the viewing angle is obtained by providing the fine particles having the disappearance spectrum shown in FIG. Resonance at a viewing angle higher than 30 ° can be suppressed, and the same effect as when the color filter of the first embodiment is provided can be obtained.

  The scattering peak wavelength, absorption peak wavelength, disappearance peak wavelength, and the like are adjusted by adjusting the material of the fine particles 22, the particle size of the fine particles (here, defined by the maximum particle length), the fine particle shape, and the like. Can do. In the case of metal fine particles, the scattering peak wavelength can be shifted to the longer wavelength side by increasing the particle diameter. In addition, when rod-shaped fine metal particles are used, plasmon resonance is applied to the short wavelength side of the electric field oscillating in the direction parallel to the minor axis, and to the long wavelength side of the electric field oscillating in the direction parallel to the major axis. The wavelength can be shifted. In the case of dielectric fine particles, the resonance wavelength of scattering can be adjusted in the same manner as metal fine particles.

  When the fine particles are scatterers, the front luminance can be further increased by the light extraction effect due to scattering. Scattering occurs only for resonant wavelengths at angles of 30 ° and above, and the light emitted in the front is unaffected. Therefore, a part of the light radiated at an angle of 30 ° or more is scattered and re-radiated to the front, so that the front luminance is increased.

An example of a method for manufacturing the EL element 2 of this embodiment will be briefly described.
The cathode 21 is formed on the substrate 20 by vapor deposition, a part of the hole injection layer 23 is vapor-deposited, and the metal constituting the metal fine particles 22 is vapor deposited extremely thin (for example, about 5 nm). It is known that metal is deposited very thin to form fine particles. Thereafter, a hole injection layer 23 is further formed by evaporation, and a hole transport layer 24, a light emitting layer 25, an electron transport layer 26, an electron injection layer 27, and a cathode 28 are sequentially formed by evaporation.
When high refractive index dielectric particles are used, the cathode 21 is formed on the substrate 20 by vapor deposition, and the fine particles dispersed in the hole injection layer 23 are dissolved in an organic solvent, and spin coating is performed. Thereafter, the organic solvent may be volatilized.

  In the above embodiment, each layer such as a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode is selected from various materials known as layers having respective functions. It can be selected as appropriate. Furthermore, layers such as a hole blocking layer, an electron blocking layer, and a protective layer may be provided.

  In each of the above embodiments, an organic EL element in which a plurality of layers including a light emitting layer is composed of an organic compound layer has been described. However, the EL element of the present invention is an inorganic element in which a plurality of layers including a light emitting layer are inorganic compound layers. In addition to EL elements, the present invention can also be suitably applied to light-emitting diodes and semiconductor lasers composed of a plurality of semiconductor layers.

<Simulation>
With respect to Example 1 and Comparative Example 1 of the configuration of the EL element 1 of the first embodiment provided with a color filter inside the resonator, simulation by the characteristic matrix method was performed to predict chromaticity.

Example 1
As Example 1, in the configuration of the EL element 1 shown in FIG. 1, an element having the following materials and thicknesses for the layers 11 to 17 was assumed.
The first reflecting mirror 11 is 100 nm thick Al, the color filter 12 is a 100 nm thick color filter having the characteristics shown in FIG. 2, the cathode 13 is 70 nm thick ITO (indium tin oxide), and the electron transport layer 14 is 30 nm thick. The organic layer and the light emitting layer 15 were made of 30 nm thick CBP-10% Ir (ppy) 3, the hole transport layer 16 was made of 35 nm thick organic layer, and the anode 17 was made of 20 nm thick Ag. The refractive index of any organic layer was assumed to be about 1.67. In this configuration, the resonance wavelength λ _{0 in the} direction of the optical axis A is 525 nm.

(Comparative Example 1)
As Comparative Example 1, an element that does not include an element that does not have a filter effect is assumed with the imaginary part of the refractive index of the color filter 12 set to 0 in the configuration of Example 1 described above.

表１に示すように、実施例１は比較例１に比べて高視野角（３０°、６０°）から観測した際の、視野角０°（正面）から観測した色度に対する変化が小さいことが確認できた。 Table 1 shows the results obtained by conducting the simulation by the characteristic matrix method for the above-described Example 1 and Comparative Example 1, and converting the spectra obtained when observed from different viewing angles into CIE chromaticity coordinates.

As shown in Table 1, Example 1 has a smaller change with respect to chromaticity observed from a viewing angle of 0 ° (front) when observed from a higher viewing angle (30 °, 60 °) than that of Comparative Example 1. Was confirmed.

<Experimental example>
Example 2 and Comparative Example 2 having the configuration of the EL element 2 of the second embodiment provided with fine particles inside the resonator were produced, and the following experiment was performed.
(Example 2)
A glass substrate was used as the transparent substrate 20, and vapor deposition was performed on the glass substrate in the following order to produce the organic EL device of Example 1.
First, 20 nm of Ag was deposited as an anode 21 on a glass substrate. Thereafter, 2-TNATA (4,4,4, -tris (2-naphthylphenylamino) triphenylamine) and F4-TCNQ were deposited on Ag at 100 nm so that F4-TCNQ was 0.3%. Next, Ag was vapor-deposited to 5 nm, and 2-TNATA-F4-TCNQ was vapor-deposited to 80 nm so that F4-TCNQ was 0.3%. Thereby, the hole injection layer 23 made of 2-TNATA-F4-TCNQ including the metal fine particles 22 made of Ag could be formed. Further, NPD (N, N′-dinaphthyl-N, N′-diphenyl- [1,1′-biphenyl]) is deposited to a thickness of 10 nm as the hole transport layer 24, and CBP-10% Ir is formed as the light emitting layer 25. (Ppy) 3 was deposited as 30 nm, electron transport layer 26 as Balq as 40 nm, electron injection layer 27 as LiF as 1 nm, cathode as 28 nm, and Al was sequentially deposited as 100 nm, and finally sealed with UV adhesive. The organic EL device of Example 2 was completed.

  In addition, when the Ag layer vapor-deposited 5 nm inserted between 2-TNATA-F4-TCNQ was observed with SEM (scanning electron microscope), it confirmed that the microparticles | fine-particles about 30 nm in diameter were formed. The result of simulating the disappearance spectrum of 30 nm Ag fine particles in such 2-TNATA-F4-TCNQ is as shown in FIG.

(Comparative Example 2)
As Comparative Example 2, an organic EL element having no Ag particles in the hole injection layer 23 in the configuration of Example 1 was prepared. In the manufacturing process of the above example, the hole injection layer 23 was prepared by omitting the step of depositing Ag 5 nm.

表２に示すように、実施例２は比較例２に比べて、特に高視野角６０°から観測した際の、視野角０°（正面）から観測した色度に対する変化が小さいことが確認できた。 For Example 2 and Comparative Example 2, EL spectra were measured from different viewing angles. The measurement was performed under the condition that a direct current was passed between the electrodes and the luminance was 1000 cd / m ² for each viewing angle. Table 2 shows the result of converting the obtained spectrum into CIE chromaticity coordinates.

As shown in Table 2, it can be confirmed that Example 2 has a smaller change with respect to chromaticity observed from a viewing angle of 0 ° (front) when compared to Comparative Example 2, particularly when observed from a high viewing angle of 60 °. It was.

DESCRIPTION OF SYMBOLS 1, 2 Electroluminescent element 10, 20 Substrate 11 Reflector 12 Color filter 12a Fine particle 13, 28 Cathode 14, 26 Electron transport layer 15, 25 Light-emitting layer 16, 24 Hole transport layer 17, 21 Anode 19, 29 Resonator 22 Fine particles 23 Hole injection layer 27 Electron injection layer

Claims (9)

An electroluminescent element comprising a light emitting region that emits light by applying an electric field between the electrodes, between a plurality of layers stacked between electrodes,
A resonator composed of two opposing reflecting mirrors arranged in parallel to the laminated surface of the plurality of layers so as to resonate the light emitted from the light emitting region;
Fine particles having scattering and / or absorption peaks with respect to the resonator wavelength in a high angle region having an inclination of more than 30 ° with respect to the optical axis perpendicular to the reflecting mirror are provided inside the resonator. An electroluminescent element characterized.   2. The electroluminescent device according to claim 1, wherein each of the plurality of layers includes at least an electron transport layer, a light emitting layer, and a hole transport layer, each formed of an organic layer.   3. The electroluminescent element according to claim 1, wherein at least one of the two opposing reflecting mirrors also serves as one of the electrodes.   The electroluminescent device according to claim 1, wherein the fine particles are metal fine particles.   5. The metal fine particles are made of at least one selected from the group consisting of Au, Ag, Al, Pt, Cu, and alloys containing these metals as main components. Electroluminescence element.   The electroluminescent device according to claim 1, wherein the fine particles are dielectric fine particles. The electroluminescent device according to claim 6, wherein the dielectric fine particles are made of at least one selected from the group consisting of TiO ₂ , SiO ₂ and ZnSe.   The electroluminescent device according to any one of claims 1 to 3, wherein the fine particles are dyes or quantum dots.   2. Each of the two opposing reflecting mirrors is made of at least one selected from the group consisting of Al, Ag, Mg, Ca, and an alloy containing these metals as main components. The electroluminescent element according to any one of 1 to 4.

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