WO2014104042A1 - Organic el element, and image display device and lighting device each of which is provided with same - Google Patents

Abstract

This organic EL element (10) is sequentially provided, on a substrate (11), with a positive electrode (first electrode) (12), an organic layer (13) which includes a light emitting layer that is formed of an organic EL material, and a negative electrode (metal layer, second electrode) (14). The positive electrode (12) is a transparent electrode that is formed of a transparent conductive material. The negative electrode (14) is formed of a conductive metal material and has a plurality of through hole portions (14A). This organic EL element (10) is configured such that light is mainly extracted from the positive electrode (12) side to the outside.

Description

ORGANIC EL ELEMENT AND IMAGE DISPLAY DEVICE AND LIGHTING DEVICE EQUIPPED

The present invention relates to an organic EL element, and an image display device and an illumination device including the organic EL element. This application claims priority based on Japanese Patent Application No. 2012-289021 filed in Japan on December 28, 2012, the contents of which are incorporated herein by reference.

Organic EL devices (organic electroluminescence devices) have features such as wide viewing angle, high-speed response, clear self-luminous display, etc., and they are next-generation lighting because they are thin, lightweight and have low power consumption. It is expected as a pillar of devices and image display devices.
Organic EL elements are classified into a bottom emission type in which light is extracted from the support substrate side and a top emission type in which light is extracted from the opposite side of the support substrate, depending on the direction in which the light generated in the organic light emitting layer is extracted. .

In a bottom emission type organic EL element, light incident on the transparent substrate out of the light emitted from the light emitting layer passes through the transparent substrate and is extracted outside the element. Of the light emitted from the light emitting layer, a transparent substrate, for example, a small incident angle (light ray and incident surface) of a critical angle or less at the interface between glass (refractive index: 1.52) and air (refractive index: 1.0). Light incident at an angle formed by a normal line is refracted at the interface and extracted outside the organic EL element. These lights can be referred to as external mode lights.
On the other hand, of the light emitted from the light emitting layer, the light incident on the interface between the transparent substrate and air at an incident angle larger than the critical angle is totally reflected at the interface and is not taken out of the device, and finally Can be absorbed by the material. This light can be referred to as substrate mode light, and the resulting loss is referred to as substrate loss.
Of the light emitted from the light emitting layer, an anode made of a transparent conductive oxide (for example, indium tin oxide (ITO (refractive index: 1.82)) and a transparent substrate (for example, glass (refractive index: 1.52)) Light incident on the interface between the high refractive index layer (incident side) and the low refractive index layer (exit side) that may exist between the light emitting layer and the anode at an incident angle greater than the critical angle The light is totally reflected and is not taken out of the organic EL element, but can be finally absorbed by the material.This light can be referred to as waveguide mode light, and the loss due to this is referred to as waveguide loss.
Of the light emitted from the light emitting layer, light incident on a metal surface such as a metal cathode is coupled with free electron vibration of the metal cathode, and the light captured on the surface of the metal cathode as surface plasmon polariton (SPP) It is not taken out of the organic EL element and can be finally absorbed by the material as heat. This light can be referred to as SPP mode light, and the loss due to this is referred to as plasmon loss.

The light extraction efficiency of the organic EL element (ratio of the light extracted outside the element with respect to the light emitted from the light emitting layer) is generally considered to be about 20%. That is, about 80% of the light emitted from the light emitting layer is lost, and it is a big problem to reduce these losses and improve the light extraction efficiency.
Here, it is known that the extraction of the substrate mode light can be dealt with by providing a light diffusion sheet or the like on the transparent substrate. It is known that waveguide mode light can be extracted by using a transparent substrate having a high refractive index (refractive index: 1.7 to 2.0).

Regarding light extraction of SPP mode light, a structure in which fine particles that generate plasmon resonance are arranged in the vicinity of or inside a light emitting layer in a structure in which a light emitting layer is provided between an anode and a cathode, and light emission enhancement by luminescence transition by plasmon is known. (Patent Document 1).
As a method for extracting the SPP mode light captured on the surface of the metal cathode, a configuration in which a periodic uneven structure of about 50 nm is formed on the surface of the metal cathode is also known (Patent Document 2).
As a method for preventing the surface of the metal cathode from being supplemented as SPP, a configuration in which the distance between the metal cathode and the light emitting portion is increased by increasing the thickness of the organic layer is also known (Non-Patent Document 1).

JP 2010-238775 A JP 2006-313667 A

Appl. Phys. Lett., 2010, 97, 253305

However, research and development has been started on a structure for suppressing SPP mode light and a structure for extracting SPP mode light, and the light extraction efficiency can be improved by suppressing SPP mode light in addition to the above-described conventional technology. It is desirable to provide a structure.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an organic EL element that can suppress SPP mode light and improve light extraction efficiency, and an image display device and an illumination device including the organic EL element. .

(1) An organic EL element in which an organic layer including a light emitting layer is sandwiched between a pair of electrodes facing each other, one electrode is a metal electrode, and the other electrode is a transparent electrode, mainly the transparent electrode An organic EL element having a configuration in which light is extracted from the side to the outside, and the metal electrode has a plurality of through holes or a plurality of non-through holes formed from the surface on the organic layer side.
(2) An organic EL element comprising a first electrode, an organic layer including a light emitting layer, and a metal layer in this order, wherein the first electrode is a transparent electrode made of a transparent conductive material, and the metal layer is a second electrode. The metal layer has a plurality of through-holes or a plurality of non-through holes formed from the surface on the organic layer side, and the first electrode side is a main light extraction side. EL element.
(3) The organic EL element according to (2), wherein the first electrode is an anode formed on a substrate, and the metal layer is a cathode.
(4) The organic EL element according to (2) or (3), wherein a minimum width of the through hole is 100 nm or more.
(5) Any one of (2) to (4), wherein a minimum width of the non-penetrating hole is 200 nm or more, and an interval between the non-penetrating holes adjacent to each other is 50 nm or more. The organic EL element as described in.
(6) The organic EL element according to (5), wherein the maximum width of the hole not penetrating is not less than the interval.
(7) The organic EL element according to any one of (2) to (6), wherein the thickness of the metal layer is in the range of 50 to 1000 nm.
(8) The organic EL device according to any one of (2) to (7), wherein a protective layer is provided between the organic layer and the metal layer.
(9) The organic EL element according to any one of (2) to (7), wherein the metal layer is in contact with the organic layer.
(10) A first dielectric layer having a refractive index lower than that of the organic layer and having a plurality of holes is provided between the first electrode and the metal layer, and the organic layer The organic EL element according to any one of (2) to (9), characterized in that covers at least the inner surface of the hole.

(11) The first electrode includes a plurality of first electrode holes, and a second dielectric layer having a refractive index lower than a refractive index of the first electrode and lower than a refractive index of the organic layer is provided as the first dielectric layer. The organic EL device according to any one of (2) to (10), wherein the organic EL device is provided inside an electrode hole.
(12) An organic EL element including a first electrode, an organic layer including a light emitting layer, a second electrode, an insulating layer, and a metal layer in this order, both of the first electrode and the second electrode being a transparent conductive material The metal layer has a plurality of through holes or a plurality of non-through holes formed from the surface on the organic layer side, and the first electrode side is a main light extraction side. A characteristic organic EL element.
(13) An image display device comprising the organic EL element according to any one of (1) to (12).
(14) An illuminating device comprising the organic EL element according to any one of (1) to (12).

According to the present invention, it is possible to provide an organic EL element that suppresses SPP mode light and improves light extraction efficiency, and an image display device and an illumination device including the organic EL element.

It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 1st Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the image display apparatus provided with the organic EL element which concerns on this invention. It is a cross-sectional schematic diagram which shows an example of the illuminating device provided with the organic EL element which concerns on this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 3rd Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 4th Embodiment of this invention. It is a schematic perspective view which shows arrangement | positioning of the through-hole part of the organic EL element which concerns on 4th Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 5th Embodiment of this invention. It is a schematic perspective view which shows arrangement | positioning of the through-hole part of the organic EL element which concerns on 5th Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 6th Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the organic EL element which concerns on 7th Embodiment of this invention. It is a schematic perspective view which shows arrangement | positioning of the through-hole part of the organic EL element which concerns on 7th Embodiment of this invention. 14 is a graph showing simulation results of in-light emission positions in an example of the organic EL device according to the first embodiment of the present invention, and FIGS. 13A to 13C are vertical propagation light, parallel propagation light, and random propagation, respectively. The wavelength dependence of the light extraction efficiency (eta) to the glass substrate of light is shown. 15 is a graph showing simulation results of out emission positions in an example of the organic EL device according to the first embodiment of the present invention, and FIGS. 14A to 14C are vertical propagation light, parallel propagation light, and random propagation, respectively. The wavelength dependence of the light extraction efficiency (eta) to the glass substrate of light is shown. The model structure used for the simulation of the organic EL element which concerns on 3rd Embodiment of this invention is shown, FIG.15 (a) is a cross-sectional schematic diagram which shows the example, FIG.15 (b) is a cross section which shows another example. It is a schematic diagram. FIG. 16 is a graph showing simulation results of the in-light emission position of the organic EL element according to the model structure shown in FIG. 15, and FIGS. 16 (a) to 16 (c) are glasses of vertical propagation light, parallel propagation light, and random propagation light, respectively. The wavelength dependence of the light extraction efficiency η up to the substrate is shown. It is a graph which shows the simulation result of in light emission position in an example of the organic EL element concerning a 4th embodiment of the present invention, and Drawing 17 (a) and (b) is a glass substrate of perpendicular propagation light and parallel propagation light, respectively. The wavelength dependence of the light extraction efficiency η is shown. It is a graph which shows the simulation result of the out light emission position in an example of the organic EL element which concerns on 4th Embodiment of this invention, (a), (b) is a glass substrate of perpendicular direction propagation light and parallel direction propagation light, respectively. The wavelength dependence of the light extraction efficiency η is shown. It is a graph which shows the simulation result of the in light emission position in an example of the organic EL element concerning a 5th embodiment of the present invention, and Drawing 19 (a) and (b) is a glass substrate of perpendicular propagation light and parallel propagation light, respectively. The wavelength dependence of the light extraction efficiency η is shown. It is a graph which shows the simulation result of the out light emission position in an example of the organic EL element concerning a 5th embodiment of the present invention, and Drawing 20 (a) and (b) is a glass substrate of perpendicular direction propagation light and parallel direction propagation light, respectively. The wavelength dependence of the light extraction efficiency η is shown. FIG. 21 is a graph showing simulation results of an in emission position and an out emission position in an example of an organic EL element according to the sixth embodiment of the present invention, and FIGS. 21A to 21C are vertical direction propagation light and parallel direction propagation light, respectively. The wavelength dependence of light extraction efficiency (eta) to the glass substrate of light and random propagation light is shown. FIG. 22A and FIG. 22C are graphs showing simulation results of in light emission positions and out light emission positions in an example of the organic EL device according to the seventh embodiment of the present invention, and FIGS. 22A to 22C are respectively vertical propagation light and parallel propagation light. The wavelength dependence of light extraction efficiency (eta) to the glass substrate of light and random propagation light is shown. It is a scanning electron microscope (SEM) photograph which shows the state which formed the through-hole part in the cathode in the Example of this invention, FIG.23 (a) is a 50,000 times enlarged photograph of a 1st example, FIG.23 (b) Is a 3000 times enlarged photograph of the first example, FIG. 23C is a 50,000 times enlarged photograph of the second example, and FIG. 23D is a 3000 times enlarged photograph of the second example. The model structure used for the simulation of the organic EL element which concerns on 1st Embodiment of this invention is shown, Fig.24 (a) is a cross-sectional schematic diagram of the model structure, FIG.24 (b) expanded the through-hole part. It is a perspective view. It is a model structure in the case of simulating in order to grasp the influence of the light source position on the through hole. FIG. 25A is a graph showing a simulation result of the organic EL element according to the model structure shown in FIG. 24. FIG. 25A shows the wavelength dependence of the light extraction efficiency η of the parallel propagation light to the glass substrate, and FIG. ) Shows the wavelength dependence of the light extraction efficiency η of random propagation light up to the glass substrate. It is a cross-sectional schematic diagram which shows the other model structure used for the simulation of the organic EL element which concerns on 6th Embodiment of this invention. 27 is a graph showing simulation results of the in-light emission position of the organic EL element according to the model structure shown in FIG. 26, and FIGS. 27A to 27C are glasses for vertically propagating light, parallel propagating light, and random propagating light, respectively. The wavelength dependence of the light extraction efficiency η up to the substrate is shown. It is a cross-sectional schematic diagram which shows the other model structure used for the simulation of the organic EL element which concerns on 6th Embodiment of this invention. 29 is a graph showing simulation results of the in-light emission position of the organic EL element according to the model structure shown in FIG. 28, and FIGS. 29 (a) to 29 (c) are glasses for vertically propagated light, parallel propagated light, and randomly propagated light, respectively. The wavelength dependence of the light extraction efficiency η up to the substrate is shown.

Hereinafter, the structure of an organic EL element to which the present invention is applied, an image display apparatus and an illumination apparatus including the organic EL element will be described with reference to the drawings. In the drawings used in the following description, in order to make the features easier to understand, the portions that become the features may be shown in an enlarged manner for convenience, and the dimensional ratios and the like of the respective components are not always the same as the actual ones. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited to these, and can be appropriately modified and implemented without changing the gist thereof.
The organic EL element exemplified below as an embodiment has a bottom emission type configuration including a substrate on the first electrode side as viewed from the organic layer, but a top emission type configuration including a substrate on the metal layer side as viewed from the organic layer. It is good also as a structure. Furthermore, in the following embodiments, the first electrode is configured as an anode, but the first electrode may be configured as a cathode.

“First Embodiment” “Organic EL Device”
The organic EL device according to the first embodiment of the present invention includes a first electrode, an organic layer including a light emitting layer made of an organic EL material, and a metal layer in this order on a substrate. The first electrode is a transparent electrode made of a transparent conductive material, and the metal layer is a second electrode. The metal layer has a plurality of through-hole portions, and the first electrode side is the main light extraction side.

FIG. 1 is a schematic cross-sectional view for explaining an example of the organic EL element according to the first embodiment of the present invention.
An organic EL element 10 shown in FIG. 1 includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode (metal layer, second electrode) 14 in this order on a substrate 11. To do. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 14 is a metal electrode made of a conductive metal material. The cathode 14 is a bottom emission type organic EL element 10 having a plurality of through-hole portions 14A and configured to extract light mainly from the anode 12 side.

The organic EL element 10 of the present embodiment is a bottom emission type organic EL element that extracts light emitted from the light emitting layer mainly from the substrate 11 side. Therefore, the substrate 11 is a light-transmitting substrate and usually needs to be transparent to visible light. Here, “transparent to visible light” means that it is only necessary to transmit visible light having a wavelength emitted from the light emitting layer, and does not need to be transparent over the entire visible light region. The transmittance in visible light of 400 to 700 nm is preferably 50% or more. More preferably, the transmittance is 70% or more.

Specific examples of the substrate 11 include a glass plate and a polymer plate. Examples of the glass plate material include soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate material include polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polymethyl naphthalate, polyethylene naphthalate, polyether sulfide, polysulfone and the like.
When the emitted light is not visible light, it is necessary to be transparent at least with respect to the emission wavelength region as in the case of visible light. The transmittance is preferably 50% or more and more preferably 70% or more with respect to the wavelength at which the emission spectrum has the maximum intensity.

When the configuration of the organic EL element according to this embodiment is a top emission type, an opaque material can be used in addition to the same material as described above. Specifically, for example, Cu, Ag, Au, Pt, W, Ti, Ta, Nb, Al alone, an alloy containing these elements, or a metal material such as stainless steel, Si, SiC, AlN, GaN, Nonmetallic materials such as GaAs and sapphire, and other substrate materials usually used in top emission type organic EL elements can be used. In order to release heat generated by light emission of the element, a material having high thermal conductivity is preferably used for the substrate.

The thickness of the substrate 11 is appropriately set depending on the required mechanical strength, and is not limited, but is preferably 0.01 to 10 mm, more preferably 0.05 to 2 mm.

The cathode 14 is an electrode for injecting electrons into the light emitting layer, and it is preferable to use a material made of a metal, an alloy, a conductive compound, or a mixture thereof having a small work function. It is preferable to use a material having a work function of 1.9 eV or more and 5 eV or less so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level of the organic layer 13 in contact with the cathode 14 does not become excessive.
Specifically, for example, materials such as single metals such as Au, Ag, Cu, Zn, and Al, alloys thereof, MgAg alloys, alloys of Al and alkali (earth) metals such as AlLi and AlCa, etc. can do.

The thickness of the cathode 14 is not particularly limited, but is, for example, 30 to 1000 nm, and preferably 100 to 1000 nm. If the thickness of the cathode 14 is less than 30 nm, the sheet resistance increases and the driving voltage rises. If the thickness of the cathode 14 is thicker than 1000 nm, heat and radiation damage during film formation, and mechanical damage due to film stress may accumulate in the electrode and the organic layer.

The cathode 14 includes a plurality of through-hole portions 14 </ b> A, and the bottom of each through-hole portion 14 </ b> A is closed with the organic layer 13. In the present embodiment, the organic layer 13 has a structure that does not enter the through-hole portion 14A. As another form, the inside of the through-hole portion may be filled with a gas, or may be filled with an organic material (the same material as the organic layer 13 or a different material may be used). Further, it may be filled with an insulating material or a metal oxide.
When the refractive index of the medium inside the through-hole portion 14A is lower than that of the organic layer 13, it is easy to totally reflect at the interface between the organic layer 13 and the medium having a low refractive index. Can be improved. The through-hole portion 14A penetrates the entire cathode 14 in the thickness direction.

Typical shapes of the through-hole portion 14A include a columnar shape, an elliptical column shape, a polygonal column shape, a truncated cone shape, a truncated pyramid shape, a hemispherical shape, and a shape in which these are combined. When the shape has a taper, the cross section may be either a straight shape or a curved shape. That is, neither the cross-sectional shape nor the planar shape of the through-hole portion 14A is limited.
The size of the through hole portion 14A can be defined by the minimum width and the maximum width of the through hole portion 14A in plan view. The minimum width refers to the diameter of the maximum circle included in the through hole portion 14A. The maximum width means the diameter of the minimum circle that includes the through-hole portion 14A. When the through-hole portion 14A is a perfect circle, the minimum width and the maximum width match. The size of the through-hole portion 14A is not particularly limited as long as the through-hole is formed. In view of the ease of forming the through hole portion 14A, the minimum width of the through hole portion 14A is preferably 100 nm or more, for example, and the interval between the through hole portions can be set to 50 nm or more, for example. The interval refers to the shortest distance not including the through hole portion between adjacent through hole portions 14A.

The maximum width of the through-hole portion 14A is preferably as large as possible within a range not overlapping with the other through-hole portions 14A. The arrangement of the plurality of through-hole portions 14A may be periodic or aperiodic. In order to extract the SPP mode light, the occupied area ratio (ratio of the bottom area of the through-hole portion 14A to the light-emitting region (a region combining an in-light-emitting region and an out-light-emitting region described later) in plan view of the through-hole portion 14A is 20 to 90% is preferable. The bottom area of the through-hole portion 14A in plan view refers to the area of the through-hole portion 14A at the interface between the cathode 14 and the organic layer 13.

The anode 12 is an electrode for applying a voltage between the anode 14 and injecting holes from the anode 12 into the light emitting layer. It is preferable to use a material made of a metal, an alloy, a conductive compound, or a mixture thereof having a high work function. It is preferable to use a material having a work function of 4 eV or more and 6 eV or less so that the difference from the HOMO (Highest Occupied Molecular Orbital) level of the organic layer 13 in contact with the anode 12 does not become excessive.
The material of the anode 12 is not particularly limited as long as it is a translucent and conductive material, and a known material can be used. For example, conductive high conductivity doped with transparent inorganic oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, zinc oxide, conductive polymers such as PEDOT: PSS, polyaniline, and arbitrary acceptors. Examples thereof include transparent carbon materials such as molecules, carbon nanotubes, and graphene. The anode 12 can be formed on the substrate 11 by, for example, a sputtering method, a vacuum deposition method, a coating method, an ion plating method, or the like.
The thickness of the anode 12 is not limited, but is, for example, 10 to 2000 nm, and preferably 50 to 1000 nm. If the thickness of the anode 12 is greater than 2000 nm, the flatness of the organic layer 13 cannot be maintained, and the transmittance of the anode 12 decreases. If the thickness of the anode 12 is less than 10 nm, the film thickness non-uniformity may increase, or the sheet resistance may increase and the in-plane luminance may become non-uniform.

As a material of the light emitting layer constituting the organic layer 13, any material known as a material for an organic EL element can be used.
The organic layer 13 may include a light emitting layer made of an organic EL material, a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, or the like individually or in combination.
The hole injection layer is a layer that assists hole injection from the anode 12 to the organic layer 13, and its ionization energy is usually as low as 5.5 eV or less. As such a hole injection layer, a material that injects holes into the organic layer 13 with lower electric field strength is preferable. The material for forming the hole injection layer is not particularly limited as long as it can perform the above function, and any material can be selected and used from known materials. The hole transport layer is a layer that transports holes to the light emitting region and has a high hole mobility. The material for forming the hole transport layer is not particularly limited as long as it can perform the above functions, and any material can be selected and used from known materials.
The electron injection layer is a layer that assists electron injection from the cathode 14 to the organic layer 13. As such an electron injection layer, a material that injects electrons into the organic layer 13 with lower electric field strength is preferable. The material for forming the electron injection layer is not particularly limited as long as it can perform the above function, and any material can be selected and used from known materials. The electron transport layer is a layer that transports electrons to the light emitting region and has a high electron mobility. The material for forming the electron transport layer is not particularly limited as long as it can perform the above functions, and any material can be selected and used from known materials.

The organic layer 13 can be formed by a known method. For example, the organic layer 13 may be formed by a dry process such as an evaporation method or a transfer method, or a spin coating method, a spray coating method, a die coating method, a gravure printing method, or the like. Alternatively, the film may be formed by a wet process.
The thickness of the organic layer 13 is not limited, but is, for example, 50 to 2000 nm, and preferably 100 to 1000 nm. When the thickness of the organic layer 13 is less than 50 nm, quenching other than the SPP coupling by the cathode metal occurs, such as a decrease in internal quantum efficiency due to a punch-through current and a lossy surface wave mode coupling. When the thickness of the organic layer 13 is greater than 2000 nm, the drive voltage increases.

When the organic EL element 10 of the present embodiment is energized so as to apply a potential difference between the anode 12 and the cathode 14, the light emitting layer inside the organic layer 13 emits light, so that the main is via the anode 12 made of a transparent conductive material. In addition, light can be extracted from the substrate 11 side. In the organic EL element 10 of the first embodiment, the amount of light extracted from the anode 12 side, which is a transparent electrode, is smaller, but the light passing through the through-hole portion 14A of the cathode 14 can also be extracted from the cathode 14 side. .
The organic layer 13 may emit light at any position in the layered region sandwiched between the anode 12 and the cathode 14, and can be described by dividing into in emission and out emission as follows. In the light emission form inside the organic layer 13, the light emission form in a region where the organic layer 13 is not seen from the plan view when the organic layer 13 is present, that is, a region overlapping the through hole portion 14 </ b> A of the cathode 14 is referred to as in light emission in this specification. A light emission form in a region where the cathode 14 exists, that is, a region overlapping with a region where the through-hole portion 14A is not formed is referred to as out light emission in this specification.

When an organic material usually used in an organic EL element is used for the organic layer 13, the organic layer 13 is generally strong on the shortest path connecting layers (anode 12 and cathode 14) made of a highly conductive material. Emits light. In the present embodiment, a region that emits light strongly is a lower region of the cathode 14 where the distance between the anode 12 and the cathode 14 is short (out emission). However, by forming a buffer layer having high conductivity between the cathode 14 having the through-hole portion 14A and the organic layer 13 in contact with the organic layer 13, a conventional element having no through-hole portion 14A in the cathode 14 is formed. Similarly, the entire light emitting layer can emit light of the same degree regardless of the arrangement of the through holes 14A of the cathode 14.
By forming an insulating layer only in the out light emitting region between the cathode 12 and the organic layer 13, and further forming the cathode 12, the conductive medium is formed so as to fill a part of the through-hole portion 14A. Thus, an organic EL element that emits light strongly by in-light emission can be produced.

Here, the highly conductive buffer layer is not limited as long as no plasmon is generated. When the cathode 14 has the through-hole part 14A, the buffer layer is formed using a material used as an electron injection layer, for example. This layer may have a function of increasing the electron injection efficiency by lowering the electron injection barrier from the cathode to the organic layer. Specific materials include, for example, metals such as alkali metals (Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba), and rare earth metals (Pr, Sm, Eu, Yb). Materials selected from fluorides, chlorides, oxides and mixtures of two or more can be used. Furthermore, a mixture of an organic compound having a high electron affinity such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (basocuproin (BCP)) and a material having a high electron donating property such as Cs is also preferably used. . The thickness of the buffer layer is preferably from 0.1 to 50 nm, more preferably from 0.1 to 20 nm, and even more preferably from 0.5 to 10 nm.

In the embodiment shown in FIG. 1, it is the cathode 14 that has the through-hole portion 14A. However, in the present invention, the electrode having the through-hole portion may be used as the anode. In such a configuration, the highly conductive buffer layer is formed by using, for example, a material used as a hole injection layer. Specifically, for example, conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, polythiophene, polyparaphenylene vinylene; organic compounds such as arylamine and phthalocyanine; vanadium oxide, zinc oxide, molybdenum oxide, ruthenium oxide, oxidation An oxide such as titanium may be used. These materials can improve conductivity by injecting carriers that can be freely doped and doped.
As the material for the hole injection layer, one kind may be used alone, or two or more kinds may be mixed and used like a mixture doped with a dopant. Further, the buffer layer may be formed by stacking different hole injection layer materials. Examples of using dopants include a mixture of poly (3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT: PSS), polyaniline (PANI) and polystyrene sulfonic acid (PSS). A mixture (PANI: PSS) etc. are mentioned. A material which is used as an anode and which is not a metal may be used.

Further, regardless of whether the electrode having the through-hole portion 14A is an anode or a cathode, indium tin oxide (ITO: Indium Tin Oxide: In ₂ O ₃ ), which is a metal oxide having conductivity, is used as the material having good conductivity. -SnO ₂ ), indium zinc oxide (IZO: Indium Zinc Oxide: In ₂ O ₃ —ZnO), indium molybdenum oxide (IMO: Indium Molybdenum), zinc oxide (ZnO), aluminum zinc oxide (AZO: Aluminum Zinc Oxide: Al ₂ O ₃ —ZnO), gallium zinc oxide (GZO: Gallium Zinc Oxide: Ga ₂ O ₃ —ZnO), molybdenum oxide (MoO ₃ ), fluorine-doped tin oxide (FTO: Fluorine Tin Oxide: F / SnO ₂ ) A material containing at least one oxide of niobium-doped titanium oxide (NTO: Niobium Titanium Oxide: Nb / TiO ₂ ) and antimony-doped tin oxide (ATO: Antimony Tin Oxide Sb / SnO ₂ ) may be used. it can.

As shown in FIG. 1, the light emission position in in light emission has a larger distance from the cathode 14 than the light emission position in out light emission, and is in a region corresponding to the through-hole portion 14A, so that the amount of energy transfer to the SPP mode is small. That is, the generation of SPP mode light is small and plasmon loss due to this is reduced. In order to reduce the generation of this SPP mode light, it is preferable that the distance between the light emitting position and the cathode 14 be 100 nm or more, and the light extraction efficiency can be improved. Therefore, the size of the inner diameter of the through hole portion 14A is important, and the minimum width of the through hole portion 14A can be set to 100 nm or more, for example, in the range of 100 to 4000 nm, and preferably in the range of 200 to 2000 nm. be able to. As described above, the minimum width of the through-hole portion 14A can be defined by the diameter of the maximum circle included in the through-hole portion 14A in plan view.

In the structure of the organic EL light emitting device 10 shown in FIG. 1, the inside of the through-hole portion 14A is a void, and is filled with a gas such as nitrogen, for example, and the material of the organic layer 13 is not formed inside the through-hole portion 14A. On the other hand, it may be configured to be filled with the organic layer 13 or other materials. When an organic material is present inside the through hole portion 14A extending from the organic layer, the emitted light propagates through the organic layer 13 and enters the organic material in the through hole portion 14A. The same applies to the case where a material having a refractive index higher than that of the light emitting layer is present in the through hole portion 14A. On the other hand, if a material having a refractive index lower than that of the organic layer 13 is present in the through-hole portion 14A, light incident on the interface between the organic layer 13 and the low refractive index material at a critical angle or more is totally reflected. Therefore, when the through hole 14A is filled with a material having a lower refractive index than the organic layer 13, the propagation distance of the guided light propagating through the organic layer 13 is shortened, so that the light loss is reduced and the light extraction efficiency is improved. Since it improves, it is preferable. Since a gas such as nitrogen has a lower refractive index than the organic material constituting the organic layer, this corresponds to the case of this low refractive index material, compared to the case where the inside of the through-hole portion 14A is filled with an organic material or a high refractive index material. Also, the light extraction efficiency is improved.

Furthermore, the flat portion having a period of 100 nm or more is intermittent in the interface in contact with the organic layer 13 in the through-hole portion 14A of the cathode 14. Therefore, the mode light generated at the interface is radiated into the organic layer 13 where the interface is interrupted (converted into an optical mode propagating in the organic layer). For this reason, the light extraction efficiency is improved by providing the cathode 14 with through-hole portions 14A having a minimum width of 100 nm or more and an interval of 50 nm or more.
As described above, since the cathode 14 has the through-hole portion 14A, there is an advantage that the light that has become the SPP mode light can be taken out, and the portion of the organic layer 13 corresponding to the through-hole portion 14A has a cathode (metal). The layer) 14 is an area that does not exist in the vicinity and does not become SPP mode light, so that the light extraction efficiency is improved.
Since the cathode 14 has the through-hole portion 14A, light generated in the organic layer 13 can be extracted outside the cathode 14 through the through-hole portion 14A. However, since the organic layer 13 is covered with a cathode (metal layer) 14 made of a conductive metal material in a region other than the through-hole portion 14A, the light extracted through the through-hole portion 14A is emitted in light or out. Regardless, less light is extracted from the anode 12 side. The same applies to the case where the electrode having the through-hole portion is used as the anode.

In the structure of the present embodiment, the substrate 11 is provided on the side opposite to the organic layer 13 of the anode 12 that is a transparent electrode, and is a bottom emission type in which light is extracted from the substrate 11 side that is the anode 12 side. A top emission type in which the stacking relationship of the cathode 14 is reversed may be employed. Specifically, a structure in which the cathode 14 is formed on the substrate and the organic layer 13 and the anode 12 are formed thereon may be employed. In this case, the cathode 14 is made of a metal material, and a through-hole portion 14A is formed in the cathode 14. In the case of such a top emission type, light emitted from the organic layer 13 is extracted mainly from the surface opposite to the substrate through the anode 12. In the example shown in FIG. 1, the transparent electrode is the anode 12 and the metal electrode having the through-hole portion 14A is the cathode 14, but the former may be a cathode and the latter may be the anode. In the case where such an anode / cathode is inverted, light in the organic layer is extracted to the outside through a cathode that is mainly transparent.
As a method of forming the through-hole portion 14A in the cathode 14, a method of forming a hole by using a mask or the like at the time of film formation by vapor deposition or the like, and a cathode in which a through-hole portion is separately formed are bonded by a transfer method or the like as will be described later. There are methods. After forming a layer having a certain film thickness by vapor deposition or the like, the through-hole portion can also be formed by ablation or the like using a laser or the like.

"Image display device"
Next, an image display apparatus including the organic EL element 10 of the first embodiment will be described.
FIG. 2 is a diagram illustrating an example of an image display device including the organic EL element 10.
An image display device 100 shown in FIG. 2 is a so-called passive matrix type image display device. In addition to the organic EL element 10, an anode wiring 104, an anode auxiliary wiring 106, a cathode wiring 108, an insulating film 110, a cathode partition 112, A sealing plate 116 and a sealing material 118 are provided.

In the present embodiment, a plurality of anode wirings 104 are formed on the substrate 11 of the organic EL element 10. The anode wirings 104 are arranged in parallel at a constant interval. The anode wiring 104 is made of a transparent conductive film, and is made of, for example, ITO (Indium Tin Oxide). The thickness of the anode wiring 104 can be set to 100 to 150 nm, for example. An anode auxiliary wiring 106 is formed on the end of each anode wiring 104. The anode auxiliary wiring 106 is electrically connected to the anode wiring 104. With this configuration, the anode auxiliary wiring 106 functions as a terminal for connecting to the external wiring on the end portion side of the substrate 1, and the anode wiring is connected from the driving circuit (not shown) provided outside through the anode auxiliary wiring 106. A current can be supplied to 104. The anode auxiliary wiring 106 is made of a metal film having a thickness of 500 to 600 nm, for example.

A plurality of cathode wirings 108 are provided on the organic EL element 10. The plurality of cathode wirings 108 are arranged so as to be parallel to each other and orthogonal to the anode wiring 104. The cathode wiring 108 can be made of Al or an Al alloy. The thickness of the cathode wiring 108 is, for example, 100 to 150 nm. A cathode auxiliary wiring (not shown) is provided at the end of the cathode wiring 108, similarly to the anode auxiliary wiring 106 for the anode wiring 104, and is electrically connected to the cathode wiring 108. Therefore, a current can flow between the cathode wiring 108 and the cathode auxiliary wiring.

Further, an insulating film 110 is formed on the substrate 11 so as to cover the anode wiring 104. A rectangular opening 120 is provided in the insulating film 110 so as to expose a part of the anode wiring 104. The plurality of openings 120 are arranged in a matrix on the anode wiring 104.
In these openings 120, the organic EL element 10 is provided between the anode wiring 104 and the cathode wiring 108. That is, each opening 120 becomes a pixel. Accordingly, a display area is formed corresponding to the opening 120. Here, the film thickness of the insulating film 110 can be, for example, 100 to 200 nm, and the size of the opening 120 can be, for example, 100 μm × 100 μm.

The organic EL element 10 is located between the anode wiring 104 and the cathode wiring 108 in the opening 120. In this case, the anode 12 of the organic EL element 10 is connected to the anode wiring 104 and the cathode 14 is connected to the cathode wiring 108. The thickness of the organic EL element 10 can be set to 150 to 200 nm, for example.
On the insulating film 110, a plurality of cathode partition walls 112 are formed along a direction perpendicular to the anode wiring 104. The cathode partition 112 plays a role for spatially separating the plurality of cathode wirings 108 so that the wirings of the cathode wirings 108 do not conduct with each other. Accordingly, the cathode wiring 108 is disposed between the adjacent cathode partition walls 112. As the size of the cathode partition 112, for example, a configuration having a height of 2 to 3 μm and a width of 10 μm can be employed.

The substrate 11 is bonded with a sealing plate 116 and a sealing material 118 interposed therebetween.
Thereby, the space in which the organic EL element 10 is provided can be sealed, and the organic EL element 10 can be prevented from being deteriorated by moisture in the air. As the sealing plate 116, for example, a glass substrate having a thickness of 0.7 to 1.1 mm can be used.

In the image display device 100 having the above-described structure, a current can be supplied to the organic EL element 10 through the anode auxiliary wiring 106 and the cathode auxiliary wiring (not shown) by a driving device (not shown) to cause the light emitting layer to emit light. Then, light can be emitted from the substrate 11 through the substrate 11. The target image can be displayed on the image display device 100 by controlling the light emission and non-light emission of the organic EL element 10 corresponding to the above-described pixel by the control device.

"Lighting device"
Next, an example of a lighting device using the organic EL element 10 of the first embodiment will be described.
FIG. 3 is a diagram illustrating an example of a lighting device including the organic EL element 10.
3 is installed adjacent to the organic EL element 10 described above and the substrate 11 (see FIG. 1) of the organic EL element 10, and is connected to the anode 12 (see FIG. 1). And a terminal 203 connected to the cathode 14 (see FIG. 1) through the wiring layer 15, and a lighting circuit 201 for driving the organic EL element 10 connected to the terminal 202 and the terminal 203.

The lighting circuit 201 has a DC power source (not shown) and a control circuit (not shown) inside, and supplies current between the anode 12 and the cathode 14 of the organic EL element 10 through the terminal 202 and the terminal 203. Then, the organic EL element 10 is driven, the light emitting layer emits light, the light is emitted through the substrate 11, and used as illumination light. The light emitting layer may be made of a light emitting material that emits white light, and each of the organic EL elements 10 using light emitting materials that emit green light (G), blue light (B), and red light (R). A plurality of them may be provided so that the combined light is white.

“Second Embodiment”
FIG. 4 shows a second embodiment of the organic EL element according to the present invention. An organic EL element 20 shown in FIG. 4 includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode (metal layer, second electrode) 24 in this order on a substrate 11. To do. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 24 is a metal electrode made of a conductive metal material. The cathode 24 is a bottom emission type organic EL element 20 having a plurality of non-penetrating holes 24A formed from the surface on the organic layer 13 side and configured to extract light mainly from the anode 12 side. .
The difference between the organic EL element 20 of the second embodiment and the previous organic EL element 10 is that the hole 24A formed in the cathode 24 does not have a shape that penetrates the entire thickness direction of the cathode 24, but the thickness of the cathode 24. It is the point which is formed in the recessed part shape so that a part of the length may be left as the base part 24B, and has a shape in which one side of the hole part 24A is closed. The opening side of the hole 24 </ b> A of the cathode 24 is closed with the organic layer 13. In other structures, the organic EL element 20 has the same structure as that of the organic EL element 10 described above, and thus the description of the similar structure is omitted.

In the second embodiment, the hole portion 24A has a non-penetrating recess shape formed so as to dig a part of the cathode 24 in the thickness direction. As a typical shape of the hole portion 24A, like the through hole portion of the first embodiment, a cylindrical shape, an elliptical column shape, a polygonal column shape, a conical shape, a pyramid shape, a truncated cone shape, a truncated pyramid shape, and a hemispherical shape , And a shape in which these are combined. When the shape is tapered, the cross section may be linear or curved. That is, the cross-sectional shape and the planar shape of the hole 14A are not limited.

The size of the hole 24A can be defined by the minimum width and the maximum width of the hole 24A in plan view. The minimum width refers to the diameter of the maximum circle included in the hole 24A. The maximum width refers to the diameter of the minimum circle that includes the hole 24A. When the hole 24A is a perfect circle, the minimum width matches the maximum width. The minimum width of the hole 24A is preferably 200 nm or more, and the minimum width is more preferably 300 nm or more.

The interval between the holes 24A can be set to 50 nm or more, for example. The interval refers to the shortest distance not including the hole portion between the adjacent hole portions 24A. It is preferable that the maximum width of the hole 24A is as large as possible without overlapping the other hole 24A. The arrangement of the plurality of hole portions 24A may be periodic or aperiodic. Also in the organic EL element 20 provided with the hole 24A, the distance between the cathode 24 and the light emitting position becomes large at the in light emitting position, and it can be prevented that the light becomes SPP mode light. Furthermore, since the concavo-convex structure is formed on the cathode 24 which is an electrode made of metal, it is possible to take out the light which has become the SPP mode light.
In the second embodiment, the hole 24A is formed, and the base 24B, which is a part of the cathode 24, is formed above the hole 24A. Therefore, the emitted light is reflected from the cathode 24 without being taken out from the cathode 24 side. Is done. As a result, more light is extracted to the anode 12 side than the through hole portion 14A of the first embodiment. In order to suppress SPP, the depth of the hole 24A is preferably 100 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more.

In order to take out the SPP mode light in this way, the size of the hole 24A in the second embodiment is the same as the through hole 14A in the first embodiment. The ratio of the bottom area of the hole portion 24A to the region (the region combining the region and the out emission region) is preferably in the range of 20 to 90%. The bottom area of the hole 24A in plan view refers to the area of the hole 24A at the interface between the cathode 24 and the organic layer 13.
As a method of forming the hole 24A in the cathode 24, for example, a method of forming a hole at the time of film formation by vapor deposition or the like using a mask, a method of bonding a cathode having a separate hole formed by a transfer method or the like as described later, etc. There are bonding methods such as a transfer method. A method of sticking a layer having a constant film thickness on the upper surface after forming the through hole may be used. As a method for forming the through hole, the method shown in the first embodiment can be used.
As described above, in the first embodiment, an example in which the through-hole portion 14A is formed in the cathode 14 is shown, and in the second embodiment, an example in which the hole portion 24A that does not penetrate through the cathode 24 is shown. The cathode (metal layer) may have both through holes and holes.

“Third Embodiment”
FIG. 5 shows a third embodiment of the organic EL element according to the present invention. The organic EL element 30 shown in FIG. 5 includes a light emitting layer made of an anode (first electrode) 12 and an organic EL material on a substrate 11. An organic layer 23 including a cathode (metal layer, second electrode) 14 in this order. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 14 is a metal electrode made of a conductive metal material. The cathode 14 is a bottom emission type organic EL element 30 having a plurality of through-hole portions 14A and configured to extract light mainly from the anode 12 side.
In the organic EL element 30 of the present embodiment, the same materials and thicknesses as those of the first embodiment can be used for the substrate 11, the anode 12, and the cathode 14.

In the structure of the third embodiment, the difference from the organic EL element 10 of the first embodiment is that the organic layer 23 is located between the anode (first electrode) 12 and the cathode (metal layer, second electrode) 14. The first dielectric layer 27 having a low refractive index is provided, the first dielectric layer 27 has a plurality of hole portions 27A, and the organic layer 23 covers at least the inner surface of the hole portion 27A.
In the structure of the present embodiment, the formation position of the through hole portion 14 </ b> A and the formation position of the hole portion 27 </ b> A overlap in a plan view of the organic EL element 30. Accordingly, the first dielectric layer 27 is formed below the region where the cathode 14 exists. The organic layer 23 is formed below the through-hole portion 14A, but the edge portion 23a of the organic layer 23 is formed below the edge portion 14a of the cathode 14 located around the through-hole portion 14A. In FIG. 5, the first dielectric layer 27 is formed with the same thickness as the organic layer 23. However, the organic layer 23 is formed on the first dielectric layer 27, and the organic layer 23 formed in the hole 27A. May be formed continuously with the organic layer 23 on the first dielectric layer 27. That is, as shown in FIGS. 15A and 15B described later, the organic layer 23 is formed in a portion covering the inner surface of the hole 27A and a region sandwiched between the first dielectric layer 27 and the entire cathode 14. It is good also as a structure which has the layered part formed.
Furthermore, the formation position of the through hole 14A and the formation position of the hole portion 27A shown in FIG. 5 may be shifted from each other when the organic EL element 30 is viewed in plan.

The material of the first dielectric layer 27 is not particularly limited as long as it is light transmissive and has a refractive index lower than that of the organic layer 23. For example, when the refractive index of the organic layer 23 is 1.72, a metal fluoride such as SOG (typical refractive index: 1.25), MgF ₂ (typical refractive index: 1.38), PTFE, etc. Organic fluorine compounds, oxides such as SiO ₂ (typical refractive index: 1.45), various low-melting glasses, and porous materials.
The thickness of the first dielectric layer 27 is not particularly limited, but is, for example, 10 to 2000 nm, and preferably 50 to 1000 nm. If the thickness of the first dielectric layer 27 is less than 10 nm, the amount of light passing through the first dielectric layer 27 is small with respect to the emitted light traveling in the organic layer 23, so that guided mode light is difficult to be extracted. Become. If the thickness of the first dielectric layer 27 is greater than 2000 nm, it is difficult to maintain the flatness of the organic layer 23.

When comparing the refractive indexes of the structures, the refractive index of the organic layer 23 refers to the average refractive index of all the layers constituting the organic layer 23 including the light emitting layer made of an organic EL material. The same applies to other embodiments described later.
The shape of the hole 27A is not particularly limited as long as it has an effect of refracting light toward the substrate 11 on the inner surface thereof. From the viewpoint of refracting the guided mode light in a direction that is more perpendicular to the substrate surface (a plane parallel to the light emitting surface of the organic EL element), a shape in which the area on the cathode 14 side is smaller than the area on the anode 12 side is preferable. From the viewpoint of strongly refracting the guided mode light and taking it out with a smaller propagation distance, a shape with a surface area as small as possible is preferable. In the example shown in FIG. 5, the inner side surface is configured to be arranged perpendicular to the substrate surface, but is not limited to such a configuration.
The angle of the inner surface of the hole 27A with respect to the substrate surface is preferably 30 ° or more, more preferably 45 ° or more, and still more preferably 60 ° or more. By setting the inner surface to such an angle, guided mode light traveling toward the anode side enters the inner surface of the hole 27A from the outside, is refracted toward the substrate 11, and is extracted from the outer surface of the substrate 11 to the outside. .

The organic layer 23 may include a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, and the like in addition to a light emitting layer made of an organic EL material. The thing similar to what was used in embodiment can be used.

When the organic EL element 30 of the present embodiment having the through-hole portion 14A is energized so as to apply a potential difference between the anode 12 and the cathode 14, the light emitting layer inside the organic layer 23 emits light. Light can be extracted from the substrate 11 side through the anode 12 made of the above. In addition to the effect of the first embodiment in which the through hole portion 14A is provided in the cathode 14, in the present embodiment, as described above, the waveguide mode light can be extracted more efficiently by the first dielectric layer 27. The light extraction efficiency is improved as compared with the first embodiment.
In the present embodiment, light emission is particularly intense at the in emission position mainly from the organic layer 23 located below the through-hole portion 14A. Therefore, light emission at the in emission position is obtained, and light extraction efficiency is suppressed by suppressing SPP mode light. Can be high.

In the structure shown in FIG. 5, the example in which the through-hole portion 14A is formed in the cathode 14 is shown. However, the cathode 14 is not a through-hole, but the upper surface of the cathode is connected to the non-through-hole shown in the second embodiment. 24A may be formed. Even in this case, the effect of forming the hole 24A in the cathode 24 shown in the second embodiment and the effect of forming the first dielectric layer 27 shown in the third embodiment can be obtained together.
Furthermore, as a third embodiment, the anode 12 is continuously drilled (a hole that does not penetrate) is formed continuously with the plurality of holes 27A formed in the first dielectric layer 27, and the anode 12 is continuously formed with the hole 27A. Further, a form in which a through hole is formed, and a form in which the substrate is continuously drilled (a hole that does not pass through) is formed continuously with the hole 27A and the anode 12 may be employed.

“Fourth Embodiment”
6 and 7 show a fourth embodiment of the organic EL element according to the present invention. The organic EL element 40 shown in FIGS. 6 and 7 includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode (metal layer, second electrode) 14 on a substrate 11. In this order. A protective layer 44 made of a transparent conductive material such as ITO is provided between the cathode 14 and the organic layer 13. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 14 is a metal electrode made of a conductive metal material. The cathode 14 is a bottom emission type organic EL element 40 having a plurality of through-hole portions 14A and configured to extract light mainly from the anode 12 side.
The organic EL element 40 of the present embodiment is different from the organic EL element 10 of the first embodiment in that a protective layer 44 is provided. Here, the protective layer 44 is formed for the purpose of preventing the organic layer 13 from being damaged by energy such as heat when the through-hole portion 14 </ b> A is formed in the cathode 14. It is possible to prevent the organic layer 13 from being damaged by heat or pressure when the organic EL element 40 is formed using a method in which the cathode 14 separately formed with the through-hole portion 14A is bonded by a transfer method or the like. Any material can be used for the protective layer 44 as long as it is not a metal that generates SPP. For example, in the case of a conductive material, in addition to the protective effect described above, there is an advantage that the light emitting region can be both in light emission and out light emission.
In the organic EL element 40 of the present embodiment, the same materials and thicknesses as those of the first embodiment can be used for the substrate 11, the anode 12, the organic layer 13, and the cathode 14.

In the structure shown in FIGS. 6 and 7, an example in which the through hole portion 14 </ b> A is formed in the cathode 14 is shown. However, the cathode 14 is not penetrating the upper surface of the cathode shown in the second embodiment instead of the through hole. The hole 24A may be formed. Even in this case, the effect of forming the hole 24A in the cathode 24 shown in the second embodiment and the effect of forming the protective layer 41 shown in the fourth embodiment can be obtained together.

“Fifth Embodiment”
8 and 9 show a fifth embodiment of the organic EL element according to the present invention. 8 and 9 includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer made of an organic EL material, a cathode (second electrode) 54, and a dielectric material. An insulating layer 55 and a metal layer 56 are provided in this order. Both the anode 12 and the cathode 54 are transparent electrodes made of a transparent conductive material. The metal layer 56 is a bottom emission type organic EL element 50 having a plurality of through-hole portions 56A and configured to extract light mainly from the anode 12 side.
In the organic EL element 50 of this embodiment, the same materials and thicknesses as those of the first embodiment can be used for the substrate 11, the anode 12, and the organic layer 13. On the other hand, in the organic EL element 50, the cathode 54 is a transparent electrode made of a transparent conductive material, and the cathode 54 is the same as the protective layer 44 of the fourth embodiment described above when the through-hole portion 56A is formed in the metal layer 56. Bring about the effect. The material of the cathode 54 may be a known transparent conductive material such as a metal oxide or an organic conductive material, not a metal material that generates SPP. In particular, a material having a high refractive index compared to the refractive index in the insulating layer 55 or the through-hole portion 56 </ b> A and a high refractive index compared to the refractive index of the organic layer 13 is preferable. Furthermore, by setting the above refractive index, the cathode 54 / insulating layer 55 / metal layer 56 have an Otto type arrangement in the out emission region, so that the light extraction efficiency can be improved.

In the structure shown in FIGS. 8 and 9, an example in which the through hole portion 56A is formed in the metal layer 56 is shown. However, the metal layer 56 is not a through hole but a metal layer such as the cathode 24 shown in the second embodiment. You may form the hole part 24A which the upper surface connected and does not penetrate. Even in this case, the effect of forming the hole 24A in the cathode 24 shown in the second embodiment and the effect shown in the fifth embodiment can be obtained together. Furthermore, the metal layer of one organic EL element may have both a through hole and a hole.

“Sixth Embodiment”
FIG. 10 shows a sixth embodiment of the organic EL element according to the present invention. An organic EL element 60 shown in FIG. 10 includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode (metal layer, second electrode) 64 in this order on a substrate 11. To do. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 64 is a metal electrode made of a conductive metal material. The cathode 64 is a bottom emission type organic EL element 60 which has a plurality of non-penetrating holes 64A formed from the surface on the organic layer 13 side, and is configured to mainly extract light from the anode 12 side to the outside. is there.

In the organic EL element 60 of the present embodiment, the same materials and thicknesses as those of the first embodiment can be used for the substrate 11, the anode 12, and the organic layer 13. The organic EL element 60 of the present embodiment is obtained by bonding the cathode 64 with the hole 64A separately formed so as to be in contact with the organic layer 13 using a transfer method or the like. An Al layer or the like is separately formed on a substrate (not shown) and the like, and the cathode 64 is attached to the organic layer 13 by bonding. A known method can be used as the bonding method.

As another method, after the side surface portion of the hole portion 64A is first formed by the same method as that of the through hole portion of the other embodiments, a layer having a constant film thickness may be bonded to the upper surface by the above method. In this case, the layer to be bonded may be a material different from that of the side surface portion, but is preferably a layer that reflects light. Increasing the amount of reflected light can increase the amount of light extracted from the substrate 11 side.
This embodiment is particularly effective when it is difficult to form a through hole or a hole in the cathode on the organic layer. When forming a through hole or a hole in a cathode formed on an organic layer, a method of forming the organic layer by heat or light or a method using a solvent in which the organic layer dissolves is used. I can't. For this reason, for example, when the through-hole part and the hole part have a complicated shape or are fine, the bonding method of the present embodiment is effective.

The cathode 64 of the present embodiment has hole portions 64A formed with the same size and spacing as the hole portions 24A formed in the cathode 24 of the second embodiment, but the cathode 64 is the cathode 24 of the second embodiment. It is easy to make it thicker by several times, and it is easy to make the hole 64A deeper than the hole 24A of the cathode 24 of the second embodiment. The hole 64A is not deep enough to penetrate the entire thickness direction of the cathode 64, but is formed in a concave shape so as to leave a part of the cathode 64 as the base 64B. However, a form in which a through hole is formed may be used. .
The cathode 64 is in close contact with the organic layer 13 so that the opening side 64a of the hole 64A is closed by the organic layer 13.
In other structures, the organic EL element 60 has the same structure as that of the organic EL element 10 described above.

As shown in FIG. 10, the in-light emission position that overlaps the hole 64 </ b> A in plan view in the organic layer 13 has a larger distance from the cathode 64 than the out emission position, and the out-light emission position that does not overlap the hole 64 </ b> A. The distance between and becomes smaller.
Here, since the in light emission position is a region corresponding to the hole 64A with a large distance from the cathode 64, energy transfer to the SPP mode is small, generation of SPP mode light is small, and plasmon loss is small. In order to reduce the generation of the SPP mode light, the size of the inner diameter of the hole 64A is important, and the generation of the SPP mode light can be reduced at a position where the distance between the in light emission position and the cathode 64 is 100 nm or more. The light extraction efficiency can be improved.

If the depth of the hole 64A is 100 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more, the distance from the cathode 64 can be surely ensured at the in emission position. That is, the energy transfer to the SPP mode at the in emission position is small, the generation of SPP mode light is small, and the plasmon loss is small.
The occupied area ratio (ratio of the bottom area of the hole 64A to the light emitting region (in light emitting region + out light emitting region)) in plan view of the hole 64A of the present embodiment is preferably in the range of 20 to 90%. The bottom area of the hole 64A in plan view refers to the area of the hole 64A at the interface between the cathode 64 and the organic layer 13.

“Seventh Embodiment”
11 and 12 show a seventh embodiment of the organic EL element according to the present invention. An organic EL element 70 shown in FIG. 11 includes an anode (first electrode) 72, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode (metal layer, second electrode) 14 in this order on a substrate 11. To do. The anode 12 is a transparent electrode made of a transparent conductive material, and the cathode 14 is a metal electrode made of a conductive metal material. The cathode 14 is a bottom emission type organic EL element 70 having a plurality of through-hole portions 14A and configured to extract light mainly from the anode 12 side.
In the organic EL element 70 of this embodiment, the same materials and thicknesses as those of the first embodiment can be used for the substrate 11, the anode 72, the organic layer 13, and the cathode 14.

The structure of the seventh embodiment is different from the organic EL element 10 of the first embodiment in that the anode 72 includes a plurality of holes 72A, which is lower than the refractive index of the anode 72 and higher than the refractive index of the organic layer 13. The second dielectric layer 77 having a low refractive index is provided in the plurality of holes 72A.
The material of the second dielectric layer 77 is not particularly limited as long as it is light transmissive and has a refractive index lower than that of the anode 72 and lower than that of the organic layer 13. For example, when the material of the anode 72 is ITO (typical refractive index: 1.82) and the refractive index of the organic layer is 1.72, SOG (typical refractive index: 1.25), MgF ₂ Metal fluorides (typical refractive index: 1.38), organic fluorine compounds such as PTFE, oxides such as SiO ₂ (typical refractive index: 1.45), various low-melting glasses, porosity Examples include materials such as substances.
The thickness of the second dielectric layer 77 is not particularly limited, but is, for example, 10 to 2000 nm, and preferably 50 to 1000 nm. If the thickness of the second dielectric layer 77 is less than 10 nm, the amount of light passing through the dielectric layer 77 relative to the emitted light traveling in the organic layer 13 is small, so that waveguide mode light is difficult to be extracted. . If the thickness of the second dielectric layer 77 is thicker than 2000 nm, it becomes difficult to maintain the flatness of the organic layer 13.

The shape of the hole 72A is not particularly limited as long as it has an effect of refracting light toward the substrate 11 on the inner surface thereof. From the viewpoint of refracting the guided mode light in a direction more perpendicular to the substrate surface, a shape having a smaller area on the cathode 14 side than an area on the anode 72 side is preferable. From the viewpoint of strongly refracting the guided mode light and taking it out with a smaller propagation distance, a shape having a small bottom area is preferable. In the example illustrated in FIG. 11, the inner side surface is configured to be disposed perpendicular to the substrate surface, but is not limited to such a configuration.
The angle of the inner side surface of the hole 72A with respect to the substrate surface is preferably 30 ° or more, more preferably 45 ° or more, and still more preferably 60 ° or more. By setting the inner surface to such an angle, guided mode light directed toward the anode side enters the inner surface of the hole 72A from the outside, is refracted toward the substrate 11, and is extracted from the outer surface of the substrate 11 to the outside. .

In the structure shown in FIG. 11, light emission from the light emitting layer in the organic layer 13 can be obtained. In particular, in the in light emission position overlapping with the through hole portion 14A in plan view, the distance from the cathode 14 is larger than the out light emission position. At the out emission position that is large and does not overlap with the through-hole portion 14A, the distance from the cathode 14 is small.
For this reason, in the case of a material used for a general organic EL, light is easily emitted at an out emission position where the distance between the cathode and the anode is short. By using a highly conductive buffer layer as described above on the organic layer side of the anode and the cathode, light emission at the in light emission position can be strengthened. Furthermore, in the structure shown in FIG. 11, the positions of the cathode side through-hole portion 14A and the anode side second dielectric layer 77 coincide, but the present embodiment is not limited to this. Specifically, the through-hole portion 14A may coincide with the anode 72 in plan view or may be displaced.

Here, since the in light emission position is a region corresponding to the through-hole portion 14A with a large distance from the cathode 14, the generation of SPP mode light is small and the plasmon loss is small. In order to reduce the generation of the SPP mode light, the size of the inner diameter of the through hole portion 14A is important, and the generation of the SPP mode light is reduced at a position where the distance between the in light emission position and the cathode 14 is 100 nm or more. And the light extraction efficiency can be improved.
Therefore, the minimum width of the through hole portion 14A is preferably in the range of 100 to 1000 nm, and more preferably in the range of 150 to 800 nm.
In the structure shown in FIGS. 11 and 12, the example in which the through hole portion 14A of the cathode 14 is formed has been described. However, the present invention is not limited to this, and the cathode 14 has not the through hole but the upper surface of the cathode shown in the second embodiment. A connected non-penetrating hole 24A may be formed. Even in this case, the effect of forming the hole 24A in the cathode 24 shown in the second embodiment and the effect shown in the seventh embodiment can be obtained together.
In this case, the minimum width of the hole is preferably in the range of 100 to 1000 nm, and more preferably in the range of 150 to 800 nm.

Examples of organic EL elements according to the present invention will be described below. *

FIGS. 24A and 24B show a finite difference time domain (FDTD: FiniteFiDifference Time) in order to grasp the influence of the light source position on the light extraction efficiency with respect to the through hole portion 14A of the organic EL element of the first embodiment. The model structure of the organic EL element in the case of performing a computer simulation of the relative value of the radiation intensity (light extraction efficiency η) using the Domain method is shown. FIG. 24A is a schematic cross-sectional view of the model structure used for the calculation, and FIG. 24B is an enlarged perspective view of the through hole portion. The FDTD method is an analysis method for tracking the time change of the electromagnetic field at each point in space by differentiating Maxwell's equation describing the time change of the electromagnetic field spatially and temporally. More specifically, a calculation method is adopted in which light emission in the light emitting layer is regarded as radiation from a minute dipole, and time variation of the radiation (electromagnetic field) is tracked.

The calculation shows that the direction of the micro dipole is X direction (direction parallel to the substrate surface), Z direction (direction perpendicular to the substrate surface) and random direction (dipole direction is randomly oriented in XYZ space) I went about the case. Here, the light radiated from the dipole in the XY direction is mainly light propagating in the direction perpendicular to the substrate surface, and the light radiated from the dipole in the Z direction is mainly light propagated in the direction parallel to the substrate surface. is there. Therefore, in the following description, the light emitted from the X-direction dipole is the vertical propagation light, the light emitted from the Z-direction dipole is the parallel propagation light, and the light emitted from the random dipole is the random propagation light. I will call it.

The propagation light in the parallel direction is light that is confined inside the device as waveguide mode light or SPP mode light in a normal organic EL device having no through-hole portion. Therefore, by calculating the degree of improvement in the extraction efficiency of the parallel propagation light, the high light extraction performance of the organic EL element of the present invention can be evaluated. Random propagation light has a light emission state similar to the light emission state of an actual organic EL device, and the magnitude of the external quantum efficiency of the actually created device is estimated by comparing the light extraction efficiency of this random propagation light. It is possible. Therefore, unless otherwise specified, the high light extraction efficiency with respect to random propagation light is used as a reference for evaluating the high light extraction performance.

The model structure of the organic EL element 82 of the first embodiment shown in FIGS. 24A and 24B is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. Assuming that the anode 12 is made of ITO, the refractive index is set to 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated by a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 14 is made of Al, and the refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and the other wavelengths are extrapolated by the Drude model.

The through-hole portions 14A (set to a radius of 800 nm) formed in the cathode 14 are arranged in a square lattice with a period of 2000 nm, and the medium in the through-hole portion 14A is nitrogen, and the refractive index is 1.0. The film thicknesses of the anode 12, the organic layer 13, and the cathode 14 were 150 nm, 100 nm, and 100 nm, respectively.
As shown in FIG. 24A, the center of the through-hole portion 14A is set as the origin (0), and the light source is simulated at a position away from this position by 200, 400, 600, 800, 1000 nm in the in-plane direction. It was. 24A and 24B, the light source positions when the light source positions are 0 nm (in light emission) and 1000 nm (out light emission) are indicated by stars.
For comparison, a simulation was also performed for the same configuration (standard) except that the through-hole portion 14A was not formed in the cathode 14.

The simulation result is shown in FIG. FIG. 25A shows the wavelength dependence of the light extraction efficiency η of parallel direction propagation light to the glass substrate, and FIG. 25B shows the wavelength dependence of the light extraction efficiency η of random direction propagation light to the glass substrate. Show.
This simulation examined how the light extraction efficiency changes depending on the position from when the light source is in the center of the through-hole portion 14A (in light emission) to when the light source is under the metal electrode (out light emission). Become.

From the results shown in FIG. 25, the light extraction efficiency is improved wherever the light emission position is, compared to the case where there is no through-hole portion 14A (standard). In particular, since there is no cathode (metal layer) in the vicinity of the through-hole portion 14A, SPP can be suppressed, and the effect of forming the through-hole portion 14A can be confirmed.
The emitted light generated at the lower portion of the cathode (metal layer) 14 is captured as SPP mode light at the upper cathode (metal layer) 14, but is re-radiated at the through-hole portion 14 A as described above to extract the SPP. Light extraction efficiency is improved.

The light emitting part in the organic EL element is in the vicinity of the shortest path between the electrodes. In the case of the organic EL element having the structure used in this calculation, the lower part of the cathode (metal layer) 14 emits light (that is, out light emission) in a normal organic material. However, as described above, when the buffer layer is formed of a material having good conductivity on the cathode (metal layer) 14 side of the organic layer 13, the entire surface can emit light. In order to emit light (that is, in light emission) only inside the through hole portion having a high SPP suppressing effect, it can be handled by forming an insulating layer in a part between the cathode (metal layer) and the organic layer.
The light extraction efficiency when light is emitted from the entire surface is an integrated result of calculation using each part as a light source. As a result, it can be said that the light extraction is improved by forming the through-hole portion in any light emission mode.
The same can be said for the organic EL element of the second embodiment in which a hole that does not penetrate is formed.

FIGS. 13 and 14 show the results of computer simulation of the light extraction efficiency η using the same FDTD method as in the previous example in order to confirm the effect of the organic EL element of the first embodiment.

The model structure of the organic EL element 10 of the first embodiment used in the simulation is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. The anode 12 is made of ITO, and the refractive index is 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 14 is made of Al. The refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Drude model.

The medium in the through-hole portion 14A formed in the cathode 14 is nitrogen, and a refractive index of 1.0 is used. The thicknesses of the anode 12, the organic layer 13, and the cathode 14 were 150 nm, 100 nm, and 100 nm, respectively.
Under the above conditions, assuming that the radius of the plurality of through-hole portions 14A formed on the cathode 14 in a square lattice arrangement is r and the period is p, (r (nm), p (nm)) = (50,500) , (100, 500), (200, 500), (400, 1000), (800, 2000), (1200, 3000), and (1800, 4000). For comparison, a simulation was also performed for the same configuration (standard) except that the through-hole portion 14A was not formed in the cathode 14.

FIG. 13 is a simulation result of the in-light emission position corresponding to the through-hole portion 14A. FIGS. 13A to 13C show light extraction from the vertically propagated light, parallel propagated light, and randomly propagated light to the glass substrate, respectively. The wavelength dependence of the efficiency η is shown.
FIG. 14 shows the simulation results of the out emission position corresponding to the through-hole portion 14A. FIGS. 14A to 14C show the light extraction of the vertical propagation light, parallel propagation light, and random propagation light to the glass substrate, respectively. The wavelength dependence of the efficiency η is shown.
From the results shown in FIGS. 13 and 14, it is understood that the light extraction efficiency is improved when the through-hole portion 14 </ b> A is formed as compared with the case where there is no through-hole portion (standard). It can also be seen that the light extraction performance is further improved by setting the radius of the through-hole portion 14A to 50 nm or more, more preferably 100 nm or more.

FIGS. 15A and 15B show model structures of the organic EL elements 80 and 81 used in the simulation in order to confirm the effect of the organic EL element of the third embodiment. FIG. 16 shows the result of computer simulation of the light extraction efficiency η for the element having the structure shown in FIG. 15 using the FDTD method similar to the previous example. In FIG. 15A, the anode 32, the first dielectric layer 27, and the organic layer 23 are formed on the substrate 11, and the hole 32A formed in the anode 32 and the hole 27A formed in the first dielectric layer 27 are formed. An example of the organic EL element 80 formed so as to be filled with a part of the organic layer 23 and provided with the cathode 14 having the through-hole portion 14A on the organic layer 23 is shown.
15B, the anode 12, the first dielectric layer 27, and the organic layer 23 are formed on the substrate 11, and the hole 27A formed in the first dielectric layer 27 is filled with a part of the organic layer 23. An example of the organic EL element 81 formed and provided with the cathode 14 having the through-hole portion 14A on the organic layer 23 is shown.
In either case, the organic layer 23 has a layered portion.

FIG. 16 shows the result of computer simulation of the light extraction efficiency η using the organic EL element 80 and the organic EL element 81 as models. In the graph, “F.15. (A)” is the result of the organic EL element 80 and “F.15. (B)” is the result of the organic EL element 81. “Pole only” is the result of the same configuration as the organic EL element 81 except that the first dielectric layer 27 is not provided, and “standard” is “hole only” except that the through hole portion 14A is not formed in the cathode 14. Is the result of the same configuration. Various conditions of the simulation are as described in FIG. FIG. 16 shows the simulation result of the in-light emission position, and FIGS. 16A to 16C show the wavelength dependence of the light extraction efficiency η of the vertically propagating light, the parallel propagating light, and the random propagating light to the glass substrate, respectively. Show.
From the result shown in FIG. 16, the organic layer 23 is introduced by forming a hole portion up to the first dielectric layer 27 or the anode 32 below the structure having only the through hole portion formed in the cathode 14 (hole only). The light extraction efficiency was improved in the structure (organic EL elements 80 and 81).
This is because a waveguide mode light extraction structure in which holes are formed in the anode and the first dielectric layer and a part of the organic layer 23 is introduced into these holes is introduced. It can be seen that the structure shown in FIG. 15A (organic EL element 80) is slightly higher in light extraction efficiency than the structure shown in FIG. 15B (organic EL element 81).

17 and 18 show the results of computer simulation of the light extraction efficiency η using the same FDTD method as in the previous example in order to confirm the effect of the organic EL element of the fourth embodiment.
The model structure of the organic EL element 40 of the fourth embodiment used in the simulation is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. The anode 12 is made of ITO, and the refractive index is 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 14 is made of Al. The refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Drude model.

The through holes 14A (set to a radius of 800 nm) formed in the cathode 14 are arranged in a square lattice with a period of 2000 nm, the medium in the through holes 14A is nitrogen, and the refractive index is 1.0. The film thicknesses of the anode 12, the organic layer 13, and the cathode 14 were 150 nm, 100 nm, and 100 nm, respectively.
As the protective layer 44 is made of ITO, the above-described refractive index is used, and a simulation is performed for each of the film thicknesses of 50 nm, 100 nm, and 150 nm. For comparison, a simulation was also performed on a model structure (standard) using a cathode in which the protective layer 44 and the through-hole portion 14A were not formed.

FIG. 17 shows simulation results of the in-light emission position corresponding to the through-hole portion 14A, and FIGS. 17A and 17B show the wavelength of light extraction efficiency η of vertically propagated light and parallel propagated light to the glass substrate, respectively. Indicates dependency.
FIG. 18 is a simulation result of the out emission position corresponding to the through-hole portion 14A, and FIGS. 18A and 18B show the wavelength of light extraction efficiency η of vertically propagating light and parallel propagating light to the glass substrate, respectively. Indicates dependency.
Since the result of the random propagation light can be understood from the result of the vertical propagation light and the horizontal propagation light, it can be seen that the light extraction efficiency is improved. Since this structure emits light entirely, it can be said that the light extraction efficiency is improved overall.

19 and 20 show the results of computer simulation of the light extraction efficiency η using the same FDTD method as in the previous example in order to confirm the effect of the organic EL element of the fifth embodiment.
The model structure of the organic EL element 50 of the fifth embodiment used in the simulation is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. The anode 12 is made of ITO, and the refractive index is 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 54 is made of ITO, and the above values are used. The insulating layer 55 is made of SiO ₂ , and the refractive index is 1.45. Assuming that the metal layer 56 is made of Al, the refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Drude model.

The through-hole portions 56A (set to a radius of 800 nm) formed in the metal layer 56 were arranged in a square lattice pattern with a period of 2000 nm. The medium in the through hole portion 56A of the metal layer 56 is nitrogen, and the refractive index is 1.0. The film thicknesses of the anode 12, the cathode 54, the organic layer 13, and the metal layer 56 were 150 nm, 50 nm, 100 nm, and 100 nm, respectively.
As the film thickness of the insulating layer 55 (SiO ₂ ), simulation was performed in each of 50 nm, 100 nm, and 200 nm. For comparison, a simulation was also performed for the same case (standard) as the above model structure except that neither the insulating layer 55 nor the metal layer 56 was formed and the cathode was made of Al.

FIG. 19 is a simulation result of the in light emission position corresponding to the through-hole portion 56A on the Bottom side, and FIGS. 19A and 19B are light extraction efficiencies of vertically propagated light and parallel propagated light to the glass substrate, respectively. The wavelength dependence of η is shown.
FIG. 20 is a simulation result of the out emission position corresponding to the through-hole portion 56A on the Bottom side, and FIGS. 20A and 20B are light extraction efficiencies to the glass substrate of vertical direction propagation light and parallel direction propagation light, respectively. The wavelength dependence of η is shown.
Since the random propagation light can be understood from the results of the vertical propagation light and the horizontal propagation light, it can be seen that the light extraction property is improved. Since this structure emits light entirely, it can be said that the light extraction efficiency is improved overall.

FIG. 21 shows the result of computer simulation of the light extraction efficiency η using the FDTD method similar to the previous example in order to confirm the effects of the organic EL elements of the second embodiment and the sixth embodiment.
The model structure of the organic EL element 60 of the sixth embodiment used in the simulation is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. The anode 12 is made of ITO, and the refractive index is 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 64 is made of Al, the refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Drude model.

The holes 64A (set to a radius of 800 nm and a depth of 800 nm) formed in the cathode 64 were assumed to have a cylindrical shape (col) or a hemispherical shape (hemi), and were arranged in a square lattice with a period of 2000 nm. The medium in the hole 64A of the cathode 64 is nitrogen and the refractive index is 1.0. The layer thicknesses of the anode 12 and the organic layer 13 were 150 nm and 100 nm, respectively. For comparison, a simulation was also performed for a case (standard) in which a cathode in which no hole was formed was used.

FIG. 21 is a simulation result of the in light emission position corresponding to the hole 64A and the out light emission position not corresponding to the hole 64A on the Bottom side. FIGS. 21 (a) to 21 (c) are vertical propagation light and parallel propagation light, respectively. The wavelength dependence of light extraction efficiency (eta) to the glass substrate of light and random propagation light is shown.
In and out shown in FIG. 21 indicate light emission positions, _col indicates a cylindrical shape, and _hemi indicates a hemispherical shape.

In the simulation results shown in FIG. 21, there is no significant difference in the light extraction efficiency results when the hole shape is a cylindrical shape and a hemispherical shape, and the value of the light extraction efficiency η is the shape of the hole 64A of the cathode 64. It turns out that it does not depend largely on. This is probably because the shortest distance from the in emission position shown in FIGS. 4 and 10 to the cathode is the same for the cylindrical shape and the hemispherical shape. Even in a configuration that employs a structure in which a hole portion that does not penetrate the cathode is employed, the same tendency as the simulation results of each of the previous embodiments that employ a structure in which a cathode portion made of an Al layer is provided with a through hole portion was exhibited. .

FIG. 22 shows the result of computer simulation of the light extraction efficiency η using the same FDTD method as in the previous example in order to confirm the effect of the organic EL element of the seventh embodiment.
The model structure of the organic EL element 70 of the seventh embodiment used in the simulation is the same as the structure shown in FIG. The substrate 11 is made of glass, and a refractive index of 1.52 is used. Assuming that the anode 72 is made of ITO, the refractive index is set to 1.82 + 0.009i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Lorentz model. As the refractive index of the organic layer 13, 1.72 was used. The cathode 14 is made of Al. The refractive index is 0.649 + 4.32i at a wavelength of 550 nm, and other wavelengths are extrapolated using a Drude model.

The through-hole portions 14A (set to a radius of 800 nm and a depth of 800 nm) formed in the cathode 14 were arranged in a square lattice with a period of 2000 nm. The medium in the through-hole portion 14A of the cathode 14 was nitrogen, and the refractive index was 1.0. In the anode 72, the hole 72A (radius 800 nm) was formed in a square lattice pattern with a period of 2000 nm with the same center position in plan view as the through hole 14A of the cathode 14. A second dielectric layer 77 was formed in the hole 72 A of the anode 72. The second dielectric layer is made of SiO ₂ and has a refractive index of 1.45.
The film thicknesses of the anode 72, the organic layer 13, and the cathode 14 were 150 nm, 100 nm, and 100 nm, respectively. For comparison, a simulation was also performed in the case where a model structure (standard) in which neither the through-hole portion nor the hole portion was formed in the cathode 14 and the anode 72 was used.
In this simulation, the in light emission position (“in” in the figure) overlaps with the position of the through-hole part 14A formed in the cathode 14, and the out light emission position (“out” in the figure) extends from the through-hole part 14A. This corresponds to the shifted position. In the figure, “inP” indicates that the through-hole portion 14A and the hole portion 72A overlap each other in plan view, and “outP” indicates that the through-hole portion 14A and the hole portion 72A are shifted from each other in plan view. To express.

FIG. 22 is a simulation result of the in light emission position corresponding to the hole 14A and the out light emission position not corresponding to the hole 14A on the Bottom side. FIGS. 22 (a) to 22 (c) are vertical direction propagation light and parallel direction propagation light, respectively. The wavelength dependence of light extraction efficiency (eta) to the glass substrate of light and random propagation light is shown.

From the simulation results shown in FIG. 22, it can be seen that in light emission has a very high extraction efficiency. This is apparent in comparison with a structure in which the dielectric layer 77 is not provided (result of FIG. 26 described later). In particular, it can be seen that a high extraction efficiency can be obtained when the hole 72A is located at a position shifted from the in light emission position by in light emission.

FIG. 23 shows a structure in which an ITO anode and an organic layer are formed on a glass substrate, an ITO film having a thickness of 50 nm is formed, and a 100 nm-thick Al film is stacked thereon as a cathode. A SEM photograph (scanning electron micrograph) showing a result of a test of forming a through-hole portion in the Al layer as a cathode by irradiation with the second harmonic of a Yb-YAG laser of It is.
FIG. 23 (a) is a 50,000 times magnified photograph of the through hole formed in the Al layer, and FIG. 23 (b) is a 3000 magnified photograph of the through hole. The through hole is formed on the cathode made of the Al layer. You can see that it has been processed. FIG. 23 (c) is a 50,000 times enlarged photograph of a through hole portion formed in an Al layer having the same structure as above, and FIG. 23 (d) is a 3000 times enlarged photograph of the through hole portion. It can be seen that the through-hole portion can be processed.
The samples shown in FIGS. 23A and 23B are the results under the conditions of a laser output of 75 mW and an incident angle of the laser beam of 14 degrees. The samples shown in FIGS. The results are obtained under the conditions of an output of 150 mW and a laser beam incident angle of 6 degrees.
When these structures were energized, it was confirmed that they actually emitted light.

FIG. 26 shows an anode 12, an organic layer 13 including a light emitting layer made of an organic EL material, and a cathode 64 in this order on a substrate 11 used for confirming the effect of the organic EL element of the sixth embodiment. The model structure of the organic EL element 83 provided is shown. The cathode 64 is formed with the same radius and cycle as the hole 64A formed in the cathode 64 of the previous sixth embodiment. The difference from the previous example is that a part of the organic layer 13 is embedded in the hole 64A. The organic layer 13 is composed of a portion in which the hole 64 is embedded and a layered portion.
Using the structure shown in FIG. 26 as a model, the light extraction efficiency η was computer-simulated using the same FDTD method as in the previous example based on the conditions shown in FIG. In this simulation, each simulation was performed when the depth h of the hole 64A was 50, 100, 200, 400, 600, and 800 nm. For comparison, a simulation was also performed for a model structure in which a hole was not formed in the cathode (standard).

FIG. 27 shows the simulation results of the in-light emission position corresponding to the hole 64A. FIGS. 27A to 27C show the light extraction efficiency of the vertical propagation light, parallel propagation light, and random propagation light to the glass substrate, respectively. The wavelength dependence of η is shown.
In the result shown in FIG. 27, the light extraction efficiency improves as the hole 64A is deepened. It can be seen that when the inside of the hole 64A is a medium having a low refractive index, the light extraction performance is remarkably improved. The depth of the hole 64A is preferably 50 nm or more, more preferably 100 nm or more, and most preferably 150 nm or more.

FIG. 28 is the same as FIG. 26 and used for confirming the effect of the organic EL device of the sixth embodiment. On the substrate 11, the anode 12, the organic layer 13 including a light emitting layer made of an organic EL material, and the cathode The structure of the organic EL element 84 which comprises 64 is shown. The cathode 64 is formed with the same radius and cycle as the hole 64A formed in the cathode 64 of the previous sixth embodiment. The medium in the hole 64 was nitrogen and the refractive index was 1.0.
As the model structure shown in FIG. 28, the light extraction efficiency η was computer-simulated using the same FDTD method as in the previous example based on the conditions shown in FIG. In this simulation, each simulation was performed when the depth h of the hole 64A was 50, 100, 200, 400, 600, and 800 nm. For comparison, a simulation was also performed for a model structure (standard) in which no hole was formed in the cathode.

FIG. 29 is a simulation result of the in light emission position corresponding to the hole 64A, and FIGS. 29A to 29C show the light extraction efficiency of the vertical direction propagation light, parallel direction propagation light, and random propagation light to the glass substrate, respectively. The wavelength dependence of η is shown.
From the results shown in FIG. 29, when the medium of the hole 64A is nitrogen and the refractive index is 1.0, the light extraction efficiency decreases as the height increases in the vertical propagation light, and increases in the parallel propagation light. It can be seen that the higher the value, the higher the efficiency.
From FIG. 29 (b), it can be seen that the SPP is hardly excited if the depth of the hole 64A is 400 nm or more, and it is considered that the SPP can be suppressed although there is some excitation at 200 nm.

DESCRIPTION OF SYMBOLS 10 ... Organic EL element, 11 ... Board | substrate, 12 ... Anode, 13 ... Organic layer, 14 ... Cathode, 14A ... Through-hole part, 20 ... Organic EL element, 23 ... Organic layer, 24 ... Cathode, 24A ... Hole part, 27 1st dielectric layer, 27A ... hole, 30 ... organic EL element, 32 ... anode, 32A ... hole, 40 ... organic EL element, 44 ... protective layer, 50 ... organic EL element, 54 ... cathode, 55 ... Insulating layer, 56 ... metal layer, 56A ... through hole, 60 ... organic EL element, 64 ... cathode, 64A ... hole, 70 ... organic EL element, 72 ... anode, 72A ... hole, 77 ... second dielectric Layers 80... Organic EL elements 81. Organic EL elements 82. Organic EL elements 83. Organic EL elements 84. Organic EL elements 100.

Claims (14)

An organic EL element in which an organic layer including a light emitting layer is sandwiched between a pair of opposed electrodes, one electrode is a metal electrode, and the other electrode is a transparent electrode, mainly from the transparent electrode side. The organic EL device is characterized in that light is extracted from the metal electrode, and the metal electrode has a plurality of through-hole portions or a plurality of non-penetrating hole portions formed from the surface on the organic layer side. An organic EL device comprising a first electrode, an organic layer including a light emitting layer, and a metal layer in this order,
The first electrode is a transparent electrode made of a transparent conductive material,
The metal layer is a second electrode;
The metal layer has a plurality of through-hole portions or a plurality of non-through holes formed from the surface on the organic layer side,
The organic EL element, wherein the first electrode side is a main light extraction side. 3. The organic EL element according to claim 2, wherein the first electrode is an anode formed on a substrate, and the metal layer is a cathode. The organic EL element according to claim 2 or 3, wherein the minimum width of the through hole is 100 nm or more. 5. The organic EL according to claim 2, wherein the minimum width of the non-penetrating hole is 200 nm or more, and the interval between the non-penetrating holes adjacent to each other is 50 nm or more. element. 6. The organic EL element according to claim 5, wherein the maximum width of the non-penetrating hole is not less than the interval. The organic EL device according to any one of claims 2 to 6, wherein the thickness of the metal layer is in the range of 50 to 1000 nm. The organic EL device according to any one of claims 2 to 7, further comprising a protective layer between the organic layer and the metal layer. The organic EL element according to any one of claims 2 to 7, wherein the metal layer is in contact with the organic layer. A first dielectric layer having a refractive index lower than the refractive index of the organic layer and having a plurality of holes is provided between the first electrode and the metal layer, and the organic layer is at least the The organic EL element according to any one of claims 2 to 9, wherein the organic EL element covers an inner surface of the hole. The first electrode includes a plurality of first electrode holes, and a second dielectric layer having a refractive index lower than the refractive index of the first electrode and lower than the refractive index of the organic layer is provided in the first electrode hole. The organic EL device according to any one of claims 2 to 10, wherein the organic EL device is provided inside the device. An organic EL device comprising a first electrode, an organic layer including a light emitting layer, a second electrode, an insulating layer, and a metal layer in this order,
The first electrode and the second electrode are both transparent electrodes made of a transparent conductive material,
The metal layer has a plurality of through-hole portions or a plurality of non-through holes formed from the surface on the organic layer side, and the first electrode side is a main light extraction side. An image display device comprising the organic EL element according to any one of claims 1 to 12. An illumination device comprising the organic EL element according to any one of claims 1 to 12.

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