WO2014084200A1 - Organic electroluminescent element, and image display device and lighting device provided with same - Google Patents

Abstract

An organic electroluminescent element (10) is provided with, in order, anodes (2), an organic layer (3) that includes a light-emitting layer comprising an organic electroluminescent material, and a cathode (4). The cathode (4) has a plurality of emission starting point sections (4a) periodically disposed on a surface (4A) on the organic layer side. The anodes (2) are provided with a plurality of anode holes wherein the inner surfaces (2a) of the anodes (2) are covered by a dielectric layer (7) having a refractive index that is lower than the refractive index of the anodes (2). The organic layer (3) has a layered section (3a) disposed between the anodes (2) and the dielectric layer (7), and the cathode (4). The anode holes are characterized by being disposed in positions that overlap with the emission starting point sections (4a) in a plan view.

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. 2012-259010 filed in Japan on November 27, 2012, the contents of which are incorporated herein by reference.

Organic EL elements have features such as a wide viewing angle, high-speed response, and clear self-luminous display. They are thin, lightweight, and have low power consumption. As expected.
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 small incident angle (incident light and incident light) below the critical angle at the interface between the transparent substrate (for example, glass (refractive index: 1.52)) and air (refractive index: 1.0) The light incident at an angle formed by the normal of the interface is refracted at the interface and extracted outside the device. In this specification, these lights are called 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. In this specification, this light is referred to as substrate mode light, and the loss due to this is referred to as substrate loss.
Of the light emitted from the light-emitting layer, light incident on the interface between the substrate and the cathode at an incident angle greater than the critical angle is also totally reflected at the interface and is not extracted outside the device, but is finally absorbed by the material. sell. As the interface between the substrate and the cathode, for example, 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)), the interface between the high refractive index layer and the low refractive index layer disposed between the anode and the cathode, etc. In this specification, this light is referred to as waveguide mode light. This loss is called waveguide loss.
Of the light emitted from the light-emitting layer, the light is incident on the surface of the metal layer such as the metal cathode and coupled with free electron vibration of the metal cathode, and is captured on the surface of the metal cathode as surface plasmon polariton (SPP). Can not be taken out of the device and can be finally absorbed by the material. In this specification, this light is referred to as SPP mode light, and the resulting loss 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 limited to about 20% (for example, Patent Document 1). 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, the extraction of the substrate mode light can be dealt with by providing a light diffusion sheet or the like on the transparent substrate (for example, Patent Document 2). However, research on the reduction and extraction of guided mode light and SPP mode light, particularly reduction and extraction of SPP mode light, has just started.

The guided mode light is generated when total reflection occurs when light enters the low refractive index material from the high refractive index material. Therefore, in order to reduce the guided mode light, there are known measures for reducing the guided mode light by making the total reflection less likely to occur or by reducing the ratio of the light causing the total reflection.
Patent Document 3 discloses a configuration in which a high refractive index layer having a higher refractive index than that of an organic light emitting layer or a transparent electrode is inserted in the vicinity of the organic light emitting layer. Patent Document 2 discloses a configuration in which the refractive index of the organic light emitting layer and the transparent electrode is equivalently lowered by dispersing fine particles having a refractive index lower than that of the organic light emitting layer and the transparent electrode in the organic light emitting layer and the transparent electrode. ing.

Patent Documents 4 and 5 disclose a configuration in which holes (cavities) are formed in an anode layer and a dielectric layer that are sequentially formed on a substrate.
Light incident on the side surface of the cavity (interface extending perpendicular to the substrate) is refracted toward the substrate at this interface. With this effect, the ratio of light that causes total reflection can be reduced by changing the incident angle of the guided mode light to a small angle.

On the other hand, as a method of extracting SPP mode light trapped on the surface of the metal layer, a configuration in which a periodic uneven structure is formed on the surface of the metal layer is known (Patent Documents 6 to 9).

JP 2008-210717A JP 2011-243625 A JP 2011-233288 A Special table 2003-522371 JP 2011-82192 A JP 2006-313667 A JP 2009-158478 A JP 2005-535121 Gazette JP 2004-31350 A

However, even if the SPP mode light is extracted into the organic layer, the light extraction efficiency cannot be improved unless the light can be extracted outside the device.

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

The present inventors first assume a two-step light extraction mechanism in which SPP mode light is extracted as light into an organic layer, and then the light is extracted outside the device without being guided mode light. From a number of structures, an effective structure that improves the light extraction efficiency has been intensively studied based on simulations.
Since it is difficult to directly measure the light extraction efficiency, we examined it based on simulation.

The two-step light extraction mechanism is a reflective electrode having a plurality of radiation starting points that are periodically arranged to generate SPP mode light and allow the generated SPP mode light to be extracted into the organic layer as propagating light It consists of a side structure and a transparent electrode side structure for extracting the propagation light to the outside.

The radiation starting point portion of the reflecting electrode side structure is a portion from which the SPP mode light captured on the reflecting electrode surface made of a light reflecting material such as metal is re-radiated.
When the angular frequency of the SPP mode light generated on a flat metal surface is ω and the wave vector is k _sp , this dispersion relation is expressed by the real part ε _m of the dielectric constant of the metal and the dielectric that contacts the metal surface. It is determined by the dielectric constant ε _{d and} is approximately given by the following equation (1) (c is the speed of incident light).

On the other hand, the magnitude of the wave number of light propagating in the dielectric is given by the following equation (2).

In a material such as a metal used as a reflective electrode of an organic EL, since ε _m <0, Equation (2) is smaller than the wave number k _sp of SPP mode light and does not have an intersection with the dispersion curve of Equation (1). Therefore, the propagating light in the dielectric cannot excite the SPP mode light directly on the metal surface. Conversely, SPP mode light present on a flat metal surface cannot be extracted directly into the dielectric as propagating light.

Even in the organic EL element, when the surface of the reflective electrode is flat and does not have a structure, the SPP mode light is not taken out into the organic layer but is lost. However, when a concave (convex) structure is provided on the reflective electrode surface, the SPP mode light is diffracted by the concave (convex) structure, and light is re-emitted as propagating light into the organic layer around the concave (convex) structure.
That is, this concave (convex) structure of the reflective electrode side structure functions as a radiation starting point.

Next, the transparent electrode side structure will be described below.
As the transparent electrode side structure, an interface having a refractive index perpendicular or nearly perpendicular to the transparent electrode was introduced. By this interface, the propagating light in the organic layer is refracted, and the incident angle to the transparent electrode surface opposite to the organic layer (the angle formed by the normal of the interface on which the light enters) and the exit angle from this surface are small. Become.
More specifically, a structure having an interface (inner side surface of a hole) between a transparent electrode having a hole and a dielectric layer covering the hole was introduced on the transparent electrode side.

By simulation, the present inventors refracted the reflection electrode side structure having a radiation starting point part and refracted the propagating light in the organic layer to the side opposite to the organic layer when viewed from the transparent electrode. By combining the transparent electrode side structure with the interface, it has been found that the reflective electrode side structure and the transparent electrode side structure have a remarkable effect that cannot be predicted from the effect of improving the light extraction efficiency of the single electrode. Was completed.

In order to achieve the above object, the present invention employs the following configuration.
(1) A transparent electrode, an organic layer including a light emitting layer made of an organic EL material, and a reflective electrode are sequentially provided, and the reflective electrode is a plurality of radiation origins periodically disposed on the surface of the organic layer. The transparent electrode includes a plurality of holes whose inner surface is covered with a dielectric layer having a refractive index lower than that of the transparent electrode, and the organic layer includes the transparent electrode. And a layered portion disposed between the dielectric layer and the reflective electrode, wherein the radiation starting point portion is disposed at a position overlapping the hole portion in plan view. EL element.
(2) The transparent electrode has a substrate on a surface opposite to the organic layer, and is configured to extract light from the transparent electrode side to the outside. The transparent electrode is an anode, and the reflective electrode is It is a cathode, The organic EL element as described in (1) characterized by the above-mentioned.
(3) The organic EL element according to any one of (1) and (2), wherein the hole portion and the radiation starting point portion have respective center axes orthogonal to the substrate.
(4) The organic EL element according to any one of (1) to (3), wherein the radiation starting point is a recess.
(5) An image display device comprising the organic EL element according to any one of (1) to (4).
(6) An illuminating device comprising the organic EL element according to any one of (1) to (4).

According to the present invention, it is possible to provide an organic EL element in which the SPP mode light and the extracted propagation light in the organic layer are effectively extracted to improve the light extraction efficiency, and an image display device and an illumination device including the organic EL element.

It is a cross-sectional schematic diagram for demonstrating an example of the organic EL element which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating the effect of the organic EL element shown in FIG. It is a cross-sectional schematic diagram for demonstrating an example of the image display apparatus provided with the organic EL element of this invention. It is a cross-sectional schematic diagram for demonstrating an example of the illuminating device provided with the organic EL element of this invention. It is a cross-sectional schematic diagram for demonstrating a part of manufacturing method of the organic EL element which concerns on one Embodiment of this invention. It is a part of manufacturing method of the organic EL element which concerns on one Embodiment of this invention, and is a cross-sectional schematic diagram for demonstrating the process after FIG. 5A. It is a figure which shows the result of computer simulation calculation of the light extraction efficiency (relative value) of the organic EL element (pitch: 500 nm) of one Embodiment of this invention, (a) is vertical propagation light, (b) is horizontal propagation light. belongs to. (A) is a cross-sectional schematic diagram for demonstrating the model structure which performed the computer simulation of FIG. 6, (b) is a cross-sectional schematic diagram for demonstrating the anti-phase model structure. It is a cross-sectional schematic diagram for demonstrating the dimension of the model structure which performed the computer simulation of FIG. It is a figure which shows the result of computer simulation calculation of the light extraction efficiency (relative value) of the organic EL element (pitch: 1000 nm) of one Embodiment of this invention, (a) is vertical propagation light, (b) is horizontal propagation light. belongs to. (A) About the organic EL element of one Embodiment of this invention, the result obtained by the computer simulation of FDTD method about the intensity distribution of the magnetic field of the radiation light from a perpendicular | vertical dipole is shown, (b) shows " The result in the case of the configuration of “cathode unevenness only” is shown. (A) About the organic EL element of one Embodiment of this invention, the result obtained by the computer simulation of FDTD method about the intensity distribution of the magnetic field of the radiated light from a horizontal dipole is shown, (b) shows " The result in the case of the configuration of “cathode unevenness only” 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 characteristics easy to understand, there are cases where the characteristic portions are enlarged for convenience. The dimensional ratio of each component is not always the same as actual. 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. Furthermore, the organic EL element of the present invention may include a layer not described below within a range not impairing the effects of the present invention.
In the following description, the configuration using the reflective electrode as the cathode and the transparent electrode as the anode will be described. However, the present invention is not limited to this configuration, and the configuration in which the reflective electrode is used as the anode and the transparent electrode as the cathode is also applicable. In the following embodiments, a bottom emission type organic EL element is used, but a top emission type organic EL element can also be used.

(Organic EL device (first embodiment))
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 according to the first embodiment of the present invention includes an anode (transparent electrode) 2, an organic layer 3 including a light emitting layer made of an organic EL material, a cathode 4 (reflection electrode), on a substrate 1. In order. The cathode 4 has a plurality of radiation starting points 4a periodically arranged on the surface 4A on the organic layer side. The anode 2 includes a plurality of anode hole portions 2A (see FIG. 5A (e)) whose inner surface 2a is covered with a dielectric layer 7 having a refractive index lower than that of the anode 2. The organic layer 3 has a layered portion 3 a arranged between the anode 2 and the dielectric layer 7 and the cathode 4. The radiation starting point 4a is arranged at a position overlapping the anode hole 2A (see FIG. 5A (e)) in plan view.
The organic layer 3 further has a portion corresponding to the shape of the radiation starting point portion 4a (in the example of FIG. 1, a convex portion 3b). Of the organic layer 3, the portion (3b) corresponding to the shape of the radiation starting point 4a is convex if the radiation starting point 4a is concave as shown in FIG. 1, and the radiation starting point 4a is convex. If there is, it becomes concave.
The configuration shown in FIG. 1 is that of a bottom emission type organic EL element. In the case of a top emission type device, the substrate 1 is disposed on the side opposite to the organic layer 3 when viewed from the cathode 4.

The shape of the anode hole 2A is not particularly limited as long as it has an effect of refracting light toward the substrate on the inner surface thereof. From the viewpoint of refracting the guided mode light more vertically, a shape in which the bottom area on the cathode 4 side is larger than the bottom area on the substrate 1 side is preferable. From the viewpoint of taking out the light beam as shown by the arrow B1 (see FIG. 2) straight up to the substrate without being refracted, a shape in which the area on the substrate 1 side is larger than the bottom area on the cathode 4 side is preferable. From the viewpoint of strongly diffracting the guided mode light and taking it out with a smaller propagation distance, a shape having a surface area as large as possible is preferable.
In order not to increase the sheet resistance of the anode, the bottom areas on the substrate 1 side and the cathode 4 side should be small.

In the example shown in FIG. 1, the inner side surface 2 a of the anode hole 2 </ b> A is configured to be orthogonal to the substrate surface, but is not limited to this configuration. The angle of the inner side surface of the anode hole with respect to the substrate surface is preferably 45 ° or more, more preferably 60 ° or more, and even more preferably 75 ° or more. By setting the inner side surface 2a of the anode hole portion 2A to such an angle, the guided mode light directed from the light emitting position toward the anode side and the guided mode light re-radiated from the SPP mode light are reflected on the inner side surface of the anode hole portion 2A. 2a is incident from the outside, refracted toward the substrate side, and taken out from the outer surface of the substrate.

1 is a bottom emission type organic EL element that extracts light emitted from the light emitting layer from the substrate side. Therefore, the substrate 1 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. A smooth substrate having a transmittance in visible light of 400 to 700 nm of 50% or more is preferable.

Specifically, a glass plate, a polymer plate, etc. are mentioned. Examples of the glass plate include soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyether sulfide, and polysulfone.
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 light emission 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 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 1 is not limited because it depends on the required mechanical strength. The thickness is preferably 0.01 mm to 10 mm, more preferably 0.05 mm to 2 mm.

The anode 2 has a plurality of anode hole portions 2A (see FIG. 5A (e)). The inner side surface 2a of the anode hole 2A is covered with a dielectric layer 7 having a refractive index lower than that of the anode 2. As long as the dielectric layer 7 covers the inner surface 2a, the dielectric layer 7 may be configured to fill the anode hole 2A or may be configured to partially fill.

The anode 2 is an electrode for applying a voltage to the cathode 4 and injecting holes from the anode 2 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 one 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 in contact with the anode does not become excessive.

The material of the anode 2 is not particularly limited as long as it is a translucent and conductive material. For example, transparent inorganic oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, zinc oxide, PEDOT: PSS (poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) In addition, a conductive polymer such as polyaniline and a conductive polymer doped with an arbitrary acceptor, and a transparent carbon material such as carbon nanotube, graphene, etc. Here, the anode 2 is formed on the substrate 1 by sputtering, for example. It can be formed by a method such as a vacuum evaporation method (resistance heating evaporation method or electron beam evaporation method), a CVD method, an ion plating method, or a coating method.

The thickness of the anode 2 is not limited, but is, for example, 10 to 2000 nm, preferably 50 to 1000 nm. If the thickness of the anode 2 is less than 10 nm, it is difficult to increase the volume of the dielectric layer 7 and the waveguide mode light is hardly scattered. This is because when the thickness of the anode 2 is greater than 2000 nm, the flatness of the organic layer 3 cannot be maintained and the transmittance of the anode is lowered.

The dielectric layer 7 covers the inner side surface 2 a of the anode hole 2 A of the anode 2 and is made of a material having a refractive index lower than that of the anode 2.
The configuration and material of the dielectric layer 7 is such that light incident on the inner surface 2a of the anode hole 2A from the anode 2 side toward the dielectric layer 7 is refracted toward the substrate 1 side at this interface, This is because by changing the incident angle into the substrate to a small angle, the ratio of light causing total reflection is reduced, and the light extraction efficiency is improved.

The material of the dielectric layer 7 is not particularly limited as long as it is a light-transmitting material and has a refractive index lower than that of the anode. When the material of the anode 2 is indium tin oxide (ITO (refractive index 1.82)), for example, spin-on glass (SOG (refractive index 1.25)), magnesium fluoride (MgF ₂ (refractive index 1.38). )), Metal fluorides such as polytetrafluoroethylene (PTFE (refractive index 1.35)), silicon dioxide (SiO ₂ (refractive index 1.45)), various low melting glass, various Examples include porous substances.
The thickness of the dielectric layer 7 is not limited, but is, for example, 10 to 2000 nm, and preferably 50 to 1000 nm. When the thickness of the dielectric layer 7 is less than 10 nm, the volume of the dielectric layer 7 with respect to the organic layer becomes small, and the guided mode light is hardly generated. If the thickness of the dielectric layer 7 is greater than 2000 nm, it is difficult to maintain the flatness of the organic layer 3.

The cathode 4 has a plurality of radiation starting points 4a periodically arranged on the surface 4A on the organic layer side. The radiation starting point portion 4a is preferably arranged at a position overlapping the anode hole portion 2A in plan view.

The cathode 4 is an electrode for injecting electrons 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 low work function. It is preferable to use a work function of 1.9 eV or more and 5 eV or less so that the difference from the LUMO (LowestLowUnoccupied Molecular Orbital) level does not become excessive. Examples of such materials include simple substances such as Au, Ag, Cu, Zn, Al, Mg, alkali metals and alkaline earth metals, alloys of Au and Ag, alloys of Ag and Cu, and alloys such as brass. It is done. The cathode 4 may have a laminated structure of two or more layers.

The thickness of the cathode 4 (thickness including the radiation starting point portion 4a) is not limited, but is, for example, 30 nm to 1 μm, and preferably 50 to 500 nm. If the thickness of the cathode 4 is less than 30 nm, the sheet resistance increases and the driving voltage rises. If the thickness of the cathode 4 is greater than 1 μm, heat and radiation damage during film formation and mechanical damage due to film stress accumulate in the electrode and the organic layer.

The radiation starting point portion 4a has a concave shape, but is not limited thereto, and may be a convex shape or an uneven shape. Each shape of the radiation starting point portion 4a when viewed in a plan view may be any of a line-shaped unevenness, a dot-shaped unevenness (unevenness that is discretely arranged), and the like.
One radiation starting point portion 4a (unit structure of the radiation starting point portion) may be composed of one concavo-convex structure or a plurality of concavo-convex structures. One radiation starting point portion is preferably smaller than the size of the anode hole portion in plan view.

The distance (pitch) between the central axes orthogonal to the substrates of the adjacent radiation starting point portions 4a is preferably 10 μm or less in which the SPP mode light can propagate. By setting such a pitch, before the SPP mode light is dissipated as heat, the SPP mode light can be scattered by the radiation starting point portion 4a and re-radiated as propagating light.
The radiation starting point portion 4a is disposed at a position overlapping the anode hole portion 2A in plan view. However, it is not necessary for all the anode hole portions 2A to have the radiation starting point portions 4a at the overlapping positions in plan view. That is, you may have 2 A of anode holes which do not have the corresponding radiation origin part 4a.
It is preferable that the pitch of the adjacent radiation starting point portions 4a is the same as the distance (pitch) between the central axes orthogonal to the substrate of the adjacent anode hole portions 2A arranged at positions where they overlap each other. Furthermore, it is more preferable that the central axis of the radiation starting point portion 4a arranged at the overlapping position and the central axis of the anode hole portion 2A coincide.

The organic layer 3 includes a layered portion 3a disposed between the anode 2 and the dielectric layer 7 and the cathode 4, and a portion corresponding to the shape of the radiation starting point portion 4a (in the example of FIG. 1, a protruding portion 3b). It is what you have.

As a material of the light emitting layer, any material known as a material for an organic EL element can be used.
The organic layer 3 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 (organic light emitting layer) made of an organic EL material.

The hole injection layer is a layer that assists hole injection from the anode 2 to the organic layer 3. Such a hole injection layer is preferably a material that injects holes into the light emitting layer with lower electric field strength. The material for forming the hole injection layer is not particularly limited as long as it can perform the above functions, and any material can be selected from known materials. The hole transport layer is a layer that transports holes to the light emitting region, and has a high hole mobility and a small ionization energy of usually 5.5 eV or less. The material to be formed as such a hole transport layer is not particularly limited as long as it has the above function, 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 4 to the organic layer 3. Such an electron injection layer is preferably a material that injects electrons into the organic layer 3 with lower electric field strength. 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 function, and any material can be selected and used from known materials.

The organic layer 3 may be formed by a dry process such as an evaporation method or a transfer method, or may be formed by a wet process such as a spin coating method, a spray coating method, a die coating method, or a gravure printing method.
The thickness of the organic layer 3 is not limited, but is, for example, 50 to 2000 nm, and preferably 100 to 1000 nm. If the thickness of the organic layer 3 is less than 50 nm, quenching other than SPP coupling by metal, such as reduction of internal QE due to punch-through current or lossy surface coupling, occurs. When the thickness of the organic layer 3 is greater than 1000 nm, the drive voltage increases.

Next, the function and effect of the organic EL element of this embodiment will be schematically described with reference to FIG. The light propagation method indicated by the arrows in FIG. 2 is schematically shown in order to easily understand the principle of the effect.

A part of the light emitted from the point A of the light emitting layer included in the organic layer 3 is captured by the surface 4A of the cathode 4 via the near field around the light emitting point (arrow A1), and becomes SPP mode light. Such energy transfer to the SPP mode is widely known to occur when a light emitting molecule and a metal layer are close to each other in a general organic EL element. The SPP mode light moves along the surface 4A of the cathode 4 (arrow A2) and is scattered by the radiation starting point portion 4a1 (4a). The trapped SPP mode light is re-emitted as propagating light into the organic layer 3, passes through the dielectric layer 17 and the like, and becomes substrate mode light (arrows B1, B2, B3), and is taken out of the substrate. It is.
Here, since the light emitted from the point A of the organic layer 3 travels in all directions, there is naturally light traveling in a direction other than the arrow A1 (for example, the anode side). The arrow A1 merely schematically shows the propagation of part of the light in order to explain the effects of the present invention. The light indicated by the arrow A2 and the arrows B1 to B3 is only schematically showing the propagation of part of the light.

Of the light radiated from the radiation starting point 4a1 (4a) and propagating in the directions indicated by the arrows B1 to B3, the light B1 travels to the substrate side perpendicular to the substrate, and the organic layer 3 and the dielectric layer 7, without being refracted at the interface with the dielectric layer 7 and the interface between the dielectric layer 7 and the substrate 1.

The light B 2 is refracted at the interface between the organic layer 3 and the anode 2, enters the anode 2, and passes through the anode 2. The transmitted light is refracted at the interface between the anode 2 and the dielectric layer 7 (the inner surface 2a of the anode hole 2A), refracted at the interface between the anode 2 and the substrate 1, and then passes through the substrate 1. Can be taken out to the outside.
Here, when the light B2 travels from the anode 2 to the dielectric layer 7, the angle of incidence on the substrate 1 is small due to refraction at the interface between the dielectric layer 7 and the anode 2 (the inner surface 2a of the anode hole 2A). Changes to.
In general, when the light is incident at an angle greater than the critical angle at the interface between the substrate (eg, glass) and air, total reflection occurs. However, since the incident angle on the substrate 1 is changed to a small angle due to refraction at the inner side surface 2a, light that can avoid total reflection at the interface between the substrate and air is increased, and light extraction efficiency is improved. That is, the light extraction efficiency is improved by having the configuration including the inner side surface 2a of the anode hole portion 2A.
Similarly to the light B2, the light B3 is also refracted to an angle at which the incident angle to the substrate 1 is small at the interface between the dielectric layer 7 and the anode 2 (the inner surface 2a of the anode hole 2A). By this refraction, the light that can avoid total reflection at the interface between the substrate and air increases, and the light extraction efficiency is improved.

As described above, in the organic EL device of the present invention, even if the light emitted from the light emitting layer included in the organic layer is captured as SPP mode light on the cathode surface, the SPP mode light is emitted at the radiation starting point on the cathode surface. Can be taken out. Furthermore, the light extracted from the cathode surface is refracted in the front direction of the substrate at the interface between the dielectric layer and the anode (the inner surface of the anode hole) to increase the amount of light extracted in the front direction of the substrate. Can do.

(Image display device)
Next, an image display apparatus provided with the organic EL element 10 will be described.
FIG. 3 is a diagram illustrating an example of an image display device including the organic EL element.
The image display device 100 shown in FIG. 3 is a so-called passive matrix 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 1 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 for example, ITO (Indium Tin Oxide) can be used. The thickness of the anode wiring 104 can be set to 100 nm 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 side of the substrate 1. As a result, a current can be supplied to the anode wiring 104 via the anode auxiliary wiring 106 from a drive circuit (not shown) provided outside. The anode auxiliary wiring 106 is made of a metal film having a thickness of 500 nm 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. For the cathode wiring 108, Al or an Al alloy can be used. The thickness of the cathode wiring 108 is, for example, 100 nm 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 1 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 the opening 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 set to, for example, 200 nm to 100 nm. 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 2 of the organic EL element 10 is in contact with the anode wiring 104 and the cathode 4 is in contact with the cathode wiring 108. The thickness of the organic EL element 10 can be set to, for example, 150 nm to 200 nm.

A plurality of cathode partition walls 112 are formed on the insulating film 110 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, the one having a height of 2 μm to 3 μm and a width of 10 μm can be used.

The substrate 1 is bonded through a sealing plate 116 and a sealing material 118. 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 mm to 1.1 mm can be used.

In the image display device 100 having such a structure, a current can be supplied to the organic EL element 10 via 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 1 through the substrate 1. An 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, a lighting device using the organic EL element 10 will be described.
FIG. 4 is a diagram illustrating an example of an illumination device including the organic EL element 10 described above.
The lighting apparatus 200 shown in FIG. 4 includes the organic EL element 10 described above, and a terminal 202 that is installed adjacent to the substrate 1 (see FIG. 1) of the organic EL element 10 and connected to the anode 2 (see FIG. 1). The terminal 203 is connected to the cathode 4 (see FIG. 1), and the lighting circuit 201 is connected to the terminal 202 and the terminal 203 to drive the organic EL element 10.

The lighting circuit 201 has a DC power supply (not shown) and a control circuit (not shown) inside, and supplies a current between the anode layer 2 and the cathode 4 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, light is emitted from the substrate 1 through the support substrate 101, and is 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.

(Manufacturing method of organic EL element)
Next, the manufacturing method of the organic EL element which is one Embodiment of this invention is demonstrated with reference to FIG. 5A and FIG. 5B.
First, as shown in FIG. 5A (a), an anode 2 is formed on a substrate 1. A method for forming the anode 2 is not particularly limited, and for example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.

By performing the surface treatment of the anode 2 after forming the anode 2, the performance of the overcoated layer (adhesion with the anode 2, surface smoothness, reduction of hole injection barrier, etc.) can be improved. . The surface treatment includes high-frequency plasma treatment, sputtering treatment, corona treatment, UV ozone irradiation treatment, ultraviolet irradiation treatment, oxygen plasma treatment, and the like.

Furthermore, the same effect as the surface treatment can be expected by forming an anode buffer layer (not shown) instead of or in addition to the surface treatment of the surface treatment of the anode 2. When the anode buffer layer is applied by a wet process, spin coating, casting, micro gravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating The film can be formed using a coating method such as a spray method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, or an inkjet printing method.

When the anode buffer layer is produced by a dry process, the anode buffer layer can be formed by using a plasma treatment or the like exemplified in Japanese Patent Application Laid-Open No. 2006-303412. In addition, a method of forming a film of a single metal, a metal oxide, a metal nitride, or the like can be given. As a specific film formation method, an electron beam evaporation method, a sputtering method, a chemical reaction method, a coating method, a vacuum evaporation method, or the like can be used.

Next, for example, a method using photolithography can be used to form the anode hole 2A. In order to do this, as shown in FIG. 5A (b), first, a positive resist solution is applied onto the anode 2 and the excess resist solution is removed by spin coating or the like to form a resist layer 9.

Then, when a mask (not shown) on which a predetermined pattern for forming the anode hole 2A is drawn is applied and exposure is performed with ultraviolet rays (UV), electron beams (EB), etc., FIG. 5A (c) is obtained. As shown, a predetermined pattern corresponding to the anode hole 2A is exposed on the resist layer 9 (exposed portion 9a). Then, the resist layer 9a in the exposed pattern portion is removed using a developer. As a result, the surface of the anode 2 is exposed corresponding to the exposed pattern portion (FIG. 5A (d)).

As shown in FIG. 5A (e), a part of the exposed anode 2 is removed by etching using the remaining resist layer 9 as a mask to form an anode hole 2A. As an etching method, either dry etching or wet etching can be used. At this time, the shape of the anode hole portion 2A can be controlled by combining isotropic etching and anisotropic etching. As the dry etching, reactive ion etching (RIE: Reactive Ion Etching) using inductively coupled plasma or capacitively coupled plasma can be used. As the wet etching, a solution of a metal salt such as an iron chloride aqueous solution or a method of immersing in an acid such as dilute hydrochloric acid or dilute sulfuric acid can be used. By this etching, the surface of the substrate 1 is exposed corresponding to the pattern.

Next, as shown in FIG. 5A (f), the dielectric layer 7 is formed using the remaining resist layer 9 as a mask. In FIG. 5A (f), the dielectric layer 7 fills the anode hole 2A and covers the inner side surface 2a of the anode hole 2A, but only partially fills the inner side surface 2a of the anode hole 2A. The structure to do may be sufficient. The formation of the dielectric layer 7 is not limited in the same manner as the formation of the anode 2, but for example, resistance heating vapor deposition, electron beam vapor deposition, sputtering, ion plating, CVD, various coating methods, etc. Can be used.

Next, after removing the resist layer 9, as shown in FIG. 5B (g), an organic layer 3 including a light emitting layer made of an organic EL material is formed on the anode 2 and the dielectric layer. Here, in the case where the surfaces of the anode 2 and the dielectric layer 7 serving as the foundation on which the organic layer 3 is formed are uneven, polishing or etching for flattening may be appropriately performed.
For forming the organic layer 3, a conventionally known method can be used and is not limited. For example, a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method can be used.

Next, a concavo-convex structure is formed on the surface of the organic layer 3 so as to have a convex portion 3b at a position corresponding to the radiation starting point portion 4a of the cathode 4 to be formed later. For example, a method using photolithography can be used for forming the unevenness. In order to do this, as shown in FIG. 5B (g), first, a positive resist solution is applied onto the organic layer 3, and the excess resist solution is removed by spin coating or the like to form a resist layer 11. .

Then, when a mask (not shown) on which a predetermined pattern for forming the convex portion 3b is drawn is applied and exposure is performed with ultraviolet rays (UV), electron beams (EB), etc., it is shown in FIG. 5B (h). As described above, the resist layer 11 is exposed with a predetermined pattern corresponding to the radiation starting point portion 4a (exposed portion 11a). Then, the resist layer 11a in the exposed pattern portion is removed using a developer. Thus, the surface of the organic layer 3 is exposed corresponding to the exposed pattern portion (FIG. 5B (i)).

Next, as shown in FIG. 5B (j), using the remaining resist layer 11 as a mask, a portion of the exposed organic layer 3 is removed by etching to form a convex portion 3b. As the etching, either dry etching or wet etching can be used. At this time, the shape of the convex portion 3b can be controlled by combining isotropic etching and anisotropic etching. As dry etching, reactive ion etching (RIE), ashing treatment using oxygen plasma, or the like can be used. As the wet etching, there can be used a method of immersing in various organic solvents in addition to dilute hydrochloric acid and dilute sulfuric acid. By this etching, a concavo-convex structure including the convex portions 3 b corresponding to the radiation starting point portions 4 a can be formed on the surface of the organic layer 3 corresponding to the pattern.
Since photolithography has alignment accuracy up to about 1 μm, it is possible to form the cathode radiation starting point portion 4a and the anode hole portion 2A so as to overlap in a plan view.

Next, as shown in FIG. 5B (k), a cathode material is vapor-deposited on the organic layer 3, and the cathode 4 having the radiation starting point portion 4a is formed by following the uneven structure of the organic layer 3.

The organic EL element 10 can be manufactured by the above process. After these series of steps, it is preferable to use the organic EL element 10 stably for a long period of time and to attach a protective layer and a protective cover (not shown) for protecting the organic EL element 10 from the outside. As the protective layer, polymer compounds, metal oxides, metal fluorides, metal borides, silicon compounds such as silicon nitride and silicon oxide, and the like can be used. And these laminated bodies can also be used. As the protective cover, a glass plate, a plastic plate whose surface is subjected to low water permeability treatment, a metal, or the like can be used. The protective cover is preferably bonded to the substrate 1 with a thermosetting resin, a photocurable resin, frit glass or the like and sealed. At this time, it is preferable to place a spacer between the substrate 1 and the protective cover because a predetermined space can be maintained and the organic EL element 10 can be prevented from being damaged.
If an inert gas such as nitrogen, argon or helium is sealed in this space, it becomes easy to prevent oxidation of the upper cathode 4. In particular, when helium is used, heat conduction is high, and thus heat generated from the organic EL element 10 when voltage is applied can be effectively transmitted to the protective cover, which is preferable. Furthermore, by installing a desiccant such as barium oxide in this space, it becomes easy to suppress the moisture adsorbed in the series of manufacturing steps from damaging the organic EL element 10.

In the above method for producing an organic EL element, the method for producing from the anode side has been described. However, in the case of a top emission type organic EL element, it may be produced from the cathode side.

Examples of the organic EL device of the present invention will be described below.

6 (a) and 6 (b) show the total radiant intensity using a finite difference time domain (FDTD) method in order to confirm the effect of the organic EL device of one embodiment of the present invention. The result of computer simulation calculation is shown by using the radiation intensity of light into the substrate as the light extraction efficiency. The FDTD method is an analysis method for differentiating Maxwell's equation describing a time change of an electromagnetic field spatially and temporally and tracking the time change of the electromagnetic field at each point in the space. 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 simulation result shows the result of calculating the light extraction efficiency with respect to the light extracted up to the substrate.
In this embodiment, a simulation of a bottom emission type organic EL element is performed, but the top emission type organic EL element also differs only in the direction of light extraction, and exhibits the effects of the present invention.

6 (a) and 6 (b) respectively show the light extraction efficiency of the radiated light from the dipole vibrating in the horizontal direction (light propagating in the direction perpendicular to the substrate (hereinafter also referred to as vertical propagation light)), The light extraction efficiency calculation result of the radiated light from the dipole vibrating in the vertical direction (light propagating in a direction parallel to the substrate (hereinafter sometimes referred to as horizontal propagation light)) is shown.

“In-phase” in the graphs shown in FIGS. 6A and 6B is an example of the present invention. As shown in FIG. 7 (a), in the case of the present invention in which the radiation starting point of the cathode and the anode hole (or dielectric layer) overlap in plan view, in particular, the radiation starting point of the cathode This is a case where the central axis C1 orthogonal to the substrate coincides with the central axis C2 orthogonal to the substrate of the anode hole portion.

As shown in FIG. 7B, the “reverse phase” is a case where the radiation starting point portion of the cathode and the anode hole portion (or dielectric layer) do not overlap each other in plan view. This is a case where the center axis C1 of the radiation starting point portion and the center axis C2 of the anode hole portion are shifted by a half cycle, and is shown as a comparative example of the present invention.

The “cathode unevenness +“ in-phase ”” according to the graphs shown in FIGS. 6A and 6B means that the cathode emission starting portion and the anode hole portion have the above-described arrangement, and the cathode has a radiation starting portion. The structure which has a recessed part of the shape mentioned later as follows.
Further, “cathode unevenness +“ reverse phase ”” according to the graphs shown in FIGS. 6A and 6B is that the emission starting point portion and the anode hole portion of the cathode have the above-described arrangement and are emitted to the cathode. The structure which has a recessed part of the shape mentioned later as a starting point part is meant.

The “cathode unevenness only” according to the graphs shown in FIGS. 6A and 6B is “cathode unevenness +“ in phase ”” except that the anode is a layered anode having no anode hole. It means the same structure as “cathode unevenness +“ reverse phase ”.” That is, the structure of the cathode (reflection electrode side structure) is the same as that of the present invention, but the structure of the anode (transparent electrode side structure) The configuration is different from that of the present invention.

The “standard” according to the graphs shown in FIGS. 6A and 6B is a layered anode in which the anode does not have an anode hole, and a cathode in which the cathode does not have a radiation starting point. Otherwise, it means the same structure as “cathode unevenness +“ in-phase ”” and “cathode unevenness +“ reverse phase ”.” That is, the structure of the cathode (reflection electrode side structure) and the structure of the anode (transparent electrode) The side structure is different from the present invention.

7A and 7B are cross-sectional views showing a model structure of the organic EL element of the embodiment used in the simulation.
The substrate 1 is made of glass, and a refractive index of 1.5 is used. The anode 2 is made of ITO, the refractive index is 1.82 + 0.009i at 550 nm, and other wavelengths are extrapolated by the Lorentz model. The dielectric layer 7 is made of SOG, and the refractive index is 1.25. As the refractive index of the organic layer 3, 1.72 was used. The cathode 4 is made of aluminum (Al), the refractive index is 0.958 + 6.69i at 550 nm, and the other wavelengths are extrapolated by the Drude model. Thereafter, unless otherwise noted, the above values are used for the refractive indexes of glass, organic layer, and aluminum, respectively.

FIG. 8 shows the shape and size of each configuration, taking the configuration of FIG. 7A as an example.
The layer thicknesses of the anode 2 (or dielectric layer 7), the layered portion 3a of the organic layer 3, and the cathode 4 were 150 nm, 100 nm, and 200 nm, respectively.
The distance (pitch) between the central axes of the adjacent radiation starting point portions 4a was 500 nm, the depth of the concave portion forming the radiation starting point portion 4a was 100 nm, and the width was 60 nm.
The distance (pitch) between the central axes of the adjacent anode hole portions 2A was set to 500 nm, similar to the pitch of the radiation starting point portions 4a of the cathode 4. The width of the anode hole 2A was set to ½ (250 nm) of the pitch. Here, the radiation starting point portion 4a and the anode hole portion 2A have a translational symmetric structure in the depth direction of the drawing. That is, in a plan view, the convex portion and the hole have a line shape extending infinitely in one direction in the plane. However, the light source is not translationally symmetric in the depth direction of the paper, but is placed in the form of dots in the organic layer layered region.

As shown in FIG. 6A, in the case of the configuration of “cathode unevenness +“ in phase ””, which is an embodiment of the present invention, the “standard” configuration, the “cathode unevenness only” configuration, As compared with the case of the configuration of “cathode unevenness +“ reverse phase ””, high light extraction efficiency was obtained over the entire calculated range of 450 nm to 750 nm, particularly 450 nm to 650 nm. In this range, a light extraction efficiency as high as 10% or more was obtained.
In the case of the “cathode unevenness +“ reverse phase ”” configuration, the light extraction efficiency was lower than in the “standard” configuration and “cathode unevenness only”.

From this result, it can be seen that the relative positional relationship between the radiation starting point 4a of the cathode and the anode hole 2A greatly affects the light extraction efficiency of the vertical propagation light. By combining the relative positions of the cathode radiation start point and anode hole part in the same phase, a higher light extraction efficiency than the conventional “standard” configuration and “cathode unevenness only” configuration can be obtained. It is done. Even if it is a combination of the cathode radiation origin portion and the anode hole portion, when the relative positions of the cathode radiation origin portion and the anode hole portion are combined in “reverse phase”, the conventional “standard” configuration, and The light extraction efficiency is lower than the “cathode unevenness only” configuration. Therefore, it can be seen that it is preferable to combine the radiation starting point of the cathode with the radiation starting point of the cathode by setting the relative position of the anode starting hole and the anode hole to the same phase.
These are theoretically difficult to predict and can only be known after simulation.

構成 “Cathode unevenness only” configuration has almost the same light extraction efficiency as “Standard” configuration. This is because, even if the SPP mode light captured on the cathode surface is re-emitted into the organic layer by the radiation origin provided on the cathode surface in the “cathode unevenness only” configuration, the re-emitted light is extracted. When the anode side structure is not provided, the re-emitted light is confined in the element as guided mode light, which means that the light extraction efficiency to the substrate cannot be improved.

Next, as shown in FIG. 6B, in the case of the configuration of “cathode unevenness +“ in phase ”” which is an embodiment of the present invention, the “standard” configuration and the “cathode unevenness” Only in the “configuration”, high light extraction efficiency was obtained over the entire calculated range of 450 nm to 750 nm. In particular, the light extraction efficiency was several times higher than that in the standard configuration. Efficiency was obtained. Compared with the “cathode concavity and convexity only” configuration, higher light extraction efficiency was obtained at 450 nm to 580 nm and 670 nm to 750 nm. The light extraction efficiency was slightly lower in the range of 450 nm to 500 nm, but the light extraction efficiency was higher in the other wavelength ranges as compared with the case of the cathode irregularity + “reverse phase” configuration.
Also for horizontal propagation light, the “cathode unevenness +“ in-phase ”” configuration is more than the “standard” configuration, “cathode unevenness only” configuration, and “cathode unevenness +“ reverse phase ”” configuration. It turns out that it is effective for the improvement of efficiency.
These are theoretically difficult to predict and can only be known after simulation.

FIGS. 9A and 9B show the model structure of the organic EL element having the same configuration as that of FIGS. 7 and 8, except that the pitch of the radiation starting point of the cathode and the pitch of the anode hole are set to 1000 nm. FIG. 7 shows a result of simulation calculation similar to that shown in FIG. 6. FIG.

As shown in FIG. 9 (a), in the case of the configuration of “cathode unevenness +“ in phase ””, the “standard” configuration for the vertical propagation light, as in the case where the pitch shown in FIG. 6 (a) is 500 nm. Higher light extraction efficiency was obtained over the entire calculated range of 450 nm to 750 nm than in the case of the “cathode unevenness only” configuration and the cathode unevenness + “reverse phase”. In the range of 500 nm to 620 nm, a light extraction efficiency as high as 10% or more was obtained.
In the case of “cathode unevenness +“ reverse phase ””, light extraction efficiency comparable to that of the “standard” configuration in the range of 450 nm to 560 nm and “cathode unevenness only” was obtained. However, the light extraction efficiency was lower in the range of 560 nm to 750 nm than in the cases of the “standard” configuration and “cathode unevenness only”.
These are theoretically difficult to predict and can only be known after simulation.

Even when the pitch is 1000 nm, the “cathode unevenness only” configuration has almost the same light extraction efficiency as the “standard” configuration. This is because even if the “cathode concavity and convexity only” configuration can extract SPP mode light captured on the cathode surface to obtain guided mode light, it does not have a configuration for extracting the guided mode light. This means that the light extraction efficiency to the substrate cannot be improved.

Further, as shown in FIG. 9B, for the horizontal propagation light, the “cathode unevenness +“ in-phase ”” configuration is more than the “standard” configuration and the “cathode unevenness only” configuration. A high light extraction efficiency was obtained over the entire calculated range of 450 nm to 750 nm. In particular, the difference from the standard “configuration” was larger than when the pitch was 500 nm. Compared with the configuration of “cathode unevenness +“ reverse phase ””, the light extraction efficiency was slightly low in the range of 450 nm to 510 nm, but the light extraction efficiency was high in other wavelength ranges.
Also for horizontal propagation light, the “cathode unevenness +“ in-phase ”” configuration is more than the “standard” configuration, “cathode unevenness only” configuration, and “cathode unevenness +“ reverse phase ”” configuration. It turns out that it is effective for the improvement of efficiency.
These are theoretically difficult to predict and can only be known after simulation.

FIG. 10A shows a configuration of “cathode unevenness +“ in phase ”” and a pitch of 500 nm (model structure shown in FIG. 7 and FIG. 8). ) Shows the simulation result of the intensity distribution of the magnetic field by the FDTD method, and the wavelength of the emitted light is 620 nm.
The intensity distribution is shown with the substrate on the top and the cathode on the bottom. In the figure, the horizontally extending line is a horizontal interface between the layers, while the line extending perpendicularly indicates the inner surface. A concave portion disposed at a position facing the anode hole portion indicates a radiation starting point portion of the cathode. The same applies to FIG.
FIG. 10B shows the result of simulation calculation corresponding to FIG. 10A for the “cathode concavity and convexity only” configuration.

When comparing the intensity distribution of FIG. 10 (a) with the intensity distribution of FIG. 10 (b), it can be seen that the horizontal propagation light is vertical. This indicates that light extraction toward the substrate is large. It can be seen that the SPP mode light is converted into radiated light (guided mode light) in the concave portion which is the radiation starting point.

FIG. 11A shows the result of simulation calculation by the FDTD method of the intensity distribution of the magnetic field of the radiation light (vertical propagation light) from the horizontal dipole for the same configuration as FIG. The wavelength of the emitted light was 550 nm.
FIG. 11B shows a simulation calculation result corresponding to FIG. 11A for the “cathode unevenness only” configuration.

In the intensity distribution of FIG. 11B, the guided mode light remains over the entire range showing the results, whereas in the intensity distribution of FIG. You can see that it has been taken out. This can be understood as an effect of the anode side structure of the present invention.
As a result, even if the SPP mode light captured on the cathode surface by the cathode unevenness can be extracted to be a guided mode light, if the configuration for extracting the guided mode light is not provided, This means that the light extraction efficiency to the substrate cannot be improved.
These are theoretically difficult to predict and can only be known after simulation.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Anode (transparent electrode) 2a Inner side surface 2A Anode hole part (hole part) 3 Organic layer 4 Cathode (reflective electrode) 4a Radiation origin part 7 Dielectric layer 9 Resist layer 10 Organic EL element 11 Resist layer 100 Image display apparatus 200 Lighting device

Claims (6)

1. A transparent electrode, an organic layer including a light emitting layer made of an organic EL material, and a reflective electrode are provided in this order, and the reflective electrode has a plurality of radiation starting points arranged periodically on the surface of the organic layer. And
   The transparent electrode includes a plurality of holes whose inner surfaces are covered with a dielectric layer having a refractive index lower than that of the transparent electrode, and the organic layer includes the transparent electrode, the dielectric layer, and the It has a layered portion arranged between the reflective electrode,
   The radiation starting point portion is disposed at a position overlapping the hole portion in plan view.
2. Having a substrate on the surface of the transparent electrode opposite to the organic layer;
   It is configured to extract light from the transparent electrode side to the outside,
   2. The organic EL device according to claim 1, wherein the transparent electrode is an anode and the reflective electrode is a cathode.
3. 3. The organic EL element according to claim 1, wherein the hole portion and the radiation starting point portion have respective center axes orthogonal to the substrate.
4. The organic EL element according to any one of claims 1 to 3, wherein the radiation starting point is a recess.
5. An image display device comprising the organic EL element according to any one of claims 1 to 4.
6. An illumination device comprising the organic EL element according to any one of claims 1 to 4.

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