WO2014069564A1

WO2014069564A1 - Organic el element, and image display device and lighting device each of which is provided with same

Info

Publication number: WO2014069564A1
Application number: PCT/JP2013/079534
Authority: WO
Inventors: 祥貴下平; 祐介山▲崎▼
Original assignee: 昭和電工株式会社
Priority date: 2012-10-31
Filing date: 2013-10-31
Publication date: 2014-05-08

Abstract

This organic EL element is obtained by sequentially forming, on a substrate, a dielectric layer, a first electrode, an organic layer containing a light emitting layer, and a second electrode; and this organic EL element is configured such that light is extracted from the first electrode side to the outside. This organic EL element is characterized in that: a low refractive index layer and a metal layer are additionally and sequentially provided on a side of the second electrode, said side being on the reverse side of the organic layer side of the second electrode; the second electrode is formed of a transparent conductive material; the refractive index of the low refractive index layer is lower than the refractive index of the organic layer; the dielectric layer is formed of a pattern that has a refractive index lower than the refractive index of the first electrode and has an opening so that the substrate is exposed therefrom; and the first electrode, the organic layer, the second electrode, the low refractive index layer and the metal layer are formed so as to follow the pattern of the dielectric layer.

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. 2012-241337 filed in Japan on October 31, 2012 and Japanese Patent Application No. 2013-148022 filed in Japan on July 16, 2013 And the contents thereof are incorporated herein.

Organic EL elements have features such as a wide viewing angle, high-speed response, clear self-luminous display, etc., and they are thin, lightweight, and have low power consumption. It is expected as a pillar of
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. .

For example, consider a bottom emission type organic EL device having a transparent electrode, an organic layer including a light emitting layer, and a metal electrode in this order on a transparent substrate. In such an organic EL element, the light emitted from the light emitting layer is critical at the interface between a transparent substrate (for example, glass (typical refractive index: 1.52)) and air (refractive index: 1.0). Light incident at a small incident angle (angle formed by the incident ray and the normal of the incident 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.
In addition, among the light emitted from the light emitting layer, a transparent electrode (for example, indium tin oxide (ITO (typical refractive index: 1.82))) and a transparent substrate (for example, glass (typical) made of a transparent conductive oxide. Further, light incident on the interface with a refractive index of 1.52)) with an incident angle larger than the critical angle is totally reflected at the interface and is not taken out of the element, but can be finally absorbed by the material. Then, this light is called waveguide mode light, and the loss due to this is called waveguide loss.
In addition, the light emitted from the light emitting layer is incident on the metal electrode and combined with the free electrons of the metal electrode, and the light captured on the surface of the metal electrode as surface plasmon polariton (SPP) is also outside the device. And can be finally absorbed into 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, 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). It can be said that research has just begun on the reduction and removal of odors.

Since guided mode light is generated when total reflection occurs when light enters a low refractive index material from a high refractive index material, total reflection is less likely to occur in order to reduce guided mode light. There are known measures for reducing guided mode light by reducing the proportion of light that causes 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 lower refractive index than the organic light emitting layer and the transparent electrode in the organic light emitting layer and the transparent electrode. It is disclosed.

Patent Documents

4 and 5 disclose a configuration in which a cavity is provided in a transparent electrode 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. The light refracted to the substrate side can reduce the proportion of light that causes total reflection at the interface between the transparent electrode and the substrate and between the substrate and the air.

On the other hand, as a method for extracting the SPP mode light trapped on the surface of the metal electrode, a configuration in which a periodic uneven structure is formed on the surface of the metal electrode 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 as propagating light, the light extraction efficiency cannot be improved unless the light becomes guided mode light and can be extracted outside the device.

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

The present inventors first assume a two-step light extraction mechanism in which SPP mode light is extracted as propagating light into an organic layer, and then the propagating light is extracted outside the device without being converted into guided mode light. Thus, an effective structure for improving the light extraction efficiency has been intensively studied among a number of structures.
Since it is difficult to directly measure the light extraction efficiency, the investigation was mainly based on simulation.

The organic EL device of the present invention has a structure in which an organic layer including a light emitting layer is sandwiched between a first electrode and a second electrode. Here, the above-described two-step light extraction mechanism generates the SPP mode light, and the second electrode side structure of the Otto type arrangement (Non-Patent Document 1) that extracts the generated SPP mode light as the propagation light, and its propagation It consists of a first electrode side structure that takes out light without using it as guided mode light.

The inventors of the present invention have shown by simulation that a first electrode having an Otto-type arrangement of the second electrode side structure and an interface that is perpendicular or nearly perpendicular to the transparent substrate that refracts or directs guided mode light toward the transparent substrate. By combining with the electrode side structure, it has been found that the second electrode side structure and the first electrode side structure have a remarkable effect that cannot be predicted from the improvement effect of the single light extraction efficiency, and the present invention has been completed. It was.

In order to solve the above-mentioned problems, the present invention having the outline adopts the following configuration.
(1) A dielectric layer, an anode, an organic layer including a light emitting layer made of an organic EL material, and a cathode are sequentially formed on the substrate, and is configured to extract light from the anode side to the outside. The organic EL device further comprises a low refractive index layer and a metal layer in order on the opposite side of the cathode from the organic layer, wherein the cathode is made of a translucent conductive material, and the low refractive index. The refractive index of the refractive index layer is lower than the refractive index of the organic layer, and the dielectric layer has a refractive index lower than that of the anode and has a pattern having an opening so that the substrate is exposed. The organic EL element, wherein the anode, the organic layer, the cathode, the low refractive index layer, and the metal layer are formed so as to follow a pattern of the dielectric layer.
(2) An organic EL device comprising a dielectric layer, a first electrode, an organic layer including a light emitting layer, and a second electrode in this order, and further, the second electrode on the opposite side of the organic layer. On the surface, a low refractive index layer having a thickness of 20 nm or more and 300 nm or less and a metal layer in order, the second electrode is made of a translucent conductive material, and the refractive index of the low refractive index layer is The dielectric layer is lower than the refractive index of the organic layer, and the dielectric layer has a refractive index different from that of the first electrode and has a pattern having an opening, and the first electrode is formed of the dielectric layer. An organic EL element characterized by being formed so as to follow the pattern.
(3) An organic EL device comprising a dielectric layer, a first electrode, an organic layer including a light emitting layer, and a second electrode in this order, and further, the second electrode on the opposite side of the organic layer. On the surface, a low refractive index layer having a thickness of 20 nm or more and 300 nm or less and a metal layer in order, the second electrode is made of a translucent conductive material, and the refractive index of the low refractive index layer is The dielectric layer is lower than the refractive index of the organic layer, and the dielectric layer has a refractive index different from the refractive index of the first electrode and has a pattern having island-shaped dielectric island portions that are independent from each other in plan view. The organic EL element is characterized in that the first electrode is formed along the pattern of the dielectric layer.
(4) An organic EL device comprising a first electrode, an organic layer including a light emitting layer, and a second electrode on a substrate in order, and further, the second electrode on the opposite side of the organic layer. On the surface, a low refractive index layer having a thickness of 20 nm to 300 nm and a metal layer are provided in order, and the second electrode is made of a light-transmitting conductive material, and the refractive index of the low refractive index layer is the organic The substrate has a refractive index lower than the refractive index of the layer, and the substrate has a refractive index different from the refractive index of the first electrode, and is independent of each other in a substrate opening or a plan view on a surface on which the first electrode is formed. A pattern having island-shaped substrate island-shaped portions is formed, and the first electrode is formed along the pattern of the substrate.
(5) The organic EL element according to any one of (1) to (4), wherein a refractive index of the anode or the first electrode is different from that of the organic layer.
(6) The surface on the organic layer side of the anode or the first electrode is flattened by a flattening layer made of a conductor or a dielectric, and the organic layer is flat (1) to The organic EL device according to any one of (5).
(7) The organic EL element according to any one of (1) to (6), wherein a refractive index of the low refractive index layer is further lower than a refractive index of the cathode or the second electrode. .
(8) The organic EL element according to (7), wherein a refractive index of the cathode or the second electrode is lower than a refractive index of the organic layer.
(9) The low refractive index layer is made of a material having a refractive index smaller by 0.2 or more than at least one of the cathode or the second electrode and the organic layer. ). The organic EL element as described in any one of 1).
(10) The period in which the opening or the island-shaped portion and the substrate opening or the substrate island-shaped portion are arranged in at least one direction within the substrate surface is 200 to 2000 nm ( The organic EL device according to any one of 1) to (9).
(11) A real part ε ₁ of the dielectric constant of the metal layer, a dielectric constant ε ₂ of the low refractive index layer, and a period (p) in at least one direction of the pattern of the dielectric layer or the pattern of the substrate, The organic EL element according to any one of (1) to (9), wherein the organic EL element is selected so as to satisfy the following formula for a certain integer N (1 ≦ N ≦ 3):

Here, λ is the maximum peak wavelength of the photoluminescence spectrum of the light emitting layer.
(12) The organic EL element according to (11), wherein the period is 200 nm to 2000 nm.
(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 (13).

According to the present invention, it is possible to provide an organic EL element in which SPP mode light and waveguide mode light are effectively extracted to improve 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 1st Embodiment of this invention, (a) is an organic EL element whose refractive index of a dielectric material layer is higher than the refractive index of an anode, b) is an organic EL element in which the refractive index of the dielectric layer is lower than the refractive index of the anode. (A) is a perspective view for demonstrating an example of the organic EL element which concerns on 1st Embodiment of this invention, (b) is a perspective view of the organic EL element which reversed the uneven structure of the dielectric material layer. It is. In addition, in order to show the feature of the invention in an easy-to-understand manner, the portion of the Otto type arrangement structure is illustrated separately. It is a cross-sectional schematic diagram for demonstrating an example of the organic EL element which concerns on 2nd Embodiment of this invention. (A) is a perspective view for demonstrating an example of the organic EL element which concerns on 2nd Embodiment of this invention, (b) is a perspective view of the organic EL element which reversed the uneven structure of the board | substrate. . In addition, in order to show the feature of the invention in an easy-to-understand manner, the portion of the Otto type arrangement structure is illustrated separately. It is a cross-sectional schematic diagram for demonstrating an example of the organic EL element which concerns on 3rd Embodiment of this invention, (a) is a figure where the planarization layer has covered a part of anode surface, (b) is It is the figure which has covered the whole anode surface. It is a cross-sectional schematic diagram of the organic EL element provided with the 2nd electrode side structure which has Otto type | mold arrangement | positioning. It is a partial cross-sectional schematic diagram including the 1st electrode side structure of the organic EL element provided with the 1st electrode side structure provided with the transmissive | pervious diffraction grating. It is a cross-sectional schematic diagram for demonstrating the effect of the diffraction in the organic EL element which concerns on 1st Embodiment of this invention, (b) The cross-sectional schematic diagram for demonstrating the effect of a photonic crystal. 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 the manufacturing method of the organic EL element which concerns on 1st Embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the organic EL element which concerns on 2nd Embodiment of this invention. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the organic EL element which concerns on 3rd Embodiment of this invention. The result of having performed the energy dissipation calculation which expand | deploys the light light-emitted in the organic layer by the wave number in the organic EL element surface direction in the general organic EL element which has an anode, an organic layer, and a cathode (metal) on a board | substrate is shown. It is the figure which showed the dependence by the film thickness of a low-refractive-index layer of energy dissipation calculation in an Otto type | mold arrangement | positioning, the refractive index of a low-refractive-index layer shall be 1.38, (a) makes a metal layer Al, ( b) is a diagram showing the results when the metal layer is Ag. It is a cross-sectional schematic diagram of the organic EL element which concerns on one Embodiment of this invention for demonstrating the change of the peak in FIG. In the result of energy dissipation calculation in FIG. 15, it is the figure which showed the change of the peak width with respect to the film thickness of a low refractive index layer. In the organic EL element which concerns on one Embodiment of this invention, (a) is a figure which graphed Formula (16) at the time of making a metal layer into Al and (b) making a metal layer into Ag. It is a figure which shows the result of the computer simulation which investigated the period dependence about the light extraction efficiency of the organic EL element of the organic EL element which concerns on 1st Embodiment of this invention using a random dipole. It is a cross-sectional schematic diagram for demonstrating the structure of the organic EL element which performed the simulation of FIG. It is the figure which showed the intensity distribution of the electric field of the radiated light from the horizontal dipole obtained by FDTD method simulation, (a) has the 2nd electrode side structure of Otto type arrangement, and propagates propagation light In the case where the first electrode side structure extracted outside without using the mode light is not provided, (b) has the second electrode side structure of the Otto type arrangement, and the first electrode period (pitch) is 500 nm. c) has an Otto type second electrode side structure, and the first interelectrode period (pitch) is 900 nm. It is the figure which showed the intensity distribution of the magnetic field of the radiated light from the dipole of the perpendicular direction obtained by FDTD method simulation, (a) has the 2nd electrode side structure of Otto type arrangement, and propagates propagation light In the case where the first electrode side structure extracted outside without using the mode light is not provided, (b) has the second electrode side structure of the Otto type arrangement, and the first electrode period (pitch) is 500 nm. c) has an Otto type second electrode side structure, and the first interelectrode period (pitch) is 900 nm. It is the figure which showed the dependence by the period (pitch) between the 1st electrodes of the intensity distribution of the electric field of the emitted light from the horizontal dipole obtained by the FDTD method simulation, (a) is 200 nm, ( b) is 300 nm, (c) is 500 nm, (d) is 900 nm, (e) is 2000 nm, and (f) is 4000 nm. It is the figure which showed the dependence by the period (pitch) of the 1st electrode of the intensity distribution of the magnetic field of the radiated light from the dipole of the perpendicular direction obtained by FDTD method simulation, and the period (a) is 200 nm, ( b) is 300 nm, (c) is 500 nm, (d) is 900 nm, (e) is 2000 nm, and (f) is 4000 nm.

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 addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. . In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.
Any of the so-called bottom emission structure and top emission structure may be applied to the organic EL element of the present invention.
In the present invention, one of the first electrode and the second electrode is an anode and the other is a cathode. In the following description, a configuration in which the first electrode is an anode and the second electrode is a cathode will be described as an example.
Moreover, the organic EL element of this invention may be provided with the layer which is not described below in the range which does not impair the effect of this invention.

(Organic EL device)
1A and 1B are schematic cross-sectional views for explaining an example of an organic EL element according to the first embodiment of the present invention.
An organic EL element 10 shown in FIG. 1 includes a dielectric layer 7, an anode (first electrode) 2, an organic layer 3 including a light emitting layer, and a cathode (second electrode) 4 in this order on a substrate 1. It is an organic EL element. Here, a low refractive index layer 5 and a metal layer 6 are sequentially provided on the opposite side of the cathode 4 from the organic layer 3. The cathode 4 is made of a transparent conductive material, the refractive index of the low refractive index layer 5 is lower than the refractive index of the organic layer 3, and the dielectric layer 7 has a refractive index different from the refractive index of the anode 2. And a pattern having an opening 7A. Here, FIG. 1A shows an organic EL element in which the refractive index of the dielectric layer 7 is higher than the refractive index of the anode 2, while FIG. 1B shows the refractive index of the dielectric layer 7 that is the refractive index of the anode 2. An organic EL element lower than the rate is shown. The anode 2 is formed (conformal) along the pattern of the dielectric layer 7.
When comparing the refractive indexes of the structure on the cathode 4 side as described above, the refractive index of the organic layer 3 means the average refractive index of all the layers including the light emitting layer made of the organic EL material.

FIG. 2 is a perspective view for explaining an example of the organic EL element according to the first embodiment of the present invention. FIG. 2A is a perspective view for explaining an organic EL element in which the openings 7A of the dielectric layer 7 are arranged in islands separated from each other in a plan view, and the anode 2 and the organic layer 3 are respectively formed thereon. It is. FIG. 2B shows an organic EL element in which the openings of the dielectric layer 17 are formed so as to be arrayed in a sea shape where all the openings are connected in a plan view, and the anode 12 and the organic layer 13 are formed thereon. It is a perspective view for demonstrating. The dielectric island portion 17B of the dielectric layer 17 formed in a protruding shape has an effect of refracting light toward the substrate side, similarly to the opening portion 7A in FIG. The shapes of the opening 7A and the dielectric island portion 17B shown in FIGS. 2A and 2B are substantially cylindrical shapes, but are not limited thereto. The shape of the opening 7A or the dielectric island portion 17B may be a truncated cone, a polygonal column, or a stripe shape (line shape). Anode protrusions 12B are formed along the pattern of dielectric layer 17 (conformal). This anode convex part 12B has the effect of refracting light toward the substrate, similarly to the anode concave part 2A in FIG. Therefore, in order to produce the same refraction effect regardless of whether the dielectric layer is a sea part or an island part of a sea-island structure, a description will be given below with reference to FIG.

When the period in which the opening 7A is arranged in at least one direction within the substrate surface is equal to or greater than the wavelength of the emitted light, the shape of the opening 7A has an effect of refracting light toward the substrate at the inner surface 7a. There is no particular limitation. However, when the refractive index of the dielectric layer 7 is higher than the refractive index of the anode 2 as shown in FIG. 1A, from the viewpoint of refracting the guided mode light to the substrate 1 side, the opening 7A side of the substrate 1 side. A shape in which the area of the upper surface on the cathode 4 side is larger than the area of the bottom of the substrate is preferable. In the example shown in FIG. 1A, the inner surface 7a of the opening 7A is arranged substantially perpendicularly to the substrate surface, but the present invention is not limited to this configuration. The angle formed between the inner surface 7a of the opening 7A and the substrate surface, and the angle θ inside the opening 7A is preferably 90 ° to 135 °, more preferably 90 ° to 120 °, and still more preferably 90 ° to 105 °. .
On the other hand, when the refractive index of the dielectric layer 7 is lower than the refractive index of the anode 2 as shown in FIG. 1B, from the viewpoint of refracting the guided mode light to the substrate 1 side, the substrate 1 in the opening 7A. A shape in which the upper surface area on the cathode 4 side is smaller than the bottom area on the side is preferable. In the example shown in FIG. 1B, the inner side surface 7a of the opening 7A is arranged substantially perpendicular to the substrate surface, but is not limited to this configuration. The angle between the inner surface 7a of the opening 7A and the substrate surface, and the angle θ inside the opening 7A is preferably 45 ° to 90 °, more preferably 60 ° to 90 °, and even more preferably 75 ° to 90 °. .
By setting the inner surface 7a of the opening 7A to the above angle, the propagation light re-radiated from the SPP mode light and the light extracted as the guided mode light from the light emission position toward the anode side are within the opening 7A. The light enters the side surface 7a and is refracted toward the substrate 1, and is easily taken out from the outer surface of the substrate.

On the other hand, when the period in which the opening 7A is arranged in at least one direction within the substrate surface is equal to or less than the wavelength of the light, the shape of the opening 7A exhibits a diffraction effect or a photonic crystal effect. However, from the viewpoint of extracting emitted light to the substrate side, it is preferable that the inner side surface 7a of the opening 7A is perpendicular or nearly perpendicular to the substrate surface.
This is because the inner side surface 7a of the opening 7A is an interface that is perpendicular or nearly perpendicular to the substrate surface, so that the refractive index modulation becomes steep in the in-plane direction across the inner side surface 7a of the dielectric layer 7. Because. When the refractive index is sharply modulated, the photonic crystal has a wider band gap frequency range in which light cannot propagate in the in-plane direction of the substrate, and more efficiently emits light emitted from the organic layer 3 from the outer surface of the substrate. Can be taken out. Further, when the refractive index is sharply modulated even in the diffraction grating, the light diffracting effect in the substrate direction is improved, and similarly, the light extraction to the outside of the element is improved. The same applies to the shape of the opening 7A as the dielectric island 17B.
Although the bottom emission structure has been described above as an example, the same applies to the top emission structure.

In the laminated structure of the metal layer / low refractive index layer / cathode / organic layer, which is common to the organic EL device of the present invention, the refractive index of the low refractive index layer is lower than the refractive index of the organic layer. Assuming that the refractive indexes of the low refractive index layer, the cathode, and the organic layer are n _L , n _C , and n _O , respectively, n _L <n _O <n _C (hereinafter referred to as “B pattern”), n _L < There are three cases: n _C <n _O (hereinafter referred to as “C pattern”) and n _C <n _L <n _O (hereinafter referred to as “D pattern”). By the way, in the Otto type arrangement, it is necessary to arrange the layers in the order of metal layer / low refractive index layer / high refractive index layer. Here, in the case of the B pattern, the structure of the metal layer / low refractive index layer / cathode is an Otto type arrangement. In the case of the C pattern, the configuration of the metal layer / low refractive index layer / cathode is an Otto type arrangement, and the configuration of metal layer / low refractive index layer + cathode / organic layer is also an Otto type arrangement. Further, in the case of the D pattern, the configuration of the metal layer / low refractive index layer + cathode / organic layer is an Otto type arrangement.

The most preferable B to D pattern is the C pattern. In this case, first, the structure of the metal layer / low refractive index layer / cathode (transparent conductive layer) is an Otto type arrangement, and the metal layer / low refractive index layer + cathode (transparent conductive layer) / organic layer Since the Otto configuration is also used in the configuration, re-radiation of SPP mode light is most likely to occur from the metal layer. Further, since the refractive index increases in the order of the low refractive index layer, the cathode (transparent conductive layer), and the organic layer, total reflection does not occur at each interface, and the re-radiated SPP mode light is extracted as it is to the substrate side. As this specific configuration, the cathode (transparent conductive layer) is PEDOT: PSS (poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid), typical refractive index: 1.5), etc. The transparent conductive material layer may be a case where the low refractive index layer is SOG (spin on glass) that satisfies the refractive index condition of air or C pattern.
Next preferred is the B pattern. In this case, since the configuration of the metal layer / low refractive index layer / cathode (transparent conductive layer) is an Otto type arrangement, SPP mode light is re-radiated from the metal layer. However, since the refractive index of the organic layer is an intermediate value between the low refractive index layer and the cathode (transparent conductive layer), some of the re-emitted SPP mode light is at the cathode (transparent conductive layer) / organic layer interface. And the remaining light is transmitted through the organic layer. As a specific configuration example, a-ITO (amorphous ITO, typical refractive index: 2.1) is used as a cathode material for an organic layer (typical refractive index: 1.7 to 1.8). And a material having a lower refractive index than the material of the organic layer is selected from SOG as the material of the low refractive index layer.
Next preferred is the D pattern. In this case, the configuration of the metal layer / low refractive index layer / cathode (transparent conductive layer) is not an Otto type arrangement. On the other hand, the Otto type arrangement is employed only in the configuration of metal layer / low refractive index layer + cathode (transparent conductive layer) / organic layer. Therefore, re-radiation of SPP mode light occurs from the metal layer, but re-radiation of SPP mode light is further reduced as compared with the case of the B pattern. Specifically, PEDOT: PSS is selected as the cathode material for the organic layer (typical refractive index: 1.7 to 1.8), and the refractive index n is selected as the material for the low refractive index layer. _{A material in which L} is between n _C and n 2 _O , for example, SOG satisfying the refractive index of the B pattern may be employed.

In the case of n _O <n _C <n _L (hereinafter referred to as “E pattern”) and in the case of n _C <n _O <n _L (hereinafter also referred to as “F pattern”), the Otto type arrangement is not achieved. In the case of n _O <n _L <n _C (hereinafter referred to as “A pattern”), the metal layer / low refractive index layer / cathode is in an Otto type arrangement, and the re-emission of SPP mode light from the metal layer is However, since the refractive index of the organic layer is lower than that of the low refractive index layer, most of the re-radiated SPP mode light is totally reflected at the cathode (transparent conductive layer) / organic layer interface and propagates on the anode side. It is difficult to extract the light extracted as light.

This organic EL element can be applied to both a top emission type and a bottom emission type organic EL element as described above.
In order to be applied to the bottom emission type, the substrate is a translucent 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 it is not necessary 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.
Specific examples of the substrate 1 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 material for the polymer plate include polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyether sulfide, and polysulfone.
When the emitted light is not visible light, the substrate needs to be transparent at least in the emission wavelength region. 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.
In order to apply to the top emission type, in addition to the same as described above, an opaque one can also be used. Specifically, for example, copper (Cu), silver (Ag), gold (Au), platinum (Pt), tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb), aluminum (Al) Or a substrate made of a material made of stainless steel or the like, or a substrate usually used in other top emission type organic EL elements can be used.

The thickness of the substrate 1 is not particularly limited because it depends on the required mechanical strength, but is preferably 0.01 mm to 10 mm, more preferably 0.05 mm to 2 mm.

The dielectric layer 7 of the organic EL element according to the first embodiment includes a plurality of openings 7A, and the inner surface 7a of the opening 7A is covered with the anode 2 having a refractive index different from that of the dielectric layer 7. ing.
The configuration and material of the dielectric layer 7 are such that the inner surface 7a of the opening 7A (the interface between the anode 2 and the dielectric layer 7 extending in a direction perpendicular to or nearly perpendicular to the substrate surface of the substrate 1). The incident light is refracted toward the substrate 1 at this interface, and the incident angle of the propagating light in the organic layer to the outer surface of the substrate 1 (in this specification, the incident angle is the normal between the incident light and the incident surface). Is changed to a smaller angle. This is to reduce the proportion of light totally reflected at the interface between the anode 2 and the substrate 1 or the outer surface of the substrate 1 and improve the light extraction efficiency (see FIGS. 1A and 1B).

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 different from that of the anode 2. When the material of the anode 2 is an indium tin oxide alloy (ITO (typical refractive index: 1.82)), the material having a refractive index lower than that of the anode 2 is, for example, a spin-on glass that satisfies this refractive index condition ( Metal fluorides such as SOG) and magnesium fluoride (MgF ₂ (typical refractive index: 1.38)), and organic fluorine compounds such as polytetrafluoroethylene (typical PTFE (refractive index: 1.35)) , Silicon dioxide (SiO ₂ (typical refractive index: 1.45)), various low-melting glasses, and porous materials. Examples of materials having a higher refractive index than the anode 2 include silicon compounds such as silicon nitride (Si ₃ N ₄ ) (typical refractive index: 2.0), titanium oxide (TiO 2) (typical refraction). Metal oxides, including aluminum oxide (AlN) (typical refractive index: 2.2), aluminum oxynitride (AlON) (typical refraction) And metal oxynitrides such as silicon oxynitride and polymer compound resins such as polyethylene naphthalate (typical refractive index: 1.8).
The thickness of the dielectric layer 7 is not particularly limited. For example, it is 10 to 2000 nm, preferably 50 to 1000 nm. If the thickness is less than 10 nm, the ratio of the thickness of the dielectric layer 7 to the thickness of the organic layer is reduced, and the guided mode light is less likely to be refracted or diffracted. It becomes difficult to maintain the flatness of the side.
When it is set as the structure which arrange | positions the opening part 7A of a dielectric material layer periodically, it is preferable to select the period between the opening parts 7A so that Formula (1) mentioned later may be satisfy | filled. That is, the SPP mode light extracted into the organic layer 3 at a predetermined angle by the cathode structure of the Otto type arrangement is diffracted by the diffraction grating formed by the opening 7A and the anode 2, and the diffracted light is diffracted by the substrate / It is preferable to select a period that satisfies the formula (1) so that the air interface is not totally reflected.

The anode 2 is an electrode for applying a voltage between the anode 4 and injecting holes into the organic layer 3 from the anode 2, and is 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. 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 (High Occupied Molecular Orbital) level with the organic layer 3 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 materials such as indium tin oxide alloy (ITO), zinc oxide tin alloy (IZO), tin oxide, and zinc oxide are available. Conductive polymers such as inorganic oxides (PEDOT: PSS), polyaniline and conductive polymers doped with any acceptor, conductive light-transmitting materials such as carbon nanotubes, thin film metals, metal nanowires formed into thin films And composite materials containing these. Here, the anode 2 can be formed on the substrate 1 by, for example, a sputtering method, a vacuum deposition method, a coating method, a CVD method, an ion plating method, or the like.
The thickness of the anode 2 is not particularly limited. For example, it is 10 to 2000 nm, preferably 50 to 1000 nm. If the thickness is less than 10 nm, the sheet resistance increases. If the thickness is 2000 nm or less, the flatness of the organic layer 3 on the cathode 4 side cannot be maintained, and the transmittance of the anode 2 decreases.
When the anode recesses 2A are periodically arranged by periodically arranging the openings 7A of the dielectric layer, the period between the anode recesses 2A is selected so as to satisfy the formula (1) described later. It is preferable. That is, the SPP mode light extracted into the organic layer 3 at a predetermined angle by the cathode structure of the Otto type arrangement is diffracted by the diffraction grating formed by the anode recess 2A and the organic layer 3, and the diffracted light is diffracted by the substrate. / It is preferable to select a period satisfying the formula (1) so as not to be totally reflected at the air interface.

The organic layer 3 has an inner surface covering portion 3a that covers the inner surface 2a of the anode recess 2A, and a layered portion 3c that is disposed between the anode 2 and the cathode 4. The organic layer 13 includes an outer surface covering portion 13b that covers the outer surface 12b of the anode convex portion 12B, and a layered portion 13c that is disposed between the anode 12 and the cathode 14.

As a material of the light emitting layer, any material known as a material for an organic EL element can be used.
In addition to the light emitting layer (organic light emitting layer), 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.
The hole injection layer is a layer that assists hole injection from the anode 2 to the organic layer 3, and its ionization energy is usually as low as 5.5 eV or less. Such a hole injection layer is preferably a material that injects holes into the organic layer 3 with a lower electric field strength. However, the material to be formed is not particularly limited as long as it can perform the above functions, and is well known. Any one can be selected and used. The hole transport layer is a layer that transports holes to the light emitting region and has a high hole mobility. The material to be formed as such a hole 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 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 these is not particularly limited as long as it can perform the above functions, and any material selected from known materials can be used. 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 such an 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 layered portion 3c of the organic layer 3 is not particularly limited. For example, it is 50 to 2000 nm, preferably 100 to 1000 nm. If it is thinner than 50 nm, extinction other than SPP coupling occurs, such as a decrease in internal quantum efficiency due to punch-through current and lossy surface wave mode coupling due to metal layer 6, and if it is thicker than 2000 nm, it is driven The voltage rises.

The cathode 4 is an electrode for injecting electrons into the organic layer 3, 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 (Lower Unoccupied Molecular Orbital) level of the organic layer 3 does not become excessive.
As a material of the cathode 4, it is necessary to use a light-transmitting conductive material in order to form a cathode side structure with an Otto type arrangement. Therefore, a nonmetallic material can be used among what was mentioned as said anode material.
The thickness of the cathode 4 is not particularly limited, but is, for example, 30 nm to 1 μm, and preferably 50 to 500 nm. If the thickness is less than 30 nm, the sheet resistance increases and the drive voltage increases. If it is thicker than 1 μm, heat and radiation damage during film formation and mechanical damage due to film stress accumulate in the electrode and organic layer.

The low refractive index layer 5 is provided on the opposite side of the cathode 4 from the organic layer 3, and is preferably made of a transparent material having a lower refractive index than the translucent conductive material constituting the cathode 4.
When light emitted from the light emitting layer propagates to the cathode side and reaches the interface between the cathode 4 and the low refractive index layer 5, total reflection occurs when incident at an angle greater than the critical angle.

The material for the low refractive index layer 5 is not particularly limited as long as it is a material having a lower refractive index than the translucent conductive material constituting the cathode 4. For example, SOG satisfying this refractive index, metal fluoride such as magnesium fluoride (MgF ₂ (typical refractive index: 1.38)), polytetrafluoroethylene (PTFE (typical refractive index: 1.35), etc. )) And the like, silicon dioxide (SiO ₂ (typical refractive index: 1.45)), various low-melting glasses, and porous materials. Further, the low refractive index layer 5 is composed of a layer including an air layer, and may have a refractive index lower than that of the translucent conductive material constituting the cathode 4.

The low refractive index layer is preferably made of a material having a refractive index smaller by 0.2 or more than at least one of the cathode and the organic layer. This corresponds to a high refractive index layer in which the cathode and the organic layer are in the Otto type arrangement, and if the difference in refractive index between the low refractive index layer and the high refractive index layer is 0.2 or more in the Otto type arrangement, the wave number of the SPP mode light This is because, since the in-plane component is small, the dispersion curve of the propagation light in the high refractive index layer and the SPP mode light crosses, and the extraction efficiency of the SPP mode light into the high refractive index layer by the Otto type arrangement increases. .

The thickness of the low refractive index layer 5 is preferably 20 nm to 300 nm. When the thickness is 20 nm or less, the film thickness of the low refractive index layer 5 is too thin, so that the metal layer and the high refractive index layer come close to each other and the in-plane wave number component of the SPP mode light becomes large. When the in-plane wave number component of the SPP mode light is increased, the dispersion curve does not intersect with the dispersion curve of the propagation light in the high refractive index layer, and the SPP mode light is not easily extracted into the high refractive index layer. When the thickness is 300 nm or more, the film thickness of the low refractive index layer 5 is too thick, so that the evanescent wave does not reach the metal layer 6 and the SPP mode light is hardly extracted into the high refractive index layer. More preferably, it is 200 nm or less.

The metal layer 6 is provided on the opposite side of the cathode 4 from the organic layer 3 via a low refractive index layer 5.
As the material of the metal layer 6, any material or plasmon resonance can be used as long as plasmon resonance is generated by the light emitted from the light emitting layer. A material having a negative real part of the complex dielectric constant and a large absolute value is preferable. Examples of such materials include simple substances such as gold, silver, copper, zinc, aluminum, and magnesium, alloys of gold and silver, alloys of silver and copper, and alloys such as brass. Further, the metal layer 6 may have a laminated structure of two or more layers.
The thickness of the metal layer 6 is not particularly limited. For example, it is 20 to 2000 nm, preferably 50 to 500 nm. When the thickness is less than 20 nm, the reflectance is lowered and the front luminance is lowered. When the thickness is more than 500 nm, heat, radiation damage, and mechanical damage due to film stress during film formation accumulate in the electrode and the organic layer.

FIG. 3 is a schematic cross-sectional view for explaining an example of the organic EL element according to the second embodiment of the present invention. In the first embodiment, openings and islands are formed in the dielectric layer, and the anode is formed so as to conform to the concavo-convex pattern (conformal), whereas in the second embodiment, the substrate A substrate recess or substrate protrusion is formed on the substrate, and an anode is formed conformally along the uneven pattern. The organic EL element 20 according to the second embodiment of the present invention includes an anode (first electrode) 22, an organic layer 23 including a light emitting layer, and a cathode (second electrode) 24 in this order on a substrate 21. It is an organic EL element. Here, a low refractive index layer 25 and a metal layer 26 are provided in this order on the opposite side of the cathode 24 from the organic layer 23. The cathode 24 is made of a transparent conductive material. The refractive index of the low refractive index layer 25 is lower than the refractive index of the organic layer 23, the substrate 21 is formed with a pattern on the surface on which the anode 22 is formed, and the anode 22 It is formed so as to conform to the pattern (conformal). That is, the organic EL element 20 according to the second embodiment corresponds to the case where the dielectric layer 7 is made of the same material as the substrate in the organic EL element according to the first embodiment.
As described above, when comparing the refractive index of the structure on the cathode 24 side, the refractive index of the organic layer 23 means an average refractive index of all the layers including the light emitting layer made of the organic EL material.

FIG. 4 is a perspective view for explaining an example of the organic EL element according to the second embodiment of the present invention. FIG. 4A shows a plurality of island-shaped substrate recesses (substrate openings) in the substrate 21. FIG. It is a perspective view for demonstrating the organic EL element which processed the 21A and formed the anode 22 so that the pattern of the board | substrate 21 might be followed (conformal). FIG. 4B shows an organic EL in which a plurality of island-shaped substrate convex portions (substrate island-shaped portions) 21B are processed on the substrate 21, and the anode 22 is formed so as to follow the pattern of the substrate 21 (conformal ridge). It is a perspective view for demonstrating an element. This substrate convex portion 21B has an effect of refracting light toward the substrate 1 as in the case of the substrate concave portion 21A in FIG. Therefore, in the uneven portion of the substrate 21, even if the substrate portion forms the sea portion of the sea-island structure or the island portion has the same refraction effect, hereinafter, the substrate recess portion 21 </ b> A in FIG. It demonstrates based on the organic EL element which has.

When the period in which the substrate recess 21A is arranged in at least one direction within the substrate surface is equal to or greater than the wavelength of the emitted light, the shape of the substrate recess 21A is not particularly limited as long as the inner side surface refracts light toward the substrate. There is no particular limitation.
When the refractive index of the substrate 21 is higher than the refractive index of the anode 22, from the viewpoint of refracting the guided mode light toward the substrate 21, the substrate recess 21 </ b> A has an upper surface on the cathode 24 side from the bottom area on the substrate outer surface side. A shape with a larger area is preferred.
In the example shown in FIG. 3, the inner side surface 21 a of the substrate recess 21 </ b> A is arranged substantially perpendicularly to the substrate surface, but is not limited to this configuration. The angle formed between the inner surface 21a of the substrate recess 21A and the substrate surface, and the inner angle of the substrate recess 21A is preferably 90 ° to 135 °, more preferably 90 ° to 120 °, and still more preferably 90 ° to 105 °.
On the other hand, when the refractive index of the substrate 21 is lower than the refractive index of the anode 22, from the viewpoint of refracting the guided mode light to the substrate 21 side, the substrate recess 21A is located on the cathode 24 side from the bottom area on the substrate outer surface side. A shape having a small upper surface area is preferred. In the example shown in FIG. 3, the substrate recess inner side surface 21 a of the substrate recess 21 </ b> A is arranged substantially perpendicular to the substrate surface, but is not limited to this configuration. The angle between the inner surface 21a of the substrate recess 21A and the substrate surface, and the angle inside the substrate recess is preferably 45 ° to 90 °, more preferably 60 ° to 90 °, and even more preferably 75 ° to 90 °.
By setting the inner side surface 21a of the substrate recess to the angle as described above, the light extracted as the propagating light re-radiated from the waveguide mode light and the SPP mode light from the light emitting position toward the anode side can be extracted. Is incident on the substrate 21 and refracted toward the substrate 21 side, and is easily taken out from the outer surface of the substrate.

On the other hand, when the period in which the substrate recess 21A is arranged in at least one direction within the substrate surface is equal to or less than the wavelength of light, the shape of the substrate recess 21A exhibits the effect of diffraction and the effect of photonic crystals. If it is, it will not be specifically limited. From the viewpoint of extracting emitted light to the substrate side, it is preferable that the substrate recess inner side surface 21a of the substrate recess 21A is perpendicular or nearly perpendicular to the substrate surface.
This is because the substrate recess inner surface 21a of the substrate recess 21A is an interface that is perpendicular or nearly perpendicular to the substrate surface, so that the refractive index modulation is steep in the in-plane direction across the substrate recess inner surface 21a of the substrate 21. Because it becomes. When the refractive index modulation is steep, the band gap frequency at which light cannot propagate in the in-plane direction of the photonic crystal becomes wider, and the light emitted from the organic layer 23 can be extracted more efficiently to the outside. Because. Further, when the refractive index is sharply modulated even in the diffraction grating, the light diffracting effect in the substrate direction is improved, and similarly, the light extraction to the outside of the element is improved.
As described above, the same can be said regarding the shape of the substrate recess 21A as the substrate protrusion 21B.

In the organic EL element according to the second embodiment, since the substrate 21 includes a plurality of substrate recesses 21A, it is preferable that the material be a material that can be processed more accurately. Although it does not specifically limit as a preferable material, For example, quartz is mentioned.

5A and 5B are schematic cross-sectional views for explaining an example of the organic EL element according to the third embodiment of the present invention. In the first embodiment and the second embodiment, the anode is formed on the anode on which the unevenness is formed so that the anode side surface of the organic layer conforms to the uneven shape (conformal). In the embodiment, a flattening layer for flattening the uneven shape of the anode is provided between the anode and the organic layer, and both surfaces of the organic layer formed thereon have a flat shape.
An organic EL element 30 shown in FIGS. 5A and 5B includes a dielectric layer 37, an anode (first electrode) 32, an organic layer 33 including a light emitting layer, and a planarizing layer 38 on a substrate 31. And the cathode (second electrode) 34 in order. Here, a low refractive index layer 35 and a metal layer 36 are sequentially provided on the opposite side of the cathode 34 from the organic layer 33. The cathode 34 is made of a transparent conductive material, the refractive index of the low refractive index layer 35 is lower than the refractive index of the organic layer 33, and the dielectric layer 37 has a refractive index different from the refractive index of the anode 32. And a pattern having an opening 37A. The planarizing layer 38 is formed so as to planarize the uneven shape of the anode 32. FIG. 5A shows an organic EL element in which the planarizing layer 38 is formed so as to fill the concave portion of the anode 32. FIG. 5B shows an organic EL element in which the planarizing layer 38 is formed so as to cover the entire anode 32. The dielectric layer 37 and the substrate 31 may be made of the same material. In this case, as shown in the second embodiment, it can be considered that a substrate recess or substrate protrusion is formed on the substrate 31.

Also in the present embodiment, as in the first embodiment, the openings of the dielectric layer are island-shaped that are independent from each other in plan view, or are connected to each other in the sea shape (the protrusions of the dielectric layer are independent in plan view). (Island shape).

When the period in which the opening 37A is arranged in at least one direction within the substrate surface is equal to or greater than the wavelength of the light, the shape of the opening 37A is particularly effective as long as the inner surface has an effect of refracting light toward the substrate. There is no limitation. That is, in the example shown in FIG. 5, the inner side surface 37a of the opening 37A is arranged substantially perpendicularly to the substrate surface, but is not limited to such a configuration.
When the refractive index of the dielectric layer 37 is higher than the refractive index of the anode 32, from the viewpoint of refracting the guided mode light toward the substrate 31 side, the opening 37A is an upper surface on the cathode 34 side from the bottom area on the substrate 31 side. A shape with a larger area is preferred. The angle formed by the inner surface 37a of the opening 37A and the substrate surface, and the angle inside the opening 37A is preferably 90 ° to 135 °, more preferably 90 ° to 120 °, and still more preferably 90 ° to 105 °.
On the other hand, when the refractive index of the dielectric layer 37 is lower than the refractive index of the anode 32, the upper surface area on the cathode 34 side is smaller than the bottom area on the substrate 31 side from the viewpoint of refracting the guided mode light more toward the substrate 31 side. Shape is preferred. The angle formed by the inner surface 37a of the opening 37A and the substrate surface, and the angle inside the opening 37A is preferably 45 ° to 90 °, more preferably 60 ° to 90 °, and even more preferably 75 ° to 90 °.
By setting the inner side surface 37a of the opening 37A to the above angle, the propagating light re-radiated from the SPP mode light and the light traveling from the light emission position toward the anode side enter the inner side surface 37a of the opening 37A and enter the substrate. It is refracted to the side 31 and is taken out from the outer surface of the substrate.

On the other hand, when the period in which the adjacent openings 37A are arranged in at least one direction in the substrate surface is equal to or less than the wavelength of the light, it is particularly limited as long as the effect of diffraction and the effect of the photonic crystal are exhibited. Not done. From the viewpoint of extracting emitted light to the substrate side, the inner side surface 37a of the opening 37A is preferably perpendicular or nearly perpendicular to the substrate surface.
This is because the modulation of the refractive index becomes steep in the direction crossing the dielectric layer 37 in the in-plane direction of the substrate because the inner side surface 37a of the opening 37A is an interface perpendicular or nearly perpendicular to the substrate surface. is there. When the refractive index modulation is steep, the frequency range of the band gap is widened, and the light emitted from the organic layer 33 can be extracted from the outer surface of the substrate to the outside more efficiently. Further, when the refractive index is sharply modulated even in the diffraction grating, the light diffracting effect in the substrate direction is improved, and similarly, the light extraction to the outside of the element is improved.

The planarization layer 38 planarizes the surface facing the organic layer of the anode, and is formed so as to cover part or all of the surface. As shown in FIG. 5A, when covering a part of the surface of the anode, the planarizing layer 38 may or may not have conductivity, and may be transparent to visible light. 37 and the same material as the anode 32 can be used. On the other hand, as shown in FIG. 5B, in order to cover the whole anode surface, it is necessary to have conductivity. Various conductive materials such as the same material as the anode 32 can be used. As a method for forming the planarizing layer, for example, a dry process method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or a wet process such as a coating method can be used. .

The operation effect of the second electrode side structure by the Otto type arrangement of the organic EL element of the present invention will be described below. The following is a principle explanation based on the calculation formula, and therefore, the first electrode and the second electrode are not associated with either the anode or the cathode, respectively, and are described as the first electrode and the second electrode.
Let ω _{sp be} the angular frequency of surface plasmon polariton (SPP) generated on a flat metal surface, and k _{sp be} the real part of the in-plane component of the wave number. This dispersion relationship (the relationship between the angular frequency and the wave number) is determined by the real part ε ₁ of the dielectric constant of the metal and the dielectric constant ε ₂ of the dielectric contacting the metal surface, and is approximately expressed by the following equation (2). (C is the speed of light in a vacuum).

On the other hand, the dispersion relation of normal propagation light is given by the following equation (3), where the angular frequency is ω and the wave number vector is k.

The dispersion curve of surface plasmon polariton (SPP) does not intersect the normal dispersion light dispersion line. Therefore, normal propagating light cannot excite SPP on a flat metal surface, and propagating light cannot be extracted directly from SPP existing on the flat metal surface.

On the other hand, in the case of using an Otto type arrangement, that is, a laminated structure of a high refractive index dielectric layer (dielectric constant ε ₃ ) / low refractive index dielectric layer (dielectric constant ε ₂ ) / metal (dielectric constant ε ₁ ) think about. Here, light incident at an incident angle larger than the critical angle from the high refractive index dielectric layer side is totally reflected at the interface between the high refractive index dielectric layer and the low refractive index dielectric layer. At this time, an evanescent wave that is non-propagating light is generated on the low refractive index dielectric layer side of the interface, and the light intensity attenuates as the distance from the point of total reflection increases (incident light is totally reflected at the interface, Some of them can be seen oozing out of the interface). The dispersion curve of this evanescent wave is given by the following equation (4). Here, θ is an incident angle of incident light from the high refractive index dielectric layer to the low refractive index dielectric layer.

Therefore, by changing the incident angle θ, the SPP dispersion curve intersects with the dispersion line of the total reflection evanescent wave (hereinafter, simply referred to as “evanescent wave” as well as the total reflection). (Ω = ω _sp , k = k _sp ) can be provided. That is, if evanescent waves are used, SPP can be excited on a flat metal surface. Moreover, it becomes possible to take out from the SPP existing on the flat metal surface as propagating light via the evanescent wave. Here, the “incident angle θ” is the radiation angle of the SPP when viewed from the metal side.
In other words, when the Otto type arrangement is used, the dispersion curve of the SPP and the dispersion line of the evanescent wave intersect each other. This means that only the SPP radiated at a predetermined angle is in a state where energy can be exchanged when the SPP and the evanescent wave resonate. And it becomes possible to take out SPP as propagation light radiated | emitted at a predetermined angle via an evanescent wave.

Accordingly, in the organic EL element, for example, when a high refractive index layer / low refractive index layer / metal layer is provided adjacent to the organic layer, a predetermined incident angle (SPP dispersion curve) of the light emitted from the organic light emitting layer is provided. And the light incident on the interface of the high refractive index layer / low refractive index from the high refractive index dielectric layer at an angle where the dispersion line and the dispersion line of the evanescent wave intersect) produces an evanescent wave. The evanescent wave excites SPP mode light on the metal surface. Further, the SPP mode light excited on the metal surface can be extracted as propagating light radiated at a predetermined angle via the evanescent wave generated in the Otto type arrangement structure. That is, by introducing an Otto type arrangement structure in the organic EL element, it is possible to extract SPP mode light as propagating light emitted at a predetermined angle. However, the excitation / extraction of the SPP mode light via the evanescent wave occurs when the low refractive index layer is sufficiently thin. This is because if the low refractive index layer is too thick, the evanescent wave oozes from the organic layer does not reach the metal layer, and the evanescent wave and the SPP mode light cannot exchange energy. If the low-refractive index layer is too thin, the metal layer and the high-refractive index layer come close to each other and the wave number of the SPP mode becomes larger than the formula (2), and the dispersion curve does not intersect with the propagation curve (3) of the propagation light. .
As described above, the light extracted from the SPP is emitted at a predetermined angle corresponding to the intersection of the SPP dispersion curve and the evanescent wave dispersion line.

Next, the effect of the first electrode side structure of the organic EL element of the present invention will be described below.
As for the first electrode side structure, the propagation light in the organic layer is refracted toward the substrate side, and the incident angle to the interface (the angle formed by the incident light and the normal line of the incident interface) is reduced. Thus, an interface having a refractive index that is perpendicular or nearly perpendicular is introduced.
More specifically, by providing a structure in which an opening is provided in the dielectric layer and the inner side surface thereof is covered with a first electrode made of a material having a refractive index different from that of the dielectric layer, An interface between the dielectric layer and the first electrode is introduced as an interface close to vertical. Further, by providing a dielectric island-like portion on the dielectric layer and covering the outer surface with the first electrode, the dielectric layer serves as an interface having a refractive index that is perpendicular or nearly perpendicular to the substrate surface. And an interface between the first electrode and the first electrode may be introduced.

The first electrode side structure may be a refractive index modulation structure having periodicity in the in-plane direction of the substrate or an aperiodic structure having no periodicity.
When the first electrode side structure is a refractive index modulation structure having periodicity, that is, when the dielectric layers having different refractive indices and the first electrode are periodically arranged one-dimensionally or two-dimensionally, In addition to the effects described above, diffraction effects (effects in which light is directed at a predetermined angle with respect to the substrate surface) by transmission diffraction gratings (hereinafter simply referred to as “diffraction gratings”) and effects by photonic crystals (specific directions) (Effect of prohibiting propagation of light of frequency) It is possible to extract guided mode light to the substrate side.
When the period (pitch) of the refractive index modulation structure of the first electrode side structure is sufficiently larger than the wavelength, refraction is considered to be the dominant mechanism and light is extracted. On the other hand, when the period of the refractive index modulation structure of the first electrode side structure is equal to or less than the wavelength, the effect of the diffraction grating or the effect of the photonic crystal becomes the dominant mechanism and light is extracted. Conceivable.

The principle of improving the light extraction efficiency when the first electrode side structure has a refractive index periodicity and functions as a transmissive diffraction grating will be described more specifically with reference to FIGS.
FIG. 6 is a schematic cross-sectional view of an organic EL element having a second electrode side structure having an Otto type arrangement. First, the principle of extracting SPP mode light as guided mode light by this second electrode side structure will be described with reference to FIG. In FIG. 6, the first electrode side structure is omitted.
Here, n _sub is the refractive index of the substrate, n _OLED is the average refractive index of the first electrode, the organic layer, and the second electrode, n ₂ is the refractive index of the low refractive index layer, and ε ₂ is the dielectric of the low refractive index layer. Ε ₁ is the real part of the dielectric constant of the metal layer, k _sp is the in-plane component of the wave number vector of the SPP mode light, k ₀ is the wave number of light in vacuum (2π / λ) (λ is from the light emitting layer) The wavelength of the emitted light in vacuum), θ is the propagation angle of the light propagating through the high refractive index layer.
The wave number k _sp of the SPP mode light is given by the following equation (5) from the equation (2).

However, ε ₂ = n ₂ ² . In order for the SPP mode light and it to be re-radiated and extracted as propagating light, the in-plane components of the wave vector match between the SPP mode light and the extracted light, that is, the expression (6) needs to be satisfied. is there.

From the equations (5) and (6), the SPP mode light is extracted as propagating light at an angle satisfying the following equation (7).

Next, the principle of extracting the light extracted from the SPP mode light to the outside by the diffraction grating will be described.
FIG. 7 is a partial schematic cross-sectional view including the first electrode side structure of the organic EL element having the first electrode side structure including the transmission diffraction grating.
It is assumed that light extracted from the SPP mode light at a predetermined angle θ is diffracted by a diffraction grating having a period (period of a refractive index modulation structure) p. The conditions for diffracting to the substrate side at a predetermined angle θ _sub with respect to the substrate surface are the in-plane wave number of incident light incident on the diffraction grating (the magnitude of the component in the substrate surface direction of the wave number) and the in-plane wave number of diffracted light. Is the integer multiple of 2π / p, and is represented by the following formula (8). Here, N = 0, ± 1,...
In FIG. 7, “OLED stack” indicates a layer through which guided mode light including the first electrode and the organic layer propagates, and the specific layer configuration is the specific configuration of the present invention. Dependent. The position where the “diffraction grating” is provided depends on the specific configuration of the present invention.

Equation (9) is obtained from Equation (7) and Equation (8).

The condition under which total reflection does not occur at the interface between the substrate and air is to satisfy equation (10).

Therefore, by providing a diffraction grating in which N exists such that the grating interval of the diffraction grating satisfies the following formula (11), total reflection does not occur at the interface between the substrate and air, and as a result, The light extraction efficiency is improved.

Here, since ε _l <0 and ε ₂ <| ε _l | in the frequency region where the SPP resonance occurs,

N in Formula (11) may be a positive integer.
Furthermore, in order to suppress Fresnel reflection at the interface between the substrate and air, it is desirable that the expression (11) approximately satisfies the following expression. Further, since the actual emission wavelength of the organic EL element has a spectrum distribution, the maximum peak wavelength of the emission spectrum of the light emitting layer is adopted as λ. As the maximum peak wavelength, the maximum peak wavelength of the photoluminescence spectrum can be used.

N is a diffraction order and is an arbitrary integer, but if the diffraction order becomes too large, the directivity of the diffracted light decreases. Therefore, it is preferable to select the pitch p and the wavelength λ so that N satisfying the formula (1) is in the range of 1 ≦ N ≦ 3.

The above theoretical analysis is a one-dimensional analysis. For a one-dimensional diffraction grating structure (a diffraction grating structure in which refractive index modulation structures are arranged at regular intervals in a predetermined direction in the substrate surface) A diffraction effect based on the analysis is obtained. Since the one-dimensional diffraction grating structure does not have a refractive index modulation structure in a direction orthogonal to the one direction, a diffraction effect does not occur for light in the orthogonal direction (light component). On the other hand, the two-dimensional diffraction grating structure has a diffraction grating structure in another direction in the substrate surface, and a diffraction effect is added also in that direction. Therefore, the diffraction effect is larger in the two-dimensional diffraction grating structure than in the one-dimensional diffraction grating structure.
Therefore, in an organic EL element having a configuration in which a positive integer N that satisfies the condition of the formula (1) exists in a predetermined cross section, the light is emitted regardless of whether the configuration is a one-dimensional diffraction grating structure or a two-dimensional diffraction grating structure. An improvement in extraction efficiency is obtained.

Next, improvement in light extraction efficiency due to the effect of the photonic crystal will be described.
A photonic crystal is a structure whose refractive index is periodically different, in particular, a structure whose period is equal to or less than a wavelength. This periodic structure forms a forbidden band (photonic band gap) in which light in a specific wavelength range cannot exist. When the first electrode side structure of the present invention is a periodic refractive index modulation structure and the period is equal to or less than the wavelength, the first electrode side structure is a one-dimensional or two-dimensional photonic crystal (respectively a substrate). It can be regarded as a photonic crystal structure in which lattices are arranged at regular intervals in a predetermined direction or two directions in a plane. In a one-dimensional photonic crystal, light having a wavelength corresponding to the photonic band gap cannot propagate in one direction having a periodic structure. For this reason, the propagation of light is redistributed in directions other than in-plane, and the light can be extracted to the transparent substrate side. However, since the one-dimensional photonic crystal structure does not have a periodic structure in the direction orthogonal to the one direction, there is no photonic band gap in this direction, and there may be no extraction effect due to this. Very small.
On the other hand, since the two-dimensional photonic crystal structure has a lattice structure in two different directions in the plane, a photonic band gap is formed in these two directions, and light cannot propagate. Accordingly, in the two-dimensional photonic crystal, the direction in which light cannot propagate in the plane increases, and thus light is extracted to the transparent substrate more efficiently than the one-dimensional structure.

When the first electrode side structure is a non-periodic structure having no periodicity in the in-plane direction of the substrate, light incident on the first electrode structure is diffracted at random positions and phases. Radiation angle light is not emitted intensifying each other. Therefore, by having such a structure on the first electrode side, relatively uniform (highly diffusible) orientation characteristics can be obtained.
That is, in the case where the first electrode side structure is a periodic structure, it is possible to obtain an alignment characteristic in which the light intensity at a specific radiation angle is increased by the effect of strengthening the emitted light by the diffraction grating, When the first electrode side structure is an aperiodic structure, relatively uniform alignment characteristics can be obtained.
Therefore, the first electrode side structure can be selected to be a structure having periodicity or a non-periodic structure according to a required light distribution characteristic.

Next, the effect of refraction of the organic EL element according to the first embodiment of the present invention will be schematically described with reference to FIGS. In the present invention, one of the first electrode and the second electrode is an anode and the other is a cathode. In the following description, a configuration in which the first electrode is an anode and the second electrode is a cathode will be described as an example.
Here, the light propagation method indicated by the arrows in FIGS. 1A and 1B is schematically shown in order to easily understand the principle of the effect of refraction. The way of light propagation varies depending on the magnitude relationship between the refractive index of the dielectric layer 7 and the refractive index of the anode 2, and FIG. 1A is an explanatory diagram when the former is higher than the refractive index of the latter, and FIG. It is explanatory drawing when the former is lower than the refractive index of the latter.

Of the light emitted at the point Ao of the light emitting layer included in the organic layer 3 in the organic EL element 10 according to the first embodiment of the present invention, the light traveling toward the cathode 4 side is between the cathode 4 and the low refractive index layer 5. When the light is incident on the interface at a larger angle than the critical angle (arrow A1) and totally reflected (arrow A1r), an evanescent wave (arrow A2) is generated in the low refractive index layer 5. The generated evanescent wave oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (arrow A3) is excited.
The excited SPP mode light is re-emitted to the cathode 4 at a predetermined angle (arrow A5) via resonance with the evanescent wave (arrow A4), and can be extracted to the organic layer 3 as propagating light.
In FIG. 1A, a light emission point (or light emission point) Ai indicates a light emission point at a position overlapping the opening 7A of the dielectric layer 7 in plan view (hereinafter, the light emission at this point is referred to as “in Sometimes referred to as “luminescence”.) The light emission point Ao indicates a light emission point between the adjacent openings 7A in plan view (hereinafter, light emission at this point may be referred to as “out light emission”). The light emission point Ae indicates light emission at the boundary between “in light emission” and “out light emission” (hereinafter, light emission at this point may be referred to as “in-out edge light emission”). For “out emission” and “in-out edge emission”, the arrow indicating total reflected light at the interface between the cathode 4 and the low refractive index layer 5 is omitted.
In addition, in the description of this function and effect, only the case of “out emission” is described in detail, but the light propagation after SPP (arrow A3) excitation is also applied to “in emission” and “in-out end emission”. Is the same as in the case of “out emission”.
It should be noted that the current density between the anode 2 portion located above the adjacent opening 7A and the cathode 4 is greater than the current density between the anode recess 2A located above the opening 7A and the cathode 4. Therefore, “out emission” emits more light than “in emission”.

Further, the light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to point A of the organic layer 3 is when the refractive index of the dielectric layer 7 is higher than the refractive index of the anode 2. Is propagated like the light AD1 in FIG.
That is, the light AD1 traveling through the organic layer 3 from the point A further passes through the anode 2 and reaches the dielectric layer 7, and then is refracted at the inner side surface 7a of the opening 7A of the dielectric layer. The light passes through and can be taken out through the substrate 1.
Here, when the light AD1 travels from the dielectric layer 7 to the anode 2, the light AD1 is incident on the substrate 1 due to the difference in refraction at the interface between the dielectric layer 7 and the anode 2 (the inner surface 7a of the opening 7A). The angle changes to a smaller angle (a direction closer to the normal of the substrate 1). Light incident on the outer surface of the substrate 1 (interface between the substrate and air) at an angle greater than the critical angle is totally reflected and becomes substrate mode light that cannot be extracted to the outside, but at the interface between the anode 2 and the dielectric layer 7. , The incident angle of the light AD1 from the substrate 1 to the air changes to a smaller angle. Therefore, it is possible to prevent the light AD1 from becoming substrate mode light due to an increase in light that is not totally reflected. That is, the light extraction efficiency is improved by having a configuration including the interface between the anode 2 and the dielectric layer 7.
Furthermore, when the refractive index of the anode 2 is different from that of the inner side surface covering portion 3a of the organic layer, the light extracted into the organic layer 3 is also refracted at the interface between the anode 2 and the inner side surface covering portion 3a of the organic layer. More preferred.

Of the light emitted at the point P of the light emitting layer included in the organic layer 3, the light PD1 is light that travels toward the substrate in a direction perpendicular to the substrate and travels through the substrate 1 without being refracted at the interface with the substrate 1. It advances and is taken out outside.
The light PD 2 can be refracted at the interface between the anode 2 and the dielectric layer 7, pass through the anode 2, and then be extracted outside through the substrate 1.
Here, when the light PD2 travels from the dielectric layer 7 to the anode 2, it is refracted at the interface between the anode 2 and the dielectric layer 7, and the incident angle of the light PD2 on the substrate 1 changes to a smaller angle. Light incident on the outer surface of the substrate at an angle greater than the critical angle is totally reflected and becomes substrate mode light and is not extracted outside. The light PD2 is refracted at the interface between the anode 2 and the dielectric layer 7, so that the incident angle of the light PD2 to the outer surface of the substrate 1 is changed to a smaller angle. Efficiency is improved. Similar effects can be obtained with the optical PD3.

Further, when the refractive index of the dielectric layer 7 is lower than the refractive index of the anode 2, the light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to the point A of the organic layer 3. Propagates like the light AD1 and is extracted to the substrate 1.
That is, the light AD1 traveling through the organic layer 3 from the point A further passes through the anode 2 and is refracted at the inner surface 7a of the opening 7A, passes through the dielectric layer 7, passes through the substrate 1, and passes through the outside. Can be taken out.
Here, when the light AD1 travels from the anode 2 to the dielectric layer 7, the light AD1 is incident on the substrate 1 due to the difference in refraction at the interface between the anode 2 and the dielectric layer 7 (the inner surface 7a of the opening 7A). The angle changes to a smaller angle. Light incident on the outer surface of the substrate 1 (interface between the substrate and air) at an angle greater than the critical angle is totally reflected, becomes substrate mode light, and is not extracted outside. The refraction at the interface between the anode 2 and the dielectric layer 7 changes the incident angle to the outer surface of the substrate 1 to a smaller angle, so that the light that can avoid this total reflection increases and the light extraction efficiency is improved. That is, the light extraction efficiency is improved by having a configuration including the interface between the anode 2 and the dielectric layer 7.
Further, when the refractive index of the anode 2 is different from that of the inner side surface covering portion 3a of the organic layer, the light extracted to the organic layer 3 is also refracted at the interface between the anode 2 and the inner side surface covering portion 3a. preferable.

Of the light emitted at the point P of the light emitting layer included in the organic layer 3, the light PD1 is light that travels toward the substrate in a direction perpendicular to the substrate and travels through the substrate 1 without being refracted at the interface with the substrate 1. It advances and is taken out outside.
Further, the light PD 2 can be refracted at the interface between the anode 2 and the dielectric layer 7, pass through the dielectric layer 7, and be extracted outside through the substrate 1.
Here, when the light PD2 travels from the anode 2 to the dielectric layer 7, the angle of incidence of the light PD2 on the outer surface of the substrate 1 changes to a smaller angle due to refraction at the interface between the anode 2 and the dielectric layer 7. Light incident at an angle greater than the critical angle is totally reflected on the outer surface of the substrate 1 and is not extracted as substrate mode light, but the light PD2 is refracted at the interface between the anode 2 and the dielectric layer 7 to the substrate 1. Since the incident angle is changed to a smaller angle, the light that is not totally reflected increases and the light extraction efficiency is improved. Similar effects can be obtained with the optical PD3.

Next, in the organic EL element 10 according to the first embodiment of the present invention, the openings 7A are periodically arranged in at least one direction in the plane of the substrate 1 with a period equal to or less than the wavelength of the emitted light. In the case where the body 7 and the anode 2 covering the opening 7A form a diffraction grating, the function and effect of the diffraction grating will be schematically described with reference to FIG. The light propagation method indicated by the arrows in FIG. 8A is schematically shown in order to easily understand the principle of the effect of the diffraction grating.

Of the light emitted from the Do point of the light emitting layer included in the organic layer 3, the light traveling toward the cathode 4 is incident on the interface between the cathode 4 and the low refractive index layer 5 at a large incident angle greater than the critical angle ( Arrow D1) In the case of total reflection (arrow D1r), an evanescent wave (arrow D2) is generated in the low refractive index layer 5. The generated evanescent wave oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (arrow D3) is excited.
The excited SPP is radiated to the cathode 4 at a predetermined angle (arrow D5) through resonance with the evanescent wave (arrow D4), and can be extracted to the organic layer 3 as guided mode light.
The same applies to the light emitted at the Di point and the De point.

The light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to point D of the organic layer 3 propagates through the organic layer and enters the diffraction grating. The incident light is diffracted by the diffraction grating in a predetermined direction (a direction that satisfies the strengthening condition).
Compared with ordinary refracted light, diffracted light is emitted at a certain predetermined angle because the diffracted light at each diffraction point is emitted while interfering.
Here, as indicated by arrows DD1 and DD2, the light incident on the outer surface of the substrate 1 at an incident angle equal to or less than the critical angle is extracted to the outside as it is. Since the light indicated by the arrows DD1 and DD2 is intensified by interference as compared with other propagation directions as described above, it is possible to extract light having a high intensity at a specific angle, and the light extraction efficiency is improved. improves.
On the other hand, as indicated by arrow DD3, light incident on the outer surface of the substrate at an incident angle greater than the critical angle is totally reflected (arrow DD3r) to become substrate mode light and cannot be extracted outside the substrate.
In order to reduce the total reflected light and extract the light efficiently in this way, the material of the metal layer 6 and the low refractive index layer 5 and the period (pitch) of the diffraction grating are set so as to satisfy the equation (1). It is preferable to select. In particular, since the intensity of the diffracted light is higher as the order N is smaller, it is preferable to select the diffraction grating period or the like so as to satisfy the formula (1) for N having the smallest absolute value. In other words, if the expression (1) is satisfied, the light re-radiated from the SPP mode light can be efficiently extracted from the substrate 1 to the outside by the diffraction grating, and the light extraction efficiency can be improved. .
Further, when the refractive index of the anode 2 is different from that of the inner surface covering portion 3a of the organic layer, the anode 2 has a periodic refractive index structure when viewed in a cross section parallel to the substrate plane crossing the inner surface covering portion 3a. Since the portion also has a diffractive structure, and light can be extracted more efficiently, it is more preferable.

Next, in the organic EL element 10 according to the first embodiment of the present invention, in the case where the organic EL element 10 is periodically disposed in at least one direction in the plane of the anode hole portion with a period equal to or less than the wavelength of the emitted light, as described above. It can be considered that a diffraction grating is formed, and on the other hand, it can be regarded as forming a photonic crystal. The effect by the photonic crystal will be schematically described with reference to FIG. The way of light propagation indicated by arrows in FIG. 8B is schematically shown in order to easily understand the principle of the effect of the photonic crystal.

Of the light emitted at the Eo point of the light emitting layer included in the organic layer 3, the light traveling to the cathode 4 side is incident on the interface between the cathode 4 and the low refractive index layer 5 at a large incident angle greater than the critical angle ( Arrow E1) When totally reflected (arrow E1r), an evanescent wave (arrow E2) is generated in the low refractive index layer 5 and oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (Arrow E3) is excited.
The excited SPP can be radiated to the cathode 4 at a predetermined angle (arrow E5) through resonance with the evanescent wave (arrow E4) and extracted to the organic layer 3 as guided mode light.
The same applies to the light emitted at the Ei point and the Ee point.

The light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to point E of the organic layer 3 propagates through the organic layer, and the refractive index of the anode 2 and the dielectric layer 7 is large or small. Regardless of the relationship, it is extracted to the outside by the photonic crystal structure as follows. In a space where a refractive index modulation structure having a period equal to or less than the wavelength of light exists in a certain direction, a photonic band gap occurs in that direction, and light in the band gap frequency range cannot propagate (light confinement effect) .
In the first embodiment of the present invention, the periodic structure is formed by the dielectric layer 7 and the anode 2 covering the opening 7A, where the photonic band gap can be generated in the direction of the arrow ED2 parallel to the substrate. It is. Therefore, propagation in the direction parallel to the substrate is prohibited for light in the band gap frequency range corresponding to the photonic band gap in the direction of ED2.
On the other hand, no photonic band gap occurs in the direction perpendicular to the substrate because the periodic structure forming the photonic crystal structure is not formed. Accordingly, the SPP mode light extracted as propagating light in the organic layer 3 travels in a direction perpendicular to the substrate.
When there is no photonic crystal structure, most of the light extracted into the organic layer 3 is totally reflected at the interface between the anode 2 (or the organic layer 3) and the substrate 1 to become guided mode light, or Although it is totally reflected on the outer surface and becomes substrate mode, the photonic crystal structure changes the light propagation direction in the organic layer to a direction close to perpendicular to the substrate surface, so total reflection at these interfaces is suppressed. The light extraction efficiency to the outside is improved.
Further, when the refractive index of the anode 2 is different from that of the inner side surface covering portion 3a of the organic layer, the anode 2 has a periodic refractive index structure when viewed in a cross section parallel to the substrate plane crossing the inner side surface covering portion 3a. This planar portion also has a photonic crystal structure, which is more preferable because light can be extracted more efficiently.

If the dielectric layer of the first embodiment and the substrate of the second embodiment have irregularities, the refraction effect will be equal if the period (pitch) and size of the irregularities are equal. The effects of the diffraction grating and the photonic crystal are also the same.

(Image display device)
Next, an image display apparatus provided with the above organic EL element will be described. Since the image display apparatus provided with the

organic EL element

10, 20, or 30 is not different depending on the organic EL element, the organic EL element 10 will be described below as a representative of each organic EL element. FIG. 9 is a diagram illustrating an example of an image display device including the organic EL element 10 described above. In addition, the organic EL element may have a bottom emission structure or a top emission structure, but in the following, an example of a bottom emission structure will be described.
The image display device 100 shown in FIG. 9 is a so-called passive matrix type image display device. In addition to the organic EL element 10, the anode wiring 104, the anode auxiliary wiring 106, the cathode wiring 108, the insulating film 110, and the cathode partition 112 , A sealing plate 116 and a sealing material 118.

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 portion side of the substrate 1, and the drive circuit (not shown) provided outside via the anode auxiliary wiring 106. A current can be supplied to the anode wiring 104. 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. Further, similarly to the anode auxiliary wiring 106 for the anode wiring 104, a cathode auxiliary wiring (not shown) is provided at the end of the cathode wiring 108 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 thickness of the insulating film 110 can be set to, for example, 200 nm to 10,000 nm, and the size of the opening 120 can be set to, 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.

On the insulating film 110, a plurality of cathode partition walls 112 are formed along a direction orthogonal to the anode wiring 104 in plan view. 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.

In addition, the substrate 1 is bonded to each other 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 atmosphere. As the sealing plate 116, for example, a glass substrate having a thickness of 0.7 mm to 1.1 mm can be used. The sealing plate 116 may not be transparent when light is extracted from the substrate 1 side as in the case of a bottom emission type element. On the other hand, in the case where light is extracted from the sealing plate 116 side as in the top emission type, the sealing plate 116 needs to be transparent to at least a part of the light emission wavelength region.

In the image display apparatus 100 having such a structure, a current can be supplied to the organic EL element 10 through a positive electrode auxiliary wiring 106 and a negative electrode 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, an image display apparatus provided with the above organic EL element will be described. The image display apparatus provided with the

organic EL element

10, 20, or 30 is not different depending on the organic EL element. In addition, the organic EL element may have a bottom emission structure or a top emission structure, but in the following, an example of a bottom emission structure will be described.
FIG. 10 is a diagram illustrating an example of an illumination device including the organic EL element 10 described above.
The illumination device 200 shown in FIG. 10 is provided on the organic EL element 10 described above, the substrate 1 of the organic EL element 10, the terminal 202 connected to the anode 2 (see FIG. 1), and the cathode 4 (see FIG. 1). 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 a current by applying a voltage between the anode 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, is emitted through the substrate 1, 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)
The manufacturing method of the organic EL element according to the first embodiment of the present invention will be described with reference to the manufacturing method of the bottom emission type organic EL element shown in FIG.
First, as shown in FIG. 11A, the dielectric layer 7 is formed on the substrate 1. The method for forming the dielectric layer 7 is not particularly limited. For example, in addition to a dry process method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, and a CVD method, various wet processes such as a coating method can be used.

In order to form the opening 7A, for example, a method using photolithography can be used. In order to do this, as shown in FIG. 11B, first, a positive resist solution is applied onto the anode 2 and the excess resist solution is removed by spin coating or the like, thereby forming a resist layer 9.

Then, when a mask (not shown) on which a predetermined pattern for forming the opening 7A is drawn is applied and exposure is performed with ultraviolet rays (UV), electron beams (EB), etc., it is shown in FIG. 11C. Thus, the resist layer 9 is exposed to a predetermined pattern corresponding to the opening 7A. Then, the resist layer 9 in the exposed pattern portion is removed using a developer. Thus, the surface of the dielectric film 7 is exposed corresponding to the exposed pattern portion (FIG. 11D).

As shown in FIG. 11E, using the remaining resist layer 9 as a mask, the exposed portion of the dielectric film 7 is removed by etching to form an opening 7A. As the etching, either dry etching or wet etching can be used. In this case, the shape of the opening 7A can be controlled by combining isotropic etching and anisotropic etching. As dry etching, reactive ion etching (RIE) or inductively coupled plasma etching can be used. As wet etching, immersion in dilute hydrochloric acid, dilute sulfuric acid, hydrofluoric acid, phosphoric acid, or aqueous iron chloride is used. You can use the method of doing. By this etching, an opening 7A is formed corresponding to the pattern, and the surface of the substrate 1 is exposed.
The opening 7A can also be formed by direct processing by laser light irradiation. In this case, after forming the dielectric layer 7 on the substrate 1, the substrate 1 is irradiated with a laser beam to directly drill the dielectric layer 7, or the substrate 1 is irradiated with an interference pattern of laser light. Then, an opening 7A having the same pattern as the interference pattern is formed in the dielectric layer. Therefore, since the mask is not formed with a photoresist, the number of processing steps is reduced. Examples of the laser used for processing include a pulse carbon dioxide laser, a Q switch Nd: YAG laser and its harmonics, a titanium sapphire laser, and an excimer laser. In order to prevent damage to the dielectric layer 7 due to laser irradiation, a surface protective film may be formed on the dielectric layer 7 before laser irradiation.

Next, after removing the resist layer 9, as shown in FIG. 11 (f), the anode 2 is formed along the upper surface of the dielectric layer 7 having the opening 7A (conformally). The formation method of this anode 2 is not specifically limited. For example, in addition to a dry process method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, and a CVD method, a wet process such as a coating method 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. . Specific examples of the surface treatment include high-frequency plasma treatment, sputtering treatment, corona treatment, UV ozone irradiation treatment, ultraviolet irradiation treatment, and oxygen plasma treatment.

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. The anode buffer layer can be prepared by applying a wet process. Specific film forming methods include spin coating, casting, micro gravure coating, gravure coating, bar coating, and roll coating. , Wire bar coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset printing method, coating method such as inkjet printing method, dipping method, electrochemical method and the like.

In the case where the anode buffer layer is formed by a dry process, the anode buffer layer can be formed by using a plasma treatment or the like exemplified in JP-A-2006-30312. In addition, a method of forming a film of a single metal, a metal oxide, a metal nitride, or the like can be mentioned. Specific film forming methods include an electron beam evaporation method, a sputtering method, a chemical reaction method, a coating method, and a vacuum evaporation method. The method etc. can be used.

Next, in FIG.11 (g), the organic layer 3 consists of the layer part 3c and the inner surface coating | coated part 3a. The inner side surface covering portion 3a is configured to fill the anode recess 2A and cover the inner side surface 2a of the anode recess 2A, but may be configured to cover only the inner surface 2a of the anode recess 2A. The method for forming the inner side surface covering portion 3a is not particularly limited as in the case of the anode 2, but a conventionally known method can be used, for example, vacuum deposition method, spin coating method, casting method, LB method, various coating methods Etc. can be used.
In addition to forming the inner surface covering portion 3a of the organic layer 3 as described above, the organic layer 3 is also formed by forming the layered portion 3c of the organic layer 3, and the structure corresponding to FIG. Make it.

Next, the cathode 4 is formed on the organic layer 3 as shown in FIG. The cathode 4 can be formed by the same method as the formation of the anode 2 and is not particularly limited. 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.

Next, as shown in FIG. 11 (i), a low refractive index layer 5 is formed on the cathode 4. The method for forming the low refractive index layer 5 is not particularly limited. For example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, and various coating methods can be used.
When the low-refractive index layer 5 is a low-refractive index layer including an air layer, for example, after the SOG layer is formed, the SOG material is left at a predetermined position in the SOG layer using photolithography. The low refractive index layer is formed by etching away the SOG layer so that the portion where the SOG layer is removed becomes an air layer.

Next, as shown in FIG. 11 (j), a metal layer 6 is formed on the low refractive index layer 5. The formation method of the metal layer 6 is not specifically limited. For example, vapor deposition or sputtering can be used.

It is preferable to attach a protective layer or a protective cover (not shown) for driving the organic EL element 10 stably for a long period of time and protecting the organic EL element 10 from external moisture, oxygen, and the like. 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. It is also possible to use a metal having a relatively large ionization tendency such as zinc as a sacrificial layer (a protective layer to be removed in a subsequent process). And these laminated bodies can also be used. Further, as the protective cover, a glass plate, a plastic plate whose surface has been subjected to low water permeability treatment, a metal, or the like can be used. It is preferable to adopt a method in which the protective cover is sealed by being bonded to the substrate 1 with a thermosetting resin, a photocurable resin, or frit glass. At this time, a predetermined space can be maintained by using a spacer, and it is preferable because the protective cover can be prevented from being touched by an external force to damage the organic EL element 10. Then, if an inert gas such as nitrogen, argon or helium, or various inert liquids such as perfluorocarbon is sealed in this space, it is easy to prevent the upper metal layer 6 from being oxidized. 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. Further, 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.

The organic EL element whose sea-island structure is opposite to the anode described in FIG. 2B uses a negative resist in the process of FIG. 11B, or in the process of FIG. It can be manufactured by reversing the mask-shaped opening and the shielding portion.

The manufacturing method of the organic EL device according to the second embodiment of the present invention will be described with reference to the manufacturing method of the bottom emission type organic EL device shown in FIG.
First, in order to form an uneven shape on the substrate 21, for example, a method using photolithography can be used. In order to do this, as shown in FIG. 12A, first, a positive resist solution is applied onto the substrate 21, and the excess resist solution is removed by spin coating or the like to form a resist layer 29.

Then, when a mask (not shown) on which a predetermined pattern for forming the concavo-convex shape is applied and exposure is performed with ultraviolet rays (UV), electron beams (EB), etc., as shown in FIG. Then, a predetermined pattern corresponding to the resist layer 29 is exposed. Then, the resist layer 29a in the exposed pattern portion is removed using a developer. As a result, the surface of the substrate 21 is exposed corresponding to the exposed pattern portion (FIG. 12C).

As shown in FIG. 12D, using the remaining resist layer 29 as a mask, the exposed portion of the substrate 21 is removed by etching to form a substrate recess 21A. As the etching, either dry etching or wet etching can be used. In this case, the shape of the substrate recess 21A can be controlled by combining isotropic etching and anisotropic etching. As dry etching, reactive ion etching (RIE) or inductively coupled plasma etching can be used. As wet etching, for example, when glass is used for the substrate, a method of immersing in hydrofluoric acid can be used. By this etching, irregularities are formed on the surface of the substrate 21 corresponding to the pattern.
The substrate recess 21A can also be formed by direct processing by laser light irradiation. In this case, a laser beam is irradiated onto the substrate 21 to directly drill the substrate 21, or a laser light interference pattern is irradiated onto the substrate 21, and the dielectric layer has the same pattern as the interference pattern. A recess 21A is formed. Therefore, since the mask is not formed with a photoresist, the number of processing steps is reduced. Examples of the laser used for processing include a pulse carbon dioxide laser, a Q switch Nd: YAG laser and its harmonics, a titanium sapphire laser, and an excimer laser. In order to prevent damage to the substrate 21 due to laser irradiation, a surface protective film may be formed on the substrate 21 before laser irradiation.

Next, after removing the resist layer 29, as shown in FIG. 12E, the anode 22 is formed along the substrate surface having the substrate recess 21A (conformal). The anode 22 can be formed by a method similar to the method for forming the organic EL element of the first embodiment. Also, the surface treatment after the formation can be performed in the same manner as the organic EL element of the first embodiment.

Next, in FIG. 12F, the inner side surface covering portion 23a of the organic layer 23 is configured to fill the anode concave portion 22A and cover the inner side surface of the anode concave portion 22A. The structure which coat | covers an inner surface may be sufficient. This organic layer can also be formed by a method similar to the method for forming the organic EL element of the first embodiment.

Formation of cathode 24, low-refractive index layer 25, and metal layer 26 on organic layer 23 The formation of cathode 24, low-refractive index layer 25, and metal layer 26 on organic layer 23 is similarly performed in the organic EL element of the first embodiment. The same processing can be performed. (Fig. 12 (g) to (i))

The organic EL element 20 can be manufactured by the above process. Moreover, after these series of processes, it is preferable to use the organic EL element 20 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 20 from the outside. As these protective layers, the same layers as those of the organic EL element 10 of the first embodiment can be used.

A method for manufacturing the bottom emission structure of the organic EL element according to the third embodiment of the present invention will be described with reference to the method for manufacturing the organic EL element shown in FIG.
First, the same manufacturing method as the bottom emission structure of the first embodiment can be used until the step of forming the anode 32.

As shown in FIG. 13A, a planarizing layer 38 is formed on the anode 32, and the unevenness of the surface of the anode 32 on the side opposite to the dielectric layer is planarized. The flattening layer 38 can be formed using the same material as that used for forming the dielectric layer 37 or the anode 32. In addition, after the planarization layer 38 is formed, the planarization layer surface is subjected to sputtering treatment including high-frequency plasma treatment for the purpose of modifying the planarization layer surface (promoting hole injection into the organic layer and improving wettability). Various surface treatments such as corona treatment, UV ozone irradiation treatment, ultraviolet irradiation treatment, and oxygen plasma treatment may be performed. In FIG. 13A, the planarization layer 38 is formed so as to cover the entire anode 32. However, the planarization layer 38 may be formed so as to fill only a part of the concave portion of the anode 32. Good.

Next, the organic layer 33, the cathode 34, the low refractive index layer 35, and the metal layer 36 are formed in order. The formation of the cathode 34, the low refractive index layer 35, and the metal layer 36 on the organic layer 33 can be similarly processed in the same manner as the organic EL element of the first embodiment. (Fig. 13 (b) to (e))

Through the above steps, the organic EL element 30 can be manufactured. Moreover, after these series of processes, it is preferable to use the organic EL element 30 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 20 from the outside. As these protective layers, the same layers as those of the organic EL element 10 of the first embodiment can be used.

(SPP extraction in Otto type arrangement)
The film thickness of the low refractive index layer capable of taking out surface plasmon polariton (SPP) trapped on the surface of the metal layer by the Otto type arrangement of the organic EL element in the present invention will be examined.

FIG. 14 shows the result of energy dissipation calculation in which the intensity of light emitted from the organic layer is developed with the wave number component in the organic EL element surface direction. The horizontal axis represents the wave number of the light emitted from the organic layer, the organic EL element surface direction component divided by the vacuum wave number k ₀ , that is, the effective refractive index, and the vertical axis represents the light intensity of the wave number, that is, the development. The coefficient is shown. The calculation was performed separately for the TM polarization component and the TE polarization component. This calculation shows the result of an organic EL element in which a flat anode, an organic layer, and a cathode (metal) are laminated on a substrate (glass). In this case, the peak area on the highest wavenumber side of TM polarized light represents the intensity of the SPP mode light, but it can be seen that most of the light emitted from the organic layer is captured as the SPP mode light. In the organic EL element shown in FIG. 14, glass corresponds to the substrate, High-n corresponds to the organic layer including the anode and the light emitting layer made of ITO, and metal corresponds to the cathode. The film thicknesses of the anode and the organic layer are 150 nm and 100 nm, respectively.

On the other hand, FIG. 15 shows the dependence of the intensity of the light (TM polarization component) emitted from the organic layer on the energy dissipation calculation in the Otto type organic EL element, depending on the film thickness of the low refractive index layer. The Otto type organic EL element has the same structure as the element shown in FIG. 14 in the substrate, anode, and organic layer, but a cathode (50 nm) made of ITO, which is a transparent conductive material, is formed on the organic layer. Further, a low refractive index layer and a metal layer are sequentially formed.
The refractive index of the low refractive index layer is 1.38, FIG. 15A shows the case where the metal layer is Al, and FIG. 15B shows the case where the metal layer is Ag. The numbers on the graph lines indicate the film thickness (nm) of the low refractive index layer.

15 (a) and 15 (b), it can be seen that as the film thickness of the low refractive index layer is increased, the peak wave number is decreased and the peak width is decreased. Further, it can be confirmed that as the film thickness increases, the peak wave number shifts slightly and the peak width approaches a constant value. Note that the decrease in the peak wave number indicates that the film thickness of the low refractive index layer in contact with the metal layer increases, and the wave number of the SPP decreases due to the influence of the refractive index of the low refractive index layer. The narrowing of the width indicates that the light captured as the SPP is taken out as propagating light and the attenuation of the light is small. This will be described next.

The change of the peak will be described below with reference to FIGS. In FIG. 16A, the light is completely trapped on the surface of the metal layer as SPP mode light. This represents a time when the film thickness of the low refractive index layer is 0 nm, and the SPP mode light attenuates rapidly while propagating in the in-plane direction through the interface between the metal layer and the cathode, and thus the peak width is large. .
Next, as the film thickness of the low refractive index layer is increased, as shown in FIG. 16B, the SPP mode light and the waveguide mode light are mixed due to the Otto type arrangement. This means that the extracted SPP mode light becomes waveguide mode light, and is re-supplemented as SPP mode light by the metal layer again by interface reflection. In this case, since the light is less likely to attenuate than the SPP mode light of FIG. 16A, the peak width becomes gradually narrower.
Finally, when the film thickness of the low refractive index layer becomes sufficiently large, it becomes as shown in FIG. In this case, although the Otto type arrangement is used, the evanescent wave at the light emitting point does not reach the metal layer and is not captured as SPP mode light. In this case, the emitted light is captured as guided mode light. That is, when the film thickness of the low refractive index layer exceeds a certain thickness, the trapped light is only guided mode light, so the ease of attenuation does not change and the peak width also does not change.

FIG. 17 is a diagram showing a change in peak width (half width) with respect to the film thickness of the low refractive index layer. When the metal layer of FIG. 17 is Al, it can be seen that the peak width does not change when the film thickness of the low refractive index layer is 200 nm or more, and the emitted light is not captured as SPP mode light. Further, it can be seen that when the metal layer is Ag, the peak width does not change when the film thickness of the low refractive index layer is 150 nm or more, and it is not captured as SPP mode light.
That is, the film thickness captured as SPP mode light is 200 nm or less. This study calculates the case where the refractive index of the low refractive index layer is n = 1.38, but the refractive index is not limited to 1.38, and the metal layer is also limited to Ag and Al. is not.

In the Otto type arrangement, the surface plasmon polariton (SPP) trapped on the surface of the metal layer can be extracted by an evanescent wave generated by light totally reflected at the interface between the cathode and the low refractive index layer. That is, the wave number of this evanescent wave needs to have an intersection with the wave number k _{SPP of the} surface plasmon polariton (SPP) generated on the surface of the metal layer.

The wave number k _SPP of the surface plasmon polariton (SPP) generated on the surface of the metal layer can be expressed by the following formula (13). Where ε ₁ is the dielectric constant of the metal layer, ε ₂ is the dielectric constant of the low refractive index layer, and k ₀ is the wave number of light in vacuum at the maximum peak wavelength of light emitted from the light emitting layer.

The real part can be expressed by the following equation (14).

On the other hand, considering that surface plasmon polariton (SPP) generated on the surface of the metal layer propagates in a direction perpendicular to the metal layer, the vertical component of the wave number of the surface plasmon polariton in the dielectric layer is expressed by the following equation ( 16).

When the surface plasmon polariton (SPP) generated on the surface of the metal layer is normalized as 1, it is attenuated exponentially by propagating in the direction perpendicular to the metal layer, and the thickness (h ₂ ) of the low refractive index layer The intensity of the surface plasmon polariton (SPP) at the position where it propagates is approximately when the reflection at each interface can be ignored.

It becomes.
However, κ _SPP is a value obtained by dividing the real part of the in-plane direction component of the surface plasmon polariton (SPP) wave number by the wave number k ₀ of light in vacuum. That is, if the equation (16) is sufficiently large, the electromagnetic field of surface plasmon polariton (SPP) generated on the surface of the metal layer oozes out to the cathode or organic layer, and is caused by total reflection at the interface between the cathode and the low refractive index layer. It can be coupled with evanescent waves and taken out.
FIG. 18A is a graph showing the equation (16) when the metal layer is Al and (b) is Ag.

When this result is compared with FIGS. 15A and 15B, the surface plasmon polariton (SPP) generated on the surface of the metal layer is normalized as 1 in the equation (16). It can be seen that the peak width is saturated to a constant value at the thickness of the low refractive index layer where the intensity of the surface plasmon polariton (SPP) at the position propagated in the thickness direction of the low refractive index layer is 0.4 or less. That is, when the expression (16) is 0.4 or less, it can be said that the intensity of the surface plasmon polariton (SPP) that oozes out to the interface between the low refractive index layer and the cathode is reduced, and the light extraction effect by the Otto type arrangement is reduced. In other words, it can be understood that the light extraction effect by the Otto type arrangement can be sufficiently obtained when the thickness of the low refractive index layer is 0.4 or more in the equation (16).
This study calculates the case where the refractive index of the low refractive index layer is n = 1.38, but the refractive index is not limited to 1.38, and the metal layer is also limited to Ag and Al. is not. If the condition that the intensity of SPP at the interface between the low refractive index layer and the cathode represented by formula (16) is larger than a certain value (for example, 0.4) is satisfied, the SPP mode light is extracted into the organic layer by the Otto arrangement. As long as this condition is satisfied, the refractive index of the low refractive index layer and the material of the cathode are not limited.

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

In the present invention, the effect on the light extraction efficiency of the organic EL element of each embodiment was confirmed by simulation. First, the finite difference time domain method (FDTD method) used for the simulation will be described. 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, it is a technique in which light emission in the light-emitting layer is regarded as radiation from a minute dipole and the time variation of the radiation (electromagnetic field) is tracked. The simulation result shows the result of light extraction to the substrate. Λ on the horizontal axis is the wavelength in vacuum, and η on the vertical axis is the light extraction efficiency (ratio of the light intensity extracted from the substrate to the total radiation intensity from the dipole). The same applies to the following drawings.
In order to simulate a light emission phenomenon close to reality, the calculation was performed with a dipole as a light emission source being random (dipole moments are random in the x, y, and z directions). Here, the x and y directions are directions parallel to the substrate surface, and the z direction is a direction perpendicular to the substrate surface. The graphs of the light extraction efficiency calculation results shown below are all the calculation results for this random dipole.

FIG. 19 shows the result of calculating the dependence of the period in which the opening is arranged on the light extraction efficiency by computer simulation using the FDTD method in order to confirm the effect of the organic EL element of the present invention. The light extraction efficiency obtained by the simulation is the light extraction efficiency when the light is extracted up to the substrate (the relative value of the light intensity extracted up to the substrate with respect to the total emission intensity) (the same applies to the following simulation results). In the graph, λ on the horizontal axis represents the wavelength of the emitted light, and η on the vertical axis represents the light extraction efficiency.

FIG. 20 is a cross-sectional view showing a model structure of the bottom emission type organic EL element 10 of the first embodiment used in the simulation.
The refractive index values used for the calculation are as follows. The substrate 1 is made of glass, and a refractive index of 1.52 is used. Assuming that 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. Further, 1.72 was used as the refractive index of the organic layer 3. Further, assuming that the cathode 4 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 low refractive index layer 5 is made of a material containing spin-on-glass (SOG), and a refractive index of 1.25 is used. Further, assuming that the metal layer 6 is made of aluminum (Al), the refractive index is 0.649 + 4.32i at 550 nm, and other wavelengths are extrapolated by the Drude model. The dielectric layer 7 is made of SiO2, and the refractive index is 1.45.
The layer thicknesses of the dielectric layer 7, the anode 2, the layered portion 3c of the organic layer 3, the cathode 4, the low refractive index layer 5, and the metal layer 6 were 100 nm, 150 nm, 100 nm, 50 nm, 50 nm, and 100 nm, respectively. The layer thicknesses of the anode projection 2B and the anode layer 2c formed so as to conform to the pattern of the dielectric layer 7 are 100 nm and 50 nm, respectively.
Further, calculation was performed for each of the period (P) (distance between the centers of adjacent openings) in which the adjacent openings 7A are arranged being 200 nm, 300 nm, 500 nm, 900 nm, 2000 nm, 4000 nm, and 8000 nm. Further, the opening 7A has a stripe shape (line shape), and the width (W) of the opening 7A in each period is set to 1/2 of the period (P). The opening 7A has a translational structure in the depth direction of the drawing. That is, the opening 7A has a line-like opening shape extending infinitely in the plane in plan view. This is because the light emission pattern corresponding to the period of the opening 7A can be seen more clearly when calculating the magnetic field strength distribution shape later.
Furthermore, for comparison, a structure having a cathode-side structure with an Otto-type arrangement, but not having a first electrode-side structure for extracting propagating light extracted into the organic layer without using it as guided-mode light (hereinafter referred to as a structure of the first electrode-side structure). “There is also a structure that only has an Otto type arrangement”), and there is no cathode side structure of the Otto type arrangement, and there is no first electrode side structure that takes propagating light out of the waveguide mode light. Calculations were also made for the structure (hereinafter sometimes referred to as “standard structure”).
The standard structure means a structure in which an anode layer, an organic layer, and a cathode metal layer are formed in this order on a glass substrate. In the simulation, the standard structure was such that the substrate was made of glass, the anode was made of ITO, the organic layer was sandwiched, and the cathode was made of Al. Refractive indexes of 1.52, 1.82 + 0.009i, 1.72, and 0.649 + 4.32i were used, respectively, and the anode, organic layer, and cathode layer thicknesses were 150 nm, 100 nm, and 100 nm, respectively. It was.

FIG. 19 shows the wavelength dependence of the light extraction efficiency with the period (P) in which the opening 7A is disposed as a parameter. Also, the simulation results for the standard structure and the structure with only the Otto type arrangement are shown in the same graph. FIG. 19 shows that the organic EL element of the present invention has a light extraction efficiency as a whole in the wavelength range of 200 nm to 2000 nm as compared with the structure having only the Otto type arrangement or the standard structure at a wavelength of 680 nm or less. The result was improved. In particular, when the period was 200 nm to 900 nm, the result that the light extraction efficiency was remarkably increased at a wavelength of 680 nm or less was obtained.
This result cannot be predicted based on the structure of the cathode side structure of the Otto type arrangement and the anode side structure (refractive index modulation structure), but was first clarified by the simulation of the present invention. .

FIG. 21A shows the intensity distribution of the electric field of the radiated light from the horizontal dipole obtained by the simulation of the FDTD method in the case of the structure having only the Otto type arrangement. The wavelength of the emitted light was 480 nm. The distribution diagram shows the substrate on the upper side and the metal layer on the lower side. The white line that crosses the electric field strength distribution is the boundary line between adjacent layers, and the distribution diagram corresponds to the electric field strength distribution in the substrate, anode, organic layer, cathode, low refractive index layer, metal layer, air layer in order from the top. Yes. The light source is placed at the right end of the figure, and the electric field intensity distribution in the right half is omitted.
FIGS. 21B and 21C respectively show the radiation from the horizontal dipole obtained by the simulation of the FDTD method when the period of the opening 7A in the organic EL element of the embodiment of the present invention is 500 nm and 900 nm. It shows the intensity distribution of the electric field of light. The wavelength of the emitted light was 480 nm. The distribution diagram shows the substrate on the upper side and the metal layer on the lower side. 21 (b) and (c), the white line crossing the electric field intensity distribution is the boundary line between the adjacent layers, and the distribution diagram shows the substrate, dielectric layer, anode, organic layer, cathode, low refractive index layer, It corresponds to the electric field strength distribution in the metal layer and air layer. Also, a plurality of thin white lines running in the vertical direction in the dielectric layer represent the inner surface of the opening of the dielectric layer, and a plurality of rectangles drawn with white lines in the anode follow the shape of the opening. It represents the opening formed (conformal).
As in FIG. 21A, the light source is placed at the right end of the figure, and the electric field intensity distribution in the right half is omitted. The electric field intensity distribution and the magnetic field intensity distribution shown in the following are illustrated for the organic EL elements similarly arranged.

From the simulation results, as compared with the case of the structure of only the Otto type arrangement of FIG. 21A, each of FIGS. 21B and 21C using the organic EL element of the present invention is obtained from the dipole light source to the organic layer. After propagating in the left direction, light is emitted obliquely upward, and it can be confirmed that the light emission in a specific direction is intensified by the effect of the diffraction grating.
This is difficult to predict even for those skilled in the art, and has been revealed only after simulation.

FIG. 22A shows the intensity distribution of the magnetic field of the emitted light from the dipole in the vertical (z) direction obtained by the simulation of the FDTD method in the case of the structure having only the Otto type arrangement. The wavelength of the emitted light was 480 nm. The distribution diagram shows the substrate on the upper side and the metal layer on the lower side.
FIGS. 22B and 22C show the electric field intensity distribution of the emitted light from the vertical dipole when the period of the opening 7A in the organic EL element of the embodiment is 500 nm and 900 nm, respectively, by simulation of the FDTD method. The obtained results are shown. The wavelength of the emitted light was 480 nm. The distribution diagram shows the substrate on the upper side and the metal layer on the lower side.

From the simulation results, as compared with the case of the structure having only the Otto type arrangement of FIG. 22A, each of FIGS. 22B and 22C using the organic EL element of the present invention is light obliquely upward. Can be confirmed. Further, with respect to the period of the opening 7A, it can be confirmed that those having a period of 900 nm in FIG.
This is difficult to predict even for those skilled in the art, and can be known only after simulation.

FIG. 23 shows the case where the period of the opening 7A of the organic EL element of the embodiment is (a) 200 nm, (b) 300 nm, (c) 500 nm, (d) 900 nm, (e) 2000 nm, and (f) 4000 nm. This figure shows the intensity distribution of the electric field of the synchrotron radiation from the horizontal dipole obtained by FDTD simulation. The wavelength of the emitted light was 620 nm. The intensity distribution is shown with the substrate on the bottom and the metal layer on the top.
FIG. 24 shows the case where the period of the opening 7A of the organic EL element of the embodiment is (a) 200 nm, (b) 300 nm, (c) 500 nm, (d) 900 nm, (e) 2000 nm, and (f) 4000 nm. This shows the intensity distribution of the magnetic field of synchrotron radiation from a vertical dipole obtained by FDTD simulation. The wavelength of the emitted light was 620 nm. The distribution diagram shows the substrate on the upper side and the metal layer on the lower side.

From the simulation results, it can be confirmed that both the electric field and the magnetic field are radiated in an oblique direction in all cases in which the period of the opening 7A is examined.

10, 20, 30

Organic EL elements

1, 11, 21, 31 Substrate 21a Inner side surface of substrate recess 21A Substrate recess 21B Substrate

convex portion

2, 12, 22, 32 Anode 2A Anode

concave portion

2B, 12B Anode

convex portion

3, 13, 23 33 Organic layer 3a Inner side surface covering portion 3c

Layered portion

4, 14, 24, 34

Cathode

5, 15, 25, 35 Low

refractive index layer

6, 16, 26, 36

Metal layer

7, 17, 37 Inside dielectric layer

7a Side surface

7A Opening portion 17B Dielectric island-shaped portion 38

Planarizing layer

9, 29, 39 Resist 9a, 29a Resist modification portion 100 Image display device 104 Anode wiring 106 Anode auxiliary wiring 108 Cathode wiring 110 Insulating film 112 Cathode partition wall 116 Sealing plate 118 Sealant 120 Opening 200 Lighting Device 201 Lighting Circuit 202 Terminal 203 Terminal

Claims

On the substrate, a dielectric layer, an anode, an organic layer including a light emitting layer made of an organic EL material, and a cathode are sequentially formed, and an organic EL configured to extract light from the anode side to the outside. An element,
Furthermore, the cathode is provided with a low refractive index layer and a metal layer in this order on the opposite side of the organic layer,
The cathode is made of a translucent conductive material,
The refractive index of the low refractive index layer is lower than the refractive index of the organic layer,
The dielectric layer has a refractive index lower than the refractive index of the anode and is formed in a pattern having an opening so that the substrate is exposed,
The organic EL element, wherein the anode, the organic layer, the cathode, the low refractive index layer, and the metal layer are formed so as to follow a pattern of the dielectric layer.
An organic EL element comprising a dielectric layer, a first electrode, an organic layer including a light emitting layer, and a second electrode in order,
Furthermore, on the surface opposite to the organic layer of the second electrode, a low refractive index layer having a thickness of 20 nm to 300 nm and a metal layer are sequentially provided.
The second electrode is made of a translucent conductive material,
The refractive index of the low refractive index layer is lower than the refractive index of the organic layer,
The dielectric layer has a refractive index different from the refractive index of the first electrode and is formed in a pattern having an opening,
The organic EL element, wherein the first electrode is formed along a pattern of the dielectric layer.
An organic EL element comprising a dielectric layer, a first electrode, an organic layer including a light emitting layer, and a second electrode in order,
Furthermore, on the surface opposite to the organic layer of the second electrode, a low refractive index layer having a thickness of 20 nm to 300 nm and a metal layer are sequentially provided.
The second electrode is made of a translucent conductive material,
The refractive index of the low refractive index layer is lower than the refractive index of the organic layer,
The dielectric layer has a refractive index different from the refractive index of the first electrode and is formed in a pattern having island-shaped dielectric island portions that are independent from each other in plan view,
The organic EL element, wherein the first electrode is formed along a pattern of the dielectric layer.
An organic EL element comprising, on a substrate, a first electrode, an organic layer including a light emitting layer, and a second electrode in order,
Furthermore, on the surface opposite to the organic layer of the second electrode, a low refractive index layer having a thickness of 20 nm to 300 nm and a metal layer are sequentially provided.
The second electrode is made of a translucent conductive material,
The refractive index of the low refractive index layer is lower than the refractive index of the organic layer,
The substrate has a refractive index different from that of the first electrode;
A pattern having island-shaped substrate islands that are independent of each other in a substrate opening or a plan view is formed on the surface on which the first electrode is formed,
The organic EL element, wherein the first electrode is formed along a pattern of the substrate.
The organic EL element according to any one of claims 1 to 4, wherein a refractive index of the anode or the first electrode is different from that of the organic layer.
The surface of the anode or the first electrode on the organic layer side is flattened by a flattening layer made of a conductor or a dielectric, and the organic layer is flat. An organic EL device according to claim 1.
The organic EL element according to any one of claims 1 to 6, wherein the refractive index of the low refractive index layer is further lower than the refractive index of the cathode or the second electrode.
The organic EL element according to claim 7, wherein a refractive index of the cathode or the second electrode is lower than a refractive index of the organic layer.
The low refractive index layer is made of a material having a refractive index smaller by 0.2 or more than at least one of the cathode, the second electrode, and the organic layer. The organic EL device according to Item.
The period in which the opening or the island-shaped portion and the substrate opening or the substrate island-shaped portion are arranged in at least one direction within the substrate surface is 200 to 2000 nm. The organic EL device according to any one of 9.
A real part ε 1 of the dielectric constant of the metal layer, a dielectric constant ε 2 of the low refractive index layer, and a period (p) in at least one direction of the pattern of the dielectric layer or the pattern of the substrate is an integer N 10. The organic EL device according to claim 1, wherein the organic EL device is selected so as to satisfy the following formula with respect to (1 ≦ N ≦ 3):

Here, λ is the maximum peak wavelength of the photoluminescence spectrum of the light emitting layer.
12. The organic EL element according to claim 11, wherein the period is 200 nm to 2000 nm.
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.