JP2015088388A - Organic el element, and image display apparatus and illumination apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element in which light extraction efficiency is improved by effectively extracting waveguide mode light and SPP mode light, and to provide an image display apparatus and an illumination apparatus each including the organic EL element.SOLUTION: Th organic EL element includes an anode, an organic layer including a light-emitting layer, and a cathode which are successively formed over a substrate, and further includes a low refractive index layer and a metal layer which are formed on a face of the cathode opposite to the organic layer successively from a side brought into contact with the opposite side face. The cathode is a transparent conductive layer composed of a translucent conductive material and a refractive index of the low refractive index layer is lower than a refractive index of the organic layer. A high refractive index layer is formed between the substrate and the anode, the high refractive index layer is composed of a material whose refractive index is higher than that of the substrate and the low refractive index layer, the high refractive index layer includes a plurality of convex portions, each of the convex portions comprises a cylindrical portion and a tip portion successively formed from the anode side, the cylindrical portion is erected vertically from the anode, the tip portion has an apex on the opposite side to the anode and has an inclined plane inclined to the apex.

Description

  The present invention relates to an organic EL element, and an image display device and an illumination device including the organic EL element.

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

For example, in a bottom emission type organic EL device including a transparent electrode, an organic layer including a light emitting layer, and a metal electrode in this order on a transparent substrate, a transparent substrate (for example, glass (typical) of light emitted from the light emitting layer is used. The refractive index: 1.52)) and air (refractive index: 1.0) are incident at a small incident angle (an angle formed by the incident light and the normal of the incident interface) that is smaller than the critical angle. The light is refracted at the interface and taken out of the element. 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 the present specification, this light is referred to as substrate mode light.
Of the light emitted from the light emitting layer, an anode (for example, indium tin oxide (ITO (typical refractive index: 1.82))) made of a transparent conductive oxide and the transparent substrate, or between the anode and the cathode. Light incident on the interface between the substrate and the cathode, such as the interface between the high-refractive index layer and the low-refractive index layer disposed at a larger angle than the critical angle, is totally reflected at the interface and is not extracted outside the device. In the present specification, this light is referred to as “waveguide mode light”.
In addition, when a metal layer such as a metal cathode is present in the organic EL element, out of the light emitted from the light emitting layer, the light enters the metal layer and is combined with free electrons of the metal cathode to form a surface plasmon polariton (SPP). The light trapped on the surface of the metal electrode as Polariton) is not taken out of the device but can be finally absorbed by the material. In the present specification, this light is referred to as SPP mode light.

The light extraction efficiency of the organic EL element (ratio of the light extracted outside the element with respect to the light emitted from the light emitting layer) is generally limited to about 20% (for example, Patent Document 1). That is, about 80% of the light emitted from the light emitting layer is lost, and it is a big problem to reduce these losses and improve the light extraction efficiency.
Here, the extraction of the substrate mode light can be dealt with by providing a light diffusion sheet or the like on the transparent substrate (for example, Patent Document 2), but the reduction and extraction of the waveguide mode light and the SPP mode light, particularly the SPP mode light. 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 improving the light extraction efficiency, a method of forming a diffraction grating at an interface between a transparent substrate and an electrode has been proposed (for example, Patent Document 6).

  In addition to organic EL devices, generally, a method of extracting the SPP mode on the surface of the metal layer from the surface of the metal layer by combining it with the external radiation mode and taking it out from the surface of the metal layer into the organic layer has a low refractive index thin film and a high refractive index. A method of arranging a dielectric constant and adopting an Otto type arrangement (Non-patent Document 1) is often used.

JP 2008-210717A JP 2011-243625 A JP 2011-233288 A Japanese translation of PCT publication No. 2003-522371 JP 2011-82192 A Japanese Patent Laid-Open No. 11-283951

A. Otto, Z. Physik 216, 398 (1968)

  However, even if the SPP mode light is extracted from the metal surface, if the light is captured as guided mode light, it is not extracted outside the device, and the light extraction efficiency is not improved.

  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 inventors first have a two-step light extraction mechanism in which SPP mode light is extracted from the surface of the metal layer into the organic layer, and then the propagating light is extracted outside the device without being guided mode light. Assuming an effective structure that improves light extraction efficiency out of many 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 SPP mode light and extracts the generated SPP mode light from the surface of the metal layer into the organic layer on the second electrode side (Non-Patent Document 1). The structure is composed of a first electrode side structure in which light extracted from the surface of the metal layer into the organic layer is extracted outside the waveguide mode light.

  The inventors of the present invention have shown by simulation that a second electrode side structure having an Otto type arrangement and a convex portion having a specific shape that refracts or directs guided mode light toward the substrate side (opposite side of the substrate in the top emission type). Or, by combining with the first electrode side structure provided with the concave portion, 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. As a result, the inventors have found that the light extraction efficiency is improved by making the shape of the first electrode side structure a specific shape, thereby completing the present invention.

In order to solve the above-mentioned problems, the present invention having the outline adopts the following configuration.
(1) An organic EL device comprising a first electrode, an organic layer including a light emitting layer, and a second electrode in this order, and a low refraction on the surface of the second electrode opposite to the organic layer. A refractive index layer and a metal layer in order from the side in contact with the opposite surface, the second electrode is made of a translucent conductive material, and the refractive index of the low refractive index layer is the refractive index of the organic layer. A high refractive index layer on the surface of the first electrode opposite to the organic layer, and the high refractive index layer is adjacent to the surface opposite to the first electrode. It is made of a material having a refractive index higher than that of the substance and a refractive index higher than that of the low refractive index layer, and the high refractive index layer has a plurality of convex portions, and the convex portions are arranged from the first electrode side. A columnar part and a tip part formed in sequence, the columnar part standing upright with respect to the first electrode, and the tip part being the first electrode Has a top portion on the opposite side, the organic EL element characterized in that it has an inclined surface inclined toward the top.
(2) The organic EL element according to (1), wherein the columnar portion has a height of 0.3 to 500 μm.
(3) The organic EL element according to (1) or (2), wherein a width of the columnar part is 0.3 to 500 μm.
(4) The organic EL element according to any one of (1) to (3), wherein the height of the tip is 0.05 to 5 times the width of the bottom surface.
(5) An organic EL element comprising a first electrode, an organic layer including a light emitting layer, and a second electrode in this order, and a low refraction on the surface of the second electrode opposite to the organic layer. A refractive index layer and a metal layer in order from the side in contact with the opposite surface, the second electrode is made of a translucent conductive material, and the refractive index of the low refractive index layer is the refractive index of the organic layer. A high refractive index layer on the surface of the first electrode opposite to the organic layer, and the high refractive index layer is adjacent to the surface opposite to the first electrode. It is made of a material having a refractive index higher than that of the substance and a refractive index higher than that of the low refractive index layer. Further, the high refractive index layer has a plurality of concave portions, and the concave portions are formed in order from the first electrode side. A columnar hole portion and a root portion, and the columnar hole portion is drilled perpendicularly to the first electrode, and the root portion is The organic EL element characterized in that it has an inclined surface extending toward the opposite side of the first electrode.
(6) The organic EL element according to (5), wherein the depth of the columnar hole is 0.3 to 500 μm.
(7) The organic EL element according to (5) or (6), wherein a width of the columnar hole is 0.3 to 500 μm.
(8) The depth of the root portion is 0.025 to 2.5 times the difference between the width of the root portion and the width of the columnar hole. (5) to (7) The organic EL element as described in any one.
(9) The organic EL element according to any one of (1) to (8), wherein the low refractive index layer has a thickness of 20 nm to 300 nm.
(10) The organic EL element according to any one of (1) to (9), wherein the convex portion or the concave portion is formed in a line shape continuous in one direction in the plane.
(11) The organic EL element according to any one of (1) to (10), wherein the high refractive index layer includes a plurality of layers.
(12) The organic EL element according to any one of (1) to (11), wherein a refractive index of the low refractive index layer is further lower than a refractive index of the second electrode.
(13) The organic EL element according to (12), wherein the refractive index of the second electrode is further lower than the refractive index of the organic layer.
(14) 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 second electrode and the organic layer. Any of (1) to (13) An organic EL device according to claim 1.
(15) An image display device comprising the organic EL element according to any one of (1) to (14).
(16) An illuminating device comprising the organic EL element according to any one of (1) to (14).

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element which extracted the SPP mode light and the waveguide mode light effectively, and the light extraction efficiency improved, and an image display apparatus and an illuminating device provided with the same can be provided.

It is a cross-sectional schematic diagram for demonstrating an example of the organic EL element which concerns on the 1st Embodiment of this invention. It is a cross-sectional schematic diagram which represented the convex part of this invention typically. It is the schematic diagram which planarly viewed the columnar part of the convex part of this invention. It is the schematic diagram which represented typically the arrangement | positioning at the time of planar view of the convex part of this invention. It is the schematic diagram which looked at the organic EL element of this invention, (a) is a perspective view of the organic EL element which concerns on 1st Embodiment, (b) is the perspective view of the organic EL element which concerns on 2nd Embodiment. FIG. It is a cross-sectional schematic diagram which represented the recessed part of this invention typically. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic diagram typically shown in order to demonstrate the principle of the refractive action effect in the organic EL element of this invention in an easy-to-understand manner, and (a) schematically shows the principle of the refractive action effect of the organic EL element of the first embodiment. (B) is a schematic diagram schematically showing the principle of the refractive action effect of an organic EL element having no tip at the convex part. 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 which represented typically the 1st manufacturing method of the organic EL element which concerns on this invention. It is a cross-sectional schematic diagram which represented typically the 2nd manufacturing method of the organic EL element which concerns on this invention. In an organic EL element having a standard structure having an anode, an organic layer, and a cathode (metal) on a substrate, an energy dissipation calculation was performed to develop the intensity of light emitted from the organic layer with a wave number in the surface direction of the organic EL element. Results are shown. It is the figure which showed the dependence by the film thickness of a low-refractive-index layer of energy dissipation calculation in Otto type | mold arrangement | positioning, the refractive index of a low-refractive-index layer shall be 1.38, (a) makes a reflective layer Al, ( b) is a diagram showing the results when Ag is used as the reflective layer. It is a cross-sectional schematic diagram of the organic EL element of Otto type | mold arrangement | positioning for demonstrating the change of the peak in FIG. (A) is a case where the film thickness of a low refractive index layer is 0 nm. (B) is a case where SPP mode light and waveguide mode light coexist as the film thickness of the low refractive index layer increases. (C) is a case where the film thickness of the low refractive index layer is sufficiently thick so that the evanescent wave does not reach the metal layer and is not captured as SPP mode light. It is the figure which showed the change of the peak width (half value width) with respect to the film thickness of a low-refractive-index layer in the result of energy dissipation calculation in FIG. In the Otto type organic EL element, (a) is a graph showing the formula (5) when the reflective layer is Al, and (b) is the reflective layer is Ag. It is a cross-sectional schematic diagram which shows the model structure of the organic EL element of Example 1 of this invention used by simulation. It is the cross-sectional schematic diagram cut | disconnected in the cross section which crosses the translation structure of the convex part of the organic EL element used by simulation, (a) is the shape of the convex part of Example 2, (b) is the convex part of Example 3. (C) is the shape of the convex part of the comparative example 1. It is a figure which shows the result of having calculated | required the light extraction efficiency of the organic EL element of Examples 1-3 and Comparative Examples 1-3 by the computer simulation using FDTD method.

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. In addition, the contents described in one embodiment may be omitted in other embodiments.
The so-called top emission type or bottom emission type 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 (first embodiment))
FIG. 1 is a schematic cross-sectional view for explaining an example of the organic EL element according to the first embodiment of the present invention. FIG. 5A is a schematic perspective view for explaining the organic EL element according to the first embodiment.
An organic EL element 10 shown in FIG. 1 is an organic EL element having 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. Further, the cathode 4 is provided with a low refractive index layer 5 and a metal layer 6 in this order on the surface opposite to the organic layer 3 from the side in contact with the opposite surface. The low refractive index layer 5 has a refractive index lower than that of the organic layer 3, and has a high refractive index layer 7 on the surface opposite to the organic layer 3 of the anode 2, and has a high refractive index. The layer 7 is made of a material having a refractive index higher than that of the substrate 1 (a material in which the high refractive index layer 7 is adjacent to the surface opposite to the anode 2) and a refractive index higher than that of the low refractive index layer 5. The refractive index layer 7 has a plurality of convex portions 7a. The convex portion 7a is composed of a columnar portion 7a1 and a tip portion 7a2 formed in this order from the anode 2 side, and the columnar portion 7a. Is erected perpendicularly to the anode 2, the distal end portion 7a2 has a top on the opposite side of the anode, and is characterized by having an inclined surface inclined toward the top. The “inclined surface” mentioned here may be an “inclined plane” or an “inclined curved surface”.
Further, as shown in FIG. 1, the high refractive index layer 7 may have a layered portion 7b.
In FIG. 1, the configuration indicated by the solid line is a bottom emission type. In FIG. 1, reference numeral 1 ′ shows the arrangement of the substrates in the case of the top emission type in order to easily explain the configuration of the present invention. In this case, it is not necessary to provide the substrate 1, and the substance in which the high refractive index layer 7 is adjacent to the surface opposite to the anode 2 may be air, for example. The substrate arrangement in the case of the top emission type is the same in the other embodiments.
As described above, when comparing the refractive indexes of the structure on the cathode side, the refractive index of the organic layer means the average refractive index of all the layers including the light emitting layer made of the organic EL material.

  In the laminated structure of the metal layer / low refractive index layer / organic layer, which is a structure on the cathode side common to the organic EL element of the present invention, in order for these to be Otto type arrangement, the refractive index of the low refractive index layer is organic. It must be lower than the refractive index of the layer. With such a refractive index configuration, SPP mode light generated at the metal layer / low refractive index interface can be extracted into the organic layer. More preferably, the refractive index of the cathode is higher than the refractive index of the low refractive index layer. When the refractive index of the cathode is higher than the refractive index of the low refractive index layer, the structure of the metal layer / low refractive index layer / cathode is also an Otto type arrangement. Layer or high refractive index layer. Furthermore, the refractive index of the cathode is preferably lower than the refractive index of the organic layer. With such a refractive index configuration, the SPP mode light extracted to the cathode can be extracted to the organic layer without being totally reflected at the cathode / organic layer interface.

The organic EL element 10 of the present invention has a top emission type (when the substrate 1 ′ is on the side opposite to the low refractive index layer 5 when viewed from the metal layer 6), a bottom emission type (as opposed to the organic layer 3 when viewed from the anode 2). It can be applied to any of the organic EL elements in the case where the substrate 1 is on the side.
When applied to the bottom emission type, the substrate 1 is a light-transmitting substrate and usually needs to be transparent to visible light. Here, “transparent to visible light” means that it is only necessary to transmit visible light having a wavelength emitted from the light emitting layer, and 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. Further, the transmittance is more preferably 70% or more.
Specific examples of the material constituting the substrate 1 include glass and polymer. Examples of the glass include soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer include polycarbonate, acrylic, polyethylene terephthalate, polyethylene naphthalate, polyether sulfide, and polysulfone.
Even when the emitted light is not visible light, it is necessary to be transparent at least in the emission wavelength region as in the case of visible light. The transmittance is preferably 50% or more and more preferably 70% or more with respect to the wavelength at which light emission has the maximum intensity.
In order to apply to the top emission type, an opaque material can be used in addition to the same as described above. Specifically, for example, Cu, Ag, Au, Pt, W, Ti, Ta, Nb, Al alone, an alloy containing these elements, or a metal material such as stainless steel, Si, SiC, AlN, GaN, Nonmetallic materials such as GaAs and sapphire, and other substrate materials usually used in top emission type organic EL elements can be used. In addition, in order to release heat generated due to light emission of the element, it is preferable to use a material having high thermal conductivity for the substrate.
However, in this embodiment, since the high refractive index layer 7 forms the convex portion 7a, the substrate 1 is provided with a plurality of concave portions corresponding thereto, and therefore, it is preferable that the material be easily processed more accurately. Although it does not specifically limit as a preferable material, For example, quartz is mentioned.

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

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, and it is preferable to use a material having a work function of 4 eV or more and 6 eV or less so that the difference from the HOMO (Highest Occupied Molecular Orbital) level of the organic layer 3 in contact with the anode 2 does not become excessive. The material of the anode 2 is not particularly limited as long as it is a translucent and conductive material. For example, transparent inorganic oxidation such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, and zinc oxide is possible. , PEDOT: PSS, conductive polymer such as polyaniline and conductive polymer doped with any acceptor, conductive light transmissive material such as carbon nanotube, thin film metal, metal nanowire formed in thin film, these Can be mentioned. Here, the anode 2 can be formed by, for example, a sputtering method, a vacuum deposition method, a coating method, or the like.
Although the thickness of the anode 2 is not specifically limited, For example, it is 10-2000 nm, Preferably it is 50-1000 nm. When the thickness is less than 10 nm, the sheet resistance of the anode 2 increases. When the thickness is more than 2000 nm, the flatness of the organic layer 3 cannot be maintained, and the transmittance of the anode decreases.

The organic layer 3 may include a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, and the like in addition to a light emitting layer made of an organic EL material. As a material of the light emitting layer, any material known as a material for an organic EL element can be used.
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. As such an electron injection layer, a material that injects electrons into the organic layer 3 with a lower electric field strength is preferable. However, the material to be formed is not particularly limited as long as it can perform the above-described function. Any one can be selected and 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.
Although the thickness of the organic layer 3 is not specifically limited, For example, it is 50-2000 nm, Preferably it is 100-1000 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 light emitting layer, and it is preferable to use a material made of a metal, an alloy, a conductive compound, or a mixture thereof having a small work function. It is preferable to use a work function of 1.9 eV or more and 5 eV or less so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level 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 having an Otto type arrangement. Therefore, the same anode material as described above can be used.
Although the thickness of the cathode 4 is not specifically limited, For example, it is 30 nm-1 micrometer, Preferably it is 50-500 nm. If the thickness is less than 30 nm, the sheet resistance increases and the driving voltage increases. If the thickness is more than 1 μm, heat and radiation damage during film formation and mechanical damage due to film stress accumulate in the electrode and the organic layer.

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

The material of the low refractive index layer 5 is not particularly limited as long as it is a material having a refractive index lower than that of the organic layer 3. For example, when the average refractive index of all the layers of the organic layer 3 is 1.72. 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. Organic fluorine compounds, silicon dioxide (SiO ₂ (typical refractive index 1.45)), various low-melting-point 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 5 is preferably made of a material having a refractive index smaller by 0.2 or more than at least one of the cathode 4 and the organic layer 3. This corresponds to the high refractive index medium in which the cathode 4 and the organic layer 3 are of the Otto type arrangement, and the low refractive index medium (low refractive index layer 5) and the high refractive index medium (of the cathode 4 and the organic layer 3) in the Otto type arrangement. If the refractive index difference of at least one of the above is 0.2 or more, the in-plane component of the wave number of the SPP mode light is small, so that the propagation curve of the cathode 4 or the organic layer 3 and the dispersion curve of the SPP mode light intersect. This is because the SPP mode light is more efficiently extracted to the cathode 4 or the organic layer 3.

  The thickness of the low refractive index layer 5 is preferably 20 nm to 300 nm. If the thickness is less than 20 nm, the film thickness of the low refractive index layer 5 is too thin, so that the metal layer 6 and the organic layer 3 or the cathode 4 come close to increase the wave number of the SPP mode light, and the dispersion curve is in the organic layer 3. It does not intersect with the dispersion curve of propagating light, and SPP mode light is difficult to be extracted into the organic layer. If it is thicker than 300 nm, the SPP mode electromagnetic field does not reach the metal layer 6 and SPP mode light is not easily extracted into the organic layer. Furthermore, the thickness of the low refractive index layer 5 is more preferably 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 film 6, it is sufficient that the emitted light generated in the organic layer 3 can be reflected to the anode side, so that almost any single metal or alloy can be used, but the real part of the relative complex dielectric constant is absolutely A material having a large negative value is preferable. Examples of such materials include simple substances such as Au, Ag, Cu, Zn, Al, Mg, alkali metals and alkaline earth metals, alloys of Au and Ag, alloys of Ag and Cu, and alloys such as brass. It is done. Further, the metal layer 6 may have a laminated structure of two or more layers.
Although the thickness of the metal layer 6 is not specifically limited, For example, it is 20-2000 nm, Preferably it is 50-500 nm. If it is thinner than 20 nm, the reflectance is lowered and the front luminance is lowered. If it is thicker than 2000 nm, heat, radiation damage, and mechanical damage due to film stress during film formation accumulate in the electrode and the organic layer.

The high refractive index layer 7 is made of a material having a refractive index higher than that of the substance adjacent to the surface opposite to the anode 2 and higher than that of the low refractive index layer 5. In the example shown in FIG. 1, since the substance whose high refractive index layer 7 is adjacent to the surface opposite to the anode 2 is the substrate 1, the high refractive index layer 7 is made of a material having a higher refractive index than the substrate 1. In the case of a top emission type element, when the material adjacent to the surface opposite to the anode 2 of the high refractive index layer is air, the high refractive index layer 7 has a higher refractive index than air and the low refractive index layer. It can be made of a material having a refractive index higher than 5.
By having a refractive index of the high refractive index layer 7 higher than that of the material of the substrate 1 and higher than that of the low refractive index layer 5, the substrate is viewed from the outer surface side (upward in the drawing) in a sectional view. The light incident on the convex portion 7a, which is convex, is refracted toward the substrate side. As a result, the incident angle of light on the substrate 1 changes to a small angle, so that the light that does not totally reflect on the outer surface of the substrate. In addition, the substrate mode light is suppressed. Similarly, in the case of a top emission type element, it is possible to direct light in a direction nearly perpendicular to the element surface.
The refractive index of the high refractive index layer 7 is preferably the same as or higher than the refractive index of the organic layer 3. With such a refractive index structure, the SPP mode light and the emitted light re-radiated into the organic layer are extracted into the high refractive index layer without being totally reflected at the anode / high refractive index layer interface.

The material of the high refractive index layer 7 is translucent and higher than the substance adjacent to the surface of the high refractive index layer 7 opposite to the anode 2 (the material adjacent to the substrate side), and the low refractive index layer 5. The material is not particularly limited as long as it has a higher refractive index.
For example, when the material adjacent to the substrate side is a glass substrate (typical refractive index: 1.52) and the refractive index of the low refractive index layer is lower than that of glass, the material of the high refractive index layer 7 is, for example, refractive SOG having a refractive index higher than 1.52 (typical refractive index: 1.6 to 2.0), magnesium oxide (MgO) (typical refractive index: 1.74), zinc oxide (ZnO) (typical Refractive index: 2.02) and other oxides, nitrides such as aluminum nitride (AlN), oxynitrides such as aluminum oxynitride (AlON) and silicon oxynitride, polyethylene naphthalate ( A polymer compound resin such as PEN (typical refractive index: 1.77)) or melamine resin can be selected and used. In addition, a porous material, a mixture thereof, or a material in which fine particles of an inorganic material are dispersed in a transparent medium can be used.
Further, when the refractive index of the material adjacent to the substrate side or the low refractive index layer 5 is lower than 1.52, the refractive index of the high refractive index layer 7 is the same as or lower than the refractive index of the substrate. For example, metal halides such as magnesium fluoride (MgF ₂ ) (typical refractive index: 1.38), polytetrafluoroethylene (PTFE (typical refractive index: 1.35)). It can also be selected from fluorine resins such as polymethyl methacrylate (typical refractive index: 1.49), silica (SiO ₂ ) (typical refractive index: 1.45), and the like.

  The high refractive index layer 7 may be composed of a plurality of layers. For example, in the organic EL element 10 of FIG. 1, the high refractive index layer 7 has a plurality of convex portions 7a and a layered portion 7b. The convex portion 7a and the layered portion 7b may be made of the same type of high refractive index material or different types of high refractive index material. When the refractive index of the layer part 7b and the convex part 7a differs, it is preferable that the refractive index of the layer part 7b is lower than the refractive index of the convex part 7a. The light emitted from the organic layer 3 passes through the layered portion 7b and the convex portion 7a in this order, and is extracted outside the device. Therefore, if the refractive index of the layered portion 7b is lower than that of the protruding portion 7a, total reflection at the interface between the protruding portion 7a and the layered portion 7b can be suppressed, and light can be extracted efficiently. The plurality of convex portions 7a are discretely arranged in the substrate 1 as shown in FIG.

The convex portion 7a is composed of a columnar portion 7a1 and a tip portion 7a2 in order from the anode side. FIG. 2 is a schematic cross-sectional view schematically showing the cross-sectional shape of the convex portion 7 a cut by a plane in the width direction perpendicular to the anode 2.
The columnar portion 7a1 only needs to stand upright with respect to the anode 2, and the shape thereof is not particularly limited, and examples thereof include a cylinder, a quadrangular column, and a triangular column. An example of a plan view viewed from the normal direction of the element surface is shown in FIG. Although there is no restriction | limiting in particular as planar shape of the columnar part 7a1 of the convex part 7a, For example, as shown to Fig.3 (a), the convex part 7a exists in dot shape, and the dot shape is circular, elliptical, and oval. 3, a triangle, a square, a rectangle, a quadrangle, a polygon, or a shape obtained by combining these, or a convex portion 7 a as shown in FIG. 3B exists in a plurality of lines, and the line shape is a straight line. It may be a shape such as a shape, a bent shape, a curved shape, or a ring shape (donut shape). Examples include a planar shape combining a dot shape and a line shape.
The tip portion 7a2 has a top on the substrate 1 side (opposite side to the anode 2) and may have an inclined surface inclined toward the top, and the shape is not particularly limited. The inclined surface may be a flat surface or a curved surface, and examples thereof include a semicircle, a triangle, a shape having a triangular recess, a trapezoid, etc., as shown in FIG.
Although there is no restriction | limiting in particular as arrangement | positioning of the convex part 7a, When a planar shape as shown in FIG. 4 is a line shape with a dot shape or a finite length (a line does not extend to the edge part of an element), it is a surface. They may be arranged periodically such as a square lattice, a hexagonal lattice, or a rectangular lattice in the inward direction, or they may be arranged aperiodically. In the case of a line shape, an array in which adjacent convex portions are extended so as to be parallel to each other, an array in which annular lines having different diameters are arranged concentrically, and a plurality of corrugations and bent lines do not overlap each other. May be arranged in In the line shape, the lines may intersect or branch. For example, the lines may be arranged in a lattice network in the plane.
If the convex part 7a is formed in a one-dimensional line shape, it is preferable that defects are not easily generated when a plurality of convex part shapes are formed by machining or the like. On the other hand, if the projections 7a are formed in a two-dimensional manner in the form of dots that are two-dimensionally arranged in a square lattice or hexagonal lattice in the in-plane direction, the re-radiated light propagating in any direction in the plane can be extracted equally. It is more preferable.

  The height of the columnar part 7a1 (h1 in FIG. 2) is preferably 0.3 to 500 μm. Moreover, it is more preferable that it is 0.5-100 micrometers. Furthermore, it is more preferable that it is 1-50 micrometers. The columnar portion 7 a 1 directs the light emitted from the organic layer 3 in a direction nearly perpendicular to the anode 2 by a side surface perpendicular to the anode 2. When the height of the columnar portion 7a1 is 0.3 μm or less, there are few side surfaces perpendicular to the anode 2, and light cannot be directed efficiently. If the thickness is 500 μm or more, the thickness of the high refractive index layer 7 is too thick, so that it is difficult to make the interface between the high refractive index layer 7 and the anode 2 flat, and it is difficult to produce a structure. If the height of the columnar portion 7a1 is too high, the distance that light is guided through the high refractive index layer 7 before the light reaches the surface of the convex portion 7a and is refracted is attenuated. This is because light extraction cannot be realized.

Moreover, it is preferable that the width | variety (W1 in FIG. 2) of the columnar part 7a1 is 0.3-500 micrometers. Moreover, it is more preferable that it is 0.5-100 micrometers. Furthermore, it is more preferable that it is 1-50 micrometers. Here, when the planar shape of the columnar portion 7a1 is a dot shape as shown in FIG. 3A, the width of the columnar portion 7a1 is the diameter of the maximum inscribed circle of the planar shape of the columnar portion 7a1. For example, when the planar shape is an ellipse, the maximum inscribed circle is a circle whose diameter is the minor axis of the ellipse. In this case, the width of the columnar portion 7a1 is equal to the length of the minor axis. 3B, the width of the columnar portion 7a1 is obtained by averaging the inscribed circle diameters of the planar shape of the columnar portion 7a1 in the length direction. For example, when the planar shape is a linear locus having an uneven thickness in the length direction, the width of the columnar portion 7a1 takes a value between the maximum value and the minimum value of the thickness.
When the width of the columnar portion 7a1 is 0.3 μm or less, the width of the columnar portion 7a1 is about the effective wavelength of light in the high refractive index layer 7 or smaller than that, and therefore the columnar portion 7a1 from the inside of the high refractive index layer 7. The light incident on the side surface of the diffracted light is diffracted and spreads in a cylindrical wave shape, and the refraction effect cannot be obtained sufficiently. On the other hand, if it is 500 μm or more, the probability that the light guided in-plane through the high refractive index layer 7 will reach the side surface of the columnar part 7a1, which is the refractive index interface, becomes small, and the light cannot be directed efficiently.

  Furthermore, the height of the tip 7a2 (h2 in FIG. 2) is preferably 0.05 to 5 times the width of the bottom surface (W2 in FIG. 2). Further, it is more preferably 0.1 to 2 times. Further, it is more preferably 0.2 to 1 times. Here, when the planar shape of the tip portion 7a2 is a dot shape as shown in FIG. 3A, the width of the bottom surface of the tip portion 7a2 is the diameter of the maximum inscribed circle of the planar shape of the bottom surface of the tip portion 7a2. is there. For example, when the planar shape is an ellipse, the maximum inscribed circle is a circle whose diameter is the minor axis of the ellipse. In this case, the width of the bottom surface of the tip 7a2 is equal to the length of the minor axis. Further, in the case of a line shape as shown in FIG. 3B, the width of the bottom surface of the tip portion 7a2 is obtained by averaging the inscribed circle diameter of the planar shape of the bottom surface of the tip portion 7a2 in the length direction. . For example, when the planar shape is a linear locus having a nonuniform thickness in the length direction, the width of the bottom surface of the tip end portion 7a2 takes a value between the maximum value and the minimum value of the thickness. When the height of the tip portion 7a2 is 0.05 times or less the width of the bottom surface, the light incident on the surface of the tip portion 7a2 from the inside of the high refractive index layer 7 is totally reflected at substantially the same angle with respect to the normal line of the substrate. Since light continues to propagate through the high refractive index layer 7, light cannot be extracted efficiently. On the other hand, if the height of the tip 7a2 is 5 times or more the height of the bottom, the inclined surface of the tip 7a2 becomes steep, making it difficult to form a structure.

(Organic EL element (2nd Embodiment))
FIG. 5B is a schematic perspective view for explaining the organic EL element according to the second embodiment.
The organic EL element 20 according to the second embodiment of the present invention includes an anode (first electrode) 12, an organic layer 13 including a light emitting layer, and a cathode (second electrode) 14 in this order on a substrate 11. The EL device further comprises a low refractive index layer 15 and a metal layer 16 on the surface of the cathode 14 opposite to the organic layer 13 in order from the side in contact with the opposite surface. The refractive index of the low refractive index layer 15 is lower than the refractive index of the organic layer 13, and the high refractive index layer 17 is provided on the substrate 11 side (the surface opposite to the organic layer 13) of the anode 12. The high refractive index layer 17 has a refractive index higher than that of the substrate 11 (a material in which the high refractive index layer 17 is adjacent to the surface opposite to the first electrode) and a refractive index higher than that of the low refractive index layer 15. The high refractive index layer 17 made of a material has a plurality of recesses 17a, and the recesses 17a are columnar holes 17a1. The columnar hole 17a1 is perforated perpendicular to the anode (first electrode) 12, and the root 17a2 is formed on the substrate 11 side of the columnar hole 17a1 (on the side opposite to the first electrode). And having an inclined surface extending toward the opposite side of the first electrode.
As described above, when comparing the refractive indexes of the structure on the cathode side, the refractive index of the organic layer means the average refractive index of all the layers including the light emitting layer made of the organic EL material.

  The materials, thicknesses, formation methods, and the like of the substrate 11, the anode 12, the organic layer 13, the cathode 14, the low refractive index layer 15, and the metal layer 16 are the same as those of the substrate 1, the anode 2, the organic layer 3, and the first embodiment. The same materials, thicknesses, formation methods and the like of the cathode 4, the low refractive index layer 5, and the metal layer 6 can be used.

  The material of the high refractive index layer 17 can be the same as that of the high refractive index layer 7 of the first embodiment.

  The high refractive index layer 17 has a plurality of recesses 17a. The plurality of recesses 17a are arranged in the high refractive index layer 17 as shown in FIG. Further, when the roots 17a2 of the adjacent recesses 17a are in contact with each other, a cross section similar to that of FIG. 1 is obtained as a cut surface at the surface passing through the contact part and having the maximum width of the recess 17a.

The concave portion 17a includes a columnar hole portion 17a1 and a root portion 17a2 in order from the anode side. FIG. 6 is a schematic cross-sectional view schematically showing a cross-sectional shape when the concave portion 17a is cut along a plane in the width direction perpendicular to the anode.
The columnar hole 17a1 only needs to be drilled perpendicularly to the anode 12, and the shape thereof is not particularly limited, and examples thereof include a cylinder, a quadrangular column, and a triangular column. The example of the top view seen from the normal line direction of the element surface is shown. The columnar hole 17a1 of the recess 17a is not particularly limited as a planar shape. For example, a circular shape, an elliptical shape, an oval shape, a triangular shape, a square shape, a rectangular shape, a rectangular shape, or a polygon shape as shown in FIG. The planar shape etc. are mentioned.
The root portion 17a2 only needs to have an inclined surface that expands toward the substrate 11 (on the side opposite to the first electrode), and the shape thereof is not particularly limited. For example, a shape like FIG. 6 is mentioned. The inclined surface may be flat or curved.
Although there is no restriction | limiting in particular as arrangement | positioning of the recessed part 17a, In addition to the case where it arranges in a square lattice shape, a hexagonal lattice shape, a rectangular lattice shape, etc. in the in-plane direction as shown in FIG. It may be a line arrangement arranged in parallel, a concentric line arrangement arranged concentrically, or the like. Moreover, the structure arrange | positioned periodically or the structure arrange | positioned aperiodically may be sufficient.

  The depth of the columnar hole 17a1 (h11 in FIG. 6) is preferably 0.3 to 500 μm. Moreover, it is more preferable that it is 0.5-100 micrometers. Furthermore, it is more preferable that it is 1-50 micrometers. The columnar hole portion 17 a 1 directs light emitted from the organic layer 13 in a direction almost perpendicular to the anode 12 by a side surface perpendicular to the anode 12. If the depth of the columnar hole 17a1 is 0.3 μm or less, there are few side surfaces perpendicular to the anode 12, and light cannot be directed efficiently. On the other hand, when the thickness is 500 μm or more, the depth of the hole to be drilled becomes deep, and it is difficult to produce a columnar hole structure with a vertical side surface. If the depth of the columnar hole portion 17a1 is too deep, the distance that light is guided through the high refractive index layer 17 until the light reaches the surface of the concave portion 17a and is refracted is attenuated while being guided. Therefore, efficient light extraction cannot be realized.

Moreover, it is preferable that the width | variety (W11 in FIG. 6) of the columnar hole part 17a1 is 0.3-500 micrometers. Moreover, it is more preferable that it is 0.5-100 micrometers. Furthermore, it is more preferable that it is 1-50 micrometers. Here, the width of the columnar hole portion 17a1 is the maximum inscribed circle diameter of the planar shape when the planar shape is a dot shape, like the width W1 of the columnar portion 7a1 of the first embodiment, and the planar shape is a line. In the case of a shape, the inscribed circle diameter of the planar shape is averaged in the length direction.
If the width of the columnar hole portion 17a1 is 0.3 μm or less, the width of the columnar hole portion 17a1 is approximately equal to or smaller than the effective wavelength of light in the high refractive index layer 17, so The light incident on the side surface of the hole 17a is diffracted and spreads in a cylindrical wave shape, and a sufficient refraction effect cannot be obtained. On the other hand, if it is 500 μm or more, the probability that the light guided in-plane through the high refractive index layer 17 will reach the side surface of the columnar hole 17a1 that is the refractive index interface becomes small, and the light cannot be directed efficiently. .

  Furthermore, it is preferable that the depth (h12 in FIG. 6) of the root portion 17a2 is 0.025 to 2.5 times the difference between the width of the root portion 17a2 (W12 in FIG. 6) and the width of the columnar hole portion 17a1. Further, it is more preferably 0.05 times to 1 time. Further, it is more preferably 0.1 to 0.5 times. Here, the width of the root portion 17a2 is the width of the bottom surface of the root portion 17a2 on the side opposite to the anode 12, and the planar shape is a dot shape like the width W2 of the bottom surface of the tip portion 7a2 of the first embodiment. Is the maximum inscribed circle diameter of the planar shape, and when the planar shape is a line shape, the inscribed circle diameter of the planar shape is averaged in the length direction. When the depth of the root portion 17a2 is 0.025 times or less of the difference between the width of the root portion 17a2 and the width of the columnar hole portion 17a1, the light enters the sidewall (inclined surface) of the root portion 17a2 from the inside of the high refractive index layer 17 Since the reflected light is totally reflected at substantially the same angle and continues to propagate through the high refractive index layer 17, the light cannot be extracted efficiently. On the other hand, when the depth of the root portion 17a2 is 2.5 times or more the difference between the width of the root portion 17a2 and the width of the columnar hole portion 17a1, the inclined surface of the root portion 17a2 becomes steep, thereby forming a structure. It becomes difficult. Further, since the distance that light is guided through the high refractive index layer 17 is increased and attenuated, efficient light extraction cannot be realized.

FIG. 5 is a schematic perspective view of the organic EL element of the present invention. FIG. 5A shows the organic EL element 10 of the first embodiment, and FIG. 5B shows the organic EL element of the second embodiment. 20. Here, in the organic EL element 10, the convex portions 7 a are scattered in an island shape in the substrate 1. That is, the board | substrate 1 is sea shape and the convex part 7a becomes an island shape. On the other hand, in the organic EL element 20, a recess 17 a is opened in an island shape in the high refractive index layer 17. That is, the high refractive index layer 17 has a sea shape and the concave portion 17a has an island shape.
The convex portion 7a shown in FIG. 5A has a refractive index interface (side surface of the columnar portion 7a1) perpendicular to the anode 2 and a refractive index interface (inclined surface of the tip portion 7a2) inclined with respect to the anode 2. doing. On the other hand, the recess 17a shown in FIG. 5B includes a refractive index interface perpendicular to the anode 12 (side surface of the columnar hole 17a1) and a refractive index interface inclined with respect to the anode 12 (inclined surface of the root portion 17a2). )have. That is, the organic EL element 10 and the organic EL element 20 have a refractive index interface that refracts the light incident from the inside of the high refractive index layer in the same direction, and have the same effect in terms of directing the light. .

これに対して、比誘電率ε_２の誘電体中を伝搬する通常の伝播光の波数の大きさは、次式（２）によって与えられる。

本発明の金属層６に用いられる金属材料においてはε_１＜０であるので、式（２）は常にＳＰＰの波数（１）より小さく、表面プラズモンポラリトン（SPP）の分散曲線は通常の伝播光の分散直線と交差しない。そのため、通常の伝播光では平坦な金属の表面にSPPを励起することはできず、また、平坦な金属の表面に存在するSPPから直接伝播光を取り出すことはできない。 (Otto type arrangement)
Next, the 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.
When the angular frequency of surface plasmon polariton (SPP) generated on a flat metal surface is ω and the wave vector is k _sp , this dispersion relationship is expressed by the real part ε ₁ of the relative dielectric constant of the metal and the surface of the metal. It is determined by the relative dielectric constant ε ₂ of the dielectric that contacts the surface and is approximately given by the following equation (1) (c is the speed of light in an optical vacuum).

On the other hand, the magnitude of the wave number of normal propagating light propagating through a dielectric having a relative dielectric constant ε ₂ is given by the following equation (2).

In the metal material used for the metal layer 6 of the present invention, since ε ₁ <0, the formula (2) is always smaller than the wave number (1) of the SPP, and the dispersion curve of the surface plasmon polariton (SPP) is normal propagation light. Does not intersect with the dispersion straight line. Therefore, normal propagating light cannot excite SPP on the surface of a flat metal, and propagating light cannot be extracted directly from SPP existing on the surface of the flat metal.

従って、ε₃が十分大きければ、入射角θを変えることにより、SPPの分散曲線と全反射によるエバネッセント波（以降、単に「エバネッセント波」という場合も、全て全反射によって生じたものをさすものとする）の分散直線に交点を持たせることが可能となる。すなわち、エバネッセント波を用いれば、有機層３中の伝播光から平坦な金属層３の表面にSPPを励起することができ、また、逆の過程として平坦な金属層６の表面に存在するSPPからエバネッセント波を介して有機層位３中へ伝播光として取り出すことが可能となる。ここで、SPPを取り出す場合は、式（３）中のθは、伝播光の放射角度ということになる。
言い換えると、所定の角度で有機層３内を伝播する光だけが、エバネッセント波を介しＳＰＰとエネルギーをやり取りできる状態となることを意味する。 On the other hand, the structure is an Otto type arrangement, that is, a metal / low refractive index medium / high refractive medium, and in the organic EL element of the present invention, the metal layer 6 (real part ε ₁ of relative dielectric constant) / low Consider a case where a laminated structure of the refractive index layer 5 (relative permittivity ε ₂ ) / organic layer 3 (relative permittivity ε ₃ ) is used. When the refractive index of the organic layer 3 is higher than the refractive index of the low refractive index layer 5, the light incident from the organic layer 3 side to the low refractive index layer 5 side at an incident angle larger than the critical angle is incident on the organic layer 3 and the cathode 4. Total reflection occurs at the interface or the interface between the cathode 4 and the low refractive index layer 5. At this time, an evanescent wave that is non-propagating light is generated on the low refractive index layer 5 side of the interface, and the electromagnetic field intensity attenuates exponentially as the distance from the interface of total reflection increases (incident light is totally reflected at the interface). However, the electromagnetic field oozes out of the interface). The dispersion curve of this evanescent wave is given by the following equation (3). Here, θ is a propagation angle with respect to the substrate normal in the organic layer 3.

Therefore, if ε ₃ is sufficiently large, by changing the incident angle θ, the dispersion curve of the SPP and the evanescent wave due to total reflection (hereinafter, even simply referred to as “evanescent wave” refers to all generated by total reflection. It is possible to give an intersection to the dispersion straight line. That is, if an evanescent wave is used, SPP can be excited from the propagating light in the organic layer 3 to the surface of the flat metal layer 3, and as a reverse process, from the SPP existing on the surface of the flat metal layer 6. It becomes possible to take out as propagating light into the organic layer level 3 via the evanescent wave. Here, when taking out SPP, (theta) in Formula (3) will be the radiation angle of propagation light.
In other words, it means that only the light propagating in the organic layer 3 at a predetermined angle can exchange energy with the SPP via the evanescent wave.

However, if the low refractive index layer 5 is too thick or too thin, the SPP mode light is not excited or extracted via the evanescent wave. This is because if the low refractive index layer 5 is too thick, the evanescent wave oozes out from the organic layer 3 does not reach the metal layer 6, and the evanescent wave and the SPP mode light cannot exchange energy. If the rate layer 5 is too thin, the metal layer 6 and the organic layer 3 or the cathode 4 approach each other, and the wave number of the SPP mode becomes larger than the equation (1), and the dispersion curve becomes the equation (3) of the dispersion curve of the evanescent wave, This is because they do not intersect at any angle θ.
As described above, the light extracted from the SPP is radiated at a predetermined angle corresponding to the intersection of the SPP dispersion curve and the evanescent wave dispersion line.

(Refraction by high refractive index layer)
Next, the effect of refraction by the high refractive index layer of the organic EL element of this embodiment will be described below. As shown in FIG. 5, the organic EL elements 10 and 20 have the same effect of extracting light to the outside by refraction, and therefore the organic EL element 10 will be described. FIG. 7 is a schematic diagram schematically showing the propagation of light with an arrow, and schematically illustrating the principle of the refractive action effect of the organic EL element, and FIG. 7A is an organic EL according to the first embodiment. FIG. 7B is a schematic diagram schematically showing the principle of the refracting effect of the element 10, and FIG. 7B shows the principle of the refracting effect of the organic EL element 30 having only the columnar portion 27a1 with the convex portion having no tip portion. It is the schematic diagram which showed typically.

  The organic EL element 10 according to the first embodiment of the present invention is refracted when propagating light in the organic layer is transmitted to the light extraction side (substrate side in the bottom emission type), and transmits the propagation angle of transmitted light (transmitted light and Transmitted light re-enters the interface of the refractive index perpendicular to or substantially perpendicular to the substrate surface (side surface of the columnar portion 7a1) and the adjacent convex portion 7a so that the angle formed by the normal of the substrate surface becomes small. Even in this case, the convex portion 7a has an inclined surface having an inclination angle with respect to the substrate surface from which light can be efficiently extracted.

As shown in FIG. 7A, in the organic EL element 10 according to the first embodiment of the present invention, a part of the light emitted at the point A of the light emitting point included in the organic layer 3 is a dipole field around the light emitting point. (Arrow A1) and energy transfer directly to the SPP (arrow A2) mode. Such energy transfer to the SPP mode is widely known to occur when a light emitting molecule and a metal layer are close to each other in a general organic EL element.
The excited SPP mode light can be emitted to the cathode 4 at a predetermined angle (arrow A4) through resonance with the evanescent wave (arrow A3) and extracted to the organic layer 3 as propagating light.
Here, since the light emitted from the point A of the organic layer 3 travels in all directions, there is naturally light traveling in a direction other than the arrow A1 in FIG. 7A, but the arrow A1 explains the effect of the present invention. In order to do so, only a part of the light propagation is schematically shown. The light indicated by the arrows A2 to A4 also only schematically shows the propagation of part of the light.
In addition, refraction occurs at interfaces having different refractive indexes, but the refraction action is not shown in the drawing for interfaces that are not particularly necessary for explaining the effects of the present invention.

The light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to the point B of the organic layer 3 propagates as shown by arrow B1 and is extracted to the substrate 1.
That is, the light B1 traveling from the point B through the organic layer 3 or the like is refracted at the interface between the organic layer 3 and the anode 2, passes through the anode 2, and is refracted at the interface between the anode 2 and the high refractive index layer 7. Then, the light advances through the high refractive index layer 7 and is refracted in a direction near the substrate at the side surface of the columnar portion 7a1 of the high refractive index layer 7.
Here, a part of the refracted light can be extracted to the outside through the substrate 1, but the rest is incident again on the convex portion 7a of the adjacent high refractive index layer (arrow B2). This light passes through the inside of the convex portion 7a (arrow B3), is rerefracted at the interface between the tip portion 7a2 and the substrate, passes through the substrate 1 (arrow B4), and is extracted outside.

  On the other hand, in the organic EL element 30, the propagation light in the organic layer is refracted to the light extraction side (the substrate side in the bottom emission type), and the incident angle to the interface (the angle formed by the incident light and the normal line of the incident interface). Is a structure having only a refractive index interface (a side surface of the columnar portion 27a1) that is perpendicular or nearly perpendicular to the substrate surface.

FIG. 7B schematically shows a light path of the organic EL element 30 that does not have a tip on the convex portion. Of the light emitted from the light emitting point A included in the organic layer 23, the light incident on the cathode 24 is extracted up to the point B, and the light is further projected from the columnar portion 27a1 of the high refractive index layer 27 to the substrate. The process is the same as that of the organic EL element 10 until the light is refracted in a direction near the vertical direction.
Here, part of the refracted light reenters the columnar portion 27a1 of the adjacent high refractive index layer 27 (arrow B′2). This light passes through the inside of the columnar portion 27a1 (arrow B′3) and is reflected at the upper end of the columnar portion 27a1 (arrow B′4). Since the incident angle of the arrow B′3 and the reflection angle of the arrow B′4 are the same, this light is confined inside the device again as shown in FIG.

  That is, the organic EL element 30 can extract most of the light emitted from the light emitting point included in the organic layer 23 by the columnar structure through the refractive index interface perpendicular to the substrate, but part of the light is guided through the organic EL element. And cannot be taken out. On the other hand, the organic EL element 10 of the present invention has a tip portion at the convex portion, and the tip portion has an inclined surface, so that the organic EL element 30 cannot be taken out by the organic EL element 30 at the upper end. Light that is reflected and re-enters the element can also be efficiently extracted outside the substrate.

(Image display device)
Next, an image display apparatus provided with the above organic EL element will be described. Since the image display devices including the organic EL elements 10 and 20 are the same as each other, the organic EL element 10 will be described.
FIG. 8 is a diagram illustrating an example of an image display device including the organic EL element.
The image display device 100 shown in FIG. 8 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 are provided.

  In the present embodiment, a plurality of anode wirings 104 are formed on the substrate 1 of the organic EL element 10. The anode wirings 104 are arranged in parallel at a constant interval. The anode wiring 104 is made of a transparent conductive film, and for example, ITO 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 formed of, for example, a metal film having a thickness of 500 nm to 600 nm.

  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, for example, 200 nm to 1000 nm, and the size of the opening 120 can be, for example, 100 μm × 100 μm.

  The organic EL element 10 is located between the anode wiring 104 and the cathode wiring 108 in the opening 120. In this case, the anode 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 150 nm to 200 nm, for example.

  On the insulating film 110, a plurality of cathode partition walls 112 are formed along a direction perpendicular to the anode wiring 104. The cathode partition 112 plays a role for spatially separating the plurality of cathode wirings 108 so that the wirings of the cathode wirings 108 do not conduct with each other. Accordingly, the cathode wiring 108 is disposed between the adjacent cathode partition walls 112. As the size of the cathode partition 112, for example, 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 air. As the sealing plate 116, for example, a glass substrate having a thickness of 0.7 mm to 1.1 mm can be used. 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, when light is extracted from the sealing plate 116 side as in the case of the top emission type, the sealing plate 116 needs to be transparent to at least a part of the 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, a lighting device using the organic EL element will be described. Since the image display devices including the organic EL elements 10 and 20 are the same as each other, the organic EL element 10 will be described.
FIG. 9 is a diagram illustrating an example of an illumination device including the organic EL element 10 described above.
The lighting device 200 shown in FIG. 9 includes the organic EL element 10 described above, and a terminal 202 that is installed adjacent to the substrate 1 (see FIG. 1) of the organic EL element 10 and connected to the anode 2 (see FIG. 1). The terminal 203 is connected to the cathode 4 (see FIG. 1), and the lighting circuit 201 is connected to the terminal 202 and the terminal 203 to drive the organic EL element 10.

  The lighting circuit 201 has a DC power source (not shown) and a control circuit (not shown) inside, and supplies a current by applying a voltage between the anode layer 2 and the cathode 4 of the organic EL element 10 through the terminal 202 and the terminal 203. To do. Then, the organic EL element 10 is driven, the light emitting layer emits light, the light is emitted through the substrate 1, and used as illumination light. The light emitting layer may be made of a light emitting material that emits white light, and each of the organic EL elements 10 using light emitting materials that emit green light (G), blue light (B), and red light (R). A plurality of them may be provided so that the combined light is white.

(First manufacturing method of organic EL element)
Below, the 1st manufacturing method of the organic EL element of this invention is demonstrated using FIG. FIG. 10 is a schematic cross-sectional view showing a first manufacturing method of the organic EL element of the present invention. Further, the first manufacturing method is limited to the case where the shape of the tip portion is a lens-like curved surface.

First, in order to form the hole 1h in the substrate 1, for example, a method using photolithography can be used. In order to do this, as shown in FIG. 10A, a positive resist solution is applied on the substrate 1, and the excess resist solution is removed by spin coating or the like to form a resist layer R.
Then, when a mask (not shown) on which a predetermined pattern for forming the hole 1h is drawn is applied and exposure is performed with ultraviolet rays (UV), electron beams (EB), etc., the hole 1h is formed in the resist layer R. A predetermined pattern corresponding to is exposed. Then, the resist layer R in the exposed pattern portion is removed using a developer. Thus, the surface of the substrate 1 is exposed corresponding to the exposed pattern portion (FIG. 10B).

  Next, as shown in FIG. 10C, using the remaining resist layer R as a mask, the exposed portion of the substrate 1 is removed by etching to form a hole 1h. As the etching, either dry etching or wet etching can be used. In this case, the shape of the hole 1h can be controlled by combining isotropic etching and anisotropic etching. As the dry etching, various methods such as reactive ion etching (RIE) can be used. As wet etching, a method of immersing in metal salts such as iron chloride, aqua regia, dilute hydrochloric acid, dilute sulfuric acid, hydrofluoric acid, and oxalic acid can be used.

A spin-on dielectric precursor S or a curable resin precursor U is injected into the hole 1h thus formed (FIG. 10D). The spin-on dielectric is a liquid that has a viscosity at the coating stage of the precursor S and becomes a solid dielectric having an insulating property by being converted after coating, and a known one may be used. it can. An example is spin-on-glass that forms silicon oxide after conversion. The curable resin may be cured after application of the precursor U, and various thermosetting resins, photocurable resins, and the like can be used.
As a method for injecting the precursor S or U, various wet processes such as spin coating, bar coating, slit coating, die coating, and spray coating for generally applying a flat film can be used. When a flat film is applied on the substrate 1 having the hole 1h, the spin-on dielectric is naturally injected into the hole 1h by surface tension.
As shown in FIG. 10D, the injected precursor S or U is lifted at a portion close to the side wall of the hole by surface tension to form an arcuate curved surface.

Next, the injected precursor material is solidified (FIG. 10E).
In the case of a spin-on dielectric, as a method for solidifying the precursor S, methods such as heating, exposure to an oxygen gas plasma atmosphere, exposure to hydrogen peroxide, and the like can be used. Among them, conversion by heating is preferable because it can be easily performed and no special equipment is required.
In the case of a curable resin, heating, light irradiation, or the like can be used as a method for solidifying the precursor U. The resin is polymerized and cured by light or thermal polymerization reaction.

Here, it is preferable that the refractive index of the solidified dielectric 1s (a dielectric obtained by converting a spin-on dielectric or a resin obtained by curing a curable resin (dielectric)) is equal to or lower than the refractive index of the substrate 1. If the dielectric 1s after solidification is equal to or lower than the refractive index of the substrate 1, total reflection at the interface between the dielectric 1s after solidification and the substrate 1 can be suppressed.
The solidified dielectric 1s preferably has the same refractive index as that of the substrate 1. If the solidified dielectric 1s and the substrate 1 have the same refractive index, unnecessary light reflection at the interface between the solidified dielectric 1s and the substrate 1 can be suppressed.
Furthermore, it is preferable that the dielectric 1s after solidification after conversion is solidified to the same material as the substrate 1. If the solidified dielectric 1 s is made of the same material as the substrate 1, the interface with the substrate 1 does not exist and adhesion and the like are improved.

  Next, the high refractive index layer 7 is formed on the substrate 1 having the hole 1h (FIG. 10F). The high refractive index layer 7 can be formed by a conventionally known method and is not particularly limited. For example, a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method can be used. Further, in order to flatten and smooth the interface with the anode 2 to be formed later, the surface of the formed high refractive index layer 7 may be etched back or polished.

  In the case of top emission, the substrate 1 and the high refractive index layer 7 are peeled off. Therefore, the refractive index of the dielectric 1s after solidification is not particularly limited. In order to facilitate peeling, it is preferable to apply a release agent before forming the high refractive index layer 7. As the release agent, a fluorine release agent, a silicon release agent, or the like can be used. For applying the release agent, a generally used spin coating method, dipping method, spraying method, or the like can be used.

Next, the anode 2, the organic layer 3, the cathode 4, the low refractive index layer 5, and the metal layer 6 are laminated in this order on the high refractive index layer 7 (FIG. 10 (g)).
Although the formation method of the anode 2 is not specifically limited, For example, resistance heating vapor deposition method, electron beam vapor deposition method, sputtering method, ion plating method, CVD method etc. can be used. By performing the surface treatment of the anode 2 after forming the anode 2, the performance of the overcoated layer (adhesion with the anode 2, surface smoothness, reduction of hole injection barrier, etc.) can be improved. . The surface treatment includes high-frequency plasma treatment, sputtering treatment, corona treatment, UV ozone irradiation treatment, ultraviolet irradiation treatment, oxygen plasma treatment, and the like.

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

  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 Japanese Patent Application Laid-Open No. 2006-303412. In addition, a method of forming a film of a single metal, a metal oxide, a metal nitride, or the like can be given. 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.

A conventionally known method can be used to form the organic layer 3 and is not particularly limited. For example, a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method can be used.
Here, in the case where the surface of the anode 2 serving as a base on which the organic layer 3 is formed is uneven, a polishing process, an etching process, or the like for flattening may be appropriately performed.

  The cathode 4 can be formed by the same method as 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 is used. Can do.

Although the formation method of the low refractive index layer 5 is not specifically limited, For example, resistance heating vapor deposition method, electron beam vapor deposition method, sputtering method, ion plating method, CVD method etc. 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.

  Although the formation method of the metal layer 6 is not specifically limited, For example, a vapor deposition method and sputtering can be used.

  The organic EL element 10 can be manufactured by the above process. Moreover, after these series of processes, it is preferable to use the organic EL element 10 stably for a long period of time and to attach a protective layer and a protective cover (not shown) for protecting the organic EL element 10 from the outside. As the protective layer, polymer compounds, metal oxides, metal fluorides, metal borides, silicon compounds such as silicon nitride and silicon oxide, and the like can be used. And these laminated bodies can also be used. 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. The protective cover is preferably bonded to the substrate 1 with a thermosetting resin or a photocurable resin and sealed. In this case, it is preferable to use a spacer because a predetermined space can be maintained and the organic EL element 10 can be prevented from being damaged. If an inert gas such as nitrogen, argon, or helium is sealed in this space, it becomes easy to prevent 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.

(Second manufacturing method of organic EL element)
Below, the 2nd manufacturing method of the organic EL element of this invention is demonstrated using FIG. FIG. 11 is a schematic cross-sectional view showing a second manufacturing method of the organic EL element of the present invention. In addition, unlike the first manufacturing method, the second manufacturing method can arbitrarily set the shape of the tip.

First, as shown in FIG. 11A, the precursor S or U is applied on the substrate 1. As the precursor S or U, the same one as in the first manufacturing method can be used.
As the coating method, various wet processes such as spin coating, bar coating, slit coating, die coating, and spray coating for generally coating a flat film can be used.
At the same time, irregularities are formed on the surface of the mold M. For the processing, lithography, machining such as cutting or polishing, laser processing, or the like can be used. The concavo-convex shape has the same shape as the tip portion 7a2 of the high refractive index layer 7, and may be a curved shape like a lens or a polygonal shape.
For the mold M, for example, a metal such as stainless steel, titanium, or nickel, or a non-metal such as silicon or resin can be used.

  Next, as shown in FIG. 11B, the uneven shape of the mold M is imprinted on the coating film of the precursor S or U by pressing the mold M against the precursor S or U. Further, the precursor S or U may be applied on the mold M without imprinting.

  Further, the curable resin precursor S or U on the mold M is solidified. As the solidification method, the same method as the first manufacturing method can be used. The refractive index of the dielectric 1s after solidification is preferably equal to or lower than the refractive index of the substrate 1. The solidified dielectric 1s preferably has the same refractive index as that of the substrate 1. More preferably, the solidified dielectric 1s and the substrate 1 are made of the same material. By adjusting the refractive index and the material, unnecessary reflection can be suppressed as described above, and adhesion and the like can be improved.

  After solidification, as shown in FIG. 11C, the mold M is peeled from the dielectric 1s after solidification. In order to facilitate the peeling of the mold M, it is preferable to apply a release agent to the surface of the coating film or the surface of the mold M before pressing the mold M. As the release agent, a fluorine release agent, a silicon release agent, or the like can be used. For applying the release agent, a generally used spin coating method, dipping method, spraying method, or the like can be used.

  After removing the mold M, the concave portion formed by imprinting is filled with a high refractive index dielectric having a higher refractive index than the cured dielectric 1s to form the tip 7a2 (FIG. 11D). A conventionally known method can be used to form the tip portion 7a2, and it is not particularly limited. For example, a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method can be used. The high refractive index dielectric formed on the flat surface other than the recess can be removed by etch back or polishing. Further, a mask may be used so that the high refractive index layer 7 is not formed on the flat portion.

  Next, a structure 1p made of a dielectric having an opening 1k whose side wall is perpendicular to the substrate plane is formed on the flat surface of the solidified dielectric 1s (FIG. 11E). The structure 1p may be formed by using a resist formed on the tip 7a2 as a mask and laminating a dielectric film thereon, or formed on the tip 7a2 after laminating a flat dielectric film. The flat film may be removed by photolithography or the like. At this time, the refractive index of the structure 1p is preferably equal to or lower than the refractive index of the dielectric 1s after solidification, and more preferably has the same refractive index as that of the dielectric 1s after solidification. More preferably, the structure 1p and the solidified dielectric 1s are made of the same material.

  Next, a columnar portion 7a1 made of the same material as the tip portion 7a2 is formed on the opening 1k formed in the structure 1p (FIG. 11 (f)). The high refractive index layer 7 can be formed by a conventionally known method and is not particularly limited. For example, a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method can be used. Further, in order to flatten and smooth the interface with the anode 2 to be formed later, the surface of the formed high refractive index layer 7 may be etched back or polished. Further, when the columnar portion 7a1 is formed, the layered portion 7b made of the same material as the columnar portion 7a1 may be formed on the exposed surface of the structure 1p. The columnar portion 7a1, the tip portion 7a2, and the layered portion 7b constitute a high refractive index layer 7.

  In the case of top emission, the high refractive index layer 7 is peeled off from the solidified dielectric 1s and structure 1p. Therefore, the refractive index of each layer is not particularly limited. In order to facilitate peeling, it is preferable to apply a release agent to the surfaces of the solidified dielectric 1s and structure 1p before forming the high refractive index layer 7. As the release agent, a fluorine release agent, a silicon release agent, or the like can be used. For applying the release agent, a generally used spin coating method, dipping method, spraying method, or the like can be used.

  On the high refractive index layer 7, the anode 2, the organic layer 3, the cathode 4, the low refractive index layer 5, and the metal layer 6 are laminated | stacked in order (FIG.11 (g)). As a forming method, a method similar to the first manufacturing method can be used.

The imprinting method using the mold M can also be used as a method for forming the recesses 17 a in the high refractive index layer 17 of the organic EL element 20.
For example, as a method of manufacturing the top emission type organic EL element 20, first, the metal layer 16, the low refractive index layer 15, the cathode 14, the organic layer 13, and the anode 12 are sequentially laminated on the substrate 11 ′. As a forming method, a method similar to the first manufacturing method can be used.
Next, a spin-on dielectric material or a curable resin precursor having a refractive index after solidification higher than that of the low refractive index layer 15 is applied onto the anode 12.
Moreover, the uneven | corrugated shape which consists of several recessed part 17a is formed in the coating film surface of a precursor by forming the unevenness | corrugation which consists of the reverse shape of several recessed part 17a on the surface of the mold M, and pressing this mold M against the coating film surface of a precursor Imprint. Then, the organic EL element 20 can be manufactured by solidifying the precursor. The method similar to the above can be used for the method of forming an uneven shape on the surface of the mold M, the method of imprinting, and the method of solidifying the precursor.

  Through the above steps, the organic EL elements 10 and 20 can be manufactured. Further, after these series of steps, it is preferable to use the organic EL elements 10 and 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 elements 10 and 20 from the outside. . As the protective layer and the protective cover, the same protective layer and protective cover as in the first manufacturing method can be used.

(SPP extraction in Otto type arrangement)
The film thickness of the low refractive index layer capable of taking out the SPP captured 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. 12 shows the result of energy dissipation calculation that develops the intensity of light emitted from the organic layer with the wave number component in the organic EL element surface direction for the organic EL element 40 having the standard structure. Horizontal axis, an organic EL element plane direction component of the wavenumber of the light emitted from the organic layer divided by the wave number k ₀ in a vacuum, i.e. the effective refractive index, and the vertical axis the intensity of the light of the wave number, i.e. The expansion 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 having a standard structure in which an anode 32, an organic layer 33, and a cathode 34 (metal) each having a flat layer are stacked on a substrate 31 (glass). In this case, the peak area on the highest wavenumber side of the TM polarized light with respect to the total integrated area of the TM / TE polarized light component represents the intensity ratio of the SPP mode light, but most of the light emitted from the organic layer 33 is SPP mode light. As you can see it is captured. In the organic EL element shown in FIG. 12, the film thicknesses of the anode 32 and the organic layer 33 are 150 nm and 100 nm, respectively.

On the other hand, in the organic EL element 50 (see FIG. 14) having the Otto type arrangement, the dependence of the intensity of the light emitted from the organic layer (TM polarization component) by the energy dissipation calculation due to the film thickness of the low refractive index layer 45 is shown. The figure shown is shown in FIG. An organic EL element 50 which is an example of an organic EL element having an Otto type arrangement has a substrate 41, an anode 42, and an organic layer 43 having the same configuration as the element 40 of FIG. 12, but a transparent conductive material on the organic layer 43. A cathode 44 (50 nm) made of ITO is formed, and a low-refractive index layer 45 and a metal layer 46 are sequentially formed thereon.
The refractive index of the low refractive index layer 45 is 1.38, FIG. 13A shows the case where the metal layer 46 is Al, and FIG. 13B shows the case where the metal layer 46 is Ag. The film thickness (nm) of the rate layer 45 is shown.

  13 (a) and 13 (b), it can be seen that as the film thickness of the low refractive index layer 45 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 45 in contact with the metal layer 46 is large, and the wave number of the SPP becomes small due to the influence of the refractive index of the low refractive index layer 45. In addition, the narrowing of the peak width indicates that the light captured as the SPP is extracted into the organic layer and the attenuation when the light is guided in the plane is small. This will be described next.

The peak change will be described below with reference to FIGS. 14 (a), 14 (b), and 14 (c).
In FIG. 14A, the light is completely trapped on the surface of the metal layer 46 as the SPP mode light. This represents the time when the film thickness of the low refractive index layer 45 is 0 nm, the laminated structure on the organic layer 43 to metal layer 46 side does not form an Otto type arrangement, and the SPP mode light is transmitted between the metal layer 46 and the cathode 44. The peak width is large because it rapidly attenuates while propagating in the in-plane direction.
Next, as the film thickness of the low refractive index layer 45 is increased, as shown in FIG. 14B, 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 guided mode light and is recaptured as SPP mode light again by the metal layer 46 by interface reflection. In this case, since the light is less likely to attenuate than the SPP mode light of FIG. 14A, the peak width becomes gradually narrower.
Finally, when the film thickness of the low refractive index layer 45 is sufficiently thick, it becomes as shown in FIG. In this case, although the Otto type arrangement is used, the evanescent wave at the light emission point does not reach the metal layer 46 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 45 exceeds a certain thickness, the trapped light is only guided mode light, so that the ease of attenuation does not change and the peak width also does not change.

FIG. 15 is a diagram showing a change in peak width (half width) with respect to the film thickness of the low refractive index layer 45. When the metal layer 46 is Al, the film thickness of the low refractive index layer 45 is 200 nm or more. It can be seen that the change in the peak width becomes smaller and the emitted light is not easily captured by the SPP. It can also be seen that when the metal layer 46 is Ag, the change in peak width is small when the film thickness of the low refractive index layer 45 is 150 nm or more, and it is difficult to be captured as SPP mode light.
That is, it can be seen that the film thickness of the low refractive index layer 45 captured as SPP mode light is at least 300 nm or less, and the capturing effect becomes remarkable at 200 nm or less. In this study, the case where the refractive index of the low refractive index layer 45 is n = 1.38 is calculated, but the refractive index is not limited to 1.38, and the metal layer 46 is also made of Ag and Al. It is not limited.

Further, in the Otto type arrangement, the surface plasmon polariton (SPP) trapped on the surface of the metal layer 46 can be taken out by an evanescent wave generated by light totally reflected at the interface between the cathode 44 and the low refractive index layer 45. That is, the wave number of the evanescent wave, it is necessary to have a wave number k _'sp and the intersection of the SPP that is generated on the surface of the metal layer 46.

The real part of the relative permittivity of the metal layer 46 is ε ₁ , the relative permittivity of the low refractive index layer 45 is ε ₂ , and the wave number of light in the vacuum at the peak wavelength of light emitted from the light emitting layer (angular frequency / in vacuum) (Speed of light) is k ₀ , the real part of the wave number k ′ _sp of the SPP generated on the surface of the metal layer 46 is the same expression as k _{sp in the} above equation (1).

On the other hand, the vertical component of the wave number in the low refractive index layer 45 of the surface plasmon polariton (SPP) generated on the surface of the reflective layer 46 can be expressed by the following formula (4).

となる。
つまり、式（５）が十分大きければ、金属層４６の表面に生成されるＳＰＰの電磁場が陰極や有機層に滲み出し、陰極４４と低屈折率層４５の界面での全反射により生じたエバネッセント波とカップリングして、取り出すことができる。
図１６（ａ）は金属層４６をＡｌ、（ｂ）は金属層４６をＡｇとした場合の式（５）をグラフ化した図である。 When the magnitude (intensity) of the electromagnetic field of the SPP generated on the surface of the metal layer 46 is normalized with the value on the surface of the metal layer 46 being 1, the bleeding occurs while exponentially decaying in the direction perpendicular to the metal layer 46. The strength of the SPP that reaches the interface between the low refractive index layer 45 and the cathode 44 is approximately when the thickness of the low refractive index layer 45 is h ₂ and reflection at each interface can be ignored.

It becomes.
In other words, if the formula (5) is sufficiently large, the electromagnetic field of the SPP generated on the surface of the metal layer 46 oozes out to the cathode and the organic layer, and evanescent generated by total reflection at the interface between the cathode 44 and the low refractive index layer 45. Coupling with the wave can be taken out.
FIG. 16A is a graph showing the equation (5) when the metal layer 46 is Al, and FIG. 16B is a graph when the metal layer 46 is Ag.

  Comparing this result with FIGS. 13A and 13B, in the formula (5), the strength of the SPP generated on the surface of the metal layer 46 at the interface of the low refractive index layer 45 / cathode 44 is When the intensity on the surface of the metal layer 46 is normalized as 1, the peak width is the thickness of the low refractive index layer 45 at which the SPP intensity is 0.4 or less at the position propagated in the thickness direction of the low refractive index layer 45. Is saturated to a constant value. That is, when the formula (5) is 0.4 or less, it can be said that the intensity of the SPP that oozes out to the interface between the low refractive index layer 45 and the cathode 44 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 45 is 0.4 or more in the formula (5). In this study, the case where the refractive index of the low refractive index layer 45 is n = 1.38 is calculated, but the refractive index is not limited to 1.38, and the metal layer 46 is also made of Ag and Al. It is not limited. If the condition that the intensity of SPP at the interface between the low refractive index layer 45 and the cathode 44 expressed by the formula (5) is larger than a certain value (for example, 0.4) is satisfied, the SPP mode light is converted into the organic layer by the Otto type arrangement. As long as this condition is satisfied, the refractive index of the low refractive index layer 45 and the material of the metal layer 46 are not limited.

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

Example 1
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 tracking the time change of the electromagnetic field at each point in space by differentiating Maxwell's equation describing the time change of the electromagnetic field spatially and temporally. In order to calculate the light extraction efficiency of the organic EL element by the FDTD method, the light emission in the light emitting layer is regarded as the radiation from the minute dipole, and the intensity of the radiation is counted. More specifically, the frequency dependence is calculated using the ratio of the light extracted to the substrate with respect to the total radiation intensity of the dipole as the light extraction efficiency. Hereinafter, the calculation result of the light extraction efficiency is shown in a graph. Λ on the horizontal axis represents the frequency of the dipole as a wavelength in vacuum, and η on the vertical axis represents the light extraction efficiency. 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 moment is random in all directions).

FIG. 17 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. The high refractive index layer 7 is made of zirconia and has a refractive index of 1.90. The anode (first electrode) 2 and the cathode (second electrode) 4 are made of ITO, the refractive index is set to 1.82 + 0.009i at 550 nm, and the other wavelengths are extrapolated by the Lorentz model. The average refractive index of the organic layer 3 was 1.72. The low refractive index layer 5 is made of SOG and has a refractive index of 1.25. 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 layer thicknesses of the anode 2, the organic layer 3, the cathode 4, the low refractive index layer 5, and the metal layer 6 were 150 nm, 210 nm, 50 nm, 100 nm, and 100 nm, respectively. In the high refractive index layer 7, the tip 7a2 has a height of 500 nm, the columnar part 7a1 has a height of 750 nm, and the layered part 7b has a thickness of 150 nm.
Furthermore, the width of the convex portion 7a of the high refractive index layer 7 was 1000 nm, and the period (pitch) p between the adjacent convex portions 7a was 1600 nm. Here, the convex portion 7a has a translational symmetrical structure in the depth direction of the drawing. That is, in a plan view, the convex portion and the hole have a line shape extending infinitely in one direction in the plane. Moreover, the front-end | tip part 7a2 has a semicircular shape in the cross-sectional shape which crosses a translation structure. However, in any calculation model, the light source is not translationally symmetric in the depth direction of the paper, but is placed in the form of dots in the film thickness of the organic layer layer portion. Computer simulation calculation was performed assuming that light emission (star mark in FIG. 17) was emitted at a position of 132.5 nm from the cathode 4 on the central axis of the adjacent convex portion.

(Example 2)
As shown in FIG. 18 (a), the tip 7a2 was subjected to the same computer simulation calculation with a cross section crossing the translational structure being triangular. All other configurations were the same as in Example 1.

(Example 3)
As shown in FIG. 18 (b), the tip portion 7a2 was subjected to the same computer simulation calculation with a cross section crossing the translational structure as a shape in which two triangles form a dual. All other configurations were the same as in Example 1.

(Comparative Example 1)
As shown in FIG. 18C, the same computer simulation calculation was performed with the columnar portion 27a1 having no top portion and a flat top portion. All other configurations were the same as in Example 1. The height of the columnar portion 27a1 was set to 1250 nm, which is the same as the height of the convex portion of the example, and consistency with the example was taken.

(Comparative Examples 2 and 3)
Further, as Comparative Example 2, the structure has a cathode-side structure with an Otto type arrangement, but does not have a first electrode-side structure that takes out propagating light extracted into the organic layer without taking it as guided mode light (hereinafter referred to as a “guide electrode mode structure”). The first electrode side which does not have the second electrode side structure of the Otto type arrangement as Comparative Example 3 and takes out the propagating light to the outside without using the guided mode light. Calculations were also made for a structure having no 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 are 1.52, 1.82 + 0.009i, 1.72, 0.649 + 4.32i, respectively, and the anode, organic layer, and cathode layer thicknesses are 150 nm, 210 nm, 100 nm.

  FIG. 19 is a diagram showing the results of calculating the light extraction efficiency η of the organic EL elements of Examples 1 to 3 and Comparative Examples 1 to 3 by computer simulation using the FDTD method. As shown in FIG. 19, it can be seen that Examples 1 to 3 have improved light extraction efficiency at almost all wavelengths of 450 nm to 750 nm compared to Comparative Examples 1 to 3. In particular, when Examples 1 to 3 are compared with Comparative Example 1, since Examples 1 to 3 have an inclined surface having an inclination angle with respect to the substrate surface at the tip of the convex part, the light reincident on the adjacent convex part. It can be seen that the light extraction efficiency is improved compared to Comparative Example 1.

1, 11, 21, 31, 41 Substrate 2, 12, 22, 32, 42 First electrode (anode)
3, 13, 23, 33, 43 Organic layer 4, 14, 24, 34, 44 Second electrode (cathode)
5, 15, 25, 45 Low refractive index layer 6, 16, 26, 46 Metal layer 7, 17, 27 High refractive index layer 7a Convex part 17a Concave part 7a1, 27a1 Columnar part 7a2 Tip part 17a1 Columnar hole part 17a2 Base 10 , 20, 30, 40, 50 Organic EL element R Resist M Mold S Spin-on dielectric U Curing resin 100 Image display device 104 Anode wiring 106 Anode auxiliary wiring 108 Cathode wiring 110 Insulating film 112 Cathode partition 116 Sealing plate 118 Sealing material 120 opening 200 lighting device 201 lighting circuit 202 terminal 203 terminal

Claims (16)

An organic EL device comprising 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 and a metal layer are sequentially provided from the side in contact with the opposite surface,
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,
A high refractive index layer is provided on the surface of the first electrode opposite to the organic layer,
The high refractive index layer is made of a material having a refractive index higher than that of the substance adjacent to the surface opposite to the first electrode and having a higher refractive index than that of the low refractive index layer. The high refractive index layer has a plurality of convex portions,
The convex part is composed of a columnar part and a tip part formed in order from the first electrode side,
The columnar part stands upright with respect to the first electrode,
The tip part has an apex on the side opposite to the first electrode, and has an inclined surface that inclines toward the apex.   The organic EL element according to claim 1, wherein the columnar portion has a height of 0.3 to 500 μm.   The organic EL element according to claim 1, wherein the columnar portion has a width of 0.3 to 500 μm.   The organic EL element according to any one of claims 1 to 3, wherein a height of the tip is 0.05 to 5 times a width of a bottom surface thereof. An organic EL device comprising 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 and a metal layer are sequentially provided from the side in contact with the opposite surface,
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,
A high refractive index layer is provided on the surface of the first electrode opposite to the organic layer,
The high refractive index layer is made of a material having a refractive index higher than that of the substance adjacent to the surface opposite to the first electrode and having a higher refractive index than that of the low refractive index layer. The high refractive index layer has a plurality of recesses,
The concave portion includes a columnar hole portion and a root portion formed in order from the first electrode side,
The columnar hole is perforated perpendicular to the first electrode,
The organic EL element, wherein the base has an inclined surface that extends toward the opposite side of the first electrode.   The organic EL element according to claim 5, wherein the depth of the columnar hole is 0.3 to 500 μm.   7. The organic EL element according to claim 5, wherein a width of the columnar hole is 0.3 to 500 μm.   8. The depth of the root portion is 0.025 to 2.5 times the difference between the width of the root portion and the width of the columnar hole portion. The organic EL element of description.   The thickness of the said low-refractive-index layer is 20 nm or more and 300 nm or less, The organic EL element as described in any one of Claims 1-8 characterized by the above-mentioned.   The organic EL element according to claim 1, wherein the convex portion or the concave portion is formed in a line shape that is continuous in one direction in a plane.   The organic EL element according to claim 1, wherein the high refractive index layer is composed of a plurality of layers.  The organic EL element according to claim 1, wherein a refractive index of the low refractive index layer is further lower than a refractive index of the second electrode.   The organic EL element according to claim 12, wherein the refractive index of the second electrode is further lower than the 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 second electrode and the organic layer. Organic EL element.   An image display device comprising the organic EL element according to claim 1.   An illuminating device comprising the organic EL element according to claim 1.

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