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WO2015016176A1 - Élément électroluminescent organique, dispositif d'affichage d'image, et dispositif d'éclairage - Google Patents

Élément électroluminescent organique, dispositif d'affichage d'image, et dispositif d'éclairage Download PDF

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Publication number
WO2015016176A1
WO2015016176A1 PCT/JP2014/069820 JP2014069820W WO2015016176A1 WO 2015016176 A1 WO2015016176 A1 WO 2015016176A1 JP 2014069820 W JP2014069820 W JP 2014069820W WO 2015016176 A1 WO2015016176 A1 WO 2015016176A1
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refractive index
layer
organic
light
substrate
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Japanese (ja)
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祥貴 下平
祐介 山▲崎▼
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Resonac Holdings Corp
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Showa Denko KK
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/875—Arrangements for extracting light from the devices
    • H10K59/879—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses

Definitions

  • the present invention relates to an organic EL element, an image display device, and a lighting device.
  • This application claims priority on July 31, 2013 based on Japanese Patent Application No. 2013-159700 for which it applied to Japan, and uses the content here.
  • An organic EL (electroluminescence) element has features such as a wide viewing angle, high-speed response, and clear self-luminous display.
  • Organic EL elements having such features are expected as pillars for next-generation lighting devices, image display devices, and the like because they are thin and light and have low power consumption.
  • the organic EL element has a bottom emission type in which light is extracted from the support substrate side and light is extracted from the opposite side of the support substrate according to the direction in which light generated in the organic light emitting layer is extracted to the outside of the element. It can be divided into an emission type.
  • 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.
  • the light emitted from the light emitting layer is critical at the interface between a transparent substrate (for example, glass (typical refractive index: 1.52)) and air (refractive index: 1.0).
  • a transparent substrate for example, glass (typical refractive index: 1.52)
  • air refractive index: 1.0
  • Light incident at a small incident angle (angle formed by the incident ray and the normal of the incident interface) that is smaller than the angle is refracted at the interface and extracted outside the device.
  • these lights are referred to as external mode light.
  • 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 thus is not extracted outside the device. Can be absorbed by the material.
  • this light is referred to as substrate mode light, and the loss due to this is referred to as substrate loss.
  • substrate mode light the light incident on various interfaces between the substrate and the cathode at an incident angle larger than the critical angle
  • the loss due to this will be referred to as waveguide loss.
  • Various interfaces include an anode made of a transparent conductive oxide (for example, indium tin oxide (ITO (typical refractive index: 1.82)) and a transparent substrate (for example, glass (typical refractive index: 1.52). And the interface between the high refractive index layer and the low refractive index layer disposed between the anode and the cathode. Further, among the light emitted from the light emitting layer, the light incident on the metal cathode and combined with the free electrons of the metal cathode, and the light captured on the surface of the metal electrode as surface plasmon polariton (SPP) is also external to the element. And can be finally absorbed into the material.
  • SPP mode light this light is referred to as SPP mode light, and the loss due to this is referred to as plasmon loss.
  • the light extraction efficiency of the organic EL element (the ratio of the light extracted outside the element with respect to the light emitted from the light emitting layer) generally remains at 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 an important issue to reduce the loss and improve the light extraction efficiency.
  • 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).
  • Patent Document 2 On the other hand, it can be said that research has just started on a method for reducing guided mode light and SPP mode light to improve extraction efficiency, particularly a method for reducing SPP mode light and improving extraction efficiency.
  • Patent Document 3 discloses a configuration in which a high refractive index layer having a higher refractive index than that of an organic light emitting layer or a transparent electrode is inserted in the vicinity of the organic light emitting layer.
  • Patent Document 2 discloses a configuration in which the refractive index of the organic light emitting layer and the transparent electrode is equivalently lowered by dispersing fine particles having a refractive index lower than that of the organic light emitting layer and the transparent electrode in the organic light emitting layer and the transparent electrode. ing.
  • Patent Documents 4 and 5 disclose a configuration in which a cavity is formed 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. Most of the light refracted to the substrate side is incident on the interface between the transparent electrode and the substrate and the interface between the substrate and air at an angle smaller than the critical angle, so that the ratio of light that causes total reflection at these interfaces can be reduced. it can.
  • Patent Document 6 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).
  • the light extraction efficiency cannot be improved unless the light becomes guided mode light and can be extracted outside the device.
  • the present invention has been made in view of the above circumstances, and provides an organic EL element, an image display device, and an illumination device that effectively extract SPP mode light and waveguide mode light and have improved light extraction efficiency. Objective.
  • the present inventors first assume a number of light extraction mechanisms in two steps that take out SPP mode light as propagating light and then take out the propagating light out of the device without using it as guided mode light.
  • the structures we have intensively studied effective structures that improve the light extraction efficiency. 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.
  • the above-described two-step light extraction mechanism generates the SPP mode light and the second electrode side structure of the Otto type arrangement (Non-Patent Document 1) that extracts the generated SPP mode light as propagation light, and its propagation. It consists of a first electrode side structure that takes out light without using it as guided mode light.
  • the present inventors refracted or directed the second electrode side structure of the Otto type arrangement and the guided mode light toward the substrate side (opposite side of the substrate in the top emission type).
  • the present inventors refracted or directed the second electrode side structure of the Otto type arrangement and the guided mode light toward the substrate side (opposite side of the substrate in the top emission type).
  • 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 thickness of 20 nm on the surface of the second electrode opposite to the organic layer.
  • a low refractive index layer of 300 nm or less and a metal layer are provided in this order from the side in contact with the opposite surface, the second electrode is made of a light-transmitting conductive material, and the refractive index of the low refractive index layer is The first refractive index material layer is lower than the refractive index of the organic layer, on the surface of the first electrode opposite to the organic layer, and in the in-plane direction of the first refractive index material layer.
  • An organic EL element comprising a refractive index modulation structure having a plurality of second refractive index material regions arranged discretely.
  • An organic EL element comprising a first electrode, an organic layer including a light emitting layer, and a second electrode in this order on a substrate, on the surface of the second electrode opposite to the organic layer, A low refractive index layer having a thickness of 20 nm or more and 300 nm or less and a metal layer are provided in this order from the side in contact with the opposite surface, and the second electrode is made of a translucent conductive material, and the low refractive index layer
  • the refractive index is lower than the refractive index of the organic layer, and includes a refractive index modulation structure in which a plurality of substrate recesses discretely formed on the surface layer of the substrate are filled with a material different from the refractive index of the substrate.
  • An organic EL device characterized by that.
  • (3) An organic EL device comprising a first electrode, an organic layer including a light emitting layer, and a second electrode on a substrate in order, on the surface of the second electrode opposite to the organic layer
  • a low refractive index layer having a thickness of 20 nm to 300 nm and a metal layer in order from the side in contact with the opposite surface, wherein the second electrode is made of a light-transmitting conductive material, and the low refractive index layer
  • the refractive index of the substrate is lower than the refractive index of the organic layer, has a plurality of substrate protrusions discretely formed on the surface layer of the substrate, and is different from the refractive index of the substrate so as to cover the side surface
  • An organic EL element comprising a refractive index modulation structure formed of (4) The organic EL element according to any one of (1) to (3), wherein a refractive index of the low refractive index layer is lower than a refractive index of
  • 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.
  • the real part ⁇ 1 of the dielectric constant of the metal layer, the dielectric constant ⁇ 2 of the low refractive index layer, and the second refractive index material region, the substrate concave portion or the substrate convex portion are within the element plane.
  • ⁇ is the peak wavelength of the photoluminescence spectrum of the light emitting layer.
  • the organic EL element according to (8), wherein the period is 200 nm to 2000 nm.
  • An image display device comprising the organic EL element according to any one of (1) to (9).
  • An illumination device comprising the organic EL element according to any one of (1) to (9).
  • an organic EL element an image display device, and an illumination device that effectively extract SPP mode light and waveguide mode light and improve light extraction efficiency.
  • FIG. 1 It is a perspective view of the organic EL element shown in FIG. In order to make the features of the invention easy to understand, the Otto type arrangement structure is shown separately.
  • FIG. 1 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.
  • FIG. 1 It is a cross-sectional schematic diagram of an organic EL element for demonstrating the change of the peak in FIG.
  • A is a case where the film thickness of the low refractive index layer is 0 nm
  • (b) is a case where SPP mode light and waveguide mode light are mixed as the film thickness of the low refractive index layer is increased
  • (c) Is a case where the film thickness of the low refractive index layer is sufficiently thick and 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 with respect to the film thickness of a low refractive index layer in the result of energy dissipation calculation in FIG.
  • (a) is a figure which represented the formula (16) at the time of making a metal layer into Al and (b) making a metal layer into Ag. It is a figure which shows the result of the computer simulation calculation which investigated the period dependence about the light extraction efficiency of the organic EL element of 1st Embodiment of this invention using the random dipole. It is a cross-sectional schematic diagram for demonstrating the structure of the organic EL element which performed the simulation of FIG.
  • the dependence of the intensity distribution of the electric field of the radiated light from the horizontal dipole on the pitch between the adjacent second refractive index material regions is calculated by computer simulation. It is the result of investigating by calculation, and the pitch (a) is 200 nm, (b) is 300 nm, (c) is 500 nm, (d) is 900 nm, (e) is 2000 nm, and (f) is 4000 nm.
  • the computer simulation shows the dependence of the intensity distribution of the magnetic field of the emitted light from the dipole in the vertical direction on the pitch between the adjacent second refractive index material regions. It is the result of investigating by calculation, and the pitch (a) is 200 nm, (b) is 300 nm, (c) is 500 nm, (d) is 900 nm, (e) is 2000 nm, and (f) is 4000 nm.
  • one of the first electrode and the second electrode is an anode and the other is a cathode.
  • a configuration in which the first electrode is an anode and the second electrode is a cathode will be described as an example.
  • the organic EL device of the present invention may include a layer not described below within a range not impairing the effects of the present invention.
  • 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. 2 is a perspective view of the organic EL element according to the first embodiment shown in FIG.
  • An organic EL element 10 shown in FIG. 1 includes an anode (first electrode) 2, an organic layer 3 including a light emitting layer, and a cathode (second electrode) 4 in this order.
  • a low refractive index layer 5 having a thickness of 20 nm to 300 nm and a metal layer 6 are sequentially provided from the side in contact with the opposite surface.
  • the cathode 4 is made of a translucent conductive material, and the refractive index of the low refractive index layer 5 is lower than the refractive index of the organic layer 3.
  • a first refractive index material layer 8 a is provided, and a plurality of second refractive index material regions are discretely arranged in the in-plane direction of the first refractive index material layer 8 a.
  • a refractive index modulation structure 8 having 8b is provided. The configuration indicated by the solid line in FIG.
  • 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 laminated structure of the cathode side metal layer / low refractive index layer / cathode / organic layer is common.
  • this laminated structure of metal layer / low refractive index layer / cathode / organic layer when the refractive indexes of the low refractive index layer, the cathode, and the organic layer are n L , n C , and n O , respectively, the refractive index of the low refractive index layer Are lower than the refractive index of the organic layer, n L ⁇ n O ⁇ n C (hereinafter referred to as “B pattern”), n L ⁇ n C ⁇ n O (hereinafter referred to as “C pattern”).
  • n C ⁇ n L ⁇ n O (hereinafter referred to as “D pattern”).
  • the Otto type arrangement it is necessary to arrange the layers in the order of metal / low refractive index medium / high refractive index medium.
  • the structure of the metal layer / low refractive index layer / cathode is an Otto type arrangement.
  • the configuration of the metal layer / low refractive index layer / cathode is the Otto type arrangement
  • the configuration of the metal layer / low refractive index layer + cathode / organic layer is also the Ototo type arrangement.
  • the configuration of metal layer / low refractive index layer + cathode / organic layer is an Otto type arrangement.
  • the most preferable B to D pattern is the C pattern.
  • the configuration of the metal layer / low refractive index layer / cathode (transparent conductive layer) is an Otto type arrangement, and the configuration of metal layer / low refractive index layer + cathode (transparent conductive layer) / organic layer is also used. It is an Otto type arrangement. Therefore, re-radiation of SPP mode light is most likely to occur from the metal layer. Furthermore, since the refractive index increases in the order of the low refractive index layer, the cathode (transparent conductive layer), and the organic layer, total reflection does not occur at each interface, and the re-radiated SPP mode light is extracted as it is to the substrate side.
  • the cathode is PEDOT: PSS (poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid), typical refractive index: 1.5), etc.
  • the transparent conductive material layer may be a case where the low refractive index layer is SOG (spin on glass) that satisfies the refractive index condition of air or C pattern. Next preferred is the B pattern.
  • the configuration of the metal layer / low refractive index layer / cathode (transparent conductive layer) is an Otto type arrangement. Therefore, re-radiation of SPP mode light occurs from the metal layer.
  • the refractive index of the organic layer is an intermediate value between the low refractive index layer and the cathode (transparent conductive layer)
  • a part of the re-radiated SPP mode light is reflected by the cathode (transparent conductive layer) / organic layer.
  • the light is totally reflected at the interface, and the remaining light is transmitted to the organic layer.
  • a-ITO amorphous ITO, typical refractive index: 2.1
  • a material having a lower refractive index than the material of the organic layer is selected from SOG as the material of the low refractive index layer.
  • SOG material of the low refractive index layer
  • the configuration of the metal layer / low refractive index layer / cathode (transparent conductive layer) is not an Otto type arrangement, but the configuration of metal layer / low refractive index layer + cathode (transparent conductive layer) / organic layer. Only Otto type arrangement. Therefore, although re-radiation of SPP mode light occurs from the metal layer, re-radiation of SPP mode light is further reduced as compared with the case of the B pattern.
  • PEDOT: PSS is selected as the cathode material for the organic layer (typical refractive index: 1.7 to 1.8), and the refractive index n is selected as the material for the low refractive index layer.
  • a material in which L is between n C and n 2 O , for example, SOG that satisfies the refractive index of the B pattern may be used.
  • n O ⁇ n C ⁇ n L (hereinafter referred to as “E pattern”) and in the case of n C ⁇ n O ⁇ n L (hereinafter also referred to as “F pattern”), the Otto type arrangement is not achieved.
  • n O ⁇ n L ⁇ n C (hereinafter referred to as “A pattern”), the metal layer / low refractive index layer / cathode are in an Otto type arrangement, and re-emission of SPP mode light occurs from the metal layer.
  • the refractive index of the organic layer is lower than that of the low refractive index layer, most of the SPP mode light re-radiated at the cathode (transparent conductive layer) / organic layer interface is totally reflected. Therefore, most of the re-radiated SPP mode light is totally reflected at the cathode (transparent conductive layer) / organic layer interface, and it is difficult to extract the light extracted as the propagation light on the anode side.
  • An organic EL element 10 shown in FIG. 1 is a bottom emission type organic EL element that extracts light emitted from a light emitting layer from a substrate side. Therefore, the substrate 1 is a light-transmitting substrate and usually needs to be transparent to visible light.
  • transparent to visible light means that it is only necessary to transmit visible light having a wavelength emitted from the light emitting layer, and it is not necessary to be transparent over the entire visible light region.
  • a smooth substrate having a transmittance in visible light of 400 to 700 nm of 50% or more is preferable.
  • Specific examples of the substrate 1 include a glass plate and a polymer plate.
  • the material of the glass plate examples include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz.
  • the polymer plate examples include polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyether sulfide, and polysulfone.
  • an opaque one can also be used.
  • a substrate made of a non-metallic material such as GaN, GaAs, or sapphire, or a substrate normally used in other top emission type organic EL elements can be used.
  • a material having high thermal conductivity for the substrate it is preferable to use a material having high thermal conductivity for the substrate.
  • the thickness of the substrate 1 is not limited by the required mechanical strength.
  • the thickness is preferably 0.01 mm to 10 mm, more preferably 0.05 mm to 2 mm.
  • the refractive index modulation structure 8 has a structure in which one region (second refractive index material region) is discretely arranged in the other (first refractive index material layer) and the refractive index is modulated.
  • the discrete arrangement may be a periodic arrangement or an aperiodic arrangement.
  • the plurality of second refractive index material regions arranged discretely may all have the same shape or may include different shapes.
  • the refractive index modulation structure 8 is a case where one region (second refractive index material region) is discretely arranged and the other (first refractive index material layer) is also discretely arranged like a checker pattern. There may be.
  • the refractive index modulation structure 8 shown in FIG. 1 may be any material having a different refractive index.
  • the first refractive index material layer 8a is made of a high refractive index material
  • the second refractive index material region 8b is a low refractive index material.
  • a high refractive index and a low refractive index in a high refractive index material and a low refractive index material mean high and low refractive indices with respect to each other.
  • the first refractive index material layer 8a made of a high refractive index material is formed in a sea shape in the in-plane direction.
  • the second refractive index material region 8b made of a low refractive index material has island-like portions arranged discretely in an island shape.
  • the refractive index modulation structure 8 shown in FIG. 1 has a low refractive index material region in which holes formed discretely in the in-plane direction of the layer 8a made of a high refractive index material are filled with a low refractive index material. 8b is formed.
  • the first refractive index material layer 8a is made of a low refractive index material
  • the second refractive index material region 8b is made of a high refractive index material.
  • the period (pitch) p is an integer.
  • N (1 ⁇ N ⁇ 3) is preferably selected so as to satisfy the above-described formula (1).
  • the period p varies depending on the material of the metal layer 6 and the low refractive index layer 5, it is preferable to consider the selection of the material.
  • the period p of the second refractive index material region 8b is shown.
  • the direction in the element plane means the in-plane direction in which each layer of the organic EL element is laminated, for example, the in-plane direction of the surface of the first electrode or the substrate surface.
  • the second refractive index material regions that are discretely arranged are periodically arranged with a period p that is approximately equal to or less than the wavelength of the light, whereby the first refractive index material layer and the second refractive index material region are photo-removed. It is good also as a structure which makes a nick crystal.
  • the high refractive index material and the low refractive index material constituting the refractive index modulation structure 8 are materials having different refractive indexes and are not particularly limited as long as they have translucency.
  • silicon oxide such as spin-on-glass (SOG, refractive index: 1.1 to 2.0) and silica (SiO 2 ), magnesium oxide (MgO, typical refractive index: 1.74) Oxides, metal halides including magnesium fluoride (MgF 2 , typical refractive index: 1.38), nitrides including aluminum nitride (AlN), aluminum oxynitride (AlON) and silicon Oxynitrides including oxynitrides, fluororesins including polytetrafluoroethylene (PTFE, typical refractive index: 1.35), polymethyl methacrylate (typical refractive index: 1.49) Or a polymer compound resin such as polyethylene naphthalate (typical refractive index: 1.77).
  • the thickness of the refractive index modulation structure 8 is not particularly limited. For example, it is 10 to 2000 nm, preferably 50 to 1000 nm. If the thickness of the refractive index modulation structure 8 is thinner than 10 nm, the volume of the refractive index modulation structure 8 becomes small, and the waveguide mode light is hardly diffracted. If the refractive index modulation structure 8 is thicker than 2000 nm, it is difficult to maintain the flatness of the anode 2.
  • the anode 2 is an electrode for applying a voltage between the anode 4 and injecting holes from the anode 2 into the light emitting layer. Therefore, it is preferable to use a material made of a metal, an alloy, a conductive compound, or a mixture thereof having a large work function for the anode 2, and there is a difference from the HOMO (Highest Occupied Molecular Orbital) level of the organic layer in contact with the anode. It is preferable to use a work function of 4 eV or more and 6 eV or less so as not to be excessive.
  • the material of the anode 2 is not particularly limited as long as it is a translucent and conductive material.
  • the anode 2 can be formed on the substrate 1 by, for example, a sputtering method, a vacuum deposition method, a coating method, or the like.
  • the thickness of the anode 2 is not limited, but is, for example, 10 to 2000 nm, and preferably 50 to 1000 nm. When the thickness of the anode 2 is thinner than 10 nm, the sheet resistance of the anode 2 increases. If the thickness of the anode 2 is greater than 2000 nm, the flatness of the organic layer 3 cannot be maintained, and the transmittance of the anode 2 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 (organic light emitting layer) made of an organic EL material.
  • the hole injection layer is a layer that assists hole injection into the light emitting layer
  • the hole transport layer is a layer that transports to the light emitting region. These have a high hole mobility and a small ionization energy of usually 5.5 eV or less.
  • a material that transports holes to the light emitting layer with lower electric field strength is preferable.
  • the material to be formed is not particularly limited as long as it can perform the above functions, and any material can be selected and used from known materials.
  • the organic layer 3 may be formed by a dry process such as an evaporation method or a transfer method, or may be formed by a wet process such as a spin coating method, a spray coating method, a die coating method, or a gravure printing method.
  • the thickness of the organic layer 3 is not limited, but is, for example, 50 to 2000 nm, and preferably 100 to 1000 nm. If the thickness of the organic layer 3 is less than 50 nm, quenching other than SPP coupling by metal, such as reduction of internal QE due to penetration current and lossy surface coupling, occurs. When the thickness of the organic layer 3 is greater than 1000 nm, the driving voltage increases.
  • the cathode 4 is an electrode for injecting electrons into the light emitting layer. Therefore, 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, so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level of the organic layer in contact with the anode does not become excessive. It is preferable to use a material having a work function of 1.9 eV or more and 5 eV or less. As a material of the cathode 4, it is necessary to use a light-transmitting conductive material in order to form a cathode side structure with an Otto type arrangement. Therefore, the same anode material as described above can be used.
  • the thickness of the cathode 4 is not limited, but is, for example, 30 nm to 1 ⁇ m, and preferably 50 to 500 nm. If the thickness of the cathode 4 is less than 30 nm, the sheet resistance increases and the driving voltage increases. If the thickness of the cathode 4 is greater than 1 ⁇ m, 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 opposite side of the cathode 4 from the organic layer 3 and is made of a material lower than the refractive index of the organic layer 3.
  • the low refractive index layer 5 is preferably made of a material having a lower refractive index than the translucent conductive material constituting the cathode 4.
  • the material for the low refractive index layer 5 is not particularly limited as long as it is a material having a lower refractive index than the translucent conductive material constituting the cathode 4.
  • metal fluorides such as SOG, MgF 2 (typical refractive index: 1.38), organic fluorine compounds such as PTFE, SiO 2 (typical refractive index: 1.45), various low melting glass, Examples include porous materials.
  • the low refractive index layer 5 is a layer including an air layer, and may have a lower refractive index than 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.
  • the cathode and the organic layer correspond to an Otto type high refractive index layer. If the difference in refractive index between the low refractive index layer and the high refractive index layer is 0.2 or more in the Otto type arrangement, the in-plane component of the wave number of the SPP mode light becomes small. Therefore, the propagation light in the high refractive index layer and the SPP mode The light dispersion curves are crossed, and the efficiency of taking out the SPP mode light into the high refractive index layer by the Otto type arrangement can be increased.
  • the thickness of the low refractive index layer 5 is preferably 20 nm to 300 nm. If the thickness of the low refractive index layer 5 is less than 20 nm, the metal layer and the high refractive index layer come close to each other and the in-plane wavenumber component of the SPP mode light becomes large, so that the dispersion curve shows the propagation light in the high refractive index layer. The dispersion curve does not intersect and the SPP mode light is not easily extracted into the high refractive index layer. When the thickness of the low refractive index layer 5 is greater than 300 nm, the evanescent wave does not reach the metal layer 6 and the SPP mode light is hardly extracted into the high refractive index layer. Therefore, 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.
  • the material of the metal film 6 may be any material that causes plasmon resonance due to the light emitted from the light emitting layer. Therefore, almost any single metal or alloy can be used. In particular, a material in which the real part of the complex dielectric constant is negative and the absolute value of the real part has a large value is preferable. Examples of such materials include simple substances such as gold, silver, copper, zinc, aluminum, and magnesium, alloys of gold and silver, alloys of silver and copper, and alloys such as brass.
  • the metal layer 6 may have a laminated structure of two or more layers.
  • the thickness of the metal layer 6 is not limited, but is, for example, 20 to 2000 nm, and preferably 50 to 500 nm. When the thickness of the metal layer 6 is less than 20 nm, the reflectance is lowered and the front luminance is lowered. If the thickness of the metal layer 6 is greater than 500 nm, heat and radiation damage during film formation, and mechanical damage due to film stress accumulate in the electrode and the organic layer.
  • 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.
  • SPP surface plasmon polariton
  • the dispersion relation (angular frequency w, wave vector k) of normal propagation light is given by the following equation (3).
  • the dispersion curve of surface plasmon polariton (SPP) does not intersect the normal dispersion light dispersion line. Therefore, normal propagating light cannot excite SPP on a flat metal surface, and propagating light cannot be extracted directly from SPP present on the flat metal surface.
  • ⁇ is an incident angle of incident light from the high refractive index layer to the low refractive index layer. Accordingly, by changing the incident angle ⁇ , the SPP dispersion curve intersects with the dispersion line of the total reflection evanescent wave (hereinafter, simply referred to as “evanescent wave” is also all generated by total reflection).
  • evanescent wave is also all generated by total reflection.
  • the “incident angle ⁇ ” is the radiation angle of the SPP when viewed from the metal side. That is, when the Otto type arrangement is used, the dispersion curve of the SPP and the dispersion line of the evanescent wave intersect each other. This means that only the SPP radiated at a predetermined angle is in a state where energy can be exchanged by the resonance of the SPP and the evanescent wave. And it becomes possible to take out SPP as propagation light radiated
  • a predetermined incident angle (SPP) of light emitted from the light emitting layer in the organic layer is provided adjacent to the organic layer.
  • the light incident on the high refractive index layer / low refractive index interface from the high refractive index layer generates an evanescent wave at an angle where the dispersion curve and the dispersion line of the evanescent wave intersect.
  • the generated evanescent wave excites SPP mode light on the surface of the metal layer.
  • SPP mode light excited on the surface of the metal layer can be extracted as propagating light emitted at a predetermined angle via an evanescent wave generated in the Otto type arrangement structure. That is, by introducing the Otto type arrangement structure in the organic EL element, it becomes possible to extract SPP mode light as propagating light emitted at a predetermined angle.
  • the excitation / extraction of the SPP mode light via the evanescent wave occurs when the low refractive index layer is sufficiently thin. This is because if the low refractive index layer is too thick, the evanescent wave oozes from the organic layer does not reach the metal layer, and the evanescent wave and the SPP mode light cannot exchange energy.
  • the metal layer and the high refractive index layer come close to each other, and the wave number of the SPP mode becomes larger than the equation (2), and the dispersion curve does not intersect with the dispersion curve (3) of propagating light.
  • the light extracted from the SPP is emitted at a predetermined angle corresponding to the intersection of the SPP dispersion curve and the evanescent wave dispersion line as described above.
  • 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 ray and the normal of the incident interface).
  • An interface having a refractive index perpendicular to or nearly perpendicular to the substrate surface was introduced so as to reduce the.
  • the first electrode side structure includes a refractive index modulation structure in which the second refractive index material regions are discretely arranged in the in-plane direction of the first refractive index material layer, A structure having an interface having different refractive indexes that are perpendicular or nearly perpendicular (interface between the first refractive index material layer and the second refractive index material region) was introduced.
  • the refractive index modulation structure as the first electrode side structure is a non-periodic structure having no periodicity even if it has a periodicity (a structure in which the second refractive index material region is periodically arranged). (Structure in which the second refractive index material region is aperiodically arranged) may be used.
  • the refractive index modulation structure is a structure having periodicity
  • the second refractive index material region is periodically arranged two-dimensionally.
  • the diffraction effect (effect refracted at a predetermined angle with respect to the substrate surface) as a transmission diffraction grating (hereinafter simply referred to as “diffraction grating”)
  • the effect as a photonic crystal (Effect of radiating in a direction perpendicular to the substrate surface) is also generated, and waveguide mode light can be extracted to the substrate side.
  • the period (pitch) of the second refractive index material region is sufficiently larger than the wavelength, it is considered that refraction is the dominant mechanism and light is extracted.
  • the period of the second refractive index material region is equal to or less than the wavelength, the effect of the diffraction grating and the effect of the photonic crystal become the dominant mechanism and light is considered to be extracted.
  • FIG. 29 is a schematic cross-sectional view of an organic EL element having a second electrode side structure having an Otto type arrangement. First, the principle of extracting SPP mode light as guided mode light by this second electrode side structure will be described with reference to FIG. In FIG. 29, the first electrode side structure is omitted.
  • n sub is the refractive index of the substrate
  • n OLED is the average refractive index of the first electrode, the organic layer, and the second electrode
  • n 2 is the refractive index of the low refractive index layer
  • ⁇ 2 is the dielectric of the low refractive index layer.
  • ⁇ 1 is the real part of the dielectric constant of the metal layer
  • k sp is the in-plane direction component of the wave number vector of the SPP mode light
  • k 0 is the wave number (2 ⁇ / ⁇ ) of light in vacuum ( ⁇ is from the light emitting layer) The wavelength of the emitted light in vacuum)
  • ⁇ is the propagation angle of the light propagating through the high refractive index layer.
  • Equation (6) the in-plane components of the wave vector match between the SPP mode light and the extracted light, that is, Equation (6) needs to be satisfied. From the equations (5) and (6), the SPP mode light is extracted as propagating light at an angle satisfying the following equation (7).
  • FIG. 30 is a partial schematic cross-sectional view including a first electrode side structure of an organic EL element including a first electrode side structure having a refractive index modulation structure that functions as a transmissive diffraction grating.
  • the principle of extracting light extracted from the SPP mode light by the diffraction grating will be described with reference to FIG. It is assumed that light extracted from the SPP mode light at a predetermined angle ⁇ is diffracted by a diffraction grating having a period (period of the refractive index modulation structure) p.
  • the condition for diffracting to the substrate side at a predetermined angle ⁇ sub with respect to the substrate surface is that the difference between the in-plane wave number of incident light incident on the diffraction grating and the in-plane wave number of diffracted light is an integral multiple of 2 ⁇ / p.
  • N 0, ⁇ 1,...
  • OLED stack indicates a layer through which guided mode light including the first electrode and the organic layer propagates, and the specific layer configuration depends on the specific configuration of the present invention. .
  • the position where the “diffraction grating” is provided also depends on the specific configuration of the present invention. Equation (9) is obtained from Equation (7) and Equation (8).
  • N in Formula (11) may be a positive integer. In order to suppress Fresnel reflection at the interface between the substrate and air, it is desirable that the expression (11) approximately satisfies the following expression.
  • the peak wavelength of the emission spectrum of the light emitting layer is adopted as ⁇ .
  • the peak wavelength the peak wavelength of the photoluminescence spectrum can be used.
  • N is a diffraction order and is an arbitrary integer, but if the diffraction order becomes too large, the directivity of the diffracted light decreases. Therefore, it is preferable to select the period (pitch) p and the wavelength ⁇ so that N satisfying the formula (1) is in the range of 1 ⁇ N ⁇ 3.
  • the above theoretical analysis is a one-dimensional analysis, and a diffraction effect based on this analysis is obtained for a one-dimensional diffraction grating structure (a diffraction grating structure in which gratings are arranged at regular intervals in a predetermined direction). It is done.
  • the one-dimensional diffraction grating structure does not have a grating structure in a direction orthogonal to the one direction, and therefore does not produce a diffraction effect for light in the orthogonal direction (light component).
  • the two-dimensional diffraction grating structure has a grating structure in the orthogonal direction, and a diffraction effect is added also in that direction.
  • the diffraction effect is larger in the two-dimensional diffraction grating structure than in the one-dimensional diffraction grating structure. Accordingly, in an organic EL element having a configuration that satisfies the condition of formula (1) in a predetermined cross section, the light extraction efficiency can be improved regardless of whether the configuration is a one-dimensional diffraction grating structure or a two-dimensional diffraction grating structure.
  • a photonic crystal is a structure whose refractive index is periodically different, in particular, a structure whose period is equal to or less than a wavelength. This periodic structure forms a forbidden band (photonic band gap) in which light in a specific wavelength range cannot exist.
  • the first electrode side structure of the present invention is a periodic refractive index modulation structure and the period is equal to or less than the wavelength
  • the first electrode side structure is a one-dimensional or two-dimensional photonic crystal (respectively a substrate). It can be regarded as a photonic crystal structure in which lattices are arranged at regular intervals in a predetermined direction or two directions in a plane.
  • a one-dimensional photonic crystal In a one-dimensional photonic crystal, light having a wavelength corresponding to the photonic band gap cannot propagate in one direction having a periodic structure. For this reason, the propagation of light is redistributed in directions other than in-plane, and the light can be extracted to the substrate side.
  • the one-dimensional photonic crystal structure since there is no periodic structure in the direction orthogonal to the one direction, there is no photonic band gap in this direction, and there is no extraction effect due to this. small.
  • the two-dimensional photonic crystal structure since the two-dimensional photonic crystal structure has a lattice structure in two different directions in the plane, a photonic band gap is formed in these two directions, and light cannot propagate. Therefore, in the two-dimensional photonic crystal, the direction in which light cannot propagate in the plane increases, and thus light is extracted to the substrate more efficiently than the one-dimensional structure.
  • the first electrode side structure is a non-periodic structure having no periodicity in the in-plane direction of the substrate, light incident on the first electrode structure is diffracted at random positions and phases. Radiation angle light is not emitted intensifying each other. Therefore, by having such a structure on the first electrode side, relatively uniform (highly diffusible) orientation characteristics can be obtained. That is, in the case where the first electrode side structure is a periodic structure, it is possible to obtain an alignment characteristic in which the light intensity at a specific radiation angle is increased by the effect of strengthening the emitted light by the diffraction grating, When the first electrode side structure is an aperiodic structure, relatively uniform alignment characteristics can be obtained. Therefore, the first electrode side structure can be selected to be a structure having periodicity or a non-periodic structure according to a required light distribution characteristic.
  • FIG. 3 The light propagation method indicated by the arrows in FIG. 3 is schematically shown in order to easily understand the principle of the action effect by refraction.
  • the reference numeral 8a is a first refractive index material layer made of a high refractive index material and the reference numeral 8b is a second refractive index material region made of a low refractive index material will be described as an example.
  • the light traveling toward the cathode 4 is incident at the interface between the cathode 4 and the low refractive index layer 5 at a large incident angle greater than the critical angle (arrow A1)
  • an evanescent wave (arrow A2) is generated in the low refractive index layer 5.
  • the generated evanescent wave oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (arrow A3) is excited.
  • the excited SPP is radiated to the cathode 4 at a predetermined angle (arrow A5) through resonance with the evanescent wave (arrow A4), and can be extracted to the organic layer 3 as propagating light.
  • a predetermined angle arrow A5
  • arrow A4 evanescent wave
  • the arrow A1 is used to explain the effect of refraction of the present invention. It only shows the propagation of part of the light. The same applies to other lights.
  • refraction occurs at the interface of materials having different refractive indexes, the refraction action is not shown in the drawing for the interface that is not particularly necessary for explaining the effect of the present invention.
  • the light B1 travels from the first refractive index material layer 8a to the second refractive index material region 8b, it is refracted toward the substrate 1 at the interface 9 thereof.
  • the substrate for example, glass
  • the light extraction efficiency is improved by having the configuration including the interface 9 between the first refractive index material layer 8a and the second refractive index material region 8b.
  • the light C1 is light that travels to the substrate 1 side in a direction perpendicular to the substrate.
  • the light C1 is not refracted at the interface between the organic layer 3 and the anode 2, the interface between the anode 2 and the first refractive index material layer 8a, and the interface between the first refractive index material layer 8a and the substrate 1; 2, the first refractive index material layer 8 a, the substrate 1, and taken out to the outside.
  • the light C2 is refracted to the substrate 1 side at the interface 9 between the first refractive index material layer 8a and the second refractive index material region 8b, passes through the second refractive index material region 8b, and is transmitted to the second refractive index material region 8b. After being refracted at the interface between the substrate 1 and the substrate 1, it can be taken out through the substrate 1. In the configuration without the interface 9 between the first refractive index material layer 8a and the second refractive index material region 8b, total reflection occurs at the interface between the substrate 1 and air, but the first refractive index material layer 8a and the second refractive index material region.
  • the incident angle to the substrate 1 is changed to a small angle due to refraction at the interface 9 with 8b, the light that does not cause total reflection increases and the light extraction efficiency is improved. That is, the light extraction efficiency is improved by having the configuration including the interface 9 between the first refractive index material layer 8a and the second refractive index material region 8b.
  • the light C3 also has a smaller incident angle to the substrate 1 due to refraction at the interface 9 between the first refractive index material layer 8a and the second refractive index material region 8b, so that light that can avoid total reflection increases. This improves the light extraction efficiency.
  • the second refractive index material region is periodically arranged, so that the first refractive index material layer and the second refractive index material region are a diffraction grating.
  • the effect of the diffraction grating will be schematically described with reference to FIG.
  • the light propagation method indicated by the arrows in FIG. 4 is schematically shown for easy understanding of the principle of the effect of the diffraction grating.
  • the light traveling toward the cathode 4 is incident at the interface between the cathode 4 and the low refractive index layer 5 at a large incident angle greater than the critical angle (arrow A1)
  • an evanescent wave (arrow A2) is generated in the low refractive index layer 5.
  • the generated evanescent wave oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (arrow A3) is excited.
  • the excited SPP is radiated to the cathode 4 at a predetermined angle (arrow A5) through resonance with the evanescent wave (arrow A4), and can be extracted to the organic layer 3 as propagating light.
  • the light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to point B propagates through the organic layer 3 and the anode 2 and enters the refractive index modulation structure 8 as a diffraction grating.
  • the incident light is diffracted by a diffraction grating in a predetermined direction (a direction satisfying the Nth order strengthening condition).
  • diffracted light is emitted at a certain predetermined angle because the diffracted light at each diffraction point is emitted while interfering.
  • arrows BD1 and BD2 light incident on the interface between the substrate (for example, glass) and air at a critical angle or less is directly extracted outside.
  • arrow BD1 and the arrow BD2 are strengthened by interference as described above, it is possible to extract light having a strong intensity at a specific angle, and the light extraction efficiency is improved.
  • an arrow BD3r light incident on the interface between the substrate and air at an angle greater than the critical angle is totally reflected (arrow BD3r) and cannot be extracted outside the substrate.
  • the material of the metal layer and the low refractive index layer, and the diffraction grating (refractive index modulation structure) so as to satisfy the formula (1) are satisfied. It is preferable to select a period.
  • the intensity of the diffracted light is higher as the order N is smaller, it is preferable to select the period of the diffraction grating and the like so as to satisfy the formula (1) as the order N is smaller.
  • Expression (1) when Expression (1) is satisfied, the generated SPP light can be efficiently extracted from the substrate 1 by the diffraction grating, and the light extraction efficiency can be improved.
  • the second refractive index material region and the second refractive index material region are arranged periodically with a period equal to or less than the wavelength of light.
  • the effect of the photonic crystal will be schematically described with reference to FIG.
  • the light propagation method indicated by the arrows in FIG. 5 is schematically shown in order to easily understand the principle of the effect of the photonic crystal.
  • the light traveling toward the cathode 4 is incident at the interface between the cathode 4 and the low refractive index layer 5 at a large incident angle greater than the critical angle (arrow A1)
  • an evanescent wave (arrow A2) is generated in the low refractive index layer 5.
  • the generated evanescent wave oozes out to the interface between the metal layer 6 and the low refractive index layer 5, and the surface plasmon polariton SPP (arrow A3) is excited.
  • the excited SPP is radiated to the cathode 4 at a predetermined angle (arrow A5) through resonance with the evanescent wave (arrow A4), and can be extracted to the organic layer 3 as propagating light.
  • the light extracted from the cathode side structure (cathode 4, low refractive index layer 5, metal layer 6) to point B propagates through the organic layer 3 and the anode 2 and enters the photonic crystal structure.
  • a structure having a wavelength equal to or smaller than the wavelength of light exists in two dimensions, a photonic band gap acts in the two-dimensional direction, and light cannot propagate in the two-dimensional direction (light confinement effect in the two-dimensional direction).
  • the periodic structure is formed in the refractive index modulation structure 8
  • the propagation of light is restricted in the direction of the arrow CD2 parallel to the substrate.
  • the photonic crystal structure is not formed in the direction perpendicular to the substrate, the propagation of light is not limited. By this mechanism, light travels in a direction perpendicular to the substrate. Since the direction of the arrow CD1 is perpendicular to the substrate, light can be extracted efficiently without being totally reflected even at the interface between the substrate and air.
  • the refractive index modulation structure has a configuration in which the first refractive index material layer 8a shown in FIG. 3 is made of a high refractive index material and the second refractive index material region 8b is made of a low refractive index material,
  • the refractive index material layer 8a may be made of a low refractive index material, and the second refractive index material region 8b may be made of a high refractive index material.
  • the effect of refraction by this refractive index modulation structure is equal if the period (pitch) and size are equal.
  • the effects of the diffraction grating and the photonic crystal are also the same.
  • reference numeral 8Aa is a first refractive index material layer constituting the refractive index modulation structure 8A
  • reference numeral 8Ab is a second refractive index material region.
  • the second refractive index material regions 8Ab are discretely arranged on one surface of the anode 2.
  • the first refractive index material layer 8Aa is composed of a sea-shaped portion disposed between the second refractive index material regions 8Ab that are discretely disposed and a continuous film portion composed of continuous layers.
  • reference numeral 8 ⁇ / b> Aa may be a second refractive index material region
  • reference numeral 8 ⁇ / b> Ab may be a first refractive index material layer.
  • the second refractive index material region 8Aa is composed of island portions that are discretely arranged and a continuous film portion that is formed of continuous layers.
  • Either the first refractive index material or the second refractive index material may be a high refractive index material or a low refractive index material.
  • reference numeral 8Ba is a first refractive index material layer constituting the refractive index modulation structure 8B
  • reference numeral 8Bb is a second refractive index material region.
  • the second refractive index material region 8 ⁇ / b> Ab is configured to be discretely arranged on one surface of the anode 2, but in the example shown in FIG. 7, the second refractive index material region 8 ⁇ / b> Bb. Is a configuration arranged discretely on the substrate 1.
  • the first refractive index material layer 8Ba is composed of a sea-like portion disposed between the second refractive index material regions 8Bb that are discretely disposed and a continuous film portion composed of continuous layers.
  • reference numeral 8 ⁇ / b> Ba may be a second refractive index material region
  • reference numeral 8 ⁇ / b> Bb may be a first refractive index material layer
  • the second refractive index material region 8Ba is composed of an island-like portion in which the second refractive index material regions 8Ba are discretely arranged and a continuous film portion formed of continuous layers.
  • the first refractive index material or the second refractive index material may be a high refractive index material or a low refractive index material.
  • reference numeral 8Ca is a first refractive index material layer constituting the refractive index modulation structure 8C
  • reference numeral 8Cb is a second refractive index material region.
  • the second refractive index material region 8Ab is in contact with the anode 2
  • the second refractive index material region 8Bb is in contact with the substrate 1
  • the second refractive index material region 8 ⁇ / b> Cb is configured not to contact the anode 2 or the substrate 1.
  • the first refractive index material layer 8Ca is composed of a sea-like portion disposed between the discretely disposed second refractive index material regions 8Cb and a continuous film portion composed of continuous layers.
  • the reference numeral 8Ca may be the second refractive index material region
  • the reference numeral 8Cb may be the first refractive index material layer.
  • the second refractive index material region 8Ca includes an island-like portion in which the second refractive index material regions 8Ca are discretely arranged and a plurality of continuous film portions including continuous layers.
  • the first refractive index material or the second refractive index material may be a high refractive index material or a low refractive index material.
  • reference numeral 8Da is a first refractive index material layer constituting the refractive index modulation structure 8D
  • reference numeral 8Db is a second refractive index material region
  • the reference numeral 8Da may be the second refractive index material region constituting the refractive index modulation structure 8D
  • the reference numeral 8Db may be the first refractive index material layer.
  • the first refractive index material layer 8Da is composed of a sea-like portion disposed between the second refractive index material regions 8Db and a continuous film portion composed of continuous layers. .
  • the second refractive index material region 8Db is composed of island portions that are discretely arranged and a continuous film portion that includes continuous layers.
  • the reference numeral 8Db is the first refractive index material layer
  • the first refractive index material layer 8Db is composed of a sea-like portion disposed between the second refractive index material regions 8Da and a continuous film portion composed of continuous layers. Is done.
  • the second refractive index material region 8Da is composed of island portions that are discretely arranged and a continuous film portion that is composed of continuous layers.
  • the first refractive index material or the second refractive index material may be either a high refractive index material or a low refractive index material.
  • reference numeral 8Ea is a first refractive index material layer constituting the refractive index modulation structure 8E
  • reference numeral 8Eb is a second refractive index material region.
  • the second refractive index material region may have a T-shaped structure or an inverted T-shaped structure.
  • the configuration may be such that the reference numeral 8Ea is the second refractive index material region and the reference numeral 8Eb is the first refractive index material layer.
  • region may be sufficient.
  • the first refractive index material or the second refractive index material may be a high refractive index material or a low refractive index material.
  • the shape of the second refractive index material region is not particularly limited as long as it exhibits the refraction effect, diffraction effect, or photonic crystal effect of the present invention.
  • the interface between the second refractive index material region and the first refractive index material layer is preferably configured so that the angle with respect to the substrate surface is 5 ° or more, and 60 ° or more. Is more preferable, and 75 ° or more is even more preferable.
  • the propagating light re-radiated from the light emitting position toward the second electrode side and the propagating light re-radiated from the SPP mode light is incident on the interface from the outside and refracted to the substrate side, It can be efficiently taken out from the outer surface of the substrate.
  • the interface between the second refractive index material region and the first refractive index material layer shown in FIGS. 1 to 10 is a flat surface, but may include a curved surface.
  • reference numeral 8Fa is a first refractive index material layer constituting the refractive index modulation structure 8F
  • reference numeral 8Fb is a second refractive index material region.
  • the second refractive index material region has a rectangular cross section, but in the example shown in FIG. 11, the second refractive index material region has a circular cross section.
  • Either the first refractive index material or the second refractive index material may be a high refractive index material or a low refractive index material.
  • FIG. 12 is a schematic cross-sectional view for explaining an example of the organic EL element according to the second embodiment of the present invention.
  • FIG. 13 is a perspective view of the organic EL element according to the second embodiment shown in FIG. In order to make the features of the invention easy to understand, the Otto type arrangement structure is shown separately.
  • the organic EL element 20 shown in FIGS. 12 and 13 includes an anode (first electrode) 22, an organic layer 23 including a light emitting layer, and a cathode (second electrode) 24 in this order on a substrate 21. It is an element.
  • a low refractive index layer 25 having a thickness of 20 nm to 300 nm and a metal layer 26 are sequentially provided on the surface of the cathode 24 opposite to the organic layer 23 from the side in contact with the opposite surface.
  • the cathode 24 is made of a translucent conductive material, and the refractive index of the low refractive index layer 25 is lower than the refractive index of the organic layer 23.
  • a plurality of substrate recesses 21aa discretely formed on the surface layer 21a of the substrate 21 are provided with a refractive index modulation structure 28 filled with a material different from the refractive index of the substrate 21.
  • the refractive index modulation structure 28 includes a substrate convex portion 21ab provided in the surface layer 21a of the substrate 21 and a refractive index modulation region 28a in which the discretely formed substrate concave portions 21aa are filled with a material different from the refractive index of the substrate 21. Is done.
  • the refractive index modulation structure 28 of the present embodiment is the same as the refractive index modulation structure of the first embodiment in that it is formed of regions made of two types of materials having different refractive indexes.
  • one (second refractive index material region) is the other region (second refractive index material region) out of regions made of two types of materials having different refractive indexes without using the substrate as a component.
  • the refractive index modulation structure 28 of the present embodiment includes a substrate as a constituent element and the surface layer 21 a of the substrate 21.
  • the substrate convex portion 21ab included in FIG. 1 corresponds to the first refractive index material layer
  • the refractive index modulation region 28a corresponds to the second refractive index material region.
  • the refractive index modulation regions 28a arranged discretely may be arranged periodically or arranged aperiodically.
  • the plurality of refractive index modulation regions 28a that are discretely arranged may have the same shape or different shapes. Even in the case where the refractive index modulation structure 28 is arranged in a discrete manner by one region (refractive index modulation region 28a) discretely arranged as in the checker pattern, the other (substrate convex portion 21ab) is also discretely arranged. Good.
  • One of the discretely arranged regions is composed of a plurality of island-like portions that are discretely arranged and a continuous film portion that is composed of continuous layers that are in contact with the plurality of island-like portions. It may be a structure.
  • the period (pitch) p is the same as that described above with respect to a certain integer N (1 ⁇ N ⁇ 3). It is preferable to select so as to satisfy the formula (1). At this time, since the period p varies depending on the material of the metal layer 26 and the low refractive index layer 25, it is preferable to consider the selection of the material. In FIG. 12, the period p of the refractive index modulation region 28a is shown.
  • the refractive index modulation regions 28a and the substrate protrusions 21ab are arranged by periodically arranging the refractive index modulation regions 28a that are discretely arranged with a period p less than or equal to the wavelength of light. May be configured to form a photonic crystal.
  • any material having a refractive index different from that of the substrate 21 can be used.
  • the same high refractive index material and low refractive index material that constitute the refractive index modulation structure of the first embodiment can be used.
  • the thickness of the refractive index modulation structure 28 can also be the same as that of the refractive index modulation structure of the first embodiment.
  • the mechanism by which the light extraction efficiency in the organic EL element of the present embodiment is improved is the same as in the first embodiment. That is, the light extraction efficiency is improved by the refraction effect, the action effect by the diffraction grating, and the action effect by the photonic crystal.
  • the refraction effect is generated by the interface 29 between the substrate convex portion 21ab and the refractive index modulation region 28a.
  • the effect of the diffraction grating is generated when the refractive index modulation region 28 is periodically arranged (period p) and the substrate convex portion 21ab and the refractive index modulation region 28a form a diffraction grating.
  • the effect of the photonic crystal is that the refractive index modulation region 28 is periodically arranged with a period p less than or equal to the wavelength of light, so that the substrate convex portion 21ab and the refractive index modulation region 28a form a photonic crystal.
  • FIG. 14 is a schematic cross-sectional view for explaining an example of the organic EL element according to the third embodiment of the invention.
  • FIG. 15 is a perspective view of the organic EL element according to the third embodiment shown in FIG. In order to make the features of the invention easy to understand, the Otto type arrangement structure is shown separately.
  • the organic EL element 30 shown in FIGS. 14 and 15 includes an anode (first electrode) 32, an organic layer 33 including a light emitting layer, and a cathode (second electrode) 34 in this order on a substrate 31. It is an element.
  • a surface of the cathode 34 opposite to the organic layer 33 is provided with a low refractive index layer 35 having a thickness of 20 nm or more and 300 nm or less and a metal layer 36 in order from the side in contact with the opposite surface.
  • the cathode 34 is made of a translucent conductive material, and the refractive index of the low refractive index layer 35 is lower than the refractive index of the organic layer 33.
  • the surface layer 31a of the substrate 31 includes a refractive index modulation structure 38 in which a material different from the refractive index of the substrate is formed so as to cover the side surfaces 31abA of the plurality of substrate convex portions 31ab formed discretely. .
  • the refractive index modulation structure 38 is made of a material different from the refractive index of the substrate so as to cover the plurality of substrate protrusions 31ab discretely formed on the surface layer 31a of the substrate 31 and the side surface 31abA of the substrate protrusion 31ab.
  • the refractive index modulation region 38a is formed.
  • the refractive index modulation structure 38 of the present embodiment is similar to the refractive index modulation structure of the second embodiment in that the substrate is a constituent element.
  • the substrate convex portion 21ab included in the surface layer 21a of the substrate 21 corresponds to the first refractive index material layer
  • the refractive index modulation region 28a corresponds to the second refractive index material region.
  • the refractive index modulation region 38a corresponds to the first refractive index material layer
  • the substrate convex portion 31ab corresponds to the second refractive index material region. Is different.
  • the substrate protrusions 31ab arranged discretely may be arranged periodically or arranged aperiodically.
  • the plurality of substrate convex portions 31ab arranged discretely may all have the same shape or may include different shapes. Even in the case where the refractive index modulation structure 38 has a discrete arrangement, the other (refractive index modulation area 38a) is arranged discretely by one area (substrate convex portion 31ab) arranged discretely, like a checker pattern. Good.
  • the other region is a continuous layer composed of a sea-like portion arranged between one region (substrate convex portion 31ab) arranged discretely and a continuous layer in contact with this sea-like portion.
  • a structure composed of a film part may be used.
  • the period (pitch) p is the above-described formula for a certain integer N (1 ⁇ N ⁇ 3). It is preferable to select so as to satisfy (1). At this time, since the period p varies depending on the material of the metal layer 36 and the low refractive index layer 35, it is preferable to consider the selection of the material. In FIG. 14, the period p of the board
  • the substrate convex portions 31ab and the refractive index modulation region 38a are arranged in a photo by disposing the substrate convex portions 31ab arranged discretely periodically with a period p equal to or less than the wavelength of light. It is good also as a structure which makes a nick crystal.
  • any material having a refractive index different from that of the substrate 31 can be used.
  • the same high refractive index material and low refractive index material that constitute the refractive index modulation structure of the first embodiment can be used.
  • the thickness of the refractive index modulation structure 38 can be the same as that of the refractive index modulation structure of the first embodiment.
  • the mechanism by which the light extraction efficiency in the organic EL element of the present embodiment is improved is the same as in the first embodiment. That is, the light extraction efficiency is improved by the refraction effect, the action effect by the diffraction grating, and the action effect by the photonic crystal.
  • the refraction effect is generated by the interface 39 between the substrate convex portion 31ab and the refractive index modulation region 38a.
  • the effect of the diffraction grating is generated when the refractive index modulation region 38 is periodically arranged (period p) and the substrate convex portion 31ab and the refractive index modulation region 38a form a diffraction grating.
  • the effect of the photonic crystal is that the refractive index modulation region 38 is periodically arranged with a period p less than or equal to the wavelength of light, so that the substrate convex portion 31ab and the refractive index modulation region 38a form a photonic crystal.
  • FIG. 16 is a diagram illustrating an example of an image display device including the organic EL element.
  • An image display device 100 shown in FIG. 16 is a so-called passive matrix type image display device.
  • an anode wiring 104, an anode auxiliary wiring 106, a cathode wiring 108, an insulating film 110, and a cathode partition 112 are provided.
  • a sealing plate 116 and a sealing material 118 are provided.
  • a plurality of anode wirings 104 are formed on the substrate 1 of the organic EL element 10.
  • the anode wirings 104 are arranged in parallel at a constant interval.
  • the anode wiring 104 is made of a transparent conductive film, and for example, ITO (Indium Tin Oxide) can be used.
  • the thickness of the anode wiring 104 can be set to 100 nm to 150 nm, for example.
  • An anode auxiliary wiring 106 is formed on the end portion of each anode wiring 104, and the anode auxiliary wiring 106 is electrically connected to the anode wiring 104.
  • the anode auxiliary wiring 106 functions as a terminal for connecting to the external wiring on the end side of the substrate 1, and the anode auxiliary wiring 106 is routed from a driving circuit (not shown) provided outside. Thus, current can be supplied to the anode wiring 104.
  • the anode auxiliary wiring 106 is made of a metal film having a thickness of 500 nm to 600 nm, for example.
  • a plurality of cathode wirings 108 are provided on the organic EL element 10.
  • the plurality of cathode wirings 108 are arranged so as to be parallel to each other and orthogonal to the anode wiring 104.
  • Al or an Al alloy can be used for the cathode wiring 108.
  • the thickness of the cathode wiring 108 is, for example, 100 nm to 150 nm.
  • a cathode auxiliary wiring (not shown) is provided at the end of the cathode wiring 108, similarly to the anode auxiliary wiring 106 for the anode wiring 104, and is electrically connected to the cathode wiring 108. This electrical connection allows a current to flow between the cathode wiring 108 and the cathode auxiliary wiring.
  • 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.
  • the organic EL element 10 is provided in the opening 120 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.
  • the film thickness of the insulating film 110 can be, for example, 200 nm to 100 nm, and the size of the opening 120 can be, for example, 100 ⁇ m ⁇ 100 ⁇ m.
  • the organic EL element 10 is located between the anode wiring 104 and the cathode wiring 108 in the opening 120. In this case, the anode 2 of the organic EL element 10 is in contact with the anode wiring 104 and the cathode 4 is in contact with the cathode wiring 108.
  • the thickness of the organic EL element 10 can be set to, for example, 150 nm to 200 nm.
  • a plurality of cathode partition walls 112 are formed on the insulating film 110 along a direction perpendicular to the anode wiring 104.
  • the cathode partition 112 plays a role for spatially separating the plurality of cathode wirings 108 so that the wirings of the cathode wirings 108 do not conduct with each other. Accordingly, the cathode wiring 108 is disposed between the adjacent cathode partition walls 112.
  • the size of the cathode partition 112 for example, the one having a height of 2 ⁇ m to 3 ⁇ m and a width of 10 ⁇ m can be used.
  • the substrate 1 is bonded through a sealing plate 116 and a sealing material 118. Thereby, the space in which the organic EL element 10 is provided can be sealed, and the organic EL element 10 can be prevented from being deteriorated by moisture in the air.
  • a sealing plate 116 for example, a glass substrate having a thickness of 0.7 mm to 1.1 mm can be used.
  • a current can be supplied to the organic EL element 10 via the anode auxiliary wiring 106 and the cathode auxiliary wiring (not shown) by a driving device (not shown) to cause the light emitting layer to emit light. Then, light can be emitted 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.
  • FIG. 17 is a diagram illustrating an example of a lighting device including the organic EL element 10 described above.
  • the lighting device 200 shown in FIG. 17 includes the organic EL element 10 described above, and a terminal 202 that is installed adjacent to the substrate 1 (see FIG. 1) of the organic EL element 10 and connected to the anode 2 (see FIG. 1).
  • the terminal 203 is connected to the cathode 4 (see FIG. 1), and the lighting circuit 201 is connected to the terminal 202 and the terminal 203 to drive the organic EL element 10.
  • the lighting circuit 201 has a DC power supply (not shown) and a control circuit (not shown) inside, and supplies a current between the anode layer 2 and the cathode 4 of the organic EL element 10 through the terminal 202 and the terminal 203.
  • the supplied current drives the organic EL element 10 to cause the light emitting layer to emit light.
  • the emitted light is emitted to the outside through the substrate 1 and can be 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.
  • a first refractive index material layer 8 a is formed on the substrate 1.
  • the formation method of this 1st refractive index material layer 8a is not specifically limited.
  • a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • the hole 8h (see FIG. 18E) is formed.
  • a forming method for example, a method using photolithography can be used. In order to do this, as shown in FIG. 18B, first, a positive resist solution is applied onto the first refractive index material layer 8a, and the excess resist solution is removed by spin coating or the like, so that a resist layer is formed. R1 is formed.
  • FIG. 18C when a mask (not shown) on which a predetermined pattern for forming the hole 8h is drawn is put on and exposed with ultraviolet rays (UV), electron beams (EB), etc., it is shown in FIG. 18C.
  • a predetermined pattern corresponding to the hole 8h is exposed to the resist layer R1 (exposed portion R1a).
  • the resist layer R1a in the exposed pattern portion is removed using a developer. Thereby, the surface of the first refractive index material layer 8a is exposed corresponding to the exposed pattern portion (FIG. 18D).
  • the exposed portion of the first refractive index material layer 8a is removed by etching to form a hole 8h.
  • etching either dry etching or wet etching can be used.
  • the shape of the hole 8h can be controlled by combining isotropic etching and anisotropic etching.
  • dry etching reactive ion etching (RIE) or inductively coupled plasma etching can be used.
  • RIE reactive ion etching
  • wet etching a method of immersing in dilute hydrochloric acid, dilute sulfuric acid, or hydrofluoric acid can be used.
  • the first refractive index material layer 8a is penetrated, but it may be non-penetrated.
  • the hole 8h is filled with the second refractive index material to form the second refractive index material region 8b.
  • the refractive index modulation structure 8 including the first refractive index material layer 8a and the second refractive index material region 8b is formed.
  • the formation of the second refractive index material region 8b is not particularly limited as in the method of forming the first refractive index material layer 8a.
  • the resistance heating vapor deposition method, the electron beam vapor deposition method, the sputtering method, the ion plating method In addition to various dry processes such as a CVD method, various wet processes such as a coating method can be used.
  • various wet processes such as a coating method can be used.
  • the hole 8h is filled.
  • the structure shown in FIG. 10 can also be formed by performing these steps of FIG. 18B to FIG. 18F a plurality of times.
  • the anode 2 is formed on the first refractive index material layer 8a and the second refractive index material region 8b.
  • the formation method of this anode 2 is not specifically limited.
  • a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • 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.
  • anode buffer layer (not shown) instead of or in addition to the surface treatment of the surface treatment of the anode 2.
  • anode buffer layer is produced by applying a wet process, spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method.
  • the film can be formed by using a coating method such as a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, and an inkjet printing method.
  • the anode buffer layer When the anode buffer layer is produced by a dry process, the anode buffer layer can be formed by using a plasma treatment or the like exemplified in Japanese Patent Application Laid-Open No. 2006-303412.
  • 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.
  • an organic layer 3 including a light emitting layer made of an organic EL material is formed on the anode 2.
  • a polishing process, an etching process, or the like for flattening may be appropriately performed.
  • 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.
  • the cathode 4 is formed on the organic layer 3.
  • the method for forming the cathode 4 can be the same as the method for forming the anode 2 and is not particularly limited.
  • a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • the low refractive index layer 5 is formed on the cathode 4.
  • the method for forming the low refractive index layer 5 is not particularly limited. For example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • 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.
  • a metal layer 6 is formed on the low refractive index layer 5 as shown in FIG.
  • the method for forming the metal layer 6 is not particularly limited. For example, vapor deposition or sputtering can be used.
  • the organic EL element 10 can be manufactured by the above process. After these series of steps, it is preferable to use the organic EL element 10 stably for a long period of time and to attach a protective layer and a protective cover (not shown) for protecting the organic EL element 10 from the outside.
  • a protective layer polymer compounds, metal oxides, metal fluorides, metal borides, silicon compounds such as silicon nitride and silicon oxide, and the like can be used. And these laminated bodies can also be used.
  • As the protective cover a glass plate, a plastic plate whose surface is subjected to low water permeability treatment, a metal, or the like can be used.
  • the protective cover is preferably bonded to the substrate 1 with a thermosetting resin or a photocurable resin and sealed.
  • 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.
  • an inert gas such as nitrogen, argon or helium
  • FIG. 19A In order to form the substrate recess 21aa (FIG. 19E) on the substrate 21, for example, a method using photolithography can be used. In order to do this, as shown in FIG. 19A, first, a positive resist solution is applied onto the substrate 21, and the excess resist solution is removed by spin coating or the like to form a resist layer R2.
  • the resist layer R2 Covering the formed resist layer R2 with a mask (not shown) on which a predetermined pattern for forming the substrate recess 21aa is drawn, and performing exposure with ultraviolet rays (UV), electron beams (EB), etc., As shown in FIG. 19B, the resist layer R2 is exposed with a predetermined pattern corresponding to the substrate recess 21aa (exposed portion R2a). Then, the resist layer R2a 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. 19C).
  • UV ultraviolet rays
  • EB electron beams
  • the exposed portion of the substrate 1 is removed by etching to form a substrate recess 21aa.
  • etching either dry etching or wet etching can be used.
  • the shape of the substrate recess 21aa can be controlled by combining isotropic etching and anisotropic etching.
  • dry etching reactive ion etching (RIE) or inductively coupled plasma etching can be used.
  • wet etching a method of immersing in dilute hydrochloric acid or dilute sulfuric acid can be used.
  • the substrate recess 21aa is filled with a refractive index modulation material to form a refractive index modulation region 28a.
  • the refractive index modulation structure 28 is formed on the surface layer 21 a of the substrate 21.
  • the method for forming the refractive index modulation region 28a is not particularly limited. For example, in addition to various dry processes such as resistance heating vapor deposition, electron beam vapor deposition, sputtering, ion plating, and CVD, various wet processes such as coating can be used.
  • the anode 22 is formed on the substrate convex portion 21ab and the refractive index modulation region 28a.
  • the formation method of this anode 22 is not specifically limited. For example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • 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.
  • anode buffer layer (not shown) instead of or in addition to the surface treatment of the surface treatment of the anode 22.
  • the anode buffer layer is produced by applying a wet process, spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method.
  • the film can be formed by using a coating method such as a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, and an inkjet printing method.
  • the anode buffer layer When the anode buffer layer is produced by a dry process, the anode buffer layer can be formed by using a plasma treatment or the like exemplified in Japanese Patent Application Laid-Open No. 2006-303412.
  • 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.
  • an organic layer 23 including a light emitting layer made of an organic EL material is formed on the anode 22.
  • polishing or etching for flattening may be appropriately performed.
  • a conventionally known method can be used to form the organic layer 23 and is not limited. For example, methods such as a vacuum deposition method, a spin coating method, a casting method, and an LB method can be used.
  • the cathode 24 is formed on the organic layer 23.
  • the cathode 24 can be formed by the same method as the anode 22 and is not limited. For example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • a low refractive index layer 25 is formed on the cathode 24.
  • the method for forming the low refractive index layer 25 is not particularly limited. For example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a CVD method, or the like can be used.
  • the low-refractive index layer 25 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 using photolithography in the SOG layer.
  • 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.
  • a metal layer 26 is formed on the low refractive index layer 25 as shown in FIG.
  • the formation method of the metal layer 26 is not specifically limited, For example, a vapor deposition method and sputtering can be used.
  • the organic EL element 30 of the third embodiment can be formed by changing the shape of the mask used for the exposure in FIG. 19B or by using a negative resist as the resist to be used.
  • the organic EL element 20 can be manufactured by the above process. After these series of steps, like the organic EL element 10, the organic EL element 20 is stably used for a long period of time, and a protective layer and a protective cover (not shown) for protecting the organic EL element 20 from the outside are mounted.
  • a protective layer polymer compounds, metal oxides, metal fluorides, metal borides, silicon compounds such as silicon nitride and silicon oxide, and the like can be used. And these laminated bodies can also be used.
  • As the protective cover a glass plate, a plastic plate whose surface is subjected to low water permeability treatment, a metal, or the like can be used.
  • the protective cover is preferably bonded to the substrate 21 with a thermosetting resin or a photocurable resin and sealed.
  • a spacer because a predetermined space can be maintained and the organic EL element 20 can be prevented from being damaged. If an inert gas such as nitrogen, argon, or helium is sealed in this space, it is easy to prevent the upper metal layer 26 from being oxidized. In particular, when helium is used, heat conduction is high, and thus heat generated from the organic EL element 20 when voltage is applied can be effectively transmitted to the protective cover, which is preferable.
  • a desiccant such as barium oxide in this space, it is easy to suppress the moisture adsorbed in the series of manufacturing steps from damaging the organic EL element 20.
  • FIG. 20 shows the result of energy dissipation calculation in which the intensity of light emitted from the organic layer is developed with the wave number component in the organic EL element surface direction.
  • the horizontal axis represents the wave number of the light emitted from the organic layer, the organic EL element surface direction component divided by the vacuum wave number k 0 , that is, the effective refractive index, and the vertical axis represents the light intensity of the wave number, that is, the development.
  • the coefficient is shown.
  • the calculation was performed separately for the TM polarization component and the TE polarization component. This calculation shows the result of an organic EL element in which a flat anode, an organic layer, and a cathode (metal) are laminated on a substrate (glass).
  • the peak area on the highest wavenumber side of TM polarized light represents the intensity of the SPP mode light, but it can be seen that most of the light emitted from the organic layer is captured as the SPP mode light.
  • the film thicknesses of the anode and the organic layer are 150 nm and 100 nm, respectively.
  • FIG. 21 shows the dependence of the intensity of the light (TM polarization component) emitted from the organic layer on the energy dissipation calculation in the Otto type organic EL element, depending on the film thickness of the low refractive index layer.
  • the Otto type organic EL device has the same structure as the device of FIG. 20 in the substrate, the anode, and the organic layer, but a cathode (50 nm) made of ITO, which is a transparent conductive material, is formed on the organic layer. Further, a low refractive index layer and a metal layer are sequentially formed.
  • the refractive index of the low refractive index layer is 1.38
  • FIG. 21A shows a case where the metal layer is Al
  • FIG. 21B shows the case where the metal layer is Ag.
  • the film thickness (nm) is shown.
  • the peak change will be described below with reference to FIGS. 22 (a), (b), and (c).
  • the light is completely trapped on the surface of the metal layer as SPP mode light. This represents the time when the film thickness of the low refractive index layer is 0 nm, and the SPP mode light attenuates rapidly while propagating in the in-plane direction through the interface between the metal layer and the cathode, and thus the peak width is large. .
  • the film thickness of the low refractive index layer increases, it becomes as shown in FIG. 22B, and the SPP mode light and the waveguide mode light are mixed due to the Otto type arrangement.
  • the extracted SPP mode light becomes guided mode light, and is again captured as SPP mode light by the metal layer by interface reflection.
  • the peak width is gradually narrowed.
  • the film thickness of the low refractive index layer becomes sufficiently large, it becomes as shown in FIG.
  • the Otto type arrangement is used, the evanescent wave at the light emitting point does not reach the metal layer and is not captured as SPP mode light.
  • the emitted light is captured as guided mode light. That is, when the thickness of the low refractive index layer 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.
  • the wave number k SPP of the surface plasmon polariton (SPP) generated on the surface of the metal layer can be expressed by the following formula (13).
  • ⁇ 1 is the dielectric constant of the metal layer
  • ⁇ 2 is the dielectric constant of the low refractive index layer
  • k 0 is the wave number of light in vacuum at the peak wavelength of light emitted from the light emitting layer.
  • the real part can be expressed by the following equation (14).
  • the vertical component of the wave number in the low refractive index layer of surface plasmon polariton (SPP) generated on the surface of the metal layer can be expressed by the following formula (15).
  • FIG. 24A is a graph showing the equation (16) when the metal layer is Al and (b) is the metal layer Ag.
  • the strength of the surface plasmon polariton (SPP) generated on the surface of the metal layer in the equation (16) at the low refractive index layer / cathode interface is:
  • the intensity on the surface of the metal layer is normalized as 1
  • the peak of the thickness of the low refractive index layer where the intensity of the surface plasmon polariton (SPP) at the position propagated in the thickness direction of the low refractive index layer is 0.4 or less. It can be seen that the width is saturated to a certain value.
  • the SPP mode light is extracted into the organic layer by the Otto arrangement.
  • a certain value for example, 0.4
  • the refractive index of the low refractive index layer and the material of the cathode are not limited.
  • the FDTD method is an analysis method for tracking the time change of the electromagnetic field at each point in space by differentiating Maxwell's equation describing the time change of the electromagnetic field spatially and temporally. More specifically, it is a technique in which the light emission in the light emitting layer is regarded as radiation from a minute dipole and the time variation of the radiation (electromagnetic field) is tracked. The simulation result shows the result of light extraction to the substrate.
  • ⁇ on the horizontal axis is the wavelength in vacuum
  • ⁇ on the vertical axis is the light extraction efficiency (ratio of the light intensity extracted from the substrate to the total radiation intensity from the dipole).
  • the calculation was performed with a dipole as a light emission source being random (dipole moments are random in the x, y, and z directions).
  • the x and y directions are directions parallel to the substrate surface
  • the z direction is a direction perpendicular to the substrate surface.
  • the graph of the calculation result of the light extraction efficiency shown below is the calculation result for this random dipole.
  • FIG. 25 shows the result of calculating the dependence of the period in which the opening is arranged on the light extraction efficiency by computer simulation using the FDTD method in order to confirm the effect of the organic EL element of the present invention.
  • the light extraction efficiency obtained by the simulation is the light extraction efficiency when the light is extracted up to the substrate (the relative value of the light intensity extracted up to the substrate with respect to the total emission intensity) (the same applies to the following simulation results).
  • ⁇ on the horizontal axis represents the wavelength of the emitted light
  • ⁇ on the vertical axis represents the light extraction efficiency.
  • FIG. 26 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 first refractive index material layer 8a is made of zinc oxide and has a refractive index of 2.00.
  • the refractive index material region 8b is made of SOG, and its refractive index is 1.25.
  • zinc oxide corresponds to a high refractive index material and SOG corresponds to a low refractive index material.
  • the refractive index is 1.82 + 0.009i at 550 nm, and other wavelengths are extrapolated by the Lorentz model.
  • the average refractive index of the organic layer 3 was 1.72.
  • the cathode (second electrode) 4 is made of amorphous ITO (a-ITO), the refractive index is 2.08 + 0.013i at 550 nm, and the other wavelengths are extrapolated by the Lorentz model.
  • the low refractive index layer 5 is made of SOG and has a refractive index of 1.25.
  • 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, the metal layer 6, and the refractive index modulation structure 8 were 150 nm, 100 nm, 50 nm, 50 nm, 100 nm, and 200 nm, respectively.
  • the period (pitch) p between the second refractive index material regions 8b was 200 nm, 300 nm, 500 nm, 900 nm, 2000 nm, 4000 nm, and 8000 nm.
  • the size s of the second refractive index material region 8b (or the size s of the hole 8h) was set to 1 ⁇ 2 of the period p.
  • the computer simulation calculation was performed assuming that light emission (star mark in FIG. 26) was emitted at a position of 52.5 nm from the cathode 4 on the central axis of the first refractive index material layer 8a made of a high refractive index material.
  • a structure having a cathode-side structure with an Otto-type arrangement does not have a first electrode-side structure that extracts propagating light extracted into the organic layer without using it as guided mode light (hereinafter, “ Otto-type arrangement only ”) and no second electrode-side structure of Otto-type arrangement, and no first electrode-side structure for extracting propagating light out of the waveguide mode light.
  • Otto-type arrangement only a structure having a cathode-side structure with an Otto-type arrangement, but does not have a first electrode-side structure that extracts propagating light extracted into the organic layer without using it as guided mode light
  • standard structure hereinafter sometimes referred to as “standard structure”.
  • the standard structure means a structure formed on a substrate in the order of an anode layer, an organic layer, and a cathode metal layer.
  • the standard structure was such that the substrate was made of glass, the anode was made of ITO, the organic layer was sandwiched, and the cathode was made of Al.
  • Refractive indexes of 1.52, 1.82 + 0.009i, 1.72, and 0.649 + 4.32i were used, respectively, and the anode, organic layer, and cathode layer thicknesses were 150 nm, 100 nm, and 100 nm, respectively. did.
  • the light extraction efficiency was lower than that of the cathode side structure having only the Otto type arrangement at almost all wavelengths of 450 nm to 750 nm. This is because the total area of the interface between the first refractive material layer and the second refractive material region perpendicular to the substrate surface decreases as the period p increases, and the propagating light in the organic layer decreases with respect to the substrate surface. This is because it is difficult to be refracted in a direction close to vertical.
  • the period p is preferably 200 nm to 2000 nm, more preferably 300 nm to 900 nm, and even more preferably 500 nm to 900 nm under the above conditions.
  • FIG. 27 shows that when the second refractive index material region is periodically arranged in one direction in the organic EL element of the first embodiment, the period p of the second refractive index material region is (a) 200 nm, and (b) 300 nm. , (C) 500 nm, (d) 900 nm, (e) 2000 nm, and (f) 4000 nm, showing the results obtained by computer simulation of the intensity distribution of the electric field of the emitted light from the horizontal dipole It is.
  • the wavelength of the emitted light was 620 nm.
  • the intensity distribution is shown with the substrate on the top and the metal layer on the bottom.
  • the computer simulation of FIG. 27 is also a result of the model structure obtained by performing the computer simulation of FIG.
  • the period p of the second refractive index material region is (a) 200 nm, (b) 300 nm, (c) 500 nm, (d) 900 nm, (e) 2000 nm, and (f) in the same case as FIG.
  • the result obtained by computer simulation about the intensity distribution of the magnetic field of the radiated light from the vertical dipole in each case of 4000 nm is shown.
  • the wavelength of the emitted light was 620 nm.
  • the intensity distribution is shown with the substrate on the top and the metal layer on the bottom.
  • the computer simulation of FIG. 28 is also a result of the model structure obtained by performing the computer simulation of FIG.

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Abstract

La présente invention concerne un élément (10) électroluminescent organique équipé, dans l'ordre indiqué, d'une anode (première électrode) (2), d'une couche organique (3) comprenant une couche électroluminescente, et d'une cathode (seconde électrode) (4), et dans lequel : la surface de la cathode (4) sur le côté faisant face à la couche organique (3) est équipée, dans l'ordre indiqué, d'une couche à faible indice de réfraction (5) présentant une épaisseur située dans la plage allant de 20 à 300 nm, et d'une couche métallique (6) ; la cathode (4) comprend un matériau électroconducteur translucide ; l'indice de réfraction de la couche à faible indice de réfraction (5) est inférieur à l'indice de réfraction de la couche organique (3) ; et la surface de l'anode (2) sur le côté faisant face à la couche organique (3) est pourvue d'une structure (8) à modulation d'indice de réfraction qui comporte une couche de matériau (8a) à premier indice de réfraction, et comporte une pluralité de régions de matériau (8b) à second indice de réfraction disposées de manière séparée dans la direction dans le plan dans la couche de matériau (8a) à premier indice de réfraction.
PCT/JP2014/069820 2013-07-31 2014-07-28 Élément électroluminescent organique, dispositif d'affichage d'image, et dispositif d'éclairage Ceased WO2015016176A1 (fr)

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JP2013159700 2013-07-31

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CN113555515A (zh) * 2021-07-16 2021-10-26 京东方科技集团股份有限公司 发光器件及显示面板

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US9890332B2 (en) 2015-03-08 2018-02-13 Proton Power, Inc. Biochar products and production
US10689581B2 (en) 2015-03-08 2020-06-23 Proton Power, Inc. Biochar products and production
CN113555515A (zh) * 2021-07-16 2021-10-26 京东方科技集团股份有限公司 发光器件及显示面板

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