JP2021106072A - Transparent conductor, manufacturing method of the same, and organic device - Google Patents

Abstract

To provide a transparent conductor capable of sufficiently increasing the efficiency of light extraction from a light-emitting layer.SOLUTION: A transparent conductor 10 for organic devices having a light-emitting layer, includes a transparent base material 11, a first metal oxide layer 12, a metal layer 18 containing silver or a silver alloy, and a second metal oxide layer 14, in this order. When a wavelength of light from the light-emitting layer is denoted as λ[nm], a refractive index of the second metal oxide layer 14 at λ is denoted as n, and a thickness of the second metal oxide layer 14 is denoted as d[nm], the transparent conductor 10 satisfying the following formula (1) or (2). 0<n×d/λ≤0.0008×λ-0.3393...(1), 0.0012×λ-0.3302≤n×d/λ≤0.0015×λ-0.1975...(2). [In equations (1) and (2), d is greater than 0 and less than or equal to 210 nm].SELECTED DRAWING: Figure 1

Description

The present disclosure relates to transparent conductors, methods for producing the same, and organic devices.

The transparent conductor is used as a display such as a liquid crystal display (LCD), a plasma display panel (PDP), and an electroluminescence panel (organic EL, inorganic EL), and as a transparent electrode such as a solar cell. The transparent conductor is required to have a high light transmittance in some applications, for example, so as not to interfere with the absorption and emission of light (for example, Patent Document 1).

On the other hand, organic EL is a technique utilizing the electroluminescence phenomenon of an organic material, and attempts are being made to improve the light extraction efficiency. For example, in Patent Document 2, it is studied to increase the intensity of emitted light by optimizing the optical path length of the light emitted from the light emitting layer of the organic light emitting element to the substrate side and reflected by the reflective film. The transparent conductor of such a light-emitting element, ITO was added tin (Sn) to indium oxide _(In 2 _{O 3),} or, IZO is added zinc (Zn) to indium oxide _(In 2 _{O 3)} It is used.

International Publication No. 2012/002113 JP-A-2002-25287

The transparent conductor is required to have flexibility in each application. In the case of the conventional ITO film, it is difficult to improve the flexibility because it is necessary to increase the thickness in order to secure the conductivity. Therefore, as a transparent conductor having both excellent conductivity and flexibility, a transparent conductor having a three-layer structure in which a metal layer is laminated between a pair of metal oxide layers is considered as a promising material.

However, according to the study by the present inventors, such a transparent conductor emits light even if the transmittance of the transparent conductor itself is maximized when the organic device is constructed by laminating it on the light emitting layer. It was found that there is a phenomenon that the efficiency of extracting light from the layer is low. Therefore, it is an object of the present disclosure to provide a transparent conductor capable of sufficiently increasing the efficiency of extracting light from the light emitting layer and a method for producing the transparent conductor in one aspect. It is an object of the present disclosure to provide an organic device including the transparent conductor in yet another aspect.

The present invention is, on one side, a transparent conductor for organic devices having a light emitting layer, a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal. The oxide layers are provided in this order, the wavelength of the light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm. ], A transparent conductor satisfying the following formula (1) or (2) is provided.
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
In the formulas (1) and (2), d is more than 0 and 210 nm or less. When the light from the light emitting layer of the organic device contains a plurality of wavelengths, the above formula (1) or the formula (2) may be satisfied at at least one wavelength among the plurality of wavelengths.

The second metal oxide layer of the transparent conductor satisfies the above formula (1) or the above formula (2). By satisfying the above formula (1) or (2) in this way, the efficiency of extracting light emitted from the organic layer can be increased. It is presumed that this is due to the fact that the phase difference between the light directly taken out from the light emitting layer and the light reflected at the boundary of each layer is aligned. The second metal oxide layer may be composed of a plurality of metal oxide films, in which case the total thickness of the plurality of metal oxide layers (that is, the thickness d of the second metal oxide film) is the above formula. (1) or the formula (2) may be satisfied.

The second metal oxide layer forming the surface opposite to the transparent base material may contain indium oxide as a main component. As a result, the hole injection efficiency can be increased and the luminous efficiency can be increased. When the second metal oxide layer is composed of a plurality of metal oxide films, the metal oxide film forming the outermost surface and in contact with the organic layer may contain indium oxide as a main component.

The work function of the second metal oxide layer on the outermost surface, which forms the surface opposite to the transparent substrate and is in contact with the organic layer, may be 4.7 eV or more. Thereby, the internal quantum efficiency of the organic layer can be increased.

In another aspect, the present disclosure comprises a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer in that order, a transparent conductor for an organic device. The method for producing the second metal oxide layer, based on the wavelength λ [nm] of the light emitted from the light emitting layer of the organic device, so as to satisfy the following formula (1) or formula (2). Provided is a method for producing a transparent conductor, which adjusts at least one of the refractive index n of the second metal oxide layer at a thickness d [nm] and λ.
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
In the formulas (1) and (2), d is more than 0 and 210 nm or less. When the light from the light emitting layer of the organic device contains a plurality of wavelengths, the above formula (1) or the formula (2) may be satisfied at at least one wavelength among the plurality of wavelengths.

In the method for producing a transparent conductor, the second metal oxide layer satisfies the above formula (1) or the above formula (2). By arranging the second metal oxide layer satisfying the above formula (1) or (2) on the light emitting layer side in this way, the efficiency of extracting light emitted from the organic layer can be increased.

In yet another aspect, the present disclosure is an organic device comprising a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, a second metal oxide layer, and a light emitting layer in this order. When the wavelength of the light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. Provided is an organic device satisfying the following formula (1) or formula (2).
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
In the formulas (1) and (2), d is more than 0 and 210 nm or less. When the light from the light emitting layer of the organic device contains a plurality of wavelengths, the above formula (1) or the formula (2) may be satisfied at at least one wavelength among the plurality of wavelengths.

The second metal oxide layer of the transparent conductor of the organic device satisfies the above formula (1) or the above formula (2). By satisfying the above formula (1) or (2) in this way, the efficiency of extracting light emitted from the organic layer can be increased. It is presumed that this is due to the fact that the phase difference between the light directly taken out from the light emitting layer and the light reflected at the boundary of each layer is aligned.

In one aspect, it is possible to provide a transparent conductor capable of sufficiently increasing the efficiency of extracting light from the light emitting layer and a method for producing the transparent conductor. In another aspect, an organic device comprising the transparent conductor can be provided.

FIG. 1 is a cross-sectional view schematically showing an embodiment of a transparent conductor. FIG. 2 is a diagram schematically showing an embodiment of an organic device. FIG. 3 is a diagram schematically showing a propagation path of light from the light emitting layer. FIG. 4 is a diagram showing an example of a simulation result of the organic device of FIG. FIG. 5 is a graph showing the relationship between the wavelength λ of the light used in the simulation and n × d / λ. FIG. 6 is a graph showing the relationship between the current value applied to the organic EL device and the luminous efficiency (EQE). FIG. 7 is a graph showing the simulation results of Experimental Example 1. FIG. 8 is a graph showing the simulation results of Experimental Example 1. FIG. 9 is a graph showing the simulation results of Experimental Example 2.

Hereinafter, embodiments of the present invention will be described below with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present invention, and the present invention is not intended to be limited to the following contents. In the description, the same reference numerals are used for elements having the same structure or the same function, and duplicate description may be omitted in some cases. In addition, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a transparent conductor. The transparent conductor 10 has a laminated structure in which the transparent base material 11, the first metal oxide layer 12, the metal layer 18, and the second metal oxide layer 14 are arranged in this order.

As used herein, "transparent" means that visible light is transmitted, and light may be scattered to some extent. Regarding the degree of light scattering, the required level differs depending on the use of the transparent conductor 10. Those with light scattering, which is generally referred to as translucent, are also included in the concept of "transparency" herein.

The transparent base material 11 is not particularly limited, and may be a flexible transparent resin base material. As the transparent resin base material, for example, the organic resin film may be an organic resin sheet. Examples of the transparent base material 11 include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin films such as polyethylene and polypropylene, polycarbonate films, acrylic films, norbornene films, polyarylate films, and polyether sulfone. Examples include films, diacetylcellulose films, polymides, and triacetylcellulose films. Of these, polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferable. The above-mentioned one type may be used alone, or two or more types may be combined.

The thickness of the transparent base material 11 is, for example, 200 μm or less from the viewpoint of further increasing the flexibility of the transparent conductor 10. The refractive index of the transparent substrate is, for example, 1.50 to 1.70 from the viewpoint of making the transparent conductor 10 having excellent optical characteristics. The refractive index in the present specification is a value measured under the conditions of λ = 633 nm and a temperature of 20 ° C. The transparent base material 11 may be subjected to at least one surface treatment selected from the group consisting of corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, and ozone treatment. ..

The transparent base material 11 is not limited to the transparent resin base material, and may be, for example, a molded product of an inorganic compound such as soda lime glass, non-alkali glass, and quartz glass. On the other hand, when the transparent base material 11 is a transparent resin base material, the transparent conductor 10 can be made excellent in flexibility. As a result, the transparent conductor 10 can be suitably used as a transparent conductor for flexible organic devices.

The first metal oxide layer 12 is a transparent layer containing a metal oxide. The first metal oxide layer 12 has a function of protecting the metal layer 18. The first metal oxide layer 12 may be composed of a metal oxide different from ITO (indium tin oxide). When the first metal oxide layer 12 does not contain ITO, corrosion of the silver alloy contained in the metal layer 18 can be suppressed.

From the viewpoint of achieving both transparency and corrosion resistance at a higher level, the first metal oxide layer 12 contains, for example, four components of zinc oxide, tin oxide, indium oxide and titanium oxide, or zinc oxide, indium oxide and oxidation. The three components of titanium may be contained as the main component. By containing the above four components, the first metal oxide layer 12 can have sufficiently high conductivity and transparency.

The zinc oxide contained in the first metal oxide layer 12 is, for example, ZnO, and the indium oxide is, for example, In ₂ O ₃ . Titanium oxide is, for example, TiO ₂ . Tin oxide is, for example, SnO ₂ . The ratio of the metal atom to the oxygen atom in each of the above metal oxides may deviate from the stoichiometric ratio. It may also contain other oxides having different oxidation numbers. The first metal oxide layer 12 may contain tin oxide, but the content of _{tin oxide (SnO 2} ) is small from the viewpoint of reducing the corrosion of silver or the silver alloy contained in the metal layer 18. Also, it does not have to contain tin oxide.

When the first metal oxide layer 12 contains the above three components as main components, the total content of the three components is 90% by mass or more in terms of _{ZnO, In 2} O ₃ and TiO _{2, respectively.} It is preferably 95% by mass or more, and more preferably 95% by mass or more.

The thickness of the first metal oxide layer 12 is, for example, 60 nm or less from the viewpoint of improving flexibility. On the other hand, from the viewpoint of further improving corrosion resistance and improving productivity, the thickness is, for example, 5 nm or more.

In the first metal oxide layer 12, when the three components of zinc oxide, indium oxide and titanium oxide _{are converted into ZnO, In 2} O ₃ and TiO ₂ , respectively, the content of ZnO with respect to the total of the above three components is It may be 20 to 85 mol%, or 30 to 80 mol%. _{When converted in the same manner, the content of In 2} O ₃ with respect to the total of the above three components may be 10 to 35 mol% or 10 to 25 mol% from the viewpoint of achieving both high conductivity and high corrosion resistance. You may.

_{When converted in the same manner, the content of TiO 2} with respect to the total of the above three components is preferably 5 to 15 mol%, preferably 7 to 13 mol%, from the viewpoint of achieving both transparency and excellent corrosion resistance. More preferred.

When the first metal oxide layer 12 contains the above four components as main components, the first metal oxide layer 12 contains four components of zinc oxide, indium oxide, titanium oxide and tin oxide, respectively, in ZnO and In. when converted into ₂ O _3, TiO ₂ and SnO _2, zinc oxide content to the total of the 4 components, from the viewpoint of achieving both excellent corrosion resistance and high conductivity, may be 20～68Mol% ..

When converted in the same manner, the content of indium oxide with respect to the total of the above four components is 15 to 35 mol% from the viewpoint of improving corrosion resistance while sufficiently lowering the surface resistance. When converted in the same manner, the content of titanium oxide with respect to the total of the above four components is 5 to 20 mol% from the viewpoint of ensuring the transmittance of visible light and increasing the alkali resistance. When converted in the same manner, the content of tin oxide with respect to the total of the above four components is, for example, 5 to 40 mol% from the viewpoint of achieving both high transparency and excellent corrosion resistance.

The first metal oxide layer 12 may be composed of a plurality of metal oxide films having different compositions, and a part of the plurality of metal oxide films is a metal nitride film or a metal oxynitride film. There may be. In that case, the film in contact with the transparent base material 11 may be a metal oxide film, a metal nitride film or a metal oxynitride film containing the above four components or other components, and the film in contact with the metal layer 18 may be a film. It may be a metal oxide film containing the above three components. The metal oxide film in contact with the transparent base material 11 may contain, for example, silicon oxide. The metal nitride film in contact with the transparent base material 11 may contain silicon nitride. The metal oxynitride film in contact with the transparent substrate 11 may contain silicon (Si—ON) nitrogen oxide. In the present disclosure, silicon corresponds to a metal element, and silicon oxide and silicon nitride correspond to a metal oxide and a metal nitride, respectively.

The first metal oxide layer 12 may have low conductivity or may be an insulator. In this case, the conductivity of the transparent conductor 10 may be borne by the metal layer 18 and the second metal oxide layer 14. The first metal oxide layer 12 can be produced by a vacuum film forming method such as a vacuum vapor deposition method, a sputtering method, an ion plating method, or a CVD method. Of these, the sputtering method is preferable in that the film forming chamber can be miniaturized and the film forming speed is high. Examples of the sputtering method include DC magnetron sputtering. As the target, a metal target or a metal oxide target can be used. The first metal oxide layer 12 may be a layer that does not dissolve in the acidic etching solution.

The metal layer 18 may contain silver or a silver alloy as a main component. The metal layer 18 may be a layer that dissolves in an acidic etching solution. Thereby, patterning can be easily performed. Since the metal layer 18 has high transparency and excellent conductivity, the surface resistance can be sufficiently lowered while ensuring the transmittance of the transparent conductor 10. The metal layer 18 may contain a metal element other than silver. For example, the environmental resistance of the metal layer 18 is improved by containing at least one element selected from the group consisting of Cu, Nd, Pt, Pd, Bi, Sn and Sb as a constituent element of the silver alloy or a simple metal. be able to. Examples of silver alloys include Ag-Pd, Ag-Cu, Ag-Pd-Cu, Ag-Nd-Cu, Ag-In-Sn, and Ag-Sn-Sb. The silver alloy preferably contains Ag as a main component and each of the above-mentioned metals as a sub component. The metal layer 18 may be a layer made of only metal.

The content of the metal other than Ag in the silver alloy is, for example, 0.5 to 5% by mass from the viewpoint of further improving the corrosion resistance and transparency. The silver alloy preferably contains Pd as a metal other than Ag. Thereby, the corrosion resistance in a high temperature and high humidity environment can be further improved.

The thickness of the metal layer 18 may be, for example, 5 to 25 nm. If the thickness of the metal layer 18 becomes too small, the continuity of the metal layer 18 is impaired and the surface resistance value of the transparent conductor 10 tends to increase. On the other hand, if the thickness of the metal layer 18 becomes too large, excellent transparency tends to be impaired.

The metal layer 18 has a function of adjusting the conductivity and surface resistance of the transparent conductor 10. The metal layer 18 can be produced by a vacuum deposition method such as a vacuum deposition method, a sputtering method, an ion plating method, or a CVD method. Of these, the sputtering method is preferable in that the film forming chamber can be miniaturized and the film forming speed is high. Examples of the sputtering method include DC magnetron sputtering. As the target, a metal target can be used.

The second metal oxide layer 14 is a transparent layer containing a metal oxide. The second metal oxide layer 14 in contact with the organic layer has a function of facilitating the movement of holes when arranged on the organic layer side of the organic device, for example. The second metal oxide layer 14 in contact with the organic layer may be composed of a metal oxide containing ITO. The second metal oxide layer 14 may contain ITO as a main component, or may be composed of ITO and unavoidable impurities derived from impurities of the raw material. The content of ITO in the second metal oxide layer 14 is preferably 90% by mass or more, and more preferably 95% by mass or more.

The second metal oxide layer 14 may be composed of a plurality of metal oxide films having different compositions. When the second metal oxide layer 14 is composed of a plurality of metal oxide films having different compositions, the film in contact with the metal layer 18 is a metal oxide film containing a metal oxide different from ITO as a main component. The film in contact with the organic layer may be a metal oxide film containing ITO as a main component.

ITO is an oxide of indium and tin. The oxide is a composite oxide having In, Sn and O (oxygen) as constituent elements. Further, the second metal oxide layer 14 may contain another composite oxide.

The work function of the surface 14a of the second metal oxide layer 14 opposite to the metal layer 18 side may be 4.7 eV or more, or 5.0 eV or more. When an organic layer is provided on the surface 14a of the second metal oxide layer 14 having such a high work function to fabricate an organic device, holes are injected into the organic layer or holes from the organic layer are collected. Acceptance can be done smoothly enough. Therefore, the performance of the organic device can be improved. The work function of the surface 14a of the second metal oxide layer 14 can be measured using a commercially available measuring device.

The work function of the surface 14a of the second metal oxide layer 14 tends to depend on the composition in the vicinity of the surface 14a. For example, when forming a second metal oxide layer 14 containing ITO or a metal oxide film in contact with an organic layer, the SnO ₂ content of the target composition or In depending on the film forming conditions at the time of sputtering. The work function of the surface 14a of the second metal oxide layer 14 can be adjusted by changing the Sn and O contents.

The thickness d of the second metal oxide layer 14 may be, for example, 2 nm or more, or 5 nm or more, from the viewpoint of stably increasing the work function on the surface 14a. On the other hand, the thickness d of the second metal oxide layer 14 is, for example, 100 nm or less from the viewpoint of sufficiently increasing the transparency and flexibility of the transparent conductor 10.

The thickness of each layer constituting the transparent conductor 10 can be measured by the following procedure. The transparent conductor 10 is cut by a focused ion beam device (FIB, Focused Ion Beam) to obtain a cross section. The cross section is observed using a transmission electron microscope (TEM), and the thickness of each layer is measured. It is preferable that the measurement is performed at 10 or more positions arbitrarily selected and the average value is obtained. As a method for obtaining a cross section, a microtome may be used as a device other than the focused ion beam device. A scanning electron microscope (SEM) may be used as a method for measuring the thickness. It is also possible to measure the film thickness using a fluorescent X-ray apparatus.

The thickness of the transparent conductor 10 may be 250 μm or less, or 200 μm or less. With such a thickness, the required levels of transparency and flexibility can be sufficiently satisfied.

The compositions of the first metal oxide layer 12 and the second metal oxide layer 14 may be different from each other. By making the composition of the first metal oxide layer 12 different from the composition of the second metal oxide layer 14, only the second metal oxide layer 14 and the metal layer 18 are acid-etched in one step. The first metal oxide layer 12 can be left by removing it by etching with a liquid.

The transparent conductor 10 having the above configuration is also excellent in alkali resistance. Therefore, patterning can be performed efficiently. The transparent conductor 10 can be suitably used for an organic EL display, an organic device such as an organic EL lighting, and the like.

The transparent conductor 10 of FIG. 1 may have an arbitrary layer between the layers. For example, a hard coat layer may be provided between the transparent base material 11 and the first metal oxide layer 12, or an etching resistant layer may be provided between the metal layer 18 and the first metal oxide layer 12. You may. Further, a water vapor barrier layer may be provided between the transparent base material 11 and the first metal oxide layer 12. The hard coat layers may be provided in pairs so as to sandwich the transparent base material 11.

Since the transparent conductor 10 is excellent in conductivity, flexibility, and corrosion resistance, it is suitably used as an electrode for an organic device such as an organic EL display and an organic EL lighting. In this case, the first metal oxide layer 12, the metal layer 18, and the second metal oxide layer 14 function as the transparent electrode 20. The transparent electrode 20 may be an anode or a cathode.

FIG. 2 is a diagram schematically showing an embodiment of an organic device. The organic device 100 is, for example, an organic EL illumination, and the transparent base material 11, the transparent electrode (anode) 20, the hole injection layer 30, the hole transport layer 32, the light emitting layer 40, the electron transport layer 50, the electron injection layer 52, and the like. And a laminate 150 having a metal electrode (cathode) 60 in this order. A transparent conductor 10 can be used as the transparent base material 11 and the transparent electrode 20 in the organic device 100.

The transparent conductor 10 is provided so that the surface of the second metal oxide layer 14 (surface 14a in FIG. 1) of the transparent electrode 20 is in contact with the hole injection layer 30. A power supply 80 is connected to the transparent electrode 20 that functions as an anode and the metal electrode 60 that functions as a cathode. By applying an electric field from the power source 80, holes are injected from the transparent electrode 20 into the hole injection layer 30, and electrons are injected from the metal electrode 60 into the electron injection layer 52.

The holes injected into the hole injection layer 30 and the electrons injected into the electron injection layer 52 move through the hole transport layer 32 and the electron transport layer 50, respectively, and recombine in the light emitting layer 40. By this recombination, the organic compound in the light emitting layer 40 emits light. The light generated by this light emission passes through the hole transport layer 32, the hole injection layer 30, the transparent electrode 20, and the transparent base material 11, and is emitted from the side surface 20a of the organic device 100. The metal electrode 60 functions as a reflective electrode.

The organic device 100 uses a transparent conductor 10 as the transparent base material 11 and the transparent electrode 20. Therefore, by increasing the work function of the surface 14a of the second metal oxide layer 14 of the transparent electrode 20, holes can be efficiently injected into the hole injection layer 30. As a result, the amount of light emitted from the light emitting layer 40 of the organic device 100 can be increased with respect to the voltage applied from the power source 80 (current flowing between both electrodes). Further, by optimizing the thickness d of the second metal oxide layer 14 according to the emission wavelength, the light emitted by the light emitting layer 40 can be efficiently extracted from the side surface 20a, and the luminous efficiency is sufficiently high. can do. This makes it possible to increase the luminous efficiency, which indicates how much light can be extracted with respect to the voltage (current) applied from the power supply 80.

The hole injection layer 30, the hole transport layer 32, the light emitting layer 40, the electron transport layer 50, the electron injection layer 52, and the metal electrode (cathode) 60 can be formed by using ordinary materials.

The hole injection layer 30 has a function of facilitating the injection of holes from the transparent electrode 20 and transporting the injected holes and injecting them into the hole transport layer 32. The hole transport layer 32 has a function of injecting the holes injected from the hole injection layer 30 into the light emitting layer 40. For example, examples of the material of the hole injection layer 30 and the hole transport layer 32 include an aromatic amine compound and an anthracene derivative.

The light emitting layer 40 has a function of transporting injected holes and electrons and a function of generating excitons by recombination of holes and electrons. Examples of the light emitting layer 40 include a two-component system in which a host material and a dopant material are combined. Host materials include aromatic hydrocarbon compounds such as 1,10-phenanthroline derivatives, organic metal complex compounds, naphthalene, anthracene, naphthalene, perylene, benzofluorantene, naphthofluoranthene and their derivatives, as well as styrylamine and Examples thereof include tetraaryldiamine derivatives. Examples of the dopant material include a benzodifluorentene derivative and a coumarin derivative.

The electron transport layer 50 has a function of transporting the electrons injected from the electron injection layer 52 to the light emitting layer 40. The electron injection layer 52 has a function of facilitating the injection of electrons from the metal electrode 60 and a function of enhancing the adhesion with the metal electrode 60. The electron transport layer 50 and the electron injection layer may be formed by using an organic material such as trinitrofluorenone, oxadiazole or a compound having a triazole structure, or an alkali metal such as lithium, lithium fluoride, etc. Alternatively, it may be formed using an inorganic material such as lithium oxide.

As the metal electrode 60, one composed of a metal material such as aluminum, an organometallic complex or a metal compound can be used. Each layer can be formed by a usual method such as a vacuum vapor deposition method, an ionization vapor deposition method, and a coating method. The thickness of each layer of the laminate 150 constituting the organic device 100 can be, for example, 1/8 to 1/4 of the wavelength of light obtained by the light emitting layer 40.

FIG. 3 is a diagram schematically showing a propagation path of light from the light emitting layer 40. In the light emitting layer 40, excitons are generated to emit light. As shown in FIG. 3, for example, a part of the emitted light is totally reflected at the interface between the hole injection layer 30 and the transparent electrode 20 and the interface between the transparent electrode 20 and the transparent base material 11. Then, another part of the emitted light is taken out from the side surface 20a. Assuming that the ratio (%) of the light emitted from the side surface 20a to the light emitted by the light emitting layer 40 is the light extraction efficiency, the luminous efficiency (external quantum efficiency) of the organic device 100 is calculated by the following formula (I). be able to. From the formula (I), in order to improve the luminous efficiency of the organic device 100, it is effective to increase the light extraction efficiency.
Luminous efficiency = internal quantum efficiency x light extraction efficiency (I)

The internal quantum efficiency in the present specification indicates the ratio (light energy generated in the light emitting layer 40) in which the energy excited in the light emitting layer 40 by the injected electric power is converted into light energy.

The light extraction efficiency can be increased by suppressing total reflection at the interface of each layer. Here, the reflectance and transmittance of the laminated body 150 can be optically simulated by using the optical constant (n / k) and the thickness of each layer. k is the extinction coefficient. Examples of such simulation software include software for organic light emitting diodes manufactured by Sim4Tech (trade name: SimOLED).

FIG. 4 shows a transparent base material 11, a first metal oxide layer 12, a metal layer 18, a second metal oxide layer 14, a hole injection layer 30, a hole transport layer 32, a light emitting layer 40, and a metal electrode 60. It is a figure which shows an example of the simulation result of the organic device composed of the laminated body which has in this order. In this simulation, the multiple interference effect inside the light emitting layer 40 and the optical characteristics of each layer other than the light emitting layer 40 are used as a function of the wavelength and the light propagation angle of the light generated in the light emitting layer 40, so that the light is extracted from the organic device. It is a simulation of efficiency. The preconditions for the simulation are as shown in Table 1.

FIG. 4 shows the results of simulating the relationship between the thickness d (nm) of the second metal oxide layer 14 and the light extraction efficiency at each wavelength under the above-mentioned preconditions. Based on this simulation result, the range of the thickness d of the second metal oxide layer 14 at which the light extraction efficiency of light of each wavelength is 15% can be obtained. In the simulation shown in FIG. 4, in the range of the thickness d of 0 to 210 nm, the range in which the light extraction efficiency of light is 15% or more at each wavelength is generally as follows.

When λ = 450 nm, d = 45 to 95 nm, d = 160 to 210 nm
When λ = 520 nm, d = 30 nm or less, d = 70 to 170 nm
When λ = 610 nm, d = 40 nm or less, d = 120 to 210 nm

From the above results, the range of the thickness d at which the light extraction efficiency is 15% or more is extracted in order from the smallest d (first range, second range, ..., Nth range). Then, the optical path length (n × d / λ) at the upper and lower limits of d in each range is calculated. Assuming that the refractive index n of the second metal oxide layer 14 at the wavelength λ at each upper and lower limit values is as shown in Table 2, the optical path lengths of the upper and lower limit values of d in each range are calculated as shown in Table 2. In the light extraction efficiency curve as shown in FIG. 4, when the light extraction efficiency is 15% or less when d = 0 nm, the optical path length in the first range is set to 0, and the light is emitted from the second range. The range of the thickness d at which the extraction efficiency is 15% or more is sequentially extracted.

FIG. 5 is a graph showing the relationship between the wavelength λ of the light used in the simulation and the lower limit value and the upper limit value in each range of the optical path length shown in Table 2. FIG. 5 shows the first-order regression line and the first-order regression equation of the upper limit value and the lower limit value of each range in which the wavelength λ [nm] is x and n × d [nm] / λ [nm] is y. There is.

In the region between the horizontal axis (x-axis) and the dotted line and the region between the solid line and the alternate long and short dash line shown in FIG. 5, the light extraction efficiency can be increased (for example, 15% or more). This region is represented by the following equations (1) and (2), respectively.
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)

In the formulas (1) and (2), d is more than 0 and 210 nm or less. N at the wavelength λ is, for example, 1.8 to 2.2. When the light from the light emitting layer 40 of the organic device contains a plurality of wavelengths, the above formula (1) or the formula (2) may be satisfied at at least one wavelength among the plurality of wavelengths. The wavelength of light from the light emitting layer 40 of the organic device may be, for example, 400 to 700 nm.

By adjusting at least one of the composition and the thickness d of the second metal oxide layer 14 so as to satisfy the above formula (1), the ratio of light extracted from the side surface 20a, that is, the light extraction efficiency is sufficiently increased. be able to. This is because the phase difference between the light directly taken out from the light emitting layer 40 and the light reflected at the boundary of each layer is aligned, and the total reflection at the interface between the transparent base material 11 and the transparent electrode 20 is reduced. It is presumed that this is due to.

The optical path length (n × d / λ) preferably satisfies the formula (1-1) or the formula (2-1) from the viewpoint of further increasing the light extraction efficiency, and the formula (1-2) or the formula (2). It is more preferable to satisfy -2). N, d, and λ in each of the following equations are synonymous with equations (1) and (2).
0 <n × d / λ ≦ 0.0006 × λ −0.2605 ... (1-1)
0.0011 × λ-0.1910 ≦ n × d / λ ≦ 0.0014 × λ-0.1914 ... (2-1)
0 <n × d / λ ≦ 0.0004 × λ-0.1817 ... (1-2)
0.0012 × λ −0.2304 ≦ n × d / λ ≦ 0.0015 × λ −0.24595 ・ ・ ・ (2-2)

The method for producing the transparent conductor 10 according to one embodiment is based on the wavelength λ [nm] of the light emitted from the light emitting layer 40, and is a second method so as to satisfy the above formula (1) or formula (2). At least one of the thickness d [nm] and the refractive index n of the metal oxide layer 14 is adjusted. This makes it possible to manufacture the transparent conductor 10 having high light extraction efficiency.

FIG. 6 is a graph showing the relationship between the current value applied to the organic EL device using Alq3 [Tris (8-quinolinolato) aluminum] that emits green light in the light emitting layer 40 and the luminous efficiency (EQE). The plots of the black circles, white squares, and black triangles of FIG. 6 show the organic device 100 shown in FIG. 2 when the thickness d of the second metal oxide layer 14 is 10 nm, 100 nm, and 40 nm, respectively. It shows the change in the luminous efficiency of. Of these, the black triangle is a conventional transparent conductor whose optical path length does not satisfy the equations (1) and (2) under the condition that the transmittance of the transparent conductor 10 is maximized. As shown in FIG. 6, the luminous efficiency can be increased by having the second metal oxide layer 14 having a thickness d satisfying the formula (1) or the formula (2). Further, the luminous efficiency can be adjusted by changing the thickness d of the second metal oxide layer 14.

Although some embodiments have been described above, the present invention is not limited to the above-described embodiments. The organic device may be an organic EL illumination, an organic EL display, or the like, and the structure thereof is not limited to the structure shown in FIG.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Experimental Example 1]
(Manufacturing of transparent conductor)
A transparent conductor having a laminated structure as shown in FIG. 1 was produced. The transparent conductor had a laminated structure in which a transparent base material, a first metal oxide layer, a metal layer, and a second metal oxide layer were laminated in this order. This transparent conductor was produced in the following manner.

A commercially available glass substrate (manufactured by Corning, trade name: EAGLE XG, thickness: 0.7 mm) was prepared. This glass substrate was used as a transparent base material. A first metal oxide layer, a metal layer, and a second metal oxide layer were sequentially formed on the transparent substrate by DC magnetron sputtering.

Using a target composed of three components of zinc oxide, indium oxide, and titanium oxide, the first layer was placed on a transparent substrate by DC magnetron sputtering under reduced pressure (0.5 Pa) in a mixed gas atmosphere of argon gas and oxygen gas. 1 metal oxide layer (thickness: 40 nm) was formed. In the first metal oxide layer, when zinc oxide, indium oxide, and titanium oxide _{are converted into ZnO, In 2} O ₃ , and TiO ₂ , respectively, the content of ZnO is relative to the total of the above three components. Was 74 mol%, the content of _{In 2} O _{3 was 15 mol%, and the content of TiO 2} was 11 mol%. The refractive index of the first metal oxide layer at a wavelength of 450 nm was 2.1.

Using a target composed of a silver alloy of Ag, Pd and Cu, the silver alloy is mainly contained on the first metal oxide layer by DC magnetron sputtering under reduced pressure (0.5 Pa) in an argon gas atmosphere. A metal layer (thickness: 10 nm) contained therein was formed. The mass ratio of each metal of the silver alloy was Ag: Pd: Cu = 99.0: 0.7: 0.3.

A second metal oxide layer (thickness: 40 nm, thickness: 40 nm) was placed on the metal layer by DC magnetron sputtering under reduced pressure (0.5 Pa) in a mixed gas atmosphere of argon gas and oxygen gas using a target composed of ITO. ITO layer) was formed. The refractive index of the second metal oxide layer at a wavelength of 450 nm was 1.9.

(Evaluation of transparent conductor)
The total light transmittance (transmittance) of the produced transparent conductor was measured using a haze meter (trade name: NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.). The total light transmittance was 88%.

The surface resistance value of the produced transparent conductor was measured using a 4-terminal resistivity meter (trade name: Loresta GP, manufactured by Mitsubishi Chemical Corporation). The surface resistance value is 10Ω / sq. Met.

The work function on the surface of the second metal oxide layer of the produced transparent conductor was measured using a photoelectron spectrometer (manufactured by RIKEN Keiki Co., Ltd., trade name: FAC-1). The work function was 5.2 eV.

A simulation of the light extraction efficiency of the produced transparent conductor was performed using a green light emitting device having a wavelength of 520 nm. As a result, the light extraction efficiency was less than 15%.

When the emission wavelengths were 450 nm, 520 nm, and 610 nm, the light extraction efficiency when the thickness d of the second metal oxide layer was changed in the above-mentioned transparent conductor was simulated. The simulation results are as shown in FIG. As shown in FIG. 7, it was confirmed that the light extraction efficiency can be increased by adjusting the thickness d of the second metal oxide layer according to the wavelength.

When the emission wavelength is 450 nm, the light extraction efficiency is 15% or less when d = 0 nm, so that the second range is the minimum range of the thickness d at which the light extraction efficiency can be increased. Therefore, it is considered that the light extraction efficiency can be increased by setting the thickness d in a range satisfying the above equation (2) corresponding to the second range. Therefore, when λ = 450 nm, the range of the thickness d of the second metal oxide layer satisfying the above formula (2) was calculated. As a result, the range of d satisfying the formula (2) was about 50 nm ≦ d ≦ about 113 nm. According to FIG. 7, it was confirmed that the light extraction efficiency was about 12% or more in the range of the thickness d.

When the emission wavelength was 520 nm, the light extraction efficiency and transmittance when the thickness d of the second metal oxide layer was changed in the above-mentioned transparent conductor were simulated. The simulation results are as shown in FIG. In FIG. 8, the dotted line shows the transmittance, and the solid line shows the light extraction efficiency at 520 nm. As shown in FIG. 8, it was confirmed that the light extraction efficiency and the transmittance are not in a direct proportional relationship with each other, and even if the transmittance is increased, the light extraction efficiency cannot be increased. Further, it was confirmed that if the thickness d is set within a predetermined range, the light extraction efficiency can be increased to 15% or more even if the transmittance is 60% or less.

[Experimental Example 2 (Comparative Example)]
The light extraction efficiency when an ITO single layer was formed on the commercially available glass substrate used in Experimental Example 1 instead of the transparent conductor of Experimental Example 1 was determined by simulation in the same manner as in Experimental Example 1. The simulation results are as shown in FIG.

As shown in FIG. 9, it was confirmed that in the case of the ITO single layer, the light extraction efficiency hardly depends on the emission wavelength and the thickness of the ITO layer.

According to the present disclosure, there is provided a transparent conductor capable of sufficiently increasing the efficiency of extracting light from the light emitting layer and a method for producing the transparent conductor. Also provided is an organic device comprising a transparent conductor.

10 ... transparent conductor, 11 ... transparent base material, 12 ... first metal oxide layer, 14 ... second metal oxide layer, 14a ... surface, 18 ... metal layer, 20 ... transparent electrode, 20a ... side surface, 30 ... hole injection layer, 32 ... hole transport layer, 40 ... light emitting layer, 50 ... electron transport layer, 52 ... electron injection layer, 60 ... metal electrode, 80 ... power supply, 100 ... organic device, 150 ... laminate.

Claims (5)

A transparent conductor for organic devices having a light emitting layer.
A transparent base material, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer are provided in this order.
When the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. , A transparent conductor satisfying the following formula (1) or (2).
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
[In the formulas (1) and (2), d is more than 0 and 210 nm or less. ] The transparent conductor according to claim 1, wherein the second metal oxide layer forming a surface opposite to the transparent base material contains indium oxide as a main component. The transparent conductor according to claim 1 or 2, wherein the work function of the second metal oxide layer forming the surface opposite to the transparent base material is 4.7 eV or more. A method for producing a transparent conductor for an organic device, comprising a transparent base material, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer in this order.
Based on the wavelength λ [nm] of the light emitted from the light emitting layer of the organic device, the light emitting layer is closer to the light emitting layer than the first metal oxide layer so as to satisfy the following formula (1) or (2). A method for producing a transparent conductor, which adjusts at least one of the thickness d [nm] of the second metal oxide layer and the refractive index n of the second metal oxide layer at λ.
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
[In the formulas (1) and (2), d is more than 0 and 210 nm or less. ] An organic device including a transparent base material, a first metal oxide layer, a metal layer containing silver or a silver alloy, a second metal oxide layer, and a light emitting layer in this order.
When the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. , An organic device that satisfies the following formula (1) or (2).
0 <n × d / λ ≦ 0.0008 × λ −0.3393 ... (1)
0.0012 x λ-0.3302 ≤ n x d / λ ≤ 0.0015 x λ-0.1975 ... (2)
[In the formulas (1) and (2), d is more than 0 and 210 nm or less. ]

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