JPWO2015029203A1 - Organic light emitting device - Google Patents

Abstract

An organic light-emitting device capable of improving light extraction efficiency is provided. In the organic light emitting device comprising a reflective electrode, a transparent electrode, and an organic layer sandwiched between the transparent electrode and the transparent electrode, the organic layer includes at least a blue light emitting emitter, a green light emitting emitter, and a red light emitting emitter, The length from the light emitting point indicating the center in the film thickness direction of the light emitting position of the green light emitting emitter to the reflective electrode is in the range of 145 nm to 235 nm, and the center of the light emitting position of the blue light emitting emitter in the film thickness direction is The length from the light emitting point to the reflective electrode is in the range of 130 nm to 200 nm, and the length from the light emitting point indicating the center of the light emitting position of the red light emitting emitter in the film thickness direction to the reflective electrode is 170 nm. It is in the range of −275 nm.

Description

  The present invention relates to an organic light emitting device.

  In order to improve the light emission efficiency of the organic light emitting device, it is necessary to efficiently extract the light emitted from the organic layer to the air layer. The light emitted from the organic layer reaches the air layer through the transparent electrode and the substrate, but the light totally reflected at the boundary surface is attenuated due to the difference in refractive index between the transparent electrode and the air layer, and is emitted to the outside. There is a case that does not come. Therefore, the light actually extracted outside is only about 20% of the light emitted from the organic layer. In addition, about 40% is light in a non-light emitting mode, about 20% is light in a thin film mode (light attenuated by a transparent electrode), and about 20% is light in a substrate mode (light attenuated by a substrate). Note that the non-light emitting mode is also referred to as an evanescent mode (surface plasmon loss). This is a phenomenon that, in a region where the light emission position is close to the reflective electrode (metal), the emitted light is lost due to thermal deactivation due to the surface of the metal electrode and plasmon coupling.

  Patent Document 1 is a conventional example that improves the light extraction efficiency of an organic light emitting device. The organic light-emitting device of Patent Document 1 includes a transparent substrate and a light collecting structure layer. The light concentrating structure layer contains a cone-shaped or hemispherical structure.

JP 2010-225584 A

  In Patent Document 1, a condensing structure is provided on a boundary surface that totally reflects, and an attempt is made to extract as much light that is totally reflected at the interface without the structure to the next interface (finally the air layer). Yes. However, there is a problem that the light that is not totally reflected is totally reflected by providing the light collecting structure.

  The objective of this invention is providing the organic light-emitting device which can improve light extraction efficiency.

  In the organic light emitting device comprising a reflective electrode, a transparent electrode, and an organic layer sandwiched between the transparent electrode and the transparent electrode, the organic layer includes at least a blue light emitting emitter, a green light emitting emitter, and a red light emitting emitter, The length from the light emitting point indicating the center in the film thickness direction of the light emitting position of the green light emitting emitter to the reflective electrode is in the range of 145 nm to 235 nm, and the center of the light emitting position of the blue light emitting emitter in the film thickness direction is The length from the light emitting point to the reflective electrode is in the range of 130 nm to 200 nm, and the length from the light emitting point indicating the center of the light emitting position of the red light emitting emitter in the film thickness direction to the reflective electrode is 170 nm. It is in the range of −275 nm.

  According to the present invention, an organic light emitting device capable of extracting light with high efficiency is provided.

It is an organic light-emitting device which concerns on Example 1 of this invention. The detail of the light emission area 109 of FIG. 1 is shown. 1 shows a structure of a light emitting element to which a light extraction structure having a cone structure is added. The result of the light extraction ratio with respect to the number of steps of a cone is shown. 1 shows a structure of a light-emitting element to which a light extraction structure composed of a microlens structure is added. The result of the light extraction ratio with respect to the number of stages of microlenses is shown. The relationship between the light emission position of each luminescent color and the amount of light extracted outside is shown. The relationship between the light extraction efficiencies of two samples having different light emitting position orders is shown. It is a figure of the organic light-emitting device which concerns on Example 2 of this invention. It is a figure of the organic light-emitting device which concerns on Example 3 of this invention. It is a figure of the organic light-emitting device which concerns on Example 4 of this invention. It is a figure of the organic light-emitting device based on Example 5 of this invention.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. Are partly or entirely modified, application examples, detailed explanations, supplementary explanations, and the like. Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number. Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numbers and the like (including the number, numerical value, quantity, range, etc.).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram of an organic light emitting device according to Embodiment 1 of the present invention, which is a bottom emission type light source device that extracts light from the substrate 100 side. In FIG. 1, a transparent electrode 101, a first bank 104, a second bank 105, an organic layer 103, a reflective electrode 102, a light extraction layer 106, a sealing substrate 107, and an auxiliary wiring 108 are disposed on a substrate 100. . The transparent electrode 101 was an anode and the reflective electrode 102 was a cathode. A light source device is provided by including a drive circuit and a housing not shown in FIG. The reflective electrode 102 is connected to the transparent electrode 101 of the adjacent light emitting unit via the auxiliary wiring 108. Thereby, a light emission part can be connected in series. A light extraction layer 106 for extracting light confined in the transparent electrode 101 and the organic layer 103 is provided on the lower surface of the transparent electrode 101.

FIG. 2 shows details of the light emitting area 109 of FIG.
[substrate]
There are no particular limitations on the type of glass, plastic, etc., and the substrate 100 may be transparent for bottom emission and transparent or opaque for top emission depending on the device structure. Examples of the transparent substrate preferably used include glass, quartz, and a transparent resin film. In a substrate that is more flexible than a rigid substrate, the effect of suppressing high-temperature storage stability and chromaticity variation appears greatly, and thus a particularly preferable substrate has flexibility that can give flexibility to an organic EL element. It is a resin film. Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylates, heat-resistant transparent resin ARTON (registered trademark) (manufactured by JSR Corporation) or Apel (registered trademark) (Mitsui Chemicals, Inc.) Cycloolefin-based resins, etc.).

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± 2)% RH) is preferably 0.01 g / (m ² · 24 h) or less, and more preferably oxygen permeability measured by a method based on JIS K 7126-1987. Preferably, the film is a high barrier film having a degree of 0.001 cm ³ / (m ² · 24 h · atm) or less and a water vapor permeability of 0.001 g / (m ² · 24 h) or less. More preferably, it is 0.00001 g / (m ² · 24 h) or less.

The material for forming the barrier film may be any material that has a function of suppressing the intrusion of factors such as moisture and oxygen that cause deterioration of the organic light emitting element. For example, silicon oxide, silicon dioxide, silicon nitride, or the like is used. Can do. Furthermore, in order to improve the brittleness of the barrier film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma. A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.
[Transparent electrode]
The transparent electrode 101 formed as an anode is an electrode for injecting holes into the organic layer 103. As this anode, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function is used. It is preferable to use an electrode material having a work function of 4 eV or more. Specific examples of such electrode materials include metals such as gold, conductive transparent materials such as CuI, ITO (indium tin oxide), SnO ₂ , ZnO, and IZO (indium zinc oxide). For example, these electrode materials can be formed as a thin film by forming a film by a method such as a vacuum deposition method, a sputtering method, a CVD method, an ion plating method, or a coating method. The light transmittance of the transparent electrode (anode) is preferably 80% or more. The sheet resistance of the transparent electrode (anode) is preferably several hundred Ω / □ or less, and particularly preferably 100 Ω / □ or less. Further, the film thickness of the transparent electrode (anode) varies depending on the material in order to control the properties such as transparency and conductivity of the electrode (anode) as described above, but is set to 80 to 400 nm, more preferably 100. Set to ~ 200 nm.
[First bank]
The first bank 104 formed on the side surface of the organic light-emitting element has a forward taper, and has a patterned transparent electrode 101 and a metal layer (for example, Ag) provided as a partial reflection layer / auxiliary wiring. Cover and prevent partial short-circuit failure of light emitting part. After applying the bank forming material, the first bank 104 is formed by developing and exposing using a predetermined photomask. The surface of the first bank 104 on the side where the organic layer 103 is present may be subjected to water repellency treatment. For example, the surface of the first bank 104 is subjected to a plasma treatment with a fluorine-based gas, and the surface of the first bank 104 is fluorinated to perform the water repellency treatment. Thereby, a water repellent layer is formed on the surface of the first bank 104. Photosensitive polyimide is preferable as the first bank 104. As the first bank 104, an acrylic resin, a novolac resin, a phenol resin, a non-photosensitive material, or the like can be used.
[Second bank]
The second bank 105 is formed on the first bank 104. The second bank 105 has a reverse taper and is used to prevent the reflective electrode 102 of the adjacent light emitting portion from conducting. After applying the bank forming material, the second bank 105 is formed by developing and exposing using a predetermined photomask. The surface of the second bank 105 on the side where the organic layer 103 is present may be subjected to water repellency treatment. For example, the surface of the second bank 105 is subjected to a plasma treatment with a fluorine-based gas, and the surface of the second bank 105 is fluorinated to perform the water repellency treatment. Thereby, a water repellent layer is formed on the surface of the second bank 105. It is preferable to use a negative photoresist as the second bank 105. As the second bank 105, an acrylic resin, a novolac resin, a phenol resin, a non-photosensitive material, or the like can be used.
[Organic layer]
Details of the organic layer 103 are shown in FIG. 2, and the organic layer 103 has a single layer structure including only a light emitting layer (first light emitting layer 203), or an electron injection layer 205, an electron transport layer 204, a hole transport layer 202, and A multilayer structure including any one or more of the hole injection layers 201 may be used. The electron injection layer 205 and the electron transport layer 204, the electron transport layer 204 and the first light emitting layer 203, the first light emitting layer 203 and the hole transport layer 202, the hole transport layer 202 and the hole injection layer 201 are in contact with each other. Alternatively, the other layers described above may be interposed between the layers. The first light-emitting layer 203 includes a host molecule (hereinafter referred to as a host) and a dopant molecule (hereinafter referred to as a dopant). The organic light-emitting element in FIG. 1 is provided with a drive circuit, a housing, and the like to provide a light source device.
The hole transport layer transports holes and injects them into the light emitting layer. Therefore, the hole transport layer is preferably made of a hole transport material having high hole mobility. Further, it is desirable that the hole transport layer is chemically stable, has a high ionization potential, has a low electron affinity, and has a high glass transition temperature. Examples of the hole transport layer include N, N′-bis (3-methylphenyl) -N, N′-diphenyl- [1,1′-biphenyl] -4, 4′diamine (TPD), 4, 4 '-Bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD), 4, 4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (TCTA), 1, 3, 5-tris [N- (4-diphenylaminophenyl) phenylamino] benzene (p-DPA-TDAB), 4, 4 ′, 4 ″ -tris (N-carbazole) triphenylamine (TCTA), 1, 3 , 5-tris [N, N-bis (2-methylphenyl) -amino] -benzene (o-MTDAB), 1,3,5-tris [N, N-bis (3-methylphenyl) -amino]- Benzene (m-MTDAB) 1, 3, 5- Tris [N, N-bis (4-methylphenyl) -amino] -benzene (p-MTDAB), 4, 4 ′, 4 ″ -tris [1-naphthyl (phenyl) amino] triphenylamine (1-TNATA ), 4, 4 ′, 4 ″ -tris [2-naphthyl (phenyl) amino] triphenylamine (2-TNATA), 4, 4 ′, 4 ″ -tris [biphenyl-4-yl- (3- Methylphenyl) amino] triphenylamine (p-PMTDATA) 4,4 ′, 4 ″ -tris [9,9-dimethylfluoren-2-yl (phenyl) amino] triphenylamine (TFATA) 4,4 ', 4 "-tris (N-carbazoyl) triphenylamine (TCTA), 1,3,5-tris- [N- (4-diphenylaminophenyl) phenylamino] benzene (p-DPA-TD B) 1,3,5-tris {4- [methylphenyl (phenyl) amino] phenyl} benzene (MTDAPB), N, N′-di (biphenyl-4-yl) -N, N′-diphenyl [1 1′-biphenyl] -4,4′-diamine (p-BPD), N, N′-bis (9,9-dimethylfluoren-2-yl) -N, N′-diphenylfluorene-2,7- Diamine (PFFA), N, N, N ′, N′-tetrakis (9,9-dimethylfluoren-2-yl)-[1,1-biphenyl] -4, 4′-diamine (FFD), (NDA) PP, 4-4′-bis [N, N ′-(3-tolyl) amino] -3-3′-dimethylbiphenyl (HMTPD) and the like are desirable, and these may be used alone or in combination of two or more. May be.

  If necessary, a hole injection layer may be disposed between the transparent electrode as the anode and the hole transport layer. In order to lower the injection barrier between the anode and the hole transport layer, the hole injection layer is preferably formed of a material having an appropriate ionization potential. In addition, the hole injection layer desirably plays a role of filling the irregularities on the surface of the underlayer. Examples of the hole injection layer include copper phthalocyanine, starburst amine compound, polyaniline, polythiophene, vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide.

  Further, the hole transporting material may contain an oxidizing agent. Thereby, the barrier of an anode and a positive hole transport layer can be reduced, or electrical conductivity can be improved. Examples of the oxidizing agent include Lewis acid compounds such as ferric chloride, ammonium chloride, gallium chloride, indium chloride, and antimony pentachloride, electron-accepting compounds such as trinitrofluorene, and vanadium oxide mentioned as a hole injection material. Molybdenum oxide, ruthenium oxide, aluminum oxide and the like can be used, and these may be used alone or in combination of two or more.

  As the light-emitting organic compound used for the light-emitting layer, any known compounds can be used. For example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxy Quinolinate) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl) -4-yl) amine, 1-aryl-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, distilbenzene derivative, distilarylene (DSA) derivative, And these luminescent organic compounds in the molecule, but are not limited thereto. In addition to compounds derived from fluorescent dyes typified by these compounds, materials capable of phosphorescence emission from a triplet state and compounds having a group consisting of these in a part of the molecule can also be suitably used.

  The electron transport layer transports electrons and injects them into the light emitting layer. Therefore, the electron transport layer is preferably made of an electron transport material having high electron mobility. As the electron transport layer, for example, tris (8-quinolinol) aluminum, oxadiazole derivative, silole derivative, zinc benzothiazole complex, bathocuproine (BCP) is desirable, and one kind alone or two or more kinds may be used in combination. You can also.

  The electron transport layer preferably contains a reducing agent in the above electron transport material to lower the barrier between the buffer layer and the electron transport layer, or to improve the electric conductivity of the electron transport layer. . Examples of the reducing agent include alkali metals, alkaline earth metals, alkali metal oxides, alkaline earth oxides, rare earth oxides, alkali metal halides, alkaline earth halides, rare earth halides, alkali metals, and aromatics. The complex formed with a compound etc. is mentioned. Particularly preferred alkali metals are Cs, Li, Na and K. It is not restricted to these materials, You may use these materials individually by 1 type or in combination of 2 or more types.

Further, an electron injection layer may be inserted between the reflective electrode or buffer layer and the electron transport layer to improve electron injection efficiency. As the electron injection layer, for example, lithium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, magnesium oxide, aluminum oxide and the like are desirable. It is not restricted to these materials, You may use these materials individually by 1 type or in combination of 2 or more types.
[Reflective electrode]
The reflective electrode 102 formed in this embodiment is an electrode for injecting electrons into the organic layer 103, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function. It is preferable to use an electrode material having a work function of 5 eV or less. As such an electrode material, an alkali metal, an alkali metal halide, an alkali metal oxide, an alkaline earth metal, a rare earth, or an alloy of these with other metals can be used. for example, sodium - potassium alloy, lithium, magnesium, aluminum, magnesium - silver mixture, a magnesium - indium mixture, an aluminum - lithium alloy, Al / Al ₂ O ₃ mixture, Al / LiF mixture, and the like as examples. In addition, improvement in light extraction efficiency can be expected by using a material having high reflectance, and a typical material includes Ag. The reflective electrode can be produced, for example, by forming the electrode material described above into a thin film by a method such as vacuum deposition or sputtering, and the light transmittance of the reflective electrode is preferably 10% or less. The film thickness of the reflective electrode varies depending on the material in order to control the characteristics such as the light transmittance of the reflective electrode as described above, but is usually preferably set to 500 nm or less, and preferably in the range of 100 to 200 nm. It is good.
[Light extraction layer]
The light extraction layer used in the present invention refers to one in which a plurality of light collecting structures are arranged. Examples of the shape of the aggregate structure include a pyramid, a cone, a triangular pyramid, a cone structure composed of other polygonal cones, a structure such as a microlens, a grating, and a sea urchin. By using a structure such as a cone or a microlens array as the light extraction layer, light that has been attenuated in the substrate can be extracted to the outside, so that the light emission efficiency of the organic light emitting device is improved. This is not only because light refracts when passing through different media, but also actually returns partly, but under certain conditions, all reflects back. It is used.

The material of the light extraction layer of the present invention is preferably an organic compound such as a transparent resin from the viewpoint of processability of the light collecting structure. Examples of the transparent resin layer include ionizing radiation curable resins, thermosetting resins, and thermoplastic resins. Examples of the ionizing rays include ultraviolet rays, visible light, infrared rays, and electron beams. Specific examples include radical polymerization monomers or oligomers such as acrylate resins (epoxy acrylate, polyester acrylate, acrylic acrylate, ether acrylate), and epoxy resins. An initiator may be added as necessary. Examples of the initiator include a UV radical generator (Irgacure 907, 127, 192, etc., manufactured by Ciba Specialty Chemicals) and benzoyl peroxide. Representative examples of other resin components include aliphatic (for example, polyolefin) resins and urethane resins. The refractive index of the resin component is preferably 1.4 to 1.85, more preferably 1.7 to 1.8. By doing in this way, more light can be taken in in a transparent resin layer, and light extraction efficiency can be improved. In order to increase the refractive index of the base member, if necessary, high refractive index nanoparticles having a size that does not contribute to scattering can be added. Specifically, titanium oxide (refractive index: 2.5 to 2.7), zirconium oxide (refractive index: 2.4), barium titanate (refractive index: 2.4), strontium titanate (refractive index). : 2.37), bismuth oxide (refractive index: 2.45), and the like. These materials may be used alone or in combination of two or more. Moreover, only 1 type may be used for transparent particle | grains and 2 or more types may be used for it. Furthermore, the fine particles may be voids in the matrix.
FIG. 3 shows a structure of a light emitting element provided with a light extraction structure having a cone structure. The light extraction efficiency is calculated using the structure of the light emitting element. Here, 1 to 3 cones are arranged as a light extraction layer on an organic light emitting device composed of a lower reflective electrode, an organic layer, and a substrate. The light extraction efficiency is calculated using this structure. The bottom surface of the pyramid is square and the length of one side is fixed at a = 30 μm. The aspect ratio of the cone is defined as a value (height / bottom width) obtained by dividing the height h of the cone by a. The cone layer S1 is made of a base material having a refractive index of 1.8, the cone layer S2 is made of a refractive index of 1.5, and the cone layer S3 is made of a refractive index of 1.3. It is assumed that light is emitted at a position away from the lower reflective electrode by a distance d (light emitting point), and is emitted to the cone layer S1 in consideration of the interference effect between the light emitted from the light emitting position to the substrate and the light reflected by the reflective electrode. Calculate the amount of light. The light emitting point described here is defined as the center in the film thickness direction of the light emitting layer of the organic layer constituting the organic light emitting element. In this calculation, green monochromatic light having an emission center wavelength of 520 nm was used. As the light extracted to the air layer, the light incident on the cone layer S1 is calculated using a ray tracing method.

  FIG. 4 shows the result of the light extraction ratio with respect to the number of cones. This ratio is a relative ratio in which the amount of light incident on the cone layer S1 from the substrate having a refractive index of 1.8 is 1.

  In Configuration 1, the aspect ratio was 0.5 or more and the light extraction ratio was about 74% or more, but the peak value did not reach 76%.

  Next, Configuration 2 will be examined. When the aspect ratio of the cone layer S1 is set to 0.75 at which the light extraction ratio of the configuration 1 is maximized, the aspect ratio of the cone layer S2 is 80% in the range of 0.3 to 1.9. This value is larger than the maximum value of the light extraction ratio of Configuration 1. The light extraction ratio is the highest when the aspect ratio of the cone layer S2 is 0.75. Examination of Configuration 2 shows that the light extraction ratio is improved by providing two layers of cone layers than by providing one layer of cone layers, depending on the numerical value of the aspect ratio.

  In the configuration 2, the example in which the aspect ratio of the cone layer S1 is 0.75 has been described. However, the aspect ratio of the cone layer S1 is 0.5 or more, and the aspect ratio of the cone layer S2 is 0.3 or more and 1 If it is in the range of .9 or less, the light extraction ratio is improved as compared with the case where one cone layer is provided.

  Next, Configuration 3 will be examined. When the aspect ratio of the cone layer S1 is 0.75 at which the light extraction ratio of the configuration 2 is maximized and the aspect ratio of the cone layer S2 is 0.75 at which the light extraction ratio of the configuration 2 is maximized, the cone layer S3 The aspect ratio is 80% in the range of 0.3 to 1.9. This value is larger than the maximum value of the light extraction ratio of Configuration 1. However, the peak location of the light extraction ratio was lower in Configuration 3 than in Configuration 2. Examination of Configuration 3 reveals that even if the aspect ratio is devised, the light extraction ratio is improved when two cone layers are provided compared with three cone layers when compared with the maximum value.

  From the examination so far, it was found that it is desirable to arrange the cone structure in two stages. In particular, it is desirable that the aspect ratio of the cone layer S1 is 0.5 or more and the aspect ratio of the cone layer S2 is 0.3 or more and 1.9 or less. On the other hand, in order to simplify the configuration, a one-stage arrangement is desirable.

  FIG. 5 shows a structure of a light emitting element provided with a light extraction structure having a microlens structure. The light extraction efficiency is calculated using the structure of the light emitting element. Here, a three-stage microlens layer is arranged as a light extraction layer on an organic light-emitting element composed of a lower reflective electrode, an organic layer, and a substrate. The light extraction efficiency is calculated using this structure. The bottom surface of the microlens is circular and the length of the diameter is fixed at a = 50 μm. The aspect ratio of the microlens is defined as a value obtained by dividing the height h of the microlens by a. The microlens layer M1 is made of a base material having a refractive index of 1.8, the microlens layer M2 is made of a refractive index of 1.5, and the microlens layer M3 is made of a base material having a refractive index of 1.3. It is assumed that light is emitted at a position away from the lower reflective electrode by a distance d (light emitting point), and is emitted to the microlens layer M1 in consideration of the interference effect between the light emitted from the light emitting position to the substrate and the light reflected by the reflective electrode. Calculate the amount of light. The light emitting point described here is defined as the center in the film thickness direction of the light emitting layer of the organic layer constituting the organic light emitting element. In this calculation, green monochromatic light having an emission center wavelength of 520 nm was used. As the light extracted to the air layer, the light incident on the microlens layer M1 is calculated using a ray tracing method.

  FIG. 6 shows the result of the light extraction efficiency with respect to the number of microlenses. In the structure of the microlens, the light extraction efficiency of the three-stage microlens is improved slightly compared to the two-stage. Therefore, a one-stage, two-stage, or three-stage arrangement is desirable.

This light extraction ratio is a relative ratio in which the amount of light incident on the microlens layer M1 from the substrate having a refractive index of 1.8 is 1. In Configuration 4, the aspect ratio is 0.9 or more, and the light extraction ratio is about 71.5% or more. Next, in the configuration 5, when the aspect ratio of the microlens layer M1 is 0.9 or more that maximizes the light extraction ratio of the configuration 4, the aspect ratio of the microlens layer M2 is 0.8 or more and 77.5% or more. It becomes. This value is larger than the peak value of the light extraction ratio of Configuration 4. Next, in the configuration 6, when the aspect ratio of the microlens layer M1 is 0.9 or more and the aspect ratio of the microlens layer M2 is 0.8 or more, the aspect ratio of the microlens layer M3 is 0.4 or more and 1.0. It is 78% or more in the following range. This value is larger than the peak value of configuration 5. Therefore, the microlens structure is desirably arranged in three stages. In the microlens structure, the light extraction efficiency of the three-stage microlens is improved slightly compared to the two-stage.
[White light emitting optical design]
White light emission has a plurality of emission points of emission colors. The optical interference condition is uniquely determined by a value obtained by dividing the optical length obtained by multiplying the film thickness (d) of the organic film constituting the light emitting point to the reflective electrode by the refractive index of the organic material by the emission wavelength. Therefore, it can be seen that the optimum optical conditions and the film thickness of the organic film are longer for long wavelength light emission than for short wavelength.

  FIG. 7 shows blue (B): Flrpic, green (G): Ir (pbi) 2OcOPhtaz, yellow (Y): Ir (t-Bu-ptp) 2OcOPhtaz, and red (R): Ir as dopants for white organic EL. (Pq) The relationship between the emission position of each emission color and the amount of light extracted to the outside when 2F7taz is used is shown. As can be seen from FIG. 7, the light emission position at which the light extraction efficiency is maximized differs for each emission color. The light distribution at the peak position where the light extraction efficiency of each color is maximized is a distribution close to perfect diffusion (Lambertian). That is, each light emission has an appropriate distance for improving the light extraction efficiency because of the distribution of light distribution, and it is important to optically design in the light emission position range equal to or more than half the peak value in FIG. For example, the emission position of the green emitter is in the range from 145 nm to 235 nm from the emission center to the reflection electrode, the emission position of blue emitter is in the range from 130 nm to 200 nm from the emission center to the reflection electrode, and the emission position of the red emitter is The distance from the light emission center to the reflective electrode is in the range of 170 nm to 275 nm. By separating from the above range, the light extraction efficiency is significantly reduced.

FIG. 8 shows the relationship between the light extraction efficiencies including non-propagating light of Sample A in which light emitting points are arranged in the order of red, green, and blue from the electrode side and Sample B in which blue, green, and red are arranged in the order from the electrode side. The light extraction efficiency is greatly increased by controlling the order of the light emission positions and controlling the light emission position near the center wavelength of the emission color. Also, in the region where the light emission position is close to the reflective electrode, the proportion of non-propagating light due to the evanescent mode (surface plasmon loss) is large, and increasing the proportion of propagating light by separating the distance of the light emitting position from the reflective electrode improves the light extraction efficiency. Is important. Here, the amount of light extraction is most improved in the white organic EL element that is optically designed at the center wavelength of the emission color and the emission positions are arranged in order of wavelength from the electrode side. If the emission position of the central wavelength of the emission color at that time is 155 nm to 250 nm from the reflective electrode, it is possible to obtain light extraction efficiency of 60% or more by controlling the light distribution. In the case of no sample A light distribution control, a light extraction efficiency of about 50% can be obtained at a light emission position of 170 nm to 225 nm. As a result, the light extraction efficiency can be improved and the engineering design range can be expanded by controlling the light distribution.
[Sealing substrate]
As the sealing substrate 107, transparent glass plates such as soda lime glass and alkali-free glass, acrylic resin, PET resin, PEN resin, cycloolefin resin, olefin resin, carbonate resin, nylon resin, fluorine resin, silicone resin, A transparent plastic plate such as polyimide resin or polysulfone resin can be used. In this case, it is desirable to use a plastic substrate having an appropriate gas barrier film. The sealing substrate 107 may be light-transmitting, and may be slightly colored in addition to being colorless and transparent. In particular, those that transmit light in the wavelength range of 380 nm to 780 nm are desirable.

The organic light emitting element used here may be a single element or an element divided into a plurality of elements. Examples of the method of connecting a plurality of elements include a method in which each element is connected in series, in parallel, or a combination thereof.
[Auxiliary wiring]
The auxiliary wiring 108 formed in this example serves to reduce the resistance component of the electrode by being arranged on the line with a width of 1 μm to 20 μm on the transparent electrode. These auxiliary wirings are preferably made of a metal or alloy material having a high reflectance and a low resistance value. Examples of such materials include alkali metals, alkali metal halides, alloys of these with other metals, such as Ag, Al, sodium, sodium-potassium alloy, lithium, magnesium, Examples include aluminum, a magnesium-silver mixture, a magnesium-indium mixture, an aluminum-lithium alloy, an Al / Al ₂ O ₃ mixture, an Al / LiF mixture, and the like. The reflective electrode / auxiliary wiring can be produced, for example, by forming the above electrode material into a thin film by a method such as a vacuum deposition method or a sputtering method, a printing method, or the like. The light transmittance is preferably 10% or less.
[overall structure]
It is a figure of the organic light emitting element which shows an example of embodiment of this invention. As shown in FIG. 2, the organic light emitting device according to Example 1 includes, in order from the bottom, a third resin layer 110, a substrate 100, a second resin layer 111, a first resin layer 106, a planarization layer 207, The transparent electrode 101, the hole injection layer 201, the hole transport layer 202, the first light emitting layer 203, the electron transport layer 204, and the electron injection layer 205 are configured.

The second resin layer 111 was attached to the substrate 100 by curing the photocurable resin. The second resin layer 111 has a cone structure. The cone structure was prepared by applying a photo-curing resin on polyethylene terephthalate (PET) as a base material, molding and photo-curing. The bottom surface of the cone structure is a square, the length a of the base is 30 μm, and the height h is 10 μm. The refractive index of the second resin layer 111 is 1.5. On top of this, a high refractive index resin having a refractive index of 1.8 was applied and thermally cured to form the first resin layer 106. As the first resin layer 106, an epoxy resin is used as a base material and zirconia (ZrO ₂ ) fine particles having a particle diameter of _{2 to 4} nm are dispersed.

  Next, a high refractive index resin having a refractive index of 1.8 was applied as the planarizing layer 207 on the first resin layer 106 and thermally cured. As the planarizing layer 207, a urethane resin was used as a base material and zirconia fine particles having a particle diameter of 2-4 nm were dispersed. It selected so that the high refractive index resin used for the 1st resin layer 106 might become insoluble with respect to the solvent used for the high refractive index resin of the planarization layer 207. An ITO film having a thickness of 150 nm was formed thereon as the transparent electrode 101. Subsequently, a positive type novolac photoresist (TFR-970: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin coated. The film thickness at this time was about 2 μm. Then, the 1st bank 104 was formed by performing patterning by exposure and image development.

On the first bank 104, 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD) and molybdenum oxide (MoO ₃ ) have a molar ratio of 1: 1. The hole injection layer 201 was formed by co-evaporation at a deposition rate. The thickness of the hole injection layer 201 is 60 nm. Next, α-NPD was deposited thereon at a deposition rate of 0.2 nm / s to form a hole transport layer 202. The thickness of the hole transport layer 202 is 20 nm. Next, CBP and Ir (ppy) ₃ were co-evaporated so that the deposition rates were 0.2 nm / s and 0.02 nm / s, respectively, whereby the first light-emitting layer 203 was formed. The thickness of the first light emitting layer 203 is 40 nm. Next, bathophenanthroline (BCP) was deposited thereon at a deposition rate of 0.2 nm / s to form the electron transport layer 204. The film thickness of the electron transport layer 204 is 20 nm. On top of that, BCP and Cs were co-deposited at a molar ratio of 1: 1 to a thickness of 195 nm to form an electron injection layer 205. On top of this, Ag was deposited by vapor deposition to form the reflective electrode 102.

  Next, the high-purity nitrogen gas was circulated and moved to a sealing chamber maintaining a high dew point without exposing the substrate 100 on which the organic light-emitting element was formed to the atmosphere. A photocuring resin for sealing was drawn on the edge portion of the sealing substrate 107 using a known seal dispenser device (not shown). Further, a photocurable sealing material made of an epoxy resin was applied to the side of the sealing substrate 107 where the organic light emitting element was provided. Then, the sealing substrate 107 and the substrate 100 were bonded to each other and bonded to the bonding apparatus in the sealing chamber. Next, the sealing substrate 107 and the substrate 100 were bonded together, and UV light was irradiated from the sealing substrate 107 side to cure the photo-curing resin.

  Next, a third resin layer 110 was formed. The formation method is the same formation method as the second resin layer 111, and the length a of the base of the cone structure included in the third resin layer 110 is 30 μm, and the height h is 30 μm. The third resin layer 110 was attached to the surface of the substrate 100 opposite to the surface on which the organic light emitting element was formed with an adhesive resin.

  In FIG. 2, the first resin layer 106 has a cone structure on the surface where the second resin layer 111 is present. In addition, the second resin layer 111 has a cone structure in the description of the manufacturing process, but in other words, the second resin layer 111 has a filling structure that fills between the cone structures of the plurality of first resin layers 106. I can say that. The third resin layer 110 has a cone structure on the side opposite to the side where the second resin layer 111 is present.

  The refractive index of the first resin layer 106 is preferably 1.6 to 1.8. The light extraction efficiency is improved when the refractive index is decreased from the first resin layer 106 toward the air layer (refractive index: 1.0). Therefore, for example, the refractive index of the second resin layer 111 is preferably 1.3 to 1.6, and the refractive index of the third resin layer 110 is preferably 1.3 to 1.6.

  Note that even when any layer (such as a sealing substrate) is provided between the resin layers, an air layer (refractive index: 1.0) is formed from the first resin layer 106 in consideration of improvement in light extraction efficiency. A structure in which the refractive index is decreased toward the surface is preferable.

  In this way, an organic light emitting device having a bottom emission type structure corresponding to FIG. 2 was produced. As a comparative example, an element in which the first resin layer 106 and the planarization layer 207 are not provided was manufactured. The light extraction efficiency of the same configuration was 24%. In the organic light emitting device of Example 1, the light extraction efficiency was 72%, and the performance was improved 3 times.

  FIG. 9 is a diagram of an organic light-emitting device according to Example 2 of the present invention. The difference from the first embodiment is that the device structure uses a top emission structure. An example of a manufacturing process is shown below.

  On the substrate 100 (glass substrate), an Ag film having a thickness of 150 nm and an IZO film having a thickness of 30 nm are formed as the reflective electrode 102.

A co-deposited film of α-NPD and MoO ₃ was formed thereon as the hole injection layer 201. The production conditions were the same as in Example 1, and the film thickness was 175 nm. A hole transport layer 202 was formed thereon. The production conditions are the same as in Example 1. A first light emitting layer 203 is formed thereon. It is a co-deposited film made of CBP as a host material, Ir (ppy) _{3 as} a green dopant, and tris (1-phenylisoquinoline) iridium (III) (Ir (piq) ₃ ) as a red dopant. The dopant concentration defined by the deposition rate of the dopant with respect to the host was 10% for the green dopant and 1% for the red dopant. The thickness of the first light emitting layer 203 was 20 nm. Next, a second light-emitting layer 206 was formed thereon. The host material is 1,3-bis (N-carbazolyl) benzene (mCP), and the blue dopant is (2-carboxypyridyl) bis (3,5-difluoro-2- (2-pyridyl) phenyl) iridium (FIrpic). It is a co-deposited film. The blue dopant concentration was 20% and the film thickness was 20 nm. An electron transport layer 204 and an electron injection layer 205 were formed thereon. The production conditions are the same as in Example 1. However, the film thickness of the electron injection layer was 60 nm.

On top of that, an IZO film was formed as the transparent electrode 101 by sputtering. The film thickness was 30 nm. On top of that, SiN _x was deposited as a protective layer 112 by CVD. The film thickness was 150 nm.

On top of that, a high refractive index resin having a refractive index of 1.8 using an epoxy resin in which ZrO ₂ is dispersed was applied, and the first resin layer 106 was formed by mold molding and thermosetting. A second resin layer 111 was formed thereon by applying a thermosetting epoxy resin. On top of that, a third resin layer 110 produced under the same conditions as in Example 1 was attached with an adhesive resin.

  In this manner, an organic light emitting device having a top emission type configuration corresponding to FIG. 9 was produced. As a comparative example, an element in which the first resin layer 106, the second resin layer 111, and the third resin layer 110 are not provided was manufactured. The light extraction efficiency of the same configuration was 24%. In the organic light emitting device of Example 2, the light extraction efficiency was 72%, and the performance was improved 3 times.

  FIG. 10 is a diagram of an organic light-emitting device according to Example 3 of the present invention. An example of a manufacturing process is shown below.

On the substrate 100 (glass substrate), the reflective electrode 102, the organic layer 103, the transparent electrode 101, and the protective layer 112 were produced under the same conditions as in Example 2. Next, the second resin layer 111 was formed on one surface of the sealing substrate 107. The production conditions are the same as those of the first resin layer 106 of Example 1. A high refractive index resin having a refractive index of 1.8 using an epoxy resin in which ZrO ₂ is dispersed is applied thereon, so that a first resin layer 106 is formed. A high refractive index adhesive layer 113 having a refractive index of 1.8 or more is attached to the sealing substrate 107 so that the substrate 100 on which the organic light emitting element is formed, the protective layer 112, and the high refractive index adhesive layer 113 are in close contact with each other. Pasted together. Next, in the sealing substrate 107, the third resin layer 110 was formed on the surface opposite to the surface on which the second resin layer 111, the first resin layer 106, and the high refractive index adhesive layer 113 were formed. The production conditions are the same as in Example 2.

  In this way, an organic light emitting device having a top emission type configuration corresponding to FIG. 10 was produced. As a comparative example, an element in which the first resin layer 106, the second resin layer 111, and the third resin layer 110 are not provided was manufactured. The light extraction efficiency of the same configuration was 24%. In the organic light emitting device of Example 3, the light extraction efficiency was 72%, and the performance was improved 3 times.

  FIG. 11 is a diagram of an organic light emitting device showing an example of an embodiment of the present invention. An example of a manufacturing process is shown below.

  On the substrate 100 (glass substrate), the reflective electrode 102, the organic layer 103, the transparent electrode 101, and the protective layer 112 were produced under the same conditions as in Example 2. A first resin layer 106 was formed thereon. The production conditions are the same as those for the first resin layer 106 of Example 2.

  In this way, an organic light emitting device having a top emission type structure corresponding to FIG. 11 was produced. As a comparative example, an element in which the first resin layer 106, the second resin layer 111, and the third resin layer 110 are not provided was manufactured. The light extraction efficiency of the same configuration was 24%. In the organic light emitting device of Example 4, the light extraction efficiency was 66%, and the performance was improved 2.75 times. In the fourth embodiment, the configuration in which the sealing substrate 107 is not used and the cone structure is provided in one stage has been described.

  FIG. 12 is a diagram of an organic light emitting device showing an example of an embodiment of the present invention. An example of a manufacturing process is shown below.

  On the substrate 100 (glass substrate), the reflective electrode 102, the organic layer 103, the transparent electrode 101, and the protective layer 112 were produced under the same conditions as in Example 2.

  Next, a fourth resin layer 114 was formed on one side of the sealing substrate 107. The fourth resin layer 114 has a microlens structure. A photo-curing resin having a refractive index of 1.8 was applied to the sealing substrate 107, and a fourth resin layer 114 was produced by a mold molding and photo-curing procedure. The diameter a of the bottom surface of the microlens is 20 μm, and the height h is 5 μm. A thermosetting resin having a refractive index of 1.5 was applied thereon to produce a fifth resin layer 117. Next, a thermosetting resin having a refractive index of 1.5 was applied, and a sixth resin layer 115 was produced by mold molding and photocuring. The sixth resin layer 115 has a microlens structure. a and h were 20 μm and 4 μm, respectively. A seventh resin layer 118 was formed thereon by applying a thermosetting resin having a refractive index of 1.3. Next, a sealing substrate 107 (refractive index 1.3) was provided. Finally, the eighth resin layer 116 was formed on the surface of the sealing substrate 107 opposite to the surface on which the fourth resin layer 114 to the seventh resin layer 118 were formed. The eighth resin layer 116 has a microlens structure. The formation method is the same as in Example 3. However, a and h were 20 μm and 10 μm, respectively.

  In this way, an organic light emitting device having a top emission type structure corresponding to FIG. 12 was produced. As a comparative example, an element in which the five resin layers of the fourth resin layer 114 to the eighth resin layer 116 were not installed was manufactured. The light extraction efficiency of the same configuration was 24%. In the organic light emitting device of Example 5, the light extraction efficiency was 68%, and the performance was improved 2.8 times. In this embodiment, the three-stage microlens layer is used, but a two-stage or one-stage microlens layer may be used. The two-stage microlens layer is a cone shown in the second and third embodiments. The structure may be a microlens structure. The one-stage microlens structure is the structure shown in the fourth embodiment, and the cone structure may be replaced with the microlens structure.

DESCRIPTION OF SYMBOLS 100 ... Substrate, 101 ... Transparent electrode, 102 ... Reflective electrode, 103 ... Organic layer, 104 ... First bank, 105 ... Second bank, 106 ... First resin layer, 107 ... Sealing substrate, 108 ... Reflection Layer / auxiliary wiring, 109 ... light emitting area, 110 ... third resin layer, 111 ... second resin layer, 112 ... protective layer, 113 ... high refractive index adhesive layer, 114 ... fourth resin layer, 115 ... first 6 ... microlens layer, 116 ... eighth resin layer, 117 ... fifth resin layer, 118 ... seventh resin layer, 201 ... hole injection layer, 202 ... hole transport layer, 203 ... first light emission Layer, 204 ... electron transport layer, 205 ... electron injection layer, 206 ... second light emitting layer, 207 ... planarization layer

Claims (12)

In an organic light emitting device comprising a reflective electrode, a transparent electrode, and an organic layer sandwiched between the transparent electrode and the transparent electrode,
The organic layer includes at least a blue light emitting emitter, a green light emitting emitter, and a red light emitting emitter,
The length from the light emitting point indicating the center of the light emitting position of the green light emitting emitter in the film thickness direction to the reflective electrode is in the range of 145 nm to 235 nm,
The length from the light emitting point indicating the center of the light emitting position of the blue light emitting emitter in the film thickness direction to the reflective electrode is in the range of 130 nm to 200 nm,
An organic light emitting device characterized in that a length from a light emitting point indicating a center of a light emitting position of the red light emitting emitter in a film thickness direction to the reflective electrode is in a range of 170 nm to 275 nm. The organic light emitting device according to claim 1,
An organic light emitting device having light emitting points in the order of blue light emission, green light emission, and red light emission from the reflective electrode side. The organic light-emitting device according to claim 1 or 2,
From the light emitting layer toward the light extraction direction, the first resin layer, the second resin layer, the third resin layer,
The refractive index of the first resin layer is 1.6 to 1.8,
The organic light-emitting device, wherein the second resin layer and the third resin layer have a refractive index smaller than that of the first resin layer. The organic light emitting device according to claim 3.
The first resin layer has a cone structure on the surface on the side where the second resin layer exists,
The second resin layer has a filling structure that fills between the cone structures of the plurality of first resin layers,
The organic light-emitting device, wherein the third resin layer has a conical structure on a surface opposite to a side on which the second resin layer is present. The organic light emitting device according to claim 4,
The aspect ratio (height / bottom width) of the cone structure of the first resin layer is 0.5 or more,
An aspect ratio (height / bottom width) of the cone structure of the third resin layer is 0.3 or more and 1.9 or less, and the organic light emitting device. The organic light emitting device according to claim 3.
The first resin layer has a microlens structure on the surface on the side where the second resin layer exists,
The second resin layer has a filling structure that fills between the microlens structures of the plurality of first resin layers,
The organic light-emitting device, wherein the third resin layer has a microlens structure on a surface opposite to a side on which the second resin layer is present. The organic light-emitting device according to claim 6.
The aspect ratio (height / bottom width) of the microlens structure of the first resin layer is 0.9 or more,
An organic light-emitting device, wherein an aspect ratio (height / bottom width) of the microlens structure of the third resin layer is 0.8 or more. The organic light-emitting device according to claim 6 or 7,
Furthermore, it has a 4th resin layer and a 5th resin layer,
The refractive index of the fourth resin layer and the fifth resin layer is smaller than the refractive index of the first resin layer, the refractive index of the second resin layer, and the refractive index of the third resin layer. An organic light emitting device characterized by that. The organic light-emitting device according to claim 8,
The fourth resin layer has a filling structure that fills between the microlens structures of the plurality of third resin layers,
The organic light-emitting device, wherein the fifth resin layer has a microlens structure on a surface opposite to a side on which the fourth resin layer is present. The organic light emitting device according to any one of claims 3 to 9,
An organic light emitting device having a bottom emission structure. The organic light emitting device according to any one of claims 3 to 9,
An organic light emitting device having a top emission structure. The organic light-emitting device according to any one of claims 3 to 11,
The organic light-emitting device, wherein the second resin layer is a photo-curing resin.

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