JPWO2015029202A1 - Organic light emitting device - Google Patents

Abstract

In order to improve the light extraction efficiency, the present invention for providing an organic light-emitting device characterized by high light extraction efficiency and excellent flatness of the ITO surface, the second light extraction layer, An organic light emitting device in which a substrate, a first light extraction layer, a planarization layer, a first electrode, an organic layer, and a second electrode are provided in order, the organic layer including a light emitting layer, One light extraction layer and the second light extraction layer contain scattering fine particles, and the light emitting point indicating the center of the light emitting position of the dopant in the light emitting layer in the film thickness direction is blue, green from the second electrode side. The red light is disposed in the order of red, and the length from the green light emitting point to the second electrode is in the range of 145 nm to 235 nm.

Description

  The present invention relates to an organic light-emitting element used in a lighting fixture, a display device, a liquid crystal backlight, a display device and the like.

  Organic electroluminescent elements (hereinafter referred to as “organic light-emitting elements”) are expected as illumination devices for thin display devices and liquid crystal display devices. The organic light emitting display device includes a plurality of organic light emitting elements that constitute pixels on a substrate and a driving layer that drives the organic light emitting elements. This organic light emitting device has a structure in which a plurality of organic layers are sandwiched between a reflective electrode and a transparent electrode. The plurality of organic layers include at least a transport layer that transports holes, a transport layer that includes electrons, and a light-emitting layer that recombines holes and electrons. In the organic light emitting device, by applying a voltage between both electrodes, holes and electrons injected from the electrode are recombined in the light emitting layer to emit light.

  In this organic light emitting device, it is necessary to extract light emitted from the light emitting layer having a refractive index of less than 2 into an air layer having a refractive index of 1. The interface between the high refractive index layer and the low refractive index layer has a critical angle at which light incident at a deep angle with respect to the interface normal direction is reflected by 100%. That is, light incident at an angle deeper than the critical angle is not emitted to the air layer but is reflected inside the organic light emitting element. Generally, the ratio of light that can be extracted to the air layer of the organic light emitting element is about 20%, and 80% of the light stays inside the organic light emitting element. About 40% is a non-emission mode, about 20% is a thin film mode (light attenuated by a transparent electrode), and about 20% is 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.

  In response to this problem, in recent years, an organic EL light emitting device that includes a light extraction layer between a transparent substrate and a transparent electrode, and extracts light emitted from the organic light emitting layer from the light extraction layer and the transparent electrode through the transparent substrate. (See, for example, Patent Documents 1, 2, 3, and 6). Further, reduction of total reflection at the interface when light is extracted from the substrate to the air layer is also an issue, and attempts have been made to provide a low refractive index layer for the purpose of reducing total reflection (for example, Patent Documents 4 and 5). reference).

  In Patent Document 1, the light extraction layer includes a light scattering layer and a planarization layer. The light scattering layer is formed by mixing a light scattering region composed of light scattering particles and a binder resin and a light transmission region having a lower light scattering particle content ratio than the light scattering region in the surface direction. It has been reported that by providing such a configuration, it is possible to increase the efficiency of light extraction in an oblique direction and suppress light with high efficiency while suppressing reduction of front extraction light. However, when the content density of the light scattering particles is different in the plane direction, it is considered that the uniformity of the film thickness in the plane direction is inferior. In addition, a flattening layer is provided in order to smooth the irregularities on the surface of the light scattering layer. However, since the refractive index of the resin constituting the planarization layer is smaller than that of ITO, there is a concern that the amount of light extracted to the planarization layer is greatly reduced.

  Patent Document 2 also reports on an organic light-emitting device having a light extraction layer and a planarization layer containing a transparent resin and light-transmitting particles, but the transparent resin has a small refractive index and is taken out to the planarization layer. Aggregation of particles is expected from the fact that the amount of light is reduced and the surface treatment is not performed on the light transmissive particles.

  In Patent Document 3, although the silane coupling treatment is performed on the fine particles contained in the light extraction layer, it is considered that the flatness cannot be sufficiently obtained because the planarization layer is not provided.

  Patent Document 4 is characterized in that the refractive index decreases from the transparent substrate side toward the outside of the element, and is a single-layer film in which the refractive index of the porous antireflection film continuously changes. .

  However, since the hole diameter is not controlled, sufficient light extraction efficiency cannot be obtained.

  In Patent Document 5, the light extraction layer is composed of a resin layer, fine particles having a refractive index different from that of the resin layer, and bubbles of a level at which the resin becomes cloudy, but the fine particles are not subjected to surface treatment and contain a large number of bubbles. Therefore, it is considered that the interfacial adhesion within the film is inferior.

  Patent Document 6 reports a matrix made of transparent resin and an anisotropic scattering layer made of flat domains. According to this document, the light extraction efficiency is improved when the aspect ratio (diameter / thickness) of the flat domain is 2 or more and the angle formed by the main plane of the flat domain and the anisotropic scattering layer is within 30 degrees. It says that. However, if there are variations in the light distribution, there are concerns about deterioration of surface irregularities, in-plane variations in light extraction efficiency, and the like.

JP 2009-76452 A JP 2006-100042 A JP 2012-155868 A JP 2005-339927 A JP 2009-245786 A JP 2010-212184 A

  In the organic light emitting device, it is important to improve the light extraction efficiency by reducing total reflection in the organic light emitting device or at the air interface. In particular, in a bottom emission type organic light emitting device that extracts light emitted from the organic layer from the anode (ITO) side, flatness of the ITO surface is important.

  Accordingly, the present inventor provides an organic light emitting device characterized by high light extraction efficiency and excellent flatness of the ITO surface.

  In the present invention, in order to improve the light extraction efficiency, a second light extraction layer, a substrate, a first light extraction layer, a planarization layer, a first electrode, an organic layer, and a second electrode are sequentially provided. The organic layer includes a light emitting layer, the first light extraction layer and the second light extraction layer include scattering fine particles, and the light emission position of the dopant in the light emission layer is determined. About the light emission point which shows the center of a film thickness direction, it arrange | positions in order of blue, green, red from said 2nd electrode side, and the length from the said green light emission point to said 2nd electrode is in the range of 145 nm-235 nm. It was.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to improve the flatness of ITO surface with the improvement of the light extraction efficiency of an organic light emitting element.

It is a figure of the organic light-emitting device which shows one example of embodiment of this invention. The detail of the light emission area 111 of FIG. 1 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. 6 is a graph showing the relationship between the extraction efficiency of light emitted from the light emitting layer 203 and the refractive index of the planarization layer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following examples.

  FIG. 1 is a diagram of an organic light emitting device showing an example of an embodiment 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 102, a first bank 105, a second bank 106, an organic layer 104, a reflective electrode 103, a first light extraction layer 107, a planarization layer 108, a sealing substrate 109, A reflective layer / auxiliary wiring 110 is disposed. The transparent electrode 102 was an anode and the reflective electrode 103 was a cathode. A second light extraction layer 101 is provided on the opposite side of the substrate 100. A light source device is provided by including a drive circuit and a housing not shown in FIG. The reflective electrode 103 is connected to the transparent electrode 102 of the adjacent light emitting unit via the reflective / auxiliary wiring 110. Thereby, a light emission part can be connected in series. A first light extraction layer 107 and a second light extraction layer 101 for extracting light confined in the transparent electrode 102 and the organic layer 104 are provided on the lower surface of the transparent electrode 102.

FIG. 2 shows details of the light emitting area 111 of FIG. A light distribution control layer 206 having a function of optically adjusting the positions of the reflective electrode 103 and the light emitting layer 203 was used.
[substrate]
The substrate 100 can be selected from a wide range as long as it is an insulating material.

Specifically, inorganic materials such as glass and an alumina sintered body, various insulating plastics such as a polyimide film, a polyester film, a polyethylene film, a polyphenyllene sulfide film, and a polyparaxylene film can be used. Further, if the insulating material is formed on the surface, there is no problem even with a metal material (for example, stainless steel, Al, Cu, an alloy containing the above metal, or the like).
[Transparent electrode]
The transparent electrode 102 formed as an anode is an electrode for injecting holes into the organic layer 104, and is preferably a conductive film having a large work function that increases the efficiency of hole injection.

  Specific examples include gold and platinum, but are not limited to these materials. The anode may be a binary system such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium germanium oxide, or a ternary system such as indium tin zinc oxide. Moreover, the composition which has tin oxide, zinc oxide, etc. as a main component besides indium oxide may be sufficient. In the case of ITO, a composition containing 5-10 wt% tin oxide with respect to indium oxide is often used.

  Examples of the method for manufacturing the oxide semiconductor include a sputtering method, an EB vapor deposition method, and an ion plating method. The work functions of the ITO film and the IZO film are 4.6 eV and 4.6 eV, respectively, but can be increased to about 5.2 eV by UV ozone irradiation, oxygen plasma treatment, or the like.

  The ITO film becomes a polycrystalline state when it is fabricated using a sputtering method and the substrate temperature is increased to about 200 ° C. In this polycrystal state, the surface flatness is poor due to crystal grains, so that the surface is preferably polished. As another method, it is desirable to heat a material formed in an amorphous state to a polycrystalline state.

In addition, the provision of the hole injection layer for the anode eliminates the need to use a material having a high work function, and an ordinary conductive film is sufficient. Specifically, metals such as Al, In, Mo, Ni, alloys using these metals, and inorganic materials such as polysilicon, amorphous silicon, tin oxide, indium oxide, indium / tin oxide (ITO) Is desirable.
[First bank]
The first bank 105 formed on the side surface of the organic light emitting element has a forward taper, and the metal layer (for example, Ag) provided as the end portion of the patterned transparent electrode 102 and the partially reflecting layer / auxiliary wiring 110. To prevent partial short-circuit failure of the light emitting part. After applying the bank forming material, the first bank 105 is formed by developing and exposing using a predetermined photomask. The surface of the first bank 105 on the side where the organic layer is present may be subjected to water repellency treatment. For example, the surface of the first bank 105 is subjected to a plasma treatment with a fluorine-based gas, and the surface of the first bank 105 is fluorinated to perform the water repellency treatment. Thereby, a water repellent layer is formed on the surface of the first bank 105. As the first bank 105, photosensitive polyimide is preferable. As the first bank, acrylic resin, novolac resin, phenol resin, non-photosensitive material, or the like can be used.
[Second bank]
The second bank 106 is formed on the first bank 105. The second bank 106 has a reverse taper and is used to prevent the upper electrode of the adjacent light emitting portion from conducting. After applying the bank forming material, the second bank 106 is formed by developing and exposing using a predetermined photomask. The surface of the second bank 106 on the side where the organic layer is present may be subjected to water repellency treatment. For example, a fluorine gas plasma treatment is performed on the surface of the second bank 106, and the water repellency treatment is performed by fluorinating the surface of the second bank 106. Thereby, a water repellent layer is formed on the surface of the second bank 106. It is preferable to use a negative photoresist as the second bank 106. As the second bank 106, an acrylic resin, a novolac resin, a phenol resin, a non-photosensitive material, or the like can be used.
[Organic layer]
FIG. 2 shows details of the organic layer 104. The organic layer 104 may have a single-layer structure including only the light-emitting layer 203 or a multilayer structure including one or more of the electron injection layer 205, the electron transport layer 204, the hole transport layer 202, and the hole injection layer 201. The electron injection layer 205 and the electron transport layer 204, the electron transport layer 204 and the light emitting layer 203, the light emitting layer 203 and the hole transport layer 202, the hole transport layer 202 and the hole injection layer 201 may be in contact with each other. Other layers described above may be interposed between the two layers. The 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.

Hereinafter, details of each layer included in the organic layer 104 will be described.
[Hole injection layer]
The hole injection layer 201 serves to lower the injection barrier between the anode and the hole transport layer. Therefore, a material having an appropriate ionization potential is desirable for the hole injection layer 201. The hole injection layer 201 preferably has a role of filling the surface irregularities of the underlayer.

Specific examples include, but are not limited to, copper phthalocyanine, starburst amine compounds, polyaniline, polythiophene, vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide.
[Hole transport layer]
The hole transport layer 202 has a role of transporting holes and injecting them into the light emitting layer 203. Therefore, the hole transport layer 202 is preferably made of a hole transport material having high hole mobility. The hole transport layer 202 is desirably chemically stable and has properties such as a low ionization potential, a low electron affinity, and a high glass transition temperature.

  Specifically, 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- Lis [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-TDAB), 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). Of course, it is not limited to these materials, and two or more of these materials may be used in combination.

  The hole transport layer 202 can be used by adding an oxidizing agent to the hole transport material as described above for the purpose of lowering the barrier with the anode or improving electric conductivity.

Specific examples of the oxidizing agent include Lewis acid compounds such as ferric chloride, ammonium chloride, gallium chloride, indium chloride, and antimony pentachloride, and electron accepting compounds such as trinitrofluorene. Of course, it is not limited to these materials, and two or more of these materials may be used in combination.
[Light emitting layer]
The light-emitting layer 203 is a layer that emits light with a wavelength specific to the material by recombination of injected holes and electrons. In the light emitting layer 203, there are a case where the host material itself forming the light emitting layer emits light and a case where a dopant material added in a small amount to the host emits light.

  Specific host materials include distyrylarylene derivatives (DPVBi), silole derivatives having a benzene ring in the skeleton (2PSP), oxodiazole derivatives having a triphenylamine structure at both ends (EM2), and perinone derivatives having a phenanthrene group (P1), oligothiophene derivative (BMA-3T) having a triphenylamine structure at both ends, perylene derivative (tBu-PTC), tris (8-quinolinol) aluminum, polyparaphenylene vinylene derivative, polythiophene derivative, polyparaphenylene derivative , Polysilane derivatives, and polyacetylene derivatives.

Specific dopant materials used for the light-emitting layer 203 include quinacridone, coumarin 6, nile red, rubrene, 4- (dicyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran ( DCM), dicarbazole derivatives, porphyrin platinum complexes (PtOEP), iridium complexes (Ir (ppy) ₃ ). The light emitting layer is not limited to these materials, and two or more of these materials may be used in combination.
[Electron transport layer]
The electron transport layer 204 has a role of transporting electrons and injecting them into the light emitting layer. Therefore, the electron transport layer 204 is preferably made of an electron transport material having a high electron mobility.

  Specifically, tris (8-quinolinol) aluminum, oxadiazole derivatives, silole derivatives, zinc benzothiazole complexes, and bathocuproine (BCP) are desirable.

  In the electron transport layer 204, it is desirable that the electron transport material contains a reducing agent to lower the barrier with respect to the cathode and to improve electrical conductivity.

Specific examples of the reducing agent include alkali metal, alkaline earth metal, alkali metal oxide, alkaline earth oxide, rare earth oxide, alkali metal halide, alkaline earth halide, rare earth halide, alkali metal and aroma. And a complex formed of a group compound.
Particularly preferred alkali metals are Cs, Li, Na and K.
[Electron injection layer]
The electron injection layer 205 is used to improve the efficiency of electron injection from the cathode to the electron transport layer 204. Specifically, the material of the electron injection layer 205 is preferably lithium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, magnesium oxide, or aluminum oxide.
[Reflective electrode]
A reflective electrode 103 formed as a cathode and an electrode for injecting electrons into the organic layer 104, and it is desirable to use a conductive film having a small work function for increasing the electron injection efficiency.

  Specifically, examples of the material of the reflective electrode 103 include an Mg · Ag alloy, an Al·Li alloy, an Al · Ca alloy, and an Al · Mg alloy.

On the other hand, if the above-described electron injection layer 205 is provided on the reflective electrode 103, it is not necessary to use a low work function material as a condition for the reflective electrode 103, and a general metal material can be used. As a material for the reflective electrode in this case, specifically, a metal such as Al, In, Mo, or Ni, an alloy using these metals, polysilicon, or amorphous silicon can be used.
[Light distribution control layer]
A light distribution control layer 206 that controls the distance from the reflective electrode 103 to the light emitting layer 203 is formed by the electron injection layer 205 and the electron transport layer 204 between the light emitting layer 203 and the reflective electrode layer 103. The light distribution control layer 206 may control the above-described distance by either the electron injection layer 205 or the electron transport layer 204, but it is important to select a material having a low resistivity because thickening is necessary. .

  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 thickness 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 optimal optical conditions and the film thickness of the organic film are longer for light emission at longer wavelengths than at shorter wavelengths. The light emitting point described here is defined as the center in the film thickness direction of the light emitting position of each color dopant in the light emitting layer of the organic layer constituting the organic light emitting element.

  FIG. 3 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. 3, the light emission position at which the light extraction efficiency is maximized is different 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). In other words, 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 greater than half the peak value in FIG. For example, the emission position of the green dopant is in the range from 145 nm to 235 nm from the emission center to the reflection electrode, the emission position of the blue dopant 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 dopant 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. 4 shows the relationship between the light extraction efficiencies including non-propagating light of Sample A in which the light emission positions are arranged in the order of red, yellow, and blue from the electrode side and Sample B in the order of blue, yellow, and red from the electrode side. . Here, it is defined that the light extraction efficiency is 100% when the remaining 87% except 13% lost by absorption and plasmon in the reflective electrode can be extracted.

  In the external mode, when the light extraction layer is not provided, Sample A and Sample B are the light extraction efficiency when one light extraction layer is provided. When the light extraction layer is not provided, the light that can be extracted to the outside is about 20% of the total. On the other hand, it can be seen that the light extraction efficiency is improved to about 70% by using the order of the light emitting positions, the control of the light distribution control layer, and the light extraction layer.

By controlling the order of the light emission positions and controlling the light emission position in the vicinity of the center wavelength of the light emission color in this way, the light extraction efficiency is greatly increased. 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. 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. Furthermore, light extraction efficiency of 50% or more can be obtained by setting the light emission position to 170 nm to 225 nm without controlling the light distribution.
[Encapsulation substrate]
The sealing substrate 109 has a role of preventing water and oxygen in the atmosphere from entering the reflective electrode 103 or the organic layer 104 therebelow. The sealing substrate 109 only needs to be light transmissive, and in particular, a substrate that transmits light in the wavelength range of 380 to 780 nm is desirable.

Specifically, as the material of the sealing substrate 109, SiO _2, SiNx, inorganic materials and polychloroprene such as Al ₂ O _3, polyethylene terephthalate, polyoxymethylene, polyvinyl chloride, polyvinylidene fluoride, cyanoethyl pullulan, polymethyl Organic materials such as methacrylate, polysulfone, polycarbonate, and polyimide can be used.
[Reflection layer and auxiliary wiring]
The reflective layer / auxiliary wiring 110 formed in this embodiment is used as a reflective layer that reflects emitted light and extracts light, and is disposed on a line with a width of 1 μm to 20 μm on the transparent electrode 102. Thus, it works to reduce the resistance component of the electrode. The reflective layer / auxiliary wiring 110 is preferably made of a metal or alloy material having a high reflectance and a low resistance value. As such materials, alkali metals, alkali metal halides, alloys of these with other metals, and the like can be used. For example, Ag, Al, Na, Na · K alloy, Li, Mg, Examples include Al, Mg—Ag mixture, Mg—In mixture, Al—Li alloy, Al—Al 2 O 3 mixture, Al—LiF mixture, and the like. The reflective electrode / auxiliary wiring 110 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.
[Light extraction layer (light scattering layer)]
In the organic light emitting device, a light extraction layer (light scattering layer) is often provided for the purpose of extracting light emitted from the light emitting layer with high efficiency. Examples of means for improving the light extraction efficiency include a microlens array structure, a scattering structure, and a diffraction structure. In particular, a light extraction layer in which a transparent resin and inorganic scattering fine particles are combined can be manufactured relatively easily and can be easily developed into a bottom emission type.

Examples of the method for applying the light extraction layer include spin coating, dip coating, die coating, casting, spray coating, and gravure coating. From the viewpoint of film uniformity, spin coating, dip coating, and die coating are particularly preferable. The light extraction layer preferably has a thickness of 2 to 20 μm. When the thickness is less than 2 μm, mixing of the scattering fine particles becomes difficult, and when it exceeds 20 μm, it is difficult to form the coating.
[First light extraction layer]
A first light extraction layer 107 is formed on the substrate 100 for the purpose of extracting light emitted from the light emitting layer 203. The resin constituting the first light extraction layer 107 may have a refractive index of 1.7 or higher, or if the refractive index of the resin is 1.7 or lower, the refractive index is 2 or higher and 2.6 or lower. These nanoparticles may be added to adjust the refractive index to 1.7 or more. As the resin constituting the first light extraction layer 107, a resin in which a part of the structural formula is substituted with chlorine or bromine, a resin containing a heterocyclic ring such as nitrogen or sulfur, or an epoxy resin having a fluorene skeleton is selected. Is preferred.

  In general, the above resins often have a refractive index of 1.6 or higher and a high refractive index.

When the refractive index is less than 1.7 and nanoparticles are added, it is preferable to select one having a particle size of several nm to several tens of nm (preferably 1 nm to 40 nm). Nanoparticles that preferably the refractive index of ZrO _2, rutile TiO _2, BaTiO ₃ chooses two or more inorganic particles, the content is 25～60Vol% on the total amount of the resin and nanoparticle desirable. If it is less than 25 vol%, sufficient high refractive index curing cannot be obtained, and if it exceeds 60 vol%, voids are formed in the film and the film quality is remarkably deteriorated.

As scattering fine particles, high refractive index fine particles such as BaTiO ₃ , ZrO ₂ , rutile TiO ₂ having a particle size of several tens to several μm are added to the transparent resin layer. Since the scattering fine particles are likely to aggregate, a dispersing agent such as a silane coupling agent can be modified on the surface of the scattering fine particles. The addition amount of the scattering fine particles is desirably 5 to 15% by volume. If it is less than 5 vol%, the number of scattering times decreases and sufficient light extraction efficiency cannot be obtained, and if it exceeds 15 vol%, voids easily form between the resin constituting the first light extraction layer 107 and sufficient adhesion. Can't get. The range of the particle size of the scattering fine particles is desirably 100 to 800 nm. It is clear from the simulation that light extraction efficiency can be obtained with high efficiency in this particle size range. When the particle size is less than 100 nm, the particles are very easily aggregated, and when the particle size exceeds 800 nm, the surface irregularities are increased.
[Planarization layer]
In order to smooth the unevenness of the surface of the first light extraction layer 107, a planarization layer 108 can be provided on the first light extraction layer 107. In the organic light emitting device, in order to avoid partial deterioration due to electric field concentration, the surface roughness of the surface of the transparent electrode 102 is required to be Ra ≦ 5 nm. Therefore, the surface roughness of the first light extraction layer 107, which is the base layer of the transparent electrode 102, is also set to Ra ≦ 5 nm. Although the flatness is improved by improving the dispersibility of the scattering fine particles, it is preferable to further improve the flatness by providing the flattening layer 108 on the first light extraction layer 107.

  The resin constituting the planarization layer 108 may be selected from a candidate group of high refractive index resins constituting the light extraction layer. In order to ensure the adhesion between the first light extraction layer 107 and the planarization layer 108, it is necessary that the first light extraction layer 107 does not elute during the planarization. Therefore, a solvent that elutes uncured components of the first light extraction layer 107 cannot be used as the solvent of the planarization layer 108. Since the chemical resistance of the first light extraction layer 107 can be enhanced by cross-linking between molecules, a resin that cross-links between molecules is more preferable. Note that the planarization layer 108 does not have to elute the light extraction layer, and may be a resin that does not cross-link between molecules such as methyl methacrylate resin.

When the resin is laminated, the resin is not completely cured in order to improve the adhesion at the interface, and an uncured component (reactive functional group) may remain. However, the lamination of the resin layer containing an inorganic material such as BaTiO ₃ is difficult to obtain adhesion because it is an interface where an organic material and an inorganic material are mixed. That is, in the case of such an interface of the composite material, the solvent for applying the upper layer resin may dissolve the uncured component of the lower layer resin and reduce the adhesiveness of the interface. In the present invention, by combining the upper layer (planarization layer 108) and the lower layer (first light extraction layer 107) so as not to dissolve each other's resin, good adhesion can be obtained even at an interface where an organic substance and an inorganic substance are mixed. Can do.

  FIG. 5 is a graph showing the relationship between the extraction efficiency of light emitted from the light emitting layer 203 and the refractive index of the planarizing layer 108. Here, a simulation is performed using a model in which light emitted from the light emitting layer 203 is extracted by the planarization layer 108, and it is assumed that the planarization layer 108 is in contact with the air layer. The external mode is light extracted by the air layer, the substrate mode is light extracted by the planarization layer 108, and the thin film mode is light extracted by ITO. According to this, as the refractive index of the planarization layer 108 increases, the light that can be extracted to the planarization layer 108 increases. The refractive index of the resin constituting the light extraction layer (a combination of the light scattering layer and the planarization layer) of the patent document is 1.45 to 1.6, and the extraction efficiency in the planarization layer is 64% at the maximum. . In the present invention, the refractive index of the resin of the planarizing layer is set to 1.7 or more, for the following reason. The white organic light emitting device has a maximum luminous efficiency of 400 lm / W. Since the light emitted from the organic layer 104 is lost by about 10% due to surface plasmon or heat, it is a problem whether the remaining 90% can be extracted efficiently.

  Since the luminous efficiency of the white LED is predicted to be 200 to 250 lm / W in the future, it is necessary to extract light of about 250 lm / W even in the organic light emitting device. In order to achieve this numerical value, it is only necessary to extract 76% or more of light into the planarization layer from the simulation calculation result. As shown in FIG. 5, when the refractive index of the planarization layer 108 is 1.7 or more, the extraction efficiency is obtained. It can be seen that becomes 76% or more.

If the planarization layer 108 has a thickness of 2 to 10 μm, it is considered that sufficient planarization can be obtained. When the thickness is less than 2 μm, a sufficient planarization effect cannot be obtained, and when it exceeds 10 μm, it takes time to cure the planarization layer, and workability is lowered.
[Second light extraction layer]
For the purpose of reducing the total reflection at the air interface and extracting light, the second light extraction layer 101 is formed on the opposite side of the substrate. As the resin constituting the second light extraction layer 101, a highly transparent resin having a refractive index of 1.3 or more and 1.65 or less may be selected. For example, polystyrene, polysulfone, acrylic, fluororesin, epoxy, silicone resin, polyethylene, polypropylene, nylon and the like can be mentioned. The second light extraction layer 101 may contain scattering fine particles having a refractive index of several tens to several μm and a refractive index of 1.3 to 1.8 as a scatterer. Specifically, fine particles such as Al 2 O 3, BaCO 3, MgO, SrCO 3, SiO 2, and CaF 2 may be selected, and the added amount of scattering fine particles is preferably 5 to 15 vol%. The coating method and film thickness range of the second light extraction layer 108 are the same as those of the first light extraction layer.
Example 1
A first light extraction layer 107 having a thickness of about 2 μm was formed on the substrate (non-alkali glass) 101 by spin coating by the following method.

  ZrO2 nanoparticle slurry using methyl ethyl ketone as a solvent (SZR-K manufactured by Sakai Chemical Industry Co., Ltd.), fluorene epoxy resin (CG-500 manufactured by Osaka Gas Chemical Co., Ltd.), phenol novolac curing agent (NV manufactured by Osaka Gas Chemical Co., Ltd.) -203-R) and triphenylphosphine (manufactured by Kanto Chemical Co., Inc.) were mixed to prepare a coating solution. In order to improve the dispersibility of the BaTiO3 scattering fine particles, surface treatment is performed using 3-isocyanatopropyltriethoxysilane (KBE-9007 manufactured by Shin-Etsu Chemical Co., Ltd.), and in addition to the coating solution, the substrate 101 is coated by a spin coat method. Heat cured.

  A triazine ring-containing resin coating solution (UR-501, manufactured by Nissan Chemical Industries, Ltd.) using cyclohexanone as a solvent was applied to the surface of the first light extraction layer 107 formed in this manner on a spin coater, and the thickness was about 2 μm. A planarizing layer 108 was formed and cured by heating.

  When the adhesion after the flattening layer 108 was formed was evaluated by an adhesive tape peeling test, no peeling was observed. The adhesion between the substrate 100 and the first light extraction layer 107 and between the first light extraction layer 107 and the planarization layer 108 was good. When the surface roughness Ra (N = 3) is calculated by performing line analysis on the flatness of the first light extraction layer 107 and the planarization layer 108 from the surface shape measurement result by AFM, Ra of the first light extraction layer 107 is calculated. Was 37.0 nm, and Ra of the planarization layer 108 was 4.58 nm, so that the flatness was greatly improved.

  Next, after patterning the transparent electrode 102 (ITO) with a film thickness of 50 nm by sputtering, Ag was formed as a reflective layer / auxiliary wiring on the transparent electrode 102 by vacuum deposition.

  Further, a first bank 105 made of polyimide and a second bank 106 made of acrylic resin were formed.

Subsequently, the organic layer 104 was formed by the following procedure. 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter referred to as α-NPD) and vanadium pentoxide (V ₂ O ₅ ) were co-deposited by a vacuum deposition method. A first co-deposited film having a thickness of about 50 nm is formed. The vapor deposition rates were determined so that the mixing ratio of α-NPD and V ₂ O ₅ was 1: 1 by molar ratio. This first co-deposited film functions as the hole injection layer 201. An α-NPD film having a film thickness of 50 nm is formed on the hole injection layer 201 by vacuum deposition. The α-NPD film functions as the hole transport layer 202.

On the hole transport layer 202, 4,4′-N, N′-dicarbazole-biphenyl (hereinafter referred to as “CBP”) and bis [2- (2′-benzo [4,5-a] are formed by vacuum deposition. ] Thienyl) pyridinate-N, C3 ′] iridium (acetylacetonate) (hereinafter referred to as “Brp2Ir (acac)”) is co-evaporated to form a second co-deposited film having a thickness of about 40 nm. The second co-deposited film functions as the light emitting layer 203. In the light-emitting layer 203, Brp ₂ Ir (acac) functions as a dopant that determines the emission color. Next, a 60-nm-thick tris (8-quinolinol) aluminum (hereinafter referred to as “Alq ₃ ”) film is formed on the light-emitting layer 203 by vacuum deposition. This Alq ₃ film functions as the electron transport layer 204.

  On the electron transport layer 204, a co-deposited film of Mg and Ag is formed as a buffer layer. The co-deposited film of Mg and Ag has both functions of protecting the underlying organic film and forming the electron injection layer 205 when forming the upper electrode thereon. In this embodiment, the light distribution control layer 206 is formed by controlling the electron transport layer 204. After forming the reflective electrode 103 made of Ag with a film thickness of 150 nm, a sealing substrate 109 made of PEN was attached. Finally, a second light extraction layer 101 was formed on the opposite side of the substrate 100 by the following method.

  A second light extraction layer 101 having a thickness of about 2 μm was formed on the substrate (non-alkali glass) 100 by spin coating by the following method.

  Mix the epoxy dissolved in toluene (made by Hitachi Chemical Co., Ltd.), alicyclic acid anhydride curing agent (made by Hitachi Chemical Co., Ltd.), triphenylphosphine (made by Kanto Chemical Co., Ltd.) Produced. In order to improve the dispersibility of the Al2O3 scattering fine particles, surface treatment is performed using 3-isocyanatopropyltriethoxysilane (KBE-9007 manufactured by Shin-Etsu Chemical Co., Ltd.), and in addition to the above coating solution, the substrate 100 is spin coated. It was applied and heat cured.

  Thus, the bottom emission type organic light emitting device was completed, and the light extraction efficiency was measured and found to be 85%.

Table 1 shows the composition of the first light extraction layer 107, the planarization layer 108, and the second light extraction layer 101 in Examples 2 to 7, the presence / absence of light distribution control, and the evaluation results of the light extraction efficiency. .
(Examples 2 to 7)
In Examples 2 to 7, the resin composition of the first light extraction layer 107 and the second light extraction layer 101, the type of silane coupling agent that modifies the scattering fine particles contained in each light extraction layer, and the light extraction efficiency in the case It shows the result of evaluating. When the light distribution control was performed in all the examples, the light extraction efficiency of 84% or more was obtained in all cases.
(Comparative Example 1)
A first light extraction layer 107 and a planarization layer 108 were formed in the same manner as in Examples 1-7. When the light distribution control was performed, the light extraction efficiency was 78%, which was lower than those of Examples 1 to 7 in which the second light extraction layer 101 was provided.
(Comparative Example 2)
The first light extraction layer 107, the planarization layer 108, and the second light extraction layer 101 were formed in the same manner as in Examples 1-7. When light distribution control was not performed, the light extraction efficiency was 74%, which was a lower value than when light distribution control was performed.
(Comparative Example 3)
A first light extraction layer 107 and a planarization layer 108 were formed in the same manner as in Examples 1-7. When light distribution control was not performed, the light extraction efficiency was 68%, which was a lower value than when light distribution control was performed or when the second light extraction layer 101 was formed.
(Supplement)
In Example 1, the fluorene-containing epoxy resin is an epoxy resin having a fluorene skeleton, and the triazine ring-containing resin is a resin having a nitrogen heterocycle. The scattering fine particles are surface-treated with B: 3-isocyanatopropyltriethoxysilane.

  In Example 2, the fluorene-containing epoxy resin is an epoxy resin having a fluorene skeleton, and the triazine ring-containing resin is a resin having a nitrogen heterocycle. The scattering fine particles are surface-treated with C: 3-glycidpropyltriethoxysilane.

  In Example 3, the fluorene-containing epoxy resin is an epoxy resin having a fluorene skeleton, and the triazine ring-containing resin is a resin having a nitrogen heterocycle. The scattering fine particles are surface-treated with D: 3-aminopropyltrimethoxysilane.

  In Example 4, the fluorene-based epoxy resin is an epoxy resin having a fluorene skeleton, and the thiourethane resin is a resin in which a part of the repeating unit of the structural formula is substituted with sulfur. The scattering fine particles are surface-treated with D: 3-aminopropyltrimethoxysilane.

  In Example 5, the episulfide resin is a resin having a sulfur heterocycle, and the triazine ring-containing resin is a resin having a nitrogen heterocycle. The scattering fine particles are surface-treated with B: 3-isocyanatopropyltriethoxysilane.

  In Example 6, the polymetal methyl methacrylate resin is a methyl methacrylate resin, and the thiourethane is a resin in which a part of the repeating unit of the structural formula is substituted with sulfur. The scattering fine particles are surface-treated with D: 3-aminopropyltrimethoxysilane.

  In Example 7, S-containing vinyl chloride is a resin in which a part of the repeating unit of the structural formula is substituted with sulfur, and the episulfide resin is a resin having a sulfur heterocycle. The scattering fine particles are surface-treated with C: 3-glycidpropyltriethoxysilane.

  As described above, in Examples 1 to 7, the first light extraction layer 107 and the planarization layer 108 are made of different resins. These resins are in a relationship that does not dissolve one of the resins. Although not all examples are given here, as long as none of the resins dissolves one of the resins, the resin of the first light extraction layer 107 is partially substituted with chlorine, bromine or sulfur in the structural formula. Selected from resins having a heterocyclic ring of nitrogen or sulfur, and epoxy resins having a fluorene skeleton. The resin of the planarization layer 108 is a resin in which a part of the repeating unit of the structural formula is substituted with chlorine, bromine or sulfur, a resin having a nitrogen or sulfur heterocycle, an epoxy resin having a fluorene skeleton, or a methyl methacrylate resin. Can be selected and used.

  DESCRIPTION OF SYMBOLS 100 ... Substrate, 101 ... Second light extraction layer, 102 ... Transparent electrode, 103 ... Reflective electrode, 104 ... Organic layer, 105 ... First bank, 106 ... Second bank, 107 ... First light extraction layer , 108 ... planarization layer, 109 ... sealing substrate, 110 ... reflective layer / auxiliary wiring, 201 ... hole injection layer, 202 ... hole transport layer, 203 ... light emitting layer, 204 ... electron transport layer, 205 ... electron injection Layer, 206 ... Light distribution control layer

Claims (17)

An organic light-emitting device in which a second light extraction layer, a substrate, a first light extraction layer, a planarization layer, a first electrode, an organic layer, and a second electrode are provided in order,
The organic layer includes a light emitting layer,
The first light extraction layer and the second light extraction layer include scattering fine particles,
With respect to the light emitting point indicating the center in the film thickness direction of the light emitting position of the dopant in the light emitting layer, it is arranged in the order of blue, green, red from the second electrode side,
An organic light-emitting element, wherein a length from the green light emitting point to the second electrode is in a range of 145 nm to 235 nm. The organic light emitting device according to claim 1,
The organic light-emitting element, wherein a length from the blue light emitting point to the second electrode is in a range of 130 nm to 200 nm. The organic light emitting device according to claim 1 or 2,
The organic light-emitting element, wherein a length from the red light emitting point to the second electrode is in a range of 170 nm to 275 nm. The organic light emitting device according to any one of claims 1 to 3,
The organic light-emitting device, wherein the scattering fine particles are surface-treated with a dispersant. The organic light emitting device according to claim 1,
The refractive index of the first light extraction layer is 1.7 or more,
The organic light emitting device, wherein the second light extraction layer has a refractive index lower than that of the first light extraction layer. The organic light emitting device according to claim 5,
The refractive index of the resin contained in the first light extraction layer is 1.7 or less,
The organic light-emitting device, wherein the scattering fine particles contained in the first light extraction layer have a refractive index of 2 or more and 2.6 or less. The organic light emitting device according to claim 5,
The refractive index of the resin contained in the second light extraction layer is 1.3 or more and 1.65 or less,
The organic light-emitting device, wherein the scattering fine particles contained in the second light extraction layer have a refractive index of 1.3 or more and 1.8 or less. The organic light emitting device according to any one of claims 1 to 7,
The organic light-emitting device, wherein an average particle diameter of the scattering fine particles contained in the first light extraction layer and the second light extraction layer is 100 to 800 nm. The organic light emitting device according to any one of claims 1 to 8,
The type of the scattering fine particles is BaTiO3 or rutile TiO2 in the first light extraction layer, and Al2O3, BaCO3, MgO, SrCO3, SiO2, CaF2 in the second light extraction layer. . The organic light emitting device according to any one of claims 1 to 9,
The organic light-emitting device, wherein the scattering fine particles are included in the light extraction layer in an amount of 5 to 15 vol%. The organic light emitting device according to any one of claims 1 to 10,
The organic light-emitting device, wherein the light extraction layer or the planarization layer includes nanoparticles having a refractive index of 2 or more and a particle size of 1 to 40 nm. The organic light emitting device according to claim 11,
An organic light emitting device, wherein the planarization layer has a thickness of 2 to 10 μm. The organic light emitting device according to claim 11,
The organic light emitting device, wherein the nanoparticles are contained in an amount of 25 to 60 vol% in the light extraction layer or the planarization layer. The organic light emitting device according to any one of claims 1 to 13,
The first light extraction layer includes a first high refractive index resin,
The planarizing layer includes a second high refractive index resin,
The organic light-emitting element, wherein the first high-refractive index resin and the second high-refractive index resin are in a relationship that does not dissolve one of the resins. The organic light emitting device according to claim 14,
An organic light-emitting device, wherein a difference between an SP value indicating a solubility parameter of the first high refractive index resin and an SP value indicating a solubility parameter of the second high refractive index resin is 1 or more. The organic light emitting device according to claim 14,
The first high refractive index resin is any one of a resin in which a part of the repeating unit of the structural formula is substituted with chlorine, bromine or sulfur, a resin having a nitrogen or sulfur heterocyclic ring, or an epoxy resin having a fluorene skeleton. An organic light-emitting element characterized by the above. The organic light emitting device according to claim 14,
The second high refractive index resin includes a resin in which a part of the repeating unit of the structural formula is substituted with chlorine, bromine or sulfur, a resin having a nitrogen or sulfur heterocyclic ring, an epoxy resin having a fluorene skeleton, methacrylic acid An organic light-emitting element characterized by being one of methyl resins.

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