Organic light-emitting element

Abstract

To improve the light-emitting characteristics and the driving durability characteristics of an organic light-emitting element having two light-emitting layers.SOLUTION: In the organic light-emitting element having a first light-emitting layer formed of a first organic compound, a first light-emitting material, and a second light-emitting material and having a second light-emitting layer formed of a second organic compound and a third light-emitting material, the difference between the HOMO level of the first light-emitting material and the first organic compound of the first light-emitting layer is made smaller than that of the LUMO level of the second organic compound and the third light-emitting material of the second light-emitting layer and the content of the light-emitting material of the first light-emitting layer is made smaller so that the hole trap capability of the first light-emitting layer is reduced and the re-combination region of holes and electrons is made distant from the electrode side of the first light-emitting layer and is also localized in the light-emitting layer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an organic light-emitting element and various devices and apparatuses having the organic light-emitting element. [Background technology]

[0002] An organic light-emitting element (sometimes called an "organic electroluminescence element" or "organic EL element") has an anode, a cathode, and an organic compound layer including a light-emitting layer disposed between these electrodes, and emits light by passing an electric current through the organic compound layer. Compared to conventional display devices, organic light-emitting elements are used in various display devices due to their characteristics of high freedom in shape, light weight, and high color rendering. As one of the techniques, a full-color display using organic light-emitting elements is known. The method includes a method in which a light-emitting layer is made separately for each pixel (element) to emit a different light color, and a method in which a white-emitting light-emitting layer is used and a color filter is used to extract a different light-emitting color for each pixel. For the white light-emitting layer, it is known to use two or more types of light-emitting materials and two or more light-emitting layers. In recent years, in order to expand the scope of application products, active development has been carried out, and there is a particular demand for technology to improve the driving durability of white organic light-emitting devices. Patent Document 1 describes an organic light-emitting element in which two light-emitting layers are stacked, with the light-emitting layer on the cathode side having 0.6% by mass of a blue-emitting dopant and the light-emitting layer on the anode side having a red-emitting dopant and 2.0% by mass of a green-emitting dopant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-186521 A Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes the configuration of a white organic light-emitting element having blue, green, and red light-emitting dopants, but there is room for improvement in the concentration of the light-emitting dopants and the resulting charge balance in the light-emitting layer. In view of the above problems, the present invention aims to improve the light emitting characteristics and driving durability characteristics of an organic light emitting device having two light emitting layers. [Means for solving the problem]

[0005] A first organic light-emitting device of the present invention has a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, in this order. The first light-emitting layer has a first organic compound, a first light-emitting material, and a second light-emitting material, and the second light-emitting layer has a second organic compound and a third light-emitting material. The first organic light-emitting device is characterized in that it satisfies the following formulas [1] to [4]. [1] HOMOd2-HOMOh1 <LUMOh2-LUMOd3 [2] Content of first luminescent material < Content of second luminescent material [3] The content of the first luminescent material < the content of the third luminescent material [4] Content of second luminescent material < 2.0% by mass HOMOh1: HOMO level of the first organic compound HOMOd2: HOMO level of the second emitting material LUMOh2: LUMO levels of second organic compounds LUMOd3: LUMO level of the third emitting material The second organic light-emitting device of the present invention has a first electrode, a first light-emitting layer, a second light-emitting layer, an adjacent layer, and a second electrode, in this order. The first light-emitting layer has a first organic compound, a first light-emitting material, and a second light-emitting material. The second light-emitting layer has a second organic compound and a third light-emitting material. The adjacent layer is made of an organic compound composed of a hydrocarbon, and is characterized in that it satisfies the following formula [4]: [4] Content of second luminescent material < 2.0% by mass Effect of the Invention

[0006] According to the present invention, in an organic light-emitting device having two or more light-emitting layers, the light-emitting characteristics and driving durability can be improved. [Brief description of the drawings]

[0007] [Figure 1] 1A is a schematic cross-sectional view showing an example of a pixel of a display device according to one embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view showing an example of a display device using an organic light-emitting element according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram illustrating an example of a display device according to an embodiment of the present invention. [Diagram 3] 1A is a schematic diagram of an imaging device according to an embodiment of the present invention, and FIG. [Figure 4] 1A is a schematic diagram of a display device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of a foldable display device according to an embodiment of the present invention. [Diagram 5] 1A is a schematic diagram of an illumination device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of an automobile having a vehicle lamp according to an embodiment of the present invention. [Figure 6] 1A is a schematic diagram of a wearable device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of an example of a wearable device according to an embodiment of the present invention, showing a form having an imaging device. [Figure 7] 1A is a schematic diagram of an image forming apparatus according to one embodiment of the present invention, and FIG. 1B and FIG. 1C are schematic diagrams showing an embodiment in which a plurality of light-emitting units of an exposure light source are arranged on a long substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The first organic light-emitting device of the present invention has a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, in this order. The first light-emitting layer has a first organic compound, a first light-emitting material, and a second light-emitting material, and the second light-emitting layer has the second organic compound and a third light-emitting material. The first light-emitting layer is characterized by satisfying the following formulas [1] to [4]: [1] HOMOd2-HOMOh1 <LUMOh2-LUMOd3 [2] Content of first luminescent material < Content of second luminescent material [3] The content of the first luminescent material < the content of the third luminescent material [4] Content of second luminescent material < 2.0% by mass HOMOh1: HOMO level of the first organic compound HOMOd2: HOMO level of the second emitting material LUMOh2: LUMO levels of second organic compounds LUMOd3: LUMO level of the third emitting material

[0009] The features of the light-emitting layer of the organic light-emitting device of the present invention will be described below. In order to improve the light-emitting properties and driving durability of the organic light-emitting device, it is necessary that the injected holes and electrons are both confined in the light-emitting layer and recombined efficiently. In other words, it is necessary to prevent the holes in the light-emitting layer from leaking to the layer on the cathode side and the electrons in the light-emitting layer from leaking to the layer on the anode side. In addition, it is preferable for the charge recombination region to be delocalized in the light-emitting layer in order to improve durability. This is because the excitation load per molecule is reduced and deterioration from the excited state is suppressed.

[0010] In order to confine holes and electrons in the light-emitting layer, it is effective to provide an electron blocking layer on the anode side of the light-emitting layer and a hole blocking layer on the cathode side. As a constituent material of the electron blocking layer, an arylamine derivative having a nitrogen-containing skeleton with high electron donating properties can be mentioned. Although such a derivative has a high hole transporting ability, the stability of the radical anion is low. Therefore, it has been found that the durability of the organic light-emitting element can be improved by moving the recombination region away from the interface between the light-emitting layer and the electron blocking layer and suppressing the transport of electrons or the excitation due to recombination at the interface.

[0011] Therefore, in the present invention, the first light-emitting layer efficiently traps holes, and the second light-emitting layer efficiently traps electrons, thereby confining charges in both light-emitting layers and delocalizing the recombination region. Furthermore, by reducing the content of the light-emitting material in the first light-emitting layer, the hole trapping ability of the first light-emitting layer is alleviated, and the recombination region is moved away from the interface of the first light-emitting layer on the first electrode side, so that even if a layer having an arylamine derivative, such as an electron blocking layer or a hole injection layer, is provided on the first electrode side of the first light-emitting layer, the deterioration of these layers is suppressed. Thus, the durability of the organic light-emitting device is improved.

[0012] The formula [1], which is a feature of the present invention, indicates that the hole trapping ability of the first light-emitting layer is lower than the electron trapping ability of the second light-emitting layer. The HOMO level of the light-emitting material of the light-emitting layer is shallower (closer to vacuum) than the HOMO level of the host material, but the larger the difference between them, the higher the hole trapping ability of the light-emitting layer. The LUMO level of the light-emitting material of the light-emitting layer is deeper (farther from vacuum) than the LUMO level of the host material, but the larger the difference between them, the higher the electron trapping ability of the light-emitting layer. Therefore, by making the difference between the HOMO levels of the second light-emitting material and the first organic compound of the first light-emitting layer smaller than the difference between the LUMO levels of the third light-emitting material and the second organic compound of the second light-emitting layer, the hole trapping ability of the first light-emitting layer becomes lower than the electron trapping ability of the second light-emitting layer. That is, if the first electrode on the first light-emitting layer side is made an anode, the recombination region is farther away from the first electrode side of the first light-emitting layer.

[0013] Incidentally, HOMO means the highest occupied molecular orbital, and LUMO means the lowest unoccupied molecular orbital. The energy level of HOMO is sometimes called "HOMO" or "HOMO level", and the energy level of LUMO is sometimes called "LUMO" or "LUMO level".

[0014] Moreover, formulas [2] to [4], which are features of the present invention, indicate that the content of the light-emitting material in the first light-emitting layer is small. Specifically, as shown in formulas [2] and [3], the content of the first light-emitting material is smaller than the second light-emitting material and the third light-emitting material, and further, as shown in formula [4], the content of the second light-emitting material is suppressed to a low level of less than 2.0 mass%. Therefore, the hole trapping ability of the first light-emitting layer is suppressed to be lower than the electron trapping ability of the second light-emitting layer, and the recombination region is closer to the second light-emitting layer.

[0015] Furthermore, preferred conditions in the present invention will be described. In the present invention, by setting the content of the third light-emitting material in the second light-emitting layer to be 1.0 mass % or more, the electron trapping performance of the second light-emitting layer is improved, and the recombination region can be located closer to the second light-emitting layer and farther from the interface of the first light-emitting layer on the first electrode side, which is preferable.

[0016] The first light-emitting material is preferably red light-emitting, and the content of the first light-emitting material in the first light-emitting layer is preferably less than 0.3% by mass, more preferably less than 0.2% by mass. By reducing the content of the first light-emitting material, the loss of excitons due to the loss of concentration is suppressed, and the luminous efficiency is improved, which is preferable. When the first light-emitting material is red light-emitting, one of the second light-emitting material and the third light-emitting material can be made to emit blue light and the other can be made to emit green light to form an organic light-emitting device that emits white light, but the present invention is not necessarily limited to such a configuration.

[0017] Regarding the thickness of the light-emitting layers, it is preferable that the first light-emitting layer is thicker than the second light-emitting layer, because, as described above, in order to place the recombination region closer to the second light-emitting layer and to delocalize the recombination region, it is effective to make the first light-emitting layer thicker by the amount of the recombination region being moved away from the interface of the first light-emitting layer on the first electrode side.

[0018] It is preferable that the first organic compound and the second organic compound are the same organic compound, because it is preferable for the delocalization of the recombination region that no energy barrier is formed between the first emitting layer and the second emitting layer.

[0019] The first light-emitting material, the second light-emitting material, and the third light-emitting material are not particularly limited as long as the energy relationship of the above formula [1] is satisfied, but it is preferable that they have a fluoranthene skeleton. The fluoranthene skeleton is an electron-deficient system, so the LUMO level is deep. Therefore, it is suitable for the organic light-emitting device of the present invention. Below, examples of the light-emitting material according to the present invention are shown, but of course, they are not limited to these. The following R-1 to R-27 are specific examples of the first light-emitting material, G-1 to G-24 are specific examples of the second light-emitting material, and B-1 to B-62 are specific examples of the third light-emitting material. In the present invention, it is preferable to use a red light-emitting material as the first light-emitting material, a green light-emitting material as the second light-emitting material, and a blue light-emitting material as the third light-emitting material.

[0020] [ka]

[0021] [ka]

[0022] [ka]

[0023] [ka]

[0024] [ka]

[0025] The first organic compound and the second organic compound are not particularly limited as long as they satisfy the energy relationship of the above formula [1], but preferably have a pyrene skeleton. The pyrene skeleton is preferred because it has high planarity and is advantageous for adjusting the transport of charges, and also has an energy level applicable to all of blue, green, and red light-emitting materials.

[0026] In addition, it is preferable that all of the freely rotatable single bonds in both the first organic compound and the second organic compound are carbon-carbon bonds, and further, at least one carbon of the carbon-carbon bonds is sp 2 Carbon is preferred for its good durability properties.

[0027] The light-emitting layer usually has a host material and a light-emitting dopant material, and the first organic compound and the second organic compound according to the present invention are host materials, and the first light-emitting material, the second light-emitting material, and the third light-emitting material are light-emitting dopant materials. The host material is a compound having the largest mass ratio among the compounds constituting the light-emitting layer. The light-emitting dopant is a compound having a smaller mass ratio than the host material among the compounds constituting the light-emitting layer, and is a compound that is responsible for the main emission of light. The light-emitting layer may also contain an assist material in addition to the host material and the light-emitting dopant material. The assist material is a compound having a smaller mass ratio than the host material and a larger mass ratio than the light-emitting dopant material among the compounds constituting the light-emitting layer. That is, the mass ratio is host material>assist material>light-emitting dopant material. The light-emitting dopant material is also called a guest.

[0028] The contents of the first light-emitting material and the second light-emitting material in the first light-emitting layer and the third light-emitting material in the second light-emitting layer according to the present invention may satisfy the above-mentioned formulas [2] to [4].

[0029] The light-emitting material may be uniformly contained throughout the first or second light-emitting layer in which the first or second organic compound forms a matrix, or may be contained with a concentration gradient, within the range in which the effects of the present invention can be obtained. The light-emitting material may also be partially contained in a specific region within the layer, so that the light-emitting layer has a region containing only the host and no light-emitting material.

[0030] For the first light-emitting layer, the second light-emitting layer, or the third light-emitting layer that is provided as needed according to the present invention, materials other than the first organic compound, the second organic compound, the first light-emitting material, the second light-emitting material, and the third light-emitting material described above can also be used as long as the effects of the present invention can be obtained.

[0031] In addition to the above-mentioned light-emitting materials, examples of light-emitting materials mainly involved in the light-emitting function include condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, rubrene, etc.), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylenevinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives. Specific examples of compounds used as light-emitting materials are shown below, but are not limited to these.

[0032] [ka]

[0033] [ka]

[0034] The first light-emitting layer and the second light-emitting layer may contain a third organic compound other than the first organic compound and the second organic compound as a host material or an assist material. Examples of the third organic compound include, but are not limited to, aromatic hydrocarbon compounds or derivatives thereof, carbazole derivatives, azine derivatives, xanthone derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organic aluminum complexes such as tris(8-quinolinolato)aluminum, and organic beryllium complexes. Specific examples are shown below.

[0035] [ka]

[0036] The organic light-emitting device of the present invention comprises a first electrode, a second electrode, and an organic compound layer between the first electrode and the second electrode, and the organic compound layer comprises at least a first light-emitting layer and a second light-emitting layer. In the present invention, a functional layer may be appropriately provided between the first electrode and the first light-emitting layer, and between the second light-emitting layer and the second electrode. Examples of the functional layer include a hole injection layer, a hole transport layer, an electron blocking layer, a hole / exciton blocking layer, an electron transport layer, and an electron injection layer, in addition to the light-emitting layer. The organic light-emitting device may also have a light-emitting layer other than the first light-emitting layer and the second light-emitting layer of the present invention.

[0037] In the present invention, it is preferable that the second light-emitting layer has an adjacent layer adjacent to the cathode side, and that the adjacent layer is made of an organic compound comprising a hydrocarbon. The reason for this will be explained below. As described above, the recombination region of the organic light-emitting layer of the present invention is characterized by being closer to the second light-emitting layer. Therefore, the adjacent layer adjacent to the second light-emitting layer is in a region where there are many charges and excitons, and the organic compound is likely to deteriorate. Therefore, the adjacent layer according to the present invention is preferably an organic compound having high bonding stability and chemical stability and made of a hydrocarbon. For example, the above-mentioned compounds EM1 to EM12 and EM16 to EM27 can be mentioned, but the present invention is not limited to these as long as the compound is made of a hydrocarbon.

[0038] In addition, the organic compound made of hydrocarbon preferably has a condensed polycyclic skeleton with four or more rings. This is because the number of condensed rings is large, and the following effects are obtained. The first is that the band gap is small, and the voltage in the organic light-emitting device is reduced. The second is that the thermal stability, such as the glass transition temperature, is improved. The third is that the electron mobility is improved by increasing the planarity, and the voltage in the organic light-emitting device is reduced.

[0039] In addition, all organic compounds made of hydrocarbons are sp 2 It is preferably made of sp 3 sp between carbons 2 This is because the bond energy between carbon atoms is higher, resulting in a molecular structure with higher bond stability.

[0040] A second organic light-emitting device of the present invention has a first electrode, a first light-emitting layer, a second light-emitting layer, an adjacent layer, and a second electrode, in this order. The first light-emitting layer has a first organic compound, a first light-emitting material, and a second light-emitting material. The second light-emitting layer has a second organic compound and a third light-emitting material. The adjacent layer is made of an organic compound composed of a hydrocarbon, and is characterized in that the following formula [4] is satisfied: [4] Content of second luminescent material < 2.0% by mass

[0041] The present inventors have found that in the organic light-emitting device of the present invention, the content of the second light-emitting material is preferably less than 2.0% by mass. This is due to the following two reasons. First, when the second light-emitting material of the present invention is 2.0% by mass or more, concentration quenching occurs, so that it is preferable that the content is less than 2.0% by mass, since it is highly efficient. More preferably, the second light-emitting material is an organic compound composed of a hydrocarbon. When composed only of a hydrocarbon, the planarity is high and concentration quenching becomes more prominent. Second, by suppressing the content of the second light-emitting material to a low level of less than 2.0% by mass, the hole trapping ability of the first light-emitting layer is suppressed, and the recombination region is closer to the second light-emitting layer side. As a result, the recombination region also reaches the interface between the second light-emitting layer and the adjacent layer. Therefore, the structural stability of the adjacent layer affects the characteristics. In other words, it is preferable that the organic compound constituting the adjacent layer is composed of a hydrocarbon having high bond stability. Due to the above two factors, a light-emitting layer structure that can achieve both high efficiency and high durability has been discovered.

[0042] A charge generation layer may also be provided between the first light-emitting layer and the first electrode, and between the second light-emitting layer and the second electrode. The charge generation layer exerts the function of a tandem element, and the electrons generated from the charge generation layer and the holes injected from the first electrode recombine to generate excitons, and the holes generated from the charge generation layer and the electrons injected from the second electrode recombine to generate excitons. This doubles the internal quantum efficiency. Film formation is also performed by vapor deposition or coating.

[0043] A specific device configuration of the organic light-emitting device of this embodiment may be a multi-layer device configuration in which electrode layers and organic compound layers as shown in (1) to (6) below are sequentially laminated on a substrate. In any device configuration, the organic compound layer necessarily includes a light-emitting layer having a light-emitting material. In the following, the "light-emitting layer" includes the first light-emitting layer and the second light-emitting layer according to the present invention, with the anode side being the first light-emitting layer and the cathode side being the second light-emitting layer. (1) Anode / light-emitting layer / cathode (2) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (4) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (5) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) Anode / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode However, these device configuration examples are merely very basic device configurations, and are not limited to these. For example, various layer configurations can be adopted, such as providing an insulating layer, an adhesive layer, or an interference layer at the interface between the electrode and the organic compound layer, or forming the electron transport layer or the hole transport layer from two layers having different ionization potentials.

[0044] Among the device configurations shown in (1) to (6) above, the configuration (6) is preferred because it has both an electron blocking layer and a hole blocking layer. In other words, the configuration (6) having an electron blocking layer and a hole blocking layer can reliably confine both hole and electron carriers within the light-emitting layer, resulting in an organic light-emitting device with no carrier leakage and high light-emitting efficiency.

[0045] The compounds of the electron blocking layer and the hole blocking layer in contact with the light emitting layer preferably have a stable structure. For example, since the hole blocking layer needs to be stable against holes, the hole blocking layer compound is preferably an organic compound with low reactivity, and more preferably an organic compound consisting only of hydrocarbons. Since the electron blocking layer also needs to be stable against electrons, it is preferably an organic compound with low reactivity, and more preferably an organic compound in which all the freely rotatable single bonds are carbon-carbon bonds, preferably sp 2 Carbon-sp 2 It is preferably an organic compound consisting of carbon bonds.

[0046] The mode of extraction (element form) of the light output from the light emitting layer may be a so-called bottom emission type in which light is extracted from the electrode on the substrate side, or a so-called top emission type in which light is extracted from the opposite side of the substrate. Also, a double-sided extraction type in which light is extracted from the substrate side and the opposite side of the substrate can be adopted.

[0047] The organic compound layer is mainly composed of an organic compound, but may contain inorganic atoms or compounds, such as copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, zinc, or the like.

[0048] The organic compound layer can be formed by dry processes such as vacuum deposition, ionization deposition, sputtering, plasma, etc. Alternatively to the dry process, a wet process can be used in which the organic compound is dissolved in a suitable solvent and a layer is formed by a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.). Here, when the layer is formed by a vacuum deposition method or a solution coating method, crystallization is unlikely to occur and the layer has excellent stability over time. When the layer is formed by a coating method, the layer can be formed by combining with a suitable binder resin.

[0049] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin. These binder resins may be used alone or in combination as homopolymers or copolymers, and may further include known additives such as plasticizers, antioxidants, and ultraviolet absorbers, if necessary.

[0050] In the present invention, in layers other than the light-emitting layer, conventionally known low-molecular-weight and high-molecular-weight hole-injecting or hole-transporting compounds, electron-injecting or electron-transporting compounds, etc. may be used as necessary. Specific examples of these compounds are given below.

[0051] As the hole injection transport material, a material having a high hole mobility is preferable so that the injection of holes from the anode can be easily performed and the injected holes can be transported to the light emitting layer. In addition, a material having a high glass transition temperature is preferable so as to suppress deterioration of the film quality such as crystallization in the organic light emitting element. Examples of low molecular weight and polymeric materials having hole injection transport performance include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Furthermore, the above hole injection transport material is also preferably used in the electron blocking layer. Specific examples of compounds used as the hole injection transport material are shown below, but are not limited to these.

[0052] [ka]

[0053] The electron transporting material can be arbitrarily selected from those capable of transporting electrons injected from the cathode to the light-emitting layer, and is selected in consideration of the balance with the hole mobility of the hole transporting material. Examples of materials having electron transporting properties include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organic aluminum complexes, and condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, chrysene derivatives, anthracene derivatives, etc.). Furthermore, the above electron transporting materials are also preferably used in the hole blocking layer. Specific examples of compounds used as electron transporting materials are shown below, but are of course not limited to these. Specific examples are shown below.

[0054] [ka]

[0055] The electron injection material can be selected from those that can easily inject electrons from the cathode, and is selected in consideration of the balance with hole injection properties. Organic compounds include n-type dopants and reducing dopants. For example, compounds containing alkali metals such as lithium fluoride, lithium complexes such as lithium quinolinol, benzimidazolidene derivatives, imidazolidene derivatives, fulvalene derivatives, and acridine derivatives can be mentioned. They can also be used in combination with the above electron transport materials.

[0056] [Other configurations of organic light-emitting element] An organic light-emitting element is usually provided by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode on a substrate. A protective layer, a color filter, a microlens, etc. may be provided on the second electrode. When a color filter is provided, a planarizing layer may be provided between the protective layer. The planarizing layer may be made of acrylic resin, etc. The same applies when a planarizing layer is provided between the color filter and the microlens. A preferred configuration of the organic light-emitting device of the present invention other than the organic compound layer will be described below.

[0057] [substrate] The organic light-emitting element of the present invention may be formed on a substrate, and examples of the substrate include quartz, glass, silicon wafer, resin, and metal. In addition, the substrate may be provided with switching elements such as transistors and wiring, and an insulating layer may be provided thereon. As the insulating layer, any material can be used as long as it can form a contact hole so that wiring can be formed between the first electrode and the insulating layer, and can ensure insulation from wiring that is not connected. For example, resins such as polyimide, silicon oxide, silicon nitride, etc. can be used.

[0058] [electrode] In the present invention, one of the first electrode and the second electrode is an anode, and the other is a cathode. When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode with the higher potential is the anode, and the electrode with the lower potential is the cathode. It can also be said that the electrode that supplies holes to the light-emitting layer is the anode, and the electrode that supplies electrons is the cathode.

[0059] The material constituting the anode should have as large a work function as possible. For example, metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, tungsten, etc., mixtures containing these metals, alloys combining these metals, metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide can be used. Conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used. These electrode materials may be used alone or in combination of two or more kinds. The anode may be composed of one layer or multiple layers.

[0060] When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys or laminates thereof can be used. The above materials can also function as a reflective film without serving as an electrode. When used as a transparent electrode, a transparent conductive layer of oxide such as indium tin oxide (ITO) or indium zinc oxide can be used, but is not limited to these. Photolithography technology can be used to form the electrode.

[0061] On the other hand, the material for the cathode should have a small work function. Examples of the material include alkali metals such as lithium, alkaline earth metals such as calcium, aluminum, titanium, manganese, silver, lead, chromium, and other metals or mixtures containing these metals. Alternatively, alloys combining these metals can be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, zinc-silver, and the like can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials may be used alone or in combination of two or more types. The cathode may have a single layer structure or a multi-layer structure. Among these, it is preferable to use silver, and it is even more preferable to use a silver alloy to reduce the aggregation of silver. As long as the aggregation of silver can be reduced, the ratio of the alloy is not important. For example, the ratio of silver to other metals may be 1:1, 3:1, and the like.

[0062] The cathode may be a top-emission element using an oxide conductive layer such as ITO, or a bottom-emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. The method for forming the cathode is not particularly limited, but it is more preferable to use a direct current or alternating current sputtering method, etc., since the film coverage is good and the resistance can be easily reduced.

[0063] [Protective layer] A protective layer may be provided on the second electrode. For example, by bonding glass provided with a moisture absorbent on the second electrode, it is possible to reduce the intrusion of water and the like into the organic compound layer and reduce the occurrence of display defects. In another embodiment, a passivation film such as silicon nitride may be provided on the second electrode to reduce the intrusion of water and the like into the organic compound layer. For example, after the second electrode is formed, it may be transported to another chamber without breaking the vacuum, and a silicon nitride film having a thickness of 2 μm may be formed by the CVD method to serve as a protective layer. A protective layer may be provided using the atomic deposition method (ALD method) after the film is formed by the CVD method. The material of the film formed by the ALD method is not limited, and may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed by the CVD method on the film formed by the ALD method. The film formed by the ALD method may have a smaller thickness than the film formed by the CVD method. Specifically, it may be 50% or less, or even 10% or less.

[0064] [Color Filter] A color filter may be provided on the protective layer. For example, a color filter taking into consideration the size of the organic light-emitting element may be provided on another substrate, and the substrate on which the organic light-emitting element is provided may be bonded to the color filter. Alternatively, a color filter may be patterned on the protective layer described above using a photolithography technique. The color filter may be made of a polymer.

[0065] [Planarization layer] A planarization layer may be provided between the color filter and the protective layer. The planarization layer is provided for the purpose of reducing the unevenness of the layer below. It may also be called a material resin layer without limiting the purpose. The planarization layer may be composed of an organic compound, and may be a low molecular weight or a high molecular weight, but is preferably a high molecular weight. The planarization layer may be provided above and below the color filter, and may be made of the same or different materials.Specific examples of the materials include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0066] [Microlens] The organic light-emitting element or the light-emitting device having the organic light-emitting element may have an optical member such as a microlens on the light-emitting side. The microlens may be made of acrylic resin, epoxy resin, or the like. The microlens may be intended to increase the amount of light extracted from the organic light-emitting element or the light-emitting device, or to control the direction of the extracted light. The microlens may have a hemispherical shape. When the microlens has a hemispherical shape, among the tangents to the hemisphere, there is a tangent that is parallel to the insulating layer, and the tangent and the hemisphere are the vertices of the microlens. The vertex of the microlens can be determined in the same manner in any cross-sectional view. That is, among the tangents to the semicircle of the microlens in the cross-sectional view, there is a tangent that is parallel to the insulating layer, and the tangent and the semicircle are the vertices of the microlens. It is also possible to define the midpoint of the microlens. In the cross section of the microlens, a line segment is imaginary from a point where an arc shape ends to a point where another arc shape ends, and the midpoint of the line segment can be called the midpoint of the microlens. The cross section for determining the vertex and midpoint may be a cross section perpendicular to the insulating layer.

[0067] [Opposite substrate] A counter substrate may be provided on the planarization layer. The counter substrate is called a counter substrate because it is provided at a position corresponding to the aforementioned substrate. The material of the counter substrate may be the same as that of the aforementioned substrate. When the aforementioned substrate is the first substrate, the counter substrate may be the second substrate.

[0068] [Pixel circuit] The light-emitting device having the organic light-emitting element may have a pixel circuit connected to the organic light-emitting element. The pixel circuit may be an active matrix type that controls the emission of a plurality of organic light-emitting elements independently. The active matrix type circuit may be voltage programming or current programming. The driving circuit has a pixel circuit for each pixel. The pixel circuit may have an organic light-emitting element, a transistor that controls the emission luminance of the organic light-emitting element, a transistor that controls the emission timing, a capacitance that holds the gate voltage of the transistor that controls the emission luminance, and a transistor for connecting to GND without going through the light-emitting element.

[0069] The light emitting device has a display region and a peripheral region arranged around the display region. The display region has a pixel circuit, and the peripheral region has a display control circuit. The mobility of a transistor constituting the pixel circuit may be smaller than the mobility of a transistor constituting the display control circuit. The slope of the current-voltage characteristic of the transistor constituting the pixel circuit may be smaller than the slope of the current-voltage characteristic of the transistor constituting the display control circuit. The slope of the current-voltage characteristic can be measured by the so-called Vg-Ig characteristic. The transistor constituting the pixel circuit is a transistor connected to an organic light emitting element.

[0070] [Pixels] A light emitting device having an organic light emitting element may have a plurality of pixels, each of which has sub-pixels that emit different colors, and each of the sub-pixels may have, for example, RGB light emitting colors. A pixel has an area that emits light, also called a pixel aperture. The pixel aperture may be 15 μm or less, or 5 μm or more. More specifically, it may be 11 μm, 9.5 μm, 7.4 μm, 6.4 μm, etc. The distance between subpixels may be 10 μm or less, more specifically, it may be 8 μm, 7.4 μm, 6.4 μm.

[0071] The pixels may have a known arrangement in plan view. For example, they may have a stripe arrangement, a delta arrangement, a pentile arrangement, or a Bayer arrangement. The shape of the subpixels in plan view may be any known shape. For example, they may be a rectangle, a quadrangle such as a diamond, or a hexagon. Of course, if the shape is not an exact figure but is close to a rectangle, it is included in the rectangle. The shape of the subpixels and the pixel arrangement may be used in combination.

[0072] [Uses of organic light-emitting devices] The organic light-emitting element of the present invention can be used as a component of a display device or a lighting device, and can also be used as an exposure light source for an electrophotographic image forming apparatus, a backlight for a liquid crystal display device, a light-emitting device having a white light source and a color filter, etc.

[0073] The display device may be an image information processing device having an image input unit that inputs image information from an area CCD, a linear CCD, a memory card, etc., an information processing unit that processes the input information, and displays the input image on the display unit. The display device may have a plurality of pixels, at least one of which has the organic light-emitting element of the present invention, and may further have a transistor connected to the organic light-emitting element.

[0074] The display unit of the imaging device or inkjet printer may have a touch panel function. The driving method of this touch panel function may be an infrared type, a capacitance type, a resistive film type, or an electromagnetic induction type, and is not particularly limited. The display device may be used in the display unit of a multifunction printer.

[0075] Next, the display device according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a display device having an organic light-emitting element of the present invention and a transistor connected to the organic light-emitting element. FIG. 1(a) is an example of a pixel that is a component of the display device according to this embodiment. The pixel has a subpixel 20. The subpixels are divided into 20R, 20G, and 20B according to their light emission. The emitted light color may be distinguished by the wavelength emitted from the light-emitting layer, or the light emitted from the subpixel may be selectively transmitted or color-converted by a color filter or the like. Each subpixel has a first electrode 12 that is a reflective electrode on an interlayer insulating layer 11, an insulating layer 13 that covers the edge of the first electrode 12, an organic compound layer 14 that covers the first electrode 12 and the insulating layer 13, a second electrode 15, a protective layer 16, and a color filter 17. The first electrode 12, the organic compound layer 14, and the second electrode 15 constitute an organic light-emitting element 18 of this embodiment.

[0076] A transistor and a capacitor may be disposed below or inside the interlayer insulating layer 11. The transistor and the first electrode 12 may be electrically connected via a contact hole (not shown) or the like. The insulating layer 13 is also called a bank or a pixel separation film. It covers the ends of the first electrodes 12 and is disposed so as to surround the first electrodes 12. The portion where the insulating layer 13 is not disposed contacts the organic compound layer 14 and becomes a light-emitting region. The second electrode 15 may be a transparent electrode, a reflective electrode, or a semi-transparent electrode. The protective layer 16 reduces the penetration of moisture into the organic compound layer 14. Although the protective layer 16 is illustrated as being a single layer, it may be a multi-layer. Each layer may be an inorganic compound layer and an organic compound layer.

[0077] The color filters 17 are divided into 17R, 17G, and 17B according to their colors. The color filters may be formed on a planarization film (not shown). A resin protective layer (not shown) may be provided on the color filters. The color filters 17 may be formed on a protective layer 16. Alternatively, the color filters 17 may be provided on an opposing substrate such as a glass substrate and then bonded to each other.

[0078] The display device in Fig. 1(b) has an organic light-emitting element 36 and a TFT 28 as an example of a transistor. Specifically, a substrate 21 such as glass or silicon has an insulating layer 22 provided thereon, and a TFT 28 having a gate electrode 23, a gate insulating film 24, a semiconductor layer 25, a drain electrode 26, and a source electrode 27 is disposed on the insulating layer 22. An insulating film 29 is provided on the TFT 28, and the anode 31 constituting the organic light-emitting element 36 is connected to the source electrode 27 through a contact hole 30 provided in the insulating film 29.

[0079] Note that the method of electrical connection between the electrodes (anode 31, cathode 33) included in the organic light-emitting element 36 and the electrodes (source electrode 27, drain electrode 26) included in the TFT 28 is not limited to the mode shown in Fig. 2(b). That is, any one of the anode 31 and the cathode 33 may be electrically connected to any one of the source electrode 27 and the drain electrode 26. The TFT 28 refers to a thin-film transistor. A first protective layer 34 and a second protective layer 35 for reducing the deterioration of the organic light-emitting element are provided on the cathode 33.

[0080] The light emission luminance of the organic light-emitting element 36 according to this embodiment is controlled by the TFT 28, and an image can be displayed by the respective light emission luminances by providing the organic light-emitting element 36 in a plurality of planes.

[0081] In the display device of Fig. 1(b), a transistor is used as a switching element, but other switching elements may be used instead. Also, the transistor used in the display device of Fig. 1(b) is not limited to a TFT having an active layer on an insulating surface of a substrate, and a transistor using a single-crystalline silicon wafer may also be used. Further, as the active layer, non-single-crystalline silicon such as amorphous silicon or microcrystalline silicon, or a non-single-crystalline oxide semiconductor such as indium zinc oxide or indium gallium zinc oxide may be used.

[0082] Alternatively, the transistor may be made of low-temperature polysilicon, or an active matrix driver may be formed on a substrate such as a Si substrate. On the substrate can also be said to be inside the substrate. Whether to provide a transistor inside the substrate or to use a TFT is selected depending on the size of the display unit. For example, if the size is about 0.5 inches, it is preferable to provide an organic light-emitting element on a Si substrate. Here, forming inside the substrate means that the substrate itself, such as a Si substrate, is processed to produce a transistor. In other words, having a transistor inside the substrate can be seen as the substrate and the transistor being formed integrally.

[0083] 2 is a schematic diagram showing an example of a display device according to the present invention. The display device 1000 has a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between an upper cover 1001 and a lower cover 1009. Flexible printed circuits FPC1002 and 1004 are connected to the touch panel 1003 and the display panel 1005. A transistor is printed on the circuit board 1007. The battery 1008 may not be provided if the display device is not a portable device, and may be provided in a different position even if the display device is a portable device.

[0084] The display device according to the present embodiment may have color filters having red, green, and blue colors, the red, green, and blue colors being arranged in a delta arrangement.

[0085] The display device according to the present embodiment may be used as a display unit of a mobile terminal. In this case, the display device may have both a display function and an operation function. Examples of the mobile terminal include mobile phones such as smartphones, tablets, and head-mounted displays.

[0086] The display device according to the present embodiment may be used as a display unit of an imaging device having an optical unit with a plurality of lenses and an imaging element that receives light that has passed through the optical unit. The imaging device may have a display unit that displays information acquired by the imaging element. The display unit may be a display unit exposed to the outside of the imaging device, or may be a display unit disposed within a viewfinder. The imaging device may be a digital camera or a digital video camera.

[0087] 3(a) is a schematic diagram showing an example of an imaging device according to the present invention. The imaging device 1100 has a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 may have a display device according to this embodiment. In that case, the display device may display not only an image to be captured, but also environmental information, imaging instructions, and the like. The environmental information may include the intensity of external light, the direction of external light, the moving speed of the subject, the possibility that the subject will be blocked by an obstruction, and the like.

[0088] Since the timing suitable for imaging is short, it is better to display information as soon as possible. Therefore, it is preferable to use a display device using the organic light-emitting element of the present invention. This is because the organic light-emitting element has a fast response speed. A display device using the organic light-emitting element can be used more preferably than a liquid crystal display device, which requires a high display speed.

[0089] The imaging device 1100 has an optical section (not shown). The optical section has a plurality of lenses, which form an image on an imaging element housed in a housing 1104. The focus of the plurality of lenses can be adjusted by adjusting their relative positions. This operation can also be performed automatically. The imaging device may be called a photoelectric conversion device. The photoelectric conversion device can include an imaging method that does not capture images sequentially, but detects the difference from the previous image, cuts out an image from an image that is always recorded, and the like.

[0090] FIG. 3(b) is a schematic diagram showing an example of an electronic device according to the present invention. The electronic device 1200 has a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may have a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and performs unlocking or the like. An electronic device having a communication unit can also be called a communication device. The electronic device may further have a camera function by including a lens and an image sensor. An image captured by the camera function is displayed on the display unit. Examples of the electronic device include a smartphone and a notebook computer.

[0091] FIG. 4 is a schematic diagram showing an example of a display device according to the present invention. FIG. 4(a) shows a display device such as a television monitor or a PC monitor. The display device 1300 has a frame 1301 and a display unit 1302. The display unit 1302 uses a light-emitting device using an organic light-emitting element according to the present invention. The display unit 1300 has the frame 1301 and a base 1303 that supports the display unit 1302. The base 1303 is not limited to the form shown in FIG. 4(a). The lower side of the frame 1301 may also serve as the base. The frame 1301 and the display unit 1302 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less.

[0092] FIG. 4(b) is a schematic diagram showing another example of a display device according to the present invention. The display device 1310 in FIG. 4(b) is configured to be bendable, and is a so-called foldable display device. The display device 1310 has a first display unit 1311, a second display unit 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 have a light-emitting device using an organic light-emitting element according to the present invention. The first display unit 1311 and the second display unit 1312 may be a single display unit without a joint. The first display unit 1311 and the second display unit 1312 can be separated at the bending point. The first display unit 1311 and the second display unit 1312 may display different images, or the first and second display units may display one image.

[0093] FIG. 5(a) is a schematic diagram showing an example of a lighting device according to the present invention. The lighting device 1400 has a housing 1401, a light source 1402, a circuit board 1403, an optical filter 1404, and a light diffusion unit 1405. The light source 1402 has an organic light-emitting element according to the present invention. The optical filter 1404 may be a filter that improves the color rendering of the light source. The light diffusion unit 1405 can effectively diffuse the light of the light source 1402, such as for lighting up, and deliver the light over a wide range. The optical filter 1404 and the light diffusion unit 1405 may be provided on the light emission side of the lighting. If necessary, a cover may be provided on the outermost part.

[0094] The lighting device is, for example, a device that illuminates a room. The lighting device may emit white light, natural white light, or any other color from blue to red. It may have a dimming circuit that adjusts the light intensity. The lighting device has the organic light-emitting element of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts AC voltage into DC voltage. Moreover, white has a color temperature of 4200K, and natural white has a color temperature of 5000K. The lighting device may have a color filter. The lighting device according to the present invention may further include a heat dissipation section that dissipates heat from within the device to the outside, and examples of the heat dissipation section include metals with high specific heat, liquid silicone, and the like.

[0095] Fig. 5(b) is a schematic diagram of an automobile, which is an example of a moving body according to the present invention. The automobile has tail lamps, which are an example of a lamp. The automobile 1500 has tail lamps 1501, and may be configured to turn on the tail lamps when braking or the like is performed. A tail lamp 1501 has an organic light-emitting element according to the present invention. The tail lamp may have a protective member for protecting the organic light-emitting element. The protective member may be made of any material as long as it has a certain degree of strength and is transparent, but it is preferable that the protective member is made of polycarbonate or the like. A furandicarboxylic acid derivative, an acrylonitrile derivative, or the like may be mixed with the polycarbonate.

[0096] Automobile 1500 may have a vehicle body 1503 and a window 1502 attached thereto. The window may be a transparent display as long as it is not a window for checking the front and rear of the vehicle. The transparent display has an organic light-emitting element according to the present invention, and the constituent materials of the electrodes and the like of the organic light-emitting element are made of transparent members.

[0097] The moving body according to the present invention may be a ship, an aircraft, a drone, or the like. The moving body has a body and a lamp provided on the body. The lamp emits light to indicate the position of the body. The lamp has the organic light-emitting element according to the present invention.

[0098] An application example of the display device of each of the above-mentioned embodiments will be described with reference to Fig. 6. The display device can be applied to a system that can be worn as a wearable device such as smart glasses, HMD, and smart contacts. An image capturing and display device used in such an application example has an image capturing device capable of photoelectrically converting visible light, and a display device capable of emitting visible light.

[0099] 6(a) shows glasses 1600 (smart glasses) according to one application example. An imaging device 1602 such as a CMOS sensor or a SPAD is provided on the front side of a lens 1601 of the glasses 1600. In addition, a display device according to each of the above-mentioned embodiments is provided on the back side of the lens 1601.

[0100] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the image capture device 1602 and the display device according to each embodiment. The control device 1603 also controls the operations of the image capture device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light on the image capture device 1602.

[0101] FIG. 6(b) is another embodiment of glasses 1610 (smart glasses). The glasses 1610 have a control device 1612, which is equipped with an imaging device corresponding to the imaging device 1602 in FIG. 6(a) and a display device. The lens 1611 is formed with an imaging device in the control device 1612 and an optical system for projecting light emitted from the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source that supplies power to the imaging device and the display device, and controls the operation of the imaging device and the display device. The control device may have a line of sight detection unit that detects the line of sight of the wearer. Infrared light may be used to detect the line of sight. The infrared light emission unit emits infrared light to the eyeball of a user gazing at a displayed image. An imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. By having a reduction means for reducing light from the infrared light emission unit to the display unit in a planar view, deterioration of image quality is reduced.

[0102] The user's gaze with respect to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be applied to gaze detection using an image of the eyeball. As an example, a gaze detection method based on a Purkinje image produced by reflection of irradiated light on the cornea can be used. More specifically, a gaze detection process based on a pupil-corneal reflex method is performed. Using the pupil-corneal reflex method, a gaze vector representing the direction (rotation angle) of the eyeball is calculated based on the image of the pupil and the Purkinje image contained in the image of the eyeball, thereby detecting the user's gaze.

[0103] The display device according to the present invention may have an imaging device having a light receiving element, and may control the display image of the display device based on the user's line of sight information from the imaging device. Specifically, the display device determines a first field of view area to which the user gazes and a second field of view area other than the first field of view area based on the line of sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0104] The display area includes a first display area and a second display area different from the first display area, and an area having a high priority is determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. The resolution of the area having a high priority may be controlled to be higher than the resolution of areas other than the area having a high priority. In other words, the resolution of an area having a relatively low priority may be lowered.

[0105] In addition, AI may be used to determine the first field of view area and the area with high priority. The AI ​​may be a model configured to estimate the angle of the line of sight and the distance to an object at the end of the line of sight from the image of the eyeball, using the image of the eyeball and the direction in which the eyeball in the image was actually looking as teacher data. The AI ​​program may be included in the display device, the imaging device, or an external device. If included in the external device, it is transmitted to the display device via communication. When display control is performed based on visual recognition detection, the present invention is preferably applicable to smart glasses that further include an imaging device for capturing images of the outside world. The smart glasses can display captured outside information in real time.

[0106] FIG. 7(a) is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1700 is an electrophotographic image forming apparatus, and includes a photoconductor 1707, an exposure light source 1708, a charging unit 1710, a developing unit 1711, a transfer unit 1712, a transport roller 1713, and a fixing unit 1715. Light 1709 is irradiated from the exposure light source 1708, and an electrostatic latent image is formed on the surface of the photoconductor 1707. The exposure light source 1708 includes an organic light emitting element according to the present invention. The developing unit 1711 includes a toner and the like. The charging unit 1710 charges the photoconductor 1707. The transfer unit 1712 transfers the developed image to a recording medium 1714. The transport roller 1713 transports the recording medium 1714. The recording medium 1714 is, for example, paper. The fixing unit 1715 fixes the image formed on the recording medium 1714.

[0107] 7(b) and 7(c) are diagrams showing the exposure light source 1708, and are schematic diagrams showing a state in which a plurality of light-emitting units 1726 are arranged on a long substrate. An arrow 1727 is a direction parallel to the axis of the photoconductor, and represents the column direction in which the organic light-emitting elements are arranged. This column direction is the same as the axis direction about which the photoconductor 1707 rotates. This direction can also be called the long axis direction of the photoconductor 1707. FIG. 7(b) shows a form in which the light-emitting units 1726 are arranged along the long axis direction of the photoconductor 1707. FIG. 7(c) shows a form different from FIG. 7(b), in which the light-emitting units 1726 are alternately arranged in the column direction in each of the first column and the second column. The first column and the second column are arranged at different positions in the row direction. In the first column, a plurality of light-emitting units 1726 are arranged at intervals. In the second column, the light-emitting units 1726 are arranged at positions corresponding to the intervals between the light-emitting units 1726 in the first column. That is, the light emitting units 1726 are also spaced apart in the row direction. The arrangement in Fig. 7(c) can also be described as a grid arrangement, a houndstooth arrangement, or a checkerboard pattern.

[0108] As described above, by using a device using the organic light-emitting element according to the present invention, it is possible to achieve a display with good image quality and stability even over a long period of time.

[0109] [Included configuration] The disclosure of this embodiment includes the following configuration. (Configuration 1) An organic light-emitting element comprising a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, in this order; the first light-emitting layer comprises a first organic compound, a first light-emitting material, and a second light-emitting material; and the second light-emitting layer comprises a second organic compound and a third light-emitting material, wherein the organic light-emitting element satisfies the following formulae [1] to [4]: [1] HOMOd2-HOMOh1 <LUMOh2-LUMOd3 [2] Content of first luminescent material < Content of second luminescent material [3] The content of the first luminescent material < the content of the third luminescent material [4] Content of second luminescent material < 2.0% by mass HOMOh1: HOMO level of the first organic compound HOMOd2: HOMO level of the second emitting material LUMOh2: LUMO levels of second organic compounds LUMOd3: LUMO level of the third emitting material (Configuration 2) The organic light-emitting device according to configuration 1, further comprising an adjacent layer on the second electrode side of the second light-emitting layer, the adjacent layer being made of an organic compound comprising a hydrocarbon.

[0110] (Configuration 3) An organic light-emitting element comprising a first electrode, a first light-emitting layer, a second light-emitting layer, an adjacent layer, and a second electrode, in this order; the first light-emitting layer comprises a first organic compound, a first light-emitting material, and a second light-emitting material; the second light-emitting layer comprises a second organic compound and a third light-emitting material; the adjacent layer is composed of an organic compound comprising a hydrocarbon; and the organic light-emitting element satisfies the following formula [4]: [4] Content of second luminescent material < 2.0% by mass (Configuration 4) 4. The organic light-emitting device according to claim 2 or 3, wherein the organic compound made of a hydrocarbon has a condensed polycyclic aromatic ring having four or more rings. (Configuration 5) The organic compound consisting of the hydrocarbon is sp 25. The organic light-emitting device according to any one of configurations 2 to 4, which is composed only of carbon.

[0111] (Configuration 6) 6. The organic light-emitting device according to any one of Structures 1 to 5, further comprising a layer having an arylamine derivative on the first electrode side of the first light-emitting layer. (Configuration 7) 7. The organic light-emitting device according to any one of configurations 1 to 6, wherein the content of the third light-emitting material is 1.0% by mass or more. (Configuration 8) 8. The organic light-emitting device according to any one of configurations 1 to 7, wherein the content of the first light-emitting material is less than 0.3% by mass. (Configuration 9) 9. The organic light-emitting device according to any one of configurations 1 to 8, wherein the first light-emitting layer has a thickness greater than that of the second light-emitting layer.

[0112] (Configuration 10) 10. The organic light-emitting device according to any one of configurations 1 to 9, wherein the first organic compound and the second organic compound are the same compound. (Configuration 11) 11. The organic light-emitting device according to any one of configurations 1 to 10, wherein the first light-emitting material, the second light-emitting material, and the third light-emitting material each contain a fluoranthene skeleton. (Configuration 12) 12. The organic light-emitting device according to any one of configurations 1 to 11, wherein the first organic compound and the second organic compound each contain a pyrene skeleton. (Configuration 13) 13. The organic light-emitting device according to any one of Structures 1 to 12, wherein all of the compounds constituting the first light-emitting layer and the second light-emitting layer are made of hydrocarbons. (Configuration 14) The first organic compound and the second organic compound each have a freely rotatable single bond that is a carbon-carbon bond, and at least one carbon of the carbon-carbon bond is a sp 2 14. The organic light-emitting device according to any one of structures 1 to 13, wherein the organic light-emitting element is carbon.

[0113] (Configuration 15) A display device comprising a plurality of pixels, at least one of the plurality of pixels comprising an organic light-emitting element according to any one of structures 1 to 14 and a transistor connected to the organic light-emitting element. (Configuration 16) an optical unit having a plurality of lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays an image captured by the image sensor; 15. A photoelectric conversion device, wherein the display section comprises the organic light-emitting element according to any one of the first to fourteenth aspects. (Configuration 17) An electronic device comprising: a display unit having the organic light-emitting element according to any one of structures 1 to 14; a housing in which the display unit is provided; and a communication unit provided in the housing and configured to communicate with an external device. (Configuration 18) 15. An illumination device comprising: a light source having the organic light-emitting element according to claim 1; and a light diffusion section or an optical filter that transmits light emitted by the light source. (Configuration 19) A moving body comprising: a lighting fixture having the organic light-emitting element according to any one of configurations 1 to 14; and a body on which the lighting fixture is provided. (Configuration 20) 15. An image forming apparatus comprising: a photoconductor; and an exposure light source for exposing said photoconductor, said exposure light source comprising the organic light-emitting element according to any one of configurations 1 to 14. EXAMPLES

[0114] The present invention will be described below with reference to examples. However, the present invention is not limited to these. The compounds used in the examples were synthesized according to known synthesis methods.

[0115] Table 1 shows the HOMO and LUMO levels of the light-emitting layer materials used in the examples. The HOMO level is the value of the ionization potential of each compound, which is measured by vacuum deposition of a 50 nm film using a Riken Keiki AC-3. The LUMO level is the value obtained by measuring the absorption spectrum of a film similarly prepared, determining the optical absorption edge as the band gap, and then subtracting it from the ionization potential.

[0116] [Table 1]

[0117] Example 1 In this example, an organic light-emitting element having a top-emission structure was produced in which an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode were successively formed on a substrate. A 40 nm Ti film was formed on a glass substrate by sputtering, and then patterned using photolithography to form an anode. The electrode area of ​​the anode was 3 mm. 2 Then, the mixture was washed. Next, the electrode-attached substrate prepared above was attached to a vacuum deposition apparatus (manufactured by ULVAC), and after preparing the deposition material, 1.33 × 10 -4 Pa(1×10 -6 The chamber was evacuated to a pressure of 100 MPa (120 Torr). The chamber was then subjected to UV / ozone cleaning. Each layer was then formed in the layer configuration shown in Table 2. The substrate was then transferred to a glove box and sealed in a nitrogen atmosphere with a glass cap containing a desiccant to obtain an organic light-emitting device.

[0118] [Table 2]

[0119] A voltage application device was connected to the obtained organic light-emitting device, and its characteristics were evaluated. The current-voltage characteristics were measured with a Hewlett-Packard 4140B microammeter, and the chromaticity was evaluated with a Topcon SR-3. The luminance was measured with a Topcon BM7. 2 The current efficiency calculated from the current value and the emitted luminance when the device was made to emit light at a luminance of 4.5 cd / A was found to be a good white organic light-emitting device. In addition, the initial brightness is 2000cd / m 2 The degradation rate of the luminance after 100 hours was measured. The results are shown in Table 3.

[0120] (Examples 2 to 22, Comparative Examples 1 to 17) An organic light-emitting device was produced and its characteristics were evaluated in the same manner as in Example 1, except that the light-emitting layer in Example 1 was changed to the configuration shown in Tables 3 to 5. The results are shown in Tables 3 to 5. The current efficiency is expressed as a ratio relative to the current efficiency of Example 5, which is set to 1.0, and the durability evaluation is expressed as a ratio relative to the luminance deterioration rate of Example 5, which is set to 1.0. In addition, in Tables 3 to 5, "ΔHOMO" indicates the difference in HOMO levels (HOMOd2-HOMOh1) between the second light-emitting material and the first organic compound in the first light-emitting layer, and "ΔLUMO" indicates the difference in LUMO levels (LUMOh2-LUMOd3) between the second organic compound and the third light-emitting material in the second light-emitting layer.

[0121] [Table 3]

[0122] [Table 4]

[0123] [Table 5]

[0124] It can be seen from Examples 1 to 3 and Comparative Examples 2 and 3 that both the current efficiency and durability are improved when the content of the second light-emitting material is less than 2.0 mass %. This is because when the content of the second light-emitting material is low, the hole trapping ability of the first light-emitting layer is improved, and the recombination region is closer to the interface between the first light-emitting layer and the electron blocking layer, causing deterioration of the electron blocking layer.

[0125] Moreover, when the contents of the first and second light-emitting materials are the same as in Comparative Example 1, the balance of red, green and blue light emission is significantly disrupted, resulting in a significant decrease in current efficiency, which is not preferable.

[0126] It can be seen from Examples 4 to 6 and Comparative Example 4 that the current efficiency and durability characteristics improve as the content of the third light-emitting material increases. This is because the electron trapping ability of the second light-emitting layer improves when the content of the third light-emitting material is large, and the recombination region is separated from the interface between the first light-emitting layer and the electron blocking layer, thereby reducing deterioration of the electron blocking layer.

[0127] From Examples 7 and 8, it is found that if the content of the first emitting material is high, the current efficiency decreases due to concentration quenching, so the content is preferably less than 0.3 mass %, and more preferably less than 0.2 mass %.

[0128] It can be seen from Examples 9 to 11 that the durability improves when the first emitting layer is thicker than the second emitting layer, because the thicker first emitting layer separates the recombination region from the interface between the first emitting layer and the electron blocking layer, thereby reducing the deterioration of the electron blocking layer.

[0129] When formula [4] is not satisfied, as in Comparative Examples 5 to 15, the current efficiency and durability are deteriorated. This is because charges are not confined in the light-emitting layer and the hole trapping ability of the first light-emitting layer is not sufficiently alleviated, causing recombination at the interface with the electron blocking layer.

[0130] From the above, it was found that in the organic light-emitting device of the present invention, in addition to confining the charge in the light-emitting layer and delocalizing the recombination region, the durability characteristics are improved by moving the recombination region a little away from the interface between the first light-emitting layer and the electron blocking layer.To achieve this, the content of the light-emitting material in the first light-emitting layer is reduced to relax the hole trapping ability of the first light-emitting layer, and the electron trapping ability of the second light-emitting layer is strengthened to move the recombination region away from the interface, thereby improving the driving durability characteristics.

[0131] (Examples 23 to 29, Comparative Examples 18 to 20) Organic light-emitting devices were fabricated and their characteristics were evaluated in the same manner as in Examples 2, 22, and 18, except that the materials of the adjacent layers were changed to those shown in Table 6. The results are shown in Table 6.

[0132] [Table 6]

[0133] Although the materials of the light-emitting layers are the same in Examples 2, 23 to 27, the efficiency and durability are improved compared to Comparative Example 18. This is because the adjacent layer in Comparative Example 18 is a compound having heteroatoms, which is highly chemically reactive and prone to causing degradation during operation. On the other hand, the adjacent layer in Examples 2, 23 to 27 is a compound made of hydrocarbon, which is highly stable and can suppress degradation during operation.

[0134] Similar effects were also obtained for Examples 22, 28, 20, and 29 and Comparative Examples 19 and 20, which had different light-emitting layer configurations.

[0135] (Examples 30 and 31, Comparative Examples 21 to 29) An organic light-emitting device was produced and its characteristics were evaluated in the same manner as in Example 2, except that the materials and concentrations of the light-emitting layer and the adjacent layers were changed to those shown in Table 7. The results are shown in Table 7.

[0136] [Table 7]

[0137] Example 2 and Comparative Examples 21 to 23 are examples in which the concentration of the second light-emitting material in the first light-emitting layer was changed. As the concentration of the second light-emitting material was reduced to less than 2%, the efficiency and durability improved. This is because the lower the concentration of the second light-emitting material, the lower the hole trapping performance of the first light-emitting layer, and the recombination region shifts toward the second light-emitting layer (away from the electron blocking layer). In Comparative Examples 18 and 24, the adjacent layer was changed from a stable hydrocarbon compound to a heteroatom-containing compound, and the efficiency and durability were worse than those of Example 2 and Comparative Example 23. This is because, as described above, the adjacent layer was a heteroatom-containing compound and was prone to deterioration.

[0138] In Example 30 and Comparative Examples 25 to 27, the third luminescent material was changed. Even if the molecular structure of the third luminescent material was significantly changed, the same effect was obtained by adjusting the concentration of the second luminescent material and by using a hydrocarbon as the adjacent layer.

[0139] Example 31 and Comparative Examples 28 and 29 are examples in which the relationship between the concentration of the third luminescent material and the concentration of the first luminescent material is changed. Regardless of the concentration of these luminescent materials, the same effect can be obtained by changing the concentration of the second luminescent material and the fact that the adjacent layer is made of a hydrocarbon. [Explanation of symbols]

[0140] 12: first electrode, 15: second electrode, 18, 36: organic light-emitting element, 1000, 1300, 1310: display device, 1100: imaging device, 1104, 1203, 1313: housing, 1200: electronic device, 1201, 1302, 1311, 1312: display unit, 1402: light source, 1404: optical filter, 1405: light diffusion unit

Claims

1. An organic light-emitting element comprising a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, in this order; the first light-emitting layer comprises a first organic compound, a first light-emitting material, and a second light-emitting material; and the second light-emitting layer comprises a second organic compound and a third light-emitting material, wherein the organic light-emitting element satisfies any of the following formulae [1] to [4]: [1] HOMOd2-HOMOh1<LUMOh2-LUMOd3 [2] The content of the first light-emitting material is less than the content of the second light-emitting material. [3] The content of the first light-emitting material is less than the content of the third light-emitting material. [4] The content of the second light-emitting material is less than 2.0% by mass. HOMOH1: HOMO level of the first organic compound HOMOd2: HOMO level of the second light-emitting material LUMOH2: LUMO level of the second organic compound LUMOd3: LUMO level of the third light-emitting material

2. 2 . The organic light-emitting element according to claim 1 , further comprising an adjacent layer on the second electrode side of the second light-emitting layer, the adjacent layer being made of an organic compound comprising a hydrocarbon.

3. An organic light-emitting element comprising a first electrode, a first light-emitting layer, a second light-emitting layer, an adjacent layer, and a second electrode, in this order; the first light-emitting layer comprises a first organic compound, a first light-emitting material, and a second light-emitting material; the second light-emitting layer comprises a second organic compound and a third light-emitting material; the adjacent layer is composed of an organic compound comprising a hydrocarbon; and the organic light-emitting element satisfies the following formula [4]: [4] The content of the second light-emitting material is less than 2.0% by mass.

4. 4. The organic light-emitting element according to claim 2, wherein the organic compound made of a hydrocarbon has a condensed polycyclic aromatic ring having four or more rings.

5. The organic compound consisting of the hydrocarbon is sp 2 4. The organic light-emitting device according to claim 2, which is composed only of carbon.

6. 4. The organic light-emitting element according to claim 1, further comprising a layer having an arylamine derivative on the first electrode side of the first light-emitting layer.

7. 4. The organic light-emitting element according to claim 1, wherein the content of the third light-emitting material is 1.0% by mass or more.

8. 4. The organic light-emitting device according to claim 1, wherein the content of the first light-emitting material is less than 0.3% by mass.

9. 4. The organic light-emitting element according to claim 1, wherein the first light-emitting layer has a thickness greater than that of the second light-emitting layer.

10. 4. The organic light-emitting element according to claim 1, wherein the first organic compound and the second organic compound are the same compound.

11. The organic light-emitting element according to claim 1 , wherein the first light-emitting material, the second light-emitting material, and the third light-emitting material each contain a fluoranthene skeleton.

12. 4. The organic light-emitting element according to claim 1, wherein the first organic compound and the second organic compound each contain a pyrene skeleton.

13. 4. The organic light-emitting element according to claim 1, wherein all of the compounds constituting the first light-emitting layer and the second light-emitting layer are composed of hydrocarbons.

14. The first organic compound and the second organic compound each have a freely rotatable single bond that is a carbon-carbon bond, and at least one carbon of the carbon-carbon bond is an sp 2 4. The organic light-emitting device according to claim 1, wherein the organic light-emitting element is carbon.

15. A display device comprising a plurality of pixels, at least one of the plurality of pixels comprising the organic light-emitting element according to claim 1 and a transistor connected to the organic light-emitting element.

16. an optical unit having a plurality of lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays an image captured by the image sensor; The photoelectric conversion device according to claim 1 , wherein the display section comprises the organic light-emitting element according to claim 1 .

17. 13. An electronic device comprising: a display section having the organic light-emitting element according to claim 1; a housing in which the display section is provided; and a communication section provided in the housing for communicating with an external device.

18. 13. An illumination device comprising: a light source having the organic light-emitting element according to claim 1; and a light diffusion section or an optical filter that transmits light emitted by the light source.

19. A moving object comprising: a lighting device having the organic light-emitting element according to claim 1; and a body on which the lighting device is provided.

20. 13. An image forming apparatus comprising: a photoconductor; and an exposure light source for exposing said photoconductor, said exposure light source comprising the organic light emitting element according to claim 1.

21. A display device comprising a plurality of pixels, at least one of the plurality of pixels comprising the organic light-emitting element according to claim 3 and a transistor connected to the organic light-emitting element.

22. an optical unit having a plurality of lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays an image captured by the image sensor; The photoelectric conversion device according to claim 3 , wherein the display section comprises the organic light-emitting element according to claim 3 .

23. 4. An electronic device comprising: a display section having the organic light-emitting element according to claim 3; a housing in which the display section is provided; and a communication section provided in the housing for communicating with an external device.

24. 4. An illumination device comprising: a light source having the organic light-emitting element according to claim 3; and a light diffusion section or an optical filter that transmits light emitted by the light source.

25. A moving body comprising: a lighting device having the organic light-emitting element according to claim 3; and a body on which the lighting device is provided.

26. 4. An image forming apparatus comprising: a photoconductor; and an exposure light source for exposing said photoconductor, said exposure light source comprising the organic light emitting element according to claim 3.

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