Organic light-emitting element

Abstract

Provided is an organic light-emitting element having improved device characteristics including luminous efficiency and durability. The organic light-emitting element comprises a first electrode (2), a second electrode (4) and an organic compound layer (3) disposed between the first electrode (2) and the second electrode (4). The organic compound layer (3) has an electron transport layer (3b) in contact with the second electrode (4). The electron transport layer (3b) is composed of an organic compound having a 1,10-phenanthroline skeleton.

Description

Organic light-emitting device

[0001] The present invention relates to an organic light-emitting device having high luminous efficiency.

[0002] An organic light-emitting device (also referred to as an "organic electroluminescence device" or an "organic EL device") is composed of a first electrode, a second electrode, and an organic compound layer between the two electrodes. The light emitted from the light-emitting layer in the organic compound layer is emitted from one of the first electrode or the second electrode (the light extraction electrode). In an organic light-emitting device, an electron injection layer using a metal with a small work function such as Li is used for low-voltage driving. In such an electron injection layer, Li is used in a compound such as LiF, and by including a reducing metal such as Mg in the second electrode, it is utilized, but it also contributes to reducing the light transmittance of the second electrode.

[0003] In recent years, for further development in application products, technologies for improving the luminous efficiency and driving durability of organic light-emitting devices have been demanded.

[0004] Patent Document 1 describes an organic electroluminescent device having an organic layer between a pair of electrodes, wherein the cathode among the pair of electrodes contains an alloy of Ag and Li, and the concentration of Li with respect to Ag is 0.04% by mass to 0.3% by mass.

[0005] Japanese Patent Application Laid-Open No. 9-283281

[0006] Patent Document 1 describes the configuration of an organic light-emitting device containing Li in the second electrode. However, since Li has a property of easily diffusing outside the layer during device driving, there are problems such as quenching of light emission due to diffusion of Li into the light-emitting layer, and luminance degradation easily occurring due to a decrease in electron injection property during long-time driving.

[0007] In view of the above problems, the present invention aims to provide an organic light-emitting device with improved luminous efficiency and improved driving durability characteristics in an organic light-emitting device containing Li in the second electrode.

[0008] The present invention relates to an organic light-emitting element comprising a first electrode, a second electrode, and an organic compound layer disposed between the first electrode and the second electrode, wherein the organic compound layer comprises at least a light-emitting layer and an electron transport layer, and the electron transport layer is in contact with the second electrode, characterized in that the second electrode comprises a layer containing Li, and the electron transport layer comprises at least an organic compound A having a structure represented by the following general formula [1].

[0009]

[0010] [In the above general formula [1], A and B are each substituted or unsubstituted heterorings containing N, and heterorings A and B may be fused such that N is positioned on the outside.]

[0011] According to the present invention, it is possible to improve the device characteristics of organic light-emitting devices, including luminous efficiency and durability.

[0012] This is a schematic cross-sectional view in the thickness direction of one embodiment of the organic light-emitting element of the present invention. This is a diagram showing the absorption spectra of the second electrode and silver in Comparative Example 4 and Example 26. This is a schematic cross-sectional view showing an example of a pixel of a display device according to one embodiment of the present invention. This is a schematic cross-sectional view of an example of a display device using an organic light-emitting element according to one embodiment of the present invention. This is a schematic diagram showing an example of a display device according to one embodiment of the present invention. This is a schematic diagram of an imaging device according to one embodiment of the present invention. This is a schematic diagram of an electronic device according to one embodiment of the present invention. This is a schematic diagram of a display device according to one embodiment of the present invention. This is a schematic diagram of a foldable display device according to one embodiment of the present invention. This is a schematic diagram of a lighting device according to one embodiment of the present invention. This is a schematic diagram of an automobile having a vehicle light fixture according to one embodiment of the present invention. This is a schematic diagram of a wearable device according to one embodiment of the present invention. This is a schematic diagram showing an example of a wearable device according to one embodiment of the present invention, which has an imaging device. This is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. This is a schematic diagram showing a configuration in which multiple light-emitting parts of an exposure light source are arranged on a long substrate. This is a schematic diagram showing a configuration in which multiple light-emitting parts of an exposure light source are arranged on a long substrate.

[0013] The present invention will be described below with reference to the drawings. Figure 1 shows a schematic cross-sectional view in the thickness direction of one embodiment of the organic light-emitting element of the present invention. The organic light-emitting element of the present invention has a first electrode 2, a second electrode 4, and an organic compound layer 3 having a light-emitting layer disposed between the first electrode 2 and the second electrode 4 on a substrate 1. The organic compound layer 3 has an electron transport layer 3b in contact with the second electrode 4, and other layers such as a light-emitting layer in the region 3a excluding the electron transport layer 3b. The organic light-emitting element shown in Figure 1 is a so-called top-emission type, in which light is extracted from the second electrode 4 side opposite to the substrate 1. The second electrode 4 is a layer that can transmit light in the visible light region, including Li.

[0014] Although not specifically shown in the figures, the present invention can also be applied to so-called bottom-emission type organic light-emitting devices in which light is extracted from the substrate 1 side. Furthermore, the present invention can also be applied to double-sided light-emitting type organic light-emitting devices in which light is extracted from both the substrate 1 side and the side opposite to the substrate 1. Specifically, the present invention relates to an organic light-emitting device comprising a substrate 1, a transmissive first electrode 2, an organic compound layer 3, and a transmissive second electrode 4.

[0015] Generally, organic light-emitting devices use lithium fluoride (LiF) as the electron injection material, and electron injection is achieved by reducing LiF with an electrode made of an alloy containing Mg. This Mg absorbs light in the visible light region. Furthermore, the Li generated by the reduction of LiF is prone to diffusion within the device, and if it diffuses to the light-emitting layer, it adversely affects the device's performance.

[0016] In contrast, the second electrode 4 of the organic light-emitting element of the present invention does not contain the aforementioned Mg, and is a layer made of an alloy of Li and a transition metal. The second electrode 4 can be formed by known methods such as vapor deposition, sputtering, and photolithography. Furthermore, the second electrode 4 may have a laminated structure in which a metal layer of a different composition exists on top of the Li-containing layer.

[0017] Furthermore, the electron transport layer 3b is a layer containing organic compound A having the structure shown in the following general formula [1], and is in contact with the second electrode 4. Dry processes such as vacuum deposition, ionization deposition, sputtering, and plasma deposition can be used to form the electron transport layer 3b. Alternatively, a wet process can be used, in which the layer is formed by dissolving the compound in a suitable solvent and applying a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.).

[0018]

[0019] In the above general formula [1], A and B are each substituted or unsubstituted heterorings containing N, and heterorings A and B may be fused such that N is positioned on the outside.

[0020] The structure represented by the above general formula [1] is preferably a 2,2'-bipyridine skeleton, and more preferably a phenanthroline skeleton, which is a fused ring structure having a 2,2'-bipyridine structure within the molecule. Furthermore, a molecule may have multiple structures represented by general formula [1], in which case the structures represented by general formula [1] are preferably linked to each other via a structure in which one to four phenylene groups are continuously bonded.

[0021] The substituents that can be substituted on the heterocycles A and B are not particularly limited, but include, for example, hydrogen atoms, deuterium atoms, halogen atoms, substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted heterocyclic groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted aryloxy groups, cyano groups, and silyl groups, each of which can be selected independently. The substituents may be the same or different, and adjacent substituents may bond to each other to form a ring.

[0022] Examples of the halogen atoms mentioned above include, but are not limited to, fluorine, chlorine, bromine, iodine, astatine, and tennessine.

[0023] The alkyl group may be an alkyl group having 1 to 20 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. Specifically, examples include, but are not limited to, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, s-butyl group, octyl group, cyclohexyl group, t-pentyl group, 3-methylpentan-3-yl group, 1-adamantyl group, and 2-adamantyl group.

[0024] The alkoxy group may be an alkoxy group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms. Specifically, examples include, but are not limited to, a methoxy group, an ethoxy group, a propoxy group, an isopropyl group, a t-butoxy group, a 2-ethyloctyloxy group, a benzyloxy group, etc.

[0025] Examples of silyl groups include, but are not limited to, trimethylsilyl and triphenylsilyl groups.

[0026] The aryl group may have 6 to 20 carbon atoms, 6 to 18 carbon atoms, or 6 to 12 carbon atoms. Specifically, examples include, but are not limited to, phenyl, biphenyl, naphthyl, phenanthrenyl, triphenylenyl, indenyl, terphenyl, fluorenyl, pyrenyl, anthranyl, perilenyl, chrysenyl, and fluoranthenyl groups.

[0027] The heterocyclic group may have 3 to 24 carbon atoms, 3 to 18 carbon atoms, or 3 to 12 carbon atoms. Specifically, examples include, but are not limited to, pyridyl, pyrimidyl, pyrazyl, triazyl, benzofuranyl, benzothiophenyl, dibenzofuranyl, dibenzothiophenyl, oxazolyl, oxadiazolyl, thiazolyl, thiadiazolyl, carbazolyl, acridinyl, and phenanthrolyl groups.

[0028] The amino group may be a substituted amino group substituted with an alkyl group or an aryl group, and may be a substituted amino group substituted with an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms. Specifically, examples include, but are not limited to, N-methylamino group, N-ethylamino group, N,N-dimethylamino group, N,N-diethylamino group, N-methyl-N-ethylamino group, N-benzylamino group, N-methyl-N-benzylamino group, N,N-dibenzyloamino group, anilino group, N,N-diphenylamino group, N,N-dinaphthylamino group, N,N-difluorenylamino group, N-phenyl-N-tolylamino group, N,N-ditolylamino group, N-methyl-N-phenylamino group, N,N-dianisorylamino group, N-mesityl-N-phenylamino group, N,N-dimesitylamino group, N-phenyl-N-(4-t-butylphenyl)amino group, N-phenyl-N-(4-trifluoromethylphenyl)amino group, N-piperidyl group, etc.

[0029] Examples of aryloxy groups include, but are not limited to, phenoxy groups.

[0030] Examples of heteroaryloxy groups include, but are not limited to, thienyloxy groups.

[0031] Examples of substituents that the alkyl groups, alkoxy groups, amino groups, aryloxy groups, silyl groups, aryl groups, heterocyclic groups, and heteroaryloxy groups may further have include, but are not limited to, deuterium, alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, and t-butyl group, aralkyl groups such as benzyl group, aryl groups such as phenyl group and biphenyl group, heterocyclic groups such as pyridyl group and pyrrolyl group, amino groups such as dimethylamino group, diethylamino group, dibenzylamino group, diphenylamino group, and ditolylamino group, alkoxy groups such as methoxy group, ethoxy group, and propoxy group, aryloxy groups such as phenoxy group, halogen atoms such as fluorine, chlorine, bromine, and iodine, and cyano groups.

[0032] Specific examples of organic compound A having the structure represented by general formula [1], which is used as an electron transport material in the electron transport layer 3b in the present invention, are listed below, but the present invention is not limited to these.

[0033]

[0034] The features of the organic light-emitting element of the present invention are as follows: (1) Light absorption in the visible region can be suppressed by using electrodes containing metallic Li. (2) Diffusion of Li can be suppressed by using an electron transport material that forms a chelate complex with metallic Li.

[0035] The following provides a detailed explanation of each of these points.

[0036] [1] In the present invention, since the second electrode 4 contains metallic Li and therefore has electron injection properties, there is no need to provide a LiF layer, nor is there a need to reduce the LiF. For this reason, there is no need to include Mg in the second electrode 4 to reduce LiF, and the effect of light absorption in the visible light region that occurs when the second electrode contains Mg can be eliminated.

[0037] [2] Conventional Alq3 does not form complexes with Li. On the other hand, the inventors have found that the organic compound A contained in the electron transport layer 3b according to the present invention has the structure shown in the general formula [1] above, and therefore readily forms a chelate complex with Li diffused from the second electrode 4, thereby suppressing Li diffusion. However, as shown below, even if it has an azine unit that interacts with Li, it is difficult to exert the effect unless the two nitrogen atoms are in positions where they both interact with Li. Therefore, according to the present invention, it is preferable that the structure shown in the general formula [1] above has a 2,2'-bipyridine skeleton, in which the distance between the two nitrogen atoms is close.

[0038]

[0039] A further Li compound layer may be present between the electron transport layer 3b according to the present invention and the second electrode 4 containing metallic Li. This is because any layer containing Li will not impair the performance of the device. Examples of Li compounds include, but are not limited to, LiF, lithium oxide, and lithium carbonate.

[0040] Next, other components of the organic light-emitting device of the present invention will be described.

[0041] The substrate 1 can be made of a dielectric such as glass or plastic. Further, the substrate 1 may be composed of a support substrate, a switching element provided thereon, and an insulating layer provided thereon. Note that, for example, a transistor such as a TFT can be used as the switching element.

[0042] The first electrode 2 preferably has a high reflectivity, and a metal layer such as Al, Ag, Mo, W, Ni, Cr, or an alloy thereof can be used with a film thickness of 50 nm or more and 300 nm or less. This metal layer can be formed by methods such as vapor deposition, sputtering, or photolithography techniques. Further, the first electrode 2 may have a structure in which a transparent oxide conductive layer such as tin oxide, indium oxide, indium tin oxide, or indium zinc oxide is laminated on the light extraction side of the metal layer.

[0043] The organic compound layer 3 includes an electron transport layer 3b in contact with the second electrode 4, and includes at least a light-emitting layer on the side of the first electrode 2. If necessary, it has functional layers such as a hole injection layer, a hole transport layer, a hole blocking layer, an electron injection layer, an electron blocking layer, and an exciton blocking layer, and each functional layer is laminated in an appropriate order. Known materials can be used as the materials constituting each functional layer used in the organic compound layer. Note that the organic compound layer 3 can be formed by dry processes such as vacuum evaporation, ionization evaporation, sputtering, and plasma. Further, instead of the dry process, a wet process in which the layer is formed by dissolving it in an appropriate solvent and using a known coating method (for example, spin coating, dipping, casting method, LB method, inkjet method, etc.) can also be used.

[0044] In addition, on the second electrode 4, a transparent oxide conductive layer, an organic compound layer such as lithium fluoride or a material constituting the organic light-emitting device, and an inorganic layer such as aluminum oxide, silicon oxide, silicon nitride, or silicon oxynitride can be provided as an optical adjustment layer or a protective layer.

[0045] In the present invention, it is preferable to have the following further features: [3] A top-emission type configuration in which a resonator structure is formed by a first electrode 2 and a second electrode 4. [4] The optical distance L between the first electrode 2 and the second electrode 4 satisfies the following equation (1) with respect to the maximum peak wavelength λ when the light-emitting layer emits light and the sum of the phase shifts φ [rad] when the light of the maximum peak wavelength λ is reflected at each electrode interface: (-1-(φ / π)) × (λ / 4) < L < (1-(φ / π)) × (λ / 4) (1) [5] The material used for the electron transport layer 3b has a 1,10-phenanthroline skeleton. [6] The thickness of the electron transport layer is in the range of 5 nm to 20 nm. [7] The second electrode has a laminated structure of a layer made of an alloy containing metallic Li and a layer made of a transition metal that does not contain metallic Li. [8] There is no electron injection layer made of a Li compound. [9] A condensed polycyclic hydrocarbon compound is used as the hole blocking layer.

[10] The luminescent material LUMO of the luminescent layer is further from the vacuum level than the LUMO of the host material.

[11] The concentration of Li contained in the second electrode is 0.01% by mass or more and 10% by mass or less.

[12] A sealing layer is present on the second electrode.

[0046] The following provides a detailed explanation. [3] The organic light-emitting element according to the present invention preferably has a top-emission configuration in which light is extracted from the second electrode side and from the side opposite to the substrate 1. Furthermore, it is preferable that a resonator structure is formed in which the first electrode 2 is reflective and the second electrode 4 is reflective and transmittance with respect to the light emitted from the light-emitting layer. In an element with a resonator structure, the light emitted from the light-emitting layer is repeatedly reflected between the first electrode 2 and the second electrode 4, so the attenuation of light emission due to light absorption in each layer is greater compared to an element without a resonator structure. The second electrode 4 of the present invention suppresses light absorption in the visible region, so a more effective improvement in luminous efficiency can be obtained in an organic light-emitting element with a resonator structure.

[0047] [4] When the resonator structure described in [3] above is present, the optical distance L between the first electrode 2 and the second electrode 4 satisfies the following equation (A) for the maximum peak wavelength λ in the emission of light from the light-emitting layer, the sum of the phase shifts φ [rad] when the light of the maximum peak wavelength λ is reflected at each electrode interface, and a natural number n, the light extraction efficiency is highest. L = (2n - 1) × (-φ / π) × (λ / 4) (A)

[0048] In equation (A) above, when n=1, it is the thinnest film thickness condition in which light extraction is efficient in the resonator structure, and it is a film thickness condition that can achieve both high light extraction efficiency and low film deposition cost. At this time, in actual organic light-emitting devices, considering the viewing angle characteristics which are in a trade-off relationship with the front extraction efficiency, it is not necessarily required to strictly match the above film thickness. Specifically, there may be an error of L within the range of ±λ / 4 from the value that satisfies equation (A) above. Therefore, it is preferable that the organic light-emitting device of the present invention satisfies the following equation (1): (-1-(φ / π))×(λ / 4) < L < (1-(φ / π))×(λ / 4) (1)

[0049] More preferably, L is within the range of ±λ / 8 from the value satisfying formula (A) above, and it is preferable that the organic light-emitting element of the present invention satisfies the following formula (2): (-1-(φ / π))×(λ / 8) < L < (1-(φ / π))×(λ / 8) (2)

[0050] [5] The organic compound A contained in the electron transport layer 3b is preferably an organic compound having a 1,10-phenanthroline skeleton. This is because, as shown below, phenanthroline, which has a fused ring structure without freely transferable bonds, has a less variable distance between the two N atoms, and therefore can stably form a chelate complex with Li.

[0051]

[0052] [6] The thickness of the electron transport layer 3b is preferably in the range of 5 nm to 20 nm. This is because the uniformity of the film is good at 5 nm or more, and good device performance can be obtained. Also, a thickness of 20 nm or less is preferred because the increase in driving voltage due to the electrical resistance of the electron transport layer is suppressed at 20 nm or less.

[0053] [7] The second electrode 4 is preferably a laminated structure consisting of a layer of an alloy containing Li and a transition metal layer (second layer) that does not contain Li. This is because the presence of the second layer can suppress the diffusion of Li into the outside of the device, which would otherwise degrade the device's performance.

[0054] [8] It is preferable not to include an electron injection layer made of a Li compound between the second electrode 4 and the electron transport layer 3b. This is because the second electrode 4 has electron injection properties and therefore does not require a Li compound layer such as LiF. Although including an electron injection layer made of a Li compound does not impair the device performance, omitting this layer makes it possible to fabricate the device with fewer processes.

[0055] [9] Preferably, the electron transport layer 3b has a hole blocking layer on the first electrode side, and preferably the hole blocking layer is a layer made of a condensed polycyclic hydrocarbon compound. Since the condensed polycyclic hydrocarbon compound is a nonpolar compound, the hole blocking layer made of it has the role of protecting the light-emitting layer from Li that has diffused beyond the electron transport layer 3b. For this reason, the function of the Li diffusion prevention layer to the light-emitting layer can be enhanced when the device is driven.

[0056]

[10] The light-emitting layer contained in the organic compound layer 3a consists of a host material and at least one light-emitting material, and it is more preferable that the LUMO of the light-emitting material is further from the vacuum level than the LUMO of the host material. The greater these differences, the higher the electron trapping ability of the light-emitting layer, and the recombination region in the light-emitting layer will be distributed on the second electrode 4 side. In the present invention, stable electron injection is performed by the effects of the second electrode 4 and the electron transport layer 3b, so by increasing the electron trapping ability of the light-emitting layer, the recombination region can be kept in a stable region inside the light-emitting layer.

[0057] Examples of hole-blocking materials and light-emitting materials according to the present invention are shown below, but are not limited to these. ET8 to ET23 are specific examples of hole-blocking materials, EM1 to EM40 are host materials, R-1 to R-27 are red light-emitting materials, G-1 to G-24 are green light-emitting materials, and B-1 to B-62 are blue light-emitting materials.

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] Furthermore, LUMO refers to the lowest unsaturated orbit, and the energy level of LUMO is sometimes referred to as "LUMO" or "LUMO level."

[0066]

[11] The Li concentration in the second electrode 4 is preferably 0.01% by mass or more and 10% by mass or less. More preferably, it is 0.01% by mass or more and 3% by mass or less. When the Li concentration is 0.01% by mass or more, the Li concentration at the interface of the second electrode 4 on the first electrode 2 side is sufficient, the electron injection barrier can be sufficiently lowered, and the electron injection performance into the electron transport layer 3b is improved.

[0067] Furthermore, if the Li concentration exceeds 10% by mass, the structure of the solid solution changes. When the Li concentration is low, Li penetrates into the gaps in the crystal lattice of the other metal, forming an interstitial solid solution. However, when the Li concentration is high, the crystal lattice of the other metal changes, or it changes into a substitutional solid solution, which alters the properties of the alloy. In this case, excess Li is more likely to diffuse from the second electrode 4, and as it diffuses to the light-emitting layer, the light-emitting efficiency decreases.

[0068]

[12] It is preferable to provide a sealing layer on the second electrode 4. For example, by bonding a glass with a desiccant on the second electrode 4, the intrusion of water and the like into the organic compound layer 3 can be reduced, thereby reducing the occurrence of display defects. In another embodiment, a passivation film such as silicon nitride may be provided on the second electrode 4 to reduce the intrusion of water and the like into the organic compound layer 3. For example, after forming the second electrode 4, it may be transported to another chamber without breaking the vacuum and a silicon nitride film with a thickness of 2 μm may be formed by CVD to serve as a protective layer. A protective layer may also be provided using atomic deposition (ALD) after film formation by CVD. The material of the film formed by ALD is not limited, but may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed by CVD on the film formed by ALD. The film formed by ALD may have a thinner film thickness than the film formed by CVD. Specifically, it may be 50% or less, or even 10% or less.

[0069] Next, the parts of this embodiment other than those described above will be explained. In the organic light-emitting element of this embodiment, the organic compound layer 3 only needs to have an electron transport layer 3b and an emissive layer according to the present invention, and may also have a hole injection layer, a hole transport layer, an electron blocking layer, an electron injection layer, etc. as appropriate. The emissive layer may be a single layer or a laminate consisting of multiple layers.

[0070] The light-emitting layer comprises a host material and a guest material (dopant material), and may also include an assist material. Here, the host material is the compound with the largest mass ratio among the compounds constituting the light-emitting layer. The assist material is a compound with a smaller mass ratio than the host material among the compounds constituting the light-emitting layer, and assists the light emission of the guest material. The assist material is also called the second host material. The guest material is a compound with a smaller mass ratio than the host material among the compounds constituting the light-emitting layer, and is the compound responsible for the primary light emission.

[0071] The concentration of the guest material in the light-emitting layer is preferably 0.01% by mass or more and 30% by mass or less relative to the entire light-emitting layer, and more preferably 2% by mass or more and 20% by mass or less.

[0072] The luminescent material may be uniformly distributed throughout the entire luminescent layer, or it may be distributed with a concentration gradient. Alternatively, the luminescent material may be partially distributed in specific regions within the layer, so that the luminescent layer has regions containing only the host material and no luminescent material.

[0073] In addition to the aforementioned luminescent materials, other luminescent materials primarily involved in light emission include fused 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-quinolinolate)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 luminescent materials are shown below, but are not limited to these.

[0074]

[0075]

[0076]

[0077] Examples of host or assist materials include, but are not limited to, aromatic hydrocarbon compounds or their derivatives, as well as carbazole derivatives, azine derivatives, xanthone derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organoaluminum complexes such as tris(8-quinolinolate)aluminum, and organoberylium complexes. Specifically, examples include, but are not limited to, EM1 to EM40.

[0078] In addition to the above, conventionally known low-molecular-weight and high-molecular-weight hole-injecting or hole-transporting compounds, host compounds, luminescent compounds, electron-injecting or electron-transporting compounds, etc., can be used together as needed. Examples of these compounds are listed below.

[0079] As hole-injection transport materials, materials with high hole mobility are preferred to facilitate hole injection from the anode and to transport the injected holes to the light-emitting layer. Furthermore, materials with a high glass transition temperature are preferred to suppress deterioration of the film quality, such as crystallization, in the organic light-emitting element. Examples of low-molecular-weight and high-molecular-weight materials with hole-injection transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Moreover, the above-mentioned hole-injection transport materials are also suitably used in electron-blocking layers. Specific examples of compounds used as hole-injection transport materials are shown below, but are not limited to these.

[0080]

[0081] Among the hole transport materials listed, HT16 to HT18 can reduce the driving voltage when used in the layer in contact with the anode. HT16 is widely used in organic light-emitting devices. HT2, HT3, HT4, HT5, HT6, HT10, and HT12 may be used in the organic compound layer adjacent to HT16. Furthermore, multiple materials may be used in a single organic compound layer.

[0082] <Other configurations of the organic light-emitting element> The organic light-emitting element comprises a first electrode 2, an organic compound layer 3, and a second electrode 4 on a substrate 1. The aforementioned sealing layer may be provided on the second electrode 4, and further, a color filter, microlens, etc. If a color filter is provided, a planarization layer may be provided between it and the protective layer. The planarization layer can be made of acrylic resin or the like. The same applies when a planarization layer is provided between the color filter and the microlens.

[0083] [Color Filter] A color filter may be provided on top of the protective layer. For example, a color filter that takes into account the size of the organic light-emitting element may be provided on a separate substrate and bonded to the substrate on which the organic light-emitting element is provided, or a color filter may be patterned on the protective layer as described above using photolithography technology. The color filter may be made of polymer.

[0084] [Planarizing Layer] A planarizing layer may be provided between the color filter and the protective layer. The planarizing 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 its purpose. The planarizing layer may be composed of an organic compound, and may be low molecular weight or high molecular weight, but high molecular weight is preferred.

[0085] The planarization layer may be provided above or below the color filter, and its constituent materials may be the same or different. Specifically, examples include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, urea resin, etc.

[0086] [Microlenses] Organic light-emitting elements may have optical components such as microlenses on their light-emitting side. Microlenses may be made of acrylic resin, epoxy resin, etc. Microlenses may be used to increase the amount of light extracted from the organic light-emitting element or to control the direction of the extracted light. Microlenses may have a hemispherical shape. If they have a hemispherical shape, among the tangents tangent to the hemisphere, there is a tangent parallel to the insulating layer, and the point of contact between that tangent and the hemisphere is the vertex of the microlens. The vertex of the microlens can be similarly determined in any cross-sectional view. That is, among the tangents tangent to the semicircle of the microlens in the cross-sectional view, there is a tangent parallel to the insulating layer, and the point of contact between that tangent and the semicircle is the vertex of the microlens.

[0087] Furthermore, the midpoint of a microlens can also be defined. In the cross-section of a microlens, a line segment can be imagined from the point where one arc ends to the point where another arc ends, and the midpoint of this line segment can be called the midpoint of the microlens. The cross-section used to determine the vertices and midpoints may be a cross-section perpendicular to the insulating layer.

[0088] [Opposite Substrate] An opposite substrate may be provided on the planarization layer. The opposite substrate is called an opposite substrate because it is provided in a position corresponding to the aforementioned substrate. The constituent material of the opposite substrate may be the same as that of the aforementioned substrate. The opposite substrate may be a second substrate if the aforementioned substrate is the first substrate.

[0089] [Method for producing the organic compound layer] The organic compound layer can be produced using dry processes such as vacuum deposition, ionization deposition, sputtering, and plasma deposition. Alternatively, a wet process can be used in place of a dry process, in which the compound is dissolved in a suitable solvent and the layer is formed by a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.).

[0090] When layers are formed using methods such as vacuum deposition or solution coating, crystallization is less likely to occur, resulting in excellent stability over time. Furthermore, when forming films using coating methods, it is possible to combine the film with an appropriate binder resin.

[0091] Examples of the binder resins mentioned above include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, and urea resin.

[0092] Furthermore, these binder resins may be used individually as homopolymers or copolymers, or as a mixture of two or more types. Additionally, known additives such as plasticizers, antioxidants, and UV absorbers may be used in combination as needed.

[0093] <Organic Light-Emitting Device> [Pixel Circuit] The organic light-emitting device equipped with the organic light-emitting element of the present invention may have a pixel circuit connected to the organic light-emitting element. The pixel circuit may be an active matrix type that independently controls the emission of light from multiple organic light-emitting elements. The active matrix type circuit may be voltage programmed or current programmed. The drive circuit has a pixel circuit for each pixel. The pixel circuit may have a transistor that controls the luminescence brightness of the organic light-emitting element, a transistor that controls the luminescence timing, a capacitor that holds the gate voltage of the transistor that controls the luminescence brightness, and a transistor for connecting to GND without going through the light-emitting element.

[0094] The organic light-emitting device has a display area and a peripheral area arranged around the display area. The display area has a pixel circuit, and the peripheral area has a display control circuit. The mobility of the transistors constituting the pixel circuit may be smaller than the mobility of the transistors constituting the display control circuit.

[0095] The slope of the current-voltage characteristics of the transistors constituting the pixel circuit may be smaller than the slope of the current-voltage characteristics of the transistors constituting the display control circuit. The slope of the current-voltage characteristics can be measured using the so-called Vg-Ig characteristic.

[0096] The transistors that make up the pixel circuit are the transistors connected to the organic light-emitting element.

[0097] [Pixels] The organic light-emitting device has a plurality of pixels. Each pixel has sub-pixels that emit light of a different color from the others. The sub-pixels may each have, for example, RGB light-emitting colors.

[0098] A pixel emits light in a region also called the pixel aperture. This region is the same as the first region. 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.

[0099] The distance between subpixels may be 10 μm or less, and specifically, it may be 8 μm, 7.4 μm, or 6.4 μm.

[0100] Pixels can take on known arrangements in a plan view. For example, they may be arranged in a stripe pattern, delta pattern, pentile pattern, or Bayer pattern. The shape of subpixels in a plan view may be any known shape. For example, rectangles, rhombuses, hexagons, etc. Of course, even if it is not a precise shape, if it is close to a rectangle, it is included in the category of rectangles. The shape of subpixels and the pixel arrangement can be used in combination.

[0101] [Applications of Organic Light-Emitting Devices] The organic light-emitting device according to the present invention can be used as a component of display devices and lighting devices. Other applications include exposure light sources for electrophotographic image forming apparatuses, backlights for liquid crystal display devices, and light-emitting devices with a color filter in a white light source.

[0102] The display device may also be an image information processing device that has an image input unit for receiving image information from an area CCD, linear CCD, memory card, etc., an information processing unit for processing the input information, and displays the input image on the display unit.

[0103] The display unit of the imaging device or inkjet printer may have a touch panel function. The driving method for this touch panel function may be infrared, capacitive, resistive, or electromagnetic induction, and is not particularly limited. The display device may also be used as the display unit of a multifunction printer.

[0104] Next, the display device according to this embodiment will be described with reference to the drawings.

[0105] Figures 3A and 3B are schematic cross-sectional diagrams showing an example of a display device having an organic light-emitting element of the present invention and a transistor connected to this organic light-emitting element.

[0106] Figure 3A shows an example of a pixel, which is a component of the display device according to this embodiment. The pixel has sub-pixels 20. The sub-pixels are divided into 20R, 20G, and 20B based on their light emission. The light emission color may be distinguished by the wavelength emitted from the light-emitting layer, or the light emitted from the sub-pixel may be selectively transmitted or color-converted by a color filter or the like. Each sub-pixel has a first electrode 12 which is a reflective electrode, an insulating layer 13 covering the end of the first electrode 12, an organic compound layer 14 covering the first electrode 12 and the insulating layer 13, a second electrode 15, a protective layer 16, and a color filter 17 on an interlayer insulating layer 11. The first electrode 12, the organic compound layer 14, and the second electrode 15 constitute the organic light-emitting element 18 of this embodiment.

[0107] The interlayer insulating layer 11 may have transistors or capacitive elements placed in the layer below or inside it. The transistor and the first electrode 12 may be electrically connected via a contact hole or the like (not shown).

[0108] The insulating layer 13 is also called a bank or pixel separation layer. It covers the end of the first electrode 12 and is arranged to surround the first electrode 12. The portion where the insulating layer 13 is not present is in contact with the organic compound layer 14 and becomes the light-emitting region.

[0109] The second electrode 15 may be a transparent electrode, a reflective electrode, or a semi-transparent electrode.

[0110] The protective layer 16 reduces the penetration of moisture into the organic compound layer 14. Although the protective layer 16 is shown as a single layer, it may be made up of multiple layers. Each layer may contain an inorganic compound layer and an organic compound layer.

[0111] The color filters 17 are classified into 17R, 17G, and 17B according to their color. The color filters may be formed on a planarization film (not shown). Alternatively, the color filters may have a resin protective layer (not shown). The color filters 17 may also be formed on a protective layer 16. Or, they may be bonded together after being placed on an opposing substrate such as a glass substrate.

[0112] The display device in Figure 3B includes an organic light-emitting element 36 and a TFT 28 as an example of a transistor. Specifically, a substrate 21 made of glass, silicon, or the like, and an insulating layer 22 are provided on top of it. 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 arranged on the insulating layer 22. An insulating film 29 is provided on top of the TFT 28, and the anode 31 and the source electrode 27 constituting the organic light-emitting element 36 are connected via contact holes 30 provided in the insulating film 29.

[0113] Furthermore, 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 configuration shown in Figure 3B. In other words, it is sufficient for either the anode 31 or cathode 33 to be electrically connected to either the source electrode 27 or the drain electrode 26. TFT 28 refers to a thin-film transistor.

[0114] A first protective layer 34 and a second protective layer 35 are provided on the cathode 33 to reduce the degradation of the organic light-emitting element.

[0115] In the display device shown in Figure 3B, a transistor is used as the switching element, but other switching elements may be used instead.

[0116] Furthermore, the transistor used in the display device shown in Figure 3B is not limited to a TFT having an active layer on the insulating surface of the substrate, but may also be a transistor using a single-crystal silicon wafer. In addition, the active layer may be a non-single-crystal silicon such as amorphous silicon or microcrystalline silicon, or a non-single-crystal oxide semiconductor such as indium zinc oxide or indium gallium zinc oxide.

[0117] The transistors included in the display device shown in Figure 3B may be formed within a substrate such as a Si substrate. Here, "formed within a substrate" means that the transistors are fabricated by processing the substrate itself, such as a Si substrate. In other words, having transistors within a substrate can be seen as the substrate and transistors being formed as a single unit.

[0118] The organic light-emitting element according to this embodiment has its luminescence controlled by a TFT, which is an example of a switching element, and by providing multiple organic light-emitting elements on one surface, an image can be displayed according to the luminescence of each element. The switching element according to this embodiment is not limited to a TFT, but may also be a transistor made of low-temperature polysilicon, or an active matrix driver formed on a substrate such as a Si substrate. "On the substrate" can also mean "within the substrate." Whether to provide a transistor within the substrate or to use a TFT is selected depending on the size of the display area; for example, if the size is about 0.5 inches, it is preferable to provide the organic light-emitting element on a Si substrate.

[0119] Figure 4 is a schematic diagram showing an example of a display device according to this embodiment. The display device 1000 may have a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 107, and a battery 1008 between an upper cover 1001 and a lower cover 1009. Flexible printed circuits FPCs 1002 and 1004 are connected to the touch panel 1003 and the display panel 1005. Transistors are printed on the circuit board 107. The battery 1008 does not need to be provided if the display device is not a portable device, or it may be provided in a different location even if it is a portable device.

[0120] The display device according to this embodiment may have a color filter having red, green, and blue colors. The color filter may have the red, green, and blue colors arranged in a delta array.

[0121] The display device according to this embodiment may be used in the display unit of a mobile terminal. In that case, it may have both display and operation functions. Examples of mobile terminals include smartphones and other mobile phones, tablets, and head-mounted displays.

[0122] The display device according to this embodiment may be used in the display unit of an imaging device having an optical unit with a plurality of lenses and an image sensor that receives light that has passed through the optical unit. The imaging device may have a display unit that displays information acquired by the image sensor. Furthermore, the display unit may be a display unit exposed to the outside of the imaging device or a display unit located inside the viewfinder. The imaging device may be a digital camera or a digital video camera.

[0123] Figure 5A is a schematic diagram showing an example of an imaging device according to this embodiment. The imaging device 1100 may include 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 the image to be captured, but also environmental information, imaging instructions, etc. Environmental information may include the intensity of ambient light, the direction of ambient light, the speed at which the subject is moving, the possibility of the subject being obscured by an obstruction, etc.

[0124] Since the optimal timing for imaging is very short, it is best to display the information as quickly as possible. Therefore, it is preferable to use a display device using the organic light-emitting element of the present invention, because organic light-emitting elements have a fast response speed. Display devices using organic light-emitting elements can be used more suitably than liquid crystal display devices, which require a fast display speed.

[0125] The imaging device 1100 has an optical section (not shown). The optical section has multiple lenses that form an image on the image sensor housed in the housing 1104. The focus can be adjusted by adjusting the relative positions of the multiple lenses. This operation can also be performed automatically. The imaging device may also be called a photoelectric converter. The photoelectric converter does not capture images sequentially, but may include imaging methods such as detecting the difference from the previous image or extracting from an image that is always being recorded.

[0126] Figure 5B is a schematic diagram showing an example of an electronic device according to this embodiment. 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 response unit. The operation unit may also be a biometric recognition unit that recognizes fingerprints to unlock or otherwise perform actions. 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. Images captured by the camera function are displayed on the display unit. Examples of electronic devices include smartphones and laptop computers.

[0127] Figures 6A and 6B are schematic diagrams showing an example of a display device according to the present invention. Figure 6A is 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 frame 1301 and the base 1303 that supports the display unit 1302 are included. The base 1303 is not limited to the form shown in Figure 6A. The lower edge of the frame 1301 may also serve as the base. Furthermore, 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.

[0128] Figure 6B is a schematic diagram showing another example of a display device according to the present invention. The display device 1310 in Figure 6B is configured to be foldable 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 light-emitting devices using organic light-emitting elements according to the present invention. The first display unit 1311 and the second display unit 1312 may be a single display device without seams. 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 each display different images, or the first and second display units may together display a single image.

[0129] Figure 7A is a schematic diagram showing an example of a lighting device according to the present invention. The lighting device 1400 includes 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 from the light source 1402, such as for lighting up, and deliver light over a wide area. The optical filter 1404 and the light diffusion unit 1405 may be provided on the light-emitting side of the lighting. A cover may be provided on the outermost part as needed.

[0130] The lighting device is, for example, a device for illuminating a room. The lighting device may emit white light, daylight white light, or any other color from blue to red. It may also have a dimming circuit to adjust the brightness. 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 to DC voltage. White light has a color temperature of 4200K, and daylight white light has a color temperature of 5000K. The lighting device may also have a color filter.

[0131] Furthermore, the lighting device according to the present invention may have a heat dissipation section. The heat dissipation section releases heat from inside the device to the outside, and examples include metals with high specific heat, liquid silicone, etc.

[0132] Figure 7B is a schematic diagram of an automobile, which is an example of a mobile body according to the present invention. The automobile has a taillight, which is an example of a lighting device. The automobile 1500 may have a taillight 1501, and the taillight may be configured to illuminate when the brakes are applied or the like.

[0133] The tail lamp 1501 has an organic light-emitting element according to the present invention. The tail lamp may have a protective member to protect the organic light-emitting element. The protective member has a certain degree of strength and can be made of any transparent material, but it is preferably made of polycarbonate or the like. A frangic acid derivative, an acrylonitrile derivative, or the like may be mixed with the polycarbonate.

[0134] The automobile 1500 may have a body 1503 and windows 1502 attached thereto. The windows may be transparent displays, unless they are windows for checking the front and rear of the automobile. The transparent displays have organic light-emitting elements according to the present invention, and the constituent materials such as electrodes of the organic light-emitting elements are made of transparent members.

[0135] The mobile body according to the present invention may be a ship, aircraft, drone, etc. The mobile body has a body and a light fixture installed on the body. The light fixture emits light to indicate the position of the body. The light fixture has an organic light-emitting element according to the present invention.

[0136] Referencing Figures 8A and 8B, examples of applications of the display devices of each embodiment described above will be explained. The display device can be applied to systems that can be worn as wearable devices such as smart glasses, HMDs, and smart contact lenses. The imaging display device used in such applications comprises an imaging device capable of photoelectric conversion of visible light and a display device capable of emitting visible light.

[0137] Figure 8A shows eyeglasses 1600 (smart glasses) according to one application example. An imaging device 1602, such as a CMOS sensor or SPAD, is provided on the front surface of the lens 1601 of the eyeglasses 1600. In addition, the display devices of each embodiment described above are provided on the back surface of the lens 1601.

[0138] The eyeglasses 1600 further include a control device 1603. The control device 1603 functions as a power supply that provides power to the imaging device 1602 and the display device according to each embodiment. The control device 1603 also controls the operation of the imaging device 1602 and the display device. The lens 1601 has an optical system formed therein for focusing light onto the imaging device 1602.

[0139] Figure 8B shows another embodiment of the eyeglasses 1610 (smart glasses). The eyeglasses 1610 have a control device 1612, which is equipped with an imaging device corresponding to the imaging device 1602 in Figure 8A and a display device. The lens 1611 has an optical system formed therein for projecting light emitted from the imaging device and the display device within the control device 1612, and an image is projected onto the lens 1611. The control device 1612 functions as a power supply to provide power to the imaging device and the display device, and also controls the operation of the imaging device and the display device. The control device may have a gaze detection unit that detects the wearer's gaze. Gaze detection may use infrared light. The infrared light emitter emits infrared light towards the eyeball of the user who is gazing at the displayed image. The imaging unit, which has a light-receiving element, detects the reflected light from the eyeball of the emitted infrared light, thereby obtaining an image of the eyeball. By having a reduction means that reduces the light from the infrared light emitter to the display unit in planar view, the deterioration of image quality is reduced.

[0140] The user's gaze towards a displayed image is detected from an image of the eyeball obtained by imaging with 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 the Purkinje image obtained by the reflection of the irradiated light from the cornea can be used. More specifically, gaze detection processing based on the pupil-corneal reflection method is performed. Using the pupil-corneal reflection method, the user's gaze is detected by calculating a gaze vector representing the orientation (rotation angle) of the eyeball based on the pupil image and the Purkinje image contained in the image of the eyeball.

[0141] The display device according to the present invention includes an imaging device having a light-receiving element, and the display image of the display device may be controlled based on the user's gaze information from the imaging device. Specifically, the display device determines a first field of view area that the user is fixated on, and a second field of view area other than the first field of view area, based on the gaze information. The first and second field of view areas may be determined by the control device of the display device, or they may be determined by an external control device and received. 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.

[0142] Furthermore, the display area has a first display area and a second display area different from the first display area, and based on gaze information, the area with higher priority is determined from the first display area and the second display area. The first and second view areas may be determined by the control device of the display device, or they may be determined by an external control device and received. The resolution of the high-priority area may be controlled to be higher than the resolution of the areas other than the high-priority area. In other words, the resolution of areas with relatively lower priority may be lower.

[0143] Furthermore, AI may be used to determine the primary field of view area and high-priority areas. The AI ​​may be a model configured to estimate the angle of line of sight and the distance to the target object at the end of the line of sight from the image of the eye, using the image of the eye and the direction the eye was actually looking in the image as training data. The AI ​​program may be installed in the display device, the imaging device, or an external device. If installed in an external device, it will be transmitted to the display device via communication.

[0144] When display control is based on visual detection, this method is preferably applicable to smart glasses that further include an imaging device for capturing images of the surrounding environment. The smart glasses can display the captured external information in real time.

[0145] Figure 9A is a schematic diagram showing an example of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus 1700 is an electrophotographic image forming apparatus and includes a photoreceptor 1707, an exposure light source 1708, a charging unit 1710, a developing unit 1711, a transfer unit 1712, a transport roller 1713, and a fuser 1715. Light 1709 is irradiated from the exposure light source 1708, and an electrostatic latent image is formed on the surface of the photoreceptor 1707. This exposure light source 1708 has an organic light-emitting element according to the present invention. The developing unit 1711 has toner or the like. The charging unit 1710 charges the photoreceptor 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 fuser 1715 fixes the image formed on the recording medium 1714.

[0146] Figures 9B and 9C are diagrams showing the exposure light source 1708, and are schematic diagrams showing how multiple light-emitting units 1726 are arranged on a long substrate. The arrow 1727 is parallel to the axis of the photoreceptor and represents the column direction in which the organic light-emitting elements are arranged. This column direction is the same as the direction of the axis in which the photoreceptor 1707 rotates. This direction can also be called the long axis direction of the photoreceptor 1707. Figure 9B shows a configuration in which the light-emitting units 1726 are arranged along the long axis direction of the photoreceptor 1707. Figure 9C shows a different configuration from Figure 9B, in which the light-emitting units 1726 are arranged alternately in the column direction in the first column and the second column, respectively. The first column and the second column are arranged at different positions in the row direction. In the first column, multiple light-emitting units 1726 are arranged at intervals. In the second column, light-emitting units 1726 are located at positions corresponding to the intervals between the light-emitting units 1726 in the first column. In other words, multiple light-emitting units 1726 are also arranged at intervals in the row direction. The arrangement in Figure 9C can also be described as a grid arrangement, a houndstooth arrangement, or a checkerboard pattern.

[0147] As described above, by using the apparatus employing the organic light-emitting element according to the present invention, it becomes possible to display images with good quality and stable display even for extended periods.

[0148] The present invention will be described below with reference to examples. However, the present invention is not limited to these examples. Furthermore, the compounds used in these examples were synthesized according to known synthesis methods.

[0149] (Examples 1 and 2) In these examples, an organic light-emitting element with a top-emission structure was fabricated on a substrate in which an anode as the first electrode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and a cathode as the second electrode were sequentially formed.

[0150] A 40 nm layer of Ti was deposited on a glass substrate using sputtering, and then patterned using photolithography, resulting in an electrode area of ​​3 mm². ２ The anode was formed and then cleaned.

[0151] Next, the electrode-equipped substrate prepared above is attached to the vacuum deposition apparatus (manufactured by ULVAC), and after preparing for the deposition of the deposition material, 1.33 × 10－４ Pa(1 × 10) －６ The chamber was evacuated to Torr. After that, the inside of the chamber was cleaned with UV / ozone. Then, each layer was deposited in the layer configuration shown in Table 1 using the following method. With this layer configuration, the optical path length (optical distance) L between the anode and cathode satisfies equation (1) above.

[0152] As for the organic compound layer, first, HT16, as previously exemplified, was deposited to a thickness of 8 nm to form a hole injection layer. Next, HT1, as previously exemplified, was deposited to a thickness of 6 nm to form a hole transport layer. Next, HT7, as previously exemplified, was deposited to a thickness of 10 nm to form an electron blocking layer. Next, EM1 and B-1, as previously exemplified, were co-deposited at deposition rates of 0.99 Å / s and 0.01 Å / s, respectively, to form a light-emitting layer with a thickness of 20 nm. Next, ET8, as previously exemplified, was deposited to a thickness of 6 nm to form a hole blocking layer. Next, ET1, as previously exemplified, was deposited to a thickness of 10 nm to form an electron transport layer.

[0153] Next, as the cathode (second electrode), a layer with a mass ratio of Ag to Li of 1:0.0001 was formed with a thickness of 10 nm using a co-evaporation method of Ag and Li. A Li dispenser was used for the Li deposition.

[0154] Finally, the substrate was transferred to a glove box and sealed with a glass cap containing a desiccant in a nitrogen atmosphere to obtain the organic light-emitting element of Example 1. The configuration from the hole injection layer to the second electrode is shown in Table 1.

[0155] The organic light-emitting element of Example 2 was fabricated in the same manner as the organic light-emitting element of Example 1, except that the film thickness of each layer of the organic compound layer was changed to the film thickness shown in Table 1. With this layer configuration, the optical path length L between the anode and cathode does not satisfy the above formula (1).

[0156]

[0157] (Examples 3 to 4) The organic light-emitting element of Example 3 was fabricated by changing the electron transport layer in Example 1 as shown in Table 2. Furthermore, the organic light-emitting element of Example 4 was fabricated in the same manner as in Example 3, except that an electron injection layer was formed on the cathode side of the electron transport layer, as shown in Table 3. Since the electron injection layer has a thin film thickness of 1 nm, the optical path length L between the anode and cathode satisfies the above formula (1).

[0158]

[0159] (Examples 5 to 6) The light-emitting material of the light-emitting layer in Example 1 was changed to B-63 below, and its content and the material of the hole block layer were changed as shown in Table 3 to produce the organic light-emitting device of Example 5. Similarly, the light-emitting material and content of the light-emitting layer were changed to produce the organic light-emitting device of Example 6. The LUMO of the host material and light-emitting material of the light-emitting layer used in Examples 1, 5, and 6 is shown in Table 4.

[0160]

[0161]

[0162]

[0163] (Examples 7 to 10) Organic light-emitting devices were fabricated in the same manner as in Example 1, except that the Li concentration of the cathode was changed to the configuration shown in Table 5.

[0164] (Examples 11 to 25) Organic light-emitting devices were fabricated in the same manner as in Example 1, except that the cathode film thickness was changed to the configuration shown in Table 5.

[0165] (Examples 26 to 105) Organic light-emitting devices were fabricated in the same manner as in Examples 1 to 20, except that the cathode of Examples 1 to 20 was used as the first cathode, an Ag layer was deposited on top of the first cathode as the second cathode by vacuum deposition, and the thickness of each layer was changed to the thickness shown in Tables 5 to 7.

[0166] (Example 106) An organic light-emitting element was fabricated in the same manner as in Example 26, except that a 2 μm thick silicon nitride film sealing layer was formed on the second cathode of Example 26 by CVD.

[0167] (Example 107) An organic light-emitting element was fabricated in the same manner as in Example 106, except that a silicon nitride film with a thickness of 2 μm was sequentially deposited on the sealing layer of Example 106 by the ALD method as a second sealing layer, and a silicon nitride film with a thickness of 2 μm was sequentially deposited on the sealing layer of Example 106 by the CVD method.

[0168] (Comparative Examples 1 and 2) Organic light-emitting devices of Comparative Examples 1 and 2 were fabricated in the same manner as in Example 26, except that the materials of the hole blocking layer, electron transport layer, and first cathode were changed to the materials shown in Table 7.

[0169] (Comparative Example 3) An organic light-emitting element was fabricated in the same manner as in Comparative Example 2, except that an electron injection layer made of LiF similar to that in Example 4 was formed on the electron transport layer.

[0170] (Comparative Examples 4 to 6) Organic light-emitting devices were fabricated in the same manner as in Example 1, except that the hole blocking layer and electron transport layer were changed to the materials shown in Table 7. In Comparative Example 5, ET25, shown below, was used as the material for the electron transport layer.

[0171]

[0172] (Comparative Example 7) An organic light-emitting element was fabricated in the same manner as in Example 2, except that the composition of each organic layer and the second electrode in Example 2 was changed to the same materials as in Comparative Example 2, as shown in Table 7.

[0173] (Comparative Example 8) An organic light-emitting element was fabricated in the same manner as in Example 4, except that the material of the hole blocking layer was changed to BAlq and the material of the electron injection layer was changed to ET1 and Li (mass ratio 99:1).

[0174] (Comparative Example 9) An organic light-emitting element was fabricated in the same manner as in Example 1, except that the Li content of the cathode was changed to 15.0% by mass as shown in Table 7.

[0175] (Comparative Example 10) An organic light-emitting element was fabricated in the same manner as in Example 1, except that the materials for the electron transport layer and the cathode are shown in Table 7.

[0176] The configuration of each organic light-emitting element is shown in Tables 5 to 7. The optical path length L between the anode and cathode is indicated by "○" if it satisfies formula (1) above, and by "×" if it does not.

[0177]

[0178]

[0179]

[0180] (Evaluation Method) A voltage application device was connected to the obtained organic light-emitting element, and its characteristics were evaluated. Current-voltage characteristics were measured using a Hewlett-Packard 4140B microcurrent meter, and chromaticity was evaluated using a Topcon SR-3. Luminous intensity was measured using a Topcon BM7. These results are shown in Table 8 as relative values ​​with the result of Comparative Example 1 set to 1.

[0181] Furthermore, the initial brightness is 2000 cd / m². ２ A continuous operation test was conducted, and the degradation rate of brightness after 100 hours was measured. These results are shown in Table 8 as relative values, with the result of Comparative Example 1 set to 1.

[0182] (Evaluation Results) The current-voltage characteristics were also measured after 1000 hours of storage in a constant temperature chamber at 85°C. Table 8 shows whether or not there was an increase in the drive voltage compared to the current-voltage characteristics before storage at 85°C.

[0183]

[0184] A comparison between Example 1 and Example 2, and between Comparative Example 2 and Comparative Example 7, shows that when the optical path length between the first electrode and the second electrode satisfies equation (1) with respect to the peak wavelength λ during emission, an organic light-emitting element with higher luminescence efficiency can be obtained.

[0185] A comparison of Example 3 with Comparative Examples 4 and 5 shows that the configuration using an electron transport layer made of ET24 with a 2,2'-bipyridine skeleton has a lower drive voltage, higher luminous efficiency and drive durability compared to configurations using Alq3 or ET25.

[0186] Furthermore, a comparison between Example 1 and Example 3 shows that compound ET1, which has a 1,10-phenanthroline skeleton in the electron transport layer, exhibits even greater stability during operation than ET24, which has a 2,2'-bipyridine skeleton. While electron injection and suppression of Li diffusion can also be achieved by introducing a Li-doped layer of a compound with a 1,10-phenanthroline skeleton as the electron injection layer, the efficiency decreases because the electron injection layer absorbs light in the visible light region.

[0187] A comparison of Examples 1 and 4, and Comparative Examples 2 and 3, shows that in the conventional configuration, a Li compound layer (electron injection layer) is necessary between the electron transport layer and the second electrode to improve device performance, but in the configuration of the present invention, it does not affect device performance and is therefore unnecessary.

[0188] Comparative Example 6, although its hole-blocking layer is BAlq rather than a condensed hydrocarbon compound, exhibits a lower driving voltage, higher luminous efficiency, and greater driving durability compared to Comparative Example 1. Furthermore, no voltage increase is observed during high-temperature storage. However, as with Comparative Example 4, it is clear that using ET10, a condensed polycyclic hydrocarbon compound, further enhances luminous efficiency and device stability during operation.

[0189] Furthermore, from Examples 5 to 6, it can be seen that even if the hole-blocking material is a condensed hydrocarbon compound, if the LUMO of the light-emitting material is closer to the vacuum level than the LUMO of the host, the recombination region moves to the first electrode side interface of the light-emitting layer, and the device performance deteriorates.

[0190] Comparing Examples 1, 7 to 10 and Comparative Example 4, it can be seen that in the present invention, when the Li concentration in the second electrode 4 is 0.01% by mass or more and 10% by mass or less, Li imparts electron injection properties to the second electrode while not affecting the metal lattice structure. Therefore, the Li concentration does not affect the device performance, and the device consistently exhibits better performance than Comparative Example 4. Similar results were obtained in Examples 11 to 105. Furthermore, in Comparative Example 9, where the Li concentration exceeds 10% by mass, it can be seen that the luminous efficiency decreases due to Li diffusion, and the device stability during operation also deteriorates.

[0191] Comparing Examples 1, 11, 16, 21 and Comparative Example 4, it can be seen that in the present invention, the current efficiency can be improved by increasing the thickness of the second electrode. This is because the reflectivity increases as the second electrode becomes thicker, allowing for a stronger resonance effect to be obtained before light extraction. The effect of the thickness of the second electrode on the device performance was similar in Examples 7 to 10, 12 to 15, 17 to 20, and 22 to 25.

[0192] A comparison of Examples 1, 26, 31, 36, and 41 shows that when a multilayer electrode consisting of a Li-containing layer and a transition metal layer is used as the second electrode, the device stability is improved by suppressing the diffusion of Li outside the device.

[0193] Furthermore, Figure 2 shows the absorption spectra in the visible region for the second electrode configuration of Example 26 and the second electrode configuration of Comparative Example 4. The absorption spectra were calculated by measuring the transmittance and reflectance using "SolidSpec3700" (Shimadzu Corporation) and using the following formula: Absorption (%) = 100 - Transmittance (%) - Reflectance (%)

[0194] The second electrode configuration of Example 26 shows a lower light absorption rate in the visible region compared to the second electrode configuration of Comparative Example 4, and is equivalent to that of Ag. This indicates that the configuration of the present invention reduces inhibition due to absorption during light extraction and improves luminescence efficiency. The effects of the presence or absence and film thickness of the transition metal layer on the device performance were similar in Examples 7 to 10, 27 to 30, 32 to 35, 37 to 40, and 42 to 105.

[0195] A comparison of Examples 26 with 106 and 107 shows that adding a thin film sealing layer on the second electrode provides both moisture intrusion prevention and Li diffusion suppression, thereby improving the stability of the device.

[0196] Comparative Example 10 improves the transmittance of the second electrode and the light extraction efficiency by doping the second electrode with Cs, thereby providing electron injection properties to the second electrode. The ET1 contained in the electron transport layer has the structure of general formula [1], but since Cs does not form a chelate complex with ET8, Cs diffusion occurs. On the other hand, in Example 1, Li is used instead of Cs as the material contained in the second electrode, and the electron transport layer is formed with ET1 having the structure shown in general formula [1], thereby providing electron injection properties to the second electrode, reducing light absorption in the visible region, and further improving the stability of the device by suppressing the diffusion of doped Li.

[0197] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0198] This application claims priority based on Japanese Patent Application No. 2025-016570, filed on February 4, 2025, and all of its contents are incorporated herein by reference.

[0199] 2, 12, 22 First electrode 3, 14, 32 Organic compound layer 3a Electron transport layer 4, 15, 33 Second electrode 14, 32 Organic compound layer 18, 36 Organic light-emitting element 1000, 1300, 1310 Display device 1100 Imaging device 1104, 1203, 1313 Housing 1200 Electronic equipment 1201, 1302, 1311, 1312 Display unit 1707 Photoreceptor 1708 Exposure light source

Claims

1. An organic light-emitting element comprising a first electrode, a second electrode, and an organic compound layer disposed between the first electrode and the second electrode, wherein the organic compound layer comprises at least a light-emitting layer and an electron transport layer, and the electron transport layer is in contact with the second electrode, characterized in that the second electrode has a layer containing Li, and the electron transport layer contains an organic compound A having a structure represented by the following general formula [1]. [In the above general formula [1], A and B are each substituted or unsubstituted heterorings containing N, and heterorings A and B may be fused such that N is positioned on the outside.] 2. The organic light-emitting element according to claim 1, characterized in that the structure represented by the general formula [1] is a 2,2'-bipyridine skeleton.

3. The organic light-emitting element according to claim 2, characterized in that the structure represented by the general formula [1] is a 1,10-phenanthroline skeleton.

4. The organic light-emitting element according to claim 1, characterized in that the organic compound A has a plurality of structures represented by the general formula [1] within its molecule.

5. The organic light-emitting element according to claim 1, characterized in that the second electrode is made of at least an alloy of Ag and Li.

6. The organic light-emitting element according to claim 1, characterized in that the concentration of Li contained in the second electrode is 0.01% by mass or more and 10% by mass or less.

7. The organic light-emitting element according to claim 1, characterized in that the concentration of Li contained in the second electrode is 0.01% by mass or more and 3% by mass or less.

8. The organic light-emitting element according to claim 1, characterized in that the organic light-emitting element extracts light from the second electrode side.

9. The organic light-emitting element according to claim 8, characterized in that a resonator structure is formed by the first electrode being reflective and the second electrode being reflective and transparent to light emitted from the light-emitting layer.

10. The organic light-emitting element according to claim 9, characterized in that the optical distance L between the first electrode and the second electrode satisfies the following equation (1) with respect to the maximum peak wavelength λ during emission of light from the light-emitting layer and the sum of the phase shifts φ [rad] when light of the maximum peak wavelength λ is reflected at each electrode interface: (-1-(φ / π))×(λ / 4) < L < (1-(φ / π))×(λ / 4) (1) 11. The organic light-emitting element according to claim 1, characterized in that the thickness of the electron transport layer is 5 nm or more and 20 nm or less.

12. The organic light-emitting element according to claim 1, characterized in that the second electrode is a multilayer electrode having a further layer made of a transition metal on the side opposite to the electron transport layer.

13. The organic light-emitting element according to claim 1, characterized in that there is no LiF layer between the second electrode and the electron transport layer.

14. The organic light-emitting element according to claim 1, characterized in that the electron transport layer is in contact with a hole-blocking layer made of a condensed polycyclic hydrocarbon compound on the first electrode side.

15. The organic light-emitting element according to claim 1, wherein the light-emitting layer comprises a host material and a light-emitting material, and the LUMO of the light-emitting material is further from the vacuum level than the LUMO of the host material.

16. The organic light-emitting element according to claim 1, characterized in that a sealing layer is provided on the second electrode of the organic light-emitting element.

17. A display device comprising a display unit having an organic light-emitting device according to any one of claims 1 to 16, and a housing on which the display unit is provided.

18. A photoelectric conversion device comprising an image sensor that receives light and a display unit that displays an image captured by the image sensor, wherein the display unit has an organic light-emitting device as described in any one of claims 1 to 16.

19. An electronic device comprising: a display unit having an organic light-emitting device as described in any one of claims 1 to 16; a housing on which the display unit is provided; and a communication unit provided in the housing for communicating with the outside.

20. A wearable device comprising: a display unit having an organic light-emitting device according to any one of claims 1 to 16; an optical system for focusing light from the display unit; and a control device for controlling the display of the display unit.

21. A lighting device comprising a light source having an organic light-emitting device as described in any one of claims 1 to 16, and a housing on which the light source is provided.

22. A mobile body characterized by having a display unit having an organic light-emitting device according to any one of claims 1 to 16, and a body on which the display unit is provided.

23. An image forming apparatus comprising a photoreceptor and an exposure light source for exposing the photoreceptor, wherein the exposure light source has an organic light-emitting device as described in any one of claims 1 to 16.

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