Light-emitting device and display device

Abstract

The present disclosure achieves cost reduction and mitigation of the effects of carrier leakage between pixels. A light-emitting device (10) includes a first electrode layer (21), light-emitting layers (25) of three colors, and a second electrode layer (29) stacked in this order, with various functional layers interposed therebetween. At least a portion of the functional layers is an integral common layer formed across the light-emitting layers of the respective colors, and the difference in intermediate gradation voltages in the current density-voltage characteristics of the light-emitting layers of the respective colors is 0.1-1.1 V.

Description

Light-emitting device and display device

[0001] The present disclosure relates to a light-emitting device and a display device.

[0002] BACKGROUND ART Organic electroluminescence (hereinafter also referred to as "organic EL") displays have been used as display devices in smartphones and tablet terminals because they are capable of displaying high-resolution images with low power consumption.

[0003] Organic EL displays typically have pixels of multiple colors, and the pixels of each color are fabricated by applying different light-emitting layer materials using a mask deposition method. In response to demands for higher resolution, the masks used in the mask deposition method are also becoming more precise, which increases the costs of fabricating and using the masks, and therefore the manufacturing costs of organic EL displays.

[0004] One known technique for achieving both high resolution and low cost in the manufacture of organic EL displays is to employ a common layer formed across the light-emitting layers of each color in a portion of the functional layers and electrode layers other than the light-emitting layers. This technique involves depositing the common layer over the entire surface, including the edge cover (also known as a bank), without using a mask. This technique significantly reduces the number of masks and their use in the manufacture of organic EL displays, thereby potentially leading to significant cost savings (see, for example, Patent Document 1).

[0005] Japanese Patent Application Publication No. 2015-26417

[0006] However, in the conventional techniques described above, the common layer is formed continuously across adjacent pixels or even pixels further apart. Therefore, carriers (holes and / or electrons) injected from the anode of a particular pixel into the light-emitting layer of that pixel may leak to adjacent pixels. Such carrier leakage may result in a phenomenon known as crosstalk, where a pixel intended to be in a non-lighted state lights up. Furthermore, the above-described carrier leakage may accelerate deterioration of the light-emitting layer of the pixel into which the leaked carriers flow.

[0007] An object of one embodiment of the present disclosure is to provide a technique that can reduce the manufacturing cost of a light-emitting device or a display device while suppressing the influence of carrier leakage between adjacent pixels.

[0008] In order to solve the above-described problems, a light-emitting device according to one aspect of the present disclosure includes a first electrode layer, which is either an anode layer or a cathode layer, a light-emitting layer, and a second electrode layer, which is the other of the anode layer and the cathode layer, stacked in this order in a stacking direction, and has a functional layer between the first electrode layer and the light-emitting layer and / or between the light-emitting layer and the second electrode layer, wherein two or more of the light-emitting layers that emit light of different colors are arranged adjacent to each other in a direction intersecting the stacking direction, and at least a part of the functional layer is formed as a common, integrated layer for two or more adjacent light-emitting layers, and when a voltage at a same current density at a middle gray level in the current density-voltage characteristics (hereinafter also referred to as "J-V characteristics") of the light-emitting layers is defined as a middle gray level voltage, a difference in the middle gray level voltage between two of the light-emitting layers that are adjacent to each other in a direction intersecting the stacking direction and emit light of different colors is 0.1 V or more and 1.1 V or less.

[0009] In order to solve the above problem, a display device according to an aspect of the present disclosure includes the above light-emitting device.

[0010] According to one aspect of the present disclosure, it is possible to reduce the manufacturing cost of a light-emitting device or a display device while suppressing the influence of carrier leakage between adjacent pixels.

[0011] FIG. 1 is a diagram schematically illustrating a configuration of a display device according to an embodiment of the present disclosure. FIG. 2 is a diagram schematically illustrating a main part of a layer configuration in one pixel portion of the display device of FIG. 1. FIG. 3 is a diagram for explaining an example of an arrangement of light-emitting layers according to the present disclosure. FIG. 4 is a flowchart illustrating an example of a manufacturing method of a display device according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of J-V characteristics including intermediate gradation voltages of light-emitting layers of each color according to an embodiment of the present disclosure. FIG. 6 is an equivalent circuit diagram of a light-emitting device according to an embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example of J-V characteristics including intermediate gradation voltages of a green light-emitting layer according to an embodiment of the present disclosure. FIG. 8 is a diagram illustrating the relationship between the J-V characteristics including intermediate gradation voltages between a green light-emitting layer and a blue light-emitting layer according to an embodiment of the present disclosure. FIG. 9 is a diagram illustrating the relationship between the J-V characteristics including intermediate gradation voltages between a green light-emitting layer and a red light-emitting layer according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example of J-V characteristics including the turn-on voltage of light-emitting layers of each color according to an embodiment of the present disclosure. FIG. 11 is a diagram illustrating the turn-on voltage according to an embodiment of the present disclosure. FIG. 12 is a diagram illustrating a method for determining the turn-on voltage according to an embodiment of the present disclosure. FIG. 13 is a diagram illustrating an example of J-V characteristics including the turn-on voltage of a green light-emitting layer according to an embodiment of the present disclosure. FIG. 14 is a diagram illustrating the relationship between the J-V characteristics including the turn-on voltage of a green light-emitting layer and a blue light-emitting layer according to an embodiment of the present disclosure. FIG. 1 is a diagram for explaining the relationship between the J-V characteristics, including the turn-on voltage, of a green light-emitting layer and a red light-emitting layer in an embodiment of the present disclosure. FIG. 2 is a diagram showing the J-V characteristics, including the turn-on voltage, of a green light-emitting layer in an example. FIG. 3 is a diagram showing the J-V characteristics, including the turn-on voltage, of a blue light-emitting layer in an example. FIG. 4 is a diagram showing the J-V characteristics, including the turn-on voltage, of a red light-emitting layer in an example. FIG. 5 is a diagram showing the J-V characteristics, including the turn-on voltage, of a green light-emitting layer in an example. FIG. 6 is a diagram showing the J-V characteristics, including the turn-on voltage, of a blue light-emitting layer in an example. FIG. 7 is a diagram showing the J-V characteristics, including the turn-on voltage, of a red light-emitting layer in an example. FIG. 8 is a diagram showing the emission spectrum of green light in an example.

[0012] An embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that, in this specification, for similar components related to different colors, a symbol indicating the color may be added to the symbol of the component. For example, a red component is indicated by the symbol R, a green component is indicated by the symbol G, and a blue component is indicated by the symbol B. Furthermore, in this specification, "to" means a range including both ends unless otherwise specified. Furthermore, the light-emitting device of the present disclosure includes a configuration having a light-emitting layer between two electrode layers, a first electrode layer and a second electrode layer, in the stacking direction. However, in the following embodiment, the first electrode layer will be described as an anode layer and the second electrode layer as a cathode layer. Note that, in this disclosure, the anode layer may be the second electrode layer and the cathode layer may be the first electrode layer.

[0013] [Display Device] FIG. 1 is a diagram schematically illustrating a configuration of a display device 100 according to an embodiment of the present disclosure. FIG. 1 illustrates a smartphone, which is an example of a display device. As illustrated in FIG. 1, the display device 100 includes a frame region NDA and a display region DA. The display region DA includes a plurality of pixels PIX. For example, the display region DA is configured by a plurality of pixels PIX regularly arranged within the display region. The pixels PIX include red subpixels RSP, green subpixels GSP, and blue subpixels BSP. Note that the pixels PIX may further include subpixels of colors other than the red subpixels RSP, green subpixels GSP, and blue subpixels BSP.

[0014] 2 is a diagram schematically showing the main part of the layer configuration in one pixel PIX of the display device 100 of FIG.

[0015] The substrate 110 is a glass substrate or a flexible substrate whose main component is a resin such as polyimide. The substrate 110 may be composed of, for example, two polyimide films and an inorganic film sandwiched between them. The cap layer 120 is a layer that covers the surface of the light-emitting device 10 and is, for example, a refractive index adjustment layer.

[0016] [Light-Emitting Device] As shown in Figure 2, the light-emitting device 10 has an anode layer 21, a light-emitting layer 25, and a cathode layer 29 stacked in this order in the stacking direction. The light-emitting layer 25 includes a blue light-emitting layer 25B, a green light-emitting layer 25G, and a red light-emitting layer 25R, which are arranged side by side in a direction intersecting the stacking direction (hereinafter also referred to as the "plane direction"). The anode layer 21 is also arranged in the plane direction to correspond to the light-emitting layers of each color, and includes an anode layer 21B corresponding to the blue light-emitting layer 25B, an anode layer 21G corresponding to the green light-emitting layer 25G, and an anode layer 21R corresponding to the red light-emitting layer 25R. Hereinafter, layers having the same function and arranged separately corresponding to the light-emitting colors of the light-emitting layers will also be referred to as "independent layers."

[0017] A hole injection layer 22, a hole transport layer 23, and an electron blocking layer 24 are disposed between the anode layer 21 and the light-emitting layer 25 in the stacking direction. The electron blocking layer 24 is adjacent to the light-emitting layer 25 in the stacking direction. The hole injection layer 22 and the hole transport layer 23 each form an integrated layer (hereinafter also referred to as a "common layer") common to the three light-emitting layers, i.e., the blue light-emitting layer 25B, the green light-emitting layer 25G, and the red light-emitting layer 25R, in the in-plane direction. The electron blocking layer 24 is composed of an independent layer and includes an electron blocking layer 24B corresponding to the blue light-emitting layer 25B, an electron blocking layer 24G corresponding to the green light-emitting layer 25G, and an electron blocking layer 24R corresponding to the red light-emitting layer 25R. The electron blocking layers 24B, 24G, and 25R all have different thicknesses.

[0018] In addition, a hole blocking layer 26, an electron transport layer 27, and an electron injection layer 28 are disposed between the light emitting layer 25 and the cathode layer 29 in the stacking direction. All of these are common layers.

[0019] The hole injection layer 22, the hole transport layer 23, the electron blocking layer 24, the hole blocking layer 26, the electron transport layer 27, and the electron injection layer 28 are all functional layers that contribute to at least one of the injection, movement, and generation of carriers (electrons or holes).

[0020] In this way, in the light emitting device 10, three light emitting layers, namely, the blue light emitting layer 25B, the green light emitting layer 25G, and the red light emitting layer 25R, which emit light of different colors, are arranged adjacent to each other in the surface direction. The light emitting device 10 also has a functional layer between the anode layer 21 and the light emitting layer 25, and also has a functional layer between the light emitting layer 25 and the cathode layer 29. Furthermore, the light emitting device 10 has a common layer as part of the functional layer.

[0021] Focusing on the collection of light-emitting layers in the surface direction, the light-emitting device 10 includes a group of light-emitting layers consisting of a blue light-emitting layer 25B, a green light-emitting layer 25G, and a red light-emitting layer 25R that emit light in three colors in one direction of the surface direction.

[0022] Here, when a regular arrangement of two or more light-emitting layers of two or more colors is established in each of two or more directions in the plane direction, two or more light-emitting layers of two or more colors arranged in one direction that satisfy the voltage difference requirement described below constitute a "group of light-emitting layers" in the present disclosure. For example, in an example of a Pentile arrangement shown in FIG. 3, blue light-emitting layers and green light-emitting layers are arranged alternately in a diagonal direction, or red light-emitting layers and green light-emitting layers are arranged alternately. Furthermore, blue light-emitting layers and red light-emitting layers are arranged alternately in the vertical or horizontal direction. When two light-emitting layers of two colors arranged in a diagonal direction satisfy the voltage difference requirement described below, the two light-emitting layers of two colors arranged in a diagonal direction constitute a "group of light-emitting layers." In this case, the voltage difference requirement does not need to be satisfied in the vertical and horizontal directions.

[0023] Furthermore, when two or more light-emitting layers of two or more colors are regularly arranged in each of the diagonal, vertical, and horizontal directions, and the arrangement of the light-emitting layers in the two or more directions satisfies the voltage requirements described below, each of the two or more light-emitting layers of two colors arranged in each of the two or more directions may be considered as a "group of light-emitting layers."

[0024] Each layer constituting the light-emitting device of the present disclosure will be further described below.

[0025] [Anode Layer] The anode layer is one of a pair of electrode layers, an anode and a cathode, and is an electrode layer for supplying holes to each layer constituting the light-emitting element in the present disclosure. In the present disclosure, the term "light-emitting element" refers to a laminated structure from a first electrode layer to a second electrode layer corresponding to a single light-emitting layer. The anode layer is conductive. Furthermore, the anode layer has optical properties, for example, of reflecting part of visible light and transmitting the rest. Typically, the anode layer includes both an electrode material that reflects visible light and an electrode material that transmits visible light.

[0026] To enhance hole injection properties, a material with a relatively high work function (e.g., a material with a work function of 4.5 eV or more) is preferably used as the material for the anode layer. Examples of electrode materials with a high work function include Pt (5.65 eV), Ir (5.25 eV), Ni (5.2 eV), Au (5.15 eV), and Pd (5.15 eV), as well as indium tin oxide (In—Sn—O).

[0027] Examples of electrode materials that reflect visible light include metal materials such as Al, Mg, Li, Ag, Pd, and Cu, as well as alloys of these metal materials (e.g., APC (Ag-Pd-Cu) alloy, etc.).

[0028] Examples of electrode materials that transmit visible light include thin films of transparent metal oxides (e.g., indium tin oxide, indium zinc oxide (In—Zn—O), and indium gallium zinc oxide (In—Ga—Zn—O)), thin films made of metal materials such as Al, Mg, and Ag, or alloys of these metal materials (e.g., Mg—Ag alloy), and nanowires (NW) made of these metal materials. Electrode materials that transmit visible light are also used for the cathode layer in top-emission light-emitting devices, which will be described later.

[0029] Among transparent metal oxides, indium tin oxide has a relatively high work function of 4.6 to 5.0 eV and is therefore suitable for use as a material for the anode layer. Furthermore, for the anode layer, a laminate (e.g., indium tin oxide / Ag) in which an indium tin oxide layer is formed on the surface of a metal material can be used for the purpose of improving the conductivity as an electrode layer or adding a function of reflecting visible light.

[0030] In the present disclosure, the anode layer 21 being an independent layer is even more effective in terms of suppressing crosstalk between adjacent light-emitting layers and color shift in emitted light.

[0031] [Hole Injection Layer] The hole injection layer (HIL) is disposed adjacent to the anode layer 21 in the stacking direction, for example, and may be composed of a hole transport material and an electron accepting material (hole supply material). The material of the hole injection layer may be the same inorganic or organic material as the material described for the hole transport layer below. The specific material of the hole injection layer in the present disclosure may be the same as or different from the material of the hole transport layer described below.

[0032] The hole injection layer may be composed of a material containing an organic hole transport material and an organic electron accepting material (hole supply material) added in the range of 1 to 10%. Known triarylamine organic compounds can be used as the organic hole transport material. Examples of organic electron accepting materials include TCNQ (tetracyanoquinodimethane), TNAP (tetracyano-2,6-naphthoquinodimethane), DCNQI (dicyanoquinomethane), TCNQ-4F (1,2,3,4-fluorinated tetracyanoquinodimethane), TNAP-4F (1,2,3,4,5,6-fluorinated tetracyano-2,6-naphthoquinodimethane), DCTCNQ (dicyanotetracyanoquinodimethane), and the like. Examples of suitable hole-transporting materials include tetracyanoquinodimethane (TCNTQ), tetracyanoterphenylquinomethane (TCNDQ), TNAT (tetracyanoanthracenylquinodimethane), M(dmit)2 (a type of metal complex), OCNAQ (octacyanoanthracenylquinotetramethane), and HAT-CN (dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile). Adding an electron-accepting material to the hole-transporting material described above as the material for the hole-injection layer is even more effective in terms of sufficiently enhancing the hole-injection ability of the hole-injection layer.

[0033] [Hole Transport Layer] The hole transport layer (HTL) may be disposed adjacent to the hole injection layer in the stacking direction, for example, and may be composed of a hole transport material. Examples of the hole transport material include polystyrene sulfonic acid-doped polyethylenedioxythiophene (PEDOT:PSS), 4,4',4"-tris(9-carbazolyl)triphenylamine (TCTA), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (NPB), zinc phthalocyanine (ZnPC), di[4-(N,N-ditolylamino)phenyl]cyclohexane (TAPC), 4,4'-bis(carbazol-9-yl)biphenyl (CBP), and 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN). Examples of hole transport materials include poly(N-vinylcarbazole) (PVK), poly(2,7-(9,9-di-n-octylfluorene))-(1,4-phenylene-(4-sec-butylphenyl)imino)-1,4-phenylene (TFB), and poly(triphenylamine) derivatives (Poly-TPD).

[0034] [Electron Blocking Layer] The electron blocking layer (EBL) may be made of an organic or inorganic hole transport material, similar to the hole transport layer (HTL). The material of the electron blocking layer may be the same as the material of the hole transport layer (HTL), or may be different from the material of the hole transport layer (HTL).

[0035] Furthermore, from the viewpoint of ease of injection of holes from the hole transport layer to the electron blocking layer and ease of injection of holes from the electron blocking layer to the light-emitting layer, the HOMO (Highest Occupied Molecular Orbital) level of the material constituting the electron blocking layer is preferably equal to or higher than the HOMO level of the hole-transport material constituting the hole transport layer, and is preferably equal to or lower than the HOMO level of a host compound described below constituting the light-emitting layer.

[0036] Furthermore, the difference between the HOMO level and the LUMO (Lowest Unoccupied Molecular Orbital) level of the material constituting the electron blocking layer is preferably greater than 3.00 eV, and more preferably greater than 3.05 eV, from the viewpoint of suppressing injection of electrons from the light-emitting layer into the electron blocking layer.

[0037] Furthermore, increasing the difference between the HOMO level and the LUMO level of the material constituting the electron blocking layer may reduce the thermal stability of the material, for example, lowering the glass transition point of the material, which may result in a shift in the carrier mobility characteristics of the electron blocking layer due to instability of the morphology (molecular form or microstructure in the film). Therefore, from the viewpoint of maintaining the thermal stability of the material, the difference between the HOMO level and the LUMO level of the material constituting the electron blocking layer is preferably smaller than 3.50 eV, and more preferably smaller than 3.45 eV.

[0038] [Light-emitting layer] The light-emitting layer (EML) is a layer that emits light of a predetermined color when an electric field is applied. The light-emitting layer is made of a light-emitting material. The light-emitting layer may have a laminated structure in which two or more light-emitting functional layers corresponding to two or more functions for light emission are stacked, such as an immediate light-emitting layer and a delayed light-emitting layer, and the stacked light-emitting functional layers as a whole exhibit a specific light-emitting function.

[0039] For example, examples of light-emitting materials for the blue light-emitting layer include fluorescent dopants such as pyrene-based compounds and anthracene-based compounds, while examples of light-emitting materials for the red and green light-emitting layers include phosphorescent dopants such as iridium complexes, palladium complexes, and platinum complexes.

[0040] In addition, complexes containing iridium, palladium, or platinum-based elements used as phosphorescent dopants are very expensive even in small amounts, due to the limited production of the metal elements and uneven distribution of their production areas, and stable supply may be difficult. Therefore, reducing the amount of phosphorescent dopants using these metal-based complexes is extremely important from the perspectives of cost reduction and economic security.

[0041] In this way, a host-guest emitting layer can be formed by doping a host compound with a guest compound, or by a co-evaporation method using multiple evaporation sources.

[0042] Various known examples of host-guest emitting layer materials can be used. Examples of host compounds include known emitting layer materials for each color as host-guest emitting layer materials.

[0043] Examples of guest compounds include the aforementioned fluorescent dopants and phosphorescent dopants, as well as TADF and hyperfluorescent materials. Further examples of fluorescent dopants include the aforementioned pyrene-based and anthracene-based compounds, as well as perylene, DPT, Coumarin 6, PMDFB, quinacridone, rubrene, BTX, ABTX, DCM, and DCJT. Further examples of phosphorescent dopants include Ir(ppy) for iridium complexes. ３ , Ir(thpy) ３ , Ir(t5m-thpy) ３ , Ir(t-5CF ３ -py) ３ , Ir(t-5t-py) ３ , Ir(mt-5mt-py) ３ , Ir(btpy) ３ , Ir(tflpy) ３ , Ir(piq) ３ , Ir(tiq) ３ , Ir(fliq) ３ , FIrpic, FIr6, Ir(ppy), Ir(tpy), Ir(bzz), Ir(thp), Ir(op), Ir(bo), Ir(bt), Ir( bon), Ir(αbsn), Ir(btp), Ir(ppo), Ir(C6), Ir(pq), Ir(β-bsn), and Ir(ppz).

[0044] Additionally, examples of platinum-based complexes include PtON-TBBI, mPtON7-t-Bu, and PtOEP.

[0045] In addition, the LUMO level of the host compound constituting the light-emitting layer is preferably lower than the LUMO level of the hole-transport material constituting the hole-transport layer, from the viewpoint of suppressing the movement of electrons toward the hole-transport layer side.

[0046] Furthermore, it is preferable that the difference in HOMO levels between the electron blocking layer material and the host compound of the light-emitting layer is larger as the emission wavelength of the light-emitting layer is shorter, from the viewpoint of realizing a difference in the turn-on voltage in the J-V characteristics between the light-emitting layers of multiple colors, which will be described later, by increasing the turn-on voltage of any one of the light-emitting layers of multiple colors when designing a light-emitting device. For example, in the case where a light-emitting device has three light-emitting layers of blue, green, and red, the difference in HOMO levels between the host compound of the blue light-emitting layer and the electron blocking layer material is set to ΔHOMO 青 The HOMO level difference between the host compound of the green light-emitting layer and the electron blocking layer material is defined as ΔHOMO 緑 and the HOMO level difference between the host compound of the red light-emitting layer and the electron blocking layer material is ΔHOMO 赤 , the HOMO level difference in the light-emitting device is ΔHOMO 青 >ΔHOMO 緑 >ΔHOMO 赤 , is preferable.

[0047] The light-emitting layer may also include a quantum dot-containing light-emitting layer that emits light upon excitation by an electric field or current. The quantum dot-containing light-emitting layer is a light-emitting diode (QLED) element that uses quantum dots as its light-emitting layer.

[0048] Quantum dots are semiconductor particles with a particle size of approximately 100 nm or less (e.g., several nm to several tens of nm), and because their composition is derived from semiconductor materials, they are sometimes called semiconductor nanoparticles. Quantum dots can vary their emission wavelength by adjusting the particle size or composition of the particles. The shape of the quantum dots is not limited. For example, the shape of the quantum dots may be a spherical three-dimensional shape (with a circular cross-section), or may be a polygonal three-dimensional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, or a three-dimensional shape with an uneven surface, or a combination thereof.

[0049] The quantum dots may be formed of only a core, or may have a core-shell structure including a core and a shell. The shell may be formed in a solid solution state on the surface of the core. The quantum dots may also include doped nanoparticles.

[0050] Examples of quantum dot core materials include Si, Ge, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, and ZnSeTe. Examples of quantum dot shell materials include CdS, ZnS, CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AIP.

[0051] Examples of combinations of quantum dot core and shell materials include CdSe / CdS, InP / ZnS, ZnSe / ZnS, and CIGS / ZnS.

[0052] The quantum dots described above are quantum dots that emit visible light, and by appropriately adjusting the particle size and composition of the quantum dots, it is possible to control the emission wavelength to any wavelength range, for example, from the blue wavelength range to the red wavelength range.

[0053] A ligand may be coordinated to the surface of the quantum dot as long as the effects of the present disclosure are obtained. Various known ligands can be used as the ligand. The ligand may be an organic ligand or an inorganic ligand.

[0054] Furthermore, the quantum dot-containing light-emitting layer may further contain components other than the above-mentioned ligands, as long as the effects of the present disclosure are achieved. For example, the quantum dot-containing light-emitting layer may further contain a binder component that can be interposed between individual quantum dots. When the light-emitting layer contains a binder component, the reliability of the quantum dot-containing light-emitting device is further improved. Furthermore, since the surface flatness of the quantum dot-containing light-emitting layer is improved, subsequent film formation processes such as the electron transport layer can be easily performed with high yield. Furthermore, maintaining the distance between individual quantum dots can prevent concentration quenching.

[0055] The light-emitting layer containing quantum dots can arbitrarily set the emitted color by adjusting the size of the quantum dots. Furthermore, the light-emitting layer containing quantum dots can be easily and precisely fabricated by a coating method, as described below, and the thickness of the fabricated light-emitting layer can be sufficiently controlled. Furthermore, layers other than the light-emitting layer containing quantum dots are not thermally damaged by the manufacturing conditions of the light-emitting layer. Therefore, a light-emitting device including a light-emitting layer containing quantum dots is suitable from the viewpoint of increasing the reliability of the light-emitting device.

[0056] [Hole Blocking Layer] The hole blocking layer (HBL) is a layer that suppresses hole injection from the light-emitting layer and transports electrons to the light-emitting layer. Specifically, the hole blocking layer contains an electron transporting material. The hole blocking layer may be composed of an inorganic electron transporting material or an organic electron transporting material. Examples of organic electron transporting materials include oxadiazole-based compounds or phenanthroline-based compounds containing one or more metal elements selected from the group consisting of Zn, Ti, Mg, Zr, Sn, and Nb. The material of the hole blocking layer may contain lithium quinoline (Liq) in addition to the electron transporting material. Alternatively, the hole blocking layer may be composed solely of an electron transporting material that does not contain Liq or a metal element and is composed solely of an organic component.

[0057] [Electron Transport Layer] The electron transport layer (ETL) contributes to the transport of electrons and contains an electron transport material. The electron transport material may be an inorganic electron transport material or an organic electron transport material. The electron transport material may be appropriately selected from materials commonly used in the field.

[0058] Examples of inorganic electron transport materials include metal oxide materials containing one or more metal elements selected from the group consisting of Zn, Ti, Mg, Zr, Sn, and Nb, and the metal oxide materials may be in the form of nanoparticles.

[0059] Examples of organic electron transporting materials include compounds and complexes containing one or more nitrogen-containing heterocycles. Examples of nitrogen-containing heterocycles include oxadiazole rings, triazole rings, triazine rings, quinoline rings, phenanthroline rings, pyrimidine rings, pyridine rings, imidazole rings, and carbazole rings. Specific examples of organic electron transporting materials include 1,10-phenanthroline derivatives such as bathocuproine or bathophenanthroline, benzimidazole derivatives such as 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI), metal complexes such as bis(10-benzoquinolinolato)beryllium complex, 8-hydroxyquinoline Al complex, and bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum, and 4,4'-biscarbazole biphenyl.

[0060] As with the hole blocking layer, the material for the electron transport layer may contain lithium quinoline (Liq) in addition to the electron transport material.

[0061] [Electron Injection Layer] The electron injection layer (EIL) is disposed adjacent to the cathode layer, for example, and may be composed of an electron transport material. Examples of electron transport materials constituting the electron injection layer include lithium fluoride (LiF), which is an inorganic material. The electron injection layer may be composed solely of an organic material such as an oxadiazole compound, or may be composed of an organic material doped with a metal material (e.g., Li or Yb), or may be composed solely of a metal material (e.g., Li or Yb).

[0062] LiF used in the electron injection layer exhibits excellent electron injection properties. On the other hand, the formation of a functional layer containing an inorganic material, such as Yb, including but not limited to LiF, is generally carried out at a higher temperature than the formation of an emitting layer and other functional layers made of organic materials due to the high melting point of the inorganic material. This may cause thermal damage to the organic material and (near) infrared emitting material that have been previously formed. Therefore, if possible, it is preferable to form a light-emitting device using only organic materials, without including inorganic materials. Even when the electron injection layer is made only of organic materials, the high electron injection properties of the electron injection layer can be maintained by including metals such as Yb, Li, and Al in the cathode layer.

[0063] Examples of organic materials for the electron injection layer, which can have sufficient properties when combined with a cathode layer made of aluminum (Al) or the like, which can form a vapor deposition layer at a relatively low temperature, include BUPH1, BPen, p-MeO-Phen, and p-NMe. ２ -Phen, and p-Pyrrd-Phen.

[0064] However, the electron injection ability of an electron injection layer using an organic material may be inferior to that of an electron injection layer using an inorganic material such as LiF. Therefore, when an electron injection layer made of an organic material is disposed adjacent to a cathode layer, the amount of carriers (electrons) supplied to the light-emitting layer may decrease. In such a case, it is sufficient to appropriately adjust the amount of holes injected from the anode layer to balance the amount of electrons supplied to the light-emitting layer.

[0065] [Cathode Layer] The cathode layer is the other of a pair of electrode layers, an anode and a cathode, and in the present disclosure is an electrode layer for supplying electrons to each layer constituting the light-emitting element. The cathode layer is disposed opposite the anode layer in the stacking direction. The cathode layer has, for example, electrical conductivity and visible light transparency.

[0066] For example, a material with a relatively small work function is preferably used as the material for the cathode layer, from the viewpoint of enhancing electron injection properties. Examples of electrode materials constituting the cathode layer include metal materials such as alkali metals, alkaline earth metals, and Al, alloys containing these, and nanowires (e.g., Ag nanowires). Examples of alloys include an alloy of Mg and Ag, and Al doped with a small amount of Li.

[0067] A high silver ratio in the Mg-Ag alloy is preferable from the viewpoints of lowering the resistance of the cathode layer, facilitating the flow of carriers (electrons), and facilitating backplane design. A high magnesium ratio is preferable from the viewpoint of reducing the work function of the cathode layer. The silver-to-magnesium ratio can be appropriately determined by further considering the above-mentioned characteristics, as well as the environmental stability required of the cathode layer, such as resistance to oxidation or humidity, the appearance (color) of the cathode layer, the type of light-emitting layer for each color, and the layer configuration for each color. From the viewpoint of achieving at least one of the above effects, the ratio of Mg to the Mg-Ag alloy as the cathode layer material may be 50% or less, 10% or less, or 5% or less by mass. Furthermore, from the above viewpoint, this ratio may be 1% or more.

[0068] In the light-emitting device of the present disclosure, the functional layer between the cathode layer and the light-emitting layer is one or more layers selected from the group consisting of a hole-blocking layer, an electron-transporting layer, and an electron-injection layer, and the functional layer may include a common layer. Having the functional layer closer to the cathode layer than the light-emitting layer be a common layer is more effective from the viewpoints of reducing the manufacturing cost of the light-emitting device and suppressing leakage of holes to adjacent pixels.

[0069] In the light-emitting device according to the present disclosure, the cathode layer may be a common layer, which is more effective from the viewpoint of reducing the manufacturing cost of the light-emitting device and suppressing leakage of holes to adjacent pixels.

[0070] [Method for Manufacturing Light-Emitting Device] The light-emitting device of the present disclosure can be manufactured, for example, according to the flow shown in FIG.

[0071] In step S11, an anode layer is formed on the substrate for each color. That is, the anode layers are formed on the substrate so that they are independently arranged in the surface direction corresponding to the light-emitting layers. For example, Ag is deposited on the substrate by sputtering, and then ITO is deposited on the substrate through a fine metal mask, to form reflective anode layers at positions corresponding to the light-emitting layers in the surface direction.

[0072] Next, in step S12, a hole injection layer (HIL) is formed on the anode layer as a common layer, for example, by co-evaporating a hole transport material and an electron acceptor material through a common mask at a predetermined temperature and rate to form the hole injection layer at each position corresponding to each group of light-emitting layers.

[0073] Next, in step S13, a hole transport layer (HTL) is formed on the hole injection layer as a common layer by, for example, depositing a hole transport material by evaporation at a predetermined temperature and rate through a common mask to form the hole transport layer at each position corresponding to each group of light-emitting layers.

[0074] Next, in step S14, an electron blocking layer (EBL) is formed on the hole transport layer for each color by, for example, depositing a hole transport material by vapor deposition at a predetermined temperature and rate through a fine metal mask, to form a hole transport layer at each position corresponding to the position of the light emitting layer in the in-plane direction.

[0075] Next, in step S15, the light-emitting layers (EMLs) for each color are formed on the electron blocking layer by, for example, co-evaporation of a light-emitting host compound and a dopant through a fine metal mask at a predetermined temperature and rate to sequentially form red, green, and blue light-emitting layers at the respective positions of the light-emitting layers in the in-plane direction.

[0076] Next, in step S16, a hole blocking layer (HBL) is formed as a common layer on the light-emitting layers by, for example, depositing an electron transport material by evaporation at a predetermined temperature and rate through a common mask, at positions corresponding to each group of light-emitting layers.

[0077] Next, in step S17, an electron transport layer (ETL) is formed on the hole blocking layer as a common layer. For example, an electron transport material is deposited by vapor deposition at a predetermined temperature and rate through a common mask to form the electron transport layer at each position corresponding to each group of light-emitting layers. The electron transport layer may also be formed by co-evaporation of the electron transport material and lithium quinoline.

[0078] Next, in step S18, an electron injection layer (EIL) is formed as a common layer on the electron transport layer by, for example, depositing LiF or Yb by evaporation at a predetermined temperature and rate through a common mask, to form the electron injection layer at each position corresponding to each group of light-emitting layers.

[0079] Next, in step S19, a cathode layer is formed as a common layer on the electron injection layer by, for example, depositing Mg and Ag at a predetermined temperature and rate through a common mask by sputtering to form an Mg / Ag metal electrode layer at each position corresponding to each group of light-emitting layers.

[0080] Next, in step S20, a cap layer is formed on the cathode layer as a common layer. For example, lithium fluoride or other organic material is deposited by vapor deposition at a predetermined temperature and rate to form the cap layer on the entire surface. The cap layer may be composed of two or more layers.

[0081] In the case where the light-emitting layer includes a light-emitting layer containing quantum dots, the light-emitting layer containing quantum dots can be produced by a method (coating method) in which an ink in which quantum dots are dispersed in a dispersion medium is applied, the coating film is dried, and the coating film is cured as needed. A slit coater or an inkjet printer can be used to apply the ink, and therefore, the coating method makes it possible to produce a fine light-emitting layer under normal conditions, such as room temperature, normal pressure, and atmospheric air.

[0082] For example, in the above embodiment, if the blue light-emitting layer is a quantum dot light-emitting layer, in the above-mentioned step S15, a quantum dot ink for blue light can be applied to the electron blocking layer using a slit coater or an inkjet device, and then solidified or dried to produce the blue light-emitting layer. Including a quantum dot light-emitting layer in a light-emitting element can reduce the costs of manufacturing equipment and masks compared to a vapor deposition method using a fine metal mask, and is advantageous from the standpoint of reducing initial costs and operating costs in manufacturing.

[0083] [J-V Characteristics (Grayscale Voltage)] In the present disclosure, the difference in grayscale voltage of current density in the J-V characteristics of two light-emitting layers that are adjacent to each other in one plane direction and emit light of different colors is specified to be within a specific range.

[0084] The intermediate gradation voltage is the voltage at the same current density at an intermediate gradation in the J-V characteristics of the light-emitting layer. Here, "intermediate gradation" refers to a range of brightness that is 40 to 60% of the maximum brightness of each light-emitting layer. Therefore, the intermediate gradation voltage is the voltage applied to each light-emitting layer when it is at an intermediate gradation in each light-emitting layer. In the case of an OLED, for example, it is 3.0 to 4.5 mA / cm. ２ It could be.

[0085] If the difference in the intermediate gradation voltages is too small, when a voltage is applied to one of the adjacent light-emitting layers with a lower intermediate gradation voltage, holes may leak to the other light-emitting layer with a higher intermediate gradation voltage, shortening the life of the other light-emitting layer (the period during which the desired luminance characteristics can be maintained).Furthermore, the driving voltage of the other light-emitting layer with a lower intermediate gradation voltage may become approximately the same as that of the other light-emitting layer with a higher intermediate gradation voltage, resulting in increased power consumption of the light-emitting device.

[0086] If the difference in the gray scale voltages is too large, the drive voltage of the adjacent light-emitting layer with the higher gray scale voltage becomes even higher, which may increase the power consumption of the light-emitting device. Also, when a voltage is applied to the light-emitting layer with the higher gray scale voltage, holes are more likely to leak to the light-emitting layer with the lower gray scale voltage, which may make the crosstalk phenomenon in which the lower light-emitting layer also emits light more likely or more pronounced.

[0087] From the viewpoint of suppressing a shortened lifespan of the light-emitting layer having a higher gray scale voltage and an increase in power consumption of the light-emitting device, in the present disclosure, as shown in Fig. 5, the difference in the gray scale voltages between adjacent light-emitting layers in one plane direction is preferably 0.1 V or more, more preferably 0.15 V or more, and even more preferably 0.2 V or more. Furthermore, from the viewpoint of suppressing an increase in power consumption of the light-emitting device and the occurrence of crosstalk, the difference in the gray scale voltages is preferably 1.1 V or less, more preferably 0.9 V or less, and even more preferably 0.7 V or less.

[0088] Furthermore, if the difference between the maximum and minimum values ​​of the intermediate gray scale voltages of the light-emitting layers in each group of light-emitting layers is too large, the driving voltage of the adjacent light-emitting layer with the higher intermediate gray scale voltage will become even higher, which may increase the power consumption of the light-emitting device and shorten the life of the light-emitting layer with the higher intermediate gray scale voltage. Furthermore, even in the light-emitting layer with the lower intermediate gray scale voltage, crosstalk such as weak emission may occur as the power consumption of the light-emitting device increases, which may shorten the life of the light-emitting layer with the lower intermediate gray scale voltage. From the viewpoint of suppressing an increase in the power consumption of the light-emitting device and a shortened life of the light-emitting layers, the difference between the maximum and minimum values ​​of the intermediate gray scale voltages in the group of light-emitting layers is preferably 1.3 V or less, more preferably 1.2 V or less, and even more preferably 1.1 V or less.

[0089] In order to achieve the above-described preferable grayscale voltage difference between adjacent light-emitting layers, the difference between the maximum and minimum grayscale voltages in the group of light-emitting layers is preferably 0.1 × n (V) or more, where n is the number of light-emitting layers included in the group of light-emitting layers.

[0090] The difference in grayscale voltages can be adjusted by the materials of the light-emitting layers or functional layers. For example, the greater the energy level between the materials of adjacent light-emitting layers or functional layers that are independent layers, the greater the difference in grayscale voltages can be. More specifically, when the electron blocking layer is an independent layer, the HOMO level of the electron blocking layer can be changed for each emission color of the corresponding light-emitting layer. Therefore, it is preferable that the electron blocking layer is an independent layer, because the greater the HOMO levels of the electron blocking layer and the light-emitting layer for each adjacent light-emitting element, the greater the difference in turn-on voltage can be.

[0091] The upper limit of the driving voltage of the J-V characteristics when determining the intermediate gradation voltage may be the driving voltage at which the luminance of each light-emitting layer becomes maximum, and the upper limit may be substantially the same for the light-emitting layers of each color, or may be different.

[0092] The light-emitting device of the present disclosure may be configured such that, in each group of light-emitting layers, the grayscale voltages of the light-emitting layers increase sequentially in one direction in the in-plane direction. When the group of light-emitting layers is composed of light-emitting layers of three or more colors, if the light-emitting layers other than those at both ends in the one direction are taken as reference light-emitting layers, the group of light-emitting layers may include both light-emitting layers with grayscale voltages higher than the reference light-emitting layer and light-emitting layers with grayscale voltages lower than the reference light-emitting layer. Therefore, this is suitable for a light-emitting device from the viewpoint of simultaneously reducing the power consumption of the light-emitting device, suppressing shortening of the lifespan of light-emitting layers with higher grayscale voltages, and suppressing crosstalk between light-emitting layers with lower grayscale voltages.

[0093] For example, when the group of light-emitting layers is a group consisting of three light-emitting layers that emit light of red, green, and blue, the grayscale voltages of the light-emitting layers in each group of light-emitting layers may be higher in the order of red, green, and blue. In this case, using the driving voltage of the green light-emitting layer as a reference is advantageous from the viewpoints of reducing the power consumption of the light-emitting device, as well as shortening the life of the blue light-emitting layer and preventing crosstalk in the red light-emitting layer.

[0094] [Explanation of the mechanism of light emission based on gray scale voltage] Figure 6 shows an equivalent circuit diagram when current is applied to the green light-emitting layer in a light-emitting device having three light-emitting layers of blue, green, and red light-emitting layers and a common layer on their anode sides. The meanings of the letters in Figure 6 are as follows: B: Resistance in the stacking direction of the blue light-emitting layer and its common layer on the cathode side G: Resistance in the stacking direction of the green light-emitting layer and its common layer on the cathode side R: Resistance in the stacking direction of the red light-emitting layer and its common layer on the cathode side R Ｖ R: Resistance in the stacking direction (longitudinal resistance) of the hole injection layer and the hole transport layer Ｌ A: Resistance in the plane direction (lateral resistance) of the hole injection layer and the hole transport layer Ｇ A: Anode layer of green light-emitting layer (independent layer) Ｂ : Anode layer (independent layer) of blue light-emitting layer C: Cathode layer (common layer) V １ : voltage applied to the anode layer of the green light-emitting layer when emitting green light V ２ : voltage applied to the anode layer of the blue light-emitting layer when emitting blue light V Ｂ : voltage applied to the blue light-emitting layer when emitting green light V Ｒ : Voltage applied to the red light-emitting layer when emitting green light I Ｌ n: Current in the plane direction (lateral current) in the hole injection layer and the hole transport layer Ｌ : Number of holes moving in the surface direction (horizontal direction) q: Charge

[0095] The relationship between the voltage in the stacking direction and the current in the surface direction is expressed by the following formula (1), and the following formula (2) is derived from formula (1): １ -V Ｂ =I Ｌ ×R Ｌ (1) V １ -V Ｂ = q × n Ｌ ×R Ｌ (2)

[0096] The functional layers of organic EL devices are essentially composed of insulating materials. Each layer is approximately 10 to 100 nm thick, while its length in the plane direction is several 10 μm. Therefore, carriers are unlikely to flow in the plane direction of each layer, resulting in little leakage to adjacent subpixels. However, when a voltage is applied to a specific subpixel, carriers may leak to the adjacent subpixel. For example, even when only the green light-emitting layer is lit, current may flow to the blue and red subpixels adjacent to the green subpixel. In this case, even though the green subpixel is intended to be lit, one or both of the adjacent blue and red subpixels may be slightly lit, resulting in color mixing and reduced color purity. Furthermore, current flowing from the green subpixel to the blue subpixel may cause degradation of the blue light-emitting layer, and current flowing from the green subpixel to the red subpixel may cause degradation of the red subpixel.

[0097] In order to obtain green light emission from the green sub-pixel, the voltage applied between the anode layer, which is an independent layer, and the cathode layer, which is a common layer, in the green sub-pixel is V. １ Voltage V １ 7 varies depending on the current density (J), and can be any value within a sufficiently large range. Note that, unless otherwise specified, a cross in the figure indicates the intersection of two lines.

[0098] <Impact on conventional blue sub-pixels> When a voltage V is applied to the anode layer of the green sub-pixel １ When a voltage is applied to the blue sub-pixel, V Ｂ This is because, as shown in FIG. 8, the J-V characteristics of the conventional blue light-emitting layer (dashed line in FIG. 8) are close to those of the green light-emitting layer, and therefore some of the holes that should flow into the green subpixel also flow into the blue subpixel via the common layer (hole injection layer and hole transport layer). As a result, as shown in FIG. 8, the blue light-emitting layer has a current density of J ｂ mA / cm ２ In this way, when the green sub-pixel is energized, electricity also flows in the blue light-emitting layer, and therefore, degradation of the blue light-emitting layer occurs in the blue sub-pixel when green light is emitted.

[0099] Here, the amount of holes flowing from the green sub-pixel to the blue sub-pixel through the common layer is determined by applying a voltage V between the anode layer, which is an independent layer of the blue sub-pixel, and the cathode layer, which is a common layer, in order to make the blue light-emitting layer in the blue sub-pixel emit light. ２ can be considered to be substantially the same as the amount of holes that flow when V Ｂ ≒V ２ ). V １ and V Ｂ The difference between the lateral resistance R Ｌ and the amount (number) of holes n Ｌ It is expressed as the product of

[0100] <Impact of the Present Disclosure on Blue Subpixels> In this embodiment, the grayscale voltage of the blue light-emitting layer is designed to be higher than the grayscale voltage of the green light-emitting layer by 0.1 to 1.1 V. The grayscale voltage characteristics of a conventional blue light-emitting layer are comparable to the grayscale voltage characteristics of the green light-emitting layer in this embodiment. Therefore, in this embodiment, within the range of drive voltages for the green subpixels, the voltage of the green light-emitting layer rises earlier than the voltage of the blue light-emitting layer, and the current density J of the blue light-emitting layer in this embodiment, as shown by the solid line in FIG. Ｂ is the current density J of the conventional blue light-emitting layer ｂ As a result, in this embodiment, compared to the conventional art, the conduction in the blue light-emitting layer when the green sub-pixel is conducting is suppressed, and deterioration of the blue light-emitting layer is suppressed.

[0101] <Impact on Conventional Red Sub-Pixel> In a conventional light-emitting device, the grayscale voltage of the red light-emitting layer is sufficiently lower than the grayscale voltage of the green light-emitting layer, as shown by the dashed line in FIG. 9. Therefore, when the voltage V １ When V is applied, some of the holes that should flow into the green subpixel also flow into the red subpixel through the common layer (hole injection layer and hole transport layer), and as a result, V R Therefore, when the green sub-pixel is energized, a voltage of J is applied to the red light-emitting layer. ｒ mA / cm ２ The current density J ｒ is V ＲThis is significantly larger than the current density of the green light-emitting layer when voltage is applied. Therefore, when green light is emitted, a sufficiently large current also flows in the red light-emitting layer, causing the red light-emitting layer to emit light, and this unintended current flow can deteriorate the red light-emitting layer.

[0102] <Impact of the Present Disclosure on Red Subpixel> In this embodiment, the grayscale voltage of the red light-emitting layer is closer to the grayscale voltage of the green light-emitting layer than that of the conventional technology, and the difference is designed to be in the range of 0.1 to 1.1 V. Therefore, as shown by the solid line in FIG. 9 , in the range of the driving voltage of the green subpixel, the voltage of the red light-emitting layer rises earlier than the voltage of the green light-emitting layer. Ｒ When the current density J is applied Ｒ is the same as that of the conventional red light-emitting layer (J ｒ ) is significantly reduced compared to the conventional case. Therefore, in this embodiment, the conduction of current in the red light-emitting layer due to the conduction of current in the green sub-pixel is suppressed, and unexpected light emission from the red light-emitting layer is suppressed, thereby suppressing deterioration of the red light-emitting layer.

[0103] As described above, in this embodiment, the gray scale voltages of the J-V characteristics of the three light-emitting layers that respectively emit red, green, and blue light and that constitute the group of color-emitting layers are set to be higher in the order of red, green, and blue, and the voltage differences between the gray scale voltages of adjacent light-emitting layers in the surface direction within the group of light-emitting layers, i.e., between the gray scale voltage of the red light-emitting layer and the gray scale voltage of the green light-emitting layer, and between the gray scale voltage of the green light-emitting layer and the gray scale voltage of the blue light-emitting layer, are each set to 0.1 to 1.1 V. As a result, when a voltage is applied to the green subpixel, holes leak laterally from the green subpixel to the blue and red subpixels via the common layer on the anode layer side, so that even if a voltage is applied to the blue and red subpixels, current is less likely to flow in the blue and red subpixels than in the past.

[0104] That is, the intermediate gray scale voltage of the J-V characteristic of the blue sub-pixel is shifted to a higher voltage side than that of the green sub-pixel. Therefore, when it is desired to light only the green light emitting layer, a voltage V Ｂ Even if a large current is applied, the magnitude of the current flowing through the blue subpixel (current density: J ｂ From JＢ Therefore, the deterioration of the blue sub-pixel is prevented more effectively than in the past.

[0105] In addition, the intermediate gradation voltage of the J-V characteristic of the red subpixel is shifted to the high voltage side so that the voltage difference between the red subpixel and the green subpixel is approximately the same as the voltage difference between the green subpixel and the blue subpixel. Therefore, when it is desired to light only the green light-emitting layer, a voltage V Ｒ Even if a current density is applied, the magnitude of the current flowing through the red sub-pixel is Ｒ Therefore, unexpected light emission and deterioration of the red light-emitting layer are suppressed.

[0106] Furthermore, the difference between the intermediate gradation voltage of the red light-emitting layer and the intermediate gradation voltage of the blue light-emitting layer is 1.3 V or less, as shown in Fig. 5. As a result, when it is desired to light only the green light-emitting layer, the influence (hole leakage) on both the red light-emitting layer and the blue light-emitting layer can be sufficiently suppressed. Therefore, this is preferable from the viewpoint of fully and balancedly achieving the effect of adjusting the intermediate gradation voltage as described above.

[0107] [J-V Characteristics (Rise Voltage) of Light-Emitting Device] In the present disclosure, it is preferable that the difference in rise voltage of current density in the J-V characteristics of two light-emitting layers that are adjacent to each other in one plane direction and emit light of different colors is specified to be within a specific range.

[0108] If the difference in the on-state voltage is too small, when a voltage is applied to one of the adjacent light-emitting layers with a lower on-state voltage, holes may leak to the light-emitting layer with a higher on-state voltage, shortening the life (the period during which the desired luminance characteristics can be maintained) of the light-emitting layer with the higher on-state voltage.Furthermore, the driving voltage of the light-emitting layer with the lower on-state voltage may become approximately the same as that of the light-emitting layer with the higher on-state voltage, which may increase the power consumption of the light-emitting device.

[0109] If the difference in the on-state voltage is too large, the driving voltage of the adjacent light-emitting layer with the higher on-state voltage becomes even higher, which may increase the power consumption of the light-emitting device. Also, when a voltage is applied to the light-emitting layer with the higher on-state voltage, holes are more likely to leak to the light-emitting layer with the lower on-state voltage, which may make the crosstalk phenomenon in which the lower light-emitting layer also emits light more likely or more pronounced.

[0110] From the viewpoint of suppressing a shortened life of the light-emitting layer having a higher turn-on voltage and an increase in power consumption of the light-emitting device, in the present disclosure, the difference in the turn-on voltage between adjacent light-emitting layers in one plane direction is preferably 0.1 V or more, more preferably 0.2 V or more, and even more preferably 0.3 V or more, as shown in Figure 10. Furthermore, from the viewpoint of suppressing an increase in power consumption of the light-emitting device and the occurrence of crosstalk, the difference in the turn-on voltage is preferably 1.0 V or less, more preferably 0.85 V or less, and even more preferably 0.7 V or less.

[0111] The difference in turn-on voltage can be adjusted by the material of the light-emitting layer or functional layer. For example, the difference in turn-on voltage can be increased if the energy level between the materials of adjacent light-emitting layers or functional layers that are independent layers is higher. More specifically, when the electron blocking layer is an independent layer, the HOMO level of the electron blocking layer can be changed for each emission color of the corresponding light-emitting layer. Therefore, it is preferable that the electron blocking layer is an independent layer, from the viewpoint that the difference in turn-on voltage can be increased as the HOMO levels of the electron blocking layer and the light-emitting layer are increased for each adjacent light-emitting element.

[0112] The above-mentioned turn-on voltage can be determined as follows. First, as shown in Fig. 11, a drive voltage is applied to each light-emitting layer until the slope of the J-V characteristics of each light-emitting layer decreases, and the current density at that time is determined and plotted with the vertical axis as a logarithm. Usually, the current density of the light-emitting layer substantially reaches a plateau at about 1 to 3 V, so the maximum drive voltage may be set to 3 V.

[0113] Next, the plotted measurement points are divided into two groups I and II, and an approximate straight line of the measurement points is calculated for each group.

[0114] Next, the ranges of groups I and II are changed and the process of finding an approximate straight line of the measurement points for each group is repeated to find a plurality of approximate straight lines of the measurement points of each group in the plurality of ranges of groups I and II.

[0115] Next, for each group, the approximate line that minimizes the error between the approximate line and the measurement points is determined by referring to the multiple approximate lines that have been determined.

[0116] Next, the voltage value at the intersection of the approximate line in group I that minimizes the error and the approximate line in group II that minimizes the error is found, and this is taken as the rise voltage.

[0117] 12 shows an example of an approximate line with the smallest error in groups I and II as a thick solid line. If there are too few measurement points in group I (if the boundary value of the drive voltage is too low), the error between the measurement points in group I and the approximate line tends to be large, and if there are too few measurement points in group II (if the boundary value of the drive voltage is too high), the error between the measurement points in group II and the approximate line tends to be large.

[0118] The upper limit of the drive voltage of the J-V characteristic when determining the turn-on voltage may be the same or different for each light-emitting layer of each color. The upper limit may be a specific value such as 3 V, as described above, or may be specified by the differential coefficient of the J-V characteristic curve when the current density increment starts to decrease, or the inflection point of the curve. Alternatively, the upper limit may be the drive voltage value when the current density reaches a specific current density value after the current density increment increases by a specific amount on the J-V characteristic curve. Appropriately setting the upper limit of the drive voltage is preferable from the viewpoint of accurately determining the turn-on voltage.

[0119] The light-emitting device of the present disclosure may be configured such that the turn-on voltage of each of the groups of light-emitting layers increases sequentially in one direction in the in-plane direction. When the group of light-emitting layers is composed of light-emitting layers of three or more colors, if the light-emitting layers other than those at both ends in the one direction are considered to be reference light-emitting layers, the group of light-emitting layers may include both light-emitting layers with a higher turn-on voltage than the reference light-emitting layer and light-emitting layers with a lower turn-on voltage than the reference light-emitting layer. Therefore, this is suitable for a light-emitting device from the viewpoint of simultaneously reducing the power consumption of the light-emitting device, suppressing shortening of the lifespan of light-emitting layers with higher turn-on voltages, and suppressing crosstalk between light-emitting layers with lower turn-on voltages.

[0120] For example, when the group of light-emitting layers is a group consisting of three light-emitting layers that emit light of red, green, and blue, the turn-on voltages of the light-emitting layers in each group of light-emitting layers are usually higher in the order of red, green, and blue. In this case, using the driving voltage of the green light-emitting layer as the reference is advantageous from the viewpoints of reducing the power consumption of the light-emitting device, shortening the life of the blue light-emitting layer, and suppressing crosstalk in the red light-emitting layer.

[0121] [Explanation of the mechanism of light emission based on the rising voltage] In order to obtain green light emission from the green sub-pixel, the voltage applied between the anode layer, which is an independent layer, and the cathode layer, which is a common layer, in the green sub-pixel is V １ Voltage V １ varies depending on the current density (J), for example, as shown in FIG. 13, and may be any value within a range where the variation is sufficient.

[0122] <Impact on conventional blue sub-pixels> When a voltage V is applied to the anode layer of the green sub-pixel １ When a voltage is applied to the blue sub-pixel, V Ｂ This is because, as shown in FIG. 14, the J-V characteristics of the conventional blue light-emitting layer (dashed line in FIG. 14) are close to those of the green light-emitting layer, and therefore some of the holes that should flow into the green subpixel also flow into the blue subpixel via the common layer (hole injection layer and hole transport layer). As a result, as shown in FIG. 14, the blue light-emitting layer has a current density of J ｂ mA / cm ２In this way, when the green sub-pixel is energized, electricity also flows in the blue light-emitting layer, and therefore, degradation of the blue light-emitting layer occurs in the blue sub-pixel when green light is emitted.

[0123] Here, the amount of holes flowing from the green sub-pixel to the blue sub-pixel through the common layer is determined by applying a voltage V between the anode layer, which is an independent layer of the blue sub-pixel, and the cathode layer, which is a common layer, in order to make the blue light-emitting layer in the blue sub-pixel emit light. ２ can be considered to be substantially the same as the amount of holes that flow when V Ｂ ≒V ２ ). V １ and V Ｂ The difference between the lateral resistance R Ｌ and the amount (number) of holes n Ｌ It is expressed as the product of

[0124] <Impact of the Present Disclosure on Blue Subpixel> In this embodiment, the rise voltage of the blue light-emitting layer is designed to be higher than the rise voltage of the green light-emitting layer in the range of 0.1 V to 1.0 V. The rise voltage characteristics of a conventional blue light-emitting layer are similar to the rise voltage characteristics of the green light-emitting layer in this embodiment. Therefore, in this embodiment, within the range of the driving voltage of the green subpixel, the voltage of the green light-emitting layer rises earlier than the voltage of the blue light-emitting layer, and the current density J of the blue light-emitting layer in this embodiment, as shown by the solid line in FIG. 14 , Ｂ is the current density J of the conventional blue light-emitting layer ｂ As a result, in this embodiment, compared to the conventional art, the conduction in the blue light-emitting layer when the green sub-pixel is conducting is suppressed, and deterioration of the blue light-emitting layer is suppressed.

[0125] <Effect on Conventional Red Sub-Pixel> In a conventional light-emitting device, the turn-on voltage of the red light-emitting layer is sufficiently lower than the turn-on voltage of the green light-emitting layer, as shown by the dashed line in FIG. 15. Therefore, when a voltage V １ When V is applied, some of the holes that should flow into the green subpixel also flow into the red subpixel through the common layer (hole injection layer and hole transport layer), and as a result, V R A voltage of V is applied. Ｒcorresponds to the voltage at which the change in current density in the J-V characteristic curve of the red light-emitting layer reaches a plateau. ｒ mA / cm ２ The current density J ｒ is V Ｒ This is significantly larger than the current density in the green light-emitting layer when a current is applied. Therefore, when a current is applied to the green sub-pixel, a sufficiently large current also flows in the red light-emitting layer, causing the red light-emitting layer to emit light when green light is emitted, and this unintended current flow can cause degradation of the red light-emitting layer.

[0126] <Impact of the Present Disclosure on Red Subpixel> In this embodiment, the turn-on voltage of the red light-emitting layer is closer to the turn-on voltage of the green light-emitting layer than in the conventional case, and the difference is designed to be in the range of 0.1 V to 1.0 V. Therefore, as shown by the solid line in FIG. 15 , within the range of the driving voltage of the green subpixel, the voltage of the red light-emitting layer rises earlier than the voltage of the green light-emitting layer. Ｒ When the current density J is applied Ｒ is the same as that of the conventional red light-emitting layer (J ｒ ) is significantly reduced compared to the conventional case. Therefore, in this embodiment, the conduction of current in the red light-emitting layer due to the conduction of current in the green sub-pixel is suppressed, and unexpected light emission from the red light-emitting layer is suppressed, thereby suppressing deterioration of the red light-emitting layer.

[0127] As described above, in this embodiment, the turn-on voltages of the J-V characteristics of the three light-emitting layers that constitute the group of color-emitting layers and emit light of red, green, and blue become higher in the order of red, green, and blue, and the voltage differences between the turn-on voltages of adjacent light-emitting layers in the plane direction within the group of light-emitting layers, i.e., between the turn-on voltages of the red light-emitting layer and the green light-emitting layer, and between the turn-on voltages of the green light-emitting layer and the blue light-emitting layer, are each set to 0.1 V or more and 1.0 V or less. As a result, when a voltage is applied to the green subpixel, holes leak laterally from the green subpixel to the blue and red subpixels via the common layer on the anode layer side, so that even when a voltage is applied to the blue and red subpixels, current is less likely to flow in the blue and red subpixels than in the past.

[0128] That is, the onset voltage of the J-V characteristic of the blue sub-pixel is shifted to a higher voltage side than the onset voltage of the green sub-pixel. Therefore, when it is desired to light only the green light-emitting layer, a voltage V Ｂ Even if a large current is applied, the magnitude of the current flowing through the blue subpixel (current density: J ｂ From J Ｂ Therefore, the deterioration of the blue sub-pixel is prevented more effectively than in the past.

[0129] In addition, the rise voltage of the J-V characteristic of the red subpixel is shifted to the high voltage side so that the voltage difference between the red subpixel and the green subpixel is approximately the same as the voltage difference between the green subpixel and the blue subpixel. Therefore, when it is desired to light only the green light-emitting layer, a voltage V Ｒ Even if a current density is applied, the magnitude of the current flowing through the red sub-pixel is Ｒ Therefore, unexpected light emission and deterioration of the red light-emitting layer are suppressed.

[0130] [Other Aspects] In the above-described embodiment, the first electrode layer is an anode layer and the second electrode layer is a cathode layer, but in the present disclosure, the first electrode layer may be a cathode layer and the second electrode layer may be an anode layer, as long as the above-described conditions for the presence of a common layer and the turn-on voltage are satisfied. Furthermore, the light-emitting device according to the present disclosure may be fabricated from either the first electrode layer or the second electrode layer, as long as the above-described conditions for the presence of a common layer and the turn-on voltage are satisfied.

[0131] A device including a light-emitting device according to the present disclosure may be a device other than the display device described in the above embodiment. For example, the device may be a full-color display device including light-emitting elements of four or more colors, or a surface-emitting device (illumination device) including light-emitting elements of two or more colors and capable of changing the color tone based on white.

[0132] The light-emitting device according to the present disclosure may be a device in which a light-emitting layer that emits light of a first color and a light-emitting layer that emits light of a second color are arranged adjacent to each other, or a device in which four types of light-emitting layers that emit light of the first to fourth colors are arranged adjacent to each other in sequence.

[0133] In the light-emitting device according to the present disclosure, it is sufficient that one or more of the functional layers are common layers, and the number of functional layers may be determined within a range that can reduce manufacturing costs. For example, all of the functional layers may be common layers. Such a configuration is even more effective in terms of reducing the cost of manufacturing the functional layers.

[0134] In the light-emitting device according to the present disclosure, the turn-on voltages of the three light-emitting layers of red, green, and blue do not have to increase in the above order. For example, in a group of light-emitting layers, the turn-on voltages may increase in the order of green, red, and blue, or in the order of green, blue, and red. Furthermore, the light-emitting layer used as the reference for the turn-on voltage in the group of light-emitting layers does not have to be the central light-emitting layer (green light-emitting layer). For example, the turn-on voltages of the light-emitting layers may increase in order from the light-emitting layer at one end to the light-emitting layer at the other end in the order of red, green, and blue in the in-plane direction.

[0135] In the light-emitting device according to the present disclosure, the electron blocking layer may be a common layer. In this case, the thickness of the sub-pixels of each color may be changed by treating the functional layers other than the electron blocking layer as independent layers and changing the thickness of the independent functional layers.

[0136] According to the present disclosure, it is possible to further reduce the power consumption of a light-emitting device having light-emitting layers of multiple colors and prevent a shortening of the lifespan of the light-emitting layers. The technology of the present disclosure, which has such effects, is expected to contribute to the achievement of, for example, Goal 9 of the Sustainable Development Goals (SDGs) proposed by the United Nations, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0137] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0138] An embodiment of the present disclosure is described below.

[0139] [Example of Fabrication of Light-Emitting Device] An acrylic resin layer was fabricated on a substrate, and ITO, Ag, and SiN were deposited thereon in this order by sputtering through a fine metal mask, to form first electrode layers each consisting of a SiN / Ag / ITO film as an anode layer at a position corresponding to the light-emitting layer in the surface direction.

[0140] Next, the hole transport material and 3% by mass of TCNQ-4F were co-deposited through a common mask to form hole injection layers with a thickness of 10 nm at positions corresponding to each group of light-emitting layers.

[0141] Next, a triphenylamine-based compound, which is a hole transport material, was deposited by vapor deposition through a fine metal mask to form hole transport layers having thicknesses corresponding to the emitted light colors at positions corresponding to the light-emitting layers: the hole transport layer thickness for the green light-emitting layer was 110 nm, the hole transport layer thickness for the blue light-emitting layer was 100 nm, and the hole transport layer thickness for the red light-emitting layer was 120 nm.

[0142] Next, hole transport material 1, which is a carbazole-based compound, and hole transport material 2, which is a triphenylamine-based compound different from that of the hole transport layer, were deposited in this order by vapor deposition through a fine metal mask to prepare two-layer electron blocking layers having thicknesses corresponding to the emitted light colors at positions corresponding to the light-emitting layers. The thickness of the electron blocking layer for the green light-emitting layer was 30 nm, the thickness of the electron blocking layer for the blue light-emitting layer was 5 nm, and the thickness of the electron blocking layer for the red light-emitting layer was 80 nm.

[0143] Next, fluorescent or phosphorescent light-emitting layers were prepared for each color. A 35-nm-thick green phosphorescent light-emitting layer was prepared by co-depositing a light-emitting host compound, which was a mixture of an electron transport material and a hole transport material, and a dopant, which was an indium complex compound for green light emission, through a fine metal mask. A 20-nm-thick blue fluorescent light-emitting layer was prepared by co-depositing a light-emitting host compound, which was a perylene-based compound, and a dopant, which was an anthracene-based compound, through a fine metal mask. A 35-nm-thick red phosphorescent light-emitting layer was prepared by co-depositing a light-emitting host compound, which was a mixture of an electron transport material and a hole transport material, and a dopant, which was an indium complex compound for red light emission, through a fine metal mask.

[0144] Next, a phenanthroline-based compound serving as an electron transport material was deposited by vapor deposition through a fine metal mask to form hole-blocking layers having thicknesses corresponding to the emission colors at positions corresponding to the light-emitting layers. The thickness of the hole-blocking layer for the green light-emitting layer was 5 nm, and the thicknesses of the hole-blocking layers for the blue light-emitting layer and the red light-emitting layer were each 10 nm.

[0145] Next, an oxadiazole-based compound serving as an electron transport material was deposited by vapor deposition through a fine metal mask to form electron transport layers having thicknesses corresponding to the emission colors at positions corresponding to the light-emitting layers. The electron transport layer for the green light-emitting layer had a thickness of 20 nm, and the electron transport layers for the blue light-emitting layer and the red light-emitting layer each had a thickness of 25 nm.

[0146] Next, Yb was deposited by vapor deposition through a fine metal mask to form electron injection layers having thicknesses corresponding to the emission colors at positions corresponding to the light-emitting layers. The thicknesses of the electron injection layers for the green and red light-emitting layers were each 5 nm, and the thickness of the electron injection layer for the blue light-emitting layer was 3 nm.

[0147] Next, Mg and Ag were deposited by sputtering through a fine metal mask at positions corresponding to the light-emitting layers in a quantitative ratio according to the emitted color to prepare a metal electrode layer containing Mg and Ag as a second electrode layer (cathode layer). The mass ratio of Mg to Ag in the second electrode layer relative to the green light-emitting layer (Mg:Ag) was 5:95, the mass ratio of Mg to Ag in the second electrode layer relative to the blue light-emitting layer (Mg:Ag) was 10:90, and the mass ratio of Mg to Ag in the second electrode layer relative to the red light-emitting layer (Mg:Ag) was 50:50.

[0148] In this way, a light-emitting device was fabricated that had three light-emitting layers of red, green, and blue as a group and a common layer on the first electrode layer side of the light-emitting layers. The energy levels of each layer in the fabricated light-emitting device are as follows: [Blue] HOMO level of the host compound of the blue-emitting layer (EML-host(Blue)): −5.80 eV HOMO level of the electron blocking layer (EBL(Blue)): −5.49 eV LUMO level of the electron blocking layer (EBL(Blue)): −2.41 eV [Green] HOMO level of the host compound of the green-emitting layer (EML-host(Green)): −5.56 eV, HOMO level of the electron blocking layer (EBL(Green)): −5.48 eV, LUMO level of the electron blocking layer (EBL(Green)): −2.39 eV [Red] HOMO level of the red-emitting layer (EML-host(Red)): −5.54 eV, HOMO level of the electron blocking layer (EBL(Red)): −5.41 eV LUMO level of electron blocking layer (EBL(Red)): −2.30 eV

[0149] [J-V Characteristics 1 (Rise Voltage)] The J-V characteristics were measured when the above light-emitting device was made to emit light for each color, and the rise voltage for each color was determined. The J-V characteristics including the rise voltages for the three colors of red, green, and blue are shown in FIG. 16, the J-V characteristics for green emission are shown in FIG. 17, the J-V characteristics for blue emission are shown in FIG. 18, and the J-V characteristics for red emission are shown in FIG. 19. The rise voltages for emission of each color are shown in Table 1 below.

[0150]

[0151] As shown in Table 1, in the light emitting device of the example, the difference in the current density turn-on voltage in the JV characteristics between two light emitting layers adjacent to each other in the plane direction and emitting light of different colors was 0.2V.

[0152] [J-V Characteristics 2 (Gradation Voltage)] The J-V characteristics were measured when the above light-emitting device was caused to emit light for each color, and the gradient voltage for each color was determined. As a result, the range of current density corresponding to the gradient voltage for each color light-emitting layer was 3.0 to 4.5 mA / cm ２ It was confirmed that the range of 3.0 to 4.5 mA / cm ２ The J-V characteristics including the intermediate gradation voltages of the three colors of red, green, and blue are shown in FIG. 20, the J-V characteristics of green light emission are shown in FIG. 21, the J-V characteristics of blue light emission are shown in FIG. 22, and the J-V characteristics of red light emission are shown in FIG. 23. Note that when the current density is 3.0 mA / cm ２ The driving voltage of the green light-emitting layer was 3.27 V, and the current density was 4.5 mA / cm ２ The driving voltage of the green light-emitting layer was 3.44 V when the current density was 3.0 mA / cm ２ The driving voltage of the blue light-emitting layer was 3.75 V, and the current density was 4.5 mA / cm ２ The driving voltage of the blue light-emitting layer was 3.95 V. When the current density was 3.0 mA / cm ２ The driving voltage of the red light-emitting layer at this time was 3.15 V, and the current density was 4.5 mA / cm ２ The driving voltage of the red light-emitting layer at this time was 3.34 V. The gray scale voltage difference for each color of light emission is shown in Table 2 below.

[0153]

[0154] As shown in Table 2, in the light-emitting device of the example, the current density was 3.0 to 4.5 mA / cm ２When the light emitting device is caused to emit light for each color within the above range, the red light emitting layer, the green light emitting layer, and the red light emitting layer satisfy the following conditions for the intermediate gray scale voltage of the J-V characteristics at the same current density: Intermediate gray scale voltage value: red light emitting layer < green light emitting layer < blue light emitting layer Difference in intermediate gray scale voltage value between the red light emitting layer and the green light emitting layer: 0.1 to 1.1 V Difference in intermediate gray scale voltage value between the green light emitting layer and the blue light emitting layer: 0.1 to 1.1 V Difference in intermediate gray scale voltage value between the red light emitting layer and the blue light emitting layer: 1.3 V or less

[0155] [Evaluation] (1) Color shift in white light emission White light emission was achieved by emitting three colors, red, green, and blue, in the light-emitting device of the example. The light-emitting device was then driven for 300 hours, and the chromaticity of the white light emission was measured before and after driving. The difference in chromaticity in the chromaticity diagram was 0.02 or less (Δx≦0.02, Δy≦0.02) in both the x-axis and y-axis directions.

[0156] When green and blue light are emitted simultaneously, if holes are supplied from the green light-emitting layer to the blue light-emitting layer, the life of the blue light-emitting layer will be shortened, and the chromaticity of the white light will change accordingly. However, in the light-emitting device of the example, the chromaticity of the white light emission does not change substantially, which indicates that the blue light-emitting layer continues to function normally. Therefore, it is clear that the leakage of holes from the green light-emitting layer to the blue light-emitting layer is sufficiently suppressed in the light-emitting device of the example.

[0157] (2) Influence of Red Light Emission In the light-emitting device of the example, current was applied using only the anode layer corresponding to the green light-emitting layer, causing only the green light-emitting layer to emit light and measuring the emission spectrum. The emission spectrum of the light-emitting device of the example when emitting green light is shown in Figure 24. In Figure 24, the solid line shows the emission spectrum of the light-emitting device of the example when emitting green light, and the dashed line shows the emission spectrum of the light-emitting device of the comparative example when emitting green light. The comparative example light-emitting device is a light-emitting device equipped with conventional blue and red light-emitting layers as shown by the dashed lines in Figures 8 and 9, or Figures 14 and 15.

[0158] As shown in Figure 24, it can be seen that the influence of red and blue emissions is substantially absent in the green emission of the light-emitting device of the example. Thus, in the light-emitting device of the example, the slight red and blue emissions during green emission are substantially prevented, and therefore, it can be seen that the leakage of holes from the green light-emitting layer to the red light-emitting layer is sufficiently suppressed. In contrast, in the light-emitting device of the comparative example, slight red and blue emissions are detected during green emission. This is thought to be due to the leakage of holes from the green light-emitting layer to the red and blue light-emitting layers during green emission.

[0159] REFERENCE SIGNS LIST 10 Light-emitting device 21 Anode layer (first electrode layer) 22 Hole injection layer 23 Hole transport layer 24 Electron blocking layer 25 Light-emitting layer 26 Hole blocking layer 27 Electron transport layer 28 Electron injection layer 29 Cathode layer (second electrode layer) 100 Display device 110 Substrate 120 Cap layer DA Display area NDA Frame area PIX Pixel RSP Red sub-pixel GSP Green sub-pixel BSP Blue sub-pixel

Claims

1. A light-emitting device in which a first electrode layer which is one of an anode layer and a cathode layer, a light-emitting layer, and a second electrode layer which is the other of the anode layer and the cathode layer are stacked in this order in the stacking direction, and a functional layer is provided either or both between the first electrode layer and the light-emitting layer and between the light-emitting layer and the second electrode layer, two or more of the light-emitting layers which emit light of different colors are arranged adjacent to each other in a direction intersecting with the stacking direction, and at least a part of the functional layer is formed as a common, integrated layer for two or more adjacent light-emitting layers, when the voltage at the same current density at a middle gray level in the current density-voltage characteristics of the light-emitting layers is defined as a middle gray level voltage, the difference in the middle gray level voltage between two of the light-emitting layers which are adjacent to each other in one direction intersecting with the stacking direction and emit light of different colors is 0.1 V or more and 1.1 V or less.

2. The light emitting device according to claim 1, wherein two or more groups of light emitting layers each comprising two or more light emitting layers emitting light of two or more different colors are arranged in a direction intersecting the stacking direction.

3. The light emitting device according to claim 2, wherein the group of light emitting layers comprises three or more light emitting layers that emit light of three or more different colors.

4. The light emitting device according to claim 2 or 3, wherein the gray scale voltages of the light emitting layers in each of the groups of light emitting layers increase sequentially in the one direction in each of the groups of light emitting layers.

5. The light emitting device according to any one of claims 2 to 4, wherein the difference between the maximum and minimum values of the gray scale voltages of the light emitting layers in each of the groups of light emitting layers is 1.3 V or less.

6. A light emitting device according to any one of claims 2 to 5, wherein the group of light emitting layers is a group consisting of three light emitting layers that emit light of red, green, and blue, respectively, and the intermediate gradation voltages of the light emitting layers in each of the groups of light emitting layers become higher in the order of red, green, and blue.

7. The light-emitting device according to any one of claims 1 to 6, wherein the functional layer between the anode layer and the light-emitting layer includes an electron blocking layer adjacent to the light-emitting layer in the stacking direction, and the electron blocking layer is independently disposed for each light-emitting layer in the one direction intersecting the stacking direction.

8. The light-emitting device according to claim 7, wherein the electron blocking layer has a thickness that varies depending on the color of the light-emitting layer in the one direction that intersects with the stacking direction.

9. The light-emitting device according to any one of claims 1 to 6, wherein the functional layer is one or more layers selected from the group consisting of a hole injection layer, a hole transport layer, an electron blocking layer, a charge generation layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and includes a layer formed as an integrated layer common to two or more of the light-emitting layers adjacent to each other in the direction intersecting the stacking direction.

10. The light-emitting device according to claim 9, wherein the functional layer between the anode layer and the light-emitting layer includes the hole transport layer formed as an integral layer common to two or more of the light-emitting layers adjacent to each other in the direction intersecting the stacking direction.

11. A light-emitting device according to claim 9 or 10, wherein the functional layer between the anode layer and the light-emitting layer includes the hole injection layer formed as an integral layer common to two or more of the light-emitting layers adjacent to each other in the one direction intersecting the stacking direction.

12. The light-emitting device according to any one of claims 9 to 11, wherein the hole injection layer comprises a mixture of a hole transport material and an electron acceptor material.

13. The light-emitting device according to any one of claims 9 to 12, wherein the functional layer between the cathode layer and the light-emitting layer is one or more layers selected from the group consisting of the hole-blocking layer, the electron-transporting layer, and the electron-injecting layer, and includes a layer formed as an integrated layer common to two or more of the light-emitting layers adjacent to each other in the direction intersecting the stacking direction.

14. A light-emitting device described in any one of claims 1 to 13, wherein the first electrode layer is independently arranged corresponding to two or more adjacent light-emitting layers in the one direction intersecting the stacking direction, and the second electrode layer is formed as an integrated layer common to two or more adjacent light-emitting layers in the one direction intersecting the stacking direction.

15. A display device comprising a light-emitting device according to any one of claims 1 to 14.

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