Self-luminous element and self-luminous display panel

Abstract

To secure a hole block property, an electron injection property, and environmental resistance to improve an element life.SOLUTION: A self-luminous element comprises: a pixel electrode; a luminous layer that is disposed above the pixel electrode and contains luminescent material; a first functional layer that is disposed on the luminous layer and is made from metal fluoride; a second functional layer that is disposed on the first functional layer, contains first organic material having at least one of an electron transport property and an electron injection property, and does not contain one or more metallic elements selected from an alkaline metal, alkaline earth metal, and rare earth elements and having a property of reducing metal fluoride; and a counter electrode disposed above the second functional layer.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a self-luminous element and a self-luminous display panel. [Background technology]

[0002] In recent years, organic EL panels, which are self-luminous displays using organic EL (Electro Luminescence) elements that utilize the electroluminescence phenomenon of organic materials and in which multiple organic EL elements are arranged in a matrix direction on a substrate, have been put to practical use as displays for electronic devices. Each organic EL element has a basic structure in which multiple functional layers, such as an electron transport layer, including an organic light-emitting layer containing an organic light-emitting material, are laminated between a pair of electrodes, an anode and a cathode, and is a current-driven light-emitting element that is generated when a voltage is applied between the pair of electrodes during operation and holes injected from the anode into the organic light-emitting layer are recombined with electrons injected from the cathode into the organic light-emitting layer.

[0003] In such organic EL elements, it is required to appropriately align the lowest unoccupied molecular orbital (LUMO: Lowest Unoccupied Molecular Orbital) and the highest occupied molecular orbital (HOMO: Highest Occupied Molecular Orbital) of each functional layer to improve the carrier balance between holes and electrons in the light-emitting layer, thereby achieving high efficiency and long life of the light-emitting element.

[0004] In response to this, for example, Patent Document 1 proposes a light-emitting device in which an intermediate layer made of an alkali metal fluoride is provided between an electron transport layer made of an organic material and an organic light-emitting layer, and a metal material having a low work function is doped into the electron transport layer, thereby improving the electron injection property and the device life.

[0005] Furthermore, Patent Document 2 proposes a light-emitting device in which a hole blocking layer (HBL) is provided as an adjacent layer to the light-emitting layer on the cathode side. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. WO2015-194189 [Patent Document 2] JP 2007-36175 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the configuration described in Patent Document 1, in which an intermediate layer made of an alkali metal fluoride is disposed as an adjacent layer to the cathode side of the light-emitting layer, the hole blocking ability from the light-emitting layer to the intermediate layer is low, and sufficient device life is not obtained. In addition, in the configuration described in Patent Document 2, in which a hole blocking layer is disposed as an adjacent layer to the cathode side of the light-emitting layer, the electron injection ability from the hole blocking layer to the light-emitting layer is low, and moisture and the like in the light-emitting layer penetrates into the electron transport layer, resulting in poor environmental resistance and insufficient device life.

[0008] In view of the above circumstances, an object of the present disclosure is to provide a self-luminous element and a self-luminous display panel that ensure hole blocking properties, electron injection properties, and environmental resistance, and improves element life. [Means for solving the problem]

[0009] In order to solve the above problems, a self-luminous EL element in one embodiment of the present disclosure comprises a pixel electrode, a light-emitting layer containing a light-emitting material arranged above the pixel electrode, a first functional layer arranged on the light-emitting layer and made of a metal fluoride, a second functional layer arranged on the first functional layer and containing a first organic material having at least one of electron transport properties and electron injection properties, and a counter electrode arranged above the second functional layer, wherein the second functional layer does not contain one or more metal elements selected from alkali metals, alkaline earth metals, and rare earth elements that have reducing properties against the metal fluoride. Effect of the Invention

[0010] In the self-luminous element and the self-luminous display panel according to an aspect of the present disclosure, hole blocking properties, electron injection properties, and environmental resistance are ensured, thereby improving the element life. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing an overall configuration of an organic EL display device according to an embodiment of the present disclosure. [Diagram 2] 2 is a schematic plan view showing an enlarged portion of an image display surface of an electroluminescence panel in the above-mentioned organic electroluminescence display device. FIG. [Diagram 3] FIG. 3 is a schematic cross-sectional view taken along the line AA in FIG. 2. [Figure 4] 1 is a schematic diagram showing a layered structure of an organic EL element 2 according to one embodiment of the present disclosure. [Diagram 5] 1A is a schematic diagram showing the energy levels of the hole blocking / electron transporting layer, the light emitting layer, the electron transporting layer, and the electron injecting and transporting layer in the organic EL element 2, and FIG. 1B is a diagram illustrating the operation. [Figure 6] 1 is a flowchart showing a manufacturing process of an organic EL display panel according to one embodiment of the present disclosure. [Figure 7] 1(a) to 1(d) are partial cross-sectional views that typically show the process for producing an organic EL element. [Figure 8] 8(a) to 8(d) are partial cross-sectional views that diagrammatically show the manufacturing process of the organic EL element following FIG. 7. [Figure 9] 9(a) and 9(b) are partial cross-sectional views that diagrammatically show the manufacturing process of the organic EL element subsequent to FIG. 8. [Figure 10] 10(a) to 10(e) are partial cross-sectional views that diagrammatically show the manufacturing process of the organic EL element subsequent to FIG. [Figure 11] 1A is a schematic diagram showing a laminated structure of an organic EL element 2Z according to Sample 3, and FIG. 1B is a diagram illustrating the operation of the organic EL element 2Z. [Figure 12] 1 shows the experimental results showing the relationship between the film thickness of the hole-blocking / electron-transporting layer (first functional layer) and the element lifetime in an organic EL element 2. [Figure 13]FIG. 2 is a schematic diagram showing a state in which the energy levels of a hole transport layer, a light emitting layer, and an electron injecting and transporting layer in an organic EL element are appropriately balanced. [Figure 14] 1(a) and 1(b) are schematic diagrams showing the laminated structure of conventional organic EL elements 2X and 2Y. [Figure 15] 13(a) and 13(b) are diagrams illustrating the operation of conventional organic EL elements 2X and 2Y. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <<How the invention was developed>> In organic EL elements, it has been necessary to improve the carrier balance between holes and electrons in the light-emitting layer by optimally designing the arrangement of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of each functional layer, thereby achieving high efficiency of the light-emitting element.

[0013] Hereinafter, a method for optimizing carrier movement in the light-emitting layer of an organic EL element will be described with reference to the drawings. Fig. 13 is a schematic diagram showing a state in which the energy levels of the hole transport layer, light-emitting layer, and electron injection transport layer in an organic EL element are appropriately set.

[0014] As shown in the figure, when a voltage is applied between the pixel electrode (anode) and the counter electrode (cathode), holes are supplied from the pixel electrode through the hole transport layer to the highest occupied molecular orbital (HOMO) of the light-emitting layer, and electrons are supplied from the counter electrode through the electron injection transport layer to the lowest unoccupied molecular orbital (LUMO) of the light-emitting layer. Then, the holes supplied to the light-emitting layer from the hole transport layer side and the electrons supplied to the light-emitting layer from the electron injection transport layer side recombine in the light-emitting layer to generate an excited state and emit light.

[0015] In this recombination, if a good carrier balance is maintained and the electrons and holes injected into the light-emitting layer are quantitatively balanced, the electrons and holes are recombined with little excess or deficiency, so that few residual holes or electrons are generated, and many holes and electrons can contribute to light emission, optimizing the light-emitting efficiency of the organic EL element.

[0016] FIGS. 14(a) and 14(b) are schematic diagrams showing the layered structure of the main part (the part from the anode to the cathode: hereinafter also referred to as the "light-emitting part") of conventional organic EL elements 2X and 2Y described in Patent Documents 1 and 2, respectively, and FIGS. 15(a) and 15(b) are explanatory diagrams of the operation of organic EL elements 2X and 2Y, respectively.

[0017] 14(a), in the organic EL element 2X, a light-emitting portion is formed by stacking a hole injection layer 15, a hole transport layer 16, an organic light-emitting layer 17 (hereinafter sometimes referred to as "light-emitting layer 17"), an intermediate layer 18X made of a material with high electron injection properties, an electron injection transport layer 19X, and a counter electrode 20 on a pixel electrode 13. The intermediate layer 18X is composed of an intermediate layer made of an alkali metal fluoride, for example, a layer made of a metal compound such as sodium fluoride, and the electron injection transport layer 19X adjacent to the cathode side is configured such that the alkali metal fluoride of the intermediate layer is reduced by a metal element M1 with a low work function selected from doped alkali metals or alkaline earth metals, for example, barium, cesium, lithium, etc., and the alkali metal is partially dissociated, thereby enhancing electron injection properties.

[0018] In general, organic layers 17 including the organic light-emitting layer have a tendency to easily absorb and transmit moisture. In addition, metal element M1 has an active nature and tends to react with moisture in light-emitting layer 17, deteriorating the characteristics and shortening the element life.

[0019] In contrast, in the organic EL element 2X, an intermediate layer 18X made of an alkali metal fluoride is provided between the electron injection transport layer 19X and the light-emitting layer 17 to prevent moisture and the like in the light-emitting layer 17 from penetrating into the electron injection transport layer 19X, thereby improving environmental resistance, and also improving the electron injection property from the intermediate layer 18X to the light-emitting layer 17 by reducing a part of the metal compound in the intermediate layer 18X by the metal element M1 contained in the electron injection transport layer 19X and partially dissociating into an alkali metal.

[0020] According to the inventors' investigations, in the organic EL element 2X, as shown in FIG. 15(a), the intermediate layer 18X made of a material having a higher electron injection property than the hole blocking layer 18Y is employed as an adjacent layer on the cathode side of the light-emitting layer 17, thereby improving the electron injection property into the light-emitting layer 17 and preventing a shortage of electrons in the light-emitting layer 17.

[0021] However, in the organic EL element 2X, the intermediate layer 18X, which has a smaller absolute value of the HOMO level than the hole blocking layer 18Y described later, is provided as an adjacent layer on the cathode side of the light emitting layer 17, and therefore the blocking of holes and excitons from the light emitting layer 17 to the electron injection transport layer 19X is insufficient. Furthermore, the inventors' study suggests that the blocking ability of the intermediate layer 18X against holes and excitons is reduced by a metal element contained in the electron injection transport layer 19X, which reduces the blocking ability of the intermediate layer 18X against holes and excitons. If the hole blocking ability is low, holes will enter the electron injection transport layer 19X side and combine with electrons in the electron injection transport layer 19X to generate excitons, which will cause deterioration of the electron injection transport layer 19X and reduce the device life. If the blocking ability against excitons is low, it is assumed that excitons generated in the light emitting layer 17 will diffuse to the electron injection transport layer 19X, which will cause deterioration of the electron injection transport layer 19X and reduce the device life.

[0022] Furthermore, the presence of the metal compound in the intermediate layer 18X makes it possible to prevent the penetration of moisture and the like in the light-emitting layer 17 into the electron injecting and transporting layer 19X and thereby improve the environmental resistance. However, there is a concern that a part of the metal compound in the intermediate layer 18X may be reduced by the metal element contained in the electron injecting and transporting layer 19X, causing the metal compound to dissociate and resulting in a decrease in the environmental resistance of the intermediate layer 18X.

[0023] On the other hand, in the organic EL element 2Y, as shown in FIG. 14(b), the light-emitting portion is formed by stacking a hole injection layer 15, a hole transport layer 16, an emitting layer 17, a hole blocking layer 18Y (HBL), an electron injection transport layer 19Y and a counter electrode 20 on the pixel electrode 13.

[0024] 15(b), in the organic EL element 2Y, the hole blocking layer 18Y, which has a higher absolute value of the HOMO level than the light emitting layer 17, is used as an adjacent layer on the cathode side of the light emitting layer 17, thereby blocking the movement of holes and excitons from the light emitting layer 17 to the electron injecting and transporting layer 19Y. This makes it possible to confine holes in the light emitting layer 17 and increase the ratio of holes that combine with electrons, and to efficiently convert the energy of excitons into light.

[0025] However, the hole blocking layer 18Y made of an organic material is insufficient in terms of the function of preventing the penetration of moisture and the like in the light-emitting layer 17 into the electron injecting and transporting layer 19Y and enhancing the environmental resistance, and is therefore expected to cause deterioration of the active electron injecting and transporting layer 19Y, leading to a decrease in the electron injection ability and a deterioration in the carrier balance, thereby shortening the element life.

[0026] In particular, in organic EL elements manufactured using a wet process in which a solution containing an organic material and a solvent for forming an organic layer, which allows for low cost, (hereinafter simply referred to as "ink") is applied by a printing device, the amount of residual moisture in the organic layer is much greater than in cases where a film is formed by a dry process such as a vapor deposition method, and there is concern that moisture in the underlying organic layer will penetrate into the electron injecting and transporting layer and react with alkali metals and the like in the electron injecting and transporting layer, resulting in significant deterioration of the light-emitting characteristics. Therefore, there has been a demand for further improvement in environmental resistance in element configurations in which the light-emitting layer is made of a coating film.

[0027] In order to solve the above problems, the inventors have conducted extensive research into a layered structure of an organic EL element that ensures hole blocking properties, electron injection properties, and environmental resistance and improves element life, and have arrived at an organic EL element and an organic EL display panel according to one embodiment of the present disclosure.

[0028] <<Summary of the Mode for Carrying Out the Invention>> A self-luminous element according to one aspect of the present disclosure includes a pixel electrode, a light-emitting layer containing a light-emitting material arranged above the pixel electrode, a first functional layer arranged on the light-emitting layer and made of a metal fluoride, a second functional layer arranged on the first functional layer and containing a first organic material having at least one of electron transport properties and electron injection properties, and a counter electrode arranged above the second functional layer, wherein the second functional layer does not contain one or more metal elements selected from alkali metals, alkaline earth metals, and rare earth elements that have a reducing property with respect to the metal fluoride. In another aspect, the metal fluoride may be a fluoride of an alkali metal, an alkaline earth metal, or a rare earth element. In another aspect, the metal fluoride may be sodium fluoride.

[0029] With this configuration, a metal element having a reducing property for a metal fluoride such as sodium fluoride spreads to the first functional layer, reducing the metal fluoride such as sodium fluoride constituting the first functional layer, preventing partial dissociation of sodium, preventing a decrease in hole blocking property, and improving the electron injection property from the first functional layer to the light-emitting layer. This ensures the hole blocking property and the electron injection property, and improves the carrier balance in the light-emitting layer.

[0030] In addition, by preventing dissociation of sodium fluoride in the first functional layer, it is possible to suppress the penetration of moisture and the like in the light-emitting layer into the second functional layer, thereby improving environmental resistance. As a result, the self-luminous element and the self-luminous display panel can ensure hole blocking properties, electron injection properties, and environmental resistance, and can improve the element life.

[0031] In another aspect, in any of the above aspects, the metal element may be one or more metal elements selected from barium, lithium, cesium, and ytterbium.

[0032] With this configuration, it is possible to specifically realize a self-luminous element that ensures hole blocking properties and electron injection properties, improves the carrier balance in the light-emitting layer, and improves the element life.

[0033] In another aspect, in any of the above aspects, the first functional layer may have a thickness of 5 nm or less.

[0034] With this configuration, the element life can be increased sharply compared to ranges other than the above.

[0035] In another aspect, in any of the above aspects, the first functional layer may have a thickness of 1 nm or more and 5 nm or less.

[0036] With this configuration, the element life can be further increased.

[0037] In another aspect, in any of the above aspects, the second functional layer may have a thickness of 5 nm or more and 30 nm or less.

[0038] With this configuration, the metal elements contained in the third functional layer (electron injection transport layer) can be prevented from spreading to the first functional layer and reducing sodium fluoride in the first functional layer, while improving the electron injection property into the light-emitting layer.

[0039] In another aspect, in any of the above aspects, the first functional layer may have a thickness equal to or less than the thickness of the second functional layer.

[0040] With this configuration, the electron injection properties of the first functional layer can be ensured.

[0041] In another embodiment, in any of the above embodiments, a third functional layer may be provided on the second functional layer and below the counter electrode, the third functional layer being formed by doping a second organic material having at least one of electron transport and / or electron injection properties with one or more metal elements selected from alkali metals, alkaline earth metals, and rare earth metals. In another embodiment, in any of the above embodiments, a third functional layer may be provided on the second functional layer and below the counter electrode, the third functional layer being formed of one or more metal elements selected from alkali metals, alkaline earth metals, and rare earth metals. The third functional layer may be formed of ytterbium.

[0042] With this configuration, the presence of the second functional layer (electron transport layer) that does not contain a metal element having reducibility to metal fluorides such as sodium fluoride prevents the influence of the metal elements contained in the third functional layer (electron injection transport layer) from spreading to the sodium fluoride in the first functional layer. Therefore, the content of the metal elements contained in the third functional layer can be optimally set for the electron injection and electron transport properties of the third functional layer. There is no need to determine the content of the metal elements in the third functional layer in consideration of the reducibility of sodium fluoride in the first functional layer, and the electron injection and electron transport properties of the third functional layer can be further improved.

[0043] In another aspect, in any of the above aspects, the metal element contained in the third functional layer may be different from the metal element contained in the first functional layer.

[0044] With this configuration, a first functional layer made of sodium fluoride can be realized.

[0045] In another aspect, in any of the above aspects, the pixel electrode may be light reflective, and the counter electrode may be semi-transparent.

[0046] With this configuration, a top emission type self-luminous element can be realized.

[0047] In another aspect, in any of the above aspects, a fourth functional layer may be provided above the pixel electrode and below the light-emitting layer, the fourth functional layer including an organic material having at least one of hole transport properties and hole injection properties.

[0048] With this configuration, at least one of the hole injection property and the hole transport property from the pixel electrode is improved, and the supply of holes to the light emitting layer is promoted, thereby making it possible to achieve high efficiency.

[0049] In another aspect, in any of the above aspects, the film thickness of at least one of the light emitting layer and the fourth functional layer may be configured to vary depending on the wavelength of light emitted by the light emitting layer.

[0050] With this configuration, it becomes easier to construct an optical resonator structure, and it is expected that the light emission efficiency will be improved.

[0051] In another aspect, in any of the above aspects, at least one of the light emitting layer and the fourth functional layer may be a coating film.

[0052] With this configuration, the manufacturing cost can be reduced by adopting a wet process. When forming a film by a wet process, the amount of remaining impurities such as moisture increases compared to the case of a dry process, but the sodium fluoride contained in the first functional layer suppresses deterioration of the second functional layer and the third functional layer due to the remaining moisture, thereby making it possible to extend the life of the functional layer.

[0053] In another aspect, in any of the above aspects, a self-luminous display panel may be formed by arranging a plurality of self-luminous elements according to any one of claims 1 to 12 in a matrix above a substrate, and the light-emitting layers of adjacent self-luminous elements in the row direction are separated by banks extending in the column direction.

[0054] With this configuration, it is possible to realize a self-luminous display panel that ensures hole blocking properties and electron injection properties, improves the carrier balance in the light-emitting layer, and improves the element life.

[0055] <Embodiment> Hereinafter, an organic EL element, an organic EL panel, and an organic EL display device as a self-luminous element and a self-luminous display panel according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings include schematic drawings, and the scale and aspect ratio of each component may differ from the actual ones.

[0056] 1. Overall configuration of organic EL display device 1 1 is a block diagram showing the overall configuration of an organic EL display device 1. The organic EL display device 1 is a display device used in, for example, televisions, personal computers, mobile terminals, commercial displays (electronic signboards, large screens for commercial facilities), and the like.

[0057] The organic EL display device 1 includes an organic EL display panel 10 (hereinafter referred to as "display panel 10") and a drive control unit 200 electrically connected thereto.

[0058] In this embodiment, the display panel 10 is a top-emission type display panel whose upper surface is a rectangular image display surface. In the display panel 10, a plurality of organic EL elements (not shown) are arranged along the image display surface, and an image is displayed by combining the light emitted by each organic EL element. As an example, the display panel 10 employs an active matrix system.

[0059] The drive control unit 200 has a drive circuit 210 connected to the display panel 10, and a control circuit 220 connected to an external device such as a computer or a receiving device such as an antenna. The drive circuit 210 has a power supply circuit that supplies power to each organic EL element, a signal circuit that applies a voltage signal that controls the power supplied to each organic EL element, a scanning circuit that switches the location to which the voltage signal is applied at regular intervals, and the like.

[0060] The control circuit 220 controls the operation of the drive circuit 210 in response to data including image information input from an external device or a receiving device.

[0061] 1, as an example, four drive circuits 210 are arranged around the display panel 10, but the configuration of the drive control unit 200 is not limited to this, and the number and positions of the drive circuits 210 can be changed as appropriate. For the sake of explanation, the direction along the long side of the upper surface of the display panel 10 is defined as the X direction, and the direction along the short side of the upper surface of the display panel 10 is defined as the Y direction, as shown in FIG.

[0062] 2. Configuration of the display panel 10 (A) Plane configuration 2 is a schematic plan view showing an enlarged portion of the image display surface of the display panel 10. In the display panel 10, as an example, sub-pixels 100R, 100G, and 100B that emit light in R (red), G (green), and B (blue) (hereinafter also simply referred to as R, G, and B) are arranged in a matrix. The sub-pixels 100R, 100G, and 100B are alternately arranged in the X direction, and a set of sub-pixels 100R, 100G, and 100B arranged in the X direction constitutes one pixel P. In the pixel P, full color can be expressed by combining the emission luminance of the sub-pixels 100R, 100G, and 100B, which are grayscale-controlled.

[0063] In the Y direction, subpixel columns CR, CG, and CB are formed by arranging only subpixels 100R, 100G, and 100B, respectively. As a result, pixels P are arranged in a matrix along the X and Y directions in the entire display panel 10, and an image is displayed on the image display surface by combining the colors of the pixels P arranged in this matrix.

[0064] The sub-pixels 100R, 100G, and 100B are provided with organic EL elements 2(R), 2(G), and 2(B) (see FIGS. 2 and 3) that emit R, G, and B colors, respectively.

[0065] The display panel 10 according to the present embodiment employs a so-called line bank system, in which a plurality of banks 14, which separate the subpixel columns CR, CG, and CB into one another, are arranged at intervals in the X direction, and in each of the subpixel columns CR, CG, and CB, the subpixels 100R, 100G, and 100B share an organic light-emitting layer.

[0066] However, in each of the subpixel columns CR, CG, and CB, multiple pixel regulation layers 141 that insulate the subpixels 100R, 100G, and 100B from each other are arranged at intervals in the Y direction, so that each of the subpixels 100R, 100G, and 100B can emit light independently.

[0067] The height of the pixel regulating layer 141 is lower than the height of the liquid surface when the ink of the organic light emitting layer is applied. In Fig. 2, the bank 14 and the pixel regulating layer 141 are shown by dotted lines, because the pixel regulating layer 141 and the bank 14 are not exposed on the surface of the image display surface but are arranged inside the image display surface.

[0068] (B) Cross-sectional configuration Fig. 3 is a schematic cross-sectional view taken along line AA in Fig. 2. In the display panel 10, one pixel is composed of three sub-pixels that emit R, G, and B light respectively, and each sub-pixel is composed of an organic EL element 2(R), 2(G), or 2(B) that emits light of the corresponding color.

[0069] The organic EL elements 2(R), 2(G), and 2(B) of each luminescent color basically have almost the same configuration, and therefore will be described as the organic EL element 2 when no distinction is required.

[0070] As shown in Figure 3, the organic EL element 2 comprises a substrate 11, an interlayer insulating layer 12, a pixel electrode (anode) 13, a bank 14, a hole injection layer 15, a hole transport layer 16, an emitting layer 17, a hole block / electron transport layer (first functional layer) 18, an electron transport layer (second functional layer) 191, an electron injection transport layer (third functional layer) 192, a counter electrode (cathode) 20, and a sealing layer 21.

[0071] The substrate 11, the interlayer insulating layer 12, the hole blocking / electron transport layer 18, the electron transport layer 191, the electron injection transport layer 192, the counter electrode 20, and the sealing layer 21 are not formed for each pixel, but are formed in common to the multiple organic EL elements 2 included in the display panel 10.

[0072] (1) Circuit Board The substrate 11 includes a base material 111 made of an insulating material, and a TFT (Thin Film Transistor) layer 112. A drive circuit is formed for each subpixel in the TFT layer 112. The base material 111 may be, for example, a glass substrate, a quartz substrate, a silicon substrate, a metal substrate such as molybdenum sulfide, copper, zinc, aluminum, stainless steel, magnesium, iron, nickel, gold, or silver, a semiconductor substrate such as gallium arsenide, or a plastic substrate.

[0073] The plastic material may be either a thermoplastic resin or a thermosetting resin. Examples of the plastic material include polyethylene, polypropylene, polyamide, polyimide (PI), polycarbonate, acrylic resin, polyethylene terephthalate (PET), polybutylene terephthalate, polyacetal, other fluorine resins, various thermoplastic elastomers such as styrene, polyolefin, polyvinyl chloride, polyurethane, fluorine rubber, and chlorinated polyethylene, epoxy resin, unsaturated polyester, silicone resin, polyurethane, etc., or copolymers, blends, and polymer alloys mainly made of these, and a laminate of one or more of these may be used.

[0074] (2) Interlayer insulation layer The interlayer insulating layer 12 is formed on the substrate 11. The interlayer insulating layer 12 is made of a resin material and serves to flatten steps on the upper surface of the TFT layer 112. An example of the resin material is a positive-type photosensitive material. Examples of such photosensitive materials include acrylic resins, polyimide resins, siloxane resins, and phenol resins. Although not shown in the cross-sectional view of FIG. 3, the interlayer insulating layer 12 has contact holes formed for each subpixel.

[0075] (3) Pixel electrode The pixel electrode 13 includes a metal layer made of a light-reflective metal material, and is formed on the interlayer insulating layer 12. The pixel electrode 13 is provided for each sub-pixel, and is electrically connected to the TFT layer 112 through a contact hole (not shown). In the present embodiment, the pixel electrode 13 functions as an anode.

[0076] Specific examples of metal materials having light reflectivity include Ag (silver), Al (aluminum), aluminum alloys, Mo (molybdenum), APC (an alloy of silver, palladium, and copper), ARA (an alloy of silver, rubidium, and gold), MoCr (an alloy of molybdenum and chromium), MoW (an alloy of molybdenum and tungsten), and NiCr (an alloy of nickel and chromium).

[0077] The pixel electrode 13 may be composed of a metal layer alone, or may have a laminated structure in which a layer made of a metal oxide such as ITO (indium tin oxide) or IZO (indium zinc oxide) is laminated on a metal layer.

[0078] (4) Bank / pixel control layer The bank 14 divides the pixel electrodes 13 arranged for each sub-pixel above the substrate 11 into columns in the X direction (see FIG. 2), and has a line bank shape extending in the Y direction between the sub-pixel columns CR, CG, and CB aligned in the X direction.

[0079] An electrically insulating material is used for this bank 14. Specific examples of the electrically insulating material include insulating organic materials (for example, acrylic resins, polyimide resins, novolac resins, phenol resins, etc.).

[0080] The bank 14 functions as a structure for preventing the applied inks of each color from overflowing and mixing when the light-emitting layer 17 is formed by a coating method.

[0081] When a resin material is used, it is preferable that the resin material has photosensitivity from the viewpoint of processability. The photosensitivity may be either positive or negative.

[0082] It is preferable that the banks 14 have resistance to organic solvents and heat, and that the surface of the banks 14 has a predetermined liquid repellency in order to prevent the outflow of ink.

[0083] In the portion where the pixel electrode 13 is not formed, the bottom surface of the bank 14 contacts the upper surface of the interlayer insulating layer 12 .

[0084] The pixel regulation layer 141 is made of an electrically insulating material, covers the ends of the pixel electrodes 13 adjacent to each other in the Y direction (FIG. 2) in each subpixel column, and separates the pixel electrodes 13 adjacent to each other in the Y direction.

[0085] The film thickness of the pixel regulating layer 141 is set to be slightly larger than the film thickness of the pixel electrode 13, but smaller than the thickness to the upper surface of the light emitting layer 17. As a result, the light emitting layers 17 in each of the subpixel columns CR, CG, and CB are not partitioned by the pixel regulating layer 141, and the flow of ink is not impeded when forming the light emitting layers 17. This makes it easy to make the thickness of the light emitting layers 17 in each subpixel column uniform.

[0086] Due to the above-mentioned structure, the pixel regulation layer 141 improves the electrical insulation between adjacent pixel electrodes 13 in the Y direction, while suppressing discontinuities in the light-emitting layer 17 in each sub-pixel column CR, CG, CB, and improving the electrical insulation between the pixel electrodes 13 and the counter electrode 20.

[0087] Specific examples of the electrical insulating material used for pixel regulating layer 141 include the resin materials and inorganic materials exemplified above as the materials for bank 14. In addition, it is preferable that the surface of pixel regulating layer 141 has lyophilicity to ink so that ink can easily wet and spread when forming light emitting layer 17, which is the upper layer.

[0088] (5) Hole injection layer The hole injection layer 15 is provided in the opening 14a on the pixel electrode 13 for the purpose of promoting the injection of holes (positive holes) from the pixel electrode 13 to the light-emitting layer 17. The hole injection layer 15 is a layer made of an oxide of, for example, silver (Ag), molybdenum (Mo), chromium (Cr), vanadium (V), tungsten (W), nickel (Ni), iridium (Ir), or a conductive polymer material such as PEDOT (a mixture of polythiophene and polystyrene sulfonic acid). Of the above, the hole injection layer 15 made of a metal oxide has the function of injecting holes into the light-emitting layer 17 by stably injecting holes or by assisting in the generation of holes. In this embodiment, the hole injection layer 15 is formed of a conductive polymer material such as PEDOT (a mixture of polythiophene and polystyrene sulfonic acid) by a wet process such as a printing method.

[0089] (6) Hole transport layer The hole transport layer 16 has a function of transporting holes injected from the hole injection layer 15 to the light emitting layer 17. The hole transport layer 16 is made of a material such as an arylamine derivative, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazoline derivative and a pyrazolone derivative, a phenylenediamine derivative, an amino-substituted chalcone derivative, an oxazole derivative, a styrylanthracene derivative, a fluorenone derivative, a hydrazone derivative, a stilbene derivative, a butadiene compound, a polystyrene derivative, a hydrazone derivative, a triphenylmethane derivative, a tetraphenylbenzine derivative, or the like, or a combination thereof.

[0090] Alternatively, the conductive layer may be formed by a wet process such as a printing method using a polymer compound such as polyfluorene or a derivative thereof, or polyarylamine or a derivative thereof that does not have a hydrophilic group.

[0091] (7) Organic light-emitting layer The light-emitting layer 17 is formed in the opening 14a, and has a function of emitting light of each color R, G, and B by recombination of holes and electrons. When it is necessary to particularly specify the emitted colors, they will be referred to as light-emitting layers 17(R), 17(G), and 17(B).

[0092] Known materials can be used as the organic light-emitting material used in the light-emitting layer 17. For example, oxinoid compounds, perylene compounds, coumarin compounds, azacoumarin compounds, oxazole compounds, oxadiazole compounds, perinone compounds, pyrrolopyrrole compounds, naphthalene compounds, anthracene compounds, fluorene compounds, fluoranthene compounds, tetracene compounds, pyrene compounds, coronene compounds, quinolone compounds and azaquinolone compounds, pyrazoline derivatives and pyrazolone derivatives, rhodamine compounds, chrysene compounds, phenanthrene compounds, cyclopentadiene compounds, stilbene compounds, diphenylquinone compounds, styryl compounds, butadiene compounds, dicyanomethylene compounds, and the like. Fluorescent substances such as pyran compounds, dicyanomethylenethiopyran compounds, fluorescein compounds, pyrylium compounds, thiapyrylium compounds, selenapyrylium compounds, telluropyrylium compounds, aromatic aldadiene compounds, oligophenylene compounds, thioxanthene compounds, anthracene compounds, cyanine compounds, acridine compounds, metal complexes of 8-hydroxyquinoline compounds, metal complexes of 2-bipyridine compounds, complexes of Schiff salts with Group III metals, metal oxine complexes, and rare earth complexes, as well as known phosphorescent substances such as phosphorescent metal complexes such as tris(2-phenylpyridine)iridium, can be used.

[0093] (8) Hole-blocking / electron-transporting layer 18 (first functional layer) The hole blocking / electron transport layer 18 has a function of blocking the movement of holes and excitons from the light emitting layer 17 to the electron transport layer 191, and also transporting electrons from the counter electrode 20 to the light emitting layer 17. The hole blocking / electron transport layer 18 has a function of preventing holes injected from the pixel electrode 13 from passing through the light emitting layer 17 and being injected into the electron transport layer 191 without contributing to recombination, thereby confining the holes within the light emitting layer 17, and also prevents the excitation energy generated in the light emitting layer 17 from transferring to molecules in the electron transport layer 191. This makes it possible to suppress a decrease in the light emitting efficiency and a decrease in the life of the element.

[0094] The hole blocking / electron transporting layer 18 is disposed adjacent to the cathode side of the light emitting layer 17, and is a first functional layer formed by depositing a metal fluoride, for example, sodium fluoride (NaF), by vapor deposition.

[0095] The hole blocking / electron transporting layer 18 can improve the electron transporting property by being formed of sodium fluoride having a predetermined thickness. Also, sodium fluoride is not reduced by metal elements M1 and M2 described later, and therefore exists as a compound in the hole blocking / electron transporting layer 18. In this way, by preventing dissociation of sodium fluoride, it is possible to prevent a decrease in the hole blocking property.

[0096] In addition, the metal fluoride other than sodium fluoride may be a fluoride of an alkali metal, an alkaline earth metal, or a rare earth element. For example, ytterbium fluoride (YbF3), lithium fluoride (LiF), and barium fluoride (BaF2) are preferable. Other examples of the alkali metal fluorides that may be used include cerium fluoride (CeF3), lithium fluoride (LiF), and sodium fluoride (NaF); examples of the alkaline earth metal fluorides include calcium fluoride (CaF2), magnesium fluoride (MgF2), and barium fluoride (BaF2); and examples of the rare earth metal fluorides include lanthanum fluoride (LaF3), neodymium fluoride (NdF3), samarium fluoride (SmF3), ytterbium fluoride (YbF3), yttrium fluoride (YF3), and gadolinium fluoride (GdF3).

[0097] The thickness of the hole blocking / electron transporting layer 18 is preferably more than 0 nm and 5 nm or less, more preferably 1 nm or more and 5 nm or less. By containing a predetermined amount of sodium fluoride and having a thickness of 1 nm or more, the layer has a function of blocking the movement of holes and excitons, and by having a thickness of 5 nm or less, the layer has a function of improving the electron injection property into the light emitting layer 17.

[0098] That is, it is possible to optimize carrier movement between the light-emitting layer and the adjacent layer in the hole-blocking / electron-transporting layer 18. Fig. 5(a) is a schematic diagram showing the energy levels of the light-emitting layer, hole-blocking / electron-transporting layer, electron-transporting layer, and electron-injecting / transporting layer in the organic EL element 2, and (b) is an explanatory diagram of the operation.

[0099] The hole blocking / electron transporting layer 18 has a function of blocking the movement of holes and excitons from the light emitting layer 17 to the electron transporting layer 191 by having a lower HOMO level (higher absolute value of HOMO level) of the constituent material than the light emitting layer 17. Specifically, by making the absolute value of the HOMO of the organic material constituting the hole blocking / electron transporting layer 18 6.0 eV or more, it is possible to adopt a configuration in which the difference between the HOMO level of the molecules contained in the hole blocking / electron transporting layer 18 and that of the molecules contained in the light emitting layer 17 (A in FIG. 5(a)) is 0.2 eV or more, more preferably 0.5 eV or more. This makes it possible to block the movement of holes and excitons from the light emitting layer 17 to the electron transporting layer 191, as shown in FIG. 5(b). This makes it possible to prevent a situation in which holes penetrate into the electron injecting transport layer 192 and combine with electrons in the electron injecting transport layer 192 to generate excitons, which cause deterioration of the electron injecting transport layer 192, or a situation in which excitons generated in the light-emitting layer 17 diffuse into the electron injecting transport layer 192, which causes deterioration of the electron injecting transport layer 192 and shortens the life of the element.

[0100] Furthermore, as shown in FIG. 5(b), a part of the sodium fluoride in the hole-blocking / electron-transporting layer 18 is reduced by the metal element contained in the electron-injecting / transporting layer 192, which can prevent the metal compound from dissociating and thus preventing the hole-blocking property and environmental resistance of the hole-blocking / electron-transporting layer 18 from decreasing.

[0101] As described above, by setting the thickness of the hole-blocking / electron-transporting layer 18 to 5 nm or less, it is possible to improve the electron injection from the hole-blocking / electron-transporting layer 18 to the light-emitting layer 17, as shown in Fig. 5(b). This improves the electron injection into the light-emitting layer 17 and improves the carrier balance in the light-emitting layer 17, thereby improving the luminous efficiency and preventing a decrease in the device life due to a decrease in the current density required to ensure a predetermined luminance.

[0102] (9) Electron transport layer, electron injection transport layer: 19 (9-1) Electron transport layer 191 (second functional layer) The electron transport layer 191 has a function of transporting electrons from the counter electrode 20 to the light emitting layer 17. The electron transport layer 191 is disposed adjacent to the cathode side of the hole blocking / electron transport layer 18, and is made of a first organic material having at least one of electron transport and electron injection properties. Examples of the first organic material (host material) include, but are not limited to, π-electron low molecular weight organic materials such as oxadiazole derivatives (OXD), triazole derivatives (TAZ), and phenanthroline derivatives (BCP, Bphen).

[0103] Furthermore, the electron transport layer 191 is configured not to contain one or more metal elements M1 selected from alkali metals, alkaline earth metals, and rare earth elements, such as barium, cesium, lithium, and ytterbium, that have a reducing effect on metal fluorides in the hole blocking / electron transport layer 18, such as sodium fluoride. This prevents the metal element M1 that has a reducing effect on metal fluorides, such as sodium fluoride, from spreading to the hole blocking / electron transport layer 18, reducing the fluorides of the alkali metals that constitute the hole blocking / electron transport layer 18, and partially dissociating the alkali metals. Here, even if the electron transport layer 191 does not contain the above-mentioned metal element M1, it may be permitted to contain the metal element M1 in the electron transport layer 191 to an extent that the metal element M1 does not substantially dissociate the fluorides of the alkali metals that constitute the hole blocking / electron transport layer 18.

[0104] Furthermore, by making the film thickness of the electron transport layer 191 5 nm or more, it is possible to prevent the metal element M2 contained in the electron injection transport layer 192 from spreading to the hole block / electron transport layer 18 and reducing the alkali metal fluoride in the hole block / electron transport layer 18. Furthermore, by making the thickness of the electron transport layer 191 30 nm or less, it is possible to improve the electron injection property into the light-emitting layer 17.

[0105] (9-2) Electron injection transport layer 192 (third functional layer) The electron injecting and transporting layer 192 has a function of injecting and transporting electrons supplied from the counter electrode 20 to the light-emitting layer 17. The electron injecting and transporting layer 192 may have a configuration in which a second organic material having an electron transporting property is doped with a metal element M2 or the like that enhances the electron transporting property.

[0106] The second organic material (host material) can be selected from the same group of organic materials as the first organic material described above. The second organic material may be the same material as the first organic material, or may be a different material.

[0107] As the metal element M2, alkali metals, alkaline earth metals, and rare earth elements, for example, low work function metals such as lithium, barium, calcium, potassium, cesium, sodium, and rubidium, low work function metal salts selected from lithium fluoride, ytterbium, and the like, low work function metal oxides such as barium oxide, and low work function metal organic complexes such as lithium quinolinol are used. When lithium quinolinol is contained in the electron injecting and transporting layer 192, it may be reduced by the metal material of the counter electrode 20, and the lithium quinolinol in the electron injecting and transporting layer 192 may be dissociated and exist as lithium.

[0108] The electron injecting and transporting layer 192 may be made of one or more metal elements selected from the group consisting of alkali metals, alkaline earth metals, and rare earth metals. In this case, the metal element may be ytterbium.

[0109] (10) Counter electrode The counter electrode 20 is made of a light-transmitting conductive material, and is formed on the electron injecting and transporting layer 192. The counter electrode 20 functions as a cathode.

[0110] The counter electrode 20 may be, for example, a metal thin film or a transparent conductive film such as ITO or IZO. In order to obtain an optical resonator structure more effectively, it is preferable to form a metal thin film made of at least one material selected from the group consisting of aluminum, magnesium, silver, an aluminum-lithium alloy, and a magnesium-silver alloy as the material of the counter electrode 20. In this case, it is preferable that the thickness of the metal thin film is 5 nm or more and 30 nm or less. This makes the counter electrode 20 semi-transparent, and an optical resonator structure can be constructed between the pixel electrode 13 and each reflective surface of the counter electrode 20, thereby further improving the luminous efficiency.

[0111] In addition, when the optical resonator structure as described above is adopted, it is desirable to form a transparent conductive film such as ITO or IZO with a desired thickness between the electron injection transport layer 192 and the counter electrode 20, and adjust the optical distance between the light emitting layer 17 and the counter electrode 20 to an appropriate size.

[0112] Moreover, a transparent conductive film such as ITO or IZO may be formed on the counter electrode 20 to adjust the chromaticity and viewing angle.

[0113] (11) Sealing layer The sealing layer 21 is provided to prevent organic layers such as the hole transport layer 16, the light emitting layer 17, the electron transport layer 191, and the electron injection transport layer 192 from being deteriorated due to exposure to moisture or air.

[0114] The sealing layer 21 is formed using a light-transmitting material such as silicon nitride (SiN) or silicon oxynitride (SiON).

[0115] (12)Other 3, an anti-glare polarizing plate or an upper substrate may be attached onto the sealing layer 21 via a transparent adhesive. Also, a color filter may be attached to correct the chromaticity of the light emitted by each organic EL element 2. This can further protect the hole transport layer 16, the light emitting layer 17, the electron transport layer 191, the electron injection transport layer 192, etc. from external moisture and air.

[0116] 3. Manufacturing method of organic EL elements A method for manufacturing the organic EL element 2 according to the embodiment will be described below with reference to Fig. 6 to Fig. 10. Fig. 6 is a flow chart showing the manufacturing process of the organic EL element 2, and Fig. 7 to Fig. 10 are cross-sectional views that typically show the manufacturing process of the organic EL element 2.

[0117] (1) Board preparation process First, as shown in Fig. 7(a), the substrate 11 is prepared by forming the TFT layer 112 on the base material 111 (Step S1 in Fig. 6). The TFT layer 112 can be formed by a known method for manufacturing a TFT.

[0118] (2) Interlayer insulation layer formation process Next, as shown in Fig. 7(b), an interlayer insulating layer 12 is formed on the substrate 11 (Step S2 in Fig. 6).

[0119] Specifically, a resin material having a certain degree of fluidity is applied, for example, by a die coating method along the upper surface of substrate 11 so as to fill in the irregularities on substrate 11 caused by TFT layer 112. As a result, the upper surface of interlayer insulating layer 12 has a flat shape along the upper surface of base material 111.

[0120] Furthermore, a contact hole (not shown) is formed in the interlayer insulating layer 12 at a location above, for example, the source electrode of the TFT element by dry etching. The contact hole is formed by patterning or the like so that the surface of the source electrode is exposed at the bottom of the contact hole.

[0121] Next, a connection electrode layer is formed along the inner wall of the contact hole. A part of the upper part of the connection electrode layer is disposed on the interlayer insulating layer 12. The connection electrode layer can be formed by, for example, a sputtering method, and after forming a metal film, it may be patterned by using a photolithography method and a wet etching method.

[0122] (3) Pixel electrode formation process 7(c), a pixel electrode material layer 130 is formed on the interlayer insulating layer 12. The pixel electrode material layer 130 can be formed by using, for example, a vacuum deposition method, a sputtering method, or the like.

[0123] Then, as shown in FIG. 7(d), the pixel electrode material layer 130 is patterned by etching to form a plurality of pixel electrodes 13 partitioned into sub-pixels (Step S3 in FIG. 6).

[0124] (4) Bank and pixel regulation layer formation process Next, the bank 14 and the pixel regulating layer 141 are formed (Step S4 in FIG. 6).

[0125] In this embodiment, the pixel regulating layer 141 and the bank 14 are formed in separate steps.

[0126] (4-1) Pixel regulation layer formation First, in order to divide the pixel electrode row in the Y direction (FIG. 2) into sub-pixels, a pixel regulation layer 141 extending in the X direction is formed.

[0127] 8(a), a photosensitive resin material that is to be the material of pixel regulating layer 141 is uniformly applied onto interlayer insulating layer 12 on which pixel electrode 13 is formed, to form pixel regulating layer material layer 1410. The amount of the resin material applied at this time is determined in advance so that pixel regulating layer 141 will have a target film thickness after drying.

[0128] As a specific coating method, for example, a wet process such as a die coating method, a slit coating method, a spin coating method, etc. After coating, it is preferable to remove unnecessary solvent by performing, for example, vacuum drying and low-temperature heating and drying (pre-baking) at about 60°C to 120°C, and fix the pixel regulating layer material layer 1410 to the interlayer insulating layer 12.

[0129] Then, the pixel regulation layer material layer 1410 is patterned by photolithography.

[0130] For example, when the pixel regulation layer material layer 1410 has positive photosensitivity, the portions to be left as the pixel regulation layer 141 are shielded from light, and the pixel regulation layer material layer 1410 is exposed to light through a photomask (not shown) through which the portions to be removed are transparent.

[0131] Next, development is performed to remove the exposed area of ​​the pixel regulation layer material layer 1410, thereby forming the pixel regulation layer 141. As a specific development method, for example, the entire substrate 11 may be immersed in a developer such as an organic solvent or an alkaline solution that dissolves the part of the pixel regulation layer material layer 1410 that has been exposed to light, and then the substrate 11 may be washed with a rinse liquid such as pure water.

[0132] Thereafter, by baking (post-baking) at a predetermined temperature, pixel regulating layer 141 extending in the X direction can be formed on interlayer insulating layer 12 (FIG. 8(b)).

[0133] (4-2) Bank formation Next, the bank 14 extending in the Y direction is formed in the same manner as the pixel regulating layer 141 described above.

[0134] That is, a resin material for the bank is applied by a die coating method or the like onto the interlayer insulating layer 12 on which the pixel electrodes 13 and pixel regulating layer 141 are formed, to form a bank material layer 140 (FIG. 8(c)). The amount of the resin material applied at this time is determined in advance so that the bank 14 will have the desired height after drying.

[0135] Then, the bank material layer 140 is patterned by photolithography to form the bank 14 extending in the Y direction, and then baked at a predetermined temperature to form the bank 14 (FIG. 8(d)).

[0136] In the above, the material layers of the pixel regulating layer 141 and the bank 14 are formed by a wet process and then patterned. However, it is also possible to form one or both of the material layers by a dry process and then pattern them by photolithography and etching.

[0137] (5) Step of forming the fourth functional layer (hole injection layer, hole transport layer) The fourth functional layer formation step includes forming the hole injection layer 15 and the hole transport layer 16 (Step S5 in FIG. 6).

[0138] First, the hole injection layer 15 is formed by ejecting an ink containing a conductive polymer material such as PEDOT:PSS (a mixture of polythiophene and polystyrene sulfonic acid) from the nozzle 3011 of the application head 301 of the printing device, applying it into the opening 14a, and then volatilizing off the solvent and / or baking the ink.

[0139] The hole transport layer 16 is formed by applying an ink containing the material of the hole transport layer 16 onto the hole injection layer 15, and then volatilizing off the solvent and / or baking the applied ink. The material of the hole transport layer 16 is, for example, a polymer compound such as polyfluorene or a derivative thereof, or polyarylamine or a derivative thereof, which does not have a hydrophilic group. The application method is the same as that for the hole injection layer 15.

[0140] FIG. 9(a) is a schematic cross-sectional view of the display panel 10 when the hole transport layer 16 is being formed after the hole injection layer 15 is formed.

[0141] (6) Organic light-emitting material layer formation process Next, organic light-emitting material layers 170(R), 170(G), and 170(B) (hereinafter, simply referred to as "organic light-emitting material layer 170" without distinguishing between the respective light-emitting colors) are formed above the hole transport layer 16 as precursors of the light-emitting layer 17 (Step S6 in FIG. 6).

[0142] 9(b), ink containing an organic light-emitting material, which is a constituent material of an organic light-emitting layer of an emission color corresponding to each opening 14a, is sequentially discharged from nozzles 3011 of a coating head 301 of a printing device to coat the hole transport layer 16 in the opening 14a, and the substrate 11 after the ink coating is carried into a vacuum drying chamber and heated in a vacuum environment to evaporate the organic solvent in the ink. This allows the organic light-emitting layer 17 to be formed (step S6 in FIG. 6).

[0143] (7) Hole-blocking / electron-transporting layer 18 (first functional layer) formation process 10(a), sodium fluoride is deposited on the organic light-emitting layer 17 and the bank 14 by vacuum deposition or the like to a thickness of more than 0 nm and not more than 5 nm, more preferably 1 nm to 5 nm, for example, to a thickness of 5 nm, to form a hole-blocking / electron-transporting layer 18 (step S7 in FIG. 6). The hole-blocking / electron-transporting layer 18 is formed by depositing the layer in common to each sub-pixel.

[0144] (8) Electron transport layer 191 (second functional layer) formation process As shown in Fig. 10(b), a first organic material having at least one of electron transport and electron injection properties is deposited on the hole blocking / electron transport layer 18 by vacuum deposition to a thickness of 5 nm to 30 nm, for example, 10 nm, to form an electron transport layer 191 (step S8 in Fig. 6). In this case, in the deposition of the electron transport layer 191, the first organic material is deposited so as not to contain one or more metal elements M1 selected from alkali metals, alkaline earth metals, and rare earth elements and having a reducing property with respect to the metal fluorides, for example, sodium fluoride. The electron transport layer 191 is formed by depositing a film in common to each sub-pixel.

[0145] (9) Electron injection transport layer 192 (third functional layer) forming process As shown in FIG. 10(c), a second organic material having at least one of electron transport properties and electron injection properties and a metal element M2, which is a doping metal, are co-deposited on the electron transport layer 191 by vacuum deposition to a thickness of 5 nm to 50 nm, for example, 10 nm, to form an electron injection transport layer 192 (step S9 in FIG. 6). The concentration is a doping concentration in which the weight content ratio of the doping metal is 3 wt to 60 wt%, for example, 10 wt%. Alternatively, a metal thin film selected from alkali metals, alkaline earth metals, and rare earth elements may be used. In this case, the thickness is 0.1 nm to 5 nm, for example, 1 nm, to form the electron injection transport layer 192 (step S9 in FIG. 6). The electron injection transport layer 192 is formed by forming a film in common to each sub-pixel.

[0146] In this manner, the functional layer 19 is formed.

[0147] (10) Counter electrode formation process Next, the counter electrode 20 is formed on the functional layer 19 (Step S10 in FIG. 6).

[0148] In the counter electrode formation step, first, a film of silver, aluminum, or the like is formed on the functional layer 19 by sputtering or vacuum deposition (FIG. 10(d)).

[0149] (11) Sealing layer formation process 10(e), a sealing layer 21 is formed on the counter electrode 20 (Step S11 in FIG. 6). The sealing layer 21 can be formed by depositing SiON, SiN, or the like by a sputtering method, a CVD method, or the like.

[0150] In this manner, the display panel 10 shown in Fig. 3 is manufactured. Note that the above manufacturing method is merely an example and can be appropriately modified according to the purpose.

[0151] 4. Experimental results on element life and driving voltage using organic EL element 2 The element lifetime of the organic EL element 2 was measured by changing the lamination structure from the light-emitting layer 17 to the counter electrode 20. Table 1 shows the measurement results of the element lifetime. The element lifetime in Table 1 is the light-emitting time until the luminance decreases to 97% of the initial value, and is a relative value with sample 1 as the reference.

[0152] [Table 1] As test samples, Nos. 1 to 3 according to comparative examples and sample 4 according to the embodiment were used. The specifications of each sample are shown below. FIG. 11(a) is a schematic diagram showing the layered structure of an organic EL element 2Z according to sample 3, and (b) is an explanatory diagram of the operation. In the organic EL element 2Z, the second functional layer is represented as an electron transport layer 191Z, and the third functional layer is represented as an electron injection transport layer 192Z.

[0153] No. 1: Organic EL element 2X shown in FIG. 14(a): A sample in which a sodium fluoride layer (NaF) is disposed as an adjacent layer on the cathode side of the light-emitting layer 17, and an electron injection transport layer (EIL) made of an organic material doped with a metal element M1 having a reducing property against sodium fluoride is disposed as an adjacent layer on the cathode side. No. 2: Organic EL element 2Y shown in FIG. 14(b): A sample in which a hole blocking layer (HBL) is disposed adjacent to the cathode side of the light-emitting layer 17, and an electron injection transport layer (EIL) made of an organic material doped with a metal element M2 that enhances electron transportability is disposed adjacent to the cathode side. No. 3: In the laminated structure of the organic EL element 2, the adjacent layer (hole blocking / electron transport layer 18) on the cathode side of the light emitting layer 17 is changed to a hole blocking layer (HBL). A laminated structure: A sample in which an electron transport layer (ETL) made of an organic material that does not contain a metal element M1 having a reducing property against sodium fluoride is arranged between the hole blocking layer (HBL) and the electron injection transport layer (EIL). No. 4: In the laminated structure of the organic EL element 2, the thickness of the sodium fluoride layer of the adjacent layer (hole block / electron transport layer 18 (NaF)) on the cathode side of the light emitting layer 17 is set to 5 nm. A sample in which an electron transport layer (ETL) made of an organic material that does not contain a metal element M1 having a reducing property against sodium fluoride is arranged between the hole block / electron transport layer 18 (NaF) and the electron injection transport layer (EIL). The layer structure and thickness of Samples No. 1 and 2 were a hole injection layer [50 nm], a hole transport layer [20 nm], an emission layer [85 nm], an adjacent layer on the cathode side of the emission layer [5 nm], an electron injection transport layer [1 nm], and a counter electrode. The layer structure and thickness of Samples No. 3 and 4 were a structure in which an electron transport layer [10 nm] was provided between the adjacent layer on the cathode side of the emission layer and the electron injection transport layer.

[0154] As shown in Table 1, the order of device lifetime from largest to smallest is Sample 4>Sample 1>Sample 2>Sample 3. Specifically, when the device lifetime of Sample 1 is taken as the standard, the device lifetime of Sample 2 was about 3%, and that of Sample 3 was about 1%. The hole blocking layers in Samples 2 and 3 have high hole blocking properties but low electron injection properties, which deteriorate the carrier balance and reduce the device lifetime. In addition, the function of preventing the penetration of moisture and the like in the light-emitting layer 17 into the electron injection transport layer and increasing environmental resistance is insufficient, which is thought to cause deterioration of the active electron injection transport layer and reduce the device lifetime.

[0155] In contrast, in Sample 4 according to the embodiment, an improvement in life was observed compared to Samples 1 to 3.

[0156] Sample 4 according to the embodiment showed a significant improvement in device life compared to Sample 3. That is, in Sample 3, as shown in Fig. 11(b), the hole blocking layer does not have an adequate function of preventing the penetration of moisture and the like in the light-emitting layer 17 into the electron injection transport layer 192Z and enhancing environmental resistance, so that the device life was short even when the electron transport layer 191Z did not contain the metal element M1. In contrast, it is presumed that the sodium fluoride layer constituting the hole blocking / electron transport layer 18 has excellent environmental resistance, which is the reason why the device life was improved in Sample 4.

[0157] Moreover, it was found that Sample 4 according to the embodiment had an improved element life of 204% compared to Sample 1.

[0158] The reason for this is considered to be that in sample 4, the metal element M1 having a reducing effect against sodium fluoride is not contained in the layer adjacent to the cathode side of the hole blocking / electron transport layer 18, and thus dissociation of sodium fluoride constituting the hole blocking / electron transport layer 18 is prevented, thereby preventing a decrease in hole blocking properties and blocking the movement of holes and excitons. This makes it possible to prevent holes from penetrating the electron injecting / transporting layer 192 side and combining with electrons in the electron injecting / transporting layer 192 to generate excitons, which cause deterioration of the electron injecting / transporting layer 192, or prevents excitons generated in the light emitting layer 17 from diffusing to the electron injecting / transporting layer 192, which causes deterioration of the electron injecting / transporting layer 192 and shortens the life of the device.

[0159] In addition, in sample 4, by preventing dissociation of sodium fluoride in the hole blocking / electron transporting layer 18, it is possible to suppress the penetration of moisture and other substances in the light-emitting layer 17 into the electron transporting layer 191 and the electron injecting / transporting layer 192, and it is believed that this improves environmental resistance compared to sample 1.

[0160] Next, the relationship between the film thickness and the element lifetime was investigated by varying the film thickness of the sodium fluoride layer in the hole-blocking / electron-transporting layer 18 in the organic EL element 2 in stages. Figure 12 shows the experimental results showing the relationship between the film thickness of the hole-blocking / electron-transporting layer 18 (first functional layer) in the organic EL element 2 and the element lifetime. The element lifetime in Figure 12 is a relative value based on the measured value in the above-mentioned sample 1.

[0161] The test samples were samples in which sodium fluoride layers with thicknesses of 0.5, 1, 3, 5, 6, and 7 nm were arranged as the hole blocking / electron transporting layer 18 in the organic EL element 2, and the layered structure, film thickness, and driving voltage drop rate in each sample were the same.

[0162] As shown in FIG. 12, a peak region in which the element lifetime increases sharply was observed in the range of 1 nm or more and 5 nm or less of the thickness of the sodium fluoride layer constituting the hole-blocking / electron-transporting layer 18, compared with the other ranges.

[0163] In this example, a peak was observed in which the element life was further improved in the range of more than 3 nm and not more than 5 nm.

[0164] The reason why the element lifetime drops sharply when the film thickness exceeds 5 nm is thought to be that in the early stages of lifetime, the tunneling barrier increases with increasing film thickness, which deteriorates the electron injection property, electrons accumulate at the interface between the hole blocking / electron transport layer 18 and the electron transport layer, and a strong electric field is applied, which increases the load on the organic material of the electron transport layer and accelerates the deterioration of the electron transport layer. It is presumed that the deterioration of the electron transport layer further deteriorates the electron injection property, accelerating the shortening of the lifetime.

[0165] Moreover, the reason why the element life is reduced when the film thickness is less than 1 nm is considered to be that it is difficult to form a uniform film in the manufacturing process, and the effect of the environmental resistance of the sodium fluoride layer in the hole-blocking / electron-transporting layer 18 is reduced. Also, when the film thickness is less than 1 nm, the hole-blocking property is reduced, the carrier balance is deteriorated, and the element life is reduced.

[0166] In the experiment shown in Fig. 12, the driving voltage was lowest at a film thickness of 5 nm, and the film thickness with the best carrier balance was 5 nm. However, since the carrier balance varies depending on the configuration of other layers in the laminated configuration, such as the electron / hole mobility in the light-emitting layer and the constituent materials of the hole injection layer and hole transport layer, the film thickness with the best carrier balance can be appropriately adjusted by adjusting these factors as well.

[0167] 5. Experimental results of luminous efficiency and driving voltage using organic EL element 2 The driving voltage and luminous efficiency were measured using samples 3 and 4 as test samples. Table 2 shows the measurement results of the driving voltage reduction rate and luminous efficiency. The driving voltage was 1 mA / cm 2 In Table 2, it is expressed as a relative value as the driving voltage reduction rate. The driving voltage reduction rate is [driving voltage before change] / [driving voltage after change]. The driving voltage reduction rate and luminous efficiency in Table 2 are relative values ​​with Sample 3 as the standard.

[0168] [Table 2] As shown in Table 2, in Sample 4 according to the embodiment, the driving voltage reduction rate and the luminous efficiency were improved by about 5% and 18%, respectively, compared to Sample 3. Sample 3 using a hole blocking layer had high hole blocking properties but low electron injection properties, resulting in poor carrier balance in the light-emitting layer and low luminous efficiency. In contrast, Sample 4 according to the embodiment had high electron injection properties compared to Sample 3, and it is believed that the driving voltage was reduced due to the improved carrier balance in the light-emitting layer. Also, it is believed that Sample 4 had high hole blocking properties and electron injection properties, which improved the carrier balance and increased the luminous efficiency.

[0169] In the conventional organic EL element 2X, as described above, the intermediate layer composed of a layer of a metal compound such as sodium fluoride has an improved electron injection property due to reduction of the alkali metal fluoride in the intermediate layer by a metal element M1, such as barium, cesium, or lithium, contained in the adjacent electron injection / transport layer, causing partial dissociation of the alkali metal.

[0170] In contrast, in the organic EL element 2, the electron transport layer 191 does not contain metal elements such as alkali metals, alkaline earth metals, and rare earth elements that have a reducing effect on metal fluorides such as sodium fluoride, and therefore sodium fluoride does not dissociate. Therefore, sodium fluoride in the hole-blocking / electron transport layer 18 exists as a compound. In the organic EL element 2, the reason why the driving voltage drop and luminous efficiency increased in the peak region (FIG. 12) is considered to be that the local presence of sodium fluoride in the first organic material causes local concentration of an electric field on the sodium fluoride, which enhances electron injection due to a tunneling phenomenon, thereby improving the carrier balance of the luminescent layer. On the other hand, according to the inventor's study, the organic EL element 2 shows improvements in the driving voltage drop and luminous efficiency compared to the conventional organic EL element 2X, and therefore it is considered that preventing dissociation of sodium fluoride and having sodium fluoride exist as a compound in the organic EL element 2 also contributes to suppressing the decrease in hole blocking properties.

[0171] Regarding the tunneling phenomenon in organic EL elements, H. Tang et al. (Applied Physics Letters, November 3, 1997, Volume 71, Issue 18, pp. 2560-2562) discloses that by using an aluminum film with an insulating layer made of Al2O3 formed on the electron transport layer side as a cathode that injects electrons into the electron transport layer, electrons are injected into the electron transport layer by the tunneling phenomenon via the Al2O3 layer, improving the current injection efficiency.

[0172] 6. Summary As described above, the organic EL element 2 in the embodiment of the present disclosure is characterized by comprising an emitting layer 17 containing an organic emitting material arranged above the pixel electrode 13, a first functional layer (hole blocking / electron transport layer) 18 arranged on the emitting layer 17 and made of sodium fluoride, a second functional layer (electron transport layer) 191 arranged on the first functional layer 18 and containing a first organic material having at least one of electron transport properties and electron injection properties, and which is selected from alkali metals, alkaline earth metals, and rare earth elements and does not contain one or more metal elements M1 that have a reducing property against metal fluorides such as sodium fluoride, and a counter electrode 20 arranged above the second functional layer.

[0173] With this configuration, the metal element M1 having a reducing property for metal fluorides such as sodium fluoride spreads to the hole blocking / electron transporting layer 18, and the sodium fluoride in the hole blocking / electron transporting layer 18 is reduced, and partial dissociation of sodium is prevented, thereby preventing a decrease in hole blocking property. In addition, the electron injection property to the light emitting layer 17 can be improved. This ensures hole blocking property and electron injection property, and improves the carrier balance in the light emitting layer. Furthermore, by preventing dissociation of sodium fluoride in the hole blocking / electron transporting layer 18, the penetration of moisture and the like in the light emitting layer 17 into the electron injection / transporting layer 192 can be suppressed, and environmental resistance can be improved. This ensures hole blocking property, electron injection property, and environmental resistance in the organic EL element, and improves the element life.

[0174] The metal element M1 may be one or more metal elements selected from barium, lithium, cesium, and ytterbium.

[0175] With this configuration, it is possible to specifically realize an organic EL element that ensures hole blocking properties and electron injection properties, improves the carrier balance in the light-emitting layer, and improves the element life.

[0176] In the conventional organic EL element 2X, as described above, the intermediate layer composed of a layer of a metal compound such as sodium fluoride has enhanced electron injection properties by reducing the alkali metal fluoride in the intermediate layer due to the metal element M1, such as barium, cesium, or lithium, contained in the adjacent electron injection transport layer 19X, thereby partially dissociating the alkali metal.

[0177] In contrast, as described above, the organic EL element 2 has a configuration in which the metal element M1 having a reducing property against metal fluorides such as sodium fluoride is not present in the electron transport layer 191, and therefore the influence of the metal element M2 contained in the electron injection transport layer 192 does not extend to sodium fluoride in the hole block / electron transport layer 18. Therefore, the content of the metal element M2 contained in the electron injection transport layer 192 can be optimally set for the electron injection property and electron transport property of the electron injection transport layer 192. There is no need to determine the content of the metal element M2 in consideration of the reducing property of the alkali metal fluoride in the hole block / electron transport layer 18, and the electron injection property and electron transport property of the electron injection transport layer 192 can be further improved.

[0178] <<Variations>> Although the organic EL element 2 and the like according to the embodiments have been described above, the present invention is not limited to the above embodiments except for the essential characteristic components. For example, the present invention also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art can conceive, and forms realized by arbitrarily combining the components and functions of each embodiment within the scope of the present invention. Below, modified examples of an organic EL element and an organic EL display panel will be described as examples of such forms.

[0179] (1) In the organic EL element according to the embodiment, a hole injection layer and a hole transport layer are present between the pixel electrode and the light emitting layer, but the present invention is not limited to this. For example, a hole transport layer or an electron injection transport layer may be present without using a hole injection layer or a hole transport layer. Also, a hole injection layer, a hole transport layer, or an electron injection transport layer may be included, or a plurality of or all of these layers may be included at the same time. Moreover, all of these layers do not need to be made of organic compounds, and may be made of inorganic substances, etc.

[0180] (2) In the display panel 10 according to the above embodiment, the extension direction of the pixel regulation layer 141 is the direction of the long axis X of the display panel 10, and the extension direction of the bank 14 is the direction of the short axis Y of the display panel 10, as shown in FIG. 2 , however, the extension directions of the pixel regulation layer 141 and the bank 14 may be reversed. In addition, the extension directions of the pixel insulating layer and the bank may be directions unrelated to the shape of the display panel 10.

[0181] Furthermore, in the display panel 10 according to the above embodiment, the image display surface is rectangular as an example, but the shape of the image display surface is not limited and can be changed as appropriate.

[0182] In addition, in the display panel 10 according to the above embodiment, the pixel electrodes 13 are rectangular flat plate-shaped members, but this is not limiting.

[0183] Furthermore, although a line bank type organic EL display panel has been described in the above embodiment, a pixel bank type display panel in which each sub-pixel is surrounded by a bank on all four sides may also be used.

[0184] (3) In the above embodiment, the hole injection layer 15, the hole transport layer 16, and the light-emitting layer 17 are all formed by the printing method (coating method), but only one of them may be a coating film formed by the printing method. Whether or not a particular layer in the finished display panel 10 is a coating film can be easily determined by detecting the moisture or solvent remaining in the film.

[0185] (4) In the above embodiment, the hole injection layer 15 is formed by printing using ink containing a conductive polymer material, but a film of a transition metal oxide may also be formed by vapor deposition or sputtering. A transition metal oxide can have multiple oxidation numbers and therefore multiple levels, which makes it easier to inject holes and reduces the driving voltage. Tungsten oxide is a suitable metal oxide.

[0186] This allows the amount of hole injection to be increased in accordance with the increase in the amount of electron injection, achieving a carrier balance with a greater amount of excitons, and thus a further improvement in luminous efficiency can be expected.

[0187] In this case, the metal material layer and the tungsten oxide layer of the pixel electrode are first laminated, and then the pixel electrode 13 and the hole injection layer 15 are simultaneously formed by patterning using photolithography and wet etching, and then the bank 14 and the pixel regulating layer 141 are formed, thereby simplifying the manufacturing process.

[0188] (5) In the display panel 10 according to the above embodiment, the sub-pixels 100R, 100G, and 100B emitting R, G, and B light, respectively, are arranged, but the emission colors of the sub-pixels are not limited to this and may be, for example, four colors including yellow (Y) in addition to R, G, and B. Furthermore, the number of sub-pixels per color in one pixel P is not limited to one and multiple sub-pixels may be arranged. Furthermore, the arrangement of the sub-pixels in the pixel P is not limited to the order of red, green, and blue as shown in FIG. 2 and may be in an order that interchanges these.

[0189] (6) Furthermore, the display panel 10 according to the above embodiment employs an active matrix system, but is not limited to this, and may employ a passive matrix system.

[0190] Moreover, the present invention can be applied not only to top-emission type organic EL display panels but also to bottle-emission type organic EL display panels.

[0191] In the case of a bottom emission type, the counter electrode 20 is a light-reflective anode, and the pixel electrode 13 is made of a light-transmitting (including semi-light-transmitting) material and is a cathode. Accordingly, the stacking order of the other layers, such as the first functional layer 22, the intermediate layer 18, and the second functional layer 19, is also different.

[0192] The present invention can also be applied to self-luminous display panels such as quantum dot display devices that use colloidal quantum dots.

[0193] <Additional Information> The above-described embodiments each show a preferred specific example of the present invention. The numerical values, shapes, materials, components, the arrangement and connection of the components, steps, and the order of steps shown in the embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the embodiments, steps that are not described in the independent claims showing the highest concept of the present invention are described as optional components constituting a more preferred embodiment.

[0194] The order in which the above steps are performed is merely an example for specifically explaining the present invention, and the steps may be performed in an order other than the above. Some of the steps may be performed simultaneously (in parallel) with other steps.

[0195] In order to facilitate understanding of the invention, the scale of the components in the drawings may differ from the actual scale. Furthermore, the present invention is not limited to the description of the above embodiments, and can be modified as appropriate without departing from the gist of the present invention.

[0196] Furthermore, at least some of the functions of each of the embodiments and their modified examples may be combined.

[0197] Furthermore, various modifications of the present embodiment that are within the scope of what would occur to a person skilled in the art are also included in the present invention. [Industrial Applicability]

[0198] The organic EL element and the like according to the present disclosure can be suitably used in, for example, a method for producing an organic EL element and an organic EL panel used as various display devices, television devices, displays for portable electronic devices, and the like, for home or public facilities, or for commercial use. [Explanation of symbols]

[0199] 1 Organic EL display device 2. Organic EL elements 10 Organic EL Panel 11 Substrate 12 Interlayer insulation layer 13 Pixel electrode (anode) 15 Hole injection layer 16 Hole transport layer 17 Emitting layer 170 Organic light-emitting material layer 18 Hole blocking / electron transport layer (first functional layer) 19 Electron transport layer / electron injection transport layer 191 Electron transport layer (second functional layer) 192 Electron injection transport layer (third functional layer) 20 Counter electrode (cathode) 21 Sealing layer 23 Transparent conductive film

Claims

1. A pixel electrode; a light-emitting layer including a light-emitting material disposed above the pixel electrode; a first functional layer disposed on the light-emitting layer and made of a metal fluoride; a second functional layer disposed on the first functional layer and including a first organic material having at least one of an electron transport property and an electron injection property; A counter electrode disposed above the second functional layer; a third functional layer disposed on the second functional layer and below the counter electrode; the second functional layer does not include one or more metal elements selected from alkali metals, alkaline earth metals, and rare earth elements that have a reducing property with respect to the metal fluoride; the third functional layer is formed by doping a second organic material having at least one of an electron transport property and an electron injection property with one or more metal elements selected from an alkali metal, an alkaline earth metal, and a rare earth metal, the metal fluoride being reducible; The thickness of the second functional layer is equal to or greater than the thickness of the first functional layer, and is equal to or greater than 1 nm and equal to or less than 5 nm. Self-luminous element.

2. The metal fluorides are fluorides of alkali metals, alkaline earth metals, and rare earth elements. The self-luminous element according to claim 1 .

3. The metal fluoride is sodium fluoride. The self-luminous element according to claim 1 .

4. The metal element is one or more metal elements selected from barium, lithium, cesium, and ytterbium. The self-luminous element according to any one of claims 1 to 3.

5. The thickness of the first functional layer is 1 nm or more and 5 nm or less, and the thickness of the second functional layer is 1 nm or more and 5 nm or less and is equal to or greater than the thickness of the first functional layer. The self-luminous element according to any one of claims 1 to 4.

6. The metal element contained in the third functional layer is ytterbium. The self-luminous element according to any one of claims 1 to 5.

7. The metal element contained in the third functional layer is different from the metal element contained in the first functional layer. The self-luminous element according to any one of claims 1 to 6.

8. The pixel electrode is light reflective, and the counter electrode is semi-transparent. The self-luminous element according to any one of claims 1 to 7.

9. a fourth functional layer including an organic material having at least one of a hole transport property and a hole injection property, the fourth functional layer being above the pixel electrode and below the light emitting layer; The self-luminous element according to any one of claims 1 to 8.

10. The thickness of at least one of the light emitting layer and the fourth functional layer varies depending on the wavelength of light emitted by the light emitting layer. The self-luminous element according to claim 9 .

11. At least one of the light-emitting layer and the fourth functional layer is a coating film. The self-luminous element according to claim 9 or 10.

12. A plurality of the self-luminous elements according to any one of claims 1 to 11 are arranged in a matrix above a substrate, and the light-emitting layers of the self-luminous elements adjacent in the row direction are partitioned by a bank extending in the column direction. Self-luminous display panel.

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