Method for manufacturing light-emitting element, and method for manufacturing display device

Abstract

Provided is a method for manufacturing a light-emitting element (20), the method including: a step for irradiating a hole transport layer (24) that has been exposed from a pattern of a resist layer (60) with ultraviolet ray; a step for, after the irradiation with the ultraviolet ray, applying a dispersion solution containing quantum dots onto the hole transport layer (24) to form a light-emitting layer (25); and a step for, after the formation of the light-emitting layer, removing the resist layer (60) with a peeling solvent. The hole transport layer (24) contains an organic compound.

Description

Method for manufacturing light-emitting element and method for manufacturing display device

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

[0002] For example, U.S. Patent No. 6,277,949 describes a method for forming a combined charge transporting and emissive layer (CCTEL) of a light-emitting device, the method including depositing a mixture containing quantum dots and a cross-linkable material in a solvent onto a base layer, and exposing at least a portion of the mixture to an activation stimulus to cross-link the cross-linkable material.

[0003] Japanese Patent Publication No. 2021-018986

[0004] In the method for manufacturing a light-emitting element described in Patent Document 1, a mixture containing quantum dots and a cross-linkable material is applied to a charge functional layer provided on a substrate, and the applied layer of the mixture is irradiated with ultraviolet light to cross-link the cross-linkable material, thereby forming a quantum dot-containing light-emitting layer (QD layer). This provides the light-emitting layer with peel resistance (solvent resistance).

[0005] Furthermore, in the method for manufacturing a light-emitting element described in Patent Document 1, the light-emitting layer is patterned by photolithography using a photoresist (photosensitive agent). Even in patterning the light-emitting layer by photolithography, the light-emitting layer is required to have peel resistance to, for example, a photoresist stripping solvent. For example, a manufacturing method that can increase the peel resistance of the patterned light-emitting layer to a solvent, regardless of the composition of the material for forming the light-emitting layer, like the manufacturing method described in Patent Document 1, is useful from the viewpoint of broadening the range of choices for materials for forming the light-emitting layer.

[0006] The invention of the present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide a novel method for manufacturing a light-emitting element that can improve the peel resistance of the light-emitting layer that is exposed to a solvent during the manufacturing process of the light-emitting element, and a method for manufacturing a display device that includes the light-emitting element.

[0007] A method for manufacturing a light-emitting element according to one aspect of the present disclosure is a method for manufacturing a light-emitting element having an anode and a cathode, and an emitting layer and at least one charge functional layer between the anode and the cathode, the method including the steps of forming the charge functional layer on the anode or the cathode, forming a resist layer pattern on the charge functional layer, irradiating ultraviolet light onto the charge functional layer exposed from the pattern, applying a dispersion liquid containing quantum dots onto the charge functional layer after the ultraviolet light irradiation to form the emitting layer, and removing the resist layer with a stripping solvent after forming the emitting layer, wherein the charge functional layer contains an organic compound.

[0008] Furthermore, a method for manufacturing a display device according to one aspect of the present disclosure is a method for manufacturing a display device having a plurality of light-emitting elements on a substrate, and includes a step of performing a method for manufacturing light-emitting elements according to one aspect of the present disclosure.

[0009] According to the method for manufacturing a light-emitting element according to one aspect of the present disclosure, it is possible to improve the peel resistance of the light-emitting layer that is exposed to a solvent during the manufacturing process of the light-emitting element.

[0010] FIG. 1 is a diagram illustrating the flow of each step included in a method for manufacturing a light-emitting element according to one embodiment (first embodiment) of the present disclosure. FIG. 2 is a diagram illustrating an outline of a step of forming an anode 21 on a substrate 10, included in a method for manufacturing a light-emitting element 20 according to one embodiment of the present disclosure. FIG. 3 is a diagram illustrating an outline of a step of forming a bank 22 on a substrate 10, included in a method for manufacturing a light-emitting element 20 according to one embodiment of the present disclosure. FIG. 4 is a diagram illustrating an outline of a step of forming a hole injection layer 23, included in a method for manufacturing a light-emitting element 20 according to one embodiment of the present disclosure. FIG. 5 is a diagram illustrating an outline of exposure of a resist layer 60 formed by applying a resist composition onto a hole transport layer. FIG. 6 is a diagram illustrating an outline of a step of washing the resist layer 60 with a developer and developing a pattern in the resist layer 60. FIG. 7 is a diagram illustrating an outline of a step of irradiating ultraviolet light onto the hole transport layer 24 exposed from the patterned resist layer 60, included in a method for manufacturing a light-emitting element 20 according to one embodiment of the present disclosure. FIG. 8 is a diagram illustrating an outline of a process of forming a light-emitting layer 25R on a hole transport layer 24 irradiated with ultraviolet light, which is included in the method for manufacturing a light-emitting element 20 according to an embodiment of the present disclosure. FIG. 9 is a diagram illustrating an outline of a process of removing a resist layer 60 with a stripping solvent after forming the light-emitting layer 25R, which is included in the method for manufacturing a light-emitting element 20 according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an outline of exposure of a resist layer 60 formed by applying a resist composition to the hole transport layer 24 on which the light-emitting layer 25R has been formed. FIG. 11 is a diagram illustrating an outline of a process of washing the resist layer 60 with a developer and developing a pattern in the resist layer 60. FIG. 12 is a diagram illustrating an outline of a process of irradiating ultraviolet light onto the hole transport layer 24 exposed from the patterned resist layer 60, which is included in the method for manufacturing a light-emitting element 20 according to an embodiment of the present disclosure. FIG. 13 is a diagram illustrating an outline of a process of forming a light-emitting layer 25B on a hole transport layer 24 irradiated with ultraviolet light, which is included in the method for manufacturing a light-emitting element 20 according to an embodiment of the present disclosure. Fig. 14 illustrates an outline of a process of removing the resist layer 60 with a stripping solvent after forming the light-emitting layer 25B, which is included in the method for manufacturing the light-emitting element 20 according to one embodiment of the present disclosure. Fig. 15 illustrates an outline of exposure of the resist layer 60 formed by applying a resist agent composition to the hole transport layer 24 on which the light-emitting layers 25R and 24B have been formed.FIG. 16 is a diagram illustrating an outline of a process of washing the resist layer 60 with a developer and developing a pattern in the resist layer 60. FIG. 17 is a diagram illustrating an outline of a process of irradiating ultraviolet light onto the hole transport layer 24 exposed from the patterned resist layer 60, which is included in the method for manufacturing the light-emitting element 20 according to one embodiment of the present disclosure. FIG. 18 is a diagram illustrating an outline of a process of forming a light-emitting layer 25G on the hole transport layer 24 irradiated with ultraviolet light, which is included in the method for manufacturing the light-emitting element 20 according to one embodiment of the present disclosure. FIG. 19 is a diagram illustrating an outline of a process of removing the resist layer 60 with a stripping solvent after forming the light-emitting layer 25G, which is included in the method for manufacturing the light-emitting element 20 according to one embodiment of the present disclosure. FIG. 20 is a diagram illustrating an outline of light-emitting elements 20R, 20B2, and 20G obtained by forming the electron transport layer 26 and the cathode 27. FIG. 21 is a diagram illustrating an outline of a cross section of a display device 100 including a plurality of light-emitting elements 20R, 20B, and 20G. FIG. 22 is a diagram illustrating an outline of the display device 100 as viewed from above. Fig. 23 is a diagram illustrating an outline of a top view of light-emitting elements 20R, 20B, and 20G in the display region of display device 100. Fig. 24 is a diagram illustrating a flow of each step included in a method for manufacturing a light-emitting element according to one embodiment (second embodiment) of the present disclosure. Fig. 25 is a diagram illustrating an outline of a step of irradiating ultraviolet light onto electron transport layer 26 exposed from patterned resist layer 60, included in a method for manufacturing a light-emitting element according to one embodiment of the present disclosure. Fig. 26 is a diagram illustrating an outline of a step of forming light-emitting layer 25R on electron transport layer 26 irradiated with ultraviolet light, included in a method for manufacturing a light-emitting element according to one embodiment of the present disclosure.

[0011] <Method for manufacturing light-emitting element and method for manufacturing display device (first embodiment)> A method for manufacturing a light-emitting element according to one embodiment of the present disclosure includes the steps of forming an anode or a cathode on a substrate, forming a charge functional layer on the anode or the cathode, forming a resist layer pattern on the charge functional layer, irradiating ultraviolet rays onto the charge functional layer exposed from the pattern, applying a dispersion liquid containing quantum dots onto the charge functional layer after the ultraviolet irradiation to form the light-emitting layer, and removing the resist layer with a stripping solvent after the light-emitting layer is formed, wherein the charge functional layer contains an organic compound.

[0012] In the step of forming a pattern of a resist layer on the charge functional layer, the resist layer formed on the charge functional layer is exposed and developed to pattern the resist layer into a desired pattern, and then the charge functional layer exposed from the pattern is irradiated with ultraviolet light. This improves the adhesion of an emissive layer formed on the charge functional layer in a subsequent step to the charge functional layer, and improves the peel resistance of the emissive layer formed on the charge functional layer against a solvent. A method for manufacturing a light-emitting element according to one embodiment improves the peel resistance of the emissive layer formed on the charge functional layer against a solvent in the process of manufacturing a light-emitting element having at least one charge functional layer and an emissive layer between an anode and a cathode.

[0013] Examples of the charge functional layer include a hole injection layer, a hole transport layer, and an electron transport layer. Light-emitting elements can be classified into light-emitting elements having a forward stack structure or an inverted stack structure depending on the stack structure of the charge functional layer between the anode and the cathode. In a light-emitting element having a forward stack structure, a hole injection layer, a hole transport layer, an emitting layer, and an electron transport layer are stacked in this order from the anode side provided on the substrate, and a cathode can be provided on the electron transport layer. In a light-emitting element having an inverted stack structure, an electron transport layer, an emitting layer, a hole transport layer, and a hole injection layer are stacked in this order from the cathode side provided on the substrate, and an anode can be provided on the hole injection layer.

[0014] In the method for manufacturing a light-emitting element according to one embodiment, the anode and cathode are formed from a transparent electrode material or a reflective electrode material, so that, for example, a top-emission type light-emitting element and a bottom-emission type light-emitting element can be manufactured.

[0015] 1 to 21 illustrate a method for manufacturing a top-emission light-emitting device having a forward stack structure, and explain a method for manufacturing a light-emitting device according to one embodiment. Fig. 1 is a diagram showing the flow of each step included in the method for manufacturing a light-emitting device according to one embodiment. Figs. 2 to 21 are diagrams for explaining an outline of each step in the method for manufacturing a light-emitting device according to one embodiment, and Fig. 21 shows an outline of a cross section of a display device 100 including light-emitting elements 20R, 20B, and 20G.

[0016] 1 , a method for manufacturing a light-emitting device according to an embodiment of the present disclosure includes the steps of forming an anode on a substrate (Step 1), forming a hole transport layer as a charge functional layer (Step 4), forming a resist pattern on the hole transport layer (Step 5), irradiating the hole transport layer exposed from the pattern with ultraviolet light (Step 6), applying a quantum dot dispersion liquid to the hole transport layer after the ultraviolet irradiation to form a light-emitting layer (Step 7), and removing the resist layer with a stripping solvent after the light-emitting layer is formed (Step 8). After the step of forming the anode on the substrate (Step 1) and before the step of forming the hole transport layer (Step 4), the method for manufacturing a light-emitting device according to an embodiment of the present disclosure includes the steps of forming an electron transport layer on the light-emitting layer (Step 9) and forming a cathode on the electron transport layer (Step 10). The method for manufacturing a light-emitting element according to an aspect of the present disclosure may also include a step of forming a sealing layer that seals the light-emitting elements 20R, 20B, and 20G (step 11).

[0017] As shown in FIG. 1 , in a method for manufacturing a light-emitting element according to one embodiment of the present disclosure, between step 1 of forming an anode on a substrate and step 3 of forming a hole transport layer, which is a charge functional layer, on the anode, a process from forming a resist layer pattern on the hole transport layer (step 5) to a process of removing the resist layer with a stripping solvent after forming the light-emitting layer (step 8) may be repeated to form a plurality of types of light-emitting elements that emit light of different wavelengths.

[0018] [1] Step of Forming Anode on Substrate As shown in FIG. 2, a method of manufacturing a light-emitting element 20 according to one embodiment includes a step of forming an anode 21 on a substrate 10 (step 1).

[0019] 2 includes an anode 21R for the light-emitting element 20R, an anode 21B for the light-emitting element 20B, and an anode 21G for the light-emitting element 20G. The anodes 21 are provided on the substrate 10 in an island shape for each sub-pixel, and are also referred to as "pixel electrodes."

[0020] The anode 21 includes a conductive material and may be a transparent electrode or a reflective electrode, and in the manufacturing method according to this embodiment, it may be a reflective electrode. The reflective electrode may be formed from a light-reflective conductive material, or may be formed from a laminate of a light-transmitting conductive material and a light-reflective conductive material.

[0021] The anode 21 contains a conductive material and may be a reflective electrode in the manufacturing method according to this embodiment. The reflective electrode may be formed from a light-reflective conductive material, or may be formed from a laminate of a light-transmitting conductive material and a light-reflective conductive material.

[0022] The electrode material that reflects visible light is not particularly limited as long as it can reflect visible light and has conductivity, and examples thereof include metal materials such as Al, Mg, Li, and Ag, alloys of the metal materials, laminates of the metal materials and transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), and laminates of the alloys and the transparent metal oxides. The transparent metal oxides that transmit visible light include electrode materials that are not particularly limited as long as they can transmit visible light and have conductivity, and examples thereof include thin films made of transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), or thin films made of metal materials such as Al and Ag, or nanowires made of metal materials such as Al and Ag.

[0023] Examples of light-transmitting conductive materials include indium tin oxide (ITO), indium zinc oxide (IZO), and tin oxide (SnO ２ ), fluorine-doped tin oxide (FTO), etc. These materials have high transmittance for visible light, which improves the luminous efficiency of the light-emitting device.

[0024] The anode 21 can be formed by a general electrode formation method, such as a physical vapor deposition (PVD) method such as vacuum deposition, sputtering, EB deposition, or ion plating, or a chemical vapor deposition (CVD) method. The method for patterning the anode 21 is not particularly limited as long as it can be formed into a desired pattern with high precision, and specific examples include photolithography and inkjet printing.

[0025] A substrate 11 is provided with a barrier layer 12 and a thin-film transistor layer 13 including a transistor TR, in this order from the substrate 11 side, and is provided with a plurality of anodes 21 (i.e., anodes 21R, 21G, and 21B), and this substrate is referred to as a substrate (active matrix substrate) 10 with anodes 21.

[0026] The substrate 11 is a support substrate and may be a non-flexible substrate made of quartz or glass, or a flexible substrate made of a resin film or sheet. The flexible substrate may be a resin substrate made of a resin material such as methacrylic resins typified by polyethylene methacrylate (PMMA), polyester resins typified by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN), polycarbonate resins, or polyimides. In this embodiment, to make the display device 100 a flexible display device, a case where a resin substrate made of a resin material such as polyimide is used as the substrate 11 will be described as an example, but the present invention is not limited to this.

[0027] The barrier layer 12 is a layer that prevents foreign substances such as water and oxygen from penetrating into the transistor TR, the light-emitting element 20R, the light-emitting element 20B, and the light-emitting element 20G described later, and can be composed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film of these, formed by the CVD method.

[0028] The transistor TR portion of the thin film transistor layer 13 including the transistor TR includes a semiconductor film SEM and doped semiconductor films SEM′ and SEM″, an inorganic insulating film 131, a gate electrode G, an inorganic insulating film 132, an inorganic insulating film 133, a source electrode S and a drain electrode D, and a planarization film 134, and the portion of the thin film transistor layer 13 including the transistor TR other than the transistor TR portion includes the inorganic insulating film 131, the inorganic insulating film 132, the inorganic insulating film 133, and the planarization film 134.

[0029] The semiconductor film SEM and the doped SEM' and SEM'' may be made of, for example, low-temperature polysilicon (LTPS) or an oxide semiconductor (for example, an In-Ga-Zn-O based semiconductor). In this embodiment, the case where the transistor TR has a top-gate structure will be described as an example, but the present invention is not limited to this, and the transistor TR may also have a bottom-gate structure.

[0030] The gate electrode G and the source electrode S and drain electrode D can be formed of a single layer or a multilayer film of a metal containing at least one of aluminum, tungsten, molybdenum, tantalum, chromium, titanium, and copper, for example.

[0031] The inorganic insulating films 131, 132, and 133 can be formed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film of these films, which are formed by a CVD method.

[0032] The planarization film 134 can be made of a coatable organic material such as polyimide or acrylic.

[0033] [2] Step of Forming Banks As shown in FIG. 3, the method of manufacturing the light-emitting element 20 according to one embodiment includes a step of forming banks 22 on the substrate 10 (step 2).

[0034] As shown in FIG. 3 , a bank (partition wall) 22 surrounds the anodes 21R, 21G, and 21B. The bank 22 need only separate the anodes 21R, 21G, and 21B provided on the substrate 10 in a top view and insulate them from one another. The bank 22 may be formed so that at least a portion thereof overlaps the vicinity of the end faces of the anodes 21R, 21G, and 21B. The bank 22 is preferably formed so as to cover the vicinity of the end faces of the anodes (so-called "edges"). This electrically insulates the light-emitting elements 20R, 20G, and 20B. For this reason, the bank 22 is also referred to as an "edge cover."

[0035] The bank 22 is an insulator formed from an insulating material, and may include, for example, a resin material such as polyimide resins, acrylic resins, novolac resins, or fluorene resins. The bank 22 can be formed, for example, by using a photolithography technique to pattern a photosensitive resin composition containing a photosensitizer such as a photoradical generator or a photoacid generator and a resin material. The photosensitive resin composition may be a negative-type photosensitive resin composition or a positive-type photosensitive resin composition.

[0036] 3, the bank 22 defines the outer periphery of the anodes 21R, 21B, and 21G, that is, the upper surfaces of the anodes 21. In the top view shown in FIG. 3, the bank 22 surrounds the upper surface of the anode 21 with its upper surface.

[0037] The width W of the upper surface of the anodes 21R, 21B, and 21G surrounded by the bank 22 is Ａ１ Although not limited to, the width W of the anodes 21R, 21B, and 21G surrounded by the bank 22 is, for example, in the range of 5 μm to 100 μm, and preferably in the range of 5 μm to 50 μm. Ａ２ Although not limited to, the width W is, for example, in the range of 50 μm to 500 μm, and preferably in the range of 50 μm to 200 μm. The height h of the bank 22 in a plan view is preferably in the range of 0.1 μm to 2.0 μm. Ａ１ is in the range of 5 μm to 100 μm, and the long width WＡ２ The upper surface of the anode, which has a thickness in the range of 50 μm to 500 μm, may be surrounded by a bank 22 having a height h in the range of 0.1 μm to 2.0 μm.

[0038] In addition, the width W of the bank 22 Ｂ１ and width W Ｂ２ are not limited to, but may each independently be, for example, in the range of 10 μm to 100 μm, and preferably in the range of 10 μm to 50 μm.

[0039] The anode 21 is formed in a thickness of 1×10 per unit area in the display region of the substrate 10. ３ ~1 x 10 ５ pieces / cm ２ It can be formed to a density of about 1000 .mu.m.

[0040] In the top view of FIG. 3 , the bank 22 surrounds the anode 21 with a rectangular opening, but the shape of the opening in top view is not limited to this and may be circular or elliptical. The anode may be surrounded by an elliptical opening having two straight sides along the long width direction and a curve in the short width direction.

[0041] [3] Step of Forming Hole Injection Layer The manufacturing method of the light-emitting element 20 according to one embodiment of the present disclosure may include a step of forming the hole injection layer 23 (Step 3). The hole injection layer 23 shown in Fig. 4 is a charge functional layer that contains a material having hole transport properties and has the function of injecting holes from the anode 21 to the hole transport layer 24 or the light-emitting layer 25 described later, and is one embodiment of a hole transport layer. The hole injection layer 23 preferably has the function of inhibiting the transport of electrons from the hole transport layer 24 described later or the light-emitting layer 25 described later to the anode 21.

[0042] The hole injection layer 23 contains inorganic nanoparticles as a material having hole transport capability. Examples of inorganic nanoparticles having hole transport capability include those containing one or more selected from the group consisting of oxides, nitrides, and carbides containing one or more of Zn, Cr, Ni, Ti, Nb, Al, Si, Mg, Ta, Hf, Zr, Y, La, Sr, and W. Among these, oxides containing one or more of Zn, Cr, Ni, Ti, Nb, Al, Si, Mg, Ta, Hf, Zr, Y, La, and Sr are preferred, such as NiO, MgO, MgNiO, and LaNiO. ３ , CuO and Cu ２ It is more preferable that the hole transport material is at least one selected from O. Furthermore, suitable hole transport materials include materials in which a CN group, an SCN group, and an SeCN group are bonded to a metal, such as CuSCN.

[0043] The median diameter of the inorganic nanoparticles contained in the hole injection layer 23 is 0.5 to 100 nm, preferably 1 to 40 nm, and more preferably 1 to 10 nm. Having the median diameter within this range prevents the hole injection layer 23 from becoming uneven, thereby preventing the generation of reactive current that does not contribute to light emission between the light-emitting layer and the hole transport layer (organic layer). The median diameter may be measured as a volume-based particle size distribution using, for example, a particle size distribution analyzer (Nanotrac wave II, manufactured by Microtrac-Bell).

[0044] The hole injection layer 23 may be formed, for example, by applying a dispersion containing inorganic nanoparticles having hole transport properties onto the anode 21 and the bank 22 of the substrate 10 by a known coating method such as spin coating, inkjet printing, or aerosol jet printing, and then drying by heating and / or vacuum drying. The dispersion of inorganic nanoparticles having hole transport properties may contain, for example, an organic amine compound or an organic thiol compound.

[0045] [4] Step of Forming Hole Transport Layer The manufacturing method of a light-emitting element according to one embodiment of the present disclosure includes a step of forming a hole transport layer 24 (Step 4). The hole transport layer 24 shown in Fig. 4 contains a material having hole transport properties and functions to inject holes from the anode 21 and the hole injection layer 23 to the light-emitting layer 25 described below. Note that the hole transport layer 24 preferably has a function of inhibiting the transport of electrons from the light-emitting layer 25 described below to the hole injection layer 23 and the anode 21.

[0046] The hole transport layer 24 contains an organic compound as a material having hole transport properties. Examples of organic compounds having hole transport properties include poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl))diphenylamine)] (abbreviated as "TFB"), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (abbreviated as "p-TPD"), and poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(N,N'-bis{4-butylphenyl}-benzine-N,N'-{1,4-diphenylene})] (abbreviated as "DTFB"). Other examples include polyvinylcarbazole (abbreviated as "PVK"). These hole transport materials may be used alone or in combination of two or more. In addition, a hole injection layer (not shown) may be formed. Examples include a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (abbreviated as "PEDOT:PSS"), NiO (nickel oxide), CuSCN (copper thiocyanate), etc. Note that these materials may be used alone or in combination of two or more types.

[0047] The organic compound having hole transport ability contained in the hole transport layer 24 is highly hydrophobic, and therefore the hole transport layer 24 has the problem of having high water and oil repellency due to the organic compound having hole transport ability.

[0048] The hole transport layer 24 may be formed on the hole injection layer 23 by a known coating method such as vacuum deposition, spin coating, ink jetting, or aerosol jetting, using an organic compound having hole transport capability. For example, when forming the hole transport layer 24 by spin coating, ink jetting, or aerosol jetting, a solution may be prepared by dissolving an organic compound having hole transport capability in an organic solvent, and the solution may be applied to the hole injection layer 23, followed by heating and / or vacuum drying.

[0049] The thickness of the hole transport layer 24 on the upper surfaces of the anode 21 and the hole injection layer 23 is preferably 10 nm or more at the thinnest portion and 100 nm or less at the thickest portion, thereby improving the hole transport properties of the hole injection layer 23 while suppressing an increase in the driving voltage of the light-emitting element.

[0050] [5] Step of forming a pattern of a resist layer on the hole transport layer The method for manufacturing a light-emitting element according to one aspect of the present disclosure includes a step of forming a pattern of a resist layer 60 on the hole transport layer 24 (step 5).

[0051] The resist composition for forming the resist layer 60 may be a positive resist composition or a negative resist composition, but is preferably a positive resist composition from the viewpoint that the resist layer 60 can be patterned in the air atmosphere.

[0052] The process of forming a pattern of the resist layer 60 on the hole transport layer 24 includes a step of applying a resist agent composition for forming the resist layer 60 onto the hole transport layer 24 containing an organic compound having hole transport ability, and a step of exposing the resist layer 60 formed by applying the resist agent composition onto the hole transport layer 24 as shown in Fig. 5. After the step of applying the resist agent composition and before the step of exposing the resist layer 60, it is preferable to remove the solvent contained in the resist layer 60 by heating and / or vacuum drying the resist layer 60 (pre-baking).

[0053] The light used in the step of exposing the resist layer 60 may be selected depending on the type of photosensitizer contained in the resist layer 60. Examples of light for exposing the resist layer 60 include ultraviolet light with a wavelength of about 150 to 450 nm, electron beams, etc. The ultraviolet light may be g-line (wavelength 436 nm), h-line (wavelength 405 nm), or i-line (wavelength 365 nm) from a high-pressure mercury lamp, or may be an excimer laser (wavelength 150 to 248 nm). When exposing the resist layer 60, the integrated exposure amount is not limited by designing the wavelength and exposure amount, but may be, for example, 1 mJ / cm. ２ ~1000mJ / cm ２ It is sufficient if it is within the range.

[0054] In the step of exposing the resist layer 60, a photomask 300 having a desired pattern may be used to expose the resist layer 60 formed on the hole transport layer 24.

[0055] FIG. 6 is a diagram illustrating an outline of the process of washing the resist layer 60 with a developer and developing a pattern in the resist layer 60. The resist layer 60 has increased solubility in an alkaline aqueous developer at exposed locations. Therefore, a desired pattern can be developed in the resist layer 60 by washing with the alkaline aqueous developer. The desired pattern can be developed by immersing the resist layer 60 in, for example, a beaker (not shown) containing the developer. The developer can be supplied to the resist layer 60 by spraying the developer using a spray nozzle, for example. After development with the alkaline aqueous developer, the substrate can also be washed with, for example, pure water.

[0056] The resist layer 60 may be formed on the hole transport layer 24 by applying a positive resist composition by a known application method such as a spin coating method, an inkjet method, or an aerosol jet method. Alternatively, the resist layer 60 may be formed by heating and / or vacuum drying the resist composition applied on the hole injection layer 23 (pre-baking).

[0057] The positive resist composition contains a positive photosensitizer and may contain a resin material. Examples of the positive photosensitizer include diazoquinone compounds, such as diazobenzoquinone (DBQ) and diazonaphthoquinone (DNQ), and derivatives thereof. Examples of diazoquinone derivatives include azoquinone sulfonate esters and azoquinone sulfonamides.

[0058] Examples of diazoquinone sulfonate esters include diazobenzoquinone compounds such as 1,2-benzoquinone diazo-4-sulfonate ester and 1,2-benzoquinone diazo-5-sulfonate ester, and diazonaphthoquinone compounds such as 1,2-naphthoquinone diazo-5-sulfonate ester and 1,2-naphthoquinone diazo-4-sulfonate ester. The diazoquinone sulfonic acid derivatives may be diazo-coupled.

[0059] The diazoquinone compound may have a structure having a phenolic hydroxyl group. The structure having a phenolic hydroxyl group may be a phenol structure having a monovalent hydroxyl group, such as phenol or naphthol; a phenol structure having a divalent or higher hydroxyl group, such as catechol or pyrogallol; a phenol structure having a divalent or higher phenolic hydroxyl group, such as bisphenol, trisphenol or tetrakisphenol; or a phenol resin structure, such as a novolac phenolic resin. Examples of compounds having a phenolic hydroxyl group include 4,4',4"-ethylidynetrisphenol, 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, α,α-bis(4-hydroxyphenyl)-4-(4-hydroxy-α,α-dimethylbenzyl)-ethylbenzene, 4,4'-(1-{4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene)diphenol, and novolac cresol resin.

[0060] In addition, the positive resist composition may contain, for example, resin materials such as polyolefin sulfone and polyphthalaldehyde, novolac type phenolic resin, and the like.

[0061] In addition, the resist composition for forming the resist layer may contain, as additives, for example, a photosensitizer such as acetophenone, a chemical sensitizer, a filler, a colorant, a stabilizer such as an antioxidant, and a surfactant such as a leveling agent, an antifoaming agent, or a dispersant.

[0062] Examples of the surfactant include fluorine-based solvents such as hydrofluoroethers and hydrofluoroolefins, and fluorine-based surfactants having a hydrophobic group, such as a hydrofluoroether chain or a hydrofluoroolefin chain, and a hydrophilic group.

[0063] [6] Step of Irradiating the Hole Transport Layer with Ultraviolet Rays As shown in FIG. 7 , a method for manufacturing a light-emitting element 20 according to one embodiment of the present disclosure includes a step of irradiating the hole transport layer 24 exposed from the patterned resist layer 60 with ultraviolet rays (Step 6). By irradiating the hole transport layer 24 exposed from the resist layer 60 with ultraviolet rays, the surface free energy of the hole transport layer 24 at the location irradiated with the ultraviolet rays can be increased. This reduces the water and oil repellency due to the organic compound contained in the hole transport layer 24. This increases the wettability of the dispersion liquid for forming the light-emitting layer applied to the surface of the hole transport layer 24, thereby improving the adhesion of the light-emitting layer to the surface of the hole transport layer 24. The reduction in water and oil repellency of the hole transport layer 24 is due to the increase in moisture (H O ... ２ This is expected to be brought about by the removal of oxygen radicals and the surface modification of the hole transport layer 24 due to the generation of oxygen radicals. Therefore, although not limited to this, it is preferable to irradiate the hole transport layer 24 with ultraviolet light in an air atmosphere.

[0064] The water contact angle, which is an index of the water and oil repellency of the hole transport layer 24, is preferably lower than 80°, and more preferably 60° or less.

[0065] The ultraviolet light irradiated onto the hole transport layer 24 exposed from the pattern of the resist layer 60 may be, for example, ultraviolet light having a wavelength of about 150 to 450 nm. The ultraviolet light may be g-line (wavelength 436 nm), h-line (wavelength 405 nm), or i-line (wavelength 365 nm) emitted by a high-pressure mercury lamp, or may be an excimer laser (wavelength 150 to 248 nm).

[0066] The cumulative dose of ultraviolet light irradiated onto the hole transport layer 24 is 200 to 1000 mJ / cm ２ It is preferable that the cumulative dose of ultraviolet light irradiated onto the hole transport layer 24 is within the range of 200 mJ / cm ２ This makes it possible to prevent the light-emitting layer from peeling off from the hole transport layer 24, and ２ By setting the temperature to the value below, it is possible to prevent the bank 22 and the substrate 10 from being damaged by ultraviolet rays.

[0067] The hole transport layer 24 is preferably irradiated with ultraviolet light using a photomask that can form the same pattern as the photomask 300 that was used to form the pattern on the resist layer 60. This allows the hole transport layer 24 exposed from the surface of the resist layer 60 to be successfully irradiated with ultraviolet light.

[0068] [8] Step of forming the light-emitting layer As shown in FIG. 8, a method for manufacturing the light-emitting element 20 according to one embodiment of the present disclosure includes a step of forming the light-emitting layer 25R on the hole transport layer 24 irradiated with ultraviolet light (step 7).

[0069] The light-emitting layer 25 includes a light-emitting layer 25R that emits red light, a light-emitting layer 25G that emits green light, and a light-emitting layer 25B that emits blue light. In the present disclosure, "blue light" refers to light having a central emission wavelength in a wavelength band of, for example, 400 nm or more and 500 nm or less. "Green light" refers to light having a central emission wavelength in a wavelength band of, for example, more than 500 nm and less than 600 nm. "Red light" refers to light having a central emission wavelength in a wavelength band of, for example, more than 600 nm and less than 780 nm.

[0070] The light-emitting layer 25 is a layer that emits light when a light emitter is excited by recombination of holes from the anode 21 and electrons from the cathode 27, and the excited light emitter returns to its ground state. When a voltage or current is applied between the anode 21 and the cathode 27, recombination occurs in the light-emitting layer 25, causing light to be emitted. The light-emitting layer 25 contains quantum dots as light emitters.

[0071] The light-emitting layer 25 is a layer formed by applying a dispersion liquid containing quantum dots onto the hole transport layer 24. The dispersion liquid containing quantum dots may contain an amine compound or a thiol compound as a dispersant, or may contain a dispersion medium. The dispersion liquid containing quantum dots may also contain a constituent material of the matrix material.

[0072] The dispersion liquid containing quantum dots may contain, for example, a hydrocarbon-based solvent as a dispersion medium. Examples of hydrocarbon-based solvents include aliphatic hydrocarbons such as hexane, cyclohexane, octane, and decane, and aromatic hydrocarbons such as toluene and xylene.

[0073] The light-emitting layer 25 may be formed by applying a dispersion liquid containing quantum dots onto the resist layer 60 and onto the hole transport layer 24 exposed from the pattern of the resist layer 60 by a known coating method such as spin coating, inkjet coating, slit coating, or aerosol jet coating. In the step of forming the light-emitting layer 25, the light-emitting layer 25 applied onto the hole transport layer 24 may be dried by heating and / or vacuum drying.

[0074] In one embodiment of the method for manufacturing a light-emitting element, the wettability of the hole transport layer 24 is increased by the ultraviolet irradiation process, so that the hole transport layer 24 can be coated in such a way that no areas are left unwetted by droplets of the dispersion liquid containing quantum dots.

[0075] In the present disclosure, the "quantum dots" contained in the light-emitting layer 25 refer to dots having a maximum width of 100 nm or less. The shape of the quantum dots is not particularly limited as long as it satisfies the above-mentioned maximum width, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). The shape of the quantum dots may be, for example, a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with an uneven surface, or a combination thereof.

[0076] The quantum dots are typically made of a semiconductor. The semiconductor may have a certain band gap. The semiconductor may be any material capable of emitting light and may include at least the materials described below. The semiconductor may be capable of emitting red, green, and blue light, respectively. The semiconductor may include, for example, at least one selected from the group consisting of a II-VI compound, a III-V compound, a chalcogenide, and a perovskite compound. Note that a II-VI compound refers to a compound containing a II element and a VI element, and a III-V compound refers to a compound containing a III element and a V element. Furthermore, a II element may include a group 2 element and a group 12 element, a group III element may include a group 3 element and a group 13 element, a group V element may include a group 5 element and a group 15 element, and a group VI element may include a group 6 element and a group 16 element.

[0077] The II-VI compound includes, for example, at least one selected from the group consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe.

[0078] The III-V compound includes, for example, at least one selected from the group consisting of GaAs, GaP, InN, InAs, InP, and InSb.

[0079] Chalcogenides are compounds containing a Group VI A(16) element, such as CdS or CdSe. Chalcogenides may also include mixed crystals thereof.

[0080] The perovskite compound has a composition represented by the general formula CsPbX3, for example. The constituent element X includes at least one element selected from the group consisting of Cl, Br, and I.

[0081] Here, the numbering of element groups using Roman numerals is based on the old IUPAC (International Union of Pure and Applied Chemistry) system or the old CAS (Chemical Abstracts Service) system, and the numbering of element groups using Arabic numerals is based on the current IUPAC system.

[0082] The light-emitting layer 25 may contain a matrix material. The matrix material refers to a material that contains and holds other substances, and can be referred to as a base material, a parent material, or a filler. The matrix material may be solid at room temperature. The matrix material may be a material that contains and holds multiple quantum dots. The matrix material may be a component of the light-emitting layer 25 that contains multiple quantum dots. The light-emitting layer 25 has a quantum dot group that contains multiple quantum dots, and the matrix material may fill regions (spaces) other than the quantum dot group. Here, three or more quantum dots are collectively referred to as a quantum dot group. The matrix material may fill regions (spaces) in the light-emitting layer 25 other than the multiple quantum dots.

[0083] The matrix material may be the same material as the shell contained in each of the multiple quantum dots. In this case, the average distance between adjacent cores (core-to-core distance) may be 3 nm or more, or may be 5 nm or more. Alternatively, the average distance between adjacent cores may be 0.5 times or more the average core diameter. The core-to-core distance is the average of the shortest distances between 20 adjacent cores. The core-to-core distance should be kept wider than the distance when the shells are in contact with each other. The average core diameter is the average of the core diameters of 20 adjacent cores observed in cross-section. The core diameter can be the diameter of a circle having the same area as the core area in cross-section observation.

[0084] The concentration of the matrix material in the light-emitting layer 25 is, for example, the area ratio occupied by the matrix material in the cross section of the light-emitting layer 25. This concentration may be 10% to 90% or 30% to 70% in cross-sectional observation. This concentration may be measured, for example, from the area ratio in image processing of cross-sectional observation. When the quantum dots have a core-shell structure, the shell concentration may be 1% to 50%. When the shell and the matrix material are made of the same material (same composition) and cannot be distinguished from each other, the concentration of the combined region of the shell and the matrix material may be within the range obtained by adding the range of the matrix material concentration to the range of the shell concentration. The ratio of the core, shell, and matrix material of the quantum dot may be adjusted appropriately so that the total is 100% or less. In this way, when the shell and the matrix material cannot be distinguished from each other, the shell may be part of the matrix material.

[0085] The light-emitting layer 25 may be composed of a plurality of quantum dots and a matrix material. When the light-emitting layer 25 is analyzed, the intensity of carbon detected due to the chain structure may be equal to or less than noise.

[0086] The matrix material preferably has a wider band gap than the quantum dot material (for example, the core material). A semiconductor or an insulator can be used as the matrix material. Examples of the matrix material include metal sulfides and / or metal oxides. Metal sulfides include, for example, zinc sulfide (ZnS), zinc magnesium sulfide (ZnMgS, ZnMgS ２ ), gallium sulfide (GaS, Ga ２ S ３ ), zinc tellurium sulfide (ZnTeS), magnesium sulfide (MgS), zinc gallium sulfide (ZnGa ２ S ４ ), magnesium gallium sulfide (MgGa ２ S ４ The metal oxide may be zinc oxide (ZnO), titanium oxide (TiO ２ ), tin oxide (SnO ２ ), tungsten oxide (WO ３ ), zirconium oxide (ZrO２ ) The chemical formulas written in parentheses after the compound names are representative examples. The composition ratios written in the chemical formulas are preferably stoichiometric, so that the actual composition of the compounds is as shown in the chemical formulas, but they do not necessarily have to be stoichiometric.

[0087] [9] Process for patterning the light-emitting layer As shown in FIG. 9, a method for manufacturing a light-emitting element according to one embodiment of the present disclosure includes a process (step 8) for removing the resist layer 60 with a stripping solvent after forming the light-emitting layer 25R.

[0088] In the step of removing the resist layer 60 with a stripping solvent, the substrate on which the light-emitting layer 25R has been formed is washed with a stripping solvent, so that the light-emitting layer 25R formed on the resist layer 60 is stripped and removed together with the resist layer 60. This develops the pattern of the light-emitting layer 25R so that the light-emitting layer 25 remains on the hole transport layer 24. Here, the hole transport layer 24 has been irradiated with ultraviolet light, thereby increasing the peel resistance of the light-emitting layer 25. Therefore, in the step of patterning the light-emitting layer, it is possible to prevent the light-emitting layer 25R from being stripped from the hole transport layer 24 by the stripping solvent.

[0089] The stripping solvent is not limited as long as it can strip the resist layer 60, and examples thereof include propylene glycol monomethyl ether acetate (PEGMEA), propylene glycol monomethyl ether (PEGME), etc. Among these, propylene glycol monomethyl ether acetate (PEGMEA) is preferred as the stripping solvent from the viewpoint of safety during manufacturing, as it has a high flash point.

[0090] [Formation of Multiple Types of Light-Emitting Layers] In a method for manufacturing a light-emitting device according to one aspect of the present disclosure, it is preferable to repeatedly perform steps from forming a resist pattern on the hole transport layer in step 5 to patterning the light-emitting layer in step 8. In this manner, it is preferable to form multiple types of light-emitting layers 25 (25R, 25B, 25G) on substrate 10.

[0091] More specifically, similar to the step of forming a pattern of a resist layer on the hole transport layer (step 5), the following steps may be performed: applying a resist layer agent composition to the hole transport layer 24 on which the light-emitting layer 25R has been formed, and exposing the formed resist layer 60; and washing the exposed resist layer 60 with a developer to form a pattern in the resist layer 60, as shown in Fig. 11. By using a photomask 301, the hole transport layer 24 overlapping the anode 21B may be exposed from the pattern of the resist layer 60 so as not to substantially overlap with the light-emitting layer 25R, as shown in Fig. 11. The step of forming a pattern of the resist layer 60 shown in Figs. 10 and 11 can be performed under the same conditions as step 5 except for using the photomask 301, and therefore a description thereof will be omitted.

[0092] 12, ultraviolet light may be irradiated onto the hole transport layer 24 exposed from the pattern of the resist layer 60, similar to the step of irradiating ultraviolet light onto the hole transport layer (step 6). The ultraviolet light irradiation step can be performed under the same conditions as step 6 except that a photomask 301 is used, and therefore a description thereof will be omitted.

[0093] The light-emitting layer 25B may be formed in accordance with the process of forming the light-emitting layer (step 7) and the process of patterning the light-emitting layer (step 8) (FIGS. 13 and 14).

[0094] Similarly, similar to the step (step 5) of forming a resist layer pattern on the hole transport layer 24, a step of applying a resist layer agent composition to the hole transport layer 24 on which the light-emitting layers 25R and 25B have been formed, and a step of exposing the resist layer 60 through a photomask 302 as shown in FIG. 15 and washing the exposed resist layer 60 with a developer to form a pattern in the resist layer 60 as shown in FIG. 16 may be performed. By using the photomask 302, the hole transport layer 24 overlapping the anode 21G may be exposed from the pattern of the resist layer 60 so as not to substantially overlap with the light-emitting layers 25R and 25B, as shown in FIG. 16. The step of forming the resist layer 60 pattern shown in FIGS. 15 and 16 can be performed under the same conditions as step 5 except for using the photomask 302, and therefore a description thereof will be omitted.

[0095] 17, similar to the step of irradiating the hole transport layer with ultraviolet light (step 6), ultraviolet light may be irradiated onto the hole transport layer 24 exposed from the pattern of the resist layer 60. The step of irradiating ultraviolet light can be performed under the same conditions as step 6 except that a photomask 302 is used, and therefore a description thereof will be omitted.

[0096] The light-emitting layer 25G may be formed in accordance with the process of forming the light-emitting layer (step 7) and the process of patterning the light-emitting layer (step 8) (FIGS. 17 and 18).

[0097] As exemplified by the above light-emitting elements 25R, 25B, and 25G, after developing (patterning) the resist layer 60, ultraviolet light may be irradiated onto the hole transport layer 24 exposed from the pattern of the resist layer 60. This allows for improved adhesion of each light-emitting layer to the hole transport layer, even when multiple types of light-emitting layers are used.

[0098]

[10] Step of Forming Electron Transport Layer A method for manufacturing a light-emitting device according to one embodiment of the present disclosure includes a step of forming an electron transport layer 26, which is a charge functional layer (Step 9). The electron transport layer 26 shown in Fig. 20 contains a material having electron transport properties and functions to transport electrons from the cathode 27 to the light-emitting layer 25. Note that the electron transport layer 26 preferably has a function of inhibiting the transport of holes from the hole injection layer 23, the hole transport layer 24, and the light-emitting layer 25 to the cathode 27.

[0099] The electron transport layer 26 contains an organic compound as a material having electron transport properties. Examples of organic compounds having electron transport properties include compounds and complexes containing one or more nitrogen-containing heterocycles such as an oxadiazole ring, a triazole ring, a triazine ring, a quinoline ring, a phenanthroline ring, a pyrimidine ring, a pyridine ring, an imidazole ring, or a carbazole ring. Like organic compounds having hole transport properties, these organic compounds having electron transport properties (electron transport materials) can also increase their surface free energy by irradiating them with ultraviolet light, thereby improving the adhesion of the light-emitting layer 25. Specific examples include 1,10-phenanthroline derivatives such as bathocuproine and bathophenanthroline, benzimidazole derivatives such as 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI), metal complexes such as tris(8-quinolinolato)aluminum complex (Alq3), bis(10-benzoquinolinolato)beryllium complex, 8-hydroxyquinoline Al complex, and bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum, and 4,4′-biscarbazole biphenyl. Other examples include aromatic boron compounds, aromatic silane compounds, aromatic phosphine compounds such as phenyldi(1-pyrenyl)phosphine, bathophenanthroline, bathocuproine, 2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), and nitrogen-containing heterocyclic compounds such as triazine derivatives.

[0100] Additionally, examples of electron transport materials suitable for the electron transport layer 26 include compounds having a paraphenylene vinylene skeleton. Specific examples include polyparaphenylene vinylene (PPV) compounds such as poly(2-2'-ethyl-hexoxy)-5-methoxy-1,4-phenylene vinylene (POPh-PPV).

[0101] The electron transport layer 26 may be formed on the light-emitting layer 25 by applying an organic compound having electron transport capability by a known coating method such as a vacuum deposition method, a spin coating method, an inkjet method, or an aerosol jet method. For example, when forming the electron transport layer 26 by a spin coating method, an inkjet method, or an aerosol jet method, the electron transport layer 26 may be formed by preparing a solution in which an organic compound having electron transport capability is dissolved in an organic solvent, applying the solution to the light-emitting layer 25, and then drying by heating and / or vacuum drying.

[0102] The thickness of the electron transport layer 26 is preferably 10 nm or more at its thinnest portion and 100 nm or less at its thickest portion, which makes it possible to improve the electron transport properties of the electron transport layer 26 while suppressing an increase in the driving voltage of the light-emitting element.

[0103]

[10] Step of Forming Cathode A method for manufacturing a light-emitting device according to one embodiment of the present disclosure includes a step of forming a cathode 27 on the electron transport layer 26 (step 10). The cathode 27 shown in Fig. 20 includes a conductive material and may be a transparent electrode or a reflective electrode. In the manufacturing method according to this embodiment, the cathode 27 may be a transparent electrode. A transparent electrode can be formed from a light-transmitting conductive material.

[0104] The conductive materials that can be used in the step of forming the cathode and the method of forming the cathode are similar to the explanation of the step of forming the anode on the substrate, and therefore the explanation thereof will be omitted.

[0105] In this manner, the light emitting elements 20R, 20B, and 20G are formed on the substrate 10.

[0106]

[11] Step of Forming a Sealing Layer A manufacturing method for a light-emitting element according to one embodiment of the present disclosure may include a step of forming a sealing layer 30 on the cathode 27 (step 11). The sealing layer 30 covers the light-emitting elements 20R, 20B, and 20G and the bank 22, sealing the light-emitting elements. The sealing layer 30 reduces the penetration of foreign matter, including moisture, into the light-emitting layer, electron transport layer, etc. from the outside of the sealing layer side of the light-emitting element. The sealing layer 30 may have a laminated structure of, for example, an organic sealing film 31 made of an organic material and an inorganic sealing film 32 made of an inorganic material.

[0107] [Display device 100] Figure 21 is a diagram illustrating an outline of a cross section of a display device 100 equipped with a plurality of light-emitting elements 20R, 20B, and 20G, Figure 22 is a diagram illustrating an outline of the display device 100 as viewed from above, and Figure 23 is a diagram illustrating an outline of the light-emitting elements 20R, 20B, and 20G as viewed from above in the display area of ​​the display device 100.

[0108] 22 , display device 100 according to the present disclosure includes a display area DA that displays by extracting light from light-emitting elements 20 (described later), and a frame area NA that surrounds the periphery of display area DA. Although not shown, terminals are formed in frame area NA to which signals for driving light-emitting elements of display device 100 are input.

[0109] Fig. 23 corresponds to an enlarged top view of one pixel PIX shown in Fig. 22. As shown in Fig. 23, the light-emitting element includes light-emitting elements 20R, 20G, and 20B surrounded by a bank 22, and each of these light-emitting elements 20R, 20G, and 20B can constitute a sub-pixel within one pixel PIX shown in Fig. 22.

[0110] According to the method for manufacturing a light-emitting element according to one embodiment of the present disclosure, each of light-emitting elements 20R, 20G, and 20B has improved adhesion to hole transport layer 24, which is a charge transport layer. Therefore, a method for manufacturing a display device, which includes the method for manufacturing a light-emitting element according to one embodiment of the present disclosure, is also within the scope of the present disclosure.

[0111] <Method for manufacturing light-emitting element and method for manufacturing display device (second embodiment)> Fig. 24 is a diagram showing a flow illustrating an example of a method for manufacturing a light-emitting element according to one embodiment (second embodiment) of the present disclosure. The method for manufacturing a light-emitting element according to the first embodiment is a method for manufacturing a light-emitting element having a forward stack structure, while the method for manufacturing a light-emitting element according to the second embodiment is a method for manufacturing a light-emitting element having an inverted stack structure.

[0112] 24 , a method for manufacturing a light-emitting device according to an embodiment of the present disclosure includes the steps of forming a cathode on a substrate (Step 1′), forming an electron transport layer as a charge functional layer (Step 3′), forming a resist pattern on the electron transport layer (Step 4′), irradiating the electron transport layer exposed from the pattern with ultraviolet light (Step 5′), applying a quantum dot dispersion liquid to the electron transport layer after the ultraviolet irradiation to form a light-emitting layer (Step 6′), and removing the resist layer with a stripping solvent after the light-emitting layer is formed (Step 7′). The method may also include the steps of forming a bank (Step 2′) after the step of forming the cathode on the substrate (Step 1′) and before the step of forming the electron transport layer (Step 3). The method for manufacturing a light-emitting device according to an embodiment of the present disclosure includes the steps of forming a hole transport layer on the light-emitting layer (Step 8′), forming a hole injection layer (Step 9′), and forming an anode on the hole injection layer (Step 10′) after removing the resist layer with a stripping solvent. The method for manufacturing a light-emitting element according to an aspect of the present disclosure may also include a step of forming a sealing layer that seals the light-emitting element (step 11').

[0113] As shown in FIG. 24 , in a method for manufacturing a light-emitting element according to one embodiment of the present disclosure, multiple types of light-emitting elements emitting light of different wavelengths may be formed by repeating the steps from forming a pattern of a resist layer on an electron transport layer (step 4′) to forming a light-emitting layer and then removing the resist layer with a stripping solvent (step 7′).

[0114] The light-emitting element having an inverted stack structure manufactured by the above steps 1' to 11' may have an electron transport layer 26, a light-emitting layer 25, a hole transport layer 24, and a hole injection layer 23 laminated in this order from the cathode 27 side provided on the substrate 10, and an anode 21 may be provided on the hole injection layer 23 as a counter electrode.

[0115] The methods for forming the cathode 27 (27R, 27B, 27G), the electron transport layer 26, the light-emitting layer 25, the hole transport layer 24, the hole injection layer 23, and the anode 21, as well as the materials and details used in each step, are similar to the method for manufacturing the light-emitting element according to the first embodiment, and therefore will not be described here.

[0116] FIG. 25 is a diagram illustrating an outline of a process of irradiating ultraviolet light onto the electron transport layer 26 exposed from the patterned resist layer 60, which is included in a method for manufacturing a light-emitting device according to one embodiment of the present disclosure. As already described, the electron transport layer 26 contains an organic compound as a material with electron transport properties, similar to the hole transport material. According to this method for manufacturing a light-emitting device, after performing the process of forming an electron transport layer (step 3′) as a charge functional layer and the process of forming a resist layer pattern on the electron transport layer (step 4′), the process of irradiating ultraviolet light onto the electron transport layer 26 exposed from the pattern (step 5′) can be performed. This can increase the surface free energy of the electron transport layer 26 at the locations irradiated with ultraviolet light. This can reduce the water and oil repellency due to the organic compound contained in the electron transport layer 26. This can increase the wettability of the dispersion liquid for forming the light-emitting layer 25, which is applied to the surface of the electron transport layer 26, and can improve the adhesion of the light-emitting layer 25 to the surface of the electron transport layer 26 ( FIG. 26 ).

[0117] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. An embodiment obtained by appropriately combining the technical means disclosed in each of the different embodiments is also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0118] An embodiment of the present disclosure is described below.

[0119] In the examples and comparative examples, the hole transport layer was irradiated with ultraviolet light during the process of manufacturing the light emitting device, and the water contact angle of the hole transport layer and the peel resistance of the light emitting layer were evaluated.

[0120] [1] Evaluation of peeling resistance For the evaluation of peeling resistance, an anode, a bank, a hole injection layer, a hole transport layer, and a light emitting layer were formed in this order according to the manufacturing process of a light emitting device to prepare a test piece for evaluation of peeling resistance. The peeling resistance of the light emitting layer formed on the test piece was evaluated based on whether or not the light emitting layer peeled off from the hole transport layer during patterning. Light emitting layer: InP Hole transport layer: TFB Hole injection layer: NiO Bank: Acrylic resin Anode: Ag / ITO Substrate: Glass

[0121] [1-1] Formation of anode and bank An Ag / ITO anode and bank were patterned on the upper surface of a 25 mm x 25 mm glass substrate. The bank pattern had an opening that opened to the upper surface of the glass substrate, and was formed so that the anode was exposed at the bottom of the opening. The bank opening had a depth of 3 μm, an inner vertical width of about 100 μm, and a horizontal width of about 30 μm, and the density per unit area was 14,700 / cm. ２ An opening was formed.

[0122] [1-2] Formation of Hole Injection Layer First, a dispersion of the hole injection material was prepared using NiO as the hole injection material and pure water as the dispersion medium. Next, the dispersion was spin-coated onto the substrate on which the anode and bank had been formed, and then heated and dried at 200°C for 20 minutes to form a hole injection layer with a thickness of 50 nm.

[0123] [1-3] Formation of Hole Transport Layer First, a dispersion of hole transport material was prepared using TFB as the hole transport material and chlorobenzene as the dispersion medium. Next, the dispersion was spin-coated on the hole injection layer formed on the substrate, and heated and dried at 200°C for 30 minutes to form a hole transport layer with a thickness of 30 nm.

[0124] [1-4] Formation and patterning of resist layer A positive resist agent THB-801P (manufactured by JSR Corporation) was spin-coated on the hole transport layer formed on the glass substrate under light-shielding conditions, and then heated and dried (pre-baked) at 90°C for 1 minute. Then, using a photomask, the pre-baked positive resist layer was irradiated with 300 mJ / cm ２ The positive resist layer was then exposed to ultraviolet light with a wavelength range of 365 to 436 nm at an integrated dose of 1000 u / s. The positive resist layer was then treated with 2.38% tetramethylammonium hydroxide (TMAH) as an alkaline developer and pure water as a rinse, followed by heating and drying at 90°C for 1 minute (post-baking). This resulted in the formation of a pattern in the positive resist layer, with openings at least in the banks and the hole transport layer formed therein exposed.

[0125] [1-5] Ultraviolet irradiation Using the same photomask as that used for patterning the positive resist layer, 300 mJ / cm was applied to the hole transport layer exposed in the pattern of the positive resist layer after post-baking. ２ The sample was irradiated with ultraviolet light having a wavelength range of 365 to 436 nm at an integrated irradiation dose of 1000 .mu.m.

[0126] [1-6] Formation of the Light-Emitting Layer First, a dispersion containing quantum dots InP containing dodecanethiol as a ligand and octane as a dispersion medium was prepared. Next, the dispersion was applied to a post-baked and UV-irradiated substrate using a spin coater under a light-shielded condition, and then heated and dried at 80°C for 10 minutes.

[0127] [1-6] Evaluation of Peel Resistance (Lift-Off Patterning) (Example 1) The peel resistance of the light-emitting layer was evaluated according to the conditions for lift-off patterning of the light-emitting layer. The peel resistance evaluation was performed using propylene glycol monomethyl ether acetate (PEGMEA) as a stripping solution. First, a beaker was filled with PEGMEA, and the positive resist layer was stripped by immersing the beaker in the stripping solution for 30 seconds at a liquid temperature of about 25°C, and a pattern of the light-emitting layer was developed on the hole transport layer.

[0128] When the light-emitting layer pattern was developed, peel resistance was evaluated. The peel resistance was evaluated visually, and the evaluation criteria are as follows: +: No peeling was observed. -: Peeling was observed.

[0129] (Examples 2 to 4) A plurality of test pieces were prepared by carrying out the above-mentioned steps from [1-1] formation of the anode and bank to [1-6] formation of the light-emitting layer under the same conditions as in Example 1. The immersion time of these test pieces in the stripping solution was changed from 30 seconds to 60 seconds, 90 seconds, and 120 seconds, and the peeling resistance of the light-emitting layer was evaluated after each immersion time.

[0130] Comparative Example 1 A test piece for a comparative example was prepared under the same conditions as in Example 1, except that the above-mentioned (1-5) ultraviolet irradiation was not performed, and the peeling resistance of the light-emitting layer was evaluated.

[0131] Table 1 below shows the evaluation results of peel resistance in Examples 1 to 4 and the Comparative Example.

[0132] [2] Evaluation of Water Contact Angle As in Example 1, a test piece was prepared by carrying out the same steps as those described above, from [1-1] Formation of the anode and bank to [1-5] UV irradiation, and the water contact angle of the test piece was measured using a contact angle meter (device name: MCA-4, manufactured by Kyowa Interface Science Co., Ltd.) after dropping a 5 pL water droplet into the bank under conditions of a temperature of 25°C and a humidity of 40%. As a comparative example, a test piece was prepared under the same conditions as in Example 1, except that [1-5] UV irradiation was not carried out, and the water contact angle of the test piece was measured.

[0133]

[0134] [3] Fabrication of Light-Emitting Device As in Example 1, an electron transport layer and a cathode were formed on the light-emitting layer of a test piece that had been subjected to the same steps as those described above from [1-1] Formation of an anode and a bank to [1-6] Evaluation of peelability (lift-off patterning), to fabricate a light-emitting device.

[0135] The electron transporting material and cathode material used in the manufacture of the light-emitting device are as follows: Cathode: ITO Electron transport layer: ZnO

[0136] Following the above procedure, light-emitting elements were manufactured on a test scale on a 25 mm x 25 mm glass substrate. As shown in Table 1, the light-emitting elements of Examples 1 to 4 with a peel resistance rating of "+" were prevented from peeling off of the light-emitting layer. Therefore, it is clear that manufacturing a display device including light-emitting elements using the manufacturing methods of Examples 1 to 4 can prevent display unevenness (color unevenness) due to missing pixels caused by peeling off of the light-emitting layer, and complete light failure caused by peeling off of all the RGB light-emitting layers.

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

[0138] REFERENCE SIGNS LIST 10 Substrate 20, 20R, 20B, 20G Light-emitting element 21, 21R, 21B, 21G Anode 22 Bank 23 Hole injection layer (charge functional layer) 24 Hole transport layer (charge functional layer) 25, 25R, 25B, 25G Light-emitting layer 26 Electron transport layer 27, 27R, 27B, 27G Cathode 100 Display device

Claims

1. A method for manufacturing a light-emitting device having an anode and a cathode, and an emitting layer and at least one charge functional layer between the anode and the cathode, comprising: forming the charge functional layer on the anode or the cathode; forming a resist layer pattern on the charge functional layer; irradiating ultraviolet rays onto the charge functional layer exposed from the pattern; after the ultraviolet irradiation, applying a dispersion liquid containing quantum dots onto the charge functional layer to form the emitting layer; and after forming the emitting layer, removing the resist layer with a stripping solvent, wherein the charge functional layer contains an organic compound.

2. The irradiation amount of the ultraviolet light is 200 to 1000 mJ / cm ２ The method for manufacturing a light-emitting element according to claim 1 , wherein the thickness of the light-emitting element is within the range of 3. The method for producing a light-emitting element according to claim 1 or 2, wherein the ultraviolet light is irradiated in an air atmosphere.

4. The method for producing a light-emitting element according to any one of claims 1 to 3, wherein the resist layer is formed by applying a positive resist composition.

5. The method for producing a light-emitting element according to any one of claims 1 to 4, wherein the stripping solvent is selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether.

6. A method for manufacturing a light-emitting device according to any one of claims 1 to 5, comprising the step of forming the charge functional layer on the anode, wherein the charge functional layer is a hole transport layer.

7. The method for producing a light-emitting element according to claim 6, wherein the organic compound is a hole-transporting material selected from poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl))diphenylamine)], poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine], and poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(N,N'-bis{4-butylphenyl}-benzine-N,N'-{1,4-diphenylene})].

8. The method for producing a light-emitting device according to claim 6 or 7, further comprising the step of forming a hole injection layer between the anode and the hole transport layer.

9. A method for producing a light-emitting device according to any one of claims 6 to 8, further comprising the step of forming another charge transport layer on the anode and the light-emitting layer, the another charge transport layer being an electron transport layer.

10. A method for manufacturing a light-emitting device according to any one of claims 1 to 5, comprising the step of forming the charge functional layer on the cathode, wherein the charge functional layer is an electron transport layer.

11. The method for producing a light-emitting element according to claim 10, wherein the organic compound is at least one organic compound selected from the group consisting of 1,10-phenanthroline derivatives, benzimidazole derivatives, aromatic phosphine compounds, aromatic boron compounds, aromatic silane compounds, and triazine derivatives.

12. The method for manufacturing a light-emitting element according to claim 11, wherein the 1,10-phenanthroline derivative is at least one selected from the group consisting of bathocuproine and bathophenanthroline, the benzimidazole derivative is 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI), and the aromatic phosphine compound is phenyldi(1-pyrenyl)phosphine.

13. A method for manufacturing a display device having a plurality of light-emitting elements on a substrate, the method comprising the step of carrying out the method for manufacturing a light-emitting element according to any one of claims 1 to 12.

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