Display device and method for manufacturing display device

Abstract

A display device (1) includes a substrate (2), and a first light-emitting element (4B) and a second light-emitting element (4G) on the substrate. The first light-emitting element has: a first light-emitting layer (45B) containing a first quantum dot (51B) and a first ligand (52B) having a dipole moment (M1) in a direction from a main chain (61) to a coordination functional group (62); and a first high dielectric layer (44B) located on the substrate side with respect to the first light emitting layer. The second light-emitting element has: a second light-emitting layer (45G) containing a second quantum dot (51G) and a second ligand (52G) having a dipole moment (M2) in a direction from the coordination functional group toward the main chain; and a second high dielectric layer (44G) located on the substrate side with respect to the second light emitting layer.

Description

Technical Field

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

[0002] Patent Document 1 discloses a method of forming a quantum dot layer on a substrate by electrophoretic volumetric method using a solution in which quantum dots are dispersed in a polar solvent. Prior art literature Patent Literature

[0003] Patent Document 1: Chinese Patent Application Publication No. 113809273 Summary of the Invention Technical problems to be solved by the present invention

[0004] In the method described in Patent Document 1, there is a possibility that only polar solvent molecules will be adsorbed on the substrate. In addition, in the method described in Patent Document 1, quantum dots may not be charged and thus cannot be effectively adsorbed on the substrate. Technical solutions to technical problems

[0005] A display device according to one embodiment of the present disclosure comprises: a substrate; and a first light-emitting element and a second light-emitting element on the substrate, wherein the first light-emitting element has a first light-emitting layer, the first light-emitting layer includes a first quantum dot and a first ligand, the first ligand has a dipole moment in the direction from the main chain to the coordination functional group, and the second light-emitting element has a second light-emitting layer, the second light-emitting layer includes a second quantum dot and a second ligand, and the second ligand has a dipole moment in the direction from the coordination functional group to the main chain.

[0006] A display device according to another embodiment of the present disclosure includes: a substrate; and a plurality of light-emitting elements on the substrate, each light-emitting element having: a light-emitting layer containing quantum dots; and a high dielectric layer located on the substrate side relative to the light-emitting layer.

[0007] A display device according to another embodiment of the present disclosure comprises: a substrate; and a first light-emitting element and a second light-emitting element on the substrate, wherein the first light-emitting element comprises: a first light-emitting layer, the first light-emitting layer comprising first quantum dots and first ligands, the first ligands having a dipole moment in a direction from a main chain to a coordinated functional group; and a first high dielectric layer, the first high dielectric layer being located on the substrate side relative to the first light-emitting layer; the second light-emitting element comprises: a second light-emitting layer, the second light-emitting layer comprising second quantum dots and second ligands, the second ligands having a dipole moment in a direction from a coordinated functional group to the main chain; and a second high dielectric layer, the second high dielectric layer being located on the substrate side relative to the second light-emitting layer.

[0008] A method for manufacturing a display device according to one embodiment of the present disclosure includes: preparing a substrate; forming a first electrode and a second electrode on the substrate; forming a high dielectric layer on the substrate that overlaps with the first electrode and the second electrode respectively in a plan view of the substrate; synthesizing a first solution, wherein the first solution contains a first quantum dot and a first ligand, wherein the first ligand has a dipole moment in a direction from the main chain to the coordination functional group; synthesizing a second solution, wherein the second solution contains a second quantum dot and a second ligand, wherein the second ligand has a dipole moment in a direction from the coordination functional group to the main chain; immersing the substrate on which the high dielectric layer is formed in the first solution; applying a voltage to at least one of the first electrode and the second electrode of the substrate immersed in the first solution, so that the first quantum dot is adsorbed on the high dielectric layer that overlaps with the first electrode in a plan view of the substrate; immersing the substrate on which the high dielectric layer is formed in the second solution; and applying a voltage to at least one of the first electrode and the second electrode of the substrate immersed in the second solution, so that the second quantum dot is adsorbed on the high dielectric layer that overlaps with the second electrode in a plan view of the substrate. Beneficial effects

[0009] Provided is a display device including a light-emitting element capable of efficiently forming a light-emitting layer even by electrophoretic deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic side sectional view of the display device and a schematic diagram of the quantum dot structure according to the first embodiment. Figure 2 This is a schematic plan view of the display device according to the first embodiment. Figure 3 This is a flowchart showing a method for manufacturing the display device according to the first embodiment. Figure 4 These are cross-sectional views showing steps of the method for manufacturing the display device according to the first embodiment. Figure 5 This is a cross-sectional view showing a step in the method for manufacturing another display device according to the first embodiment. Figure 6 This is a cross-sectional view showing a step in the method for manufacturing another display device according to the first embodiment. Figure 7 This is a cross-sectional view showing a step in the method for manufacturing another display device according to the first embodiment. Figure 8 This is an equivalent circuit diagram of a pixel circuit and an anode of the display device according to the first embodiment. Figure 9This is a schematic side sectional view of a display device according to a second embodiment. DETAILED DESCRIPTION

[0011] [First embodiment] [Display Device: Overview] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals and their description will be omitted.

[0012] Figure 2 This is a schematic plan view of a display device according to this embodiment. Display device 1 is a device that can be used as a display, such as a television or smartphone. Display device 1 includes a display portion DA and a frame portion NA formed around the periphery of display portion DA. Display device 1 displays on display portion DA by controlling the light emission from each of a plurality of light-emitting elements (described later) formed in display portion DA. Drivers, etc. for driving each of the plurality of light-emitting elements in display portion DA may also be formed on frame portion NA.

[0013] Figure 1 101, a schematic side cross-sectional view of a display device according to the present embodiment, a schematic diagram 102 of a quantum dot structure, a schematic diagram 103, and a schematic diagram 104. In the present disclosure, the direction from a substrate 2 of the display device 1 described later toward the light-emitting element 4 is sometimes described as "upper," and the opposite direction is sometimes described as "lower."

[0014] The schematic side cross-sectional view 101 is Figure 2 10. The schematic side cross-sectional view 101 is a diagram showing a cross section through the blue sub-pixel SPB, green sub-pixel SPG, and red sub-pixel SPR, described later, in a plan view of the substrate 2 of the display device 1 according to this embodiment. Schematic diagrams 102, 103, and 104 are diagrams showing enlarged views of one of the blue quantum dot structures 5B, green quantum dot structures 5G, and red quantum dot structures 5R, respectively, described later.

[0015] As shown in a schematic side cross-sectional view 101, a display device 1 includes a substrate 2, a pixel circuit layer 3, and light-emitting elements 4. In a plan view of the substrate 2, the display device 1 arranges a blue sub-pixel SPB, which forms a blue light-emitting element 4B (described later), a green sub-pixel SPG, which forms a green light-emitting element 4G, and a red sub-pixel SPR, which forms a red light-emitting element 4R. The blue light-emitting element 4B, the green light-emitting element 4G, and the red light-emitting element 4R emit blue light, green light, and red light, respectively. Thus, the display device 1 individually controls these light-emitting elements, for example, using a driver (not shown), thereby achieving color display.

[0016] In this embodiment, blue light is, for example, light having a central emission wavelength in the wavelength range of 380 nm to 500 nm. Furthermore, green light is, for example, light having a central emission wavelength in the wavelength range of 500 nm to 600 nm. Furthermore, red light is light having a central emission wavelength in the wavelength range of 600 nm to 780 nm.

[0017] <Display Device: Substrate and Pixel Circuit Layer> In this embodiment, the substrate 2 may be a rigid substrate such as a glass substrate, or a flexible substrate such as a film substrate.

[0018] The pixel circuit layer 3 includes a plurality of pixel circuits 31 formed on the substrate 2 , contact portions 32 electrically connecting each pixel circuit 31 to an anode 41 described later, and a planarizing film 33 that planarizes the pixel circuit layer 3 .

[0019] Pixel circuit 31 includes pixel circuit 31B formed in the blue sub-pixel SPB, pixel circuit 31G formed in the green sub-pixel SPG, and pixel circuit 31R formed in the red sub-pixel SPR. Contact portion 32 includes contact portion 32B formed in the blue sub-pixel SPB, contact portion 32G formed in the green sub-pixel SPG, and contact portion 32R formed in the red sub-pixel SPR. Each pixel circuit 31 is driven by a driver (not shown), and a voltage is applied to the anode 41 of each light-emitting element 4 via each contact portion 32.

[0020] The planarization film 33 is an organic film such as polyimide, and planarizes the upper surface of the pixel circuit layer 3 on which the light emitting element 4 is formed. The contact portion 32 may be formed in a contact hole formed in the planarization film 33 .

[0021] <Display Device: Light-Emitting Element: Overview> The light-emitting element 4 is sequentially stacked on the pixel circuit layer 3 and includes an anode 41, a hole injection layer 42, a hole transport layer 43, a high dielectric layer 44, a light-emitting layer 45, an electron transport layer 46, and a cathode 47. However, in this embodiment, if the high dielectric layer 44 is located closer to the substrate 2 than the light-emitting layer 45, the configuration is not limited to the above. For example, the light-emitting element 4 may also include a cathode 47, an electron transport layer 46, a high dielectric layer 44, a light-emitting layer 45, a hole transport layer 43, a hole injection layer 42, and an anode 41 stacked in this order on the pixel circuit layer 3.

[0022] The light-emitting element 4 includes a blue light-emitting element 4B as a first light-emitting element, a green light-emitting element 4G as a second light-emitting element, and a red light-emitting element 4R as a third light-emitting element. As described above, the blue light-emitting element 4B is formed in the blue sub-pixel SPB, the green light-emitting element 4G is formed in the green sub-pixel SPG, and the red light-emitting element 4R is formed in the red sub-pixel SPR.

[0023] Moreover, the display device 1 has a bank BK on the pixel circuit layer 3. The bank BK may also be an insulating layer having visible light absorptivity or light-shielding properties. As a material for the bank BK, for example, a photosensitive resin to which a light absorber such as carbon black is added can be cited. As the above-mentioned photosensitive resin, organic insulating materials having photosensitivity such as polyimide and acrylic resin can be cited. The bank BK divides the plurality of light-emitting elements 4, and in particular, is formed between the plurality of anodes 41 in a planar view of the substrate 2. In this embodiment, the light-emitting layer 45 is divided into each sub-pixel by the bank BK. In addition, the hole injection layer 42, the hole transport layer 43, the high dielectric layer 44, the electron transport layer 46 and the cathode 47 are formed in common in the plurality of sub-pixels. However, the hole injection layer 42, the hole transport layer 43, the high dielectric layer 44, the electron transport layer 46 and the cathode 47 can also be divided into each sub-pixel by the bank BK.

[0024] The bank BK may be formed at a position covering the end of each anode 41. In other words, the bank BK may have an opening partially at the portion overlapping with each anode 41 in a plan view of the substrate 2. In this case, the bank BK can reduce the influence of electric field concentration at the end of the anode 41 in each light-emitting element 4 on hole injection from the anode 41 into the light-emitting layer 45.

[0025] The blue light-emitting element 4B includes an anode 41B, which overlaps with the blue sub-pixel SPB in a plan view of the substrate 2, a hole injection layer 42, a hole transport layer 43, a high dielectric layer 44, a blue light-emitting layer 45B, an electron transport layer 46, and a cathode 47. The green light-emitting element 4G includes an anode 41G, which overlaps with the green sub-pixel SPG in a plan view of the substrate 2, a hole injection layer 42, a hole transport layer 43, a high dielectric layer 44, a green light-emitting layer 45G, an electron transport layer 46, and a cathode 47. The red light-emitting element 4R includes an anode 41R, which overlaps with the red sub-pixel SPR in a plan view of the substrate 2, a hole injection layer 42, a hole transport layer 43, a high dielectric layer 44, a red light-emitting layer 45R, an electron transport layer 46, and a cathode 47.

[0026] Specifically, blue light-emitting element 4B includes anode 41B as a first electrode and blue light-emitting layer 45B as a first light-emitting layer. Furthermore, green light-emitting element 4G includes anode 41G as a second electrode and green light-emitting layer 45G as a second light-emitting layer. Furthermore, red light-emitting element 4R includes red light-emitting layer 45R as a third light-emitting layer.

[0027] <Display Device: Light-Emitting Element: Anode and Cathode> At least one of the anode 41 and the cathode 47 is a transparent electrode that transmits visible light. As the transparent electrode, for example, ITO, InZnO, SnO2, or FTO can also be used. Furthermore, either the anode 41 or the cathode 47 can be a reflective electrode. The reflective electrode can include a metal material with high reflectivity for visible light, such as Al, Ag, Cu, or Au, alone or in alloys thereof. The anode 41 can include the same material across the multiple light-emitting elements 4, or different materials.

[0028] Each anode 41 is electrically connected to each pixel circuit 31 via a contact portion 32. Furthermore, a predetermined voltage from, for example, an auxiliary power supply (not shown) is applied to the cathode 47. Therefore, the display device 1 controls the application of a voltage to each anode 41 via each pixel circuit 31 using a driver (not shown), thereby individually controlling the light emission from each light-emitting element 4.

[0029] In particular, in this embodiment, the pixel circuit 31B electrically connected to the anode 41B as the first electrode is a first pixel circuit. In addition, in this embodiment, the pixel circuit 31G electrically connected to the anode 41G as the second electrode is a second pixel circuit.

[0030] <Display Device: Light-Emitting Element: Hole Injection Layer, Hole Transport Layer, and Electron Transport Layer> The hole injection layer 42 is a layer for injecting holes from the anode 41 into a layer closer to the light-emitting layer 45 than the anode 41. The hole injection layer 42 is electrically connected to each anode 41 via the opening of the bank BK. As the material of the hole injection layer 42, organic or inorganic materials with hole transport properties that have been used in the past in light-emitting elements including quantum dots can be used. Examples of the material of the hole injection layer 42 include a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrenesulfonic acid (PSS) (abbreviated as "PEDOT:PSS"), NiO (nickel oxide), CuSCN (copper thiocyanate), etc. In addition, these materials can be used alone or in combination of two or more.

[0031] The hole transport layer 43 is a layer that transports the holes injected from the anode 41 into the hole injection layer 42 to the light-emitting layer 45 side. The material of the hole transport layer 43 can use organic or inorganic materials with hole transport properties that have been used in light-emitting elements containing quantum dots. As the material of the hole transport layer 43, for example, 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"), polyvinyl carbazole (abbreviated as "PVK"), etc. Regarding these materials, only one kind can be used, or two or more kinds can be appropriately mixed and used.

[0032] The electron transport layer 46 is a layer that transports electrons injected from the cathode 47 to the light-emitting layer 45. The material of the electron transport layer 46 can be an organic or inorganic material with electron transport properties that has been used in light-emitting elements containing quantum dots. As the material of the electron transport layer 46, for example, ZnO (zinc oxide) nanoparticles, MgZnO (magnesium zinc oxide) nanoparticles, 2,2',2"-(1,3,5-biphenyltriyl)-tris(1-phenyl-1-H-benzimidazole) (abbreviated as "TPBi"), etc. can be listed. Regarding these materials, only one kind can be used, or two or more kinds can be appropriately mixed and used.

[0033] The hole injection layer 42, hole transport layer 43, and electron transport layer 46 may comprise the same material across multiple light-emitting elements 4, or they may comprise different materials. In particular, to improve the efficiency of hole and electron injection into each light-emitting layer 45, the materials for the hole injection layer 42, hole transport layer 43, and electron transport layer 46 of each light-emitting element 4 may be selected based on the band gap of the material of each light-emitting layer 45. Furthermore, the hole injection layer 42, hole transport layer 43, and electron transport layer 46 may be formed commonly across multiple sub-pixels, for example, on the upper surface of the bank BK.

[0034] <Display Device: Light Emitting Element: High Dielectric Layer> The high-dielectric layer 44 is located closer to the substrate 2 than the light-emitting layer 45. For example, the high-dielectric layer 44 can be formed between the hole-transporting layer 43 and the light-emitting layer 45, or in particular, can be in contact with the light-emitting layer 45. The relative dielectric constant of the high-dielectric layer 44 is higher than the relative dielectric constants of the layers of the light-emitting element 4 located closer to the substrate 2 than the high-dielectric layer 44. Specifically, the relative dielectric constant of the high-dielectric layer 44 is higher than the relative dielectric constants of the hole-injection layer 42 and the hole-transporting layer 43. Furthermore, the relative dielectric constant of the high-dielectric layer 44 is higher than the relative dielectric constant of the bank BK.

[0035] The high dielectric layer 44 may comprise, for example, at least one of silicon oxide, silicon nitride, and an oxide of a Group IV element. Silicon oxide may comprise, for example, SiO2, silicon nitride may comprise, for example, SiN, and oxides of a Group IV element may comprise, for example, hafnium oxide such as HfO2. The high dielectric layer 44 comprising silicon oxide, silicon nitride, or an oxide of a Group IV element can achieve both an increased relative dielectric constant and reduced cost.

[0036] The high-dielectric layer 44 may have a thickness sufficient to allow holes transported from the hole transport layer 43 to the light-emitting layer 45 to pass through the high-dielectric layer 44 by the tunnel effect. For example, the thickness of the high-dielectric layer 44 may be greater than 1 nm and less than 100 nm. By setting the thickness of the high-dielectric layer 44 to less than 100 nm, it is possible to effectively prevent the high-dielectric layer 44 from obstructing hole transport from the hole transport layer 43 to the light-emitting layer 45. By setting the thickness of the high-dielectric layer 44 to greater than 1 nm, the film-forming properties of the high-dielectric layer 44 can be improved.

[0037] In this embodiment, the high dielectric layer 44 includes a high dielectric layer 44B as the first high dielectric layer in the blue sub-pixel SPB, a high dielectric layer 44G as the second high dielectric layer in the green sub-pixel SPG, and a high dielectric layer 44R in the red sub-pixel SPR. High dielectric layer 44B, high dielectric layer 44G, and high dielectric layer 44R can each be part of the high dielectric layer 44 shared by multiple sub-pixels. Therefore, the high dielectric layer 44 can include the same material or different materials among the multiple light-emitting elements 4. Furthermore, in this embodiment, the red light-emitting element 4R does not need to include the high dielectric layer 44R.

[0038] <Display device: Light-emitting element: Light-emitting layer: Quantum dot> As described above, the light-emitting layer 45 includes the blue light-emitting layer 45B, the green light-emitting layer 45G, and the red light-emitting layer 45R. The blue light-emitting layer 45B, the green light-emitting layer 45G, and the red light-emitting layer 45R are formed at positions overlapping with the blue sub-pixel SPB, the green sub-pixel SPG, and the red sub-pixel SPR, respectively, in a planar view of the substrate 2.

[0039] Each light-emitting layer 45 includes a plurality of quantum dot structures, each comprising quantum dots and ligands having coordinating functional groups capable of coordinating with the quantum dots. In particular, the blue light-emitting layer 45B, the green light-emitting layer 45G, and the red light-emitting layer 45R include a plurality of blue quantum dot structures 5B, green quantum dot structures 5G, and red quantum dot structures 5R, respectively. The plurality of quantum dot structures in each light-emitting layer 45 can be arranged irregularly, as shown in the schematic side cross-section 101, or can be arranged regularly.

[0040] For the quantum dot structure included in each light emitting layer 45, refer to Figure 1 Schematic diagram 102, schematic diagram 103, and schematic diagram 104 are used to illustrate. As shown in schematic diagram 102, the blue quantum dot structure 5B includes a blue quantum dot 51B as a first quantum dot and a first ligand 52B. As shown in schematic diagram 103, the green quantum dot structure 5G includes a green quantum dot 51G as a second quantum dot and a second ligand 52G. As shown in schematic diagram 104, the red quantum dot structure 5R includes a red quantum dot 51R as a third quantum dot and a third ligand 52R.

[0041] Blue quantum dot 51B, green quantum dot 51G, and red quantum dot 51R include at least a core. Holes from anode 41 and electrons from cathode 47 are injected into the core of each quantum dot. These holes and electrons recombine, and the excitons generated by the recombination emit light. Blue quantum dot 51B, green quantum dot 51G, and red quantum dot 51R emit blue light, green light, and red light from their cores, respectively.

[0042] In addition, in the present invention, "quantum dot" refers to a dot having a maximum width of 100 nm or less. The shape of the quantum dot is not particularly limited as long as it satisfies the above-mentioned maximum width range, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). The shape of the quantum dot can be, for example, a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with concave and convex surfaces, or a combination of these shapes.

[0043] Quantum dots are typically preferably made of semiconductors. Semiconductors may have a certain band gap. Semiconductors can be any material that can emit light, and furthermore, they may contain at least the following materials. Semiconductors can emit blue, green, and red light, respectively. For example, semiconductors include at least one selected from the group consisting of II-VI compounds, III-V compounds, chalcogen compounds, and perovskite compounds. In addition, II-VI compounds refer to compounds containing Group II elements and Group VI elements, and III-V compounds refer to compounds containing Group III elements and Group V elements. In addition, Group II elements include Group 2 elements and Group 12 elements, Group III elements include Group 3 elements and Group 13 elements, Group V elements include Group 5 elements and Group 15 elements, and Group VI elements may include Group 6 elements and Group 16 elements.

[0044] The II-VI group compound contains, 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.

[0045] The Group III-V compound includes, for example, at least one selected from the group consisting of GaAs, GaP, InN, InAs, InP, and InSb.

[0046] Chalcogenides are compounds containing Group VIA (16) elements, such as CdS or CdSe. Chalcogenides may also contain mixed crystals of these elements.

[0047] The perovskite compound has a composition represented by the general formula CsPbX 3 , for example. The constituent element X includes at least one selected from the group consisting of Cl 1 , Br, and I, for example.

[0048] Here, the numbering notations of element groups using Roman numerals are based on the old IUPAC (International Union of Pure and Applied Chemistry) method or the old CAS (Chemical Abstracts Service) method, and the numbering notations of element groups using Arabic numerals are based on the current IUPAC method.

[0049] Blue quantum dots 51B, green quantum dots 51G, and red quantum dots 51R may also have a so-called core / shell structure, in which a shell is located at least partially around a core. The shell of each quantum dot may also have a core-protecting function, such as compensating for defects in the core of each quantum dot. Furthermore, blue quantum dots 51B, green quantum dots 51G, and red quantum dots 51R may have various conventionally known structures as quantum dot structures.

[0050] <Display Device: Light-Emitting Element: Light-Emitting Layer: Ligand> The first ligand 52B, the second ligand 52G, and the third ligand 52R each have a main chain 61, such as a carbon chain, and a coordinating functional group 62 located at one end of the main chain 61. The coordinating functional group 62 is a functional group capable of forming a coordinating bond with the outermost surfaces of the blue quantum dot 51B, the green quantum dot 51G, and the red quantum dot 51R.

[0051] In the present disclosure, the main chain 61 can be a neutral, nonpolar molecule that does not ionize even in polar solvents, such as a carbon chain. The coordinating functional group 62 is a polar functional group capable of forming a coordination bond with the quantum dot. Furthermore, when observing a cross-section of the light-emitting layer 45, if a ligand is identified within 10 nm of the outermost surface of the quantum dot, the ligand can be considered to be coordinated with the quantum dot.

[0052] The first ligand 52B has an acidic group 63 at one end of the main chain 61 opposite the coordinating functional group 62. The acidic group 63 is a functional group that becomes negatively charged by releasing a proton into a polar medium such as water. The first ligand 52B may contain an acidic group 63 that becomes negatively charged without losing a proton. The acidic group 63 may include, for example, a carbonyl group, a phosphite group, an aldehyde group, or a sulfonyl group. For example, the first ligand 52B may contain a polyethylene glycol carboxylic acid represented by the following chemical formula. In this case, the first ligand 52B contains a carbonyl group as the acidic group 63.

[0053] [Chemical Formula 1] -RO-(CH2)n-COOH In the above chemical formula, "R" is a substituent containing carbon or hydrogen, and "n" is the degree of polymerization, which is, for example, an integer of 1 to 12. The first ligand 52B comprising polyethylene glycol carboxylic acid releases a proton into a polar solvent such as water, and becomes negatively charged as shown in the following chemical formula.

[0054] [Chemical Formula 2] -RO-(CH2)n-COO - Therefore, the first ligand 52B is a polar molecule whose electron cloud is more inclined toward the acidic group 63 side than the coordinating functional group 62 side of the main chain 61. In particular, in this embodiment, the dipole moment attributable to the acidic group 63 is sufficiently greater than the dipole moment attributable to the coordinating functional group 62. Therefore, the first ligand 52B as a whole has a dipole moment M1 in the direction from the main chain 61 toward the coordinating functional group 62.

[0055] The second ligand 52G has a basic group 64 at one end of the main chain 61 opposite to the coordinating functional group 62. The basic group 64 is a functional group that becomes positively charged by receiving a proton from a polar medium such as water. The second ligand 52G may include a basic group 64 that becomes positively charged by receiving a proton. The basic group 64 may include, for example, an imino group, a hydroxyl group, an amino group, a hydroxyl group, or an alkoxide group. For example, the second ligand 52G may include an imine as shown in the following chemical formula. In this case, the second ligand 52G includes an imino group as the basic group 64.

[0056] [Chemical Formula 3] In addition, in the above chemical formula, "R 1 ”, “R 2 ” and “R 3 " is a carbon-hydrogen-containing substituent and may be the same as or different from each other. The second ligand 52G containing an imine receives a proton from a polar solvent such as water, and becomes positively charged as shown in the following chemical formula.

[0057] [Chemical Formula 4] Therefore, the second ligand 52G is a polar molecule whose electron cloud is more biased toward the coordinating functional group 62 than toward the basic group 64 of the main chain 61. In particular, in this embodiment, the dipole moment attributable to the basic group 64 is sufficiently greater than the dipole moment attributable to the coordinating functional group 62. Therefore, the second ligand 52G as a whole has a dipole moment M2 in the direction from the coordinating functional group 62 toward the main chain 61.

[0058] The third ligand 52R has a neutral group 65 at one end of the main chain 61 opposite to the coordinating functional group 62. The neutral group 65 is a functional group that does not donate or accept protons or is in equilibrium with the polar solvent even in a polar medium such as water. Therefore, the third ligand 52R is uncharged and neutral in a polar solvent. The neutral group 65 includes, for example, an alkyl group or an allyl group. Therefore, the third ligand 52R as a whole is a non-polar molecule with a small deviation in the electron cloud. For example, the third ligand 52R is a molecule that can be dispersed in water.

[0059] In this embodiment, the first ligand 52B and the second ligand 52G are not limited to the above-described configuration. In this embodiment, the first ligand 52B can be any polar molecule having a dipole moment M1, and the second ligand 52G can be any polar molecule having a dipole moment M2. As long as the above-described configuration is met, the first ligand 52B and the second ligand 52G do not need to be charged in a polar solvent.

[0060] <Method for Manufacturing Display Device: Until Formation of Red Light-Emitting Layer> Reference Figures 3 to 7 A method for manufacturing the display device 1 according to this embodiment will be described in detail. Figure 3 This is a flowchart showing a method for manufacturing the display device 1 according to this embodiment. Figures 4 to 7 is a cross-sectional view of the process of the display device 1 of this embodiment, showing Figure 1 The cross section of the display device 1 shown in the schematic side cross section 101 corresponds to the cross section of the display device 1 .

[0061] In the method for manufacturing a display device 1 of this embodiment, a substrate 2 is first prepared (step S1). The substrate 2 can be prepared by, for example, cutting a glass substrate or a film substrate into a predetermined shape. Alternatively, a large substrate 2 can be prepared and then cut into pieces after each step, thereby dividing the substrate 2 into a plurality of display devices 1.

[0062] Next, the pixel circuit layer 3 is formed on the substrate 2 (step S2). Step S2 can also be performed, for example, by forming the pixel circuit 31 at a position overlapping with each sub-pixel on the substrate 2 in a planar view of the substrate 2, after forming a planarization film 33 by coating or other means, and then forming the contact portion 32 in the planarization film 33. The contact portion 32 can also be formed by forming a contact hole in the portion of the planarization film 33 that overlaps with the pixel circuit 31 in a planar view of the substrate 2 by etching or other means, and then forming a film of a conductive material in the contact hole by sputtering or other means.

[0063] Next, an anode 41 is formed on the pixel circuit layer 3 (step S3). The anode 41 can also be formed by, for example, forming a thin film of a metal material on the pixel circuit layer 3 by sputtering or the like, and then patterning it by dry etching or the like. Therefore, in step S3, in a plan view of the substrate 2, the anode 41B serving as the first electrode is formed at a position overlapping with the blue sub-pixel SPB, and the anode 41G serving as the second electrode is formed at a position overlapping with the green sub-pixel SPG.

[0064] In step S3, each anode 41 is formed at a position overlapping with each contact portion 32 in a plan view of the substrate 2. Thus, each anode 41 is electrically connected to each pixel circuit 31 via each contact portion 32. In particular, by forming anode 41B as a first electrode on substrate 2, anode 41B is electrically connected to pixel circuit 31B as a first pixel circuit. Furthermore, by forming anode 41G as a second electrode on substrate 2, anode 41G is electrically connected to pixel circuit 31G as a second pixel circuit.

[0065] Next, banks BK are formed on the pixel circuit layer 3 and the anode 41 (step S4). For example, after coating a film of a photosensitive resin material on the substrate 2 and the anode 41, an opening is provided at a position overlapping the anode 41 in a plan view of the substrate 2 using photolithography or the like, thereby forming the banks BK.

[0066] Next, a hole injection layer 42 is formed on the anode 41 (step S5). The hole injection layer 42 can be formed by, for example, applying a material having hole transport properties to form a film between the banks BK and on the anode 41 in a plan view of the substrate 2 using an inkjet method. Alternatively, the hole injection layer 42 can be formed by, for example, applying a material having hole transport properties to form a film on the anode 41 and on the banks BK using a spin coating method.

[0067] Next, the hole transport layer 43 is formed on the hole injection layer 42 (step S6 ). The hole transport layer 43 can be formed in the same manner as step S6 , or by coating a hole transporting material on a portion including the hole injection layer 42 .

[0068] Next, a high dielectric layer 44 is formed on the hole transport layer 43 (step S7). The high dielectric layer 44 can also be formed by, for example, applying the above-mentioned high dielectric constant material to form a film between the banks BK and on the hole transport layer 43 in a plan view of the substrate 2 using an inkjet method. Alternatively, the high dielectric layer 44 can also be formed by, for example, applying the above-mentioned high dielectric constant material to form a film on the hole transport layer 43 and on the banks BK using a spin coating method. By the end of step S7, a layer including Figure 4 The laminated body of the substrate 2 shown in step S3.

[0069] In particular, step S7 forms high dielectric layer 44B, which overlaps anode 41B in a plan view of substrate 2, and high dielectric layer 44G, which overlaps anode 41G. Furthermore, in this embodiment, as described above, high dielectric layer 44 is formed before forming light-emitting layer 45. Therefore, in the display device 1 manufactured by the method for manufacturing a display device 1 according to this embodiment, high dielectric layer 44 is located closer to substrate 2 than light-emitting layer 45.

[0070] Next, in this embodiment, a red light-emitting layer 45R is first formed in the light-emitting layer 45 (step S8). The red light-emitting layer 45R can be formed, for example, by applying a solution in which the red quantum dot structure 5R is dispersed in a solvent to form a film between the bank walls BK and on the hole transport layer 43 in a plan view of the substrate 2 by an inkjet method, and then drying the solution. In the solution in which the red quantum dot structure 5R is dispersed, the concentration of the third ligand 52R can be 1 to 100 mg / mL. Thus, as Figure 4 As shown in step S8 , a red light-emitting layer 45R including a plurality of red quantum dot structures 5R is formed.

[0071] Alternatively, the red light-emitting layer 45R can also be formed by a stripping method using a sacrificial layer. In this case, first, a sacrificial layer is formed at a position other than the red sub-pixel SPR in a plan view of the substrate 2, for example, by coating a photosensitive resin material and patterning by photolithography. Then, a solution containing the red quantum dot structure 5R is coated into a film by spin coating or the like, and the solution is dried to form a layer containing the red quantum dot structure 5R. Then, the sacrificial layer is cleaned with an appropriate cleaning solution, and the sacrificial layer is removed together with the layer containing the red quantum dot structure 5R on the sacrificial layer. In this way, the layer containing the red quantum dot structure 5R can remain only in the red sub-pixel SPR, and the red light-emitting layer 45R can be formed.

[0072] <Method for Manufacturing Display Device: Synthesis of Quantum Dot Material> In the method for manufacturing the display device 1 of the present embodiment, a synthesis process of solutions used for forming the blue light-emitting layer 45B and the green light-emitting layer 45G is performed from step S1 to completion of step S8 .

[0073] For example, in this embodiment, the synthesis of the first solution is performed in parallel with the process from step S1 to step S8 (step S9). The first solution is a solution in which the blue quantum dot structure 5B is dispersed, in other words, a solution containing blue quantum dots 51B and the first ligand 52B. The first solution can be synthesized by mixing blue quantum dots 51B and the first ligand 52B synthesized by various methods, for example, in a polar solvent such as water. In addition, the first solution can also be synthesized by mixing an excess amount of the first ligand 52B in a solution in which blue quantum dots 51B coordinated by an organic ligand different from the first ligand 52B are dispersed in a polar solvent, and then stirring the solution. In this case, the blue quantum dot structure 5B is synthesized in the solution by replacing the ligand coordinated to the blue quantum dots 51B with the first ligand 52B.

[0074] In addition, in this embodiment, following step S9, a second solution is synthesized (step S10). The second solution is a solution in which green quantum dot structures 5G are dispersed, in other words, a solution containing green quantum dots 51G and second ligands 52G. The second solution can be synthesized by replacing the blue quantum dots 51B with green quantum dots 51G and the first ligands 52B with second ligands 52G in the same manner as the first solution.

[0075] <Method for Manufacturing Display Device: Forming Blue Light-Emitting Layer> After the formation of the red light emitting layer 45R and the synthesis of the first solution and the second solution are completed, in this embodiment, the laminate including the substrate 2 having the high dielectric layer 44 and the red light emitting layer 45R formed thereon is immersed in the first solution (step S11 ). Figure 5 Step S11 of FIG. 1 shows a case where a stacked body including substrate 2 is immersed in a first solution 71. For example, first solution 71 contains a plurality of blue quantum dot structures 5B dispersed in a first polar solvent 72. In step S11, the upper surface of red light-emitting layer 45R of the stacked body and, in a plan view of substrate 2, the upper surface of high dielectric layer 44 overlapping with blue sub-pixel SPB and green sub-pixel SPG are exposed to first solution 71 in which the plurality of blue quantum dot structures 5B are dispersed.

[0076] Next, voltage is applied to the anode 41B serving as the first anode (step S12 ). The voltage application to the anode 41B is performed by, for example, applying voltage to the pixel circuit 31B using a method described later.

[0077] In particular, in this embodiment, a voltage is applied to anode 41B so that anode 41B has a higher potential than anodes 41R and 41G. Therefore, an electric field is formed between anode 41B and the other anodes 41 in a direction from anode 41B toward the other anodes 41.

[0078] Furthermore, by applying the aforementioned voltage to anode 41, the layers overlapping anode 41B in a plan view of substrate 2, in other words, the layers of the blue subpixel SPB, are polarized, with the top surface in particular becoming positively charged. In particular, the top surface of high dielectric layer 44B, which has a high relative dielectric constant, becomes more strongly positively charged. The electric field formed in the direction from anode 41B toward the other anodes 41 becomes stronger due to the positively charged top surface of high dielectric layer 44B.

[0079] Furthermore, by applying the above-described voltage to anode 41, the layers overlapping anodes 41R and 41G in a plan view of substrate 2, in other words, the layers of red subpixel SPR and green subpixel SPG, are polarized, with their top surfaces becoming particularly negatively charged. In particular, the top surfaces of high dielectric layers 44R and 44G, each having a high relative dielectric constant, are more strongly negatively charged. The electric field formed in the direction from anode 41B toward the other anode 41 by high dielectric layers 44R and 44G, whose top surfaces have a negative charge, becomes even stronger.

[0080] Here, in step S12, a blue quantum dot structure 5B including blue quantum dots 51B is dispersed in the first solution 71 in which the laminate including the substrate 2 is immersed. The blue quantum dots 51B are coordinated with the first ligand 52B having the negatively charged acidic group 63. Therefore, the acidic group 63 of the first ligand 52B is attracted to the anode 41B by the electric field. Figure 5 As shown in step S12 , the blue quantum dot structure 5B including the blue quantum dots 51B is adsorbed on the upper surface of the high dielectric layer 44B formed in the blue sub-pixel SPB.

[0081] Furthermore, even when the first ligand 52B of the blue quantum dot structure 5B in the first solution 71 is not negatively charged, the first ligand 52B still has a dipole moment M1. Therefore, the electric field generates an attractive force between the first ligand 52B and the positively charged high dielectric layer 44B. Therefore, even in this case, the blue quantum dot structure 5B is adsorbed to the upper surface of the high dielectric layer 44B.

[0082] Furthermore, to reduce the attraction of the blue quantum dots 51B to the red and green sub-pixels SPR and SPG, the electric field generated between the anodes 41R and 41G is preferably small. Therefore, to reduce the electric field generated between the anodes 41R and 41G, the potentials of the anodes 41R and 41G can be substantially the same. However, a potential difference between the anodes 41R and 41G is also acceptable as long as the attraction of the blue quantum dots 51B to the red and green sub-pixels SPR and SPG is sufficiently reduced.

[0083] Next, the stacked body of the substrate 2 containing the blue quantum dot structure 5B adsorbed on the upper surface of the high dielectric layer 44B is cleaned (step S13). In step S13, the stacked body is taken out from the first solution 71, and the stacked body is cleaned, for example, by a polar solvent containing PGMEA. Thus, the blue quantum dot structure 5B adsorbed on the upper surface of the high dielectric layer 44B is removed, for example, the blue quantum dot structure 5B attached to the upper surface of the red light-emitting layer 45R and the upper surface of the high dielectric layer 44G is washed. By the above, as Figure 6 As shown in step S13 , a blue light-emitting layer 45B is formed in the blue sub-pixel SPB.

[0084] <Method for Manufacturing Display Device, Voltage Application Method in Adsorption Step> Reference Figure 8 A specific method of applying a voltage to each anode 41 in step S12 will be described. Figure 8 is an equivalent circuit diagram of the pixel circuit 31 and the anode 41 of the display device 1. In particular, Figure 8 , an equivalent circuit diagram of the pixel circuit 31G, the pixel circuit 31B, the anode 41G, and the anode 41B of the display device 1 is shown in FIG. Figure 8 , wiring electrically connected to each pixel circuit 31 and each anode 41 is also shown.

[0085] In this embodiment, each pixel circuit 31 includes a drive transistor TR1, a write transistor TR2, and a capacitor C1. Specifically, in this embodiment, the gate of the drive transistor TR1 is connected to the source of the write transistor TR2. Furthermore, capacitor C1 is formed between the drain of the drive transistor TR1 and the source of the write transistor TR2. Each pixel circuit 31 is connected to each anode 41 by connecting the source of each drive transistor TR1 to each anode 41.

[0086] In addition, the pixel circuit layer 3 of this embodiment includes a plurality of data lines DL, power supply voltage lines VL, and scanning signal lines SL. Each pixel circuit 31 is connected to each of the data lines DL, power supply voltage lines VL, and scanning signal lines SL. In particular, each data line DL is connected to the drain of the write transistor TR2 in each pixel circuit 31. Furthermore, each power supply voltage line VL is connected to the drain of the drive transistor TR1 in each pixel circuit 31. Furthermore, each scanning signal line SL is connected to the gate of the write transistor TR2 in each pixel circuit 31.

[0087] Here, Figure 8 The pixel circuit 31G and the pixel circuit 31B shown are both connected to the operation signal line SLn. In addition, the pixel circuit 31G is connected to the data line DLn and the power supply voltage line VLn, and the pixel circuit 31B is connected to the data line DLn+1 and the power supply voltage line VLn+1.

[0088] During normal operation of the display device 1 after manufacture, a high-level power supply voltage ELVDD, for example, is applied to each power supply voltage line VL, and a potential signal corresponding to the grayscale data of each subpixel is applied to each data line DL. Therefore, while each scanning signal line SL is active, a potential signal corresponding to the grayscale data is supplied from each data line DL to each anode 41 connected thereto. Furthermore, a low-level power supply voltage ELVSS is applied to the cathode 47 via, for example, an auxiliary voltage (not shown). In this manner, the display device 1 drives each anode 41 individually based on the potential signal applied to each data line DL, thereby individually controlling the light emission from each subpixel and performing display.

[0089] On the other hand, in step S12, if Figure 8 As shown, the low-level power supply voltage ELVSS is applied to the power supply voltage line VLn connected to the pixel circuit 31G, and the high-level power supply voltage ELVDD is applied to the power supply voltage line VLn+1 connected to the pixel circuit 31B. Thus, voltage application to each pixel circuit 31 is performed in step S12.

[0090] In step S12, the voltage application may be performed using, for example, a driver used in normal display of the display device 1. In this case, the driver can implement the voltage application by switching the target of application of the low-level power supply voltage ELVSS from the auxiliary power supply from the cathode 47 to the power supply voltage line VLn.

[0091] Furthermore, in step S12, a predetermined voltage equal to or higher than the threshold voltage of the drive transistor TR1 and the write transistor TR2 of each pixel circuit 31 is applied to each data line DL and each scanning signal line SL. As described above, by applying a voltage to each pixel circuit 31 in step S12, a voltage is applied to each anode 41. In particular, in step S12, a higher voltage can be applied to the anode 41B than to the anode 41G.

[0092] Alternatively, pixel circuit 31R may have the same configuration as pixel circuit 31G or pixel circuit 31B. In this case, in step S12, a low-level power supply voltage ELVSS, for example, is applied to power supply voltage line VL connected to pixel circuit 31R. This allows a higher voltage to be applied to anode 41B than to anode 41R in step S12.

[0093] In summary, in this embodiment, voltage application to each anode 41 during the electrophoretic deposition process is performed by applying voltage to each pixel circuit 31 used during normal display of the display device 1. Thus, in this embodiment, voltage application to each anode 41 during the electrophoretic deposition process can be performed using a driver or the like used during normal display of the display device 1, eliminating the need for an external power supply or the like. Therefore, in this embodiment, the electrophoretic deposition process can be performed more simply.

[0094] While the method of applying voltage to both anode 41B and anode 41G during the electrophoretic deposition process of this embodiment has been described, the present invention is not limited thereto. For example, during the electrophoretic deposition process, a voltage may be applied to only one of anode 41B and anode 41G, thereby increasing the potential of anode 41B to a higher potential than that of anode 41G. For example, during the electrophoretic deposition process, anode 41G may be grounded while a predetermined positive voltage is applied to anode 41B.

[0095] Furthermore, in the electrophoretic deposition process of this embodiment, a method of applying voltage to both anode 41B and anode 41G by applying voltage to both pixel circuit 31B and pixel circuit 31G has been described, but the present invention is not limited thereto. For example, in the electrophoretic deposition process, a voltage may be applied to only one of pixel circuit 31B and pixel circuit 31G. In this case, a voltage may also be applied to only one of anode 41B and anode 41G.

[0096] The high-level power supply voltage ELVDD may also be the reverse voltage of the low-level power supply voltage ELVSS. In other words, during the electrophoretic deposition process, the voltage applied to anode 41B may be the reverse voltage of the voltage applied to anode 41G. Thus, in this embodiment, voltage application to each anode 41 during the electrophoretic deposition process can be performed more simply.

[0097] Furthermore, the configuration of the pixel circuit 31 is not limited thereto. As long as a higher voltage than the anodes 41R and 41G can be applied to the anode 41B, various conventionally known configurations may be employed. For example, the pixel circuit layer 3 may include an initialization signal line that supplies an initialization signal for initializing the potential signal applied to each anode 41. In this case, each pixel circuit 31 may also include an initialization transistor driven by the initialization signal supplied to the initialization signal line.

[0098] <Method for Manufacturing Display Device: Formation of Green Light-Emitting Layer> Next, the laminate including the substrate 2 on which the blue light emitting layer 45B is formed is immersed in the second solution (step S14). Figure 6 Step S14 of FIG. 1 shows a case where the stacked body including the substrate 2 is immersed in the second solution 73. For example, the second solution 73 contains a plurality of green quantum dot structures 5G dispersed in the second polar solvent 74. In step S14, the upper surfaces of the red light-emitting layer 45R and the blue light-emitting layer 45B of the stacked body, as well as the upper surface of the high dielectric layer 44 overlapping with the green sub-pixel SPG in a plan view of the substrate 2, are exposed to the second solution 73 in which the plurality of green quantum dot structures 5G are dispersed.

[0099] Next, voltage is applied to the anode 41G serving as the second anode (step S15 ). The voltage application to the anode 41G is performed by applying voltage to the pixel circuit 31G via a driver (not shown) by a method described later.

[0100] In particular, in this embodiment, voltage is applied to anode 41G so that anode 41G has a lower potential than other anodes 41. Therefore, an electric field is formed between anode 41G and other anodes 41 in a direction from other anodes 41 toward anode 41G.

[0101] The voltage application to each anode 41 in step S15 can be performed using the same method as the voltage application to each anode 41 in step S12, except for the voltage application to anode 41R. For example, in step S15, the voltage is applied to anode 41R so that anode 41R has a higher potential than anode 41G. For example, in step S15, the voltage application can be performed using the same method as in step S12, except that the power supply voltage applied to power supply voltage line VL connected to pixel circuit 31R is set to high-level power supply voltage ELVDD.

[0102] In step S15 , the upper surface of high dielectric layer 44G is strongly negatively charged, and the upper surfaces of high dielectric layers 44R and 44B are strongly positively charged. Therefore, the electric field formed in the direction from the other anodes 41 toward anode 41G becomes stronger.

[0103] Here, in step S15, the second solution 73 in which the laminate including the substrate 2 is immersed contains a green quantum dot structure 5G including green quantum dots 51G, which is coordinated with the second ligand 52G having a positively charged basic group 64. Therefore, the basic group 64 of the second ligand 52G is attracted to the anode 41G by the above-mentioned electric field. Figure 7 As shown in step S15 , the green quantum dot structure 5G including the green quantum dots 51G is adsorbed onto the upper surface of the high dielectric layer 44G formed in the green sub-pixel SPG.

[0104] Furthermore, in the second solution 73, even when the second ligand 52G of the green quantum dot structure 5G is not negatively charged, the second ligand 52G still has a dipole moment M2. Therefore, the electric field generates an attractive force between the second ligand 52G and the negatively charged high dielectric layer 44G. Therefore, even in this case, the green quantum dot structure 5G is adsorbed to the upper surface of the high dielectric layer 44G.

[0105] Next, the laminate including the substrate 2 having the green quantum dot structure 5G adsorbed on the upper surface of the high dielectric layer 44G is cleaned (step S16). Step S16 can be performed by the same method as step S13. Thus, the green quantum dot structure 5G adsorbed on the upper surface of the high dielectric layer 44G is removed, for example, the green quantum dot structure 5G attached to the upper surface of the red light-emitting layer 45R and the upper surface of the blue light-emitting layer 45B is washed. As described above, Figure 7 As shown in step S16 , the green light emitting layer 45G is formed in the green sub-pixel SPG, and the formation process of the light emitting layer 45 is completed.

[0106] <Method for Manufacturing Display Device: After Forming Electron Transport Layer> Next, the electron transport layer 46 is formed on the light emitting layer 45 (step S17 ). The electron transport layer 46 can be formed similarly to step S6 or step S7 , or by coating a material having electron transport properties on a portion including the light emitting layer 45 .

[0107] Next, cathode 47 is formed on electron transport layer 46 (step S18). Cathode 47 can be formed by depositing a thin film of a metal material on electron transport layer 46, for example, by sputtering. Cathode 47 can also be formed so as to be electrically connected to the auxiliary power supply. The above steps complete the manufacturing process of display device 1.

[0108] <Effects of the Display Device> The blue light-emitting layer 45B of the display device 1 includes a blue quantum dot structure 5B, which includes blue quantum dots 51B and first ligands 52B coordinated to the blue quantum dots 51B. Furthermore, the green light-emitting layer 45G includes a green quantum dot structure 5G, which includes green quantum dots 51G and second ligands 52G coordinated to the green quantum dots 51G.

[0109] The first ligand 52B has a dipole moment M1 in the direction from the main chain 61 toward the coordinating functional group 62. Therefore, in step S12, an attractive force is generated between the first ligand 52B coordinated to the blue quantum dot 51B and the anode 41B. Therefore, in step S12, even if no attractive force is generated between the blue quantum dot 51B and the anode 41B, the blue quantum dot 51B is attracted to the blue sub-pixel SPB.

[0110] The second ligand 52G has a dipole moment M2 in the direction from the coordinating functional group 62 toward the main chain 61. Therefore, in step S15, an attractive force is generated between the second ligand 52G coordinated to the green quantum dot 51G and the anode 41G. Therefore, in step S15, even if no attractive force is generated between the green quantum dot 51G and the anode 41G, the green quantum dot 51G is adsorbed to the green sub-pixel SPG.

[0111] Furthermore, repulsion occurs between the first ligand 52B and the anode 41G in step S12 and in step S15. Therefore, adsorption of quantum dots to sub-pixels emitting different colors can be reduced in steps S12 and S15.

[0112] Therefore, the blue light-emitting layer 45B and the green light-emitting layer 45G of the display device 1 can each be efficiently formed by electrophoretic deposition.

[0113] Furthermore, the first ligand 52B has an acidic group 63 that is negatively charged in solution, and the second ligand 52G has a basic group 64 that is positively charged in solution. Therefore, during the electrophoretic deposition process, even if the solvent in the solution in which the laminated body including the substrate 2 is immersed is polar, the first ligand 52B is more strongly adsorbed to the blue subpixel SPB than the solvent, and the second ligand 52G is more strongly adsorbed to the green subpixel SPG than the solvent. Therefore, with this configuration, the blue and green light-emitting layers 45B and 45G can each be formed by electrophoretic deposition with minimal incorporation of the solvent, thereby improving yield.

[0114] In particular, the first ligand 52B and the second ligand 52G have an acidic group 63 and a basic group 64, respectively, at one end of the main chain 61 opposite the coordinating functional group 62. This further separates the blue quantum dot 51B from the acidic group 63, and the green quantum dot 51G from the basic group 64. Consequently, during the electrophoretic deposition process, the attractive forces between the first ligand 52B and the second ligand 52G and the respective anodes 41 become stronger, further improving the yield of the blue light-emitting layer 45B and the green light-emitting layer 45G.

[0115] In this embodiment, the red light-emitting layer 45R includes a red quantum dot structure 5R, which includes red quantum dots 51R and a non-polar third ligand 52R coordinated with the red quantum dots 51R. Because the third ligand 52R is non-polar, it is difficult for the third ligand 52R to generate attractive and repulsive forces with each anode 41 during the electrophoretic deposition process. Therefore, the third ligand 52R reduces the red quantum dots 51R already stacked on the red sub-pixels SPR during the electrophoretic deposition process from escaping from the solution and flowing into other sub-pixels. As a result, the red light-emitting layer 45R reduces color mixing during the electrophoretic deposition process, improving the overall yield of the light-emitting layer 45.

[0116] In particular, the third ligand 52R is a neutral ligand that carries neither negative nor positive charge in the solution. Therefore, the third ligand 52R can further reduce the attractive and repulsive forces between the third ligand 52R and each anode 41 during the electrophoretic deposition process, thereby further reducing color mixing during the electrophoretic deposition process.

[0117] Generally, blue and green quantum dots tend to degrade more easily than red quantum dots. In particular, blue and green quantum dots tend to be less resistant to developing solutions or cleaning solutions used in lift-off methods, etc., than red quantum dots. In this embodiment, after forming the red light-emitting layer 45R by lift-off methods, the blue and green light-emitting layers 45B and 45G can be formed by electrophoretic deposition. Consequently, in this embodiment, degradation of the blue and green light-emitting layers 45B and 45G, which could occur during the formation of the red light-emitting layer 45R, can be reduced, thereby improving the yield of the light-emitting layer 45.

[0118] Furthermore, blue quantum dots generally tend to degrade more easily than green quantum dots. Therefore, in this embodiment, the step of forming green light-emitting layer 45G can be performed before the step of forming blue light-emitting layer 45B. In this case, steps S14 to S16 can be performed before steps S11 to S13. This manufacturing method can reduce the degradation of blue light-emitting layer 45B that may occur during the step of forming green light-emitting layer 45G, further improving the yield of light-emitting layer 45.

[0119] The display device 1 of this embodiment includes a high dielectric layer 44 located on the anode 41 side relative to the light emitting layer 45. Therefore, in steps S12 and S15, by applying a voltage to the anode 41, the high dielectric layer 44 is made ferroelectric, and each quantum dot is more efficiently adsorbed to each sub-pixel.

[0120] Therefore, the blue light-emitting layer 45B and the green light-emitting layer 45G of the display device 1 can each be efficiently formed by electrophoretic deposition.

[0121] The relative dielectric constant of high-dielectric layer 44 is higher than that of the lower side of high-dielectric layer 44. In other words, it is higher than the relative dielectric constants of the layers of light-emitting element 4 located on the substrate 2 side. Furthermore, it is also higher than the relative dielectric constant of banks BK. Therefore, during the electrophoretic deposition process, high-dielectric layer 44 is more strongly polarized than the layers and banks BK located closer to the substrate 2 side than high-dielectric layer 44, resulting in a more strongly charged upper surface. Consequently, during the electrophoretic deposition process, high-dielectric layer 44 more strongly attracts the quantum dots, improving the yield of light-emitting layer 45.

[0122] In particular, by making the relative dielectric constant of high-dielectric layer 44 higher than that of bank BK, high-dielectric layer 44 can further strengthen the attraction between itself and the quantum dots compared to the bank BK, thereby reducing the amount of quantum dots adhering to the bank BK. Therefore, with this configuration, high-dielectric layer 44 reduces the amount of quantum dots remaining on bank BK that face sub-pixels other than the sub-pixels to which the quantum dots are originally adsorbed. Consequently, with this configuration, high-dielectric layer 44 reduces color mixing in the light-emitting layer 45, improving the yield of the light-emitting layer 45.

[0123] In this embodiment, the relative dielectric constant of the high dielectric layer 44 is, for example, greater than 1.0. With this configuration, the high dielectric layer 44 more reliably adsorbs the quantum dots during the electrophoretic deposition process, thereby improving the yield of the light-emitting layer 45.

[0124] [Second embodiment] <Hydrophobic Layer> Reference Figure 9 The display device 8 of this embodiment will be described. Figure 9 A schematic side cross-sectional view of a display device 8 according to this embodiment is shown. Figure 1 The cross section of the display device 1 in the schematic side cross-sectional view 101 corresponds to the cross section of the display device 8. The display device 8 of this embodiment has the same structure as the display device 1 of the above embodiment, except that the high dielectric layer 44 of the light-emitting element 4 includes a hydrophobic layer 48 on the light-emitting layer 45 side.

[0125] The hydrophobic layer 48 is hydrophobic, particularly lyophobic to polar solvents such as water. Therefore, the surface 44S of the high dielectric layer 44 that contacts the light-emitting layer 45 is hydrophobic. The hydrophobic layer 48 can be made of a fluorine-based material such as silicon oxide or silicon nitride.

[0126] In addition, Figure 9 , the structure in which only the vicinity of surface 44S of high dielectric layer 44 on the side in contact with light-emitting layer 45 is formed as hydrophobic layer 48 is described. However, as long as surface 44S is hydrophobic, the specific structure is not limited to the above. For example, in this embodiment, high dielectric layer 44 contains a hydrophobic material in addition to a high dielectric constant material, so that the entire surface 44S including high dielectric layer 44 can also be hydrophobic.

[0127] The manufacturing method of the display device 8 of this embodiment can be performed as follows Figure 3 In the method for manufacturing the display device 8 of this embodiment, steps S1 to S6 may be the same as steps S1 to S6 in the method for manufacturing the display device 1 of the previous embodiment.

[0128] In step S7 of the method for manufacturing the display device 8 of this embodiment, for example, after coating a high dielectric constant material, a water-repellent material may be coated to form a high dielectric layer 44 having a hydrophobic layer 48. Alternatively, in step S7, for example, after forming the high dielectric layer 44, the upper surface of the high dielectric layer 44 may be modified to form the high dielectric layer 44 having the hydrophobic layer 48. Furthermore, in step S7, for example, a material obtained by coating a mixture of a high dielectric constant material and a hydrophobic material may be formed to form a high dielectric layer 44 having hydrophobicity throughout, including the surface 44S.

[0129] In step S8 of the method for manufacturing the display device 8 of this embodiment, the red light-emitting layer 45R is formed on the hydrophobic layer 48 of the high dielectric layer 44R. Therefore, in step S8, to improve the film-forming properties of the solution containing the red quantum dot structures 5R, the solvent of the solution may also include a non-polar solvent. In this case, even when the solution containing the red quantum dot structures 5R is formed into a film on the hydrophobic layer 48 in step S8, the solution easily wets and spreads onto the hydrophobic layer 48.

[0130] In the method for manufacturing the display device 8 of this embodiment, steps S9 and S10 may be respectively the same as steps S9 and S10 in the method for manufacturing the display device 1 of the previous embodiment.

[0131] In step S11 of the method for manufacturing the display device 8 of this embodiment, the hydrophobic layer 48 of the high dielectric layer 44G and the high dielectric layer 44B is exposed to the first solution 71. In this embodiment, since the first solution 71 contains the first polar solvent 72, it is difficult for the first solution 71 to wet and spread to the hydrophobic layer 48. However, in step S12, due to the above-mentioned voltage application, the blue quantum dot structure 5B is adsorbed on the high dielectric layer 44B, and thus the first solution 71 infiltrates and spreads to the hydrophobic layer 48 of the high dielectric layer 44B in step S12.

[0132] In this embodiment, in step S13, the various layers on substrate 2 can be cleaned while maintaining the aforementioned voltage application. Consequently, in step S13, first solution 71 can be easily rinsed from hydrophobic layer 48 of high dielectric layer 44G, where it has difficulty wetting and spreading, and blue quantum dot structures 5B are less likely to flow out of hydrophobic layer 48 of high dielectric layer 44B. Therefore, in this embodiment, contamination of blue quantum dot structures 5B into green light-emitting layer 45G can be reduced, and higher-quality blue light-emitting layer 45B can be formed, thereby improving the yield of light-emitting layer 45.

[0133] In step S14 of the method for manufacturing the display device 8 of this embodiment, the hydrophobic layer 48 of the high dielectric layer 44G is exposed to the second solution 73. In this embodiment, the second solution 73 contains the second polar solvent 74, so it is difficult for the second solution 73 to penetrate and diffuse into the hydrophobic layer 48. However, in step S15, due to the above-mentioned voltage application, the green quantum dot structure 5G is adsorbed on the high dielectric layer 44G, and thus the second solution 73 penetrates and diffuses into the hydrophobic layer 48 of the high dielectric layer 44G in step S15.

[0134] In this embodiment, in step S16, the above-mentioned voltage application can be maintained while cleaning the layers on the substrate 2. This prevents the green quantum dot structure 5G from flowing out of the hydrophobic layer 48 of the high dielectric layer 44G in step S16. Therefore, in this embodiment, a higher-quality green light-emitting layer 45G can be formed, improving the yield of the light-emitting layer 45.

[0135] In the method for manufacturing the display device 8 of this embodiment, step S17 and step S18 may be respectively the same as step S17 and step S18 in the method for manufacturing the display device 1 of the previous embodiment.

[0136] Display device 8 of this embodiment, like display device 1 of the previous embodiment, includes a blue light-emitting layer 45B having a blue quantum dot structure 5B, and a green light-emitting layer 45G having a green quantum dot structure 5G. Furthermore, display device 8 includes a high-dielectric layer 44 on the side of light-emitting layer 45 closer to substrate 2. Therefore, for the same reasons as described in the previous embodiment, both blue light-emitting layer 45B and green light-emitting layer 45G of display device 8 can be efficiently formed by electrophoretic deposition.

[0137] Furthermore, the display device 8 of this embodiment includes a hydrophobic layer 48 in the high dielectric layer 44, thereby imparting hydrophobicity to the surface 44S of the high dielectric layer 44 on the side in contact with the light-emitting layer 45. Therefore, during the electrophoretic deposition process, the display device 8 can reduce color mixing and form a higher-quality light-emitting layer 45, thereby enabling efficient formation of the light-emitting layer 45 by electrophoretic deposition.

[0138] The present disclosure is not limited to the above-described embodiments. Various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of the present disclosure. Moreover, new technical features can be formed by combining the technical means disclosed in the various embodiments. Description of Reference Numerals

[0139] 1, 8: display device; 2: Substrate; 4B: blue light-emitting element (first light-emitting element); 4G: green light emitting element (second light emitting element); 4R: red light-emitting element (third light-emitting element); 31: pixel circuit; 31B: pixel circuit (first pixel circuit); 31G: pixel circuit (second pixel circuit); 41: anode; 41B: anode (first electrode); 41G: anode (second electrode); 44: high dielectric layer; 44B: high dielectric layer (first high dielectric layer); 44G: high dielectric layer (second high dielectric layer); 45: luminescent layer; 45B: blue light-emitting layer (first light-emitting layer); 45G: green light-emitting layer (second light-emitting layer); 45R: red light-emitting layer (third light-emitting layer); 51B: blue quantum dots (first quantum dots); 51G: green quantum dots (second quantum dots); 51R: red quantum dot (third quantum dot); 52B: first ligand; 52G: second ligand; 52R: third ligand; 61: Main chain; 62: Coordinating functional group; 63: acidic group; 64: basic group; 71: first solution; 73: Second solution.

Claims

1. A display device, characterized in that: It has: substrate; and The first light emitting element and the second light emitting element on the substrate, The first light-emitting element has a first light-emitting layer, the first light-emitting layer includes a first quantum dot and a first ligand, the first ligand has a dipole moment in a direction from the main chain to the coordination functional group, The second light-emitting element has a second light-emitting layer, the second light-emitting layer includes second quantum dots and second ligands, and the second ligands have a dipole moment in a direction from a coordinating functional group to a main chain.

2. The display device according to claim 1, wherein The first ligand has an acidic group, and the second ligand has a basic group.

3. The display device according to claim 2, wherein: The first ligand has the acidic group at one end of the main chain opposite to the coordinating functional group, and the second ligand has the basic group at one end of the main chain opposite to the coordinating functional group.

4. The display device according to any one of claims 1 to 3, characterized in that The display device includes a third light-emitting element on a substrate, The third light-emitting element has a third light-emitting layer, and the third light-emitting layer includes third quantum dots and a third non-polar ligand.

5. The display device according to claim 4, wherein: The third ligand is neutral in polar solvents.

6. The display device according to claim 4 or 5, characterized in that One of the first quantum dot and the second quantum dot is a blue quantum dot, the other of the first quantum dot and the second quantum dot is a green quantum dot, and the third quantum dot is a red quantum dot.

7. A display device, characterized in that: It has: substrate; and A plurality of light-emitting elements on the substrate, The light emitting element has: a light-emitting layer comprising quantum dots; and A high dielectric layer is located on the substrate side relative to the light emitting layer.

8. The display device according to claim 7, wherein: The relative dielectric constant of the high dielectric layer is higher than the relative dielectric constant of each layer of the light emitting element located closer to the substrate than the high dielectric layer.

9. The display device according to claim 7 or 8, characterized in that The display device includes a bank on the substrate, the bank dividing the light emitting elements. The relative dielectric constant of the high dielectric layer is higher than the relative dielectric constant of the bank.

10. The display device according to any one of claims 7 to 9, characterized in that: The high dielectric layer includes at least one of silicon oxide, silicon nitride, and oxides of Group IV elements.

11. The display device according to any one of claims 7 to 10, characterized in that: The high dielectric constant of the high dielectric layer is greater than 1.

0.

12. The display device according to any one of claims 7 to 11, characterized in that The high dielectric layer is in contact with the light-emitting layer, and at least a surface of the side in contact with the light-emitting layer is hydrophobic.

13. A display device, characterized in that: It has: substrate; and The first light emitting element and the second light emitting element on the substrate, The first light emitting element has: a first light-emitting layer, the first light-emitting layer comprising a first quantum dot and a first ligand, the first ligand having a dipole moment in a direction from the main chain to the coordination functional group; and a first high dielectric layer, the first high dielectric layer being located on the substrate side relative to the first light-emitting layer; The second light emitting element has: a second light-emitting layer, the second light-emitting layer comprising second quantum dots and second ligands, the second ligands having a dipole moment in a direction from the coordination functional group to the main chain; as well as A second high dielectric layer is located on the substrate side relative to the second light-emitting layer.

14. A method for manufacturing a display device, characterized in that: The manufacturing method of the display device includes: Preparation of substrate; A first electrode and a second electrode are formed on the substrate; In a plan view of the substrate, a high dielectric layer is formed on the substrate, overlapping the first electrode and the second electrode respectively; Synthesis of a first solution, wherein the first solution comprises a first quantum dot and a first ligand, wherein the first ligand has a dipole moment in a direction from the main chain to the coordinating functional group; synthesizing a second solution, the second solution comprising a second quantum dot and a second ligand, the second ligand having a dipole moment in a direction from the coordinating functional group to the main chain; immersing the substrate having the high dielectric layer formed thereon in the first solution; applying a voltage to at least one of the first electrode and the second electrode of the substrate immersed in the first solution, so that the first quantum dots are adsorbed on the high dielectric layer overlapping the first electrode in a planar view of the substrate; immersing the substrate having the high dielectric layer formed thereon in the second solution; and By applying a voltage to at least one of the first electrode and the second electrode of the substrate immersed in the second solution, the second quantum dots are adsorbed on the high dielectric layer overlapping the second electrode in a planar view of the substrate.

15. The method for manufacturing a display device according to claim 14, wherein: comprising a first pixel circuit and a second pixel circuit, By forming the first electrode and the second electrode on the substrate, the first electrode is electrically connected to the first pixel circuit, and the second electrode is electrically connected to the second pixel circuit. During the adsorption of the first quantum dot and the second quantum dot, at least one of voltage application to the first electrode via voltage application to the first pixel circuit and voltage application to the second electrode via voltage application to the second pixel circuit is performed.

16. The method for manufacturing a display device according to claim 15, wherein: In at least one of the adsorption of the first quantum dot and the adsorption of the second quantum dot, the voltage applied to the first electrode is a reverse voltage with respect to the voltage applied to the second electrode.

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