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

Abstract

In the present invention, inkjet heads (51, 52) are arranged so that the trajectories of nozzle rows (1L, 2L) do not overlap, and so that an interval between a terminal nozzle (1N1) of the nozzle row (1L) of the inkjet head (51) and a terminal nozzle (2N1) on the inkjet head (51) side of the nozzle row (2L) of the inkjet head (52) is equal to an interval between the nozzles (1N, 2N) in each of the nozzle rows (1L, 2L). The inkjet heads perform simultaneous scanning to manufacture a hole injection layer 23 containing nanoparticles.

Description

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

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

[0002] Patent Document 1 describes a method for manufacturing a color filter, which includes the steps of (a) ejecting ink while relatively main-scanning an inkjet head unit and a substrate in a second direction that is approximately perpendicular to a row of nozzles arranged at uniform intervals in a first direction, and (b) sub-scanning the inkjet head unit and the substrate relatively a predetermined distance in the first direction, and coloring adjacent pixels in the second direction so that they are different colors.

[0003] Patent Document 2 describes a method for manufacturing a liquid crystal display device in which an inkjet head alternately performs a first movement along a first direction perpendicular to the row of inkjet nozzles and a second movement along a second direction parallel to the row, and the trajectories of the inkjet nozzles in the first movement before and after the second movement are partially overlapped, and the ink is ejected from the inkjet nozzles corresponding to each of the trajectories during the first movement.

[0004] Patent Document 3 describes an ink application device that memorizes malfunctioning nozzles, performs control so that the malfunctioning nozzle is not assigned to a pixel of an isolated pattern defined by an isolated pixel onto which ink is to land, and when at least one of a plurality of pixels that define the shape of a continuous pattern onto which ink is to land is assigned to the malfunctioning nozzle, performs control so that the malfunctioning nozzle is not assigned to two pixels that sandwich the pixel assigned to the malfunctioning nozzle in one direction, and ejects ink from each nozzle to form the isolated pattern and the continuous pattern.

[0005] Japanese Patent Publication No. 2007-263990 Japanese Patent Publication No. 2008-249936 Japanese Patent Publication No. 2021-137690

[0006] For example, the manufacturing methods described in Patent Documents 1 to 3 each control the trajectory of relative movement between an inkjet head and a substrate, thereby resolving unevenness and streaky defects in layers formed by the inkjet method. Patent Document 2, in particular, describes an inkjet method in which the trajectories of inkjet nozzles are overlapped when they move, and ink is ejected from only some of the inkjet nozzles along the overlapping trajectories. The manufacturing methods described in Patent Documents 1 to 3 have a problem in that, when a functional layer containing nanoparticles is formed, the surface roughness at the joints of the functional layer increases.

[0007] One aspect of the present disclosure has been developed in consideration of the above-mentioned problems, and its purpose is to provide a method for manufacturing a functional layer, and related technologies, that can reduce the surface roughness of a functional layer at the seams of the functional layer containing nanoparticles.

[0008] A method for manufacturing a functional layer according to one aspect of the present disclosure is a method for manufacturing a functional layer by ejecting ink containing nanoparticles from multiple inkjet heads onto a substrate having electrodes, wherein each of the multiple inkjet heads has at least one nozzle row in which multiple nozzles are arranged along a cross direction intersecting the scanning direction, and the first and second inkjet heads are arranged so that the trajectories of the nozzle rows of adjacent inkjet heads do not overlap, and the distance between the terminal nozzle in the nozzle row of a first inkjet head and the terminal nozzle on the first inkjet head side of the nozzle row of a second inkjet head adjacent to the first inkjet head is equal to the distance between the nozzles in each nozzle row, and the functional layer containing the nanoparticles is manufactured by scanning the first and second inkjet heads simultaneously.

[0009] Furthermore, 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 the functional layer between a first electrode and a second electrode, and includes the steps of performing a method for manufacturing a functional layer according to one aspect of the present disclosure using the electrode as a first electrode, forming the functional layer, forming a light-emitting layer on the functional layer, and forming the second electrode on the light-emitting layer, and the light-emitting layer contains quantum dots or an organic light-emitting compound.

[0010] Furthermore, a method for manufacturing a light-emitting element according to one aspect of the present disclosure produces a display device having a display area on the substrate in which a plurality of the light-emitting elements are formed by carrying out the method for manufacturing a light-emitting element according to one aspect of the present disclosure.

[0011] According to the present disclosure, an object is to provide a method for manufacturing a functional layer and related techniques that can reduce the surface roughness of a functional layer at the joints of the functional layer containing nanoparticles.

[0012] FIG. 1 is a diagram illustrating an outline of an inkjet head unit 50 for performing a method for manufacturing a functional layer and a method for manufacturing a light-emitting element according to one embodiment of the present disclosure. FIG. 2 is a diagram illustrating an outline of a process for forming a hole injection layer 23 on a substrate 13. FIG. 3 is a diagram illustrating an outline of a cross section of the hole injection layer 23 formed on the substrate 13. FIG. 4 is a diagram illustrating an outline of a process for forming a hole transport layer 24. FIG. 5 is a diagram illustrating an outline of cross sections of the hole injection layer 23 and the hole transport layer 24. FIG. 6 is an enlarged view of region 13a of the substrate 13 shown in FIG. 1. FIG. 7 is a diagram illustrating an outline of the hole injection layer 23 and the hole transport layer 24 formed within the bank 22 in region 13a of the substrate 13. FIG. 8 is a diagram illustrating an outline of a process for forming a pattern of a resist layer 70 on the hole transport layer 24. FIG. 9 is a diagram illustrating an outline of a process for developing the pattern on the resist layer 70. FIG. 10 is a diagram illustrating an outline of a process for forming a light-emitting layer 25R on the hole transport layer 24 exposed from the resist layer 70. FIG. 11 is a diagram illustrating an outline of a process for developing a pattern of light-emitting layer 25R on hole transport layer 24. FIG. 12 is a diagram illustrating an outline of a process for developing a pattern of light-emitting layer 25B on hole transport layer 24. FIG. 13 is a diagram illustrating an outline of a process for developing a pattern of light-emitting layer 25G on hole transport layer 24. FIG. 14 is a diagram illustrating an outline of light-emitting layers 25R, 25B, and 25G formed on hole transport layer 24. FIG. 15 is a diagram illustrating an outline of a process for forming electron transport layer 26. FIG. 16 is a diagram illustrating an outline of a process for forming cathode 27 on electron transport layer 26. FIG. 17 is a diagram illustrating an outline of light-emitting elements 20R, 20B, and 20G formed on substrate 13. FIG. 18 is a diagram illustrating an outline of a cross section of display device 100 including a plurality of light-emitting elements 20R, 20B, and 20G. FIG. 19 is a diagram illustrating an outline of display device 100 as viewed from above. Fig. 20 is a diagram illustrating an outline of a top view of the light emitting elements 20R, 20B, and 20G in the display area of ​​the display device 100. Fig. 21 is a diagram illustrating an outline of the inkjet head unit 60 used in the comparative sample.

[0013] <Method for manufacturing a functional layer and method for manufacturing a light-emitting element> A method for manufacturing a functional layer according to one aspect of the present disclosure is a method for manufacturing a functional layer containing nanoparticles on a substrate equipped with electrodes using an inkjet head unit equipped with multiple inkjet heads, and a method for manufacturing a light-emitting element according to one aspect of the present disclosure includes a functional layer manufacturing step in which the method for manufacturing the functional layer is performed.

[0014] Furthermore, a method for manufacturing a light-emitting element according to one aspect of the present disclosure includes a step of forming a light-emitting layer on a functional layer, and a step of forming the second electrode on the light-emitting layer, wherein the light-emitting layer contains quantum dots or an organic light-emitting compound.

[0015] The method also includes a step of forming an organic layer after the step of forming the functional layer and before the step of forming a light-emitting layer on the functional layer, and a step of forming a functional layer separate from the functional layer after the step of forming the light-emitting layer and before the step of forming the second electrode.

[0016] 1 is a diagram illustrating an outline of an inkjet head unit 50 for carrying out a method for manufacturing a functional layer and a method for manufacturing a light-emitting element according to one embodiment of the present disclosure. The inkjet head unit 50 includes inkjet heads 51 and 52, and forms a functional layer on a substrate 13. Each of the inkjet heads 51 and 52 has at least one nozzle row in which a plurality of nozzles are arranged along a cross direction (Y direction) intersecting the scanning direction (X direction).

[0017] The inkjet heads 51 and 52 are arranged so that the trajectories of the nozzles of the inkjet head 51 and the trajectories of the nozzles of the inkjet head 52 do not overlap in the scanning direction.

[0018] The inkjet heads 51 and 52 are preferably circulation type inkjet heads that supply ink containing nanoparticles from a circulation type tank (not shown) and circulate the ink within the inkjet heads 51 and 52. When the inkjet heads 51 and 52 are circulation type inkjet heads, the ink circulates to the vicinity of the nozzles and does not stagnate near the nozzles, preventing the nozzles 1N and 2N of the inkjet heads 51 and 52 from being clogged with nanoparticles.

[0019] 1 , by connecting inkjet heads 51 and 52 whose long sides are narrower than the short sides of the substrate 13 along the intersecting direction, ink can be ejected from the inkjet heads 51 and 52 along the two long sides of the substrate 13 over a width wider than the width of both ends of the short sides of the substrate 13. This makes it possible to form a functional layer over the entire surface of the substrate 13 in a single scan, for example, to generate a large display area. Furthermore, by connecting the inkjet heads 51 and 52 instead of increasing the size of the inkjet heads, it becomes possible to circulate ink independently through the inkjet heads 51 and 52 while simultaneously scanning the inkjet heads 51 and 52 relative to each other, thereby preventing a decrease in the dispersibility of nanoparticles contained in the ink.

[0020] The inkjet head (first inkjet head) 51 has n nozzle rows 1L (1L １ , 1L ２ ..., 1L n Here, each nozzle row 1L of the inkjet head 51 includes m nozzles 1N (1N １ , 1N ２ …, 1N ｍ Similarly, the inkjet head (first inkjet head) 52 includes n nozzle rows 2L (2L １ , 2L ２ ..., 2L n ), and each nozzle row 2L has m nozzles 2N (2N １ , 2N２ …, 2N ｍ ) is provided.

[0021] In the inkjet head unit 50, the inkjet head 51 has nozzles 1N (1N １ , 1N ２ …, 1N ｍ ) pitch P １ and the nozzles 2N (2N １ , 2N ２ …, 2N ｍ ) pitch P ２ are substantially equal. In addition, the odd-numbered nozzle rows 1L (1L １ Nozzle 1N located at the end of １ and the odd-numbered nozzle row 2L (2L １ Nozzle 2N located at the end of １ The pitch P between １ and P ２ The inkjet head 51 and the inkjet head 52 are preferably connected and fixed so that the amounts of ink containing nanoparticles ejected onto the substrate 13 from the inkjet head 51 and the inkjet head 52 are substantially equal to each other. This allows the inkjet head unit 50 to equalize the amounts of ink containing nanoparticles ejected onto the substrate 13 from the inkjet head 51 and the inkjet head 52. １ and the nozzle 2N of the inkjet head 52 １ This can prevent excessive lateral capillary force caused by the nanoparticles contained in the ink from acting at the joint of the functional layer formed by the trajectory of the ink.

[0022] In addition, the even-numbered nozzle row 1L of the inkjet head 51 ２ ... are arranged in odd-numbered nozzle rows 1L. １ ... are arranged at a pitch P １ Similarly, the even-numbered nozzle rows 2L of the inkjet head 52 may be arranged so that they are shifted by half the value of ２ ... are arranged in odd-numbered nozzle rows 2L １... is provided with a nozzle 2N, and P ２ The offset may be half of the value of the pixel shift, which provides the effect of forming a higher resolution image.

[0023] Pitch P between nozzles 1N arranged in a plurality of nozzle examples 1L １ and the pitch P between the nozzles 2N arranged in the plurality of nozzles 2L. ２ and the odd-numbered nozzle row 1L of the inkjet head 51. １ ... and nozzle row 1L １ The odd-numbered nozzle rows 2L of the inkjet head 52 corresponding to １ The pitch P is preferably 20 to 180 μm, and more preferably 23 to 72 μm.

[0024] The inkjet heads 51 and 52 each preferably have a total number of nozzles of 500 to 2,000, calculated by multiplying the number of nozzle rows n by the number of nozzles m. This provides the effect of forming a higher resolution image in a short time. The nozzle diameter is preferably 20 to 50 μm, and more preferably 30 to 40 μm. The pitch P between the nozzles 1N is １ , the pitch P between the nozzles 2N ２ are essentially equal.

[0025] The ink ejection amount of the inkjet heads 51 and 52 and the scanning speed of the inkjet heads 51 and 52 may be appropriately designed depending on the type of ink and the thickness of the functional layer and / or organic layer formed by the ink.

[0026] [Step of forming hole injection layer (functional layer) 24] The step of forming the hole injection layer 23 will be described with reference to Figures 2 and 3. Figure 2 is a diagram illustrating an outline of the step of forming the hole injection layer 23 on the substrate 13, and Figure 3 is a diagram illustrating an outline of the cross section of the hole injection layer 23 formed on the substrate 13. The hole injection layer 23 is a layer formed from ink containing nanoparticles.

[0027] (Ink Containing Nanoparticles) The ink containing nanoparticles contains nanoparticles and a dispersion solvent for the nanoparticles, and may contain additives within the range that does not impair the effects of the present disclosure.

[0028] The ink containing nanoparticles contains a material having hole injection ability, and the nanoparticles having hole injection properties may be inorganic nanoparticles, such as 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 injection material is at least one selected from O, and further preferable that the hole injection material is NiO or MgO. Further, preferable hole injection materials include materials in which a CN group, an SCN group, and an SeCN group are bonded to a metal, such as CuSCN.

[0029] The median diameter of the nanoparticles having hole injection ability is 0.5 to 100 nm, preferably 1 to 40 nm, and more preferably 1 to 10 nm. Having the median diameter in 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 (Microtrac-Bell, Nanotrac Wave II).

[0030] The ink containing nanoparticles having hole injection ability preferably contains 0.5 to 10.0 wt % of nanoparticles, and more preferably 1.0 to 5.0 wt % of nanoparticles, based on 100 wt % of the total of the inorganic nanoparticles and the dispersion solvent.

[0031] Ink containing nanoparticles can use organic solvents as dispersion solvents for the nanoparticles, such as polyhydric alcohols such as propylene glycol and ethylene glycolicol, polyhydric alcohol ethers such as diethylene glycol, diethylene glycol monomethyl ether, and propylene glycol monomethyl ether, and polyhydric alcohol esters such as propylene glycol monomethyl ether acetate (PGMEA) and poly(ethylene glycol) methacrylate. The use of organic solvents having hydroxyl groups, ester groups, and / or carbonyl groups in their molecular structure, such as these polyhydric alcohols and polyhydric alcohol esters, has the effect of enhancing the dispersibility of the nanoparticles.

[0032] The ink containing nanoparticles may contain additives such as dispersants exemplified by amines and thiols, and ligands to inhibit aggregation of the nanoparticles.

[0033] In the process of forming the hole injection layer 23, after applying ink containing nanoparticles by the inkjet head unit 50, for example, 10 －１ ~10 －３ The hole injection layer 23 formed on the substrate may be dried by vacuum drying under Pa and / or by heating and drying at a temperature of 120 to 200°C.

[0034] 2, in the step of forming the hole injection layer 23 according to one embodiment, ink containing nanoparticles is applied onto the substrate 13 while the inkjet heads 51 and 52 are scanned along a scanning direction parallel to the long side direction of the substrate 13. In this way, the hole injection layer 23 is formed over the entire surface of the substrate 13 in one scan. At this time, the odd-numbered nozzle rows 1L of the inkjet head 51 are aligned along the scanning direction of the inkjet head unit 50. １ ... and the nozzle row 1L １ The odd-numbered nozzle rows 2L of the inkjet head 52 corresponding to １ A locus E passing through the midpoint between １ 3, in the cross section of the hole injection layer 23 formed on the substrate 13, a seam of the functional layer containing nanoparticles may occur along a locus E １The nanoparticle-containing ink is injected into each nozzle 1N of the inkjet head 51. １ Pitch P １ and each nozzle 2N of the inkjet head 52 １ Pitch P ２ And, Locus E １ The nozzle 1N at the end passing near １ and 2N １ By making the pitch P of the ink droplets equal, it is possible to prevent the lateral capillary force caused by the nanoparticles contained in the ink from acting excessively at the joint 23a between the hole injection layer 23 formed by the inkjet head 51 and the hole injection layer 23 formed by the inkjet head 52. This makes it possible to reduce the surface roughness of the joint 23a in the hole injection layer 23.

[0035] The hole injection layer 23 formed of inorganic nanoparticles having hole injection capability is a functional layer that has the function of injecting holes from the anode 21 provided on the substrate 13 to the hole transport layer 24 or the light-emitting layer 25, which will be 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 or the light-emitting layer 25, which will be described later, to the anode 21.

[0036] 3 and 4, a manufacturing process of the hole transport layer 24 included in the manufacturing method of the light-emitting element according to one embodiment of the present disclosure will be described. Fig. 3 is a diagram illustrating an outline of the process of forming the hole transport layer 24 on the hole injection layer 23, and Fig. 4 is a diagram illustrating an outline of a cross section of the hole transport layer 24 formed on the hole injection layer 23. The hole transport layer 24 is a layer formed from ink containing an organic compound having hole transport ability.

[0037] (Ink containing organic compound) The ink containing an organic compound contains an organic compound having hole transport ability and a dispersion solvent for the organic compound, and may contain additives within a range that does not impair the effects of the present disclosure. Furthermore, the ink containing an organic compound may contain nanoparticles having the above-mentioned hole injection property.

[0038] The hole transport layer (organic layer) 24 is a layer formed from ink containing an organic compound as a material having hole transport properties. Examples of organic compounds having hole transport properties for forming the hole transport layer 24 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 a suitable mixture of two or more types. A hole injection layer (not shown) may also be formed. Examples include a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (abbreviated as "PEDOT:PSS"), NiO (nickel oxide), and CuSCN (copper thiocyanate). These materials may be used alone or in a suitable mixture of two or more types.

[0039] The ink containing an organic compound having hole transport properties preferably contains 0.5 to 10.0 wt % of the organic compound, and more preferably 1.0 to 5.0 wt % of the organic compound, with the total of the organic compound and the dispersion solvent being 100 wt %.

[0040] Inks containing organic compounds with hole transport properties can use organic solvents as dispersion solvents, such as polyhydric alcohols such as propylene glycol and ethylene glycolic acid, polyhydric alcohol ethers such as diethylene glycol, diethylene glycol monomethyl ether, and propylene glycol monomethyl ether, polyhydric alcohol esters such as propylene glycol monomethyl ether acetate, hydrocarbon solvents such as tetradecane, and aliphatic alcohols such as octanol.

[0041] The ink containing the organic compound having hole transport properties may contain an additive such as a surfactant.

[0042] In the process of forming the hole transport layer 24, after applying ink containing nanoparticles by the inkjet head unit 50, for example, 10 －１ ~10 －３ The hole injection layer 23 formed on the substrate may be dried by vacuum drying under Pa and / or by heating and drying at a temperature of 120 to 200°C.

[0043] As shown in FIG. 4, in the process of forming the hole transport layer 24, the trajectory E of the joint 23a of the hole injection layer 23 formed by ejecting ink containing nanoparticles from the inkjet heads 51 and 52 is １ 5, the trajectories of the inkjet heads 51 and 52 are preferably shifted parallel to the scanning direction. At this time, as shown in FIG. 5, the trajectories E of the joint 24a of the hole transport layer 24 formed by ejecting ink containing an organic compound having hole transport properties are ２ And, Locus E １ Width W Ｅ１ However, it is preferable to scan the inkjet heads 51 and 52 so that they are spaced apart from each other by 0.7 mm or more, and it is more preferable to scan the inkjet heads 51 and 52 so that they are spaced apart from each other by 1 mm or more. １ In this case, it is possible to prevent the joint 23 a of the hole injection layer 23 from overlapping the joint 24 a of the hole transport layer 24. １ Therefore, it is possible to prevent the hole injection layer 23 and the hole transport layer 24 from being formed too thick.

[0044] 6 shows an enlarged view of region 13a of substrate 13 shown in FIG. 1 , and FIG. 7 shows the hole injection layer 23 and hole transport layer 24 formed on region 13a of substrate 13. As shown in FIG. 6 , anodes 21R, 21G, and 21B, which are first electrodes, and banks (partition walls) 22 are formed on substrate 13. Here, by performing the above-described step of forming the hole injection layer 23 and the step of forming the hole transport layer 24, the hole injection layer 23 and the hole transport layer 24 are formed so as to cover the anodes 21R, 21G, and 21B and the banks (partition walls) 22, as shown in FIG. 7 . As already described, in the method for manufacturing a light-emitting element according to one aspect of the present disclosure, the hole injection layer 23 is formed so as to reduce the surface roughness of the joints 23a of the hole injection layer 23. Therefore, due to the formation of the joints 23a of the hole injection layer 23, the ink containing nanoparticles does not follow the locus E １ In addition, since the hole injection layer 23 and the hole transport layer 24 are formed so that the joint 23 a of the hole injection layer 23 and the joint 24 a of the hole transport layer 24 do not overlap, the hole injection layer 23 is prevented from flowing excessively onto the anodes 21R, 21G, and 21B in the bank 22 located below the joint 23 a. １ This prevents the ink containing the organic compound having hole transport properties from flowing excessively onto the anodes 21R, 21G, and 21B in the bank 22 located below the anodes 21R, 21G, and 21B. This reduces variations in the thickness of the hole injection layer 23 and the hole transport layer 24 that occur due to the trajectories of the inkjet heads 51 and 52 along the scanning direction.

[0045] The thickness of the hole injection layer 23 is preferably 40 nm or more at its thinnest portion and 80 nm or less at its thickest portion, thereby suppressing an increase in the driving voltage of the light-emitting element while improving the hole injection property of the hole injection layer 23. Furthermore, the thickness of the hole transport layer 24 is preferably 40 nm or more at its thinnest portion and 80 nm or less at its thickest portion, thereby suppressing an increase in the driving voltage of the light-emitting element while improving the hole transport property of the hole transport layer 24. According to one aspect of the method for manufacturing a functional layer and a method for manufacturing a light-emitting element, it is possible to reduce variations in the thickness of the hole injection layer 23 and the hole transport layer 24, which cause an increase in the driving voltage.

[0046] 6, anodes 21 including 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 are formed on the substrate 13. The anodes 21 are provided in an island shape for each sub-pixel on the substrate 13, and are also referred to as "pixel electrodes."

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] As shown in FIG. 6 , the bank (partition wall) 22 surrounds the anodes 21R, 21B, and 21G. The bank 22 simply divides the anodes 21R, 21B, and 21G provided on the substrate 13 in top view and insulates 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."

[0053] 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.

[0054] 6, 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.

[0055] 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 W Ａ２ 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.

[0056] 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.

[0057] 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.

[0058] In the top view of FIG. 6 , 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. Alternatively, 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.

[0059] 8 to 14, a process for forming the light-emitting layers 25 (25R, 25B, and 25G) included in the method for manufacturing a light-emitting element according to one embodiment of the present disclosure will be described. The process for forming the light-emitting layers 25R, 25B, and 25G may be performed by lift-off patterning.

[0060] 8 , a method for manufacturing a light-emitting device according to one embodiment of the present disclosure includes a step of forming a pattern of a resist layer 70 on the hole transport layer 24. The resist composition for forming the resist layer 70 may be a positive resist composition or a negative resist composition, but is preferably a positive resist composition.

[0061] The step of forming a pattern of the resist layer 70 on the hole transport layer 24 includes a step of applying a resist agent composition for forming the resist layer 70 onto the hole transport layer 24, and a step of exposing the resist layer 70 formed by applying the resist agent composition onto the hole transport layer 24 through a photomask 300 having a predetermined pattern. After the step of applying the resist agent composition and before the step of exposing the resist layer 70, it is preferable to remove the solvent contained in the resist layer 70 by heating and / or vacuum drying the resist layer 70.

[0062] FIG. 9 is a diagram illustrating an outline of the process of washing the resist layer 70 with a developer and developing a pattern in the resist layer 70. The resist layer 70 has increased solubility in an alkaline aqueous developer at exposed locations. Therefore, a desired pattern can be developed in the resist layer 70 by washing with the alkaline aqueous developer. The desired pattern can be developed by immersing the resist layer 70 in, for example, a beaker (not shown) containing the developer. The developer can be supplied to the resist layer 70 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.

[0063] The resist layer 70 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 70 may be formed by heating and / or vacuum drying the resist composition applied to the hole injection layer 23 (pre-baking).

[0064] As shown in FIG. 10 , a method for manufacturing a light-emitting element according to one embodiment of the present disclosure includes a step of forming a resist layer 70 having a predetermined pattern and a light-emitting layer 25R on the hole transport layer 24 exposed from the resist layer 70.

[0065] 11 , the method for manufacturing a light-emitting element according to one embodiment of the present disclosure includes a step of removing the resist layer 70 with a stripping solvent after forming the light-emitting layer 25R. In the step of removing the resist layer 70 with a stripping solvent, the substrate on which the light-emitting layer 25R has been formed is washed with the stripping solvent, so that the light-emitting layer 25R formed on the resist layer 70 is stripped and removed together with the resist layer 70. As a result, the pattern of the light-emitting layer 25R is developed so that the light-emitting layer 25 remains on the hole transport layer 24.

[0066] 12 , in a method for manufacturing a light-emitting element according to an embodiment of the present disclosure, after forming the light-emitting layer 25R, a resist layer 70 is formed and exposed to light, and the light-emitting layer 25B is formed. Thereafter, the resist layer 70 is removed with a stripping solvent, and a pattern of the light-emitting layer 25B is developed on the hole transport layer 24.

[0067] 13 , in a method for manufacturing a light-emitting element according to an embodiment of the present disclosure, after forming patterns of light-emitting layers 25R and 25B, a resist layer 70 is formed and exposed to light, and a light-emitting layer 25G is formed. The resist layer 70 is then removed with a stripping solvent, thereby developing a pattern of light-emitting layer 25G on the hole transport layer 24. As a result, as shown in FIG. 14 , patterns of light-emitting layers 25R, 25B, and 25G are formed on the hole transport layer 24 formed over the entire substrate 13, including region 13 a.

[0068] 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.

[0069] The light-emitting layer 25 is a layer in which light emitters are excited by recombination of holes from the anode 21 with electrons from the cathode 27 (described later), and emits light when the excited light emitters return to their ground state. Recombination occurs in the light-emitting layer 25 by applying a voltage or current between the anode 21 and the cathode 27, resulting in light emission. The light-emitting layer 25 contains quantum dots as light emitters.

[0070] 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 solvent. The dispersion liquid containing quantum dots may also contain a constituent material of the matrix material.

[0071] The dispersion liquid containing quantum dots may contain, for example, a hydrocarbon-based solvent as a dispersion solvent. Examples of hydrocarbon-based solvents include aliphatic hydrocarbons such as hexane, cyclohexane, octane, and decane, and aromatic hydrocarbons such as toluene and xylene.

[0072] The light-emitting layer 25 may be formed by applying a dispersion liquid containing quantum dots onto the resist layer 70 and onto the hole transport layer 24 exposed from the pattern of the resist layer 70, using 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] The III-V compound includes, for example, at least one selected from the group consisting of GaAs, GaP, InN, InAs, InP, and InSb.

[0077] Chalcogenides are compounds containing a Group VI A(16) element, such as CdS or CdSe. Chalcogenides may also include mixed crystals thereof.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 composition of the actual compounds is as shown in the chemical formulas, but they do not necessarily have to be stoichiometric.

[0085] The dispersion liquid containing quantum dots may contain, for example, a hydrocarbon-based solvent as a dispersion solvent. Examples of hydrocarbon-based solvents include aliphatic hydrocarbons such as hexane, cyclohexane, octane, and decane, and aromatic hydrocarbons such as toluene and xylene.

[0086] All light-emitting layers, including the light-emitting layers 25R, 25B, and 25G described above, emit light by recombination of holes transported from the anode 21 and electrons transported from the cathode 27 (described later). In one embodiment, each light-emitting layer is a quantum dot light-emitting layer that includes quantum dots (QDs: semiconductor nanoparticles) of different colors as a light-emitting material. However, the present invention is not limited to this. In one embodiment, a light-emitting layer that includes an organic light-emitting compound as an OLED (organic light-emitting diode) may be formed. The light-emitting layer containing the organic light-emitting compound may be formed by a known vapor deposition method or inkjet coating method.

[0087] [3] Step of Forming Another Functional Layer A method for manufacturing a light-emitting element according to one aspect of the present disclosure includes a step of forming an electron transport layer (another functional layer) 26 on the light-emitting layer 25. The electron transport layer 26 may be formed by scanning inkjet heads 51 and 52 over the substrate 13 on which the light-emitting layer 25 has been formed, and ejecting an ink containing another nanoparticle.

[0088] The ink containing nanoparticles may contain nanoparticles other than the nanoparticles having hole injection capability, and the other nanoparticles may be nanoparticles having electron transport capability. The ink containing the other nanoparticles contains nanoparticles having electron transport capability and a dispersion solvent, and may also contain additives to the extent that the effects of the present disclosure are not impaired.

[0089] The electron transport material contained in the ink used to form the electron transport layer 26 is not particularly limited as long as it is an electron transport material that can stabilize the transport of electrons to the light-emitting layer, and examples thereof include ZnO, ZnS, ZrO, MgZnO, AlZnO, and TiO. ２ These nanoparticles may have ligands, such as organic ligands and inorganic ligands, on their surfaces.

[0090] The dispersion solvent and additives contained in the ink containing nanoparticles having electron transport capability can be the same as those used in the ink containing nanoparticles having hole injection capability, and therefore a description thereof will be omitted. Furthermore, the drying conditions for the electron transport layer 26 by vacuum decompression or heating in the step of forming the electron transport layer 26 as another functional layer are the same as the drying conditions in the step of forming the hole injection layer 23, and therefore a description thereof will be omitted.

[0091] 15 is a diagram illustrating an outline of the process of forming the electron transport layer 26 on the substrate 13 by the inkjet heads 51 and 52. In the process of forming the electron transport layer 26, the electron transport layer 26 is formed so as to cover the light-emitting layers 25R, 25B, and 25G. Here, the ink containing nanoparticles is injected from each nozzle 1N of the inkjet head 51. １ Pitch P １ and each nozzle 2N of the inkjet head 52 １ Pitch P ２ And, Locus E １ The nozzle 1N at the end passing nearby １ and 2N １ By making the pitch P of the electron transport layer 26 equal, it is possible to prevent excessive lateral capillary force caused by nanoparticles contained in the ink from acting at the joint 26a between the electron transport layer 26 formed by the inkjet head 51 and the electron transport layer 26 formed by the inkjet head 52. This makes it possible to reduce the surface roughness of the joint 26a of the electron transport layer 26. In addition, due to the formation of the joint 26a of the electron transport layer 26, the locus E ３ This can prevent the ink containing nanoparticles having electron transport properties from flowing excessively onto the anodes 21R, 21G, and 21B in the bank 22 located below the anodes 21R, 21G, and 21B.

[0092] 15, in the process of forming the electron transport layer 26, the inkjet heads 51 and 52 are used to form a locus E of the joint 23a of the hole injection layer 23. １ and the locus E of the joint 24 a of the hole transport layer 24 ２ In this case, the trajectories of the inkjet heads 51 and 52 are shifted parallel to the scanning direction. １ and a locus E where the joint 24 a of the hole transport layer 24 is formed. ２ The inkjet heads 51 and 52 are preferably scanned so that the distance between the locus E and the seam of the electron transport layer 26 is 0.7 mm or more, and more preferably so that the distance between the locus E and the seam of the electron transport layer 26 is 1 mm or more. １ The joint 23 a of the hole injection layer 23 and the joint 26 a of the electron transport layer 26 overlap each other on the surface of the hole injection layer 23 , and the locus E ２ Therefore, the joint 24 a of the hole transport layer 24 and the joint 26 a of the electron transport layer 26 do not overlap with each other. １ , E ２ and E ３ As a result, variations in the thickness of the hole injection layer 23 , the hole transport layer 24 , and the electron transport layer 26 formed on the substrate 13 can be dispersed.

[0093] The electron transport layer 26 may be formed from a plurality of electron transport layers, and one of the plurality of electron transport layers may be a layer (another organic layer) formed from an ink containing an organic compound as a material having electron transport ability.

[0094] When the electron transport layer 26 contains an organic compound as a material having electron transport properties, examples of the organic compound having electron transport properties include compounds or 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. 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, and nitrogen-containing heterocyclic compounds such as bathophenanthroline, bathocuproine, 2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), and triazine derivatives.

[0095] In addition, examples of electron transport materials suitable for the electron transport layer include compounds having a paraphenylene vinylene skeleton, such as polyparaphenylene vinylene (PPV) compounds such as poly(2-2'-ethyl-hexoxy)-5-methoxy-1,4-phenylene vinylene (POPh-PPV).

[0096] The thickness of the other electron transport layer is preferably 10 nm or more at its thinnest portion and 100 nm or less at its thickest portion, which can enhance the electron transport properties of the electron transport layer 26 while suppressing an increase in the driving voltage of the light-emitting element.

[0097] 16, a method for manufacturing a light-emitting device according to one embodiment of the present disclosure includes a step of forming a cathode 27, which is a second electrode, on an electron transport layer 26. The cathode 27 shown in FIG. 16 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 transparent electrode. The transparent electrode can be formed from a light-transmitting conductive material.

[0098] 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.

[0099] As a result of the above, the light emitting elements 20R, 20B, and 20G are formed on the substrate 13 as shown in FIG.

[0100] The above describes a method for manufacturing a light-emitting element in which, in order from the anode (first electrode) side provided on a substrate, a hole injection layer (a functional layer containing nanoparticles), a hole transport layer (an organic layer), a light-emitting layer (a layer containing quantum dots or an organic light-emitting compound), and an electron transport layer (a layer containing another nanoparticle) are stacked, and a cathode (a second electrode) is provided on the electron transport layer. The method for manufacturing a light-emitting element according to one embodiment is not limited to manufacturing a light-emitting element having a forward stack structure, but may also manufacture a light-emitting element having an inverted stack structure. In a method for manufacturing a light-emitting element having a forward stack structure, a cathode provided on a substrate serves as a first electrode, and, in order from the cathode side, an electron transport layer (a functional layer containing nanoparticles), a light-emitting layer, a hole transport layer (an organic layer), and a hole injection layer (a functional layer containing another nanoparticle) are stacked, and an anode may be provided on the hole injection layer as a second electrode.

[0101] In one embodiment of the method for manufacturing a light-emitting element, the anode and the cathode are formed from a transparent electrode material or a reflective electrode material, thereby making it possible to manufacture, for example, a top-emission light-emitting element and a bottom-emission light-emitting element. When manufacturing a top-emission light-emitting element, it is preferable to form the first electrode as an anode and the second electrode as a cathode, and in a bottom-emission light-emitting element, it is preferable to form the first electrode as a cathode and the second electrode as an anode.

[0102] A method for manufacturing a light-emitting device according to an aspect of the present disclosure may include a step of forming a sealing layer 30 on the cathode 27 (FIG. 18).

[0103] [Display device 100] Figure 18 is a diagram illustrating an outline of a cross section of a display device 100 having a plurality of light-emitting elements 20R, 20B, and 20G, Figure 19 is a diagram illustrating an outline of the display device 100 as viewed from above, and Figure 20 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.

[0104] 18 , the sealing layer 30 covers the light-emitting elements 20R, 20B, and 20G and the bank 22 to seal the light-emitting elements. The sealing layer 30 reduces the penetration of foreign matter, including moisture, into the light-emitting layer, the electron transport layer, and the like, from outside the sealing layer side of the light-emitting element. The sealing layer 30 may have a three-layer laminate structure including, for example, an inorganic sealing film made of an inorganic material provided on the cathode 27, an organic sealing film made of an organic material provided on the inorganic sealing film, and another inorganic sealing film made of an inorganic material provided on the organic sealing film.

[0105] As shown in Figure 18, the substrate 13 is a substrate including a transistor TR (also called a thin film transistor layer), and is provided with a barrier layer 12 and a substrate 13 including a transistor TR on a support substrate 11, in this order from the support substrate 11 side.The substrate on which a plurality of anodes 21 (i.e., anodes 21R, 21G, and 21B) are provided is referred to as a substrate (active matrix substrate) 10 including anodes 21.

[0106] The support substrate 11 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 support substrate 11 will be described as an example, but the present invention is not limited to this.

[0107] 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.

[0108] The transistor TR portion of the substrate 13 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 substrate 13 other than the transistor TR portion including the transistor TR includes the inorganic insulating film 131, the inorganic insulating film 132, the inorganic insulating film 133, and the planarization film 134.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] The planarization film 134 can be made of a coatable organic material such as polyimide or acrylic.

[0113] 19 , display device 100 according to the present disclosure includes a display area DA that performs display by extracting light from light-emitting elements 20, and a frame area NA that surrounds the periphery of display area DA. In frame area NA, terminals (not shown) are formed to input signals for driving light-emitting elements of display device 100.

[0114] Fig. 20 corresponds to an enlarged top view of one pixel PIX shown in Fig. 19. As shown in Fig. 20, the display device 100 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 form a sub-pixel within one pixel PIX shown in Fig. 19. Here, one pixel PIX corresponds to the region 13a of the substrate 13 described above.

[0115] According to the method for manufacturing a light-emitting element according to one aspect of the present disclosure, it is possible to reduce the variation in the thickness of the hole injection layer 23 containing nanoparticles and the variation in the thickness of the electron transport layer 26 containing another nanoparticle. Furthermore, the variation in the thickness of the hole injection layer 23 and the variation in the thickness of the hole transport layer 24 can be dispersed within the display area of ​​the display device 100, thereby suppressing an increase in the drive voltage of the light-emitting elements 20R, 20B, and 20G caused by the variation in the thickness of these layers. Therefore, the scope of the present disclosure also includes a method for manufacturing a display device 100 including the light-emitting elements 20R, 20B, and 20G formed by the method for manufacturing a light-emitting element according to one aspect of the present disclosure.

[0116] Although the above describes a method for manufacturing a functional layer and a method for manufacturing a light-emitting element according to one embodiment using the inkjet head unit 50 including two inkjet heads 51 and 52, the number of inkjet heads in the inkjet head unit may be increased depending on the size of the substrate. By arranging the inkjet heads so that the spacing between the terminal nozzles of the inkjet heads is equal to the spacing between the nozzles in each nozzle row, it is possible to form a functional layer on the substrate in a single scan according to the size of the substrate while reducing the size of the functional layer containing nanoparticles ejected from each inkjet head.

[0117] 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.

[0118] [1] Preparation of Substrate A substrate equipped with electrodes for forming a hole injection layer, a hole transport layer, and an electron transport layer was prepared. An Ag / ITO anode (first electrode) and a bank were patterned on the top surface of a glass substrate measuring 290 mm long x 109 mm, to prepare a substrate for manufacturing a light-emitting element. The bank pattern had an opening that opened to the top 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 approximately 100 μm, and a horizontal width of approximately 30 μm, and a density of 14,700 / cm per unit area. ２ An opening was formed.

[0119] [2] Fabrication of Hole Injection Layer [Sample 1] An ink for a hole injection layer was prepared using NiO nanoparticles as the hole injection material, containing 2 wt. % of the nanoparticles, and using ethylene glycol monomethyl ether acetate (PGMEA) as a dispersion solvent. The ink for the hole injection layer was then applied to a glass substrate on which an anode and a bank had been formed as described in section [1] above, using an inkjet head unit 50 having a nozzle array conforming to FIG. 1 . Inkjet head unit 50: Number of inkjet heads: 2; Number of nozzles in each inkjet head: 2,000; Distance between nozzles at the ends of inkjet heads: 35 μm; Distance between nozzles within the nozzle array of inkjet heads: 35 μm; No overlap between inkjet head tracks; Application pitch: 35 μm; Scanning speed of inkjet head unit: 50 mm / s; Number of scans of inkjet head unit: 1; Minimum liquid dispense volume: 6 pL

[0120] After applying the ink for the hole injection layer using the inkjet head unit-1, the ink was dried in a vacuum oven for 10 minutes. －１ After drying under reduced pressure at 200° C. for 20 minutes, the coating was dried by heating to form a hole injection layer having a thickness of 50 μm on the glass substrate (Sample 1).

[0121] [Sample 2] The same hole injection layer ink as used in Sample 1 was prepared, and then the hole injection layer ink was applied to a glass substrate on which an anode and a bank had been formed as described in section [1] above using an inkjet head unit 60 having a nozzle array and nozzles as shown in Figure 21, and dried by heating, to form the hole injection layer of Sample 2. Inkjet head unit 60 - Number of inkjet heads: 2 - Number of nozzles in each inkjet head: 2,000 - Overlap of trajectories between inkjet heads: 315 mm (equivalent to 10 nozzles) - Distance between nozzles in the inkjet head nozzle array: 35 μm - Coating pitch (non-overlapping areas): 35 μm - Coating pitch (overlapping areas): 70 (35 + 35) μm In one nozzle array, nozzles that ejected ink and nozzles that did not eject ink were arranged alternately, and the coating pitch was set to 70 μm for overlapping areas. Scanning speed of inkjet head unit: 50 mm / s Number of scans of inkjet head unit: 1 Minimum droplet amount: 6 pL Note that nozzle 1N shown in white in FIG. 21 ２ , 2N ２ are nozzles that do not eject ink.

[0122] [Evaluation of Surface Condition (1)] The root mean square (RMS) surface roughness and the maximum in-plane height difference (Rmax) were measured at the joints of the inkjet heads of the hole injection layer of Sample 1 and the hole injection layer of Sample 2. The root mean square (RMS) surface roughness and the maximum in-plane height difference (Rmax) were evaluated using an atomic force microscope (manufactured by Bruker Japan). The width of the irregularities was evaluated using an atomic force microscope, measuring the area near the center of the two heads, and was evaluated as the width of the range in which the root mean square (RMS) surface roughness was 0.3 nm or more. The width of the irregularities was evaluated based on the following criteria: ○: The width of the irregularities was less than 0.2 mm. ×: The width of the irregularities was 0.2 mm or more.

[0123] Table 1 below shows the evaluation results of the surface roughness and the width of the irregularities in the hole injection layer of Sample 1 and the hole injection layer of Sample 2.

[0124] From the evaluation results shown in Table 1, it can be seen that the width of the uneven portion at the joint of the inkjet head, as well as the surface roughness and the maximum in-plane height difference of the hole injection layer of Sample 1 are all one order of magnitude smaller than those of the hole injection layer of Sample 2.

[0125] [3] Formation of Hole Transport Layer [Sample 3] An ink for a hole transport layer was prepared using TFB as the hole transport material and dichlorobenzene as the dispersion solvent. Next, inkjet head unit-1 and Sample 1 were positioned so that the trajectory of inkjet head unit-1 was shifted by 1 mm from the trajectory used when the hole injection layer was formed, and the ink for a hole transport layer was applied onto the hole injection layer of Sample 1. This was then heated and dried at 200°C for 30 minutes to form a hole transport layer with a thickness of 30 μm, yielding a substrate equipped with a hole injection layer and a hole transport layer. The application conditions for the ink for a hole transport layer using inkjet head unit-1 were as follows: Trajectory shift of inkjet head unit-1: 1 mm Scanning speed of inkjet head unit: 50 mm / s Number of scans of inkjet head unit: 1 Minimum droplet volume: 6 pL

[0126] Note that by shifting the trajectory of inkjet head unit-1 by 1 mm, the trajectories of 28 nozzles are shifted along the direction perpendicular to the scanning direction.

[0127] [Sample 4] The same ink for the hole transport layer as used in Sample 3 was prepared. Next, using this ink, the ink for the hole transport layer was applied onto the hole injection layer of Sample 1 under the same conditions as Sample 3, except that inkjet head unit-1 and Sample 1 were positioned so that the trajectory of inkjet head unit-1 was shifted by 0.5 mm from the trajectory when the hole injection layer was formed. Thereafter, the ink was dried by heating at 200°C for 30 minutes to form a hole transport layer with a thickness of 30 μm, and a substrate comprising a hole injection layer and a hole transport layer was obtained (Sample 4).

[0128] Note that by shifting the trajectory of inkjet head unit-1 by 0.5 mm, the trajectories of 14 nozzles are shifted along the direction perpendicular to the scanning direction.

[0129] [Sample 5] The same ink as the ink for the hole transport layer used in Sample 3 was prepared, and the ink for the hole transport layer was applied onto the hole injection layer of Sample 1 under the same conditions as Sample 3, except that inkjet head unit-1 and Sample 1 were positioned so that the trajectory of inkjet head unit-1 did not deviate from the trajectory when the hole injection layer was formed.

[0130] [Evaluation of Surface Condition (2)] The root mean square surface roughness (RMS) and maximum in-plane height difference (Rmax) were measured for Samples 3 to 5, in which a hole transport layer was formed on the hole injection layer of Sample 1 while changing the nozzle trajectory deviation width. The root mean square surface roughness (RMS) and maximum in-plane height difference (Rmax) were evaluated using an atomic force microscope (manufactured by Bruker Japan). The width of the irregularities was evaluated using an atomic force microscope, and the measurement range was measured near the center of the two heads, and the width was evaluated as the width of the range in which the root mean square surface roughness (RMS) was 0.3 nm or more.

[0131]

[0132] From the evaluation results shown in Table 2, it can be confirmed that the substrate including the hole injection layer and hole transport layer of Sample 3 exhibited values ​​that were one order of magnitude smaller than those of Samples 4 and 5 in both the root mean square surface roughness and the maximum in-plane height difference at the joint of the hole transport layer in the joint portion of the inkjet head.

[0133] 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. Industrial application fields

[0134] The present disclosure can be used, for example, in display devices having a display area such as smartphones and tablets, and in the manufacture of such devices.

[0135] REFERENCE SIGNS LIST 11 Support substrate (substrate) 13 Substrate (thin film transistor layer) 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 50 Inkjet head unit 51 Inkjet head (first inkjet head) 52 Inkjet head (second inkjet head) 1L １ …1L ｎ , 2L １ …2L ｎ Nozzle row 1N １ …1N ｍ , 2N １ …2N ｍ nozzle

Claims

1. A method for manufacturing a functional layer by discharging ink containing nanoparticles from a plurality of inkjet heads onto a substrate provided with electrodes, wherein each of the plurality of inkjet heads has at least one nozzle row in which a plurality of nozzles are arranged along an intersection direction intersecting the scanning direction, the trajectories of the nozzle rows of adjacent inkjet heads do not overlap, and the distance between the nozzle at the end in the nozzle row of the first inkjet head and the nozzle at the end on the side of the first inkjet head in the nozzle row of the second inkjet head adjacent to the first inkjet head is equal to the distance between the nozzles in each nozzle row, and the first and second inkjet heads are arranged so that the functional layer containing the nanoparticles is manufactured by scanning the first and second inkjet heads simultaneously.

2. The method for manufacturing a functional layer according to claim 1, wherein the ink is supplied to each of the plurality of inkjet heads from a circulation tank.

3. The method for manufacturing a functional layer according to claim 1 or 2, wherein the at least one nanoparticle is selected from NiO, ZnO, and MgZnO.

4. The method for manufacturing a functional layer according to any one of claims 1 to 3, wherein the inkjet heads arranged at both ends in the intersection direction of the plurality of inkjet heads are scanned on two sides along the scanning direction on the substrate.

5. The method for manufacturing a functional layer according to any one of claims 1 to 4, wherein a partition wall surrounding the electrodes is formed on the substrate.

6. The method for manufacturing a functional layer according to any one of claims 1 to 5, wherein the ink contains at least one organic solvent selected from propylene glycol, ethylene glycol, diethylene glycol, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and poly(ethylene glycol) methacrylate as a dispersion solvent for the nanoparticles.

7. A method for manufacturing a light-emitting element including the functional layer between a first electrode and a second electrode, the method comprising: forming the functional layer by performing the method for manufacturing the functional layer according to any one of claims 1 to 6 using the electrode as the first electrode; forming a light-emitting layer on the functional layer; and forming the second electrode on the light-emitting layer, wherein the light-emitting layer contains quantum dots or an organic light-emitting compound.

8. The method for manufacturing a light-emitting element according to claim 7, further comprising, after the step of forming the light-emitting layer and before the step of forming the second electrode, a step of forming a functional layer different from the functional layer, wherein the trajectories of the plurality of inkjet heads when forming the functional layer and the trajectories of the plurality of inkjet heads when forming the different functional layer are shifted from each other by 0.7 mm or more along the intersecting direction.

9. The method for manufacturing a light-emitting element according to claim 8, further comprising a step of forming an organic layer in at least one of after the step of forming the functional layer and before the step of forming the light-emitting layer, or after the step of forming the light-emitting layer and before the step of manufacturing the different functional layer, wherein the trajectories of the plurality of inkjet heads in the step of forming the functional layer, the trajectories of the plurality of inkjet heads in the step of forming the organic layer, and the trajectories of the plurality of inkjet heads in the step of forming the different functional layer are shifted from each other by 0.7 mm or more along the intersecting direction.

10. The method for manufacturing a light-emitting element according to claim 8 or 9, wherein the functional layer is a hole injection layer and the different functional layer is an electron transport layer, or the functional layer is an electron transport layer and the different functional layer is a hole injection layer.

11. A method for manufacturing a display device including a display area on a substrate having a plurality of the light-emitting elements formed by performing the method for manufacturing a light-emitting element according to any one of claims 7 to 10.

Images