Display device, method for manufacturing display device, and method for forming plurality of functional layers

Abstract

A display device (1) comprises a red light-emitting element (25R) including an anode that is a lower electrode (21), a cathode that is an upper electrode (24), and a red light-emitting layer (23 REM) that is a patterned functional layer and is provided between the anode that is the lower electrode (21) and the cathode that is the upper electrode (24). The red light-emitting layer (23 REM) includes a central portion (23 REM1) and an outer peripheral portion (23 REM2) provided outside the central portion (23 REM1). The outer peripheral portion (23 REM2) includes one or more kinds of elements that are the same as the elements included in the central portion (23 REM1) and has a composition different from the composition of the central portion (23 REM1).

Description

Display device, method for manufacturing a display device, and method for forming multiple functional layers

[0001] This disclosure relates to a display device, a method for manufacturing a display device, and a method for forming multiple functional layers.

[0002] In recent years, display devices equipped with light-emitting elements such as OLEDs (Organic Light Emitting Diodes) or QLEDs (Quantum Dot Light Emitting Diodes) have attracted considerable attention due to their ability to achieve lower power consumption, thinner designs, and higher image quality.

[0003] Patent Document 1 describes a display device equipped with OLEDs (Organic Light Emitting Diodes) as light-emitting elements, wherein a common hole injection layer, a common hole transport layer, and a common electron transport layer are provided for a plurality of OLEDs arranged in the display area.

[0004] Japanese Patent Application Publication No. 2014-164829

[0005] In the case of the display device described in Patent Document 1, it is not necessary to pattern the common hole injection layer, common hole transport layer, and common electron transport layer, so it can be manufactured simply. However, the functional layers provided in the display device described in Patent Document 1, namely the common hole injection layer, common hole transport layer, common electron transport layer, and each color light-emitting layer, are all composed of a single composition, and these functional layers exist even in the non-light-emitting region where the lower electrode, the first electrode, and the common hole injection layer are not in contact. Therefore, leakage current that may occur in the non-light-emitting region cannot be suppressed. Consequently, the display device described in Patent Document 1 has the problem of reduced light-emitting efficiency.

[0006] One aspect of this disclosure aims to provide a display device with improved luminous efficiency, a method for manufacturing the display device, and a method for forming multiple functional layers.

[0007] To solve the aforementioned problems, the display device of this disclosure includes a light-emitting element comprising an anode, a cathode, and a patterned functional layer provided between the anode and the cathode, wherein the functional layer comprises a central portion and an outer peripheral portion provided outside the central portion, and the outer peripheral portion contains one or more of the same elements as those contained in the central portion and has a composition different from that of the central portion.

[0008] To solve the above problems, the method for manufacturing a display device of the present disclosure includes: a step of forming the functional layer; a step of forming a resist film on the functional layer; a step of patterning the resist film to form openings in the resist film; a first etching step of removing a portion of the functional layer exposed from the openings; and a second etching step of using an etchant to allow the etchant to penetrate the remaining portion of the functional layer to form the outer periphery.

[0009] A method for forming multiple functional layers according to the present disclosure, in order to solve the above problems, includes the steps of: forming a first functional layer; forming a first resist film on the first functional layer; patterning the first resist film to form a first opening in the first resist film; a first etching step to remove a portion of the first functional layer exposed from the first opening; a second etching step to allow a first etchant to penetrate the remaining portion of the first functional layer; heat treating the first resist film; and forming a second functional layer different from the first functional layer on the first opening and the first resist film.

[0010] According to one aspect of this disclosure, a display device with improved luminous efficiency, a method for manufacturing the display device, and a method for forming multiple functional layers can be provided.

[0011] This is a plan view showing the schematic configuration of the display device of Embodiment 1. This is a diagram showing the process of forming the red light-emitting layer, green light-emitting layer, and blue light-emitting layer provided in the display device of Embodiment 1. This is a diagram showing an example of the process of forming the red light-emitting layer provided in the display device of Embodiment 1. This is a diagram showing another example of the process of forming the red light-emitting layer provided in the display device of Embodiment 1. This is a cross-sectional view showing the schematic configuration of the red light-emitting element and the green light-emitting element provided in the display device of Embodiment 1. This is a diagram showing the process of forming the red light-emitting layer, green light-emitting layer, and blue light-emitting layer provided in the display device of Embodiment 2. This is a diagram showing an example of the process of forming the red light-emitting layer provided in the display device of Embodiment 2. This is a diagram showing an example of the process of forming the green light-emitting layer provided in the display device of Embodiment 2. This is a cross-sectional view showing the schematic configuration of the red light-emitting element and the blue light-emitting element provided in the display device of Embodiment 2. This is a diagram showing another example of the process of forming the red light-emitting layer and the green light-emitting layer provided in the display device of Embodiment 2. This is a diagram showing the process of forming the red light-emitting layer, green light-emitting layer, and blue light-emitting layer provided in the display device of Embodiment 3. This is a cross-sectional view showing the schematic configuration of the red light-emitting element and the blue light-emitting element provided in the display device of Embodiment 3. This is a cross-sectional view showing the schematic configuration of the red light-emitting element and the green light-emitting element provided in the display device of Embodiment 4. This is a diagram showing an example of the process for forming the red light-emitting layer provided in the display device of Embodiment 4. This is a diagram showing an example of the process for forming the green light-emitting layer provided in the display device of Embodiment 4. This is a cross-sectional view showing the schematic configuration of the red light-emitting element and the green light-emitting element provided in the display device of Embodiment 5.

[0012] The embodiments of this disclosure will be described below with reference to Figures 1 to 16. For the sake of convenience, in the following description, components having the same function as those described in a particular embodiment will be denoted by the same reference numerals, and their descriptions may be omitted.

[0013] [Embodiment 1] Figure 1 is a plan view showing the schematic configuration of the display device 1 of Embodiment 1.

[0014] As shown in Figure 1, the display device 1 comprises a frame area NDA and a display area DA. The display area DA of the display device 1 is provided with a plurality of pixels PIX, and each pixel PIX includes a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP. In this embodiment, the case in which one pixel PIX is composed of a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP is described as an example, but it is not limited to this. For example, one pixel PIX may include subpixels of other colors in addition to the red subpixel RSP, green subpixel GSP, and blue subpixel BSP.

[0015] Figure 2 shows the process of forming the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM provided in the display device 1 of Embodiment 1. Figure 3 shows an example of the process of forming the red light-emitting layer 23REM provided in the display device 1 of Embodiment 1. Figure 4 shows another example of the process of forming the red light-emitting layer 23REM provided in the display device 1 of Embodiment 1. Figure 5 is a cross-sectional view showing the schematic configuration of the red light-emitting element 25R and the green light-emitting element 25G provided in the display device 1 of Embodiment 1.

[0016] As shown in Figure 5, the display device 1 includes a red light-emitting element 25R which comprises an anode that is a lower electrode 21, a cathode that is an upper electrode 24, and a red light-emitting layer 23REM that is a patterned functional layer provided between the anode 21 and the cathode 24. As shown in Figures 2 and 5, the red light-emitting layer 23REM includes a central portion 23REM1 and an outer peripheral portion 23REM2 provided outside the central portion 23REM1. The outer peripheral portion 23REM2 contains one or more of the same elements as those contained in the central portion 23REM1 and has a different composition from that of the central portion 23REM1.

[0017] As shown in Figure 5, the display device 1 includes a green light-emitting element 25G which comprises an anode that is a lower electrode 21, a cathode that is an upper electrode 24, and a green light-emitting layer 23GEM that is a patterned functional layer provided between the anode 21 and the cathode 24. As shown in Figures 2 and 5, the green light-emitting layer 23GEM includes a central portion 23GEM1 and an outer peripheral portion 23GEM2 provided outside the central portion 23GEM1. The outer peripheral portion 23GEM2 contains one or more of the same elements as those contained in the central portion 23GEM1 and has a different composition from that of the central portion 23GEM1.

[0018] Although not shown in the figures, the display device 1 includes a blue light-emitting element comprising an anode which is a lower electrode 21, a cathode which is an upper electrode 24, and a blue light-emitting layer 23BEM which is a patterned functional layer provided between the anode which is the lower electrode 21 and the cathode which is the upper electrode 24. As shown in Figure 2, the blue light-emitting layer 23BEM includes a central portion 23BEM1 and an outer peripheral portion 23BEM2 provided outside the central portion 23BEM1. The outer peripheral portion 23BEM2 contains one or more of the same elements as those contained in the central portion 23BEM1 and has a different composition from that of the central portion 23BEM1.

[0019] In this embodiment, the red subpixel RSP of the display device 1 shown in Figure 1 is provided with the red light-emitting element 25R shown in Figure 5, the green subpixel GSP of the display device 1 shown in Figure 1 is provided with the green light-emitting element 25G shown in Figure 5, and the blue subpixel BSP of the display device 1 shown in Figure 1 is provided with the blue light-emitting element described above (not shown). This is described as an example, but the invention is not limited to this. For example, the display device 1 may be provided with a light-emitting element in only one subpixel of a certain color among the red subpixel RSP, green subpixel GSP, and blue subpixel BSP, which includes the light-emitting layer of the corresponding color including the central portion and the outer periphery described above, and the remaining subpixels may be provided with a conventional light-emitting element in the corresponding color that does not include the central portion and the outer periphery described above. Furthermore, the display device 1 may be provided with light-emitting elements in only two subpixels of a certain color among the red subpixel RSP, green subpixel GSP, and blue subpixel BSP, which includes the light-emitting layer of the corresponding color including the central portion and the outer periphery described above, and the remaining subpixels may be provided with a conventional light-emitting element in the corresponding color that does not include the light-emitting layer of the corresponding color.

[0020] As shown in Figure 5, the red light-emitting element 25R, the green light-emitting element 25G, and the aforementioned blue light-emitting element (not shown) are each provided on the substrate 2. The substrate 2 may also be provided with a thin-film transistor, which includes a drain electrode electrically connected to the lower electrode 21, although this is not shown.

[0021] In this embodiment, as shown in Figure 5, the display device 1 is described as having an insulating bank 22 that covers the edge of the lower electrode 21, but the display device 1 does not necessarily have to have a bank 22. The bank 22 can be formed, for example, by coating an organic material such as polyimide or acrylic and then patterning it using a photolithography method.

[0022] In this embodiment, as shown in Figure 5, the display device 1 is provided with a first charge transport layer 23CT1 between the lower electrode 21 and each color light-emitting layer, and a second charge transport layer 23CT2 between each color light-emitting layer and the upper electrode 24. This is described as an example, but the embodiment is not limited to this, and for example, at least one of the first charge transport layer 23CT1 and the second charge transport layer 23CT2 may be omitted as appropriate.

[0023] In this embodiment, since the lower electrode 21 is the anode and the upper electrode 24 is the cathode, the case in which the first charge transport layer 23CT1 is provided as a common hole transport layer (HTL) and the second charge transport layer 23CT2 is provided as a common electron transport layer (ETL) will be described as an example, but the embodiment is not limited to this. The first charge transport layer 23CT1 may be provided as at least one of a hole transport layer (HTL) and a hole injection layer (HIL), and the hole transport layer (HTL) and the hole injection layer (HIL) may be formed as a common layer, or they may not be formed as a common layer. When the first charge transport layer 23CT1 is provided as a hole transport layer (HTL) and a hole injection layer (HIL), the hole injection layer (HIL) and the hole transport layer (HTL) are stacked in this order from the lower electrode 21 side. Furthermore, the second charge transport layer 23CT2 may include at least one of an electron transport layer (ETL) and an electron injection layer (EIL), and the electron transport layer (ETL) and the electron injection layer (EIL) may or may not be formed as a common layer. When the second charge transport layer 23CT2 includes an electron transport layer (ETL) and an electron injection layer (EIL), the electron injection layer (EIL) and the electron transport layer (ETL) are stacked in this order from the upper electrode 24 side.

[0024] On the other hand, when the lower electrode 21 is the cathode and the upper electrode 24 is the anode, the first charge transport layer 23CT1 may include at least one of an electron transport layer (ETL) and an electron injection layer (EIL), and the second charge transport layer 23CT2 may include at least one of a hole transport layer (HTL) and a hole injection layer (HIL).

[0025] The material used for the hole injection layer (HIL) is not particularly limited as long as it is a hole-injection material that can stabilize the injection of holes into the light-emitting layer. For example, a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS) can be used.

[0026] As materials used in the hole transport layer (HTL), for example, organic materials such as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB), N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine (poly-TPD), or polyvinylcarbazole (PVK) may be used, or nanoparticles with hole transport properties such as NiO particles may be used.

[0027] As materials used for the electron transport layer (ETL), for example, organic materials such as 2,2',2"-(1,3,5-benzintriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) may be used, or electron-transporting nanoparticles such as ZnO particles or oxide particles containing Zn and Mg may be used.

[0028] The material used for the electron injection layer (EIL) is not particularly limited as long as it is an electron-injection material that can stabilize the injection of electrons into the light-emitting layer. For example, alkali metals or alkaline earth metals such as aluminum, strontium, calcium, lithium, cesium, magnesium oxide, aluminum oxide, strontium oxide, lithium oxide, lithium fluoride, magnesium fluoride, strontium fluoride, calcium fluoride, barium fluoride, cesium fluoride, polymethyl methacrylate, sodium polystyrene sulfonate, alkali metals or alkaline earth metals, oxides of alkali metals or alkaline earth metals, fluorides of alkali metals or alkaline earth metals, and organic complexes of alkali metals can be used.

[0029] The red light-emitting element 25R, the green light-emitting element 25G, and the blue light-emitting element (not shown) described above, provided in the display device 1 shown in Figure 5, may be of the top-emission type or the bottom-emission type. In this embodiment, the red light-emitting element 25R, the green light-emitting element 25G, and the blue light-emitting element (not shown) described above are each light-emitting elements with a forward-facing structure in which the cathode, which is the upper electrode 24, is positioned as an upper layer above the anode, which is the lower electrode 21. To make such a forward-facing light-emitting element of the top-emission type, the anode, which is the lower electrode 21, may be formed from an electrode material that reflects visible light, and the cathode, which is the upper electrode 24, may be formed from an electrode material that transmits visible light. To make such a forward-facing light-emitting element of the bottom-emission type, the anode, which is the lower electrode 21, may be formed from an electrode material that transmits visible light, and the cathode, which is the upper electrode 24, may be formed from an electrode material that reflects visible light. On the other hand, the display device 1 may also include a light-emitting element with an inverted-facing structure in which the anode, which is the upper electrode 24, is positioned as an upper layer above the cathode, which is the lower electrode 21. To make such an inverted-component light-emitting element a top-emission type, the cathode, which is the lower electrode 21, should be made of an electrode material that reflects visible light, and the anode, which is the upper electrode 24, should be made of an electrode material that transmits visible light. To make such an inverted-component light-emitting element a bottom-emission type, the cathode, which is the lower electrode 21, should be made of an electrode material that transmits visible light, and the anode, which is the upper electrode 24, should be made of an electrode material that reflects visible light.

[0030] The electrode material that reflects visible light is not particularly limited as long as it can reflect visible light and is conductive, but examples include metallic materials such as Al, Mg, Li, and Ag, or alloys of the metallic materials, or laminates of the metallic material and transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), or laminates of the alloy and the transparent metal oxide.

[0031] On the other hand, the electrode material that transmits visible light is not particularly limited as long as it can transmit visible light and has conductivity. For example, it can be a transparent metal oxide (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), a thin film made of a metal material such as Al or Ag, or a nanowire made of a metal material such as Al or Ag.

[0032] In each embodiment of the present disclosure, as shown in FIG. 2, each of the red light-emitting layer 23REM, green light-emitting layer 23GEM, and blue light-emitting layer 23BEM provided in the display device 1 is a light-emitting layer containing quantum dots. As an example, the case where the display device 1 is a display device equipped with a QLED (Quantum dot Light Emitting Diode) will be described, but it is not limited thereto. For example, it may be a display device equipped with an OLED (Organic Light Emitting Diode) having a light-emitting layer containing an organic light-emitting material instead of the light-emitting layer containing quantum dots. The quantum dots may have, for example, a core structure, a core / shell / shell structure, or a core / shell structure with a continuously varying ratio. Note that the shell may cover a part of the core, but it is better if it completely covers the core. The core of the quantum dots may contain, for example, one or more selected from Si, Ge, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, and ZnTeSe. The shell of the quantum dots may contain, for example, one or more selected from CdS, ZnS, ZnSe, CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AgInP (AIP), and those with a lattice constant close to the core and a larger bandgap than the core may be selected.

[0033] At least one layer of the light-emitting layers of various colors may contain an additive that covers the periphery of at least one quantum dot or fills the space between at least two quantum dots. The additive may have properties as a semiconductor or an insulator, for example. The additive may contain any one of metal oxides, semi-metal oxides, and metal sulfides.

[0034] As an oxide, the additive may be, for example, silicon oxide (SiO ２ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), boron oxide (B ２ O ３ ), phosphorus oxide (P ２ O ５ ), germanium oxide (GeO ２ ), hafnium oxide (HfO ２ ), zinc oxide (ZnO), zirconium oxide (ZrO ２ ), tellurium oxide (TeO ２ ), bismuth oxide (Bi ２ O ３ ), vanadium oxide (V ２ O ５ ), antimony oxide (Sb ２ O ５ ), lead oxide (PbO), and copper oxide (CuO), and may contain at least one of them. Here, the case where the additive is formed as a polymer may be included. For example, when the additive contains silicon oxide as an oxide, the case where the additive is a siloxane compound having a siloxane bond may be included. Also, as a sulfide, the additive may contain at least one of, for example, zinc sulfide (ZnS) and zinc magnesium sulfide (ZnMgS, ZnMgS ２ ). Note that the chemical formula of the compound is a representative example, and the composition ratio described in the chemical formula may be stoichiometric or not necessarily stoichiometric.

[0035] In the case where the adduct surrounds at least one quantum dot, the quantum dot may be considered to be covered by the adduct if, in the cross-section of the light-emitting layer passing through the quantum dot, the adduct occupies more than 90% of the area around the quantum dot. The adduct may be composed mainly of silicon dioxide, for example, and may be positioned in contact with the surface of the quantum dot or with an organic ligand between the adduct and the quantum dot.

[0036] If the adduct is formed to fill the space between at least two quantum dots, the adduct is 1000 nm in a direction perpendicular to the film thickness direction at any position in the film thickness direction of the light-emitting layer. ２ It may be formed as a continuous film having the above area. In addition, in the light-emitting layer, quantum dots may be embedded in a continuous film of adducts (for example, the adduct in this case may be a matrix MR as described later). For example, if 60% or more of the surface of 80% or more of the quantum dots constituting the light-emitting layer is in contact with a continuous film of adducts, then the quantum dots contained in the light-emitting layer can be said to be embedded in the adduct. Furthermore, when we say that the adduct fills the space between at least two quantum dots, the space between the two quantum dots may be filled only with the adduct, or with the adduct and other materials. In addition to the adduct, a material such as a ligand different from the adduct may be included between the two quantum dots. The material such as the ligand may be an organic ligand that coordinates to the quantum dot, or an organic ligand that is separated from the quantum dot. When the light-emitting layer contains an organic ligand, for example, the weight ratio of the organic ligand to the total weight of the light-emitting layer may be less than 5%. The weight ratio of the organic ligand can be measured, for example, using TOF-SIMS (time-of-flight secondary ion mass spectrometry). If an organic ligand is dispersed in the light-emitting layer, the organic ligand may contribute to the injection of holes and electrons into the quantum dot.

[0037] In forming the light-emitting layer, first, a quantum dot dispersion is prepared. The quantum dot dispersion is a dispersion in which quantum dots and an adduct precursor are dispersed in a solvent. The precursor includes a material that is converted into an adduct through hydrolysis and dehydration condensation by performing a specific operation such as heating or light irradiation. The precursor may have a coordinating functional group that forms a coordination bond with the surface of the quantum dots in the quantum dot dispersion. In this case, the precursor may coordinate to the quantum dots in the quantum dot dispersion. The quantum dot dispersion may also contain a halide having a halogen atom (for example, zinc chloride (ZnCl)). ２ It may also contain ). By mixing a material having halogen atoms into the quantum dot dispersion, the halogen atoms can coat the surface of the quantum dots independently of the adduct, thereby reducing defects on the surface of the quantum dots. Therefore, by having halogen atoms in the adduct, each light-emitting device increases the coverage of the quantum dots in the light-emitting layer, thereby improving the light-emitting properties.

[0038] A quantum dot dispersion may be prepared, for example, by stirring a dispersion containing quantum dots and a dispersion containing a precursor to prepare a mixture, and then extracting a predetermined layer from the mixture. Here, the dispersion containing quantum dots may contain an organic ligand that coordinates to the quantum dots. In this case, for example, during the stirring for the preparation of the mixture, the ligand that coordinates to the quantum dots may be replaced from an organic ligand to a part of a precursor such as trimethoxysilylpropanethol (TMSPT).

[0039] For example, if the adduct contains silicon dioxide and the precursor has a coordinating functional group, the precursor may contain trimethoxysilylpropanethol (TMSPT). Also, if the adduct contains silicon dioxide and the precursor does not have a coordinating functional group, the precursor may contain diphenylsilanediol (DPSD). Furthermore, the precursor may contain barium hydroxide as a reaction catalyst. Also, for example, if the adduct contains zinc sulfide, the precursor may contain zinc xanthogenic acid, zinc thioureate, and zinc dithiocarboxylate, etc.

[0040] Next, the quantum dot dispersion is applied to the lower layer of the light-emitting layer to convert the precursor into an adduct. This conversion of the precursor into an adduct occurs, for example, by heating the applied quantum dot dispersion, which volatilizes the solvent and converts the precursor into an adduct. For example, if the precursor contains diphenylsilanediol (DPSD) and trimethoxysilylpropantheol (TMSPT), dehydration condensation occurs between trimethoxysilylpropantheol (TMSPT) molecules, between diphenylsilanediol (DPSD) molecules, and between diphenylsilanediol (DPSD) and trimethoxysilylpropantheol (TMSPT), forming silicon oxide as an adduct. Alternatively, barium hydroxide may act as a catalyst to further promote dehydration condensation. Furthermore, if the precursor contains zinc xanthogenic acid, the zinc xanthogenic acid is decomposed to form zinc sulfide as an adduct. The conversion of the precursor into an adduct occurs sequentially around the quantum dots in the quantum dot dispersion. By this method, a light-emitting layer having an adduct can be formed.

[0041] As shown in Figure 2, the manufacturing method of the display device 1 includes the steps of: forming a red light-emitting layer 23REM' over at least the entire display area DA, then patterning the red light-emitting layer 23REM (S1); forming a green light-emitting layer 23GEM' over at least the entire display area DA (S2); patterning the green light-emitting layer 23GEM (S3); forming a blue light-emitting layer 23BEM' over at least the entire display area DA (S4); and patterning the blue light-emitting layer 23BEM (S5). The process (S1) for patterning the red light-emitting layer 23REM shown in Figure 2 includes, as shown in Figure 3, a process of forming a first resist film RES1 on the red light-emitting layer 23REM' after the process of forming the red light-emitting layer 23REM' over at least the entire display area DA, a process (S1a) for patterning the first resist film RES1 to form a first opening KK1 in the first resist film RES1, a first etching process (S1a) for removing a portion of the red light-emitting layer 23REM' exposed from the first opening KK1, and a second etching process (S1b) for using an etchant to penetrate the remaining portion of the red light-emitting layer 23REM' and form the outer peripheral portion 23REM2 of the red light-emitting layer 23REM. The step of peeling off the first resist film RES1 (not shown) may be performed immediately after the second etching step (S1b). However, for the purpose of protecting the red light-emitting layer 23REM, the first resist film RES1 may be left in place and a light-emitting layer of another color may be formed.

[0042] In the step of patterning the first resist film RES1 shown in Figure 3 (S1a), island-shaped first resist film RES1 is formed. In the step of patterning the red light-emitting layer 23REM (S1), as shown in Figure 2, the red light-emitting layer 23REM includes a central portion 23REM1 and an outer peripheral portion 23REM2, and is formed in an island shape for each red subpixel.

[0043] In addition, in the first etching step described above, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by the etchant used in the second etching step (S1b). In this case, the first etching step and the second etching step (S1b) described above may be performed as a single etching step.

[0044] In this embodiment, the first etching step and the second etching step (S1b) described above were explained using the same etchant and wet etching as an example, but the invention is not limited to this. For example, in the first etching step (S1b) performed after the patterning step (S1a) of the first resist film RES1 shown in Figure 4, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by dry etching. In the subsequent second etching step (S1c) shown in Figure 4, wet etching may be performed using an etchant to allow the etchant to penetrate the remaining portion of the red light-emitting layer 23REM', thereby forming the outer peripheral portion 23REM2 of the red light-emitting layer 23REM.

[0045] In the wet etching process described above, an acidic etchant or a basic etchant can be used. Examples of acidic etchants include hydrochloric acid (HCl) and nitric acid (HNO). ３ ) and sulfuric acid (H ２ SO ４ Suitable etchants include, for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH).

[0046] As described above, the red light-emitting layer 23REM provided in the display device 1 is a light-emitting layer containing quantum dots, and in this embodiment, quantum dots containing zinc or indium are used, so the outer peripheral portion 23REM2 of the red light-emitting layer 23REM becomes a reaction product of an acid or base and a part of the red light-emitting layer 23REM. Examples of such reaction products include zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate. Therefore, the outer peripheral portion 23REM2 of the red light-emitting layer 23REM contains at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate.

[0047] Furthermore, the same element contained in the central portion 23REM1 and the outer peripheral portion 23REM2 of the red light-emitting layer 23REM is a metallic element (for example, zinc or indium), and the outer peripheral portion 23REM2 of the red light-emitting layer 23REM contains at least one of the following: a halide of the metallic element (for example, zinc or indium), a sulfide of the metallic element (for example, zinc or indium), and a nitrate of the metallic element (for example, zinc or indium).

[0048] As described above, the outer peripheral portion 23REM2 of the red light-emitting layer 23REM contains one or more of the same elements as those contained in the central portion 23REM1 of the red light-emitting layer 23REM (for example, zinc or indium). Furthermore, the outer peripheral portion 23REM2 of the red light-emitting layer 23REM contains at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, or indium nitrate as a component, and its composition differs from that of the central portion 23REM1 of the red light-emitting layer 23REM.

[0049] In the display device 1 shown in Figure 5, a non-luminescent region is provided where the lower electrode 21 and the first charge transport layer 23CT1 are not in contact, and the outer periphery 23REM2 of the red light-emitting layer 23REM is superimposed in a plan view. As described above, the outer periphery 23REM2 of the red light-emitting layer 23REM contains at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate, so that leakage current that may occur in the non-luminescent region can be suppressed by the outer periphery 23REM2 of the red light-emitting layer 23REM, thereby realizing a display device 1 with improved luminous efficiency and a method for manufacturing the display device 1 with improved luminous efficiency. Note that if a bank 22 is not provided, the first charge transport layer 23CT1 formed between two adjacent lower electrodes 21 does not come into contact with the lower electrodes 21, so this part becomes a non-luminescent region. Also, if the first charge transport layer 23CT1 is not provided, the region where the lower electrode 21 and the red light-emitting layer 23REM are not in contact in a plan view becomes a non-luminescent region.

[0050] In this embodiment, as described above, each of the red subpixels RSP, green subpixels GSP, and blue subpixels BSP provided in the display device 1 is equipped with a light-emitting element that includes the central portion and the outer peripheral portion described above, and is equipped with a light-emitting layer of the corresponding color. Therefore, as shown in Figure 2, the manufacturing method of the display device 1 is a process (S1) of patterning the red light-emitting layer 23REM including the central portion 23REM1 and the outer peripheral portion 23REM2, followed by a functional layer provided between the anode, which is the lower electrode 21, and the cathode, which is the upper electrode 24. The process further includes the steps of forming a green light-emitting layer 23GEM' over at least the entire display area DA (S2), patterning the green light-emitting layer 23GEM including the central portion 23GEM1 and the outer peripheral portion 23GEM2 (S3), forming a blue light-emitting layer 23BEM', which is a functional layer provided between the anode (lower electrode 21) and the cathode (upper electrode 24), over at least the entire display area DA (S4), and patterning the blue light-emitting layer 23BEM including the central portion 23BEM1 and the outer peripheral portion 23BEM2 (S5). Note that the steps of patterning the green light-emitting layer 23GEM (S3) and patterning the blue light-emitting layer 23BEM (S5) can be carried out in the same manner as the step of patterning the red light-emitting layer 23REM (S1) described above, so a detailed explanation thereof is omitted. Furthermore, by performing the steps of forming the second charge transport layer 23CT2 and forming the upper electrode 24 after the step of patterning the blue light-emitting layer 23BEM (S5), the display device 1 shown in Figure 5 can be manufactured. In this embodiment, the case in which the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM are formed in this order has been described as an example, but the order in which the light-emitting layers are formed is not limited to this.

[0051] In the display device 1 shown in Figure 5, the outer periphery 23GEM2 of the green light-emitting layer 23GEM is provided so as to overlap, in a plan view, a non-light-emitting region where the lower electrode 21 and the first charge transport layer 23CT1 are not in contact. As described above, the outer periphery 23GEM2 of the green light-emitting layer 23GEM contains at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate. Therefore, leakage current that may occur in the non-light-emitting region can be suppressed by the outer periphery 23GEM2 of the green light-emitting layer 23GEM, thereby realizing a display device 1 with improved luminous efficiency and a method for manufacturing the display device 1 with improved luminous efficiency.

[0052] In the display device 1 shown in Figure 5, the outer periphery 23BEM2 of the blue light-emitting layer 23BEM is provided so as to overlap, in a plan view, a non-light-emitting region where the lower electrode 21 and the first charge transport layer 23CT1 are not in contact. As described above, the outer periphery 23BEM2 of the blue light-emitting layer 23BEM contains at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate. Therefore, leakage current that may occur in the non-light-emitting region can be suppressed by the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, thereby realizing a display device 1 with improved luminous efficiency and a method for manufacturing the display device 1 with improved luminous efficiency.

[0053] In this embodiment, the case in which the patterned functional layer is a red light-emitting layer 23REM, a green light-emitting layer 23GEM, and a blue light-emitting layer 23BEM has been described as an example, but it is not limited to this, and as in Embodiment 5 described later, the patterned functional layer may be a first charge transport layer 23CT1 or a second charge transport layer 23CT2.

[0054] [Embodiment 2] The display device 1a of Embodiment 2 differs from the display device 1 of Embodiment 1 described above, in that two different light-emitting layers are superimposed in a plan view, whereas the light-emitting layers are not superimposed in a plan view.

[0055] Figure 6 shows the process of forming the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM provided in the display device 1a of Embodiment 2. Figure 7 shows an example of the process of forming the red light-emitting layer 23REM provided in the display device 1a of Embodiment 2. Figure 8 shows an example of the process of forming the green light-emitting layer 23GEM provided in the display device 1a of Embodiment 2. Figure 9 is a cross-sectional view showing the schematic configuration of the red light-emitting element 25R and the blue light-emitting element 25B provided in the display device 1a of Embodiment 2. Figure 10 shows another example of the process of forming the red light-emitting layer 23REM and the green light-emitting layer 23GEM provided in the display device 1a of Embodiment 2.

[0056] As shown in Figure 9, the display device 1a includes a red light-emitting element 25R which includes a red light-emitting layer 23REM as a first functional layer which is a patterned functional layer, and a blue light-emitting element 25B which includes a blue light-emitting layer 23BEM as a second functional layer which is a patterned functional layer, and one end of the red light-emitting layer 23REM, i.e., the outer periphery 23REM2 of the red light-emitting layer 23REM, and one end of the blue light-emitting layer 23BEM, i.e., the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, are superimposed in a plan view. As shown in Figure 6, the display device 1a further includes a green light-emitting element, which includes a green light-emitting layer 23GEM as a third functional layer, which is a patterned functional layer. In a plan view, one end of the green light-emitting layer 23GEM, i.e., the outer periphery 23GEM2 of the green light-emitting layer 23GEM, and the other end of the blue light-emitting layer 23BEM, i.e., the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, are superimposed. In a plan view, the other end of the green light-emitting layer 23GEM, i.e., the outer periphery 23GEM2 of the green light-emitting layer 23GEM, and the other end of the red light-emitting layer 23REM, i.e., the outer periphery 23REM2 of the red light-emitting layer 23REM, are superimposed.

[0057] In the display device 1a shown in Figure 9, a laminate is provided in which the outer periphery portions of two different light-emitting layers are stacked so as to overlap in a plan view, and a non-light-emitting region is provided in which the lower electrode 21 and the first charge transport layer 23CT1 are not in contact. The laminate can suppress leakage current that may occur in the non-light-emitting region, thereby realizing a display device 1a with improved luminous efficiency and a method for manufacturing the display device 1a with improved luminous efficiency.

[0058] As shown in Figure 6, the manufacturing method of the display device 1a includes the steps of: forming a red light-emitting layer 23REM' over at least the entire display area DA and then patterning the red light-emitting layer 23REM (S1); forming a green light-emitting layer 23GEM' over at least the entire display area DA and then patterning the green light-emitting layer 23GEM (S2); and forming a blue light-emitting layer 23BEM' over at least the entire display area DA and then patterning the blue light-emitting layer 23BEM (S3). In this embodiment, the case in which the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM are formed in this order has been described as an example, but the order in which the light-emitting layers are formed is not limited to this. The process (S1) for patterning the red light-emitting layer 23REM shown in Figure 6 includes, as shown in Figure 7, a process of forming a first resist film RES1 on the red light-emitting layer 23REM' after the process of forming the red light-emitting layer 23REM' over at least the entire display area DA, a process (S1a) for patterning the first resist film RES1 to form a first opening KK1 in the first resist film RES1, a first etching process (S1a) for removing a portion of the red light-emitting layer 23REM' exposed from the first opening KK1, and a second etching process (S1b) for using an etchant to allow the etchant to penetrate the remaining portion of the red light-emitting layer 23REM' to form the outer peripheral portion 23REM2 of the red light-emitting layer 23REM. Here, we will explain using the case where the first resist film RES1 is peeled off (S1c) immediately after the second etching step (S1b) as an example. However, as will be described later, in order to protect the red light-emitting layer 23REM, the first resist film RES1 may not be peeled off and may be left in place while light-emitting layers of other colors are formed.

[0059] In the step of patterning the first resist film RES1 shown in Figure 7 (S1a), island-shaped first resist film RES1 is formed. In the step of patterning the red light-emitting layer 23REM (S1), as shown in Figure 6, the red light-emitting layer 23REM includes a central portion 23REM1 and an outer peripheral portion 23REM2, and is formed in an island shape spanning multiple red subpixels, a portion of multiple green subpixels, and a portion of multiple blue subpixels.

[0060] In addition, in the first etching step described above, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by the etchant used in the second etching step (S1b). In this case, the first etching step and the second etching step (S3'b) described above may be performed as a single etching step.

[0061] In this embodiment, the first etching step and the second etching step (S1b) described above were explained using the same etchant and wet etching as an example, but the embodiment is not limited to this. For example, in the first etching step described above, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by dry etching. In the subsequent second etching step (S1b) shown in Figure 7, wet etching may be used to allow the etchant to penetrate the remaining portion of the red light-emitting layer 23REM', thereby forming the outer peripheral portion 23REM2 of the red light-emitting layer 23REM.

[0062] As shown in Figure 6, the manufacturing method of the display device 1a includes a step (S2) of patterning the green light-emitting layer 23GEM' after forming the green light-emitting layer 23GEM' over at least the entire display area DA. The step (S2) of patterning the green light-emitting layer 23GEM shown in Figure 6 further includes a step (not shown) of forming a second resist film RES2 on the green light-emitting layer 23GEM' after the step of forming the green light-emitting layer 23GEM' over at least the entire display area DA, as shown in Figure 8; a step (S2a) of patterning the second resist film RES2 to form a second opening KK2 in the second resist film RES2; a first etching step (not shown) of removing a part of the green light-emitting layer 23GEM' exposed from the second opening KK2; and a second etching step (S2b) of using an etchant to allow the etchant to penetrate the remaining part of the green light-emitting layer 23GEM' to form the outer peripheral portion 23GEM2 of the green light-emitting layer 23GEM. Here, we will explain using the case where the second resist film RES2 is peeled off (S2c) immediately after the second etching step (S2b) as an example. However, as will be described later, in order to protect the green light-emitting layer 23GEM, the second resist film RES2 may not be peeled off and may be left in place while light-emitting layers of other colors are formed.

[0063] In the process of patterning the second resist film RES2 shown in Figure 8 (S2a), island-shaped second resist film RES2 is formed. In the process of patterning the green light-emitting layer 23GEM (S2), as shown in Figure 6, the green light-emitting layer 23GEM includes a central portion 23GEM1 and an outer peripheral portion 23GEM2, and is formed in an island shape spanning multiple green subpixels, a portion of multiple red subpixels, and a portion of multiple blue subpixels.

[0064] The process of patterning the blue light-emitting layer 23BEM shown in Figure 6 (S3) can be carried out in the same manner as the process of patterning the red light-emitting layer 23REM (S1) and the green light-emitting layer 23GEM (S2) described above, so a detailed explanation is omitted. Furthermore, after the process of patterning the blue light-emitting layer 23BEM (S3), the process of forming the second charge transport layer 23CT2 and the process of forming the upper electrode 24 can be carried out to manufacture the display device 1a shown in Figure 9.

[0065] The method for manufacturing the display device 1a includes a method for forming a plurality of functional layers, for example, a red light-emitting layer 23REM, a green light-emitting layer 23GEM, and a blue light-emitting layer 23BEM. The method for manufacturing the display device 1a includes a step of forming a first resist film RES1 on the red light-emitting layer 23REM', which is performed after the step of forming the red light-emitting layer 23REM' shown in Figures 6 and 7 over at least the entire display area DA (not shown), a step of patterning the first resist film RES1 to form a first opening KK1 in the first resist film RES1 shown in Figure 7 (S1a), a first etching step (not shown) to remove a portion of the red light-emitting layer 23REM' exposed from the first opening KK1, and the etchant shown in Figure 7. Preferably, the process includes: a second etching step (S1b) in which the etchant (first etchant) is used to penetrate a portion of the remaining red light-emitting layer 23REM' to form the outer peripheral portion 23REM2 of the red light-emitting layer 23REM; a heat treatment step (not shown) of the first resist film RES1, which is performed instead of the peeling step (S1c) of the first resist film RES1 shown in Figure 7; and a step (not shown) of forming a green light-emitting layer 23GEM' on the first opening KK1 and the first resist film RES1. As described above, by forming the green light-emitting layer 23GEM' while leaving the first resist film RES1 on the red light-emitting layer 23REM, the protective effect of the red light-emitting layer 23REM can be enhanced.

[0066] Between the second etching step (S1b) shown in Figure 7 and the heat treatment step (not shown) of the first resist film RES1, which is performed instead of the step (S1c) of stripping the first resist film RES1 shown in Figure 7, a step (S1b') may be performed, as shown in Figure 10, in which the area around the first opening KK1 of the first resist film RES1 is exposed and developed to enlarge the size of the first opening KK1. The first opening KK1' is larger than the first opening KK1.

[0067] In addition, in the first etching step described above, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by the etchant (first etchant) used in the second etching step (S1b). In this case, the first etching step and the second etching step (S1b) described above may be performed as a single etching step.

[0068] In this embodiment, the first etching step and the second etching step (S1b) described above were explained using the same etchant and wet etching as an example, but the embodiment is not limited to this. For example, in the first etching step described above, a portion of the red light-emitting layer 23REM' exposed from the first opening KK1 may be removed by dry etching. In the subsequent second etching step (S1b) shown in Figure 7, wet etching may be used to allow the etchant to penetrate the remaining portion of the red light-emitting layer 23REM', thereby forming the outer peripheral portion 23REM2 of the red light-emitting layer 23REM.

[0069] As shown in Figure 10, the method for manufacturing the display device 1a includes the steps of forming a green light-emitting layer 23GEM' on a first opening KK1' and a first resist film RES1 (S1c'), followed by forming a second resist film RES2 on the green light-emitting layer 23GEM' (not shown), patterning the second resist film RES2 to form a second opening KK2 at a position different from the first opening KK1' (S2a), a third etching step (not shown) to remove a portion of the green light-emitting layer 23GEM' exposed from the second opening KK2, and a fourth etching step (S2b) to use a second etchant to penetrate the remaining portion of the green light-emitting layer 23GEM' and form the outer peripheral portion 23GEM2 of the green light-emitting layer 23GEM.

[0070] In the third etching step described above, a portion of the green light-emitting layer 23GEM' exposed from the second opening KK2 may be removed by dry etching. Alternatively, in the third etching step described above, a portion of the green light-emitting layer 23GEM' exposed from the second opening KK2 may be removed by the second etchant used in the fourth etching step (S2b). In this case, the third etching step and the fourth etching step (S2b) described above may be performed as a single etching step.

[0071] The method for manufacturing the display device 1a further includes a step of peeling off the first resist film RES1 and the second resist film RES2 after the fourth etching step (S2b). In this embodiment, the step of peeling off the second resist film RES2 (S2c) and the step of peeling off the first resist film RES1 (not shown) were performed separately after the fourth etching step (S2b), but the method is not limited to this, and the first resist film RES1 and the second resist film RES2 may be peeled off together in a single peeling step.

[0072] Here, we have described an example in which the first resist film RES1 and the second resist film RES2 are removed immediately after the fourth etching step (S2b). However, we are not limited to this, and for the purpose of protecting the previously formed functional layers, the red light-emitting layer 23REM and the green light-emitting layer 23GEM, the first resist film RES1 and the second resist film RES2 may be left in place without being removed, and a light-emitting layer of another color, such as a blue light-emitting layer, may be formed.

[0073] [Embodiment 3] In the display device 1b of Embodiment 3, three different light-emitting layers are superimposed in a plan view, which differs from the display device 1 of Embodiment 1 described above, in that the light-emitting layers are not superimposed in a plan view, and the display device 1a of Embodiment 2 described above, in that two different light-emitting layers are superimposed in a plan view.

[0074] Figure 11 is a diagram showing the process of forming the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM provided in the display device 1b of Embodiment 3. Figure 12 is a cross-sectional view showing the schematic configuration of the red light-emitting element 25R and the blue light-emitting element 25B provided in the display device 1b of Embodiment 3. As shown in Figure 11, the manufacturing method of the display device 1b includes the steps of forming the red light-emitting layer 23REM' over at least the entire display area DA and then patterning the red light-emitting layer 23REM (S1), forming the green light-emitting layer 23GEM' over at least the entire display area DA and then patterning the green light-emitting layer 23GEM (S2), and forming the blue light-emitting layer 23BEM' over at least the entire display area DA and then patterning the blue light-emitting layer 23BEM (S3).

[0075] In the process (S1) of patterning the red light-emitting layer 23REM shown in Figure 11, a red light-emitting layer 23REM having a plurality of openings, a central portion 23REM1, and an outer peripheral portion 23REM2 is formed in the display area DA, as shown in Figure 11.

[0076] In the process (S2) of patterning the green light-emitting layer 23GEM shown in Figure 11, a green light-emitting layer 23GEM having a plurality of openings, a central portion 23GEM1, and an outer peripheral portion 23GEM2 is formed in the display area DA, as shown in Figure 11.

[0077] In the process of patterning the blue light-emitting layer 23BEM shown in Figure 11 (S3), a blue light-emitting layer 23BEM having a plurality of openings, a central portion 23BEM1, and an outer peripheral portion 23BEM2 is formed in the display area DA, as shown in Figure 11. Furthermore, after the process of patterning the blue light-emitting layer 23BEM (S3), the process of forming the second charge transport layer 23CT2 and the process of forming the upper electrode 24 can be performed to manufacture the display device 1b shown in Figure 12.

[0078] As shown in Figure 12, the display device 1b includes a red light-emitting element 25R which includes a red light-emitting layer 23REM as a first functional layer which is a patterned functional layer, and a blue light-emitting element 25B which includes a blue light-emitting layer 23BEM as a second functional layer which is a patterned functional layer, and one end of the red light-emitting layer 23REM, i.e., the outer periphery 23REM2 of the red light-emitting layer 23REM, and one end of the blue light-emitting layer 23BEM, i.e., the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, are superimposed in a plan view. Furthermore, in the manufacturing method of the display device 1b, the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM are formed in this order. As shown in Figure 12, between the outer periphery 23REM2 of the red light-emitting layer 23REM and the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, the outer periphery 23GEM2 of the green light-emitting layer 23GEM is provided so as to overlap with the outer periphery 23REM2 of the red light-emitting layer 23REM and the outer periphery 23BEM2 of the blue light-emitting layer 23BEM in a plan view.

[0079] As shown in Figure 11, the display device 1b further includes a green light-emitting element, which includes a green light-emitting layer 23GEM as a third functional layer, which is a patterned functional layer. In a plan view, one end of the green light-emitting layer 23GEM, i.e., the outer periphery 23GEM2 of the green light-emitting layer 23GEM, and the other end of the blue light-emitting layer 23BEM, i.e., the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, are superimposed. Furthermore, in the manufacturing method of the display device 1b, the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM are formed in this order. Therefore, the outer periphery 23REM2 of the red light-emitting layer 23REM is provided as a lower layer than the outer periphery 23REM2 of the green light-emitting layer 23GEM and the outer periphery 23BEM2 of the blue light-emitting layer 23BEM, so that in a plan view, it superimposes with the outer periphery 23REM2 of the green light-emitting layer 23GEM and the outer periphery 23BEM2 of the blue light-emitting layer 23BEM. Furthermore, the other end of the green light-emitting layer 23GEM, i.e., the outer periphery 23GEM2 of the green light-emitting layer 23GEM, and the other end of the red light-emitting layer 23REM, i.e., the outer periphery 23REM2 of the red light-emitting layer 23REM, are superimposed in a plan view. Moreover, in the manufacturing method of the display device 1b, the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer 23BEM are formed in this order. Therefore, the outer periphery 23BEM2 of the blue light-emitting layer 23BEM is provided as a layer above the outer periphery 23REM2 of the green light-emitting layer 23GEM and the outer periphery 23REM2 of the red light-emitting layer 23REM, so that it superimposes with the outer periphery 23REM2 of the green light-emitting layer 23GEM and the outer periphery 23REM2 of the red light-emitting layer 23REM in a plan view.

[0080] In the display device 1b shown in Figure 12, a laminate is provided in which the outer periphery portions of three different light-emitting layers are stacked so as to overlap in a plan view, with a non-light-emitting region in which the lower electrode 21 and the first charge transport layer 23CT1 are not in contact. The laminate can suppress leakage current that may occur in the non-light-emitting region, thereby realizing a display device 1b with improved luminous efficiency and a method for manufacturing the display device 1b with improved luminous efficiency.

[0081] [Embodiment 4] Figure 13 is a cross-sectional view showing the schematic configuration of the red light-emitting element 25R and the green light-emitting element 25G provided in the display device 1c of Embodiment 4. Figure 14 is a diagram showing an example of the process for forming the red light-emitting layer 23REM provided in the display device 1c of Embodiment 4. Figure 15 is a diagram showing an example of the process for forming the green light-emitting layer 23GEM provided in the display device 1c of Embodiment 4.

[0082] As shown in Figure 14, the red light-emitting layer 23REM provided in the display device 1c includes a charge-transporting material, which is a red light-emitting quantum dot RQD, and an insulating material, which is a matrix MR made of, for example, silicon oxide.

[0083] As shown in Figure 14, the manufacturing method of the display device 1c includes a first etching step in which a portion of the red light-emitting layer exposed from the first opening KK1 of the first resist film RES1 is removed using an etchant, followed by a second etching step (S1) in which the etchant is allowed to penetrate the remaining portion of the red light-emitting layer to form the outer periphery. In this embodiment, hydrofluoric acid was used as the etchant because it has a higher effect in removing quantum dots than in removing the silicon oxide matrix MR.

[0084] As shown in the upper diagram of Figure 14, in the first etching step described above, the etchant does not penetrate to the red light-emitting layer beneath the first resist film RES1. Therefore, the red light-emitting layer beneath the first resist film RES1 has the same configuration as the central part 23REM1 of the red light-emitting layer 23REM, which includes red light-emitting quantum dots RQD and a matrix MR. In the subsequent second etching step (S1) shown in Figure 14, the etchant penetrates to the red light-emitting layer beneath the first resist film RES1. At the edges of the red light-emitting layer, the outer peripheral part 23REM2 of the red light-emitting layer 23REM is formed, where the red light-emitting quantum dots RQD have been removed and voids VO have been formed. Meanwhile, the rest of the red light-emitting layer, except for the edges, becomes the central part 23REM1 of the red light-emitting layer 23REM, which includes red light-emitting quantum dots RQD and a matrix MR. Therefore, the outer peripheral portion 23REM2 of the red light-emitting layer 23REM contains a hollow matrix MR, and the porosity of the outer peripheral portion 23REM2 of the red light-emitting layer 23REM is higher than the porosity of the central portion 23REM1 of the red light-emitting layer 23REM.

[0085] As shown in Figure 15, the manufacturing method of the display device 1c includes a third etching step in which a portion of the green light-emitting layer exposed from the second opening KK2 of the second resist film RES2 is removed using an etchant, followed by a fourth etching step (S2) in which the etchant is allowed to penetrate the remaining portion of the green light-emitting layer to form the outer periphery. In this embodiment, hydrofluoric acid was used as the etchant because it has a higher effect in removing quantum dots than in removing the silicon oxide matrix MR.

[0086] As shown in the upper diagram of Figure 15, in the third etching step described above, the etchant has not penetrated to the green light-emitting layer beneath the second resist film RES2. Therefore, the green light-emitting layer beneath the second resist film RES2 has the same configuration as the central part 23GEM1 of the green light-emitting layer 23GEM, which includes green light-emitting quantum dots GQD and a matrix MR. In the subsequent fourth etching step (S2) shown in Figure 15, the etchant penetrates to the green light-emitting layer beneath the second resist film RES2. At the edges of the green light-emitting layer, the outer peripheral part 23GEM2 of the green light-emitting layer 23GEM is formed, where the green light-emitting quantum dots GQD have been removed and voids VO have been formed. Meanwhile, the parts of the green light-emitting layer other than the edges become the central part 23GEM1 of the green light-emitting layer 23GEM, which includes green light-emitting quantum dots GQD and a matrix MR. Therefore, the outer periphery 23GEM2 of the green light-emitting layer 23GEM contains a hollow matrix MR, and the porosity of the outer periphery 23GEM2 of the green light-emitting layer 23GEM is higher than the porosity of the central part 23GEM1 of the green light-emitting layer 23GEM.

[0087] Although not shown in the figures, the manufacturing method of the display device 1c may further include a sixth etching step, which is performed after a fifth etching step in which a portion of the blue light-emitting layer exposed from the opening of the third resist film is removed using an etchant, and the etchant is allowed to penetrate the remaining portion of the blue light-emitting layer to form the outer periphery. As the etchant, hydrofluoric acid can be used, which has a higher effect in removing quantum dots than in removing the silicon oxide matrix MR.

[0088] In this embodiment as well, as described above, the resist film may be left intact and a light-emitting layer of another color may be formed in order to protect the previously formed light-emitting layer.

[0089] In the display device 1c shown in Figure 13, a laminate is provided in which the outer periphery portions of the two different light-emitting layers described above are stacked so as to overlap in a plan view, with a non-light-emitting region in which the lower electrode 21 and the first charge transport layer 23CT1 are not in contact. The laminate can suppress leakage current that may occur in the non-light-emitting region, thereby realizing a display device 1c with improved luminous efficiency and a method for manufacturing the display device 1c with improved luminous efficiency.

[0090] [Embodiment 5] Figure 16 is a cross-sectional view showing the schematic configuration of the red light-emitting element 25R and the green light-emitting element 25G provided in the display device 1d of Embodiment 5.

[0091] As shown in Figure 16, each of the red light-emitting element 25R, green light-emitting element 25G, and blue light-emitting element (not shown) provided in the display device 1d is equipped with an island-shaped lower electrode 21 and a part of a common upper electrode 24. The first charge transport layer 23CT1 is provided closer to the island-shaped lower electrode 21 than to the common upper electrode 24.

[0092] In this embodiment, the lower electrode 21 is the anode and the upper electrode 24 is the cathode, so the first charge transport layer 23CT1 includes a hole transport material. The hole transport material may be, for example, copper oxide, nickel oxide, molybdenum oxide, or tungsten oxide.

[0093] When the lower electrode 21 is the cathode and the upper electrode 24 is the anode, the first charge transport layer 23CT1 includes an electron transport material. The electron transport material may be, for example, zinc oxide, magnesium zinc oxide, lithium zinc oxide, aluminum zinc oxide, or zinc sulfide.

[0094] As shown in Figure 16, the display device 1d includes not only a red light-emitting layer 23REM, a green light-emitting layer 23GEM, and a blue light-emitting layer as patterned functional layers, but also a first charge transport layer 23CT1. The patterning method for the first charge transport layer 23CT1 can be performed using the patterning methods for each color light-emitting layer described in Embodiments 1 to 3, so a detailed explanation is omitted here. As the etchant, an acidic etchant or a basic etchant can be used. Examples of acidic etchants include hydrochloric acid (HCl) and nitric acid (HNO). ３ ) and sulfuric acid (H ２ SO ４ Suitable etchants include, for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH).

[0095] As shown in Figure 16, the first charge transport layer 23CT1, which is a patterned functional layer, includes a central portion 23CTa and an outer peripheral portion 23CTb.

[0096] In the display device 1d shown in Figure 16, a non-luminescent region is provided where the lower electrode 21 and the first charge transport layer 23CT1 are not in contact, and a laminate is provided in which the outer periphery portions of three different luminescent layers and the outer periphery portion 23CTb of the first charge transport layer 23CT1 are stacked so as to overlap in a plan view. The laminate can suppress leakage current that may occur in the non-luminescent region, thereby realizing a display device 1d with improved luminous efficiency and a method for manufacturing the display device 1d with improved luminous efficiency.

[0097] In this embodiment, the case in which the red light-emitting layer 23REM, the green light-emitting layer 23GEM, the blue light-emitting layer, and the first charge transport layer 23CT1 are each patterned using a resist film has been described as an example, but the embodiment is not limited to this. For example, only the first charge transport layer 23CT1 may be patterned using a resist film, and one or more of the red light-emitting layer 23REM, the green light-emitting layer 23GEM, and the blue light-emitting layer may be formed by deposition using a metal mask or by an inkjet method.

[0098] As described above, in each embodiment of this disclosure, the example given is a case in which the light-emitting layer containing quantum dots includes a central portion and an outer peripheral portion that contains one or more elements identical to those contained in the central portion and has a different composition from that of the central portion. However, the invention is not limited to this, and similar effects can be obtained when the light-emitting layer containing an organic light-emitting material includes a central portion and an outer peripheral portion that contains one or more elements identical to those contained in the central portion and has a different composition from that of the central portion. Furthermore, as in Embodiment 5, when the charge transport layer includes a central portion and an outer peripheral portion that contains one or more elements identical to those contained in the central portion and has a different composition from that of the central portion, the light-emitting layer may include a conventional light-emitting layer containing quantum dots or an organic light-emitting material that does not include the central portion and the outer peripheral portion described above.

[0099] [Additional Notes] This disclosure is not limited to the embodiments described above, 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 this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0100] This disclosure can be used in a display device, a method for manufacturing a display device, and a method for forming multiple functional layers.

[0101] 1, 1a-1d Display device 2 Substrate 21 Lower electrode 22 Bank 23REM Red light-emitting layer 23REM' Red light-emitting layer coated over the entire surface 23REM1 Center 23REM2 Outer edge 23GEM Green light-emitting layer 23GEM' Green light-emitting layer coated over the entire surface 23GEM1 Center 23GEM2 Outer edge 23BEM Blue light-emitting layer 23BEM' Blue light-emitting layer coated over the entire surface 23BEM1 Center 23BEM2 Outer edge 23CT1 First charge transport layer 23CTa Center 23CTb Outer edge 23CT2 Second charge transport layer 24 Upper electrode 25R Red light-emitting element 25G Green light-emitting element 25B Blue light-emitting element RES1 First resist film KK1 First opening RES2 Second resist film KK2 Second aperture MR Matrix RQD Red Quantum Dot GQD Green Quantum Dot VO Gap PIX Pixel RSP Red Subpixel GSP Green Subpixel BSP Blue Subpixel DA Display Area NDA Frame Area

Claims

1. A display device comprising a light-emitting element including an anode, a cathode, and a patterned functional layer provided between the anode and the cathode, wherein the functional layer includes a central portion and an outer peripheral portion provided outside the central portion, and the outer peripheral portion contains one or more of the same elements as those contained in the central portion and has a composition different from that of the central portion.

2. The display device according to claim 1, wherein the outer periphery is a reaction product of an acid or base and a part of the functional layer.

3. The display device according to claim 1 or 2, wherein the same element included in the central portion and the outer peripheral portion is a metallic element, and the outer peripheral portion includes at least one of a halide of the metallic element, a sulfide of the metallic element, and a nitrate of the metallic element.

4. The display device according to any one of claims 1 to 3, wherein one of the anode and cathode provided in the light-emitting element is an island-shaped electrode, the other of the anode and cathode provided in the light-emitting element is part of a common electrode, and the functional layer is provided closer to the island-shaped electrode than to the common electrode.

5. The display device according to any one of claims 1 to 4, wherein the functional layer comprises a hole transporting material.

6. The display device according to claim 5, wherein the hole transporting material is one of copper oxide, nickel oxide, molybdenum oxide, or tungsten oxide.

7. The display device according to any one of claims 1 to 4, wherein the functional layer comprises an electron transport material.

8. The display device according to claim 7, wherein the electron transport material is any of zinc oxide, magnesium zinc oxide, lithium zinc oxide, aluminum zinc oxide, or zinc sulfide.

9. The display device according to any one of claims 1 to 4, wherein the functional layer is a light-emitting layer.

10. The display device according to claim 9, wherein the light-emitting layer includes quantum dots.

11. The display device according to claim 10, wherein the outer periphery comprises at least one of zinc halide, zinc sulfate, zinc nitrate, indium chloride, indium sulfate, and indium nitrate.

12. The display device according to any one of claims 1 to 11, wherein the functional layer comprises a charge transport material and an insulating material, the outer periphery comprises the hollow insulating material, and the porosity of the outer periphery of the functional layer is higher than the porosity of the central part of the functional layer.

13. The display device according to claim 12, wherein the insulating material is silicon oxide.

14. A display device according to any one of claims 1 to 13, comprising a plurality of the light-emitting elements, wherein the plurality of light-emitting elements include a first light-emitting element having a first functional layer as a functional layer, and a second light-emitting element having a second functional layer different from the first functional layer as a functional layer, and one end of the first functional layer and one end of the second functional layer overlap in a plan view.

15. A method for manufacturing a display device according to any one of claims 1 to 14, comprising: a step of forming the functional layer; a step of forming a resist film on the functional layer; a step of patterning the resist film to form openings in the resist film; a first etching step of removing a portion of the functional layer exposed from the openings; and a second etching step of using an etchant to allow the etchant to penetrate the remaining portion of the functional layer to form the outer periphery.

16. The method for manufacturing a display device according to claim 15, wherein in the first etching step, a portion of the functional layer exposed from the opening is removed by dry etching.

17. The method for manufacturing a display device according to claim 15, wherein in the first etching step, a portion of the functional layer exposed from the opening is removed by the etchant used in the second etching step.

18. The method for manufacturing a display device according to claim 17, wherein the first etching step and the second etching step are performed as a single etching step.

19. A method for forming multiple functional layers, comprising: forming a first functional layer; forming a first resist film on the first functional layer; patterning the first resist film to form a first opening in the first resist film; a first etching step to remove a portion of the first functional layer exposed from the first opening; a second etching step to allow a first etchant to penetrate the remaining portion of the first functional layer; heat treating the first resist film; and forming a second functional layer different from the first functional layer on the first opening and the first resist film.

20. A method for forming a plurality of functional layers according to claim 19, further comprising a step of exposing and developing the area around the first opening of the first resist film to widen the size of the first opening, which is performed between the second etching step and the step of heat-treating the first resist film.

21. A method for forming a plurality of functional layers according to claim 19 or 20, wherein in the first etching step, a portion of the first functional layer exposed from the first opening is removed by dry etching.

22. A method for forming a plurality of functional layers according to claim 19 or 20, wherein in the first etching step, a portion of the first functional layer exposed from the first opening is removed by the first etchant used in the second etching step.

23. A method for forming a plurality of functional layers according to claim 22, wherein the first etching step and the second etching step are performed as a single etching step.

24. A method for forming a plurality of functional layers according to any one of claims 19 to 23, comprising: a step of forming a second resist film on the second functional layer after the step of forming the second functional layer; a step of patterning the second resist film to form a second opening in the second resist film at a position different from the first opening; a third etching step of removing a portion of the second functional layer exposed from the second opening; and a fourth etching step of using a second etchant to allow the second etchant to penetrate the remaining portion of the second functional layer.

25. A method for forming a plurality of functional layers according to claim 24, wherein in the third etching step, a portion of the second functional layer exposed from the second opening is removed by dry etching.

26. A method for forming a plurality of functional layers according to claim 24, wherein in the third etching step, a portion of the second functional layer exposed from the second opening is removed by the second etchant used in the fourth etching step.

27. A method for forming a plurality of functional layers according to claim 26, wherein the third etching step and the fourth etching step are performed as a single etching step.

28. A method for forming a plurality of functional layers according to any one of claims 24 to 27, further comprising a step of peeling off the first resist film and the second resist film after the fourth etching step.

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