Display device and production method for display device

Abstract

A display device (1) comprises a substrate (2), a blue light-emitting element (3B), and a red light-emitting element (3R). The blue light-emitting element includes a first light-reflecting electrode (41B), a first blue light-emitting layer (45B), a first charge-generating layer (5B), a second blue light-emitting layer (63B), and a transparent electrode (66). The red light-emitting element includes a second light-reflecting electrode (41R), a second charge-generating layer (5R), a first red light-emitting layer (63R), and a transparent electrode. The distance (DR) between the second light-reflecting electrode and the second charge-generating layer is smaller than the distance (DB) between the first light-reflecting electrode and the first charge-generating layer.

Description

Display device and method for manufacturing the same

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

[0002] In a display device equipped with a light-emitting element such as an OLED, in order to improve the light-emitting efficiency of the light-emitting element, a technique is known in which, as described in Patent Document 1, two light-emitting layers are formed between electrodes, a charge-generating layer is formed between the two light-emitting layers, and light is extracted from each light-emitting layer.

[0003] Japanese Patent Application Publication No. 2019-208027

[0004] The light-emitting element described in Patent Document 1 has two light-emitting layers, and therefore tends to have an increased thickness in the stacking direction.

[0005] Here, a known technique for the display device is to form a cavity between the light-reflective electrodes of the light-emitting elements and design the cavity so that light from the light-emitting layer is reinforced within the cavity, thereby improving the light extraction efficiency of each light-emitting element, thereby improving the light-emitting efficiency, and narrowing the half-width of the light from each light-emitting element, thereby improving the display quality.

[0006] Generally, in a light-emitting element having a cavity, the distance between the light-reflective electrode and the light-emitting layer, and the distance between two light-reflective electrodes, are restricted within a predetermined range depending on the wavelength of the light emitted by the light-emitting layer. In particular, the longer the wavelength of the light emitted by the light-emitting layer, such as red light, the longer the above-mentioned distances become, and therefore the thickness of the light-emitting element in the stacking direction increases.

[0007] If a display device has even one light-emitting element that is thick in the stacking direction, the wavelength of the light emitted by the other light-emitting elements is short, in other words, even if the thickness of the other light-emitting elements in the stacking direction is relatively thin, the overall thickness of the display device will increase, leading to an increase in the length of the display device.

[0008] A display device according to one aspect of the present disclosure comprises a substrate, and blue and red light-emitting elements on the substrate, wherein the blue light-emitting elements include, in order from the substrate side, a first light-reflecting electrode, a first blue light-emitting layer, a first charge generation layer, a second blue light-emitting layer, and a transparent electrode, and the red light-emitting elements include, in order from the substrate side, a second light-reflecting electrode, a second charge generation layer, a first red light-emitting layer, and the transparent electrode, wherein the distance between the second light-reflecting electrode and the second charge generation layer is smaller than the distance between the first light-reflecting electrode and the first charge generation layer.

[0009] A manufacturing method of a display device according to one aspect of the present disclosure is a manufacturing method of a display device having a plurality of light-emitting elements on a substrate, and includes forming a first light-reflecting electrode and a second light-reflecting electrode on the substrate, forming a first blue light-emitting layer at least above the first light-reflecting electrode, forming a first charge generation layer above the first blue light-emitting layer, forming a second charge generation layer above the second light-reflecting electrode at a position where the distance between the second light-reflecting electrode and the second charge generation layer is smaller than the distance between the first light-reflecting electrode and the first charge generation layer, forming a second blue light-emitting layer at least above the first charge generation layer, forming a first red light-emitting layer above the second charge generation layer, and forming transparent electrodes above the second blue light-emitting layer and the first red light-emitting layer.

[0010] The thickness of the display device in the display direction is reduced while maintaining luminous efficiency or display quality, thereby making the display device smaller.

[0011] 1 is a schematic cross-sectional side view of a display device according to embodiment 1. FIG. 2 is a schematic plan view of a display device according to embodiment 1. FIG. 3 is a flowchart showing a manufacturing method of a display device according to embodiment 1. FIG. 4 is a flowchart showing a method of forming a first stack according to embodiment 1. FIG. 5 is a flowchart showing a method of forming a second stack according to embodiment 1. FIG. 6 is a schematic cross-sectional side view of a display device according to embodiment 2. FIG. 7 is a flowchart showing a method of forming a first stack according to embodiment 2. FIG. 8 is a flowchart showing a method of forming a second stack according to embodiment 2. FIG. 9 is a schematic cross-sectional side view of a display device according to embodiment 3. FIG. 10 is a flowchart showing a method of forming a first stack according to embodiment 3. FIG. 11 is a flowchart showing a method of forming a second stack according to embodiment 3. FIG. 12 is a schematic cross-sectional side view of a display device according to embodiment 4. FIG. 13 is a schematic cross-sectional side view of a display device according to embodiment 5. FIG. 14 is a schematic cross-sectional side view of a display device according to embodiment 6. FIG. 15 is a flowchart showing a method of forming a first stack according to embodiment 6. FIG. 16 is a flowchart showing a method of forming a second stack according to embodiment 6. FIG. 17 is a schematic cross-sectional side view of a display device according to embodiment 7. FIG. 18 is a schematic cross-sectional side view of a display device according to embodiment 8. FIG. 19 is a schematic cross-sectional side view of a display device according to embodiment 9.

[0012] [Embodiment 1] <Display Device: Overview> Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that in each drawing, similar components are denoted by the same reference numerals and description thereof will be omitted.

[0013] 2 is a schematic plan view of a display device according to this embodiment. The display device 1 is a device that can be used, for example, as a display for a television or a smartphone. The display device 1 includes a display unit DA and a frame unit NA formed around the periphery of the display unit DA. The display device 1 displays an image on the display unit DA by controlling light emission from each of a plurality of light-emitting elements (described later) formed in the display unit DA. Drivers and the like for driving each of the plurality of light-emitting elements of the display unit DA may be formed in the frame unit NA.

[0014] The structure of the display unit DA of the display device 1 according to this embodiment will be described in more detail with reference to FIG. 1. FIG. 1 is a schematic side cross-sectional view of the display device according to this embodiment, taken along the line II shown in FIG. 2. In particular, FIG. 1 is a plan view of the display device 1 according to this embodiment, showing a cross section passing through a blue subpixel SPB, a red subpixel SPR, and a green subpixel SPG, which will be described later. In the present disclosure, the direction from a substrate 2 to a light-emitting element 3, which will be described later, of the display device 1 may be referred to as "upper," and the opposite direction may be referred to as "lower."

[0015] 1 , the display device 1 includes a substrate 2. For example, the substrate 2 may be a rigid substrate such as a glass substrate, or a flexible substrate such as a film substrate. When the substrate 2 is a flexible substrate, the display device 1 may be a flexible device.

[0016] The substrate 2 may be formed at a position overlapping the display section DA and the frame section NA in a plan view of the display device 1. In other words, the substrate 2 may be formed across the display section DA and the frame section NA in a plan view of the display device 1. The top surface of the substrate 2 may be substantially parallel to the display surface of the display device 1; in other words, the plan view of the substrate 2 may be substantially the same as the plan view of the display device 1.

[0017] In a plan view of the display device 1, a blue subpixel SPB, a red subpixel SPR, and a green subpixel SPG are formed in the display area DA of the substrate 2. A pixel circuit including a transistor such as a TFT (not shown) may be formed in each subpixel on the substrate 2. The display device 1 may individually control light-emitting elements (described later) by individually controlling each pixel circuit via a driver (not shown) formed in the frame area NA of the substrate 2.

[0018] The substrate 2 may be manufactured by forming circuits such as transistors and drivers on a glass substrate. Alternatively, the glass substrate may then be peeled off and replaced with a film substrate or the like, thereby making the substrate 2 a flexible substrate. In addition, in the manufacturing process of the display device 1, a plurality of light-emitting elements, which will be described later, may be formed on a large-sized glass substrate, and then the glass substrate may be cut into a plurality of substrates 2, thereby manufacturing a plurality of display devices 1.

[0019] <Display Device: Light-Emitting Element: Overview> The display device 1 includes light-emitting elements 3 on a substrate 2. The light-emitting elements 3 include a blue light-emitting element 3B, a red light-emitting element 3R, and a green light-emitting element 3G. The blue light-emitting element 3B is formed in the blue sub-pixel SPB, the red light-emitting element 3R in the red sub-pixel SPR, and the green light-emitting element 3G in the green sub-pixel SPG.

[0020] The blue light-emitting element 3B includes, in order from the substrate 2 side, a first stacked body 4B, a charge generating layer 5B serving as a first charge generating layer, and a second stacked body 6B. The first stacked body 4B includes, in order from the substrate 2 side, an anode 41B serving as a first light-reflecting electrode, a hole injection layer 42, a hole transport layer 43, a blue electron blocking layer 44B, a blue light-emitting layer 45B serving as a first blue light-emitting layer, a hole blocking layer 46, and an electron transport layer 47. The charge generating layer 5B includes, in order from the first stacked body 4B side, an electron generating layer 51 and a hole generating layer 52. The second stacked body 6B includes, in order from the charge generating layer 5B side, a hole transport layer 61, a blue electron blocking layer 62B, a blue light-emitting layer 63B serving as a second blue light-emitting layer, a hole blocking layer 64, an electron transport layer 65, and a cathode 66 serving as a transparent electrode.

[0021] The red light-emitting element 3R includes, in order from the substrate 2 side, a first stacked body 4R, a charge generation layer 5R which is a second charge generation layer, and a second stacked body 6R. The first stacked body 4R includes, in order from the substrate 2 side, an anode 41R which is a second light-reflecting electrode, a hole injection layer 42, a hole transport layer 43, a hole blocking layer 46, and an electron transport layer 47. The charge generation layer 5R includes, in order from the first stacked body 4R side, an electron generation layer 51 and a hole generation layer 52. The second stacked body 6R includes, in order from the charge generation layer 5R side, a hole transport layer 61, a red light-emitting layer 63R which is a first red light-emitting layer, a hole blocking layer 64, an electron transport layer 65, and a cathode 66 which is a transparent electrode.

[0022] The green light-emitting element 3G includes, in order from the substrate 2 side, a first stack 4G, a charge generation layer 5G which is a third charge generation layer, and a second stack 6G. The first stack 4G includes, in order from the substrate 2 side, an anode 41G which is a third light-reflecting electrode, a hole injection layer 42, a hole transport layer 43, a green electron blocking layer 44G, a green light-emitting layer 45G which is a first green light-emitting layer, a hole blocking layer 46, and an electron transport layer 47. The charge generation layer 5G includes, in order from the first stack 4G side, an electron generation layer 51 and a hole generation layer 52. The second stack 6G includes, in order from the charge generation layer 5G side, a hole transport layer 61, a green electron blocking layer 62G, a green light-emitting layer 63G which is a second green light-emitting layer, a hole blocking layer 64, an electron transport layer 65, and a cathode 66 which is a transparent electrode.

[0023] <Display Device: Light-Emitting Element: Common Layer> In this embodiment, the hole injection layer 42, the hole transport layer 43, the hole blocking layer 46, the electron transport layer 47, the electron generating layer 51, the hole generating layer 52, the hole transport layer 61, the hole blocking layer 64, the electron transport layer 65, and the cathode 66 are common layers. In this specification, a common layer refers to a layer that is formed in common in all of the blue subpixel SPB, the red subpixel SPR, and the green subpixel SPG and that is made of the same material. Therefore, each common layer is included in all of the blue light-emitting element 3B, the red light-emitting element 3R, and the green light-emitting element 3G, and each common layer is made of the same material.

[0024] Here, the common layer may be located at approximately the same distance from the substrate 2 in each subpixel, like the hole injection layer 42 and the hole transport layer 43 shown in Fig. 1. In this case, these common layers may be continuous layers.

[0025] On the other hand, the distance of the common layer from the substrate 2 may vary between subpixels, like the hole blocking layer 46, electron transport layer 47, electron generating layer 51, hole generating layer 52, hole transport layer 61, hole blocking layer 64, electron transport layer 65, and cathode 66 shown in Fig. 1. In this case, these common layers may be discontinuous in parts, or may be continuous in parts (not shown) between the subpixels.

[0026] In particular, the cathode 66 may be formed continuously between some of the sub-pixels, although the distance from the substrate 2 differs between the sub-pixels. In this case, the cathode 66 may be at approximately the same potential in all of the sub-pixels. However, the cathode 66 may also be a separate layer.

[0027] <Display Device: Light-Emitting Element: Anode and Cathode> In this embodiment, the anodes 41B, 41R, and 41G are formed in the blue subpixel SPB, the red subpixel SPR, and the green subpixel SPG, respectively, and are electrically connected to the pixel circuits formed in the respective subpixels. Therefore, the voltages of the anodes 41B, 41R, and 41G are individually controlled. In particular, the display device 1 controls the anodes 41B, 41R, and 41G, respectively, to generate a potential difference between each anode 41 and the cathode 66, thereby injecting holes from each anode toward the cathode 66.

[0028] The anode 41B, the anode 41R, and the anode 41G each include a light-reflecting electrode. The light-reflecting electrode may include, for example, a metal material with high reflectivity for visible light, and the metal material may be, for example, Al, Ag, Cu, or Au alone or an alloy thereof. The anode 41B, the anode 41R, and the anode 41G may also include a transparent electrode that transmits visible light. As the transparent electrode, for example, a thin film of a metal material that is thin enough to transmit visible light may be used, or a thin film of ITO, InZnO, SnO, or the like may be used. ２ Alternatively, a transparent conductor such as FTO may be used.

[0029] In addition, the display device 1 may further include a bank (not shown) formed between a plurality of sub-pixels on the substrate 2, and the anodes 41B, 41R, and 41G may be divided into sub-pixels by the bank.

[0030] The cathode 66 is formed, for example, in common to the plurality of sub-pixels as described above. The cathode 66 is, for example, a transparent electrode as described above. Therefore, the light-emitting element 3 according to this embodiment is a top-emission light-emitting element because it includes the anode 41B, anode 41R, and anode 41G, each including a reflective electrode, on the substrate 2 side, and the cathode 66, which is a transmissive electrode, on the side opposite the substrate 2.

[0031] The cathode 66 does not need to transmit all of the incident light, but may transmit a portion of the incident light. In particular, the cathode 66 may be a semi-reflective electrode that transmits a portion of the incident light and reflects at least a portion of the remaining incident light. Here, the semi-reflective electrode is not limited to an electrode that reflects exactly 50% of the incident light, as long as it reflects a portion of the incident light. By providing the light-emitting element 3 with a light-emitting layer between the anode, which is a semi-reflective electrode, and the cathode, which is a semi-reflective electrode, the display device 1 can make the light-emitting element 3 function as a cavity. Therefore, with the above configuration, the display device 1 improves the light extraction efficiency from the light-emitting element 3.

[0032] In this embodiment, a predetermined voltage is applied to the cathode 66 regardless of the potential of each anode. In particular, the display device 1 controls each of the anodes 41B, 41R, and 41G to generate a potential difference between each anode 41 and the cathode 66, thereby injecting electrons from the cathode 66 toward each anode.

[0033] <Display Device: Light-Emitting Element: Charge Generation Layer> Charge generation layer 5B, charge generation layer 5R, and charge generation layer 5G are layers that generate charges in response to application of voltage to anode 41B, anode 41R, and anode 41G, respectively. In particular, application of a voltage between each anode and cathode 66 causes electrons to be injected from electron generation layer 51 toward each anode, and holes to be injected from hole generation layer 52 toward cathode 66.

[0034] The electron generating layer 51 may include an n-type doped metal or organic material. For example, the metal may be selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, and Yb. Conventional materials may be used as the n-type dopant and host for the n-type doped organic material. For example, the n-type dopant may be an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound. More specifically, the n-type dopant may be selected from the group consisting of Cs, K, Rb, Mg, Na, Ca, Sr, Eu, and Yb. The metal may also be an alloy of an alkali metal, an alkaline earth metal, or a rare earth metal with another metal. In particular, the metal may include lithium or ytterbium, or a combination of these metals. Specific examples of metals that can be used as the alloy material include, but are not limited to, zinc, cadmium, and bismuth. The host material may be selected from the group consisting of compounds having a nitrogen-containing aromatic heterocycle, such as phenanthroline derivatives and oligopyridine derivatives, tris(8-hydroxyquinoline)aluminum, triazine, hydroxyquinoline derivatives, benzazole derivatives, and silole derivatives. Compounds having a phosphine oxide group can also be used as the host material.

[0035] The hole generating layer 52 may include a p-type doped metal or organic material. The metal may be one metal selected from the group consisting of Al, Cu, Fe, Pb, Zn, Au, Pt, W, In, Mo, Ni, and Ti, or an alloy containing two or more of these metals. Conventional p-type dopants and hosts may be used in the p-type doped organic material. For example, the p-type dopant may be tetrafluorene-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), a tetracyanoquinodimethane derivative, a radialene derivative, iodine, or FeCl. ３ , FeF ３ , and SbCl ５In particular, the p-type dopant may be selected from radialene derivatives. The host may be selected from the group consisting of N,N'-di(naphthalen-1-yl)-N,N-diphenyl-benzidine (NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1-biphenyl-4,4'-diamine (TPD), and N,N',N'-tetranaphthyl-benzidine (TNB), and arylamine derivatives.

[0036] Therefore, in the blue light-emitting element 3B, when the anode 41B is driven, holes from the anode 41B and electrons from the electron generating layer 51 are injected into each layer of the first stack 4B. Also, in the blue light-emitting element 3B, when the anode 41B is driven, electrons from the cathode 66 and holes from the hole generating layer 52 are injected into each layer of the second stack 6B.

[0037] Furthermore, in the red light-emitting element 3R, driving the anode 41R causes holes from the anode 41R and electrons from the electron generating layer 51 to be injected into each layer of the first stack 4R. Also, in the red light-emitting element 3R, driving the anode 41R causes electrons from the cathode 66 and holes from the hole generating layer 52 to be injected into each layer of the second stack 6R.

[0038] Additionally, in the green light-emitting element 3G, driving the anode 41G causes holes from the anode 41G and electrons from the electron generating layer 51 to be injected into each layer of the first stack 4G. Also, in the green light-emitting element 3G, driving the anode 41G causes electrons from the cathode 66 and holes from the hole generating layer 52 to be injected into each layer of the second stack 6G.

[0039] <Display Device: Light-Emitting Element: Charge Transport Layer> The hole injection layer 42 is a layer into which holes generated by applying a voltage to the anode 41B, the anode 41R, and the anode 41G are injected. The hole injection layer 42 may contain a conventionally known material having hole transport properties. Examples of materials for the hole injection layer 42 include triarylamine-based organic compounds. Examples of materials for the hole injection layer 42 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). Note that these materials may be used alone or in combination of two or more.

[0040] The hole transport layer 43 is a layer that transports holes injected from the anode 41 into the hole injection layer 42 to the cathode 66. The hole transport layer 43 may contain a material having hole transport properties that has been conventionally used in light-emitting elements and the like. Examples of materials for the hole transport layer 43 include triarylamine-based organic compounds. Examples of materials for the hole transport layer 43 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"), polyvinylcarbazole (abbreviated as "PVK"), and the like. These materials may be used alone or in combination of two or more.

[0041] The hole blocking layer 46 is a layer that reduces the number of holes transported from each anode to the light-emitting layer of each first stacked body (described later) from being further transported toward the cathode 66. For example, the hole blocking layer 46 may contain a material having electron transport properties that increases the barrier to hole injection from the light-emitting layer of each first stacked body to the hole blocking layer 46. The hole blocking layer 46 may contain, for example, an oxadiazole-based compound.

[0042] The electron transport layer 47 is a layer that transports electrons injected from the electron generating layer 51 to the anode side. The electron transport layer 47 may contain a material having electron transport properties that has been conventionally used in light-emitting devices and the like. Examples of materials for the electron transport layer 47 include oxadiazole-based compounds. Examples of materials for the hole transport layer 43 include 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (abbreviated as "TPBi"), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (abbreviated as "BCP"), and 4,7-diphenyl-1,10-phenanthroline (abbreviated as "Bphen"). These materials may also be used alone or in combination of two or more.

[0043] The hole transport layer 61 is a layer that transports holes injected from the hole generating layer 52 to the cathode 66 side. The hole transport layer 61 may have the same material as the hole transport layer 43. The hole blocking layer 64 is a layer that reduces the number of holes transported from the hole generating layer 52 to the light-emitting layer of each second stack (described later) that are further transported to the cathode 66 side. The hole blocking layer 64 may have the same material as the hole blocking layer 46. The electron transport layer 65 is a layer that transports electrons injected from the cathode 66 to each anode side. The electron transport layer 65 may have the same material as the electron transport layer 47.

[0044] <Display Device: Light-Emitting Element: Light-Emitting Layer> The blue light-emitting layer 45B, the blue light-emitting layer 63B, the red light-emitting layer 63R, the green light-emitting layer 45G, and the green light-emitting layer 63G contain light-emitting materials that emit light by excitons generated by the recombination of injected holes and electrons. In particular, the blue light-emitting layer 45B and the blue light-emitting layer 63B emit blue light, the red light-emitting layer 63R emits red light, and the green light-emitting layer 45G and the green light-emitting layer 63G emit green light.

[0045] In this embodiment, blue light refers to light having a central emission wavelength in a wavelength band of, for example, 380 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.

[0046] The blue light-emitting layer 45B and the green light-emitting layer 45G are each included in a first stack, and emit light upon injection of holes from the respective anodes and electrons from the electron generating layer 51. The blue light-emitting layer 63B, the red light-emitting layer 63R, and the green light-emitting layer 63G are each included in a second stack, and emit light upon injection of holes from the hole generating layer 52 and electrons from the cathode 66.

[0047] Of the light from each light-emitting layer, the light that is emitted to the cathode 66 side passes through each layer including the cathode 66 and is extracted to the outside of the light-emitting element 3. Furthermore, of the light from each light-emitting layer, the light that is emitted to the anode side is reflected by each anode and is extracted to the outside of the light-emitting element 3 from the cathode 66 side.

[0048] As a result, blue light, red light, and green light are extracted from the blue light emitting element 3B, red light emitting element 3R, and green light emitting element 3G, respectively, through the cathode 66. The display device 1 individually controls the light emission of the blue light emitting element 3B, red light emitting element 3R, and green light emitting element 3G by applying voltages to the respective anodes, thereby extracting blue light, red light, and green light from each sub-pixel and performing display.

[0049] The blue light-emitting layer 45B, the blue light-emitting layer 63B, the red light-emitting layer 63R, the green light-emitting layer 45G, and the green light-emitting layer 63G may contain light-emitting materials that can be formed by vacuum deposition, as described below. Examples of materials that can be formed by vacuum deposition for the blue light-emitting layer 45B and the blue light-emitting layer 63B include a material in which an anthracene compound is used as a host material and a blue fluorescent dye is doped as a guest material. Examples of materials that can be formed by vacuum deposition for the red light-emitting layer 63R include polymer light-emitting materials such as polyfluorene-based polymer derivatives, (poly)paraphenylenevinylene derivatives, polyphenylene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, perylene-based dyes, coumarin-based dyes, and rhodamine-based dyes. Examples of materials that can be formed by vacuum deposition for the green light-emitting layer 45G and the green light-emitting layer 63G include the same materials as those for the red light-emitting layer 63R. The blue light-emitting layer 45B, the blue light-emitting layer 63B, the red light-emitting layer 63R, the green light-emitting layer 45G, and the green light-emitting layer 63G may contain an organic light-emitting material such as the materials described above.

[0050] More specifically, the blue light-emitting layer 45B and the blue light-emitting layer 63B may include, for example, DPVBi (4,4'-bis(2,2-diphenylvinyl)biphenyl) as a light-emitting dopant, and the blue light-emitting layer 45B and the blue light-emitting layer 63B may include, for example, adamantane anthracene as a host material.

[0051] The green light-emitting layer 45G and the green light-emitting layer 63G may contain, for example, Ir(ppy)3 (tris(2-phenylpyridinato)iridium(III)) as a light-emitting dopant, and the green light-emitting layer 45G and the green light-emitting layer 63G may contain, for example, CBP (4,4'-di(N-carbazolyl)biphenyl) as a host material.

[0052] The red light-emitting layer 63R may include, for example, Btp2Ir(acac) (bis-(3-(2-(2-pyridyl)benzothienyl)mono-acetylacetonate)iridium(III)) as a light-emitting dopant. The red light-emitting layer 63R may also include, for example, CDBP (4,4'-bis(carbazol-9-yl)-2,2'-dimethylbiphenyl) as a host material.

[0053] However, the light-emitting material included in each of the light-emitting layers is not limited to the above materials. For example, the light-emitting material may include light-emitting semiconductor nanoparticles, in other words, quantum dots. Generally, light from quantum dots has a narrow spectrum due to the quantum confinement effect. Therefore, a light-emitting element including quantum dots in its light-emitting layer can emit light with a relatively deep chromaticity.

[0054] When the light-emitting layer contains quantum dots as a light-emitting material, the quantum dots may include at least one selected from the group consisting of, for example, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, GaAs, GaP, InN, InAs, InP, and InSb. The quantum dots may have a core / shell structure, etc. When the light-emitting layer contains quantum dots as a light-emitting material, the light-emitting layer may be formed by applying a solution in which the quantum dots are dispersed and drying the solution.

[0055] The blue light-emitting element 3B obtains blue light from both the blue light-emitting layer 45B of the first stacked body 4B and the blue light-emitting layer 63B of the second stacked body 6B. The green light-emitting element 3G obtains green light from both the green light-emitting layer 45G of the first stacked body 4G and the green light-emitting layer 63G of the second stacked body 6G. This allows the display device 1 to more efficiently extract blue light from the blue sub-pixel SPB and green light from the green sub-pixel SPG.

[0056] <Display Device: Light-Emitting Element: Electron Blocking Layer> The blue electron blocking layer 44B, blue electron blocking layer 62B, green electron blocking layer 44G, and green electron blocking layer 62G function to reduce electron injection from each light-emitting layer toward each anode. This prevents a decrease in electron concentration in each light-emitting layer or reduces deterioration of each layer on the anode side of each light-emitting layer. In particular, the blue electron blocking layer 44B is included in the first stack 4B and serves as an electron blocking layer for the blue light-emitting layer 45B, and the blue electron blocking layer 62B is included in the second stack 6B and serves as an electron blocking layer for the blue light-emitting layer 63B. The green electron blocking layer 44G is included in the first stack 4G and serves as an electron blocking layer for the green light-emitting layer 45G, and the green electron blocking layer 62G is included in the second stack 6G and serves as an electron blocking layer for the green light-emitting layer 63G. Note that in this embodiment, the red light-emitting element 3R does not necessarily have to include an electron blocking layer.

[0057] The blue electron blocking layer 44B, the blue electron blocking layer 62B, the green electron blocking layer 44G, and the green electron blocking layer 62G may contain a material having hole transport properties, for example, the same material as the hole transport layer 43 or the hole transport layer 61.

[0058] <Display Device: Light-Emitting Element: Relationship Between Film Thickness and Optical Path Length> Here, the distance between each anode including a reflective electrode and the light-emitting layer in this embodiment will be considered. As described above, light emitted from each light-emitting layer toward each anode is reflected by the anode and extracted from the cathode 66 side. For this reason, from the perspective of improving the light extraction efficiency from the light-emitting element in the front direction of the light-emitting element, a cavity is often configured so that the light emitted from the light-emitting layer and the light reflected by the anode constructively interact with each other. In this embodiment, when the following formula (1) is satisfied in a certain light-emitting element, the light emitted from the light-emitting layer and the light reflected by the anode constructively interact with each other. In other words, when the following formula (1), which is the condition for forming a cavity in the light-emitting element, is satisfied, the light extraction efficiency from the light-emitting element in the front direction of the light-emitting element is improved.

[0059] (2m-1)λ / 4=Σnd (1) In the above formula (1), m is an integer equal to or greater than 1, and therefore 2m-1 is an odd number. λ is the wavelength of light emitted by the light-emitting layer, and n and d are the absolute refractive index and film thickness of each layer between the surface of the anode on the side of the light-emitting layer and the light-emitting portion of the light-emitting layer. Therefore, Σnd corresponds to the optical path length of light propagating from the surface of the anode on the side of the cathode 66 to the light-emitting portion of the light-emitting layer.

[0060] Therefore, in each light-emitting element of this embodiment, the light extraction efficiency from the light-emitting element is improved when the optical path length of light propagating from the surface of the anode on the cathode 66 side to any part of the light-emitting layer is an odd multiple of a quarter of the wavelength of the light emitted by the light-emitting layer.

[0061] 1, the optical path length of light propagating from the surface of anode 41B on the cathode 66 side to any part of blue light-emitting layer 45B is denoted as LB1, and the optical path length of light propagating to any part of blue light-emitting layer 63B is denoted as LB2. In this embodiment, optical path length LB1 is three-quarters the wavelength of the blue light emitted by blue light-emitting layer 45B, and optical path length LB2 is five-quarters the wavelength of the blue light emitted by blue light-emitting layer 45B.

[0062] 1, the optical path length of light propagating from the surface of the anode 41R on the cathode 66 side to any part of the red light-emitting layer 63R is denoted as LR1. In this embodiment, the optical path length LR1 is three-quarters the wavelength of the red light emitted by the red light-emitting layer 45R.

[0063] 1 , the optical path length of light propagating from the surface of anode 41G on the cathode 66 side to any part of green light-emitting layer 45G is denoted as LG1, and the optical path length of light propagating to any part of green light-emitting layer 63G is denoted as LG2. In this embodiment, the optical path length LG1 is three-quarters the wavelength of the green light emitted by green light-emitting layer 45G, and the optical path length LG2 is five-quarters the wavelength of the green light emitted by green light-emitting layer 45G.

[0064] By setting each optical path length as described above, the above formula (1) is established for the blue light-emitting element 3B, the red light-emitting element 3R, and the green light-emitting element 3G, and therefore the display device 1 can more efficiently extract light from each light-emitting layer from the light-emitting element 3. The above-described optical path lengths in the light-emitting element 3 can be adjusted by appropriately setting the distance from each light-emitting layer to each anode. From the viewpoint of achieving both the light extraction efficiency from the light-emitting element 3 and thinning the light-emitting element 3, the display device 1 may achieve each of the above optical path lengths by adjusting the film thickness of some layers of the light-emitting element 3 and minimizing the film thickness of other layers. For example, the minimum film thickness may be the minimum film thickness that ensures sufficient film-formability for each layer.

[0065] Specifically, the optical path length LR1 may be appropriately adjusted by the film thickness of the hole transport layer 43. In this embodiment, the film thickness of the hole transport layer 43 may be determined so that the optical path length LR1 satisfies the above-described condition while the film thickness of each layer of the red light emitting element 3R, excluding the hole transport layer 43, is set to a minimum limit.

[0066] The thicknesses of blue electron blocking layer 44B, blue electron blocking layer 62B, green electron blocking layer 44G, and green electron blocking layer 62G may be determined so that optical path length LB1, optical path length LB2, optical path length LG1, and optical path length LG2 satisfy the above-mentioned conditions. Here, the thickness of hole transport layer 43 may be determined so that optical path length LR1 satisfies the above-mentioned condition, and in blue light-emitting element 3B and green light-emitting element 3G, the thicknesses of each layer other than each electron blocking layer and hole transport layer 43 may be set to a minimum thickness.

[0067] <Display Device: Supplementary Notes> The light-emitting element 3 according to this embodiment is not limited to the configuration described above. For example, the light-emitting element 3 may include a hole injection layer made of the same material as the hole injection layer 42 between the hole generation layer 52 and the hole transport layer 61. The light-emitting element 3 may also include an electron injection layer between the electron transport layer 47 and the electron generation layer 51 or between the electron transport layer 65 and the cathode 66.

[0068] The display device 1 according to this embodiment is not limited to the above-described configuration. For example, the display device 1 may include a capping layer in contact with the cathode 66 of the light-emitting element 3. The display device 1 may also include a sealing layer that seals the light-emitting element 3 between the substrate 2. Furthermore, the display device 1 may include a functional panel such as a touch panel on the light-emitting element 3.

[0069] <Thinning of Light-Emitting Elements> In this embodiment, the blue light-emitting element 3B and the green light-emitting element 3G each include two light-emitting layers as described above. On the other hand, the red light-emitting element 3R includes only the red light-emitting layer 63R of the second stack 6B as the light-emitting layer. Therefore, the first stack 4R of the red light-emitting element 3R is thinner than the first stack 4B of the blue light-emitting element 3B and the first stack 4G of the green light-emitting element 3G.

[0070] 1 , the distance between the anode 41B and the charge generation layer 5B, in other words, the distance from the surface of the anode 41B on the cathode 66 side to the surface of the charge generation layer 5B on the anode 41B side, is defined as DB. Also, the distance between the anode 41R and the charge generation layer 5R, in other words, the distance from the surface of the anode 41R on the cathode 66 side to the surface of the charge generation layer 5R on the anode 41R side, is defined as DR. In this embodiment, the distance DR is smaller than the distance DB.

[0071] Therefore, in this embodiment, the total film thickness of the red light emitting element 3R is smaller than the total film thickness of the blue light emitting element 3B and the green light emitting element 3G. Therefore, the display device 1 according to this embodiment can reduce the total film thickness of the red light emitting element 3R while improving the extraction efficiency of blue light and green light from the light emitting element 3.

[0072] In particular, suppose that the red light-emitting element 3R also includes a red light-emitting layer in the first stack 4R, and the optical path lengths of light propagating from the surface of the anode 41R to each of the two red light-emitting layers are set to satisfy the above formula (1). In this case, if the optical path length related to the red light-emitting layer of the first stack 4R is set to three-quarters of the length of the red light, the optical path length related to the red light-emitting layer 63R of the second stack 6R needs to be five-quarters of the length of the red light. In this case, because the wavelength of red light is longer than the wavelengths of blue and green light, the total film thickness of the red light-emitting element 3R is greater than the total film thickness of the blue light-emitting element 3B and the green light-emitting element 3G. Therefore, a display device 1 that includes only the red light-emitting layer 63R as the light-emitting layer located in the red subpixel SPR and reduces the total film thickness of the red light-emitting element 3R can efficiently reduce the total film thickness and achieve miniaturization.

[0073] When the display device 1 is flexible, for example when the substrate 2 is a film substrate, the flexibility of the display device 1 is further improved by thinning the display device 1. Furthermore, by reducing the total film thickness of the red light-emitting element 3R, the overall electrical resistance of the red light-emitting element 3R is reduced, and the same brightness can be obtained from the red light-emitting element 3R at a lower current. Therefore, the red light-emitting element 3R can be driven at a lower current to perform display, and the display device 1 improves the reliability of the red light-emitting element 3R and achieves power saving.

[0074] <Display Device Manufacturing Method: Overview and Preparation of Substrate> A method for manufacturing the display device 1 according to this embodiment will be described below. Fig. 3 is a flowchart showing a method for manufacturing the display device 1 according to this embodiment.

[0075] In the manufacturing method of the display device 1 according to this embodiment, first, a substrate 2 is prepared (step S1). The substrate 2 may be prepared, for example, by cutting a glass substrate, a film substrate, or the like into a predetermined shape. Alternatively, a large substrate 2 may be prepared, and after each process is performed, the substrate 2 may be cut out to separate the display devices 1. Step S1 may include a step of forming pixel circuits at positions corresponding to each sub-pixel of the substrate 2, and may also include a step of forming drivers and the like on the substrate 2.

[0076] <Display Device Manufacturing Method: Formation of First Stack> Next, the first stack 4B, first stack 4R, and first stack 4G of the light emitting element 3 are formed on the substrate 2 (step S2). The process of forming the first stack 4B, first stack 4R, and first stack 4G according to this embodiment will be described in more detail with reference to Fig. 4. Fig. 4 is a flowchart showing the method of forming the first stack 4B, first stack 4R, and first stack 4G according to this embodiment.

[0077] In the process of forming the first stacked body 4B, the first stacked body 4R, and the first stacked body 4G, the anodes 41B, 41R, and 41G are formed first (step S20). The anodes 41B, 41R, and 41G may be formed, for example, by forming a thin film of a metal material or the like on the substrate 2 by vacuum deposition, sputtering, or the like, and then patterning the thin film for each subpixel by dry etching or the like.

[0078] In step S20, banks may be formed to separate the anodes 41B, 41R, and 41G. In the bank formation process, the banks may be formed only at positions that separate the anodes 41B, 41R, and 41G by vacuum deposition using a metal mask or the like having openings at positions that overlap with each subpixel in a plan view. Alternatively, in the bank formation process, for example, a photosensitive resin material may be applied to form a film on the upper surfaces of the substrate 2, the anodes 41B, 41R, and 41G. Next, the banks may be formed by forming openings at positions that overlap with the anodes 41B, 41R, and 41G in the substrate 2 by photolithography or the like in the plan view.

[0079] Next, the hole injection layer 42 is formed on the anode 41B, the anode 41R, and the anode 41G (step S21). The hole injection layer 42 may be formed by, for example, a vacuum deposition method using the above-mentioned material having hole transport properties as a deposition source. Alternatively, the hole injection layer 42 may be formed by applying the above-mentioned material having hole transport properties over multiple subpixels using an inkjet method, spin coating, or the like.

[0080] Next, a hole transport layer 43 is formed on the hole injection layer 42 (step S22). The hole transport layer 43 may be formed, for example, by vacuum deposition using the above-mentioned material having hole transport properties as a deposition source. Alternatively, the hole transport layer 43 may be formed by applying the above-mentioned material having hole transport properties over multiple subpixels using an inkjet method, spin coating, or the like. In step S22, the thickness of the hole transport layer 43 to be formed may be adjusted by adjusting the thickness of the applied material, for example, so that the optical path length LR1 of the red light-emitting element 3R after formation is three-quarters the wavelength of red light emitted by the red light-emitting layer 63R.

[0081] Next, a green electron blocking layer 44G is formed on the hole transport layer 43 at a position that overlaps with the green subpixel SPG in a planar view of the substrate 2 (step S23). In step S23, a metal mask or the like having openings only at positions that overlap with the green subpixel SPG in a planar view of the substrate 2 is placed on the hole transport layer 43, and the green electron blocking layer 44G is formed by depositing the above-mentioned material by vacuum deposition. Alternatively, in step S23, a coating material obtained by mixing a material having hole transport properties described above with a photosensitive resin may be applied to the hole transport layer 43 over multiple subpixels. Next, the green electron blocking layer 44G may be formed by patterning a thin film of the coating material using photolithography or the like. Alternatively, the green electron blocking layer 44G may be formed by applying the coating material only at positions that overlap with the substrate 2 in a planar view using an inkjet method or the like.

[0082] In step S23, the thickness of the green electron blocking layer 44G to be formed may be adjusted by adjusting the film thickness of the applied material, etc., so that the optical path length LG1 of the green light-emitting element 3G after formation is three-quarters of the wavelength of the green light emitted by the green light-emitting layer 45G.

[0083] Next, green light-emitting layer 45G is formed on green electron blocking layer 44G (step S24). Step S24 may be performed by the same method as step S23, except that the material is changed from the hole-transporting material to the light-emitting material contained in green light-emitting layer 45G.

[0084] Next, a blue electron blocking layer 44B is formed on the hole transport layer 43 at a position that overlaps with the blue subpixel SPB in a plan view of the substrate 2 (step S25). Step S25 may be performed by the same method as step S23, except that the thin film is formed at a position that overlaps with the blue subpixel SPB in a plan view.

[0085] In step S25, the thickness of the blue electron blocking layer 44B to be formed may be adjusted by adjusting the film thickness of the applied material, etc., so that the optical path length LB1 of the formed blue light-emitting element 3B is three-quarters of the wavelength of the blue light emitted by the blue light-emitting layer 45B.

[0086] Next, the blue light-emitting layer 45B is formed on the blue electron blocking layer 44B (step S26). Step S26 may be performed by the same method as step S24, except that the light-emitting material is changed to the light-emitting material contained in the blue light-emitting layer 45B and the thin film is formed at a position overlapping the blue sub-pixel SPB in a plan view. In other words, in step S26, the blue light-emitting layer 45B is formed at least above the anode 41B, particularly at a position overlapping the anode 41B in a plan view of the substrate 2.

[0087] Next, the hole-blocking layer 46 is formed on the hole-transporting layer 43 at a position overlapping with the green sub-pixel SPG in a plan view of the substrate 2, on the green light-emitting layer 45G, and on the blue light-emitting layer 45B (step S27). Step S27 may be performed by the same method as step S21, etc., except that the material to be deposited is changed to the above-described electron-transporting material, etc.

[0088] Thereafter, the distance from the substrate 2, on which the common layer including the hole blocking layer 46 is formed, differs depending on the subpixel. Therefore, the common layer may be discontinuous in a portion including between different subpixels, or may be continuous in a portion not shown.

[0089] Next, an electron transport layer 47 is formed on the hole blocking layer 46 (step S28). Step S28 may be performed by the same method as step S21, etc., except that the material used to form the film is changed to the above-mentioned electron transport material, etc. This completes the process of forming the first stack 4B, the first stack 4R, and the first stack 4G.

[0090] 3 , after the formation of the first stack 4B, the first stack 4R, and the first stack 4G, the charge generation layer 5B, the charge generation layer 5R, and the charge generation layer 5G are formed. In the process of forming the charge generation layer 5B, the charge generation layer 5R, and the charge generation layer 5G, first, the electron generation layer 51 is formed on the electron transport layer 47 (step S3). The electron generation layer 51 may be formed by depositing a thin film containing the above-described n-type doped metal or organic material on the electron transport layer 47 by vacuum deposition, sputtering, or the like.

[0091] Next, a hole generating layer 52 is formed on the electron generating layer 51 (step S4). The hole generating layer may be formed by, for example, replacing the material to be deposited in step S3 with a p-type doped metal or organic material. This completes the process of forming the charge generating layer 5B, the charge generating layer 5R, and the charge generating layer 5G.

[0092] For this reason, in steps S3 and S4, charge generation layer 5B is formed above blue light-emitting layer 45B, particularly at a position overlapping blue light-emitting layer 45B in a planar view of substrate 2. Also, in steps S3 and S4, charge generation layer 5R is formed above anode 41R, particularly at a position overlapping anode 41R in a planar view of substrate 2. Furthermore, in steps S3 and S4, charge generation layer 5R is formed at a position where the distance from anode 41R is smaller than the distance between anode 41B and charge generation layer 5B.

[0093] <Display Device Manufacturing Method: Formation of Second Stack> Following the formation of the charge generation layer 5B, charge generation layer 5R, and charge generation layer 5G, the second stack 6B, second stack 6R, and second stack 6G are formed (step S5). The process of forming the second stack 6B, second stack 6R, and second stack 6G according to this embodiment will be described in more detail with reference to FIG. 5. FIG. 5 is a flowchart showing a method of forming the second stack 6B, second stack 6R, and second stack 6G according to this embodiment.

[0094] In the process of forming the second laminate 6B, the second laminate 6R, and the second laminate 6G, first, a hole transport layer 61 is formed on the hole generating layer 52 (step S50). The hole transport layer 61 may be formed by the same method as the hole transport layer 43; in other words, step S50 may be performed by the same method as step S22.

[0095] Next, a red light-emitting layer 63R is formed on the hole-transport layer 61 at a position overlapping with the red sub-pixel SPR in a plan view of the substrate 2 (step S51). Step S51 may be performed by the same method as step S24 described with reference to Fig. 4, except that the light-emitting material is changed to the light-emitting material contained in the red light-emitting layer 63R, and the thin film is formed at a position overlapping with the red sub-pixel SPR in a plan view. In other words, in step S52, the red light-emitting layer 63R is formed above the charge generation layer 5R, particularly at a position overlapping with the charge generation layer 5R in a plan view of the substrate 2.

[0096] Next, a green electron blocking layer 62G is formed on the hole transport layer 61 at a position overlapping with the green sub-pixel SPG in a plan view of the substrate 2 (step S52). Step S52 may be performed by the same method as step S23 described with reference to Fig. 4. In step S52, the film thickness of the green electron blocking layer 62G to be formed may be adjusted by adjusting the film thickness of the applied material or the like so that the optical path length LG2 in the formed green light-emitting element 3G becomes 5 / 4 times the wavelength of the green light emitted by the green light-emitting layer 63G.

[0097] Next, a green light-emitting layer 63G is formed on the green electron-blocking layer 62G (step S53). Step S53 may be performed by the same method as step S24 described with reference to FIG.

[0098] Next, a blue electron blocking layer 62B is formed on the hole transport layer 61 at a position overlapping with the blue sub-pixel SPB in a plan view of the substrate 2 (step S54). Step S54 may be performed by the same method as step S25 described with reference to Fig. 4. In step S54, the thickness of the blue electron blocking layer 62B to be formed may be adjusted by adjusting the film thickness of the applied material or the like so that the optical path length LB2 in the formed blue light-emitting element 3B becomes 5 / 4 times the wavelength of the blue light emitted by the blue light-emitting layer 63B.

[0099] Next, a blue light-emitting layer 63B is formed on the blue electron blocking layer 62B (step S55). Step S55 may be performed by the same method as step S26 described with reference to Fig. 4. In other words, in step S55, the blue light-emitting layer 63B is formed at least above the charge generating layer 5B, particularly at a position overlapping the charge generating layer 5B in a plan view of the substrate 2.

[0100] Next, the hole blocking layer 64 is formed on the blue light-emitting layer 63B, the red light-emitting layer 63R, and the green light-emitting layer 63G (step S56). Step S56 may be performed by the same method as step S27 described with reference to FIG.

[0101] Next, the electron transport layer 65 is formed on the hole blocking layer 64 (step S57). Step S57 may be performed by the same method as step S28 described with reference to FIG.

[0102] Next, a cathode 66 is formed on the electron transport layer 65 (step S58). The cathode 66 may be formed, for example, by depositing a thin film of a metal material or the like on the electron transport layer 65 by vacuum deposition, sputtering, or the like. In other words, in step S58, the cathode 66 is formed above the blue light-emitting layer 63B and the red light-emitting layer 63R, particularly at a position overlapping the blue light-emitting layer 63B and the red light-emitting layer 63R in a plan view of the substrate 2. As described above, with the completion of the steps of forming the second stack 6B, the second stack 6R, and the second stack 6G, the manufacturing process of the light-emitting element 3 is completed, and thus the manufacturing process of the display device 1 is also completed.

[0103] <Summary of Manufacturing Method of Display Device> The manufacturing method of the display device 1 according to this embodiment manufactures a miniaturized display device 1 while reducing the decrease in the efficiency of extracting light from the light-emitting element 3. Furthermore, in the manufacturing method, it is only necessary to form a single layer, the red light-emitting layer 63R, as the light-emitting layer to form the red light-emitting element 3R, thereby reducing the amount of light-emitting material consumed and shortening the time required to form the red light-emitting element 3R. Therefore, the manufacturing method of the display device 1 reduces manufacturing costs and shortens the takt time during manufacturing.

[0104] Furthermore, according to the manufacturing method of the display device 1, it is possible to adjust the optical path lengths described above by adjusting the film thicknesses of the hole transport layer 43, the green electron blocking layer 44G, the blue electron blocking layer 44B, the green electron blocking layer 62G, and the blue electron blocking layer 62B. Therefore, in the manufacturing method of the display device 1, a design that improves the light extraction efficiency from the light-emitting element 3 can be more easily achieved.

[0105] In the manufacturing method of the display device 1 according to this embodiment, a certain electron blocking layer is formed, and then a light-emitting layer located on the electron blocking layer is formed. In this way, by successively forming the electron blocking layer and the light-emitting layer for a certain subpixel, the manufacturing method of the display device 1 reduces the burden of changing manufacturing conditions and simplifies the process.

[0106] In the manufacturing method of the display device 1 according to this embodiment, the step of forming the blue light-emitting layer 45B is performed after the step of forming the green light-emitting layer 45G. Also, in the manufacturing method of the display device 1, the step of forming the red light-emitting layer 63R, the step of forming the green light-emitting layer 63G, and the step of forming the blue light-emitting layer 63B are performed in this order. By forming each light-emitting layer in the above order, the manufacturing method can reduce the occurrence of patterning other light-emitting layers after the formation of each green light-emitting layer and each blue light-emitting layer.

[0107] In general, the green light-emitting layer of a light-emitting element tends to have lower reliability and luminous efficiency than the red light-emitting layer, and the blue light-emitting layer tends to have lower reliability and luminous efficiency than the red and green light-emitting layers. Therefore, by performing a patterning process that may cause deterioration of already formed layers after each red and green light-emitting layer, deterioration of each green and blue light-emitting layer can be more efficiently reduced. Therefore, in the manufacturing method of the display device 1, deterioration of the reliability and luminous efficiency of the light-emitting element 3 can be more efficiently reduced.

[0108] However, in the method for manufacturing the display device 1, the order in which each layer is formed is not particularly important as long as the structure shown in FIG. 1 can be formed. For example, in the method for manufacturing the display device 1, multiple electron blocking layers may be formed, and then a light-emitting layer may be formed on each of the electron blocking layers. In addition, in the method for manufacturing the display device 1, the green light-emitting layer 63G may be formed before the red light-emitting layer 63R. Furthermore, in the method for manufacturing the display device 1, the blue light-emitting layer 45B may be formed before the green light-emitting layer 45G, and the blue light-emitting layer 63B may be formed before the red light-emitting layer 63R and the green light-emitting layer 63G.

[0109] [Embodiment 2] <Thinning of Green Light-Emitting Element> Figure 6 is a schematic side cross-sectional view of a display device 7 according to this embodiment. Note that all of the schematic cross-sectional views of display devices in this specification, including Figure 6, show cross sections corresponding to the cross section of the display device 1 shown in Figure 1. The display device 7 according to this embodiment differs from the display device 1 according to the previous embodiment in the configuration of some of the light-emitting elements 3, in particular, some of the red light-emitting elements 3R and green light-emitting elements 3G.

[0110] The red light-emitting element 3R according to this embodiment includes a red electron blocking layer 62R, which serves as an electron blocking layer for the red light-emitting layer 63R, between the hole transport layer 61 and the red light-emitting layer 63R. The red electron blocking layer 62R may contain, for example, a hole transport material, or may contain the same material as the green electron blocking layer 62G or the blue electron blocking layer 62B.

[0111] Furthermore, in the green light emitting element 3G according to this embodiment, compared to the green light emitting element 3G according to the previous embodiment, the first stack 4G does not include a green electron blocking layer 44G and a green light emitting layer 45G, and the second stack 6G does not include a green electron blocking layer 62G. Therefore, the green light emitting element 3G according to this embodiment includes only a green light emitting layer 63G as the light emitting layer.

[0112] Therefore, in this embodiment, the first stacked body 4R and the first stacked body 4G have the same configuration. In other words, the layers between the anode 41R and the red light-emitting layer 63R contain the same material as the layers between the anode 41G and the green light-emitting layer 63G. In this case, the layers from the hole injection layer 42 to the hole transport layer 61 may be continuous layers between the red light-emitting element 3R and the green light-emitting element 3G.

[0113] In this embodiment, the optical path length LG2 is three-quarters the wavelength of the green light emitted by the green light-emitting layer 45G. In this embodiment, the thickness of the hole transport layer 43 may be determined so that the optical path length LG2 satisfies the above-mentioned condition while the thicknesses of the layers of the green light-emitting element 3G, excluding the hole transport layer 43, are kept to a minimum.

[0114] The thicknesses of blue electron blocking layer 44B, blue electron blocking layer 62B, and red electron blocking layer 62R may be determined so that optical path lengths LB1, LB2, and LR1 satisfy the above-described conditions. Here, the thickness of hole transport layer 43 may be determined so that optical path length LG2 satisfies the above-described condition, and the thicknesses of the layers in blue light-emitting element 3B and red light-emitting element 3R, excluding each electron blocking layer and hole transport layer 43, may be set to a minimum thickness.

[0115] Except for the above, the display device 7 according to this embodiment may have the same configuration as the display device 1 according to the previous embodiment.

[0116] In this embodiment, the blue light-emitting element 3B has two light-emitting layers, while the red light-emitting element 3R and the green light-emitting element 3G each have one light-emitting layer, so that the first stack 4R of the red light-emitting element 3R and the first stack 4G of the green light-emitting element 3G are thinner than the first stack 4B of the blue light-emitting element 3B.

[0117] The distance between the anode 41G and the charge generation layer 5G, in other words, the distance from the surface of the anode 41G on the cathode 66 side to the surface of the charge generation layer 5G on the anode 41G side, is defined as DG. In this embodiment, the distances DR and DG are smaller than the distance DB. The distances DR and DG may be substantially the same.

[0118] For this reason, in this embodiment, the total film thickness of each of the red light-emitting element 3R and the green light-emitting element 3G is smaller than the total film thickness of the blue light-emitting element 3B. Therefore, the display device 7 according to this embodiment can reduce the total film thickness of each of the red light-emitting element 3R and the green light-emitting element 3G while improving the extraction efficiency of blue light from the light-emitting element 3. Therefore, the display device 7 according to this embodiment can more efficiently reduce the total film thickness and achieve miniaturization.

[0119] On the other hand, in this embodiment as well, the optical path length LG2 is determined so that the green light emitting element 3G satisfies the above-mentioned formula (1). Therefore, the display device 7 according to this embodiment improves the extraction efficiency of green light from the green light emitting element 3G.

[0120] The method for manufacturing the display device 7 according to this embodiment is performed in accordance with the steps shown in Fig. 3, except for part of step S2 and part of step S5. In other words, in the method for manufacturing the display device 7 according to this embodiment, steps S1, S3, and S4 shown in Fig. 3 are performed in the same manner as the method according to the previous embodiment.

[0121] Steps S2 and S5 of the manufacturing method for the display device 7 according to this embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a flowchart showing step S2 according to this embodiment, in other words, a method for forming the first stack 4B, the first stack 4R, and the first stack 4G. Fig. 8 is a flowchart showing step S5 according to this embodiment, in other words, a method for forming the second stack 6B, the second stack 6R, and the second stack 6G.

[0122] 7 , step S2 according to the present embodiment is different from step S2 according to the previous embodiment only in that steps S23 and S24 are not executed. Therefore, in step S27, the hole-blocking layer 46 is formed in positions of the hole-transporting layer 43 that overlap with the red sub-pixel SPR and the green sub-pixel SPG in plan view of the substrate 2, and on the blue light-emitting layer 45B.

[0123] In step S22 according to this embodiment, the thickness of the hole transport layer 43 to be formed may be adjusted so that the optical path length LG2 of the green light emitting element 3G after formation is three-quarters of the wavelength of the green light emitted by the green light emitting layer 63G.

[0124] 8 , in step S5 according to the present embodiment, following step S50, the red electron blocking layer 62R is formed (step S59). Step S59 may be performed by the same method as step S52 or step S54, except that the thin film is formed at a position overlapping the red sub-pixel SPR in plan view.

[0125] In step S59 according to this embodiment, the thickness of the red electron blocking layer 62R to be formed may be adjusted so that the optical path length LR1 of the red light emitting element 3R after formation is three-quarters of the wavelength of the red light emitted by the red light emitting layer 63R.

[0126] Following step S59, among the steps shown in FIG. 5, step S51 described above is executed, step S52 is not executed, and steps S53 to S58 are executed.

[0127] In this way, the display device 7 according to this embodiment is manufactured. Unless otherwise specified, steps denoted by the same numbers in this specification may be performed by the same method.

[0128] The manufacturing method of the display device 7 according to this embodiment manufactures a smaller display device 7 while reducing the decrease in the efficiency of light extraction from the light-emitting elements 3. Furthermore, in the manufacturing method, it is sufficient to form only the red light-emitting layer 63R and the green light-emitting layer 63G as light-emitting layers to form the red light-emitting elements 3R and the green light-emitting elements 3G. Therefore, the manufacturing method of the display device 7 can reduce the amount of light-emitting material consumed and shorten the time required to form the red light-emitting elements 3R and the green light-emitting elements 3G. Therefore, the manufacturing method of the display device 7 further reduces manufacturing costs and further shortens the takt time during manufacturing.

[0129] In particular, in this embodiment, the layers between the anode 41R and the red light-emitting layer 63R contain the same material as the layers between the anode 41G and the green light-emitting layer 63G. In this case, in this embodiment, the layers between the anode 41R and the red light-emitting layer 63R and the layers between the anode 41G and the green light-emitting layer 63G can be formed from a common material. Therefore, the display device 7 has a simpler manufacturing process and a shorter takt time during manufacturing.

[0130] Furthermore, according to the manufacturing method of the display device 7, it is possible to adjust the optical path lengths described above by adjusting the film thicknesses of the hole transport layer 43, the blue electron blocking layer 44B, the red electron blocking layer 62R, and the blue electron blocking layer 62B. Therefore, in the manufacturing method of the display device 7, a design that improves the light extraction efficiency from the light-emitting element 3 can be more easily achieved.

[0131] 9 is a schematic cross-sectional side view of a display device 8 according to this embodiment. The display device 8 according to this embodiment differs from the display device 1 described above in the configuration of part of the light-emitting elements 3, in particular, part of the red light-emitting element 3R.

[0132] The red light-emitting element 3R according to this embodiment includes a red light-emitting layer 45R, which is a second red light-emitting layer, between the hole-transporting layer 43 and the hole-blocking layer 46. The red light-emitting layer 45R may contain the same material as the red light-emitting layer 63R. The red light-emitting element 3R also includes the red electron-blocking layer 62R described in the previous embodiment.

[0133] 9, the optical path length of light propagating from the surface of the anode 41R on the cathode 66 side to any part of the red light-emitting layer 45R is denoted by LR2. In this embodiment, the optical path length LR2 is one-fourth the wavelength of the red light emitted by the red light-emitting layer 45R.

[0134] In this case, the red light emitting element 3R satisfies the above formula (1) for the red light emitting layer 45R, and therefore the display device 8 improves the extraction efficiency from the light emitting element 3 for light emitted from the red light emitting layer 45R.

[0135] The thicknesses of blue electron blocking layer 44B, blue electron blocking layer 62B, green electron blocking layer 44G, green electron blocking layer 62G, and red electron blocking layer 62R may be determined so that optical path length LB1, optical path length LB2, optical path length LG1, optical path length LG2, and optical path length LR1 satisfy the above-mentioned conditions. Here, the thickness of hole transport layer 43 may be determined so that optical path length LR2 satisfies the above-mentioned condition, and the thicknesses of each layer in light-emitting element 3, except for each electron blocking layer and hole transport layer 43, may be set to a minimum thickness.

[0136] Except for the above, the display device 8 according to this embodiment may have the same configuration as the display device 1 described above.

[0137] In this embodiment, the red light-emitting element 3R includes two light-emitting layers, just like the blue light-emitting element 3B and the green light-emitting element 3G. However, the red light-emitting layer 45R, which is the second red light-emitting layer in this embodiment, is located closer to the anode 41R than the charge generation layer 5R. Therefore, in this embodiment as well, the distance DR is smaller than the distance DG and the distance DB.

[0138] For this reason, in this embodiment, the red light emitting element 3R has two light emitting layers, but the total film thickness of the red light emitting element 3R is smaller than the total film thickness of each of the blue light emitting element 3B and the green light emitting element 3G. Therefore, the display device 8 according to this embodiment can reduce the total film thickness of the red light emitting element 3R while improving the extraction efficiency of red light from the light emitting element 3. Therefore, the display device 8 according to this embodiment achieves a smaller size while further improving the extraction efficiency of red light.

[0139] The manufacturing method of the display device 8 according to this embodiment is performed in accordance with the steps shown in Fig. 3, except for part of step S2 and part of step S5. In other words, in the manufacturing method of the display device 8 according to this embodiment, steps S1, S3, and S4 shown in Fig. 3 are performed in the same manner as the manufacturing method of the display device 1 described above.

[0140] Steps S2 and S5 of the manufacturing method for the display device 8 according to this embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a flowchart showing step S2 according to this embodiment, in other words, a method for forming the first stack 4B, the first stack 4R, and the first stack 4G. Fig. 11 is a flowchart showing step S5 according to this embodiment, in other words, a method for forming the second stack 6B, the second stack 6R, and the second stack 6G.

[0141] 10 , in step S2 according to the present embodiment, following step S22, the red light-emitting layer 45R is formed (step S29). Step S29 may be performed by the same method as step S24 or step S26, except that a light-emitting material that emits red light is used and the thin film is formed at a position that overlaps the red sub-pixel SPR in plan view.

[0142] In step S22 according to this embodiment, the thickness of the hole transport layer 43 to be formed may be adjusted so that the optical path length LR2 of the red light emitting element 3R after formation is one-fourth the wavelength of the red light emitted by the red light emitting layer 45R.

[0143] In step S5 according to the present embodiment, step S59 is executed after step S50, and then steps S51 to S58 are executed, as shown in Fig. 11. In this way, the display device 8 according to the present embodiment is manufactured.

[0144] The manufacturing method of the display device 8 according to this embodiment manufactures a display device 8 that is miniaturized while improving the extraction efficiency of red light from the light-emitting element 3. Furthermore, the manufacturing method of the display device 8 makes it possible to adjust the optical path lengths described above by adjusting the film thicknesses of the hole transport layer 43, the blue electron blocking layer 44B, the blue electron blocking layer 62B, the green electron blocking layer 44G, the green electron blocking layer 62G, and the red electron blocking layer 62R. Therefore, in the manufacturing method of the display device 8, a design that improves the extraction efficiency of light from the light-emitting element 3 can be more easily achieved.

[0145] 12 is a schematic side cross-sectional view of a display device 9 according to this embodiment. The display device 9 according to this embodiment has the same configuration as the display device 8 of the previous embodiment, except that the blue light-emitting element 3B and the green light-emitting element 3G each include a red light-emitting layer 45R. In particular, the blue light-emitting element 3B includes a red light-emitting layer 45R between the hole transport layer 43 and the blue electron blocking layer 44B. Furthermore, the green light-emitting element 3G includes a red light-emitting layer 45R between the hole transport layer 43 and the green electron blocking layer 44G.

[0146] Furthermore, the red light-emitting layer 45R included in each of the blue light-emitting element 3B and the green light-emitting element 3G contains the same material as the red light-emitting layer 45R included in the red light-emitting element 3R. Therefore, the red light-emitting layer 45R according to this embodiment is a common layer. The red light-emitting layer 45R according to this embodiment may be a continuous layer between different sub-pixels.

[0147] In other words, the blue light-emitting element 3B includes a red light-emitting layer 45R as a second auxiliary layer containing the same material as the red light-emitting layer 45R between the anode 41B and the blue light-emitting layer 45B. The green light-emitting element 3G includes a red light-emitting layer 45R as a fourth auxiliary layer containing the same material as the red light-emitting layer 45R between the anode 41G and the green light-emitting layer 45G.

[0148] As in the previous embodiments, the distance DR in this embodiment is smaller than the distance DB. Furthermore, the optical path lengths LR1, LR2, LB1, LB2, LG1, and LG2 in this embodiment are the same as those in the previous embodiments. Therefore, the display device 9 in this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the extraction efficiency of blue and green light from the light-emitting element 3.

[0149] In the blue light-emitting element 3B according to this embodiment, the film thickness, hole transport property, and electron transport property of each layer of the first stack 4B may be determined so that recombination of holes from the anode 41B and electrons from the charge generation layer 5B occurs mainly in the blue light-emitting layer 45B. Similarly, in the green light-emitting element 3G according to this embodiment, the film thickness, hole transport property, and electron transport property of each layer of the first stack 4G may be determined so that recombination of holes from the anode 41G and electrons from the charge generation layer 5G occurs mainly in the green light-emitting layer 45G. This allows the blue light-emitting element 3B and the green light-emitting element 3G to reduce the generation of red light due to recombination of holes and electrons in the red light-emitting layer 45R and reduce color mixing. Furthermore, the red light-emitting layer 45R according to this embodiment may contain a material having hole transport property in order to improve the efficiency of hole injection into the blue light-emitting layer 45B and the green light-emitting layer 45G.

[0150] The display device 9 according to this embodiment may be manufactured by the same method as the method for manufacturing the display device 8 according to the previous embodiment, except for step S29. Step S29 according to this embodiment may be performed by the same method as step S29 according to the previous embodiment, except that the red light-emitting layer 45R is formed in common to a plurality of sub-pixels.

[0151] In the manufacturing method of the display device 9 according to this embodiment, the step of patterning the red light-emitting layer 45R is unnecessary or simplified, and therefore the manufacturing process of the display device 9 according to this embodiment can be simplified.

[0152] Furthermore, due to the relationship between the optical path lengths described above, the film thicknesses of the blue electron blocking layer 44B and the green electron blocking layer 44G are thinner than those of the previous embodiment by the film thickness of the red light-emitting layer 45R. Therefore, in the manufacturing method for the display device 9 according to this embodiment, the amount of material required to form the blue electron blocking layer 44B and the green electron blocking layer 44G can be reduced. In particular, the process for forming the blue electron blocking layer 44B and the green electron blocking layer 44G may include a process for patterning the deposited material. In this case, in the manufacturing method for the display device 9 according to this embodiment, the amount of material consumed in the patterning process can be efficiently reduced.

[0153] 13 is a schematic side cross-sectional view of a display device 10 according to this embodiment. The display device 10 according to this embodiment has the same configuration as the display device 9 of the previous embodiment, except that the red light emitting element 3R and the green light emitting element 3G each include a blue light emitting layer 45B and a blue light emitting layer 63B.

[0154] In particular, the red light-emitting element 3R includes a blue light-emitting layer 45B between the red light-emitting layer 45R and the hole-blocking layer 46, and a blue light-emitting layer 63B between the red light-emitting layer 63R and the hole-blocking layer 64. The green light-emitting element 3G includes a blue light-emitting layer 45B between the green light-emitting layer 45G and the hole-blocking layer 46, and a blue light-emitting layer 63B between the green light-emitting layer 63G and the hole-blocking layer 64.

[0155] Furthermore, the blue light-emitting layer 45B included in each of the red light-emitting element 3R and the green light-emitting element 3G contains the same material as the blue light-emitting layer 45B included in the blue light-emitting element 3B. In addition, the blue light-emitting layer 63B included in each of the red light-emitting element 3R and the green light-emitting element 3G contains the same material as the blue light-emitting layer 63B included in the blue light-emitting element 3B. Therefore, the blue light-emitting layer 45B and the blue light-emitting layer 63B according to this embodiment are common layers.

[0156] In other words, the red light-emitting element 3R includes a blue light-emitting layer 45B as a third auxiliary layer containing the same material as the blue light-emitting layer 45B between the red light-emitting layer 45R and the charge generating layer 5R. The red light-emitting element 3R also includes a blue light-emitting layer 63B as a first auxiliary layer containing the same material as the blue light-emitting layer 63B between the red light-emitting layer 63R and the cathode 66.

[0157] Furthermore, the green light-emitting element 3G includes a blue light-emitting layer 45B as a sixth auxiliary layer between the green light-emitting layer 45G and the charge generating layer 5G, which contains the same material as the blue light-emitting layer 45B. In addition, the green light-emitting element 3G includes a blue light-emitting layer 63B as a seventh auxiliary layer between the green light-emitting layer 63G and the cathode 66, which contains the same material as the blue light-emitting layer 63B.

[0158] As in the previous embodiments, the distance DR in this embodiment is smaller than the distance DB. Furthermore, the optical path lengths LR1, LR2, LB1, LB2, LG1, and LG2 in this embodiment are the same as those in the previous embodiments. Therefore, the display device 10 in this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the extraction efficiency of blue and green light from the light-emitting element 3.

[0159] The red light-emitting element 3R and the green light-emitting element 3G according to this embodiment may be configured to reduce the recombination of holes and electrons in the blue light-emitting layer 45B and the blue light-emitting layer 63B by the same method as described in the previous embodiment. This reduces the generation of blue light in the red light-emitting element 3R and the green light-emitting element 3G, thereby reducing color mixing. Furthermore, the blue light-emitting layer 45B and the blue light-emitting layer 63B according to this embodiment may contain a material having electron transport properties in order to improve the efficiency of electron injection into each light-emitting layer of the red light-emitting element 3R and the green light-emitting element 3G.

[0160] The display device 10 according to this embodiment may be manufactured by the same method as the manufacturing method of the display device 9 according to the previous embodiment, except for steps S26 and S55. Step S26 according to this embodiment may be performed by the same method as step S26 according to the previous embodiment, only in that the blue light-emitting layer 45B is formed in common to a plurality of sub-pixels. Step S55 according to this embodiment may be performed by the same method as step S55 according to the previous embodiment, only in that the blue light-emitting layer 63B is formed in common to a plurality of sub-pixels.

[0161] In the manufacturing method of display device 10 according to this embodiment, the process of patterning blue light-emitting layer 45B and blue light-emitting layer 63B is unnecessary or simplified. Therefore, the manufacturing process of display device 10 according to this embodiment can be simplified, and the takt time during manufacturing can be shortened.

[0162] 14 is a schematic side cross-sectional view of a display device 11 according to this embodiment. The display device 11 according to this embodiment has the same configuration as the display device 10 of the previous embodiment, except for the positions of the blue light-emitting layer 45B and the blue light-emitting layer 63B in the green light-emitting element 3G. In particular, the green light-emitting element 3G according to this embodiment includes the blue light-emitting layer 45B between the red light-emitting layer 45R and the green electron blocking layer 44G, and the blue light-emitting layer 63B between the hole transport layer 61 and the green electron blocking layer 62G.

[0163] In this embodiment, the blue light-emitting layer 45B and the blue light-emitting layer 63B are common layers, similar to the blue light-emitting layer 45B and the blue light-emitting layer 63B in the previous embodiment. Note that in this embodiment, the blue light-emitting layer 45B of the red light-emitting element 3R and the blue light-emitting layer 45B of the green light-emitting element 3G are both formed on the red light-emitting layer 45R. Therefore, the blue light-emitting layer 45B of the red light-emitting element 3R and the blue light-emitting layer 45B of the green light-emitting element 3G may be a continuous layer.

[0164] In other words, the green light-emitting element 3G includes a blue light-emitting layer 45B as a fourth auxiliary layer containing the same material as the blue light-emitting layer 45B between the anode 41G and the green light-emitting layer 45G. The green light-emitting element 3G also includes a blue light-emitting layer 63B as a fifth auxiliary layer containing the same material as the blue light-emitting layer 63B between the charge generation layer 5G and the green light-emitting layer 63G.

[0165] As in the previous embodiments, the distance DR in this embodiment is smaller than the distance DB. Furthermore, the optical path lengths LR1, LR2, LB1, LB2, LG1, and LG2 in this embodiment are the same as those in the previous embodiments. Therefore, the display device 11 in this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the extraction efficiency of blue and green light from the light-emitting element 3.

[0166] The display device 11 according to this embodiment may be manufactured by the same method as the method for manufacturing the display device 10 according to the previous embodiment, except for the order of some of the steps in step S2 and the order of some of the steps in step S5. Steps S2 and S5 of the method for manufacturing the display device 11 according to this embodiment will be described with reference to FIGS. 15 and 16 . FIG. 15 is a flowchart showing step S2 according to this embodiment, in other words, a method for forming the first stack 4B, the first stack 4R, and the first stack 4G. FIG. 16 is a flowchart showing step S5 according to this embodiment, in other words, a method for forming the second stack 6B, the second stack 6R, and the second stack 6G.

[0167] Step S2 in the manufacturing method of display device 11 is the same as step S2 in the manufacturing method of display device 10, except that steps S25 and S26 are performed before steps S23 and S24. In other words, in step S2 in the manufacturing method of display device 11, after the blue electron blocking layer 44B and the blue light-emitting layer 45B are formed, the green electron blocking layer 44G and the green light-emitting layer 45G are formed.

[0168] Step S5 in the manufacturing method of display device 11 is the same as step S5 in the manufacturing method of display device 10, except that steps S54 and S55 are performed before steps S52 and S53. In other words, in step S5 in the manufacturing method of display device 11, after the blue electron blocking layer 62B and the blue light-emitting layer 63B are formed, the green electron blocking layer 62G and the green light-emitting layer 63G are formed.

[0169] In the manufacturing method of the display device 11 according to this embodiment, the process of patterning the blue light-emitting layer 45B and the blue light-emitting layer 63B is unnecessary or simplified. Therefore, the manufacturing process of the display device 10 according to this embodiment can be simplified, and the takt time during manufacturing can be shortened.

[0170] Furthermore, due to the relationship between the optical path lengths described above, the film thickness of the green electron blocking layer 44G is thinner than in the previous embodiment by the film thickness of the blue light-emitting layer 45B, and the film thickness of the green electron blocking layer 62G is thinner than in the previous embodiment by the film thickness of the blue light-emitting layer 63B. Therefore, in the manufacturing method for the display device 11 according to this embodiment, the amount of material required to form each of the green electron blocking layer 44G and the green electron blocking layer 62G can be reduced. In particular, the process for forming each of the green electron blocking layer 44G and the green electron blocking layer 62G may include a process for patterning the deposited material. In this case, in the manufacturing method for the display device 11 according to this embodiment, the amount of material consumed in the patterning process can be efficiently reduced.

[0171] [Embodiment 7] <Example of Further Film Thickness Reduction of Light-Emitting Element> Figure 17 is a schematic side cross-sectional view of a display device 12 according to this embodiment. Compared to the display device 1 described above, the display device 12 according to this embodiment does not include the blue electron blocking layer 44B, the green electron blocking layer 44G, the blue electron blocking layer 62B, and the green electron blocking layer 62G. Furthermore, the optical path length LB1 in the blue light-emitting element 3B according to this embodiment is one-quarter the wavelength of the blue light emitted by the blue light-emitting layer 45B, and the optical path length LG1 in the green light-emitting element 3G is one-quarter the wavelength of the green light emitted by the green light-emitting layer 45G. Additionally, the optical path length LB2 in the blue light-emitting element 3B according to this embodiment is three-quarters the wavelength of the blue light emitted by the blue light-emitting layer 63B, and the optical path length LG2 in the green light-emitting element 3G is three-quarters the wavelength of the green light emitted by the green light-emitting layer 63G.

[0172] Furthermore, the display device 12 according to this embodiment further includes a red electron blocking layer 62R, as compared with the above-described display device 1. Therefore, the optical path length LR1 in the red light emitting element 3R according to this embodiment is three-quarters of the wavelength of the red light emitted by the red light emitting layer 63R.

[0173] In the display device 12 according to this embodiment, the thickness of the hole transport layer 43 may be made thinner than in the display device 1 described above, thereby adjusting the above-mentioned optical path lengths.

[0174] Except for the above, the display device 12 according to this embodiment has the same configuration as the above-described display device 1. Therefore, in the display device 12 according to this embodiment, the first stack 4R does not include a light-emitting layer, unlike the first stack 4B, and therefore the distance DR is smaller than the distance DB. Therefore, the display device 12 according to this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the blue light extraction efficiency from the light-emitting element 3.

[0175] In the present embodiment, too, the above formula (1) holds true for the blue light-emitting element 3B, the red light-emitting element 3R, and the green light-emitting element 3G, and therefore the display device 1 can more efficiently extract light from each light-emitting layer from the light-emitting element 3. Meanwhile, the optical path lengths LB1, LB2, LG1, and LG2 in the present embodiment are shorter than the optical path lengths LB1, LB2, LG1, and LG2 in embodiment 1. Therefore, the display device 12 according to the present embodiment can more efficiently extract light from each light-emitting layer from the light-emitting element 3 while reducing the total film thickness of the light-emitting element 3 compared to the light-emitting element 3 included in the display device 1.

[0176] The display device 12 according to this embodiment may be manufactured by a method that is a partial modification of the manufacturing method of the display device 1 described above. In particular, in the manufacturing method of the display device 12, the hole transport layer 43 is formed thinner in step S22, and steps S23, S25, S52, and S54 are omitted. In addition, in the manufacturing method of the display device 12, step S59 is executed between steps S50 and S51. Except for the above, the display device 12 according to this embodiment may be manufactured by the same method as the manufacturing method of the display device 1 described above.

[0177] 18 is a schematic side cross-sectional view of a display device 13 according to this embodiment. The display device 13 according to this embodiment differs from the display device 12 according to the previous embodiment only in the configuration of the green light-emitting element 3G. In particular, the green light-emitting element 3G according to this embodiment does not include a green light-emitting layer 45G, and includes a green electron blocking layer 62G, as compared with the green light-emitting element 3G according to the previous embodiment. Furthermore, the optical path length LG2 in the green light-emitting element 3G according to this embodiment is three-quarters the wavelength of the green light emitted by the green light-emitting layer 63G.

[0178] For this reason, in this embodiment, each layer between the anode 41R and the red light-emitting layer 63R contains the same material as each layer between the anode 41G and the green light-emitting layer 63G. In particular, between the red light-emitting element 3R and the green light-emitting element 3G, each layer from the hole injection layer 42 to the hole transport layer 61 may be a continuous layer.

[0179] Except for the above, the display device 13 according to this embodiment has the same configuration as the display device 12 according to the previous embodiment. Therefore, the distance DR is also smaller than the distance DB in the display device 13 according to this embodiment. Therefore, the display device 13 according to this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the extraction efficiency of blue light from the light-emitting element 3.

[0180] The display device 13 according to this embodiment may be manufactured by a method that is a partial modification of the manufacturing method of the display device 12 according to the previous embodiment. In particular, in the manufacturing method of the display device 13, step S24 is omitted and step S52 is executed. Except for the above, the display device 13 according to this embodiment may be manufactured by the same method as the manufacturing method of the display device 12 according to the previous embodiment.

[0181] 19 is a schematic side cross-sectional view of a display device 14 according to this embodiment. The display device 14 according to this embodiment differs from the display device 12 described above only in that the green light-emitting element 3G does not include a green light-emitting layer 63G. Between the blue light-emitting element 3B and the green light-emitting element 3G according to this embodiment, the hole-blocking layer 64, the electron-transporting layer 65, and the cathode 66 may each be a continuous layer.

[0182] In the display device 14 according to this embodiment, the distance DR is also smaller than the distance DB. Therefore, the display device 14 according to this embodiment can reduce the total film thickness of the red light-emitting element 3R while improving the extraction efficiency of blue light from the light-emitting element 3. Furthermore, unlike the display device 12 described above, the display device 14 according to this embodiment does not include the green light-emitting layer 63G, and therefore the total film thickness of the green light-emitting element 3G can be further reduced.

[0183] The display device 14 according to this embodiment may be manufactured by a method that is a partial modification of the manufacturing method of the display device 12 described above. In particular, in the manufacturing method of the display device 14, execution of step S53 is omitted. Except for the above, the display device 14 according to this embodiment may be manufactured by the same method as the manufacturing method of the display device 12 described above.

[0184] As another variation of the display device, the display device according to the present disclosure may include a red light-emitting element 3R including a red light-emitting layer 45R only in the first layer 4R, and a green light-emitting element 3G including a green light-emitting layer 63G only in the second layer 6G. In this case, the optical path length LR2 in the red light-emitting element 3R may be one-fourth the wavelength of the red light emitted by the red light-emitting layer 45R. Furthermore, the optical path length LG2 in the green light-emitting element 3G may be three-fourths the wavelength of the green light emitted by the green light-emitting layer 63G.

[0185] 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 created by combining the technical means disclosed in each embodiment. For example, the display device 8 may have only a green light-emitting layer 63G as a light-emitting layer, similar to the green light-emitting element 3G of the display device 7. In this case, the green light-emitting element 3G of the display device 8 may not have a green electron-blocking layer 44G in addition to the green light-emitting layer 45G.

[0186] 1, 7-14 Display device 2 Substrate 3 Light-emitting element 3B Blue light-emitting element 3R Red light-emitting element 3G Green light-emitting element 41B Anode (first light-reflecting electrode) 41R Anode (second light-reflecting electrode) 41G Anode (third light-reflecting electrode) 45B Blue light-emitting layer (first blue light-emitting layer, third auxiliary layer, fourth auxiliary layer, sixth auxiliary layer) 45R Red light-emitting layer (second red light-emitting layer, second auxiliary layer, fourth auxiliary layer) 45G Green light-emitting layer (first green light-emitting layer) 5B Charge generation layer (first charge generation layer) 5R Charge generation layer (second charge generation layer) 5G Charge generation layer (third charge generation layer) 63B Blue light-emitting layer (second blue light-emitting layer, first auxiliary layer, fifth auxiliary layer, seventh auxiliary layer) 63R Red light-emitting layer (first red light-emitting layer) 63G Green light-emitting layer (second green light-emitting layer) 66 Cathode (transparent electrode)

Claims

1. A display device comprising: a substrate; and a blue light-emitting element and a red light-emitting element on the substrate, wherein the blue light-emitting element comprises, in order from the substrate side, a first light-reflecting electrode, a first blue light-emitting layer, a first charge-generating layer, a second blue light-emitting layer, and a transparent electrode; and the red light-emitting element comprises, in order from the substrate side, a second light-reflecting electrode, a second charge-generating layer, a first red light-emitting layer, and the transparent electrode, wherein the distance between the second light-reflecting electrode and the second charge-generating layer is shorter than the distance between the first light-reflecting electrode and the first charge-generating layer.

2. The display device according to claim 1, wherein the transparent electrode is a semi-reflective electrode.

3. A display device according to claim 1 or 2, wherein the optical path length of light propagating from the surface of the first light-reflecting electrode on the transparent electrode side to any part of the first blue light-emitting layer is three-quarters of the wavelength of light emitted by the first blue light-emitting layer, and the optical path length of light propagating from the surface of the first light-reflecting electrode on the transparent electrode side to any part of the second blue light-emitting layer is five-quarters of the wavelength of light emitted by the second blue light-emitting layer.

4. A display device described in any one of claims 1 to 3, wherein the optical path length of light propagating from the surface of the second light-reflecting electrode on the transparent electrode side to any part of the first red light-emitting layer is three-quarters of the wavelength of light emitted by the first red light-emitting layer.

5. A display device according to any one of claims 1 to 4, wherein the red light emitting element includes a first auxiliary layer between the first red light emitting layer and the transparent electrode, the first auxiliary layer including the same material as the second blue light emitting layer.

6. A display device according to any one of claims 1 to 5, wherein said red light emitting element includes a second red light emitting layer between said second light reflecting electrode and said second charge generating layer.

7. A display device as described in claim 6, wherein the optical path length of light propagating from the surface of the second light-reflecting electrode on the transparent electrode side to any part of the second red light-emitting layer is one-fourth the wavelength of light emitted by the second red light-emitting layer.

8. A display device according to claim 6 or 7, wherein the blue light-emitting element includes a second auxiliary layer between the first light-reflecting electrode and the first blue light-emitting layer, the second auxiliary layer including the same material as the second red light-emitting layer.

9. A display device according to any one of claims 6 to 8, wherein the red light-emitting element includes a third auxiliary layer between the second red light-emitting layer and the second charge generating layer, the third auxiliary layer including the same material as the first blue light-emitting layer.

10. A display device according to any one of claims 1 to 9, comprising a green light-emitting element on the substrate, the green light-emitting element including, in order from the substrate side, a third light-reflecting electrode, a third charge-generating layer, a second green light-emitting layer, and the transparent electrode, and the distance between the third light-reflecting electrode and the third charge-generating layer is smaller than the distance between the first light-reflecting electrode and the first charge-generating layer.

11. A display device as described in claim 10, wherein the optical path length of light propagating from the surface of the third light-reflecting electrode on the transparent electrode side to any part of the second green light-emitting layer is three-quarters of the wavelength of light emitted by the second green light-emitting layer.

12. A display device according to claim 10 or 11, wherein each layer between the second light-reflecting electrode and the first red light-emitting layer contains the same material as each layer between the third light-reflecting electrode and the second green light-emitting layer.

13. A display device according to any one of claims 1 to 5, comprising a green light-emitting element on the substrate, the green light-emitting element including, in order from the substrate side, a third light-reflecting electrode, a first green light-emitting layer, a third charge-generating layer, a second green light-emitting layer, and the transparent electrode.

14. A display device according to any one of claims 6 to 9, comprising a green light-emitting element on the substrate, the green light-emitting element including, in order from the substrate side, a third light-reflecting electrode, a first green light-emitting layer, a third charge-generating layer, a second green light-emitting layer, and the transparent electrode.

15. The display device according to claim 14, wherein the green light-emitting element includes a fourth auxiliary layer between the third light-reflecting electrode and the first green light-emitting layer, the fourth auxiliary layer including the same material as at least one of the second red light-emitting layer and the first blue light-emitting layer.

16. A display device according to any one of claims 13 to 15, wherein the green light-emitting element includes a fifth auxiliary layer between the third charge generating layer and the second green light-emitting layer, the fifth auxiliary layer including the same material as the second blue light-emitting layer.

17. A display device according to any one of claims 13 to 16, wherein the green light-emitting element includes a sixth auxiliary layer between the first green light-emitting layer and the third charge generating layer, the sixth auxiliary layer including the same material as the first blue light-emitting layer.

18. A display device according to any one of claims 13 to 16, wherein the green light-emitting element includes a seventh auxiliary layer between the second green light-emitting layer and the transparent electrode, the seventh auxiliary layer including the same material as the second blue light-emitting layer.

19. A display device described in any one of claims 13 to 18, wherein the optical path length of light propagating from the surface of the third light-reflecting electrode on the transparent electrode side to any part of the first green light-emitting layer is three-quarters of the wavelength of light emitted by the first green light-emitting layer, and the optical path length of light propagating from the surface of the third light-reflecting electrode on the transparent electrode side to any part of the second green light-emitting layer is five-quarters of the wavelength of light emitted by the second green light-emitting layer.

20. A method for manufacturing a display device having a plurality of light-emitting elements on a substrate, the method comprising: forming a first light-reflecting electrode and a second light-reflecting electrode on the substrate; forming a first blue light-emitting layer at least above the first light-reflecting electrode; forming a first charge generation layer above the first blue light-emitting layer; forming a second charge generation layer above the second light-reflecting electrode at a position where the distance between the second light-reflecting electrode and the second charge generation layer is shorter than the distance between the first light-reflecting electrode and the first charge generation layer; forming a second blue light-emitting layer at least above the first charge generation layer; forming a first red light-emitting layer above the second charge generation layer; and forming transparent electrodes above the second blue light-emitting layer and the first red light-emitting layer.

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