CN110858627A

CN110858627A - Method for manufacturing organic EL device and organic EL device

Info

Publication number: CN110858627A
Application number: CN201910787473.3A
Authority: CN
Inventors: 关口泰广; 山下和贵
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-08-24
Filing date: 2019-08-23
Publication date: 2020-03-03
Also published as: KR20200023199A; TW202010162A; JP7193953B2; JP2020031187A

Abstract

The invention provides an organic EL device, which comprises a pixel, a substrate and a bank, wherein the pixel comprises a first electrode, an organic light-emitting layer and a second electrode, the bank is arranged on the substrate and is used for defining the pixel, the pixel is arranged in the bank, the organic light-emitting layer has a shape in a long side direction and a short side direction in a plan view, and has a concave shape in which the thickness of the center in the long side direction is smaller than that of two ends in a cross section passing through the center in the short side direction and parallel to the long side direction, and the current value of the pixel is 10mA/cm²The average luminance at that time was 3000cd/m²As above, with respect toA normalized luminance distribution curve in the cross section in which the maximum luminance value in the cross section is 1 is obtained, and pixels satisfy the following equation: SL (70). ltoreq.0.01 [ SL (70) denotes: when the position of the center in the longitudinal direction is set to 0, the position of one end is set to +100, and the position of the other end is set to-100, the average value of the absolute values of the slopes of the luminance distribution curves at the positions +70 and-70 is obtained.]。

Description

Method for manufacturing organic EL device and organic EL device

Technical Field

The present invention relates to a method for manufacturing an organic EL device and an organic EL device.

Background

An organic EL (electroluminescence) device is a device including a light-emitting element that utilizes electroluminescence of an organic compound. In the organic EL device, an organic light emitting layer is provided in each pixel, and each pixel is caused to emit light (for example, international publication No. 2008/149499).

Disclosure of Invention

In terms of low power consumption and long lifetime, an organic EL device is required to have improved External Quantum Efficiency (EQE).

On the other hand, in an organic EL device having pixels with banks (banks), in view of the risk of leakage (short circuit) when light is emitted from an end portion, the cross-sectional shape of the organic light-emitting layer provided in each pixel is a concave shape in which the thickness at the center in the longitudinal direction is smaller than the thicknesses at both ends, thereby suppressing the risk of leakage. However, in such an organic EL device, there is room for improvement in EQE.

The purpose of the present invention is to provide an organic EL device having excellent EQE.

Another object of the present invention is to provide a method capable of manufacturing an organic EL device with good EQE with good productivity.

The present invention provides a method for manufacturing an organic EL device and an organic EL device shown below.

[1] An organic EL device having a pixel including a first electrode, an organic light-emitting layer, and a second electrode,

the organic EL device includes a substrate and banks provided on the substrate and defining the pixels,

the pixels are arranged in the banks,

the organic light-emitting layer has a shape having a long side direction and a short side direction in a plan view, and has a concave shape in which a thickness at a center in the long side direction is smaller than thicknesses at both ends in a cross section passing through the center in the short side direction and parallel to the long side direction,

the pixel has a current value of 10mA/cm²The average luminance at that time was 3000cd/m²In the above-mentioned manner,

the luminance distribution curve in the cross section normalized so that the maximum luminance value in the cross section is 1, the pixel satisfies the following expression (1),

SL(70)≤0.010 (1)

[ in the formula, SL (70) represents: and an average value of an absolute value of a slope of the luminance distribution curve at a position +70 and an absolute value of a slope of the luminance distribution curve at a position-70, where a position of the center in the longitudinal direction is 0, a position of one end in the longitudinal direction is +100, and a position of the other end in the longitudinal direction is-100. ].

[2] A method of manufacturing an organic EL device includes a step of forming a pixel including a first electrode, an organic light emitting layer, and a second electrode,

the pixels are arranged in the banks,

the step of forming the pixel includes:

forming the organic light emitting layer on the first electrode;

forming the second electrode on the organic light-emitting layer; and

a step of inspecting the obtained pixel,

the organic light-emitting layer is formed so as to have a shape having a longitudinal direction and a short-side direction in a plan view, and has a concave shape in which a thickness at a center in the longitudinal direction is smaller than thicknesses at both ends in a cross section passing through the center in the short-side direction and parallel to the longitudinal direction,

the pixel has a current value of 10mA/cm²Luminance at that time was 3000cd/m²In the above-mentioned manner,

the step of performing the inspection includes: and a step of acquiring information on the gradient of the luminance distribution curve in the cross section of the pixel and determining the quality of the pixel based on the information.

[3] The method of manufacturing an organic EL device according to [2], wherein in the step of determining whether or not the pixel is good, regarding a luminance distribution curve in the cross section normalized by the luminance at the center in the longitudinal direction, the determination of whether or not the pixel is good is performed based on whether or not the pixel satisfies the following expression (1).

SL(70)≤0.010 (1)

[ in the formula, SL (70) represents: and an average value of an absolute value of a slope of the luminance distribution curve at a position +70 and an absolute value of a slope of the luminance distribution curve at a position-70, where a position of the center in the longitudinal direction is 0, a position of one end in the longitudinal direction is +100, and a position of the other end in the longitudinal direction is-100. ]

[4] The method of manufacturing an organic EL device according to [2] or [3], wherein an organic light-emitting layer is formed on the first electrode by a coating method.

According to the present invention, an organic EL device with good EQE can be provided.

In addition, according to the present invention, a method capable of manufacturing an organic EL device excellent in EQE with good productivity can be provided.

Drawings

Fig. 1 is a plan view of an organic EL device according to an embodiment when viewed from a pixel formation surface side.

Fig. 2 is a partially enlarged view of a section taken along line II-II of fig. 1.

Fig. 3 is a diagram illustrating a substrate with banks included in the organic EL device of fig. 1.

Fig. 4 is a diagram showing an example of a luminance distribution curve of a pixel.

Fig. 5 is a diagram for explaining an organic structure forming step.

Fig. 6 is a diagram for explaining an organic light-emitting layer forming process.

Fig. 7 is a graph showing a pressure reduction curve in the step of vacuum drying the coating film in forming the organic light-emitting layer in the examples, comparative examples, and reference examples.

Description of the reference numerals

1 organic EL device, 2 pixels, 2a pixel region, 2R red pixels, 2G green pixels, 2B blue pixels, 10 substrates with banks, 11 substrates, surfaces of 11a substrates, 12 anodes (first electrodes), 13 banks, side surfaces of 13a banks, 14 recesses, 20 organic EL structure portions, 21 hole injection layers, 22 hole transport layers, 23 organic light emitting layers, 30 cathodes (second electrodes), 40 organic structures.

Detailed Description

The present invention will be described below with reference to embodiments. The same elements are denoted by the same reference numerals. Duplicate descriptions are omitted. The dimensional ratios of the drawings do not necessarily correspond to the dimensional ratios of the illustrated objects.

< organic EL device >

The organic EL device 1 shown in fig. 1 is an organic EL display panel, and has a plurality of pixels 2. Each pixel 2 is an organic EL element section. That is, the organic EL device 1 has a structure in which a plurality of organic EL element portions are integrally connected.

In this specification, a "pixel" refers to a unit (or region) that emits light, and includes at least a first electrode, an organic light-emitting layer, and a second electrode. In the present embodiment, the pixel 2 includes an anode (first electrode) 12, a hole injection layer 21, a hole transport layer 22, an organic light emitting layer 23, and a cathode (second electrode) 30.

The pixels 2 have color information by the light emission of the pixels 2. In fig. 1, the pixel 2 is schematically shown with a dashed line.

The plurality of pixels 2 emit light of any one of red, green, and blue. From this viewpoint, the organic EL device 1 has 3 kinds of pixels 2, that is, a red pixel 2R that emits red light, a green pixel 2G that emits green light, and a blue pixel 2B that emits blue light. Hereinafter, when the colors of light emitted by the pixels 2 are described separately, the pixels 2 may be referred to as the red pixels 2R, the green pixels 2G, and the blue pixels 2B as described above.

The plurality of pixels 2 are arranged in a two-dimensional array (or matrix). Two mutually orthogonal directions of a two-dimensional array are also referred to as an X direction (or row direction) and a Y direction (or column direction). In this case, the red pixel 2R, the green pixel 2G, and the blue pixel 2B of 3 types constituting the plurality of pixels 2 are arranged by sequentially repeating, for example, the following rows (i), (ii), and (iii) in the Y direction, and are arranged in an array.

(i) The red pixels 2R are arranged in a row at a predetermined interval in the X direction.

(ii) The green pixels 2G are arranged in a row with a predetermined interval in the X direction.

(iii) The blue pixels 2B are arranged in the X direction at predetermined intervals.

The organic EL device 1 can perform full-color display by controlling the red pixel 2R, the green pixel 2G, and the blue pixel 2B included in a display pixel unit with the red pixel 2R, the green pixel 2G, and the blue pixel 2B arranged in parallel as one display pixel unit, for example.

The interval between the pixels 2 in each column, the interval between the pixels 2 in each row, the arrangement example of the pixels 2, the number of the pixels 2, and the like are appropriately set according to the pattern of the organic EL device 1 and the like.

The structure of the organic EL device 1 is explained in more detail.

Fig. 2 is a partially enlarged view of a section taken along line II-II of fig. 1. Fig. 3 is a diagram illustrating a substrate with a bank included in the organic EL device of fig. 1, and corresponds to fig. 2 in which components other than the substrate with a bank 10 are omitted.

The organic EL device 1 includes a substrate 10 with a bank, a plurality of organic EL structures 20, and a cathode (second electrode) 30. The organic EL device 1 may be a top emission type device or a bottom emission type device. Hereinafter, unless otherwise specified, a bottom emission type, that is, a case where light is extracted from the substrate 10 with banks will be described.

As shown in fig. 2 and 3, the substrate 10 with banks includes a substrate 11, a plurality of anodes (first electrodes) 12, and banks 13.

(1) Substrate

The substrate 11 is a plate-like transparent member having transparency to visible light (light having a wavelength of 400nm to 800 nm). The substrate 11 is a support for supporting the anode 12 and the bank 13. The thickness of the substrate 11 is, for example, 30 μm or more and 1100 μm or less. The substrate 11 may be a rigid substrate such as a glass substrate or a silicon substrate, or may be a flexible substrate such as a plastic substrate or a polymer film. By using a flexible substrate, the organic EL device 1 can have flexibility.

The substrate 11 may be pre-formed with circuitry for driving the pixels 2. The substrate 11 may be formed in advance with, for example, a TFT (Thin Film Transistor), a capacitor, or the like.

(2) Anode (first electrode)

The anode 12 is provided on the surface 11a of the substrate 11 in the pixel region 2a corresponding to each pixel 2. Examples of the planar shape (shape viewed from the thickness direction of the substrate 11) of the anode 12 include a rectangle such as a rectangle or a square, other polygons, and rounded shapes of corners of a rectangle or other polygons. The top view shape of the anode 12 may be circular or elliptical. The shape of the anode 12 in plan view may be a shape in which at least 1 side of a quadrangle or other polygon is formed in an arc shape (for example, an arc shape).

As the anode 12, a thin film containing a metal Oxide, a metal sulfide, a metal, or the like, specifically, a thin film containing Indium Oxide, Zinc Oxide, Tin Oxide, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), gold, platinum, silver, copper, or the like can be used. When the organic EL device 1 emits light from the substrate 10 side with banks, the anode 12 exhibiting light transmittance is used.

The thickness of the anode 12 may be appropriately determined in consideration of light transmittance, electrical conductivity, and the like. The thickness of the anode 12 is, for example, 10nm or more and 10 μm or less, preferably 20nm or more and 1 μm or less, and more preferably 50nm or more and 500nm or less.

The anode 12 can be formed by an evaporation method or a coating method. In the case of formation by the vapor deposition method, a layer containing the material of the anode 12 may be formed on the substrate 11, and then the layer may be patterned into a pattern of a plurality of anodes 12. When the anodes 12 are formed by a coating method, the anodes can be formed by applying a coating solution containing the material of the anodes 12 onto the substrate 11 in a pattern corresponding to the plurality of anodes 12 and then drying the coating film. Alternatively, a coating film containing a material to be formed into the anode 12 may be formed on the substrate 11 and dried, and then patterned into the pattern of the anode 12.

When a coating method is used for forming the anode 12, the coating method may be an inkjet printing method, and a known coating method, for example, a slit coating method, a microgravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, a nozzle printing method, or the like may be used. The solvent of the coating liquid containing the material of the anode 12 may be any solvent that can dissolve the material of the anode 12.

In one embodiment, a layer including an insulating layer or the like may be provided between the anode 12 and the substrate 11. A layer such as an insulating layer may be considered as a part of the substrate 11.

(3) Dyke

As shown in fig. 2 and 3, the banks 13 are provided around the anodes 12. The bank 13 spans between adjacent anodes 12. A part of the bank 13 may cover a peripheral portion of the anode 12. The bank 13 is a partition wall for defining (partitioning) the pixel 2 (pixel region 2 a). That is, the banks 13 are provided on the substrate 11 in a pattern having openings for defining the pixel regions 2a previously set on the front surface 11a of the substrate 11. In the present embodiment, as shown in fig. 1, since a plurality of pixels 2 are arranged in a two-dimensional array, a lattice-shaped bank 13 is provided on a substrate 11.

The bank 13 may be formed of, for example, resin. The bank 13 is a cured product of a photosensitive resin composition containing a liquid repellent agent, for example. Examples of the liquid repellent agent include a liquid repellent agent containing a fluororesin. As will be described later, an organic layer such as an organic light-emitting layer 23 is formed on the pixel region 2a defined by the bank 13 by, for example, an application method. Therefore, when an organic layer is formed on the pixel region 2a defined by the bank 13 by an application method, the bank 13 is usually formed so as to have characteristics (for example, wettability) suitable for forming the organic layer.

The shape and arrangement of the banks 13 are appropriately set in accordance with the number of pixels 2, the resolution, and the like of the organic EL device 1, the ease of manufacturing, and the like. For example, in fig. 2 and 3, the side surface 13a of the bank 13 facing the pixel region 2a is substantially perpendicular to the surface 11a of the substrate 11. However, the side surface 13a may be inclined at an acute angle with respect to the surface 11a, or may be inclined at an obtuse angle. The bank 13 is known to be tapered when the side surface 13a and the surface 11a are at an acute angle, and the bank 13 is known to be tapered when the side surface 13a and the surface of the substrate 11 are at an obtuse angle. The thickness (height) of the bank 13 is, for example, about 0.3 μm to 5 μm.

The bank-equipped substrate 10 can be manufactured by forming the banks 13 after forming the anodes 12 on the plurality of pixel regions 2a set in advance on the substrate 11, for example.

The bank 13 may be formed by, for example, a coating method. Specifically, the anode electrode 12 can be formed by drying a coating film formed by applying a coating liquid containing the material of the bank 13 on the substrate 11, and then patterning the coating film into a predetermined pattern. Examples of the coating method include spin coating and slit coating. The solvent of the coating liquid including the banks 13 may be any solvent that can dissolve the material of the banks 13.

(4) Hole injection layer

The hole injection layer 21 is an organic layer having a function of improving the hole injection efficiency of injecting holes from the anode 12 into the organic light emitting layer 23. As a material of the hole injection layer 21, a known hole injection material can be used. Examples of the hole injection material include oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide; a phenyl amine compound; StarBurst (StarBurst) amine compounds; a phthalocyanine compound; amorphous carbon; polyaniline; polythiophene derivatives such as polyethylene dioxythiophene (PEDOT).

The optimum value of the thickness of the hole injection layer 21 varies depending on the material used, and can be determined as appropriate in consideration of the required characteristics, the ease of layer formation, and the like. The thickness of the hole injection layer 21 is, for example, 1nm or more and 1 μm or less, preferably 2nm or more and 500nm or less, and more preferably 5nm or more and 200nm or less.

The hole injection layer 21 may be provided by changing the material or thickness thereof as needed according to the type of the pixel 2, i.e., the red pixel 2R, the green pixel 2G, and the blue pixel 2B. From the viewpoint of simplicity of the step of forming the hole injection layer 21, all the hole injection layers 21 may be formed of the same material and the same thickness.

(5) Hole transport layer

The hole transport layer 22 is a layer having a function of improving injection of holes from the anode 12, the hole injection layer 21, or the hole transport layer 22 closer to the anode 12 into the organic light emitting layer 23. As the material of the hole transport layer 22, a known hole transport material can be used. Examples of the material of the hole transport layer 22 include polyvinylcarbazole or a derivative thereof, polysilane or a derivative thereof, polysiloxane or a derivative thereof having an aromatic amine in a side chain or a main chain, pyrazoline or a derivative thereof, arylamine or a derivative thereof, stilbene (stilbene) or a derivative thereof, triphenyldiamine or a derivative thereof, polyaniline or a derivative thereof, polythiophene or a derivative thereof, polyarylamine or a derivative thereof, polypyrrole or a derivative thereof, poly (p-phenylacetylene) or a derivative thereof, and poly (2, 5-thiophenylacetylene) or a derivative thereof. Further, as a material of the hole transport layer 22, a hole transport layer material disclosed in japanese patent laid-open No. 2012-144722 can be cited.

The optimum value of the thickness of the hole transport layer 22 varies depending on the material used, and may be set as appropriate so that the driving voltage and the light emission efficiency are appropriate values. The thickness of the hole transport layer 22 is, for example, 1nm or more and 1 μm or less, preferably 2nm or more and 500nm or less, and more preferably 5nm or more and 200nm or less.

The hole transport layer 22 may be provided by changing the material or thickness thereof as needed according to the type of the pixel 2, i.e., the red pixel 2R, the green pixel 2G, and the blue pixel 2B. From the viewpoint of simplicity of the step of forming the hole transport layer 22, all the hole transport layers 22 may be formed of the same material and the same thickness.

(6) Organic light emitting layer

The organic light-emitting layer 23 is disposed on the hole transport layer 22. The organic light-emitting layer 23 is an organic layer having a function of emitting light of a predetermined wavelength. The organic light-emitting layer 23 is generally formed mainly of an organic substance that emits fluorescence and/or phosphorescence, or formed of the organic substance and a dopant that assists the organic substance. For example, a dopant is added to improve the light emission efficiency and to change the emission wavelength.

The organic material contained in the organic light-emitting layer 23 may be a low molecular compound or a high molecular compound. Examples of the light-emitting material constituting the organic light-emitting layer 23 include a dye-based material, a metal complex-based material, a polymer-based material, and a dopant material described below.

Examples of the pigment-based light-emitting material include cyclopentylamine or a derivative thereof, tetraphenylbutadiene or a derivative thereof, triphenylamine or a derivative thereof, oxadiazole or a derivative thereof, pyrazoloquinoline or a derivative thereof, distyrylbenzene or a derivative thereof, distyrylarylene (distyrylarylene) or a derivative thereof, pyrrole or a derivative thereof, a thiophene ring compound, a pyridine ring compound, perinone or a derivative thereof, perylene or a derivative thereof, oligothiophene or a derivative thereof, an oxadiazole dimer or a derivative thereof, a pyrazoline dimer or a derivative thereof, quinacridone or a derivative thereof, coumarin or a derivative thereof, and the like.

Examples of the metal complex-based light-emitting material include metal complexes having a rare earth metal such as Tb, Eu, or Dy, a central metal such as a1, Zn, Be, Pt, or Ir, and having a ligand such as oxadiazole, thiadiazole, phenylpyridine, phenylbenzimidazole, or quinoline structure. Examples of the metal complex include metal complexes having light emission from a triplet excited state, such as iridium complexes and platinum complexes, aluminum quinolate complexes, benzoquinolinol beryllium complexes, benzoxazole zinc complexes, benzothiazole zinc complexes, azomethyl zinc complexes, porphyrin zinc complexes, phenanthroline europium complexes, and the like.

Examples of the polymer-based light-emitting material include polyparaphenylene vinylene or a derivative thereof, polythiophene or a derivative thereof, polyparaphenylene (polyparaphenylene) or a derivative thereof, polysilane or a derivative thereof, polyacetylene or a derivative thereof, polyfluorene or a derivative thereof, polyvinylcarbazole or a derivative thereof, and a material obtained by polymerizing the above-mentioned dye material and metal complex material.

Among the above-mentioned light-emitting materials, examples of the material emitting red light (hereinafter also referred to as "red light-emitting material") include coumarin or a derivative thereof, a thiophene ring compound and a polymer thereof, polyparaphenylene vinylene or a derivative thereof, polythiophene or a derivative thereof, and polyfluorene or a derivative thereof. As the red light-emitting material, a material disclosed in japanese patent application laid-open publication No. 2011-105701 may be cited.

Examples of the green light-emitting material (hereinafter also referred to as "green light-emitting material") include quinacridone or a derivative thereof, coumarin or a derivative thereof, a polymer of the coumarin or the derivative, polyparaphenylene vinylene or a derivative thereof, and polyfluorene or a derivative thereof. The green emitting material may be the one disclosed in Japanese patent laid-open No. 2012-036388.

Examples of the material emitting blue light (hereinafter also referred to as "blue light-emitting material") include distyrylarylene or a derivative thereof, oxadiazole or a derivative thereof, a polymer of these, polyvinylcarbazole or a derivative thereof, polyphenyl or a derivative thereof, and polyfluorene or a derivative thereof. Examples of the blue light-emitting material include those disclosed in Japanese patent laid-open publication No. 2012 and 144722.

Examples of the dopant include perylene or a derivative thereof, coumarin or a derivative thereof, rubrene or a derivative thereof, quinacridone or a derivative thereof, squaraine or a derivative thereof, porphyrin or a derivative thereof, styryl pigment, tetracene or a derivative thereof, pyrazolone or a derivative thereof, decacycloalkene (decacyclene) or a derivative thereof, and phenoxazone (phenoxazone) or a derivative thereof.

The organic light emitting layer 23 may be provided according to the type of the pixel 2, i.e., the red pixel 2R, the green pixel 2G, and the blue pixel 2B. An organic light-emitting layer 23 that emits red light is provided on the hole transport layer 22 of the concave portion 14 corresponding to the red pixel 2R, an organic light-emitting layer 23 that emits green light is provided on the hole transport layer 22 of the concave portion 14 corresponding to the green pixel 2G, and an organic light-emitting layer 23 that emits blue light is provided on the hole transport layer 22 of the concave portion 14 corresponding to the blue pixel 2B. Hereinafter, the organic light-emitting layers 23 included in the red pixel 2R, the green pixel 2G, and the blue pixel 2B may be referred to as a red light-emitting layer 23R, a green light-emitting layer 23G, and a blue light-emitting layer 23B.

As shown in fig. 2, in the substrate with banks 10, a plurality of organic EL structure sections 20 are provided in the concave sections 14 (see fig. 2 and 3) formed by the banks 13 and the anodes 12. In the present embodiment, the organic EL structure section 20 includes a hole injection layer 21, a hole transport layer 22, and an organic light emitting layer 23.

That is, each pixel 2 is disposed in the bank 13 (in the concave portion 14 defined by the bank 13).

In at least 1 pixel 2, it is preferable that: in all the pixels 2, the organic light-emitting layer 23 has a shape having a longitudinal direction and a short-side direction in a plan view as shown in fig. 1. In the present specification, a planar view means a view from the thickness direction of the layer. In the present embodiment, the layers constituting the organic EL structure 20 have the same shape in a plan view.

Examples of the shape having the longitudinal direction and the short side direction include a rectangle, a shape obtained by rounding the corners of the rectangle, a shape obtained by forming at least 1 side of the rectangle into an arc (for example, an arc), and an ellipse.

In at least 1 pixel 2, it is preferable that: in all the pixels 2, the organic light-emitting layer 23 having a shape of a long side direction and a short side direction in a plan view has a concave shape in which a thickness at the center in the long side direction is smaller than thicknesses at both ends in a cross section passing through the center in the short side direction and parallel to the long side direction (see fig. 2). By providing such a concave shape, the amount of current injection into the outer peripheral portion of the organic light-emitting layer 23, which is likely to cause leakage or local light emission, is reduced, and thus the reduction in the luminance characteristics of the pixel can be suppressed.

The difference between the thickness of both ends in the longitudinal direction and the thickness of the center in the organic light-emitting layer 23 having the concave shape is, for example, 1nm to 20nm, and from the viewpoint of improving luminance and EQE, it is preferably 1nm to 10nm, and more preferably 1nm to 5 nm.

The average thickness of the organic light-emitting layer is, for example, 1nm or more and 2 μm or less, preferably 5nm or more and 500nm or less, and more preferably 10nm or more and 100nm or less.

The organic light-emitting layer 23 having a concave shape can be confirmed by observing a cross section using an optical microscope, for example.

When the organic light-emitting layer 23 is formed by an application method in the bank 13, the organic light-emitting layer 23 usually has a concave shape due to the influence of surface tension.

(7) Cathode (second electrode)

The cathode 30 is disposed on the organic light emitting layer 23. The material of the cathode 30 is preferably a material having a small work function, high conductivity, and being capable of easily injecting electrons into the organic light-emitting layer 23. As described in the present embodiment, when the organic EL device 1 extracts light from the anode 12 side, a material having a high visible light reflectance is preferably used as the material of the cathode 30 in order to reflect light emitted from the organic light-emitting layer 23 to the anode 12 side by the cathode 30. For example, an alkali metal, an alkaline earth metal, a transition metal, a group 13 metal of the periodic table, or the like can be used for the cathode 30. As the cathode 30, a transparent conductive cathode containing a conductive metal oxide, a conductive organic substance, or the like may be used.

The thickness of the cathode 30 may be appropriately set in consideration of electrical conductivity and durability. The thickness of the cathode 30 is, for example, 10nm or more and 10 μm or less, preferably 20nm or more and 1 μm or less, and more preferably 50nm or more and 500nm or less.

Other layers such as 1 or 2 or more electron injection layers and electron transport layers may be provided between the organic light-emitting layer 23 and the cathode 30.

The electron injection layer is a layer having a function of improving electron injection efficiency of injecting electrons from the cathode to the organic light emitting layer. The electron injection layer may use a known electron injection material. In the case where the electron injection layer is provided in this way, an electron transport layer may be provided between the electron injection layer and the organic light emitting layer. The electron transport layer is a layer having a function of improving injection of electrons from the cathode, the electron injection layer, or the electron transport layer closer to the cathode. The electron transport layer may use a known electron transport material.

In the present embodiment, the cathode 30 is formed over the entire surface of the display region where the plurality of pixels 2 are provided. That is, the cathode 30 is formed not only on the organic light-emitting layer 23 but also on the bank 13, and is provided as a cathode commonly used in the plurality of pixels 2.

Although not shown in fig. 1 and 2, a sealing substrate is usually provided on the cathode 30 of the organic EL device 1. The organic EL device 1 may include other known elements included in an organic EL display panel, for example.

(8) Luminance characteristics and luminance distribution characteristics of pixels

In the organic EL device 1, at least 1 of the plurality of pixels 2 satisfies the following [ a ] and [ B ]. Hereinafter, a pixel satisfying the following [ a ] and [ B ] is also referred to as a "specific pixel".

The [ A ] current value was 10mA/cm²The average luminance at that time was 3000cd/m²The above.

The luminance distribution curve in a cross section passing through the center of the organic light-emitting layer 23 in the short-side direction and parallel to the long-side direction, normalized to 1, satisfies the following expression (1).

SL(70)≤0.010 (1)

The present invention remarkably improves the effect of improving EQE in an organic EL device including a specific pixel having high luminance efficiency (unit: cd/a) satisfying the above [ a ]. The luminance efficiency referred to herein is luminance (unit: cd/m)²) Is divided by the current value (unit: mA/cm²) The resulting value.

The average luminance is an average value of luminance in the longitudinal direction of the organic light-emitting layer 23 in a cross section passing through the center of the organic light-emitting layer 23 in the longitudinal direction and parallel to the longitudinal direction.

The current value was 10mA/cm²The average luminance at the time is preferably 4000cd/m²More preferably 5000cd/m or more²The above.

The current value was 10mA/cm²The average luminance (average luminance efficiency) at the time is mainly dependent on the kind of the light-emitting material contained in the organic light-emitting layer 23. Therefore, as the light-emitting material used in at least one of the organic light-emitting layers 23 included in the plurality of pixels 2, for example, a current value of 10mA/cm is selected from the light-emitting materials exemplified above²The average luminance of the phosphor is in the above range.

In the description of [ B ] above, referring to fig. 4 showing an example of a luminance distribution curve of a pixel, SL (70) shows an average value of an absolute value of a slope of the luminance distribution curve at a position +70 and an absolute value of a slope of the luminance distribution curve at a position-70, where a position of a center in a longitudinal direction of an organic light emitting layer (pixel) is 0, a position at one end in the longitudinal direction is +100, and a position at the other end in the longitudinal direction is-100.

The luminance distribution curve here refers to a graph showing a relationship between a position (horizontal axis) in the longitudinal direction of the organic light emitting layer (pixel) and luminance (vertical axis) at the position, and the luminance on the vertical axis is normalized by setting the maximum luminance value at the center in the longitudinal direction of the organic light emitting layer 23 to 1 (see fig. 4).

The slope of the luminance profile at position +70 means: when the coordinates of the luminance distribution curve are (position, luminance at the position), the slope of a straight line obtained by linear approximation using 5 coordinate points (+68.4, luminance at the position), (+69.2, luminance at the position), (+70.0, luminance at the position), (+70.8, luminance at the position), and (+71.6, luminance at the position) is used.

Likewise, the slope of the luminance profile at position-70 refers to: the slope of a line obtained by linear approximation using 5 coordinate points (-71.6, luminance at this position), (-70.8, luminance at this position), (-70.0, luminance at this position), (-69.2, luminance at this position), and (-68.4, luminance at this position).

The specific pixel satisfying [ a ] and [ B ] and the organic EL device including the specific pixel can exhibit a higher EQE than the pixel satisfying [ a ] but not satisfying [ B ] and the organic EL device including the pixel. This is presumably because: in the pixel, the proportion of the portion of the region that also produces light emission with a lower EQE decreases, and the proportion of the portion of the region that produces light emission with a higher EQE increases.

From the viewpoint of improving the effect of EQE, SL (70) is preferably 0.008 or less, more preferably 0.005 or less, further preferably 0.003 or less, and particularly preferably 0.002 or less.

SL (70) is ideally near 0.

In order to obtain a more significant EQE-enhancing effect, the specific pixel preferably satisfies [ a ] and [ B ] and satisfies the following [ C ].

In [ C ], the horizontal axis represents the amount of current (unit: mA/cm) supplied to the pixel²) The vertical axis represents the average luminance (unit: cd/m²) In the graph showing the relationship between the current amount and the average luminance, a value obtained by dividing the value of the average luminance at the current value by the current value (i.e., a slope at the current value in the graph, which means the average luminance efficiency at the current value) gradually decreases as the current amount increases.

There is a tendency that: the greater the degree of the above reduction, the greater the EQE improvement effect.

The following are clear from the studies of the present inventors: when the position at which the slope of the luminance distribution curve is obtained is the end portion (the position is 100 in absolute value) of the organic light emitting layer or is close to the end portion as in the case where the slope exceeds 80 in absolute value, for example, there are also factors such as disturbance, and no correlation is observed between the slope of the luminance distribution curve and the EQE.

It has been clarified that: when the position at which the slope of the luminance distribution curve is obtained is less than 60 in absolute value, for example, no correlation is observed between the slope of the luminance distribution curve and the EQE.

In contrast, it is clear that: when the position at which the slope of the luminance distribution curve is obtained is, for example, 60 or more and 80 or less in absolute value, the correlation is confirmed, and particularly, when the slope is 70 in absolute value, the correlation is more clear, and when SL (70) is 0.010 or less and is not 0.010 or less, a significant difference in EQE is clearly confirmed.

In the present invention, in the case where the organic EL device has a plurality of pixels, if at least 1 pixel is a specific pixel, an EQE improvement effect can be obtained in the pixel. However, from the viewpoint of the EQE improvement effect as an organic EL device, the organic EL device preferably has 2 or more specific pixels, and more preferably has as many specific pixels as possible.

From the viewpoint of the EQE-improving effect as an organic EL device and the viewpoint of improving the productivity of the organic EL device, the organic EL device is preferably: all the red pixels 2R are specific pixels, all the green pixels 2G are specific pixels, or all the blue pixels 2B are specific pixels. In particular, the green pixel 2G is preferably a specific pixel because its luminance is likely to increase in the characteristics of its visibility curve, and then more preferably a specific pixel in the order of the red pixel 2R and the blue pixel 2B. Further, it is particularly preferable that 2 or more kinds of pixels selected from all the red pixels 2R, all the green pixels 2G, and all the blue pixels 2B are used as the specific pixels.

In the above description, the first electrode included in the substrate with banks is an anode and the second electrode is a cathode, but the first electrode may be a cathode and the second electrode may be an anode. In the above description, the organic EL device has three kinds of pixels, i.e., the red pixel 2R, the green pixel 2G, and the blue pixel 2B, but the type of color is not particularly limited, and all the pixels may emit the same color.

In the above description, the hole injection layer and the hole transport layer are formed between the organic light emitting layer and the electrode provided on the substrate with banks, but these layers may not be formed. For example, the organic light-emitting layer may be formed adjacent to an electrode provided on the substrate with banks. Alternatively, the organic light-emitting layer may be formed adjacent to the hole injection layer without forming the hole transport layer.

The organic EL device is not limited to the organic display panel, and may be any organic light emitting device.

< method for producing organic EL device >

Next, a method for manufacturing the organic EL device 1 will be described. Here, a method of manufacturing the organic EL device 1 after aligning the bank-provided substrate 10 will be described.

The method of manufacturing the organic EL device 1 includes a step of forming a pixel, and the step of forming a pixel includes the following steps.

Step S101 of forming organic light-emitting layer 23 on anode (first electrode) 12 (organic light-emitting layer forming step),

A step (cathode forming step) S102 of forming a cathode (second electrode) 30 on the organic light-emitting layer 23, and

and a step S103 of inspecting the obtained pixel.

In the manufacture of the organic EL device 1, first, a step (organic structure forming step) S100 of forming the organic structure 40 on the anode (first electrode) 12 is performed after the preparation of the substrate 10 with the bank and before the step S101. In the organic structure forming step S100, as shown in fig. 5, the hole injection layer 21 and the hole transport layer 22 are sequentially formed on the anode 12 provided in the pixel region 2a, in other words, in the recess 14, by a coating method, thereby producing the organic structure 40 as a laminate of the hole injection layer 21 and the hole transport layer 22. The organic structure 40 is a part of a pixel.

Specifically, a coating film is formed by dropping a coating liquid containing a hole injection material on the anode 12 of the concave portion 14, and then the coating film is dried, thereby forming the hole injection layer 21.

The coating method includes, for example, an ink jet printing method. However, if the coating method is a coating method capable of forming a layer in the concave portion 14, other known coating methods such as a micro-gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, and a nozzle printing method may be used, and a screen printing method, a flexographic printing method, an offset printing method, and a nozzle printing method may be preferably used.

The solvent used in the coating liquid is not limited as long as it can dissolve the hole injection material, and examples thereof include: chloride solvents such as chloroform, dichloromethane, dichloroethane and the like; ether solvents such as tetrahydrofuran; aromatic hydrocarbon solvents such as toluene and xylene; ketone solvents such as acetone and methyl ethyl ketone; and ester solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve acetate.

The method for drying the coating film is not limited as long as the coating film can be dried, and vacuum drying, heat drying, and the like can be exemplified.

Next, a coating solution containing a hole transport material is dropped onto the hole injection layer 21 in the concave portion 14 to form a coating film, and then the coating film is dried to form the hole transport layer 22. Examples of the solvent and the drying method may be the same as in the case of the hole injection layer 21.

After the organic structure forming step S100, an organic light emitting layer forming step S101 is performed. In the organic light emitting layer forming step S101, as shown in fig. 6, the organic light emitting layer 23 is preferably formed on the organic structure 40 by a coating method.

Specifically, the organic light-emitting layer 23 is formed by dropping a coating liquid containing a light-emitting material to be formed into the organic light-emitting layer 23 onto the hole transport layer 22 in the bank 13, that is, in the concave portion 14 to form a coating film, and then drying the coating film.

The red light-emitting layer 23R, the green light-emitting layer 23G, and the blue light-emitting layer 23B are formed on the concave portions 14 corresponding to the red pixel 2R, the green pixel 2G, and the blue pixel 2B using coating liquids containing a red light-emitting material, a green light-emitting material, and a blue light-emitting material, respectively.

As the coating method, an inkjet printing method may be exemplified, and other known coating methods exemplified for the hole injection layer 21 may be used. The solvent used in the coating liquid is not limited as long as it can dissolve the light-emitting material, and may be the same as the solvent exemplified in the case of forming the hole injection layer 21.

As in the case of the hole injection layer 21, the method for drying the coating film is not limited as long as the coating film can be dried, and vacuum drying, heat drying, and the like can be exemplified.

In the organic light emitting layer forming step S101, the organic EL structure 20 including the organic structure 40 and the organic light emitting layer 23 is formed on the anode 12 in the concave portion 14.

As described above, in at least 1 pixel 2, preferably in all the pixels 2, the organic light-emitting layer 23 has a shape having a long side direction and a short side direction in a plan view. In the organic EL device 1 according to the present embodiment, each layer constituting the organic EL structure 20 has the same shape in a plan view.

As described above, in at least 1 pixel 2, preferably in all the pixels 2, the organic light-emitting layer 23 having a shape in the longitudinal direction and the short-side direction in a plan view has a concave shape in which the thickness at the center in the longitudinal direction is smaller than the thickness at both ends in a cross section passing through the center in the short-side direction and parallel to the longitudinal direction (see fig. 6).

In the organic light emitting layer forming step S101, the organic light emitting layer 23 is formed so that at least 1 of the plurality of pixels 2 satisfies the above [ a ]. In order to satisfy the above [ A ], a current value of 10mA/cm is selected from the light-emitting materials exemplified above²The organic light-emitting layer 23 is formed of a light-emitting material whose average luminance is in the above range. The above description is cited for the details of [ A ].

After the organic light-emitting layer 23 is formed, a step (cathode forming step) S102 of forming a cathode (second electrode) 30 is performed. Examples of the method for forming the cathode 30 include a vapor deposition method and a coating method similar to those of the anode 12. In this step, the cathode 30 is formed over the organic light-emitting layer 23 formed on the plurality of concave portions 14. This makes it possible to obtain the organic EL device 1 shown in fig. 1 and 2 in which the pixels 2 are formed in the banks 13.

After the cathode formation step S102, a step (inspection step) S103 of inspecting the obtained pixel is performed. The inspection step S103 includes: and a step of acquiring information on the gradient of a luminance distribution curve in a cross section of the organic light-emitting layer 23 included in the pixel, the cross section passing through the center in the short-side direction and being parallel to the long-side direction, and determining the quality of the pixel based on the information. The above description is cited for the luminance distribution curve.

According to the method of measuring the luminance distribution curve of the pixel and determining the quality of the pixel based on the information obtained from the curve, the quality determination can be performed easily and simply as compared with the method of measuring the shape (for example, thickness distribution, or the like) of the organic light emitting layer 23 itself and determining the quality of the pixel based on the measurement result, and therefore, the productivity of the organic EL device 1 can be improved.

The information on the slope of the luminance distribution curve is preferably information on the slope of the luminance distribution curve at a position of 60 or more and 80 or less in absolute value, and more preferably information on the slope of the luminance distribution curve at a position of 70 in absolute value, namely SL (70). By selecting information on the slope of the luminance distribution curve at a position of 60 to 80 in absolute value, particularly SL (70), as information on the slope of the luminance distribution curve, it is possible to easily determine whether or not the pixel is good, and by setting whether or not the above equation (1) is satisfied as a good/bad determination criterion, it is possible to accurately produce an organic EL device with good EQE.

The above description is cited for SL (70), its range and preferred range, and formula (1).

Examples of a method of forming a pixel so as to satisfy [ B ] above include: in the step of vacuum-drying the coating film for forming the organic light-emitting layer 23, a decompression curve (a relationship between a time of evacuation and a degree of vacuum in the drying furnace in an operation of evacuating a gas in the drying furnace and reducing the pressure) and/or a drying temperature are adjusted. For example, it is advantageous to set the decompression rate to be large or the drying temperature to be low in order to form pixels satisfying [ B ].

In the inspection step S103 for the pixel satisfying [ a ], for example, when whether or not the above expression (1) is satisfied is set as a quality determination criterion and SL (70) exceeds 0.010, it is preferable that: the step of adjusting the formation of the organic light-emitting layer 23 is performed so as to satisfy [ B ] above.

From the viewpoint of increasing the EQE, the organic EL device obtained by the manufacturing method according to the present invention includes at least 1 specific pixel, i.e., pixels satisfying the above [ a ] and [ B ]. However, from the viewpoint of the EQE improvement effect as an organic EL device, the organic EL device preferably has 2 or more specific pixels, and more preferably has as many specific pixels as possible.

From the viewpoint of the EQE-improving effect as an organic EL device and the viewpoint of improving the productivity of the organic EL device, the organic EL device is preferably: all the red pixels 2R are specific pixels, all the green pixels 2G are specific pixels, or all the blue pixels 2B are specific pixels. In particular, the green pixel 2G is preferably a specific pixel because its luminance is likely to increase in terms of the characteristics of its visibility curve, and then more preferably a specific pixel in the order of the red pixel 2R and the blue pixel 2B. Further, it is particularly preferable that 2 or more kinds of pixels selected from all the red pixels 2R, all the green pixels 2G, and all the blue pixels 2B are used as the specific pixels.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

< example 1>

A plurality of pixels were fabricated by forming a hole injection layer 21, a hole transport layer 22, and an organic light-emitting layer 23 on the bank-provided substrate 10 from the anode 12 side on the plurality of recesses 14, and forming a cathode 30 on the organic light-emitting layer 23. Thereby, an organic EL device was obtained. The hole injection layer 21, the hole transport layer 22, and the organic light-emitting layer 23 are formed by forming a coating film by an inkjet printing method using a coating liquid corresponding to each layer, and vacuum-drying the coating film. As the organic light-emitting layer 23 in each concave portion 14, a green light-emitting layer 23G is used. The organic EL structure 20 constituting a pixel has a shape having a long side direction and a short side direction in a plan view.

As a result of confirmation using a non-contact three-dimensional surface shape measuring apparatus (manufactured by Zygo), the organic light-emitting layer 23 had a concave shape in which the thickness at the center in the longitudinal direction was smaller than the thickness at both ends in a cross section passing through the center in the short-side direction and parallel to the longitudinal direction. The same applies to example 2, comparative examples 1 and 2, and reference examples 1 and 2 below.

In the plurality of pixels 2 formed, the same hole injection material, hole transport material, and green light emitting material are used for the hole injection layer 21, the hole transport layer 22, and the organic light emitting layer 23, respectively. In the vacuum drying performed when the organic light emitting layer 23 was formed, the temperature in the vacuum chamber was 25 ℃. Fig. 7 shows a pressure reduction curve in the vacuum chamber during the vacuum drying.

< example 2>

An organic EL device 1 was produced in the same manner as in example 1, except that the drying temperature in the vacuum drying performed in the formation of the organic light-emitting layer 23 was set to 35 ℃. In example 1 and example 2, the materials of the anode 12, the hole injection layer 21, the hole transport layer 22, the organic light emitting layer 23, and the cathode 30 are the same, respectively.

< comparative example 1>

An organic EL device 1 was produced in the same manner as in example 1, except that the curve of the reduced pressure in the vacuum chamber during vacuum drying performed in the formation of the organic light-emitting layer 23 was as shown in fig. 7. In example 1 and comparative example 1, the materials of the anode 12, the hole injection layer 21, the hole transport layer 22, the organic light emitting layer 23, and the cathode 30 were the same, respectively.

< comparative example 2>

An organic EL device 1 was produced in the same manner as in example 1, except that the curve of the reduced pressure in the vacuum chamber during vacuum drying performed in the formation of the organic light-emitting layer 23 was as shown in fig. 7. In example 1 and comparative example 2, the materials of the anode 12, the hole injection layer 21, the hole transport layer 22, the organic light emitting layer 23, and the cathode 30 were the same, respectively.

< reference example 1>

A plurality of pixels were fabricated by forming a hole injection layer 21, a hole transport layer 22, and an organic light-emitting layer 23 on the bank-provided substrate 10 from the anode 12 side on the plurality of recesses 14, and forming a cathode 30 on the organic light-emitting layer 23. Thereby, an organic EL device was obtained. The hole injection layer 21, the hole transport layer 22, and the organic light-emitting layer 23 are formed by forming a coating film by an inkjet printing method using a coating liquid corresponding to each layer, and vacuum-drying the coating film. As the organic light-emitting layer 23 in each concave portion 14, a blue light-emitting layer 23B is used. The organic EL structure 20 constituting a pixel has a shape having a long side direction and a short side direction in a plan view.

In the plurality of pixels 2 formed, the same hole injection material, hole transport material, and blue light emitting material are used for the hole injection layer 21, the hole transport layer 22, and the organic light emitting layer 23, respectively. In the vacuum drying performed when the organic light emitting layer 23 was formed, the temperature in the vacuum chamber was 35 ℃. Fig. 7 shows a pressure reduction curve in the vacuum chamber during the vacuum drying.

< reference example 2>

An organic EL device 1 was produced in the same manner as in reference example 1, except that the drying temperature in the vacuum drying performed in the formation of the organic light-emitting layer 23 was set to 55 ℃. In reference examples 1 and 2, the materials of the anode 12, the hole injection layer 21, the hole transport layer 22, the organic light emitting layer 23, and the cathode 30 were the same, respectively.

[ measurement and evaluation ]

(1) The current value was 10mA/cm²Average brightness of time

Using a two-dimensional color luminance meter manufactured by radial Vision Systems, 1 of the plurality of pixels was measured by the applied current [ unit: mA]And a light emitting area [ unit: cm²]The obtained current value was 10mA/cm²Average luminance [ unit: cd/m²]. The results are shown in table 1. The average luminance was obtained for a cross section passing through the center of the organic light-emitting layer 23 in the short-side direction and parallel to the long-side direction.

(2) Brightness distribution curve and SL (70)

The luminance distribution in the pixel obtained by the measurement of (1) above was obtained using a two-dimensional color luminance meter manufactured by radial Vision Systems, and a luminance distribution curve was obtained. A luminance distribution curve is obtained for a cross section passing through the center of the organic light-emitting layer 23 in the short-side direction and parallel to the long-side direction.

In addition, SL (70) is obtained from the obtained luminance distribution curve in accordance with the above definition. The results are shown in table 1.

(3)EQE

For the pixels subjected to the measurement of the above (1), a two-dimensional color luminance meter manufactured by radial Vision Systems was used, and the luminance was measured by voltage [ unit: v ], current [ unit: mA and the emission spectrum were used to determine EQE. The results are shown in table 1.

[ Table 1]

Claims

1. An organic EL device having a pixel including a first electrode, an organic light-emitting layer, and a second electrode,

the pixels are arranged within the banks,

with respect to the luminance distribution curve in the cross section on which normalization is performed with the maximum luminance value in the cross section set to 1, the pixel satisfies the following expression (1),

SL(70)≤0.010 (1)

in the formula, SL (70) represents: and an average value of an absolute value of a slope of the luminance distribution curve at a position +70 and an absolute value of a slope of the luminance distribution curve at a position-70, where a position of the center in the longitudinal direction is set to 0, a position at one end in the longitudinal direction is set to +100, and a position at the other end in the longitudinal direction is set to-100.

2. A method of manufacturing an organic EL device, comprising: a step of forming a pixel including a first electrode, an organic light-emitting layer, and a second electrode,

the pixels are arranged within the banks,

the step of forming the pixel includes:

forming the organic light emitting layer on the first electrode;

forming the second electrode on the organic light-emitting layer; and

a step of inspecting the obtained pixel,

the organic light-emitting layer is formed so as to have a shape having a long side direction and a short side direction in a plan view, and has a concave shape in which a thickness at a center in the long side direction is smaller than thicknesses at both ends in a cross section passing through the center in the short side direction and parallel to the long side direction,

the step of performing the inspection includes: and a step of acquiring information on the gradient of a luminance distribution curve in the cross section of the pixel, and determining the quality of the pixel based on the information.

3. The method of manufacturing an organic EL device according to claim 2, wherein in the step of performing the pixel quality determination, the pixel quality determination is performed based on whether or not the pixel satisfies the following expression (1) with respect to a luminance distribution curve in the cross section normalized by the luminance at the center in the longitudinal direction,

SL(70)≤0.010 (1)

4. The method for manufacturing an organic EL device according to claim 2 or 3, wherein an organic light-emitting layer is formed on the first electrode by a coating method.