JP7193953B2 - Organic EL device manufacturing method and organic EL device - Google Patents

Description

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

An organic EL (electroluminescence) device is a device including a light-emitting element utilizing electroluminescence of an organic compound. In an organic EL device, an organic light-emitting layer is provided in each pixel, and light is emitted from each pixel [eg, International Publication No. 2008/149499 (Patent Document 1)].

WO2008/149499

Organic EL devices are required to have improved external quantum efficiency (EQE) from the viewpoint of low power consumption and long life.
On the other hand, in an organic EL device having pixels with banks, the cross-sectional shape of the organic light-emitting layer provided in each pixel is adjusted so that the thickness at the center in the longitudinal direction is at both ends because of the risk of leakage (short circuit) when light is emitted from the edge. The risk of leakage was suppressed by making the concave shape smaller than the thickness. However, in such an organic EL device, there is room for improvement regarding EQE.

An object of the present invention is to provide an organic EL device with good 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 an organic EL device manufacturing method and an organic EL device described below.
[1] An organic EL device comprising a pixel including a first electrode, an organic light-emitting layer, and a second electrode,
The organic EL device comprises a substrate and a bank provided on the substrate for defining the pixel,
the pixels are arranged in the bank;
The organic light-emitting layer has a shape having a longitudinal direction and a lateral direction in plan view, and in a cross section passing through the center in the lateral direction and parallel to the longitudinal direction, the thickness at the center in the longitudinal direction is having a concave shape smaller than the thickness,
The pixel has an average luminance of 3000 cd/m ² or more when the current value is 10 mA/cm ² ,
For the pixel, the luminance distribution curve in the cross section normalized with the value of the maximum luminance in the cross section being 1, the following formula (1):
SL(70)≦0.010 (1)
[In the formula, SL(70) is the luminance distribution at position +70 when the position of the center in the longitudinal direction is 0, the position of one end in the longitudinal direction is +100, and the position of the other end in the longitudinal direction is −100. It represents the mean value of the absolute value of the slope of the curve and the absolute value of the slope of the luminance distribution curve at position -70. ]
An organic EL device that satisfies
[2] A method for manufacturing an organic EL device, comprising forming a pixel including a first electrode, an organic light-emitting layer, and a second electrode,
The organic EL device comprises a substrate and a bank provided on the substrate for defining the pixel,
the pixels are arranged in the bank;
The step of forming the pixels includes:
forming the organic light-emitting layer on the first electrode;
forming the second electrode on the organic light-emitting layer;
inspecting the resulting pixels;
including
The organic light-emitting layer has a shape having a longitudinal direction and a lateral direction in a plan view, and in a cross section passing through the center in the lateral direction and parallel to the longitudinal direction, the thickness at the center in the longitudinal direction is formed to have a concave shape that is smaller than the thickness;
the pixel has a luminance of 3000 cd/m ² or more at a current value of 10 mA/cm ² ;
The method of manufacturing an organic EL device, wherein the inspecting step includes obtaining information about a slope of a luminance distribution curve in the cross section of the pixel, and determining quality of the pixel based on the information.
[3] In the step of determining the quality of the pixel, the luminance distribution curve in the cross section when the pixel is normalized by the luminance at the center in the longitudinal direction is expressed by the following formula (1):
SL(70)≦0.010 (1)
[In the formula, SL(70) is the luminance distribution at position +70 when the position of the center in the longitudinal direction is 0, the position of one end in the longitudinal direction is +100, and the position of the other end in the longitudinal direction is −100. It represents the mean value of the absolute value of the slope of the curve and the absolute value of the slope of the luminance distribution curve at position -70. ]
The method for manufacturing an organic EL device according to [2], wherein the quality determination of the pixel is performed based on whether or not the condition is satisfied.
[4] The method for 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.

An organic EL device with good EQE can be provided.
Moreover, it is possible to provide a method capable of manufacturing an organic EL device with good EQE with good productivity.

1 is a plan view when an organic EL device according to one embodiment is viewed from a pixel formation surface side; FIG. 2 is a partially enlarged view of a cross section taken along line II-II of FIG. 1; FIG. FIG. 2 is a diagram for explaining a banked substrate included in the organic EL device of FIG. 1; It is a figure which shows an example of the luminance distribution curve of a pixel. It is a figure for demonstrating an organic structure formation process. It is a figure for demonstrating the organic light emitting layer formation process. FIG. 4 is a diagram showing pressure reduction profiles in a step of vacuum-drying a coating film when forming an organic light-emitting layer in Examples, Comparative Examples, and Reference Examples.

Hereinafter, the present invention will be described while showing embodiments. The same reference numerals are given to the same elements. Redundant explanations are omitted. The dimensional proportions of the drawings do not necessarily match those of the description.

<Organic EL device>
FIG. 1 is a plan view of an organic EL device according to one embodiment when viewed from the pixel formation surface side.
The organic EL device 1 shown in FIG. 1 is an organic EL display panel and has multiple pixels 2 . Each pixel 2 is an organic EL element portion. That is, the organic EL device 1 has a configuration in which a plurality of organic EL element portions are integrally connected.
As used herein, a "pixel" means a unit (or region) that emits light, and includes at least a first electrode, an organic light-emitting layer, and a second electrode. In this embodiment, the pixel 2 is composed of 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 .
Due to the light emission of the pixel 2, the pixel 2 has color information. In FIG. 1, the pixels 2 are schematically indicated by dashed lines.

Each of the plurality of pixels 2 emits red, green, or blue light. From this point of view, the organic EL device 1 has three types of pixels 2: red pixels 2R that emit red light, green pixels 2G that emit green light, and blue pixels 2B that emit blue light. In the following description, the pixels 2 may be referred to as the red pixel 2R, the green pixel 2G, and the blue pixel 2B as described above when the colors emitted by the pixels 2 are distinguished.

A plurality of pixels 2 are arranged in a two-dimensional array (or matrix). The two orthogonal directions of the two-dimensional array are also called X direction (or row direction) and Y direction (or column direction). In this case, the three types of red pixels 2R, green pixels 2G, and blue pixels 2B that constitute the plurality of pixels 2 are, for example, arranged in the following columns (i), (ii), and (iii) in this order in the Y direction. By repeatedly arranging with , they are aligned with each other.
(i) A row in which red pixels 2R are arranged at predetermined intervals in the X direction.
(ii) A row in which the green pixels 2G are arranged at predetermined intervals in the X direction.
(iii) A row in which the blue pixels 2B are arranged at predetermined intervals in the X direction.

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

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

The configuration of the organic EL device 1 will be described in more detail.
FIG. 2 is a partially enlarged cross-sectional view taken along line II-II of FIG. FIG. 3 is a drawing for explaining the banked substrate of the organic EL device of FIG. 1, and corresponds to the drawing in which components other than the banked substrate 10 are omitted from FIG.
The organic EL device 1 includes a banked substrate 10 , 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. Unless otherwise specified, the bottom emission type, that is, the case where light is extracted from the banked substrate 10 side will be described below.
As shown in FIGS. 2 and 3 , the banked substrate 10 has a substrate 11 , a plurality of anodes (first electrodes) 12 and banks 13 .

(1) Substrate The substrate 11 is a plate-shaped transparent member that transmits visible light (light with a wavelength of 400 nm to 800 nm). The substrate 11 is a support that supports the anodes 12 and the banks 13 . The thickness of the substrate 11 is, for example, 30 μm or more and 1100 μm or less. The substrate 11 may be, for example, a rigid substrate such as a glass substrate or a silicon substrate, or 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.

A circuit for driving the pixels 2 may be formed in advance on the substrate 11 . For example, a TFT (Thin Film Transistor), a capacitor, or the like may be formed in advance on the substrate 11 .

(2) Anode (first electrode)
The anode 12 is provided on the pixel region 2a corresponding to each pixel 2 on the surface 11a of the substrate 11 . The planar shape of the anode 12 (the shape viewed from the thickness direction of the substrate 11) may be, for example, a rectangle, a square such as a square, other polygons, and a rectangle or other polygon with rounded corners. shape and the like. The planar shape of the anode 12 may be circular or elliptical. The planar shape of the anode 12 may be a quadrangle or other polygon with at least one side arcuate (for example, arcuate).

The anode 12 can use a thin film made of metal oxide, metal sulfide, metal, etc. Specifically, indium oxide, zinc oxide, tin oxide, indium tin oxide (abbreviated as ITO), indium A thin film made of zinc oxide (Indium Zinc Oxide: abbreviated as IZO), gold, platinum, silver, copper, or the like is used. When the organic EL device 1 emits light from the banked substrate 10 side, an anode 12 exhibiting optical transparency is used.

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

Anode 12 can be formed by a vapor deposition method or a coating method. In the case of forming by vapor deposition, a layer made of the material of the anode 12 is formed on the substrate 11 and then patterned into a pattern of a plurality of anodes 12 . When forming the anodes 12 by a coating method, a coating liquid containing the material of the anodes 12 is coated on the substrate 11 in a pattern corresponding to the plurality of anodes 12, and then the coating film is dried. Alternatively, a coating film made of a material to be 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 to form the anode 12, examples of the coating method include an inkjet printing method, and other known coating methods such as a slit coating method, a micro gravure coating method, a gravure coating method, and 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, and 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 composed of an insulating layer or the like may be provided between the anode 12 and the substrate 11 . Layers such as insulating layers may also be considered part of the substrate 11 .

(3) Banks Banks 13 are provided around each anode 12, as shown in FIGS. Banks 13 are also provided across adjacent anodes 12 . A portion of bank 13 may cover the peripheral edge of anode 12 . The bank 13 is a partition for defining (partitioning) the pixels 2 (pixel regions 2a). That is, the banks 13 are provided on the substrate 11 in such a pattern as to have openings defining the pixel regions 2a preset on the surface 11a of the substrate 11 . In the present embodiment, as shown in FIG. 1, a grid-shaped bank 13 is provided on the substrate 11 because a plurality of pixels 2 are arranged in a two-dimensional array.

The bank 13 can be made of resin, for example. The bank 13 is, for example, a cured product of a photosensitive resin composition containing a liquid-repellent agent. Examples of liquid-repellent agents include liquid-repellent agents containing fluororesin. On the pixel region 2a defined by the bank 13, an organic layer such as an organic light-emitting layer 23 is formed by, for example, a coating method, as will be described later. Therefore, the bank 13 normally has a property (for example, wettability) that enables the formation of an organic layer preferably when the organic layer is formed on the pixel region 2a defined by the bank 13 using a coating method. is formed as

The shape and arrangement of the bank 13 are appropriately set according to the specifications of the organic EL device 1 such as the number of pixels 2 and resolution, ease of manufacture, and the like. For example, in FIGS. 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. As shown in FIG. However, the side surface 13a may be inclined at an acute angle or an obtuse angle with respect to the surface 11a. When the side 13a and the surface 11a form an acute angle, the shape of the bank 13 is known as forward taper, and when the side 13a and the surface of the substrate 11 form an obtuse angle, the shape of the bank 13 is a reverse taper. known as The thickness (height) of the bank 13 is, for example, about 0.3 μm or more and 5 μm or less.

The banked substrate 10 can be manufactured, for example, by forming the banks 13 after forming the anodes 12 on a plurality of pixel regions 2a preset on the substrate 11 .

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

(4) Hole injection layer The hole injection layer 21 is an organic layer that has a function of improving the efficiency of hole injection from the anode 12 to the organic light emitting layer 23 . A known hole injection material can be used for the material of the hole injection layer 21 . Examples of hole injection materials include oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide and aluminum oxide; phenylamine compounds; starburst type amine compounds; phthalocyanine compounds; and polythiophene derivatives such as

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

The hole injection layer 21 is provided with a different material or thickness for each type of pixel 2, that is, for each red pixel 2R, green pixel 2G, and blue pixel 2B, as required. From the viewpoint of simplification of the process of forming the hole injection layers 21, all the hole injection layers 21 may be formed with the same material and the same thickness.

(5) Hole-Transporting Layer The hole-transporting layer 22 is a layer having a function of improving hole injection from the anode 12, the hole-injecting layer 21, or the hole-transporting layer 22 closer to the anode 12 to the organic light-emitting layer 23. be. A known hole-transporting material can be used for the material of the hole-transporting layer 22 . Materials for the hole transport layer 22 include, for example, polyvinylcarbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane having aromatic amines in side chains or main chains or derivatives thereof, pyrazolines or derivatives thereof, arylamines or derivatives thereof. , stilbene or derivatives thereof, triphenyldiamine or derivatives thereof, polyaniline or derivatives thereof, polythiophene or derivatives thereof, polyarylamines or derivatives thereof, polypyrrole or derivatives thereof, poly(p-phenylene vinylene) or derivatives thereof, and poly(2 , 5-thienylene vinylene) or derivatives thereof. Further, a hole transport layer material disclosed in JP-A-2012-144722 can also be mentioned.

The optimum thickness of the hole transport layer 22 differs depending on the material used, and is appropriately set so that the driving voltage and the luminous efficiency are appropriate values. The thickness of the hole transport layer 22 is, for example, 1 nm or more and 1 μm or less, preferably 2 nm or more and 500 nm or less, and more preferably 5 nm or more and 200 nm or less.

The hole transport layer 22 is provided with a different material or thickness for each type of pixel 2, that is, for each red pixel 2R, green pixel 2G, and blue pixel 2B, if necessary. From the viewpoint of simplification of the process of forming the hole transport layer 22, all the hole injection layers 21 may be formed with the same material and the same thickness.

(6) Organic Light Emitting Layer The organic light emitting layer 23 is provided 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 usually formed of an organic material that mainly emits fluorescence and/or phosphorescence, or the organic material and a dopant that assists this. A dopant is added, for example, to improve the luminous efficiency or change the luminous wavelength.
The organic substance contained in the organic light-emitting layer 23 may be a low-molecular-weight compound or a high-molecular-weight compound. Examples of the light-emitting material forming the organic light-emitting layer 23 include the following dye-based materials, metal complex-based materials, polymer-based materials, and dopant materials.

Examples of dye-based luminescent materials include cyclopentamine or its derivatives, tetraphenylbutadiene or its derivatives, triphenylamine or its derivatives, oxadiazole or its derivatives, pyrazoloquinoline or its derivatives, distyrylbenzene or its derivatives. derivatives, distyrylarylene or its derivatives, pyrrole or its derivatives, thiophene ring compounds, pyridine ring compounds, perinone or its derivatives, perylene or its derivatives, oligothiophene or its derivatives, oxadiazole dimer or its derivatives, pyrazoline dimer or derivatives thereof, quinacridone or derivatives thereof, coumarin or derivatives thereof, and the like;

Examples of metal complex-based light-emitting materials include rare earth metals such as Tb, Eu, and Dy, or Al, Zn, Be, Pt, and Ir. Examples thereof include metal complexes having imidazole, quinoline structures, etc. as ligands. Examples of metal complexes include metal complexes that emit light from a triplet excited state such as iridium complexes and platinum complexes, aluminum quinolinol complexes, benzoquinolinol beryllium complexes, benzoxazolylzinc complexes, benzothiazolezinc complexes, and azomethylzinc complexes. , porphyrin-zinc complex, phenanthroline-europium complex, and the like.

Polymer-based luminescent materials include, for example, polyparaphenylenevinylene or its derivatives, polythiophene or its derivatives, polyparaphenylene or its derivatives, polysilane or its derivatives, polyacetylene or its derivatives, polyfluorene or its derivatives, polyvinylcarbazole or Examples thereof include derivatives thereof, dye materials described above, and materials obtained by polymerizing metal complex materials.

Among the above light-emitting materials, materials that emit red light (hereinafter also referred to as "red light-emitting materials") include, for example, coumarin or derivatives thereof, thiophene ring compounds, polymers thereof, polyparaphenylene vinylene or derivatives thereof. , polythiophene or its derivatives, polyfluorene or its derivatives, and the like. Materials disclosed in Japanese Patent Application Laid-Open No. 2011-105701 can also be used as red light-emitting materials.

Materials that emit green light (hereinafter also referred to as "green light-emitting materials") include, for example, quinacridone or derivatives thereof, coumarin or derivatives thereof, polymers thereof, polyparaphenylene vinylene or derivatives thereof, polyfluorene or derivatives thereof, derivatives and the like. Materials disclosed in Japanese Patent Laid-Open No. 2012-036388 can also be used as green light-emitting materials.

Materials that emit blue light (hereinafter also referred to as “blue light emitting materials”) include, for example, distyrylarylene or derivatives thereof, oxadiazole or derivatives thereof, polymers thereof, polyvinylcarbazole or derivatives thereof, polyparallel Phenylene or derivatives thereof, polyfluorene or derivatives thereof, and the like are included. Materials disclosed in Japanese Unexamined Patent Application Publication No. 2012-144722 are also examples of blue light-emitting materials.

Dopant materials include, for example, perylene or its derivatives, coumarin or its derivatives, rubrene or its derivatives, quinacridone or its derivatives, squalium or its derivatives, porphyrin or its derivatives, styryl dyes, tetracene or its derivatives, pyrazolone or its derivatives, decacyclene or derivatives thereof, phenoxazone or derivatives thereof, and the like.

The organic light emitting layer 23 is provided according to the type of the pixel 2, ie, 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 recess 14 corresponding to the red pixel 2R, and a green light is provided on the hole transport layer 22 of the recess 14 corresponding to the green pixel 2G. An organic light-emitting layer 23 that emits light is provided, and the organic light-emitting layer 23 that emits blue light is provided on the hole transport layer 22 in the recess 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 also 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, the plurality of organic EL structures 20 are provided in recesses 14 (see FIGS. 2 and 3) formed by banks 13 and anodes 12 in substrate 10 with banks. In this embodiment, the organic EL structure section 20 has a hole injection layer 21 , a hole transport layer 22 and an organic light emitting layer 23 .
That is, each pixel 2 is arranged within the bank 13 (inside the recess 14 defined by the bank 13).

In at least one pixel 2, preferably in all pixels 2, the organic light-emitting layer 23 has a shape having a longitudinal direction and a lateral direction in plan view, as shown in FIG. In this specification, "planar view" means viewing from the thickness direction of the layer. In this embodiment, each layer forming the organic EL structure section 20 has the same shape in a plan view.
Examples of the shape having a longitudinal direction and a lateral direction include a rectangle, a rectangular shape with rounded corners, a rectangular shape with at least one side arcuate (for example, arcuate), and an elliptical shape.

In at least one pixel 2, preferably in all pixels 2, the organic light-emitting layer 23 having a shape having a longitudinal direction and a lateral direction in plan view has a cross section parallel to the longitudinal direction passing through the center of the lateral direction. , has a concave shape in which the thickness at the center in the longitudinal direction is smaller than the thickness at both ends (see FIG. 2). By providing such a recessed shape, it is possible to reduce the amount of current injected into the outer peripheral portion of the organic light-emitting layer 23 where leakage and local light emission are likely to occur, thereby suppressing a decrease in specific luminance of the pixel.
The difference between the thickness at both ends in the longitudinal direction and the thickness at the center of the organic light-emitting layer 23 having the concave shape is, for example, 1 nm or more and 20 nm or less, and from the viewpoint of improving luminance and EQE, it is preferably 1 nm or more and 10 nm or less. It is more preferably 1 nm or more and 5 nm or less.
The average thickness of the organic light-emitting layer is, for example, 1 nm or more and 2 μm or less, preferably 5 nm or more and 500 nm or less, and more preferably 10 nm or more and 100 nm or less.

The fact that the organic light-emitting layer 23 has a concave shape can be confirmed by observing the cross section using an optical microscope, for example.
When the organic light-emitting layer 23 is formed in the bank 13 by a coating method, the organic light-emitting layer 23 usually has a concave shape due to the influence of surface tension.

(7) Cathode (second electrode)
A cathode 30 is provided on the organic light-emitting layer 23 . As a material for the cathode 30, a material having a small work function, easy injection of electrons into the organic light-emitting layer 23, and high electrical conductivity is preferable. Further, as described in this embodiment, when the organic EL device 1 extracts light from the anode 12 side, the light emitted from the organic light emitting layer 23 is reflected by the cathode 30 toward the anode 12 side. As a material for the cathode 30, a material having a high visible light reflectance is preferable. For the cathode 30, for example, alkali metals, alkaline earth metals, transition metals, group 13 metals of the periodic table, and the like can be used. Moreover, as the cathode 30, a transparent conductive cathode made of a conductive metal oxide, a conductive organic substance, or the like can be used.

The thickness of the cathode 30 is appropriately set in consideration of electrical conductivity and durability. The thickness of the cathode 30 is, for example, 10 nm or more and 10 μm or less, preferably 20 nm or more and 1 μm or less, and more preferably 50 nm or more and 500 nm or less.
One or more other layers such as an electron injection layer and an electron transport layer 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 from the cathode to the organic light emitting layer. A known electron injection material can be used for the electron injection layer. When the electron injection layer is provided in this manner, an electron transport layer may be provided between the electron injection layer and the organic light-emitting layer. The electron-transporting layer is a layer that has the function of improving electron injection from the cathode, the electron-injecting layer, or an electron-transporting layer closer to the cathode. A known electron transport material can be used for the electron transport layer.

In this embodiment, the cathode 30 is formed over the entire surface of the display area in which 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 provided as a common cathode for the plurality of pixels 2 .

Although not shown in FIGS. 1 and 2, a sealing substrate is usually provided on the cathode 30 of the organic EL device 1. As shown in FIG. In addition, the organic EL device 1 may have other known elements that an organic EL panel display panel has, for example.

(8) Pixel Luminance Characteristics and Luminance Distribution Characteristics In the organic EL device 1, at least one of the plurality of pixels 2 satisfies the following [A] and [B]. Hereinafter, pixels satisfying the following [A] and [B] are also referred to as "specific pixels".
[A] The average luminance is 3000 cd/m ² or more when the current value is 10 mA/cm ² .
[B] The luminance distribution curve in a cross section that passes through the center in the short direction of the organic light-emitting layer 23 and is parallel to the longitudinal direction is normalized by setting the value of the maximum luminance to 1 in the cross section, and the following formula (1):
SL(70)≦0.010 (1)
meet.

The present invention significantly improves the EQE improvement effect in an organic EL device including specific pixels with high luminance efficiency (unit: cd/A) that satisfies the above [A]. The luminance efficiency here is obtained by dividing the value of luminance (unit: cd/m ² ) by the current value (unit: mA/cm ² ).
The average luminance means an average value of luminance over 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 short direction and parallel to the longitudinal direction.
The average luminance when the current value is 10 mA/cm ² is preferably 4000 cd/m ² or more, more preferably 5000 cd/m ² or more.

The average luminance (average luminance efficiency) when the current value is 10 mA/cm ² mainly depends on the type of light-emitting material contained in the organic light-emitting layer 23 . Therefore, as the light-emitting material used for at least one of the organic light-emitting layers 23 of the plurality of pixels 2, for example, among the light-emitting materials exemplified above, the average luminance when the current value is 10 mA/cm ² falls within the above range. Choose and use whatever you want.

To explain [B] above, referring to FIG. 4 showing an example of a brightness distribution curve of a pixel, SL (70) is set to 0 at the center in the longitudinal direction of the organic light-emitting layer (pixel) and 0 at one end in the longitudinal direction. When the position of +100 and the position of the other end in the longitudinal direction is -100, the absolute value of the slope of the luminance distribution curve at position +70 and the absolute value of the slope of the luminance distribution curve at position -70. .
The term "luminance distribution curve" as used herein refers to a curve graph showing the relationship between the position (horizontal axis) in the longitudinal direction of the organic light-emitting layer (pixel) and the luminance (vertical axis) at that position. Normalization is performed by setting the value of the maximum luminance at the center in the longitudinal direction of the organic light emitting layer 23 to 1 (see FIG. 4).

The slope of the luminance distribution curve at the position +70 is five coordinate points (+68.4, luminance at this position), (+69.2, (brightness at this position), (+70.0, brightness at this position), (+70.8, brightness at this position) and (+71.6, brightness at this position). means tilt.
Similarly, the slope of the luminance distribution curve at position -70 is five coordinate points (-71.6, luminance at this position), (-70.8, luminance at this position), (-70.0, this (-69.2, luminance at this position), (-69.2, luminance at this position), and (-68.4, luminance at this position).

A specific pixel satisfying [A] and [B] and an organic EL device including the same have higher EQE than a pixel satisfying [A] but not [B] and an organic EL device including the same. can be shown. This is presumed to be due to the fact that the proportion of the area where the EQE emits light is reduced and the proportion of the area where the EQE emits light increases in the pixel.

SL (70) is preferably 0.008 or less, more preferably 0.005 or less, still more preferably 0.003 or less, and particularly preferably 0.002 or less, from the viewpoint of the EQE improvement effect. be.
SL(70) is preferably near zero.

In order to obtain the EQE improvement effect more remarkably, the specific pixel preferably satisfies [A] and [B] and satisfies [C] below.
[C] A graph showing the relationship between the amount of current supplied to the pixel (unit: mA/cm ² ) and the average luminance (unit: cd/m ² ) on the vertical axis, showing the relationship between the amount of current supplied to the pixel and the average luminance , as the amount of current increases, the value obtained by dividing the average luminance value at that current value by that current value (that is, the slope at that current value in the graph above, which means the average luminance efficiency at that current value ) gradually decreases.
There is a tendency that the greater the degree of decrease, the greater the effect of improving EQE.

According to studies by the present inventors, the position for obtaining the slope of the luminance distribution curve is the edge of the organic light-emitting layer, for example, when the absolute value exceeds 80 (the position is 100 in absolute value). It has been clarified that there is no relationship between the slope of the luminance distribution curve and the EQE when it is close to the edge or due to factors such as disturbance.
It has been clarified that even when the absolute value of the position for obtaining the slope of the luminance distribution curve is less than 60, there is no relationship between the slope of the luminance distribution curve and the EQE.
On the other hand, when the position for obtaining the slope of the luminance distribution curve is, for example, 60 or more and 80 or less in absolute value, the above relationship can be recognized, especially when the absolute value is 70, the relationship It has become clear that there is a significant difference in EQE between when SL(70) is 0.010 or less and when it is not.

In the present invention, when the organic EL device has a plurality of pixels, if at least one pixel is a specific pixel, the EQE improvement effect can be obtained for that pixel. However, from the viewpoint of improving the EQE as an organic EL device, the organic EL device preferably has two or more specific pixels, and more preferably has as many specific pixels as possible.
From the viewpoint of the EQE improvement effect as an organic EL device and the productivity improvement of the organic EL device, whether all red pixels 2R are specific pixels or all green pixels 2G are specific pixels, Alternatively, all blue pixels 2B are preferably specific pixels. In particular, the green pixel 2G tends to increase in brightness due to the characteristics of the luminosity curve, so it is preferable that the green pixel 2G be the specific pixel, and it is more preferable that the red pixel 2R and the blue pixel 2B be the specific pixels in this order. Furthermore, it is particularly preferable that two or more pixels selected from the group consisting of all red pixels 2R, all green pixels 2G and all blue pixels 2B are specific pixels.

In the above description, the first electrode and the second electrode of the banked substrate are the anode and the cathode, respectively, but the first electrode and the second electrode may be the cathode and the anode, respectively. Moreover, in the above description, the organic EL device has three types of pixels, 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 are the same. Color may be emitted.
In the above description, the hole injection layer and the hole transport layer were formed between the organic light-emitting layer and the electrode of the banked substrate, but they do not have to be formed. For example, an organic light-emitting layer may be formed adjacent to the electrodes that the banked substrate has. Alternatively, the hole-transporting layer may not be formed, and the organic light-emitting layer may be formed adjacent to the hole-injecting layer.
Examples of organic EL devices are not limited to organic display panels, and may be organic light emitting devices.

<Method for manufacturing organic EL device>
Next, a method for manufacturing the organic EL device 1 will be described. Here, a method for manufacturing the organic EL device 1 after preparing the banked substrate 10 will be described.
The method for manufacturing the organic EL device 1 includes a step of forming pixels, and the steps of forming pixels include the following steps.
a step of forming an organic light-emitting layer 23 on the anode (first electrode) 12 (organic light-emitting layer forming step) S101;
A step of forming a cathode (second electrode) 30 on the organic light emitting layer 23 (cathode forming step) S102, and a step S103 of inspecting the obtained pixels.

In manufacturing the organic EL device 1, first, after preparing the banked substrate 10, before step S101, a step of forming the organic structure 40 on the anode (first electrode) 12 (organic structure forming step). S100 is implemented. In the organic structure forming step S10, as shown in FIG. 5, a hole injection layer 21 and a hole transport layer 22 are formed on the anode 12 provided in the pixel region 2a, in other words, provided in the concave portion 14. are formed in this order by a coating method to fabricate an organic structure 40 that is a laminate of the hole injection layer 21 and the hole transport layer 22 . Organic structure 40 is part of a pixel.

Specifically, a coating liquid containing a hole injection material is dropped onto the anode 12 of the concave portion 14 to form a coating film, and then the coating film is dried to form the hole injection layer 21 .

Examples of the coating method include an inkjet printing method. However, other known coating methods, such as micro gravure coating, gravure coating, bar coating, roll coating, wire bar coating, and spray coating, can be used as long as they are coating methods capable of forming a layer in the recess 14. , screen printing, flexographic printing, offset printing, and nozzle printing, preferably screen printing, flexographic printing, offset printing, and nozzle printing.

The solvent used in the coating solution is not limited as long as it can dissolve the hole injection material. Examples include chloride solvents such as chloroform, methylene chloride, and dichloroethane; 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.

A method for drying the coating film is not limited as long as the coating film can be dried, and examples thereof include vacuum drying and heat drying.

Next, a coating liquid containing a hole transport material is dropped onto the hole injection layer 21 in the recess 14 to form a coating film, and then the coating film is dried to form the hole transport layer 22 . Examples of solvents and drying methods can be the same as for the hole injection layer 21 .

After performing the organic structure forming step S100, the 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 formed on the organic structure 40, preferably by a coating method.
Specifically, a coating liquid containing a light-emitting material to be the organic light-emitting layer 23 is dropped in the bank 13, that is, on the hole transport layer 22 in the recess 14 to form a coating film, and then the coating film is dried. Then, the organic light-emitting layer 23 is formed.
In the concave portions 14 corresponding to the red pixel 2R, the green pixel 2G and the blue pixel 2B, the red light emitting layer 23R and the green light emitting layer 23R and the green light emitting layer are formed by using coating liquids containing a red light emitting material, a green light emitting material and a blue light emitting material, respectively. 23G and a blue light emitting layer 23B are formed.

As an application method, an inkjet printing method is exemplified, but other known application methods exemplified for the hole injection layer 21 can also be used. The solvent used for the coating liquid is not limited as long as it can dissolve the light-emitting material, and may be the same as the solvents exemplified for the formation 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 in the same manner as in the case of the hole injection layer 21, but examples thereof include vacuum drying and heat drying.

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 recess 14 by the organic light emitting layer forming step S101.

As described above, in at least one pixel 2, preferably in all pixels 2, the organic light-emitting layer 23 has a shape having a longitudinal direction and a lateral direction in plan view. In the organic EL device 1 according to this embodiment, each layer forming the organic EL structure section 20 has the same shape in plan view.
Further, as described above, in at least one pixel 2, preferably in all pixels 2, the organic light-emitting layer 23 having a shape having a longitudinal direction and a lateral direction in plan view has a longitudinal direction passing through the center of the lateral direction. In a cross section parallel to the direction, it has a concave shape in which the thickness at the center in the longitudinal direction is smaller than the thickness at both ends (see FIG. 6).
When the organic light-emitting layer 23 is formed in the bank 13 by a coating method, the organic light-emitting layer 23 usually has a concave shape due to the influence of surface tension.

In the organic light-emitting layer forming step S101, the organic light-emitting layer 23 is formed so that at least one of the plurality of pixels 2 satisfies the above [A]. In order to satisfy the above [A], the organic light-emitting layer 23 is formed by selecting, for example, from among the light-emitting materials exemplified above, a light-emitting material having an average luminance in the above range at a current value of 10 mA/cm ² . . For the details of [A], the above description is cited.

After forming the organic light emitting layer 23, the step of forming the cathode (second electrode) 30 (cathode forming step) S102 is performed. Methods for forming the cathode 30 include, for example, vapor deposition and coating methods similar to those for the anode 12 . In this step, the cathode 30 is formed over the organic light emitting layer 23 formed in the plurality of recesses 14 . As a result, the organic EL device 1 shown in FIGS. 1 and 2 in which the pixels 2 are formed in the banks 13 is obtained.

After the cathode formation step S102, a step (inspection step) S103 of inspecting the obtained pixels is performed. The inspection step S103 acquires information about the slope of the luminance distribution curve in a cross section parallel to the longitudinal direction passing through the center of the short side direction of the organic light emitting layer 23 included in the pixel, and determines whether the pixel is good or bad based on the information. including the step of As for the luminance distribution curve, the above description is cited.
According to the method of measuring the luminance distribution curve of a pixel and determining the quality of the pixel based on the information obtained from the curve, the shape (for example, thickness, thickness distribution, etc.) of the organic light-emitting layer 23 itself is measured, and the measurement is performed. The productivity of the organic EL device 1 can be improved because the quality determination can be performed more simply and easily than the method of determining the quality of the pixels based on the result.

The information about the slope of the brightness distribution curve is preferably information about the slope of the brightness distribution curve at a position of 60 or more and 80 or less in absolute value, more preferably the slope of the brightness distribution curve at a position of 70 in absolute value. , namely SL (70). By selecting the information on the slope of the brightness distribution curve at a position with an absolute value of 60 or more and 80 or less, especially SL(70), as the information on the slope of the brightness distribution curve, it is possible to easily judge whether the pixel is good or bad, and By using whether or not the expression (1) is satisfied as the quality judgment criterion, an organic EL device with good EQE can be produced with high accuracy.
SL(70), its range and preferred range, and formula (1) are referred to above.

As a method of forming pixels so as to satisfy the above [B], in the formation of the organic light emitting layer 23, the pressure reduction profile in the process of vacuum drying the coating film (exhaust time in the operation of reducing pressure while exhausting the gas in the drying furnace and the degree of vacuum in the drying oven) and/or adjusting the drying temperature. For example, as an example, it is advantageous to form a pixel that satisfies [B] by increasing the depressurizing speed or setting the drying temperature to a relatively low level.
In the inspection step S103 performed for the pixels satisfying the above [A], for example, whether or not the above formula (1) is satisfied is used as a pass/fail judgment criterion, and if SL(70) exceeds 0.010, the above [B] is satisfied. In order to achieve this, it is preferable to perform the step of adjusting the formation of the organic light-emitting layer 23 as described above.

From the viewpoint of improving EQE, the organic EL device obtained by the manufacturing method according to the present invention includes at least one specific pixel, that is, a pixel that satisfies the above [A] and [B]. However, from the viewpoint of improving the EQE as an organic EL device, the organic EL device preferably has two or more specific pixels, and more preferably has as many specific pixels as possible.
From the viewpoint of the EQE improvement effect as an organic EL device and the productivity improvement of the organic EL device, whether all red pixels 2R are specific pixels or all green pixels 2G are specific pixels, Alternatively, all blue pixels 2B are preferably specific pixels. In particular, the green pixel 2G tends to increase in brightness due to the characteristics of the luminosity curve, so it is preferable that the green pixel 2G be the specific pixel, and it is more preferable that the red pixel 2R and the blue pixel 2B be the specific pixels in this order. Furthermore, it is particularly preferable that two or more pixels selected from the group consisting of all red pixels 2R, all green pixels 2G and all blue pixels 2B are specific pixels.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example 1>
A hole injection layer 21, a hole transport layer 22 and an organic light emitting layer 23 are formed in a plurality of concave portions 14 of a substrate 10 with banks from the anode 12 side, and a cathode 30 is formed on the organic light emitting layer 23 to form a plurality of pixels. was made. An organic EL device was thus obtained. The hole injection layer 21, the hole transport layer 22, and the organic light-emitting layer 23 were formed by forming a coating film using a coating liquid corresponding to each layer by an inkjet printing method, followed by vacuum drying. A green light-emitting layer 23G was used as the organic light-emitting layer 23 in each recess 14 . The organic EL structural portion 20 forming a pixel has a shape having a longitudinal direction and a lateral direction in plan view.
As a result of confirmation using a non-contact three-dimensional surface profile measuring device (manufactured by Zygo), the thickness of the organic light-emitting layer 23 in a cross section parallel to the longitudinal direction passing through the center of the longitudinal direction is the thickness at the center in the longitudinal direction. It had a concave shape smaller than The same was true in Example 2, Comparative Examples 1 and 2, and Reference Examples 1 and 2 below.

The same hole injection material, hole transport material and green light emitting material were used for the hole injection layer 21, the hole transport layer 22 and the organic light emitting layer 23 in the plurality of pixels 2 thus formed. The temperature in the vacuum chamber was 25° C. in the vacuum drying performed when forming the organic light emitting layer 23 . Also, the pressure reduction profile in the vacuum chamber in this vacuum drying was as shown in FIG.

<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 when forming the organic light-emitting layer 23 was 35°C. 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 in Examples 1 and 2, respectively.

<Comparative Example 1>
An organic EL device 1 was produced in the same manner as in Example 1, except that the pressure reduction profile in the vacuum chamber in the vacuum drying performed when forming the organic light emitting layer 23 was set as shown in FIG. 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 in Example 1 and Comparative Example 1, respectively.

<Comparative Example 2>
An organic EL device 1 was produced in the same manner as in Example 1, except that the pressure reduction profile in the vacuum chamber in the vacuum drying performed when forming the organic light emitting layer 23 was set as shown in FIG. 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 in Example 1 and Comparative Example 2, respectively.

<Reference example 1>
A hole injection layer 21, a hole transport layer 22 and an organic light emitting layer 23 are formed in a plurality of concave portions 14 of a substrate 10 with banks from the anode 12 side, and a cathode 30 is formed on the organic light emitting layer 23 to form a plurality of pixels. was made. An organic EL device was thus obtained. The hole injection layer 21, the hole transport layer 22, and the organic light-emitting layer 23 were formed by forming a coating film using a coating liquid corresponding to each layer by an inkjet printing method, followed by vacuum drying. A blue light-emitting layer 23B was used as the organic light-emitting layer 23 in each recess 14 . The organic EL structural portion 20 forming a pixel has a shape having a longitudinal direction and a lateral direction in plan view.

The same hole injection material, hole transport material and blue light emitting material were used for the hole injection layer 21, the hole transport layer 22 and the organic light emitting layer 23 in the plurality of pixels 2 thus formed. The temperature in the vacuum chamber was 35° C. in the vacuum drying performed when forming the organic light-emitting layer 23 . Also, the pressure reduction profile in the vacuum chamber in this vacuum drying was as shown in FIG.

<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 when forming the organic light-emitting layer 23 was 55°C. 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 in Reference Examples 1 and 2, respectively.

[Measurement/Evaluation]
(1) Average luminance when the current value is 10 mA/cm ² Using a two-dimensional color luminance meter manufactured by Radiant Vision Systems, applied current [unit: mA] and light emission for one of a plurality of pixels The average luminance [unit: cd/m ² ] was determined when the current value obtained from the area [unit: cm ² ] was 10 mA/cm ² . Table 1 shows the results. The average luminance was obtained for a cross section parallel to the longitudinal direction passing through the center of the organic light-emitting layer 23 in the lateral direction.

(2) Luminance distribution curve and SL(70)
About the pixel which performed the measurement of said (1), the luminance distribution in a pixel was acquired using the two-dimensional color luminance meter by the Radiant Vision Systems company, and the luminance distribution curve was calculated|required. For the luminance distribution curve, the average luminance was obtained for a cross section parallel to the longitudinal direction passing through the center of the organic light-emitting layer 23 in the lateral direction.
Also, SL(70) was obtained from the obtained luminance distribution curve according to the above definition. Table 1 shows the results.

(3) EQE
EQE was obtained from the voltage [unit: V], the current [unit: mA] and the emission spectrum using a two-dimensional color luminance meter manufactured by Radiant Vision Systems for the pixels subjected to the measurement in (1) above. Table 1 shows the results.

1 organic EL device, 2 pixel, 2a pixel region, 2R red pixel, 2G green pixel, 2B blue pixel, 10 substrate with bank, 11 substrate, 11a surface of substrate, 12 anode (first electrode), 13 bank, 13a Bank Side 14 Recess 20 Organic EL Structure Part 21 Hole Injection Layer 22 Hole Transport Layer 23 Organic Light Emitting Layer 30 Cathode (Second Electrode) 40 Organic Structure.

Claims (4)

A method for manufacturing an organic EL device, comprising forming a pixel including a first electrode, an organic light-emitting layer, and a second electrode,
The organic EL device comprises a substrate and a bank provided on the substrate for defining the pixel,
the pixels are arranged in the bank;
The step of forming the pixels includes:
forming the organic light-emitting layer on the first electrode;
forming the second electrode on the organic light-emitting layer;
inspecting the resulting pixels;
including
The organic light-emitting layer has a shape having a longitudinal direction and a lateral direction in plan view, and in a cross section passing through the center in the lateral direction and parallel to the longitudinal direction, the thickness at the center in the longitudinal direction is formed to have a concave shape that is smaller than the thickness;
the pixel has a luminance of 3000 cd/m ² or more at a current value of 10 mA/cm ² ;
The inspecting step includes acquiring information about the slope of a luminance distribution curve in the cross section of the pixel and performing quality determination of the pixel based on the information ,
In the step of performing the quality judgment,
When the position of the center in the longitudinal direction is 0, the position of one end in the longitudinal direction is +100, and the position of the other end in the longitudinal direction is -100,
A method for manufacturing an organic EL device, wherein quality determination of the pixel is performed based on information regarding a slope of a luminance distribution curve at a position of 60 or more and 80 or less in absolute value . In the step of determining whether the pixel is good or bad, the luminance distribution curve in the cross section when the pixel is normalized by the luminance at the center in the longitudinal direction,
When the position of the center in the longitudinal direction is 0, the position of one end in the longitudinal direction is +100, and the position of the other end in the longitudinal direction is -100,
2. Determination of whether the pixel is good or bad based on an average value of the absolute value of the slope of the luminance distribution curve at position +X and the absolute value of the slope of the luminance distribution curve at position -X, where 60≦X≦80. 2. A method for manufacturing the organic EL device according to 1. In the step of determining the quality of the pixel, the luminance distribution curve in the cross section when the pixel is normalized by the luminance at the center in the longitudinal direction is expressed by the following formula (1):
SL(70)≦0.010 (1)
[In the formula, SL(70) is the luminance distribution at position +70 when the position of the center in the longitudinal direction is 0, the position of one end in the longitudinal direction is +100, and the position of the other end in the longitudinal direction is −100. It represents the mean value of the absolute value of the slope of the curve and the absolute value of the slope of the luminance distribution curve at position -70. ]
3. The method of manufacturing an organic EL device according to claim 1 , wherein the quality determination of the pixel is performed based on whether or not the condition is satisfied. 4. The method for manufacturing an organic EL device according to claim 1 , wherein an organic light-emitting layer is formed on said first electrode by a coating method.

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