JP2015228456A - Organic EL element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element capable of suppressing a degree of brightness unevenness generated when a deviation of a film thickness attributed to a deposition method and such is generated in a functional layer without adding complex steps such as deposition of a light-sensitive resin, masking, and etching.SOLUTION: The organic EL element is formed by laminating a first electrode layer having light reflectivity, a functional layer having at least a light-emitting layer, and a second electrode layer having light transparency in this order. The functional layer includes a plurality of nanoparticles. A thickness of the functional layer is thicker than a thickness of a part where the nanoparticles do not exist.

Description

  The present invention relates to an organic EL (electroluminescence) element utilizing an electroluminescence phenomenon of an organic material.

In the organic EL element, the thickness of a functional layer such as a light emitting layer is optimized in order to obtain good light emission characteristics. However, if the film thickness of the functional layer deviates from the optimum condition due to variations in film forming conditions, the light emission characteristics change.
Patent Document 1 relates to a light emitting device in which an optical resonator is formed in a light emitting region. As shown in FIG. 13, the organic EL element 1300 includes a light transmissive substrate 1301, a light transmissive electrode 1302, a hole injection layer 1303 and a light emitting layer 1304 constituting a functional layer, a light reflective electrode 1305, and a semi-transmissive. It consists of a reflective film 1306 and a concavo-convex forming layer 1307. An optical resonator 1320 is formed between the lower reflective layer made of the semi-transmissive reflective film 1306 and the upper reflective layer made of the light reflective electrode 1305.

  In the organic EL element 1300, by providing the concavo-convex forming layer 1307, the film thickness of the functional layer varies depending on the position in the light emitting region (for example, film thicknesses d1, d2, and d3 in FIG. 13). Therefore, an emission spectrum corresponding to each film thickness is synthesized and emitted from the emission region. Therefore, even when the film thickness of the functional layer deviates from the optimum value due to the film formation conditions when forming the functional layer, the emission spectra of the respective film thicknesses are synthesized and emitted, and only the composition ratio is shifted. Therefore, it is possible to minimize the shift of the wavelength of the emitted light due to the film thickness variation.

JP 2006-269251 A

  The inventors have found that when examining the increase in the area of the organic EL element, there is a problem that uneven brightness occurs in the light emitting region due to uneven film thickness of the functional layer. One embodiment of the present disclosure provides an organic EL element in which uneven luminance is reduced even when uneven thickness of a functional layer occurs.

  An organic EL element according to one embodiment of the present disclosure is an organic EL element in which a first electrode layer having light reflectivity, a functional layer including at least a light emitting layer, and a second electrode layer having light transmissivity are stacked in this order. The functional layer has a plurality of nanoparticles, and the thickness of the functional layer is larger than the thickness of the portion where the nanoparticles are not present.

  According to the organic EL device according to one embodiment of the present disclosure, even when the thickness of the functional layer is uneven, the occurrence of uneven brightness can be reduced.

It is a schematic diagram which illustrates the structure of the organic EL element which concerns on one Embodiment of this invention. It is a schematic diagram which illustrates the spin coater used for film-forming of the light emitting layer of an organic EL element. It is a schematic diagram for demonstrating the structure of the organic EL element at the time of forming into a film by the spin coat method without including a nanoparticle in a light emitting layer. It is a schematic diagram for demonstrating the structure of the organic EL element at the time of forming into a film by the spin coat method including a nanoparticle in a light emitting layer. It is a figure which shows the optical parameter and structural parameter which are used for the simulation about the brightness | luminance and chromaticity of an organic EL element. It is a figure which shows the simulation result about the brightness | luminance and chromaticity of an organic EL element. (A)-(d) is schematic which shows each process of the manufacturing method of the organic EL element which concerns on embodiment. (A)-(c) is the schematic which shows each process of the manufacturing method of the organic EL element which concerns on embodiment (continuation of FIG. 7). It is a schematic diagram which illustrates the structure of the organic EL element which concerns on a modification. (A)-(c) is schematic which shows each process of the manufacturing method which concerns on the modification of an organic EL element. (A)-(c) is the schematic which shows each process of the manufacturing method which concerns on the modification of an organic EL element (continuation of FIG. 10). It is a schematic diagram for demonstrating the structure of the organic EL element manufactured with the manufacturing method which concerns on a modification. It is a schematic diagram which shows the structure of the conventional organic EL element.

<1. Embodiment>
<1-1. Outline of Organic EL Element 1 According to this Embodiment>
Hereinafter, the organic EL element 1 according to the present embodiment will be described. The organic EL element 1 is a so-called top emission type organic EL element. As shown in FIG. 1, the organic EL element 1 includes a first electrode 12 stacked on a substrate 11, a second electrode 16 provided above the substrate 11 so as to face the first electrode 12, and a first electrode And a functional layer 15 disposed between the electrode 12 and the second electrode 16. As shown in FIG. 1, the functional layer 15 is formed by laminating a light emitting layer 13 and a second carrier injection layer 14 in this order from the first electrode 12 side.

  The first electrode 12 is a reflective electrode having light reflectivity. The second electrode 16 is a transparent electrode having optical transparency, and is formed on the functional layer 15. The first electrode 12 is a cathode and the second electrode 16 is an anode. In the organic EL element 1, when a voltage is applied between the first electrode 12 and the second electrode 16, first carriers (specifically, electrons) are injected from the first electrode 12, and from the second electrode 16. Second carriers (specifically, holes) are injected. The injected first carrier and second carrier recombine in the vicinity of the interface of the light emitting layer 13 with the second carrier injection layer 14 to emit light. Of the light emitted from the light emitting layer 13, light emitted in the direction of the second electrode 16 (hereinafter referred to as “direct light”) is emitted to the outside of the organic EL element 1 through the second electrode 16. On the other hand, when light (hereinafter referred to as “reflected light”) emitted from the light emitting layer 13 toward the first electrode 12 reaches the first surface of the first electrode 12, it is reflected by the first surface and travels toward the second electrode 16. Then, the light is emitted to the outside of the organic EL element 1 through the second electrode 16. An optical resonator is formed between the first electrode 12 and the second electrode 16, and light whose optical length corresponds to an integral multiple of a half wavelength is emitted. Further, the direct light and the reflected light interfere with each other, and depending on the degree of interference, the luminance (hereinafter referred to as “light emission”) that appears on the surface (hereinafter referred to as “light emitting surface”) facing the surface of the second electrode 16 in contact with the functional layer 15. "Luminance") changes. The degree of interference between the direct light and the reflected light is determined according to the film thickness of the functional layer 15 (or the optical distance between the first electrode 12 and the second electrode 16). When the film thickness of the functional layer 15 is not uniform and varies depending on the position in the functional layer 15, the light emission luminance also varies depending on the position in the functional layer 15.

  Here, as an example, the light emitting layer 13 is formed by spin coating using a spin coater (see the spin coater 200 in FIG. 2). In the spin coating method, the substrate 11 on which the first electrode 12 is formed (corresponding to the wafer 202 in FIG. 2) is placed on the spinner 201 in the cup 203 with the surface on which the first electrode 12 is formed facing upward. Then, the surface of the wafer 202 where the first electrode 12 is not formed is fixed with a vacuum chuck attached to the spinner 201. Then, the light emitting layer 13 is formed on the wafer 202 by dropping a predetermined amount of the material of the light emitting layer 13 from the nozzle unit 204 while rotating the spinner 201 at a high speed.

In general, the thickness of the light emitting layer formed by spin coating is the thickest at the rotation center and the vicinity thereof, and the film thickness decreases as the distance from the rotation center increases.
FIG. 3 is a schematic diagram illustrating an example of an organic EL element 300 in which a light emitting layer is formed by spin coating. The organic EL element 300 includes a first electrode 312 stacked on a substrate 311, a second electrode 316 provided above the substrate 311 so as to face the first electrode 312, and a first electrode 312 and a second electrode 316. And a functional layer 315 disposed between the two. The functional layer 315 is formed by laminating a light emitting layer 313 and a second carrier injection layer 314 in this order from the first electrode 312 side.

  As an example, as shown in FIG. 3, in the light emitting layer 313, the film thickness of the portion (first portion 321) corresponding to the rotation center (axis 301) of the wafer 202 is the largest, and the film thickness increases every time the distance from the rotation center increases. Is thinner. In the light emitting layer 313, the film thickness of the first portion 321 corresponding to the rotation center is 80 nm, the film thickness of the part 2.5 cm away from the rotation center is 75 nm, and the film thickness of the part 5 cm away from the rotation center is 70 nm.

  On the other hand, in the organic EL element 1, the light emitting layer 13 has a plurality of nanoparticles 20 a, 20 b, 20 c and the like (hereinafter also collectively referred to as “nanoparticles 20”) on the first electrode 12 as shown in FIG. Are dispersed in advance and an organic material is applied thereon. That is, the light emitting layer 13 is a layer containing the nanoparticles 20. Here, in the organic EL element 1, even if the nanoparticle 20 is used, the film thickness of the functional layer 15 including the light emitting layer 13 is varied. Specifically, the film thickness of the functional layer 15 in the portion (hereinafter referred to as “particle existence portion”) 32 where the nanoparticles 20 exist between the first electrode 12 and the second electrode 16 of the organic EL element 1 is as follows. A portion where the nanoparticles 20 are not present between the first electrode 12 and the second electrode 16 other than the vicinity 33 (including 33a and 33b as an example) in the vicinity of the particle existing portion (hereinafter referred to as “particle non-existing portion”). 31 is thicker than the film thickness of the functional layer 15. Further, in the vicinity 33 of the particle existence portion 31, the film thickness of the functional layer 15 continuously changes in a range from the film thickness of the particle non-existence portion 31 to the film thickness of the particle existence portion 32. For this reason, the organic EL element 1 emits light having a light emission characteristic corresponding to the film thickness of the functional layer 15 at each position of the light emitting region. It is the combined light of these lights that is actually observed by the human eye. Here, if the thickness of the functional layer changes in the entire light emitting region, the light emission characteristics at the respective positions in the light emitting region also change. The thickness of the functional layer is set so that the change in the light emission characteristics of the combined light from these positions is smaller than the change when the thickness of the functional layer is made uniform. Thereby, the change of the light emission characteristic as a whole can be made small.

Therefore, even if a change in the thickness of the functional layer occurs over a wide range that can be visually recognized due to the film formation method, the change in the light emission characteristics is relieved by the microscopic change in the thickness due to the nanoparticles. Can be eliminated.
In addition, in the organic EL element 1, a simple method of reducing the degree of luminance unevenness described above without including complicated processes such as film formation, masking, and etching of a photosensitive resin and including nanoparticles in the functional layer 15. Has been realized. Hereinafter, the organic EL element 1 will be described in detail.
<1-2. Configuration of Organic EL Element 1>
Hereinafter, each component of the organic EL element 1 will be described in detail.
<1-2-1. Substrate 11>
The substrate 11 is, for example, a rectangular plate-shaped glass substrate. Examples of the glass substrate material include soda lime glass and non-alkali glass. The substrate 11 may be rigid or flexible. Moreover, the board | substrate 11 is not limited to rectangular plate shape, For example, plate shape of shapes other than rectangular shapes, such as a polygon, a circle, or an ellipse, may be sufficient. The vertical or horizontal dimension of the substrate 11 is, for example, about several tens of millimeters to several tens of inches, and may be appropriately selected according to the required width of the light emitting surface, application, size of manufacturing equipment, and the like.

Moreover, the board | substrate 11 is not limited to a glass substrate, For example, a plastic plate etc. may be sufficient. Furthermore, when the substrate 11 is a plastic plate, it is preferable to suppress the permeation of moisture by using a surface on which a protective film such as a SiON film or a SiN film is formed. Examples of the material for the plastic plate include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, and polycarbonate.
<1-2-2. First electrode 12>
The first electrode 12 is an electrode for injecting the first carrier into the functional layer 15 and functions as a reflective electrode. Since the first electrode 12 is a cathode, it is preferable to use, as a material, an electrode material made of a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function. LUMO (Lowest Unoccupied Molecular Orbital) level It is preferable to use a work function having a work function of 1.9 eV or more and 5 eV or less so that the difference between is not too large. The first electrode 12 is a reflective electrode, and is preferably a metal having a high reflectance with respect to light emitted from the light emitting layer 13 and a low resistivity, and therefore, aluminum or silver is preferable.

In addition, as a material of the first electrode 12, for example, aluminum, silver, or a compound containing these metals can be used. Moreover, you may comprise as a laminated structure etc. combining aluminum and another electrode material. The electrode material combination includes a laminate of an alkali metal thin film and an aluminum thin film, a laminate of an alkali metal thin film and a silver thin film, a laminate of an alkali metal halide thin film and an aluminum thin film, an alkali Examples include a laminate of a metal oxide thin film and an aluminum thin film, a laminate of an alkaline earth metal or rare earth metal thin film and an aluminum thin film, and an alloy of these metal species with another metal. More specifically, for example, a laminated body of a thin film of sodium, sodium-potassium alloy, lithium, magnesium or the like and an aluminum thin film, a magnesium-silver mixture, a magnesium-indium mixture, an aluminum-lithium alloy, a lithium fluoride thin film And a thin film of aluminum and a thin film of aluminum and a thin film of aluminum oxide. The first electrode 12 may be manufactured by a thin film process such as a vacuum evaporation method, or may be manufactured by a wet process such as a spin coating method or a dipping method.
<1-2-3. Functional layer 15>
The functional layer is a layer including at least a light emitting layer. The functional layer 15 includes a light emitting layer 13 and a second carrier injection layer 14.

(1) Light emitting layer 13
The light emitting layer 13 has a function of emitting light including a component having a wavelength of visible light. The light emitting layer 13 includes nanoparticles 20 and light emitting portions 21 other than the nanoparticles 20.
(A) Light emitting unit 21
The light emitting unit 21 may be configured by doping three kinds of dopant dyes of red, green, and blue, or a blue hole transporting light emitting layer, a green electron transporting light emitting layer, and a red electron transporting light emitting layer. You may laminate and comprise. Examples of the material of the light emitting unit 21 include polyfluorene derivatives, polyvinylcarbazole derivatives, dye bodies, and metal complex light emitting materials such as polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, and polyacetylene derivatives. Anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, coumarin, oxadiazole , Bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-mes Ru-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, pyran, quinacridone, Rubrene, and derivatives thereof, or 1-aryl-2,5-di (2-thienyl) pyrrole derivatives, distyrylbenzene derivatives, styrylarylene derivatives, styrylamine derivatives, and groups comprising these luminescent compounds are molecules And the like.

Further, not only compounds derived from fluorescent dyes typified by the above compounds, but also so-called phosphorescent materials, for example, luminescent materials such as iridium complexes, osmium complexes, platinum complexes, europium complexes, or compounds or polymers having these in the molecule Can also be suitably used. These materials can be appropriately selected and used as necessary.
The light emitting unit 21 is preferably formed by a wet process such as a coating method (for example, spin coating method, spray coating method, die coating method, gravure printing method, screen printing method, etc.). The film is formed by spin coating. However, the film forming method of the light emitting unit 21 is not limited to the coating method, and may be formed by a dry process such as a vacuum evaporation method or a transfer method.

(B) Nanoparticle 20
The nanoparticles 20 are particles that are used to locally and continuously change the film thickness of the light emitting layer 13. Here, the term “locally” means that the film thickness of the light emitting layer 13 is, for example, 80 nm due to the film forming method when the organic EL element 1 is viewed as a whole as described with reference to FIG. This is because it changes continuously in the range of ˜70 nm and is distinguished from this.

  The particle diameter of the nanoparticles 20 is such that the film thickness of the portion where the nanoparticles 20 do not exist between the first electrode 12 and the second electrode 16 in the light emitting layer 13 and the second electrode 16 in order to prevent leakage and short circuit. It is desirable that the thickness be equal to or less than the sum of the thicknesses, particularly 10 nm to 200 nm. The average particle diameter of the nanoparticles 20 is 100 nm as an example. The total volume of the nanoparticles 20 occupies 25% of the entire volume of the light emitting layer 13. The material of the nanoparticles 20 may be any material that can be contained in the functional layer 15, and is preferably a material that transmits light and has no absorption. As a material of the nanoparticle 20, for example, a metal oxide, particularly silica particles can be used. Further, in view of facilitating inclusion and dispersion in the functional layer 15, those having a functional group on the surface are more preferable. For example, mesoporous silica particles can be used.

(2) Second carrier injection layer 14
The second carrier injection layer 14 is a hole injection layer. Examples of the material of the second carrier injection layer 14 include organic materials including thiophene, triphenylmethane, hydrazoline, amyramine, hydrazone, stilbene, triphenylamine, and the like. Specifically, for example, polyvinyl carbazole, polyethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS), aromatic amine derivatives such as TPD, etc., these materials may be used alone, or two or more kinds of materials. May be used in combination. When such a material is used, the second carrier injection layer 14 can be formed by a wet process such as a coating method (spin coating method, spray coating method, die coating method, gravure printing method, or the like).

<1-2-4. Second electrode 16>
The second electrode 16 is an electrode formed on the functional layer 15 for injecting second carriers into the functional layer 15. Examples of the material of the second electrode 16 include fine particles of metal such as silver, indium-tin oxide (ITO), indium-zinc oxide (IZO), tin oxide, and gold, a conductive polymer, and a conductive organic material. , Organic materials containing dopants (donor or acceptor), mixtures of conductors and conductive organic materials (including polymer materials), mixtures of these conductive materials and non-conductive materials, etc. It is not limited to. Non-conductive materials include acrylic resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, diacryl phthalate resin , Cellulose resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and copolymers of two or more monomers constituting these resins, but are not limited thereto. It is not something.

Further, doping using a dopant may be performed in order to increase conductivity. Examples of the dopant include, but are not limited to, sulfonic acid, Lewis acid, proton acid, alkali metal, alkaline earth metal, and the like.
<1-3. Simulation for reducing uneven brightness>
The inventors of the present invention conducted a simulation for examining the improvement in luminance unevenness caused by including nanoparticles in the functional layer of the organic EL element in which the thickness of the light emitting layer is uneven. As a simulation method, the one described in Japanese Patent No. 4989366 is used.

First, an organic EL element model used for simulation will be described. The simulation is performed for two models for comparison. The first model is an organic EL element (300) that does not contain nanoparticles in the light emitting layer. A 2nd model is the organic EL element 400 which contains a nanoparticle in a light emitting layer corresponding to the above-mentioned organic EL element 1 as an example.
In the simulation, for each of the organic EL elements 300 and 400, a portion near the rotation center axis of the spin coating method (hereinafter referred to as “first portion”), a portion 2.5 cm away from the rotation center axis (hereinafter referred to as “second portion”). ), And the luminance at a portion 5 cm away from the rotation center axis (hereinafter referred to as “third portion”) is measured. Then, it is examined whether or not the difference between the luminances of the first to third portions in the organic EL element 400 is smaller than that in the case of the organic EL element 300.

Hereinafter, first, the organic EL element 300 and the organic EL element 400 will be described, and then the simulation result will be described.
<Organic EL element 300>
As shown in FIG. 3, the organic EL element 300 includes a first electrode 312 stacked on the substrate 311, a second electrode 316 provided above the substrate 311 and facing the first electrode 312, And a functional layer 315 disposed between the electrode 312 and the second electrode 316. The functional layer 315 includes a light emitting layer 313 and a second carrier injection layer 314. An axis 301 indicates a rotation center axis in the spin coating method. The surface 302 is a light emitting surface.

A table 500 in FIG. 5 shows optical parameters (column 511, column 512) and structure parameters (column 521) used for simulation for each layer in the organic EL element 300. A column 511 indicates a refractive index with respect to light having a wavelength of 550 nm of each layer or the like. A column 512 indicates an extinction coefficient with respect to light having a wavelength of 550 nm of each layer or the like. The optical parameter values are as follows. Aluminum is used for the first electrode 312, Green 1302 manufactured by Sumitomo Chemical is used for the light emitting layer 313, PEDOT: PSS is used for the second carrier injection layer 314, and the second electrode 316 is used for the second electrode 316. It is defined as using ITO. A column 521 indicates the film thickness of each layer or the like as a structural parameter. In a column corresponding to the “light emitting layer 313” in the column 521, “70 nm to 80 nm” is described. In the organic EL element 300, as shown in FIG. 3A, the light emitting layer 313 has the largest film thickness in the vicinity of the rotation center axis (for example, the axis 301) in the spin coating method, and is separated from the rotation center axis. This is because the film thickness changes continuously and the thinnest part is 70 nm. In the light emitting layer 313, the film thickness in the first portion 321 is the largest at 80 nm, the film thickness in the second portion 322 is 75 nm, and the film thickness in the third portion 323 is the smallest at 70 nm.
<Organic EL element 400>
As shown in FIG. 4, the organic EL element 400 includes a first electrode 412 stacked on the substrate 411, a second electrode 416 provided above the substrate 411 so as to face the first electrode 412, a first electrode And a functional layer 415 disposed between the electrode 412 and the second electrode 416. The functional layer 415 includes a light emitting layer 413 and a second carrier injection layer 414. An axis 401 indicates a rotation center axis in the spin coating method. The surface 402 is a light emitting surface.

A table 500 in FIG. 5 shows optical parameters (column 511, column 512) and structural parameters (column 522) used for simulation for each layer in the organic EL element 400. The parameters in the columns 511 and 512 are the same as those of the organic EL element 300 except for those related to the nanoparticles. Nanoparticles are defined when silica particles are used.
A column 522 indicates the film thickness of each layer or the like as a structural parameter, and the particle diameter of a nanoparticle. In this simulation, it is assumed that the nanoparticles occupy 25% of the volume of the light emitting layer. Here, the column corresponding to the “light emitting layer 413” in the column 522 describes 70 nm to 180 nm. This is due to the following reason. That is, in the organic EL element 400, the light emitting layer 413 has the largest thickness of 80 nm in the first portion 421 in the portion where the nanoparticles are not present between the first electrode 412 and the second electrode 416. It is assumed that the thickness decreases as the distance from the axis increases, and the thinnest part is 70 nm. And about the 1st part 421, as shown in FIG.3 (b), it is because the film thickness reaches a maximum of 180 nm about the part in which a nanoparticle exists.

Here, the thickness of the light emitting layer 413 in the first portion 421 continuously changes between 80 nm and 180 nm. As an example, the film thickness of the particle existence portion 442 is 180 nm, the film thickness of the particle non-existence portion 441 is 80 nm, and the vicinity 443 (443a, 443b) of the particle existence portion 442 has a film thickness of 80 nm or more and 180 nm or less. It changes continuously in the range. Further, the film thickness of the light emitting layer 413 in the second portion 422 also changes continuously between 75 nm and 175 nm as in the case of the first portion 421. Further, the film thickness of the light emitting layer 413 in the third portion 423 also continuously changes between 70 nm and 170 nm as in the case of the first portion 421.
<Simulation results>
(1) Luminance For each of the organic EL element 300 and the organic EL element 400, a luminance value was calculated by simulation using the optical parameters and the structural parameters described above. The simulation assumes that Green 1302 of the light emitting layer 313 has an electron transporting property and PEDOT: PSS of the second carrier injection layer 314 has a hole transporting property, so that light is emitted at the interface between the light emitting layer 313 and the hole injection layer 314. Going below.

The simulation result regarding the brightness | luminance about the organic EL element 300 is described as a luminance relative value in FIG. The luminance relative values in FIG. 3 are normalized with respect to the luminance values of the first portion 321 to the third portion 323 as viewed from the light emitting surface (the surface 302 of the second electrode 316) with reference to the luminance value of the first portion 321. It is the value.
As shown in FIG. 3, in the organic EL element 300, the relative luminance value of the first portion 321 is 1.0, the relative luminance value of the second portion 322 is 1.13, and the relative luminance of the third portion 323. The value is 1.23. In the organic EL element 300, the difference between the maximum luminance relative value (1.23) and the minimum luminance relative value (1.0) is 0.23.

Moreover, the simulation result regarding the brightness | luminance about the organic EL element 400 is described as a luminance relative value in FIG. The luminance relative values in FIG. 4 are the luminance values of the first part 421 to the third part 423 viewed from the light emitting surface (the surface 402 of the second electrode 426) side, and the luminance values of the first part 321 of the first model. Values normalized to the standard.
As shown in FIG. 4, in the organic EL element 400, the relative luminance value of the first portion 421 is 0.79, the relative luminance value of the second portion 422 is 0.87, and the relative luminance of the third portion 423 is. The value is 0.94. In the organic EL element 400, the difference between the maximum value of the relative luminance value (0.94) and the minimum value of the relative luminance value (0.76) is 0.15, which is different from the case of the organic EL element 300. Is getting smaller.

From the above, it can be said that the organic EL element 400 is slightly darker than the organic EL element 300, but the luminance unevenness is reduced.
That is, the organic EL element 400 in which the functional layer is formed so as to include the nanoparticles is different from the organic EL element 300 that does not include the nanoparticles in the functional layer even if the functional layer has a difference in film thickness due to the film formation method or the like. Compared with this, the degree of luminance unevenness that occurs can be reduced.

(2) Chromaticity X-coordinate and chromaticity-Y coordinate In addition to the above-described luminance simulation, the inventor also simulated the chromaticity X-coordinate and chromaticity Y-coordinate for each of the organic EL element 300 and the organic EL element 400. Went.
A table 600 in FIG. 6 shows the maximum value, the minimum value, and the difference between the luminance, the chromaticity X coordinate, and the chromaticity Y coordinate obtained by simulation.

A column 611 in the table 600 shows a simulation result for the organic EL element 300. A column 612 of the table 600 shows a simulation result for the second model of the organic EL element 400.
The description of the luminance in the table 600 is a summary of the simulation results described above.

Regarding the chromaticity X coordinate, the difference between the maximum value and the minimum value is 0.034 when there is no nanoparticle (organic EL element 300), whereas it is 0 when there is nanoparticle (organic EL element 400). The variation of the organic EL element 400 is smaller.
Regarding the chromaticity Y coordinate, the difference between the maximum value and the minimum value is 0.030 when there is no nanoparticle (organic EL element 300), whereas it is 0 when there is nanoparticle (organic EL element 400). .007, and the variation of the organic EL element 400 is smaller.

As described above, the organic EL element 400 in which the light emitting layer is formed so as to include nanoparticles has less variation in chromaticity X coordinate and chromaticity Y coordinate than the organic EL element 300 in which the light emitting layer does not include nanoparticles. It can be said that.
As described above, by containing the nanoparticles in the functional layer, the difference between the maximum value and the minimum value of the luminance, chromaticity X coordinate, and chromaticity Y coordinate becomes smaller than the case where no nanoparticles are contained, There is an effect that variation is improved.
<Summary>
The organic EL element 1 is configured by dispersing nanoparticles 20 in the functional layer 15 (more specifically, the light emitting layer 13). Since it is configured in this manner, the film thickness of the particle-existing portion of the functional layer 15 is equal to or greater than the particle-non-existing portion (80 nm as an example). ) Added to the film thickness (as an example, 180 nm) or less. In the functional layer 15, such a local change in film thickness occurs as many as the number of particle existing portions throughout the functional layer 15.

  That is, the film thickness of the functional layer 15 is naturally varied by using the nanoparticles 20. For this reason, regardless of the presence or absence of the unevenness of the film thickness due to the film forming method or the like, the functional layer 15 emits light in which the emission spectrum corresponding to each continuously changing film thickness is synthesized. Therefore, in the organic EL element 1, even if a deviation in film thickness due to a manufacturing method or the like occurs, the composition ratio of the originally varying film thickness only shifts as a whole corresponding to the deviation in film thickness. There is little change in the composition ratio of the emission spectrum. Therefore, in the organic EL element 1, even if a difference in film thickness due to a film forming method or the like occurs, the degree of uneven brightness can be reduced.

  In the organic EL element 1, the light emitting layer 13 is formed by forming the light emitting portion 21 on the nanoparticles 20. For this reason, in order to provide irregularities on the layer immediately below the light emitting layer 13 (for example, the first electrode 12), a photosensitive resin is once formed on the layer immediately below, and sputtering is performed to form an irregular pattern. Such a procedure is not necessary. That is, the organic EL element 1 can be manufactured by a simpler method than the organic EL element that requires the procedure for providing the above-described unevenness.

Nanoparticles can also be easily placed on curved surfaces. Therefore, when the lower layer of the functional layer forms a curved surface, the functional layer (15) is formed on the curved surface more easily than when the photosensitive resin is formed and sputtered as described above. can do.
<1-4. Manufacturing method of organic EL element 1>
The manufacturing method of the organic EL element 1 is demonstrated using FIG. 7 (a)-(d) and FIG. 8 (a)-(c).

First, the first electrode 12 is formed on one surface of the substrate 11 based on a thin film process such as a vacuum deposition method or a wet process such as a coating method (FIGS. 7A and 7B).
Next, a solvent mixed with nanoparticles 20 is applied on the first electrode 12 (FIG. 7C).
Next, the solvent is dried so that the nanoparticles 20 remain on the first electrode 12 (FIG. 7D). Here, the nanoparticles 20 are fixed on the first electrode 12 by intermolecular force or electrostatic force. Therefore, even when the substrate 11 is rotated for film formation of the light-emitting portion 21 by the spin coating method, the nanoparticles 20 can be kept in a state of being fixed on the first electrode 12. Next, on the first electrode 12 to which the nanoparticles 20 are fixed, ink is applied and the solvent is dried by spin coating to form the light emitting portion 21 of the light emitting layer 13 (FIG. 8A). Thereby, the light emitting layer 13 is completed.

Next, the second carrier injection layer 14 is formed on the light emitting layer 13 by a wet process such as a coating method (FIG. 8B). Then, ink is applied on the functional layer 15 and the solvent is dried to form the second electrode 16 (FIG. 8C). The organic EL element 1 can be manufactured by the above process.

<2. Modification 1>
The organic EL element according to the embodiment has been described above, but the exemplified organic EL element can be modified as follows, and the present invention is of course not limited to the example shown in the above-described embodiment. It is.
(1) In the above-described embodiment, the functional layer 15 is composed of the light emitting layer 13 and the second carrier injection layer 14. However, the functional layer 15 only needs to include at least the light emitting layer 13. The functional layer 15 may have a single layer structure or a multilayer structure, and layers other than the light emitting layer 13 may be provided as necessary. For example, as illustrated in FIG. 9, the functional layer 15 includes, in order from the first electrode 12 side, a first carrier injection layer 901, a first carrier transport layer 902, a light emitting layer 13, an interlayer 903, and a second carrier transport layer 904. The second carrier injection layer 14 may be laminated.
(2) In the above-described embodiment, silica particles having a refractive index lower than that of the light emitting unit 21 are used as the nanoparticles 20, but it is desirable to use a material having a higher refractive index. For example, zirconia may be used as the nanoparticles 20. Silica has a refractive index of 1.45 and zirconia has a refractive index of 2.1. Therefore, when zirconia particles are used to obtain the same effect as silica particles, the particle diameter can be 0.69 (= 1.45 / 2.1) times that when silica particles are used. Therefore, when zirconia is used as the nanoparticles, the thickness of the light emitting layer can be made thinner than when silica particles are used.

Further, when the nanoparticles are excessively aggregated in the light emitting layer, the aggregated portion can cause dark spots. Since the aggregate becomes smaller as the particle size of the nanoparticles is smaller, the risk of dark spot generation can be reduced by using zirconia particles as the nanoparticles than when silica particles are used.
(3) In the above-described embodiment, when forming the light emitting layer (13), the nanoparticles 20 are previously fixed on the first electrode 12 which is an example of the lower layer of the light emitting layer 13, and then light is emitted by spin coating. It has been described that the portion 21 is formed. However, the method for forming the light emitting layer is not limited to this, and it is sufficient if a light emitting layer containing nanoparticles can be formed. For example, the light emitting layer (1102) may be formed by a method shown in FIGS. 10 to 11 using a mixed material in which the nanoparticles 20 are mixed with the organic material that is the material of the light emitting unit 21.

10 and 11, FIGS. 10C and 11A show a method for forming the light emitting layer 1102. 10 (a) and 10 (b) are the same as those described in FIGS. 7 (a) and 7 (b), and FIGS. 11 (b) and 11 (c) are shown in FIGS. 8 (b) and 8 (c). Since these are the same as those described, description thereof will be omitted.
In this modification, the light emitting layer 1102 is formed in two steps. As a first procedure, as shown in FIG. 10C, the above-mentioned mixed material is dropped by a spin coating method, and the film thickness (80 nm as an example) or less as the film thickness of the non-existing region (as an example) As an example, a 20 nm thick film 1001 is formed. At this time, the lower 20 nm portion of the nanoparticle 20 is buried in the film 1001, and the upper 80 nm portion is exposed.

  Next, as a second procedure, an organic material not mixed with the nanoparticles 20 is dropped by a spin coating method so that the film thickness of the non-existing portion of the light emitting layer 1102 becomes the target film thickness. As a result, as shown in FIG. 11A, the film 1101 is laminated on the film 1001, and the film thickness of the part where particles are not present is increased by 60 nm from the state shown in FIG. (80 nm as an example). In addition, in the particle existing portion of the light emitting layer 1102, a film having a maximum thickness of 60 nm is laminated on the nanoparticle 20 having a particle diameter of 100 nm, and the maximum film thickness is 160 nm.

Regarding the third model obtained by modeling the organic EL element 1200 (see FIG. 12) generated as described above, the inventor performed a simulation similar to the case of the first model and the second model.
As shown in FIG. 12, the organic EL element 1200 includes a first electrode 1212 stacked on a substrate 1211, a second electrode 1216 provided above the substrate 1211 and facing the first electrode 1212, and a first electrode A functional layer 1215 disposed between the electrode 1212 and the second electrode 1216. The functional layer 1215 includes a light emitting layer 1213 and a second carrier injection layer 1214. An axis 1201 indicates the rotation center axis in the spin coating method. The surface 1202 is a light emitting surface.

In FIG. 12, the simulation result regarding the brightness | luminance performed about the organic EL element 1200 is described as a luminance relative value similarly to FIG.
As shown in FIG. 12, in the organic EL element 1200, the relative luminance value of the first portion 1221 is 0.76, and the relative luminance value of the third portion 1222 is 0.95. In the organic EL element 1200, the difference between the maximum value of the relative luminance value (0.95) and the minimum value of the relative luminance value (0.76) is 0.19, which is different from the case of the organic EL element 300. Is getting smaller.

  The inventor also performed a simulation on the chromaticity X coordinate and chromaticity Y coordinate regarding the organic EL 1200. The result is shown in the table 600 of FIG. Column 613 of table 600 shows the simulation results for the third model. The description of luminance in column 613 of table 600 is a table summarizing the simulation results described above.

  Regarding the chromaticity X coordinate, the difference between the maximum value and the minimum value is 0.034 when there is no nanoparticle (organic EL element 300), whereas it is 0 when there is nanoparticle (organic EL element 1200). .016, and the variation of the organic EL element 1200 is smaller. Regarding the chromaticity Y coordinate, the difference between the maximum value and the minimum value is 0.030 when there is no nanoparticle (organic EL element 300), whereas it is 0 when there is nanoparticle (organic EL element 1200). .030, which is the same as the first model.

As described above, the organic EL element in which the light emitting layer is formed so as to include nanoparticles does not improve the chromaticity Y coordinate as compared with the organic EL element in which the light emitting layer does not include nanoparticles, but the chromaticity X coordinate. The variation is small.
As described above, the organic EL element manufactured by the manufacturing method shown in the present modification also has a difference between the maximum value and the minimum value of the luminance and chromaticity X-coordinate by including the nanoparticles in the functional layer. Compared with the case where no is contained, all become small, and there exists an effect that dispersion | variation is improved.
(4) In the above-described embodiment, the organic EL element 1 is a top emission type light emitting element in which the first electrode 12 is a reflective electrode and the second electrode 16 is a transparent electrode, but is not limited thereto. For example, the organic EL element 1 may be a bottom emission type light emitting element in which the first electrode 12 is realized by a transparent electrode and the second electrode 16 is realized by a reflective electrode.
(5) In the above-described embodiment, it has been described that the deviation in film thickness is caused by the film forming method or the like. However, the deviation in film thickness was caused by other factors such as a change in film forming conditions. However, it goes without saying that the degree of luminance unevenness can be reduced by using the present invention.
(6) You may combine the above-mentioned embodiment and each modification partially.

  The organic EL element of the present invention can be used to produce a flexible element whose film thickness distribution changes when bent, a light-emitting element having a complicated three-dimensional shape, a lighting device used indoors or outdoors, and a public It is suitable for digital signage and advertising towers used in facilities.

DESCRIPTION OF SYMBOLS 1 Organic EL element 11 Substrate 12 1st electrode 13 Light emitting layer 14 Carrier injection layer 15 Functional layer 16 2nd electrode 20 Nanoparticle 21 Light emission part 200 Spin coater 201 Spinner 202 Wafer 203 Cup 204 Nozzle part 300 Organic EL element 301 Axis 302 Surface 310 Light emitting layer 311 Substrate 312 First electrode 313 Light emitting layer 314 Second carrier injection layer 315 Functional layer 316 Second electrode 400 Organic EL element 401 Axis 402 Surface 411 Substrate 412 First electrode 413 Light emitting layer 414 Second carrier injection layer 415 Functional layer 416 Second electrode

Claims (6)

An organic EL element in which a first electrode layer having light reflectivity, a functional layer including at least a light emitting layer, and a second electrode layer having light transmissivity are laminated in this order,
The functional layer includes a plurality of nanoparticles, and the film thickness of the functional layer is larger in the thickness of the portion where the nanoparticles are present than in the portion where the nanoparticles are not present. The organic EL device according to claim 1, wherein the plurality of nanoparticles are included in the light emitting layer. The organic EL element according to claim 2, wherein a refractive index of the plurality of nanoparticles is larger than a refractive index of an organic material constituting a portion other than the plurality of nanoparticles in the light emitting layer. The organic EL device according to claim 3, wherein the nanoparticles are mesoporous silica particles. The film thickness in the vicinity of the part where the nanoparticles are present is equal to or greater than the first film thickness of the part where the nanoparticles other than the vicinity do not exist, depending on the position in the vicinity. The organic EL element according to claim 1, which continuously changes within a range equal to or less than the sum of the diameter. The organic EL element according to claim 1, wherein the average particle diameter of the nanoparticles is 10 nm or more and 200 nm or less.

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