JP2013089501A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element which can improve light extraction efficiency and also can emit natural light difficult to get shorted and low in wavelength dependency and directivity.SOLUTION: An organic EL element 1 comprises a substrate 2, a plurality of organic layers 4 including a luminescent layer 43, and an anode layer 3 and a cathode layer 5 formed across the organic layers 4. The anode layer 3 has a plurality of concavities 3a on its face adjoining the organic layers 4, the concavities 3a being formed such that their opening diameters, as measured by distance parallel to the substrate 2, become larger as they are closer to the organic layers 4, and that the distances between center parts P of the concavities 3a are not uniform. According to this composition, the concavities 3a adjacent to the organic layers 4 of the anode layer 3 help to improve the efficiency of light extraction, and the opening diameters of the concavities 3a which are larger on the organic layers 4 side than on the other side and moderate undulations of the concavities 3a make electrical shorting difficult to occur. Furthermore, since the concavities 3a are not periodically ragged structures and are not uniformly disposed, the outgoing beam of light has its waveform dependency and directivity reduced, making it possible to emit natural light.

Description

  The present invention relates to an organic electroluminescence device having a light extraction layer.

  An electroluminescence (EL) element is formed by forming a light emitting layer sandwiched between an anode and a cathode on a transparent substrate. When a voltage is applied between the electrodes, electrons and holes injected as carriers in the light emitting layer are formed. Light is emitted by excitons generated by recombination. EL elements are roughly classified into an organic EL element using an organic substance as a fluorescent material of a light emitting layer and an inorganic EL element using an inorganic substance. In particular, the organic EL element can emit light with high luminance at a low voltage, and various emission colors can be obtained depending on the type of fluorescent material. In addition, various types of organic EL elements can be easily manufactured as a flat light-emitting panel. Used as a display device or a backlight. Further, in recent years, a device corresponding to high luminance has been realized and attention has been paid to using it for an illumination device or the like.

  FIG. 5 shows a cross-sectional configuration of a general organic EL element. In the organic EL element 101, a light-transmitting electrode layer 103 is provided on a light-transmitting substrate 102, and a hole injection layer 141, a hole transport layer 142, and a light emitting layer 143 are formed on the electrode layer 103. An organic layer 104 is provided. Further, an electrode layer 105 having light reflectivity is provided over the organic layer 104. When a voltage is applied between the electrode layers 103 and 105, light emitted from the light emitting layer 143 is converted into a plurality of layers made of different materials such as the hole transport layer 142, the hole injection layer 141, the electrode layer 103, and the substrate 102. And is taken out of the device.

  When light propagates from a certain medium to a medium having a different refractive index, reflection and transmission corresponding to each refractive index occur at the interface of the medium. Further, Fresnel's law indicates that reflection is more likely to occur as the refractive index difference of each medium increases. In addition, when light propagates from a medium with a high refractive index to a medium with a low refractive index, the critical angle is determined from Snell's law by the refractive index between the medium at the interface, and light above the critical angle is transmitted at the interface. Totally reflected, confined in a medium having a high refractive index, and lost as guided light. Here, glass is widely used for the substrate 102 used in the general organic EL element 101 from the viewpoint of transparency, strength, low cost, gas barrier properties, chemical resistance, heat resistance, etc. A typical soda lime glass has a refractive index of about 1.52. On the other hand, indium tin oxide (ITO) or indium zinc oxide (IZO) in which indium oxide is doped with tin oxide is widely used for the electrode layer 103 because of its excellent transparency and electrical conductivity. The refractive index of ITO or IZO varies depending on the composition, film forming method, crystal structure, etc., but the refractive index of ITO is about 1.7 to 2.3, and the refractive index of IZO is 1.9 to 2.4. Both have a higher refractive index than the substrate 102.

  In addition, the refractive index of each material such as a light emitting material constituting the light emitting layer 143, the hole injection layer 141, the hole transport layer 142 and the like used for the organic layer 104 is often about 1.6 to 2.0. That is, in the general organic EL element 101, the magnitude relationship of the refractive index of each layer is air <substrate <organic layer <electrode layer (anode). Therefore, of the light emitted from the light emitting source of the light emitting layer 143, light incident at a large incident angle on the interface between the substrate 102 and the outside of the element (atmosphere) and the interface between the electrode layer 103 and the substrate 102 is reflected at those interfaces. Since it is totally reflected, it may not be extracted outside the device as effective light.

  Therefore, in order to alleviate total reflection at the interface between media having different refractive indexes, an organic EL element in which fine irregularities (corrugated structure) are formed on this interface is known (for example, see Patent Document 1). . In this organic EL element, a curable resin layer having a periodic concavo-convex structure is formed on a substrate, an electrode layer or an organic layer is laminated on the curable resin layer having the concavo-convex structure, and a corrugated structure is formed on each layer. Is provided.

JP 2009-9861 A

  However, as in the organic EL element described in Patent Document 1, when the electrode layer or the organic layer is provided with a concavo-convex structure having a large undulation, for example, a convex portion of a certain layer and a concave portion of this upper layer are close to each other. As a result, the film thickness of each layer becomes non-uniform, so that a short circuit is likely to occur. In addition, when a periodic concavo-convex structure is provided in the vicinity of the light emitting layer, the light interferes, and the wavelength dependency of the light extracted outside the device becomes strong, and the directivity of the light is easily generated. Such an organic EL element having high wavelength dependency and directivity is not suitable for a device such as a lighting device that emits natural light over a wide range.

  The present invention solves the above problems, and provides an organic EL device that can emit natural light that is less likely to cause a short circuit and has low wavelength dependency and directivity while improving light extraction efficiency. The purpose is to do.

  In order to solve the above problems, an organic EL device according to the present invention includes a substrate, a plurality of organic layers including a light emitting layer provided on the substrate, and a pair of electrode layers sandwiching the organic layer. In the organic EL element, at least one of the electrode layers has a plurality of recesses on a surface in contact with the organic layer, and when the distance of the recesses parallel to the substrate is an opening diameter, the opening diameter Increases as it approaches the organic layer, and when the center of the concave portion is a central portion, the distance between the central portions of the plurality of concave portions is not uniform.

  In the organic EL element, an organic layer in contact with the electrode layer having the concave portion among the plurality of organic layers corresponds to each of the concave portions of the electrode layer on a surface opposite to the electrode layer side of the organic layer. It is preferable to have a concave portion.

  In the organic EL element, the light emitting layer in the organic layer preferably has a concave portion corresponding to each of the concave portions of the electrode layer on the surface of the light emitting layer opposite to the electrode layer side.

  In the organic EL element, it is preferable that an opening diameter of a concave portion of the electrode layer on a surface contacting the organic layer is 2 nm to 1 μm.

  In the organic EL element, it is preferable that the maximum film thickness of the electrode layer having the recess is 1 nm to 500 nm.

  According to the present invention, while the light extraction efficiency is improved by the concave portion in contact with the organic layer of the electrode layer, the opening diameter of the concave portion increases as it approaches the organic layer, and the undulation of the concave portion is gentle, so that a short circuit hardly occurs. In addition, since it is not a periodic concavo-convex structure and the arrangement of the concave portions is not uniform, the wavelength dependency and directivity of outgoing light are reduced, and natural light can be emitted.

1 is a side sectional view of an organic EL element according to an embodiment of the present invention. (A) is AA sectional drawing of FIG. 1, (b) is BB sectional drawing. The sectional side view of the organic EL element which concerns on the modification of the said embodiment. (A) is a sectional side view of the substrate and electrode layer of the organic EL element according to Example 1, (b) is a sectional side view of the substrate and electrode layer of the organic EL element according to Example 2, and (c) is a comparative example. 2 is a side cross-sectional view of a substrate and an electrode layer of an organic EL element according to FIG. 1, and FIG. The sectional side view of the conventional organic electroluminescent element.

  An organic electroluminescence element (hereinafter referred to as an organic EL element) according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the organic EL element 1 of the present embodiment includes a substrate 2, a plurality of organic layers 4 including a light emitting layer provided on the substrate 2, and a pair of electrode layers sandwiching the organic layer 4. (Anode layer 3 and cathode layer 5). The organic layer 4 has a hole injection layer 41, a hole transport layer 42, and a light emitting layer 43, which are laminated in this order from the anode layer 3 side. In this configuration, when a voltage is applied between the anode layer 3 and the cathode layer 5, the light emitted from the light emitting layer 43 is emitted from the hole transport layer 42, the hole injection layer 41, the anode layer 3, and the substrate. 2 is extracted out of the device.

In the organic EL element 1, at least one of the electrode layers, in this example, the anode layer 3 has a plurality of recesses 3 a on the surface in contact with the organic layer 4. As shown in FIGS. 2 (a) and 2 (b), the recess 3 a increases as the opening diameter approaches the organic layer 4 when the distance parallel to the substrate 2 is the opening diameter. In this example, the concave portion 3a has a substantially hemispherical shape, and the opening diameter of the regular circle increases from the BB cross section shown in FIG. 1 toward the AA cross section. Further, when the center of the concave portion 3a is the central portion P, the distance D between the central portions P of the plurality of concave portions 3a is not uniform. That is, the substantially hemispherical concave portions 3 a are formed so as to be unevenly dispersed in the anode layer 3. Furthermore, the opening peripheral edge of the concave portion 3a in the A-A cross section, may be comprised of a single circular a _1, for example, consisted of a shape a _2, a ₃ a plurality of circular led May be.

  Further, as shown in FIG. 1, among the plurality of organic layers 4, the organic layer 4 in contact with the anode layer 3 having the recess 3 a, in this example, the hole injection layer 41 is the surface opposite to the anode layer 3. In addition, a recess 41 a corresponding to each of the recesses 3 a of the anode layer 3 is provided. Furthermore, like the hole injection layer 41, the hole transport layer 42 and the light emitting layer 43 formed on the hole injection layer 41 also have recesses 42a and 43a, respectively. That is, not only the anode layer 3 but also the light emitting layer 43 has a recess 43a on the surface opposite to the anode layer 3 side of the light emitting layer 43. In addition, although the same recessed part is provided also in the surface on the opposite side to the organic layer 4 of the cathode layer 5, this does not act directly on the improvement of light extraction efficiency.

  The substrate 2 is a flat rectangular plate material having translucency. For example, a rigid glass plate such as soda glass or non-alkali glass or a flexible plastic plate such as polycarbonate or polyethylene terephthalate is used.

  The anode layer 3 having the recess 3a is formed by, for example, the following manufacturing method. In this production method, first, a nanoparticle dispersion liquid in which nanoparticles are monodispersed in a liquid is prepared (first step). Next, a nanoparticle dispersion is applied to the surface of the substrate 2, and the nanoparticles are monodispersed and adhered to the surface of the substrate 2 (second step). Subsequently, a conductive material is formed on the surface of the substrate 2 from above the nanoparticles adhered in a monodispersed state (third step). Then, the nanoparticles are removed from the surface of the substrate 2 (fourth step).

  In the first step, silica nanoparticles having high transparency, controllable particle diameter, and low cost are preferably used as the nanoparticles. The solution in which the nanoparticles are dispersed includes water, alcohols such as methanol, ethanol, propanol or butanol, ethers such as diethyl ether, dibutyl ether, tetrahydrofuran or dioxane, and aliphatic carbonization such as hexane, heptane or octane. Hydrogen, aromatic hydrocarbons such as benzene, toluene or xylene, esters such as ethyl acetate or butyl acetate, ketones such as methyl ethyl ketone or methyl isobutyl ketone, and halogenated carbons such as methylene chloride or chloroform are used. A nanoparticle dispersion in which nanoparticles are dispersed in any of the solutions described above becomes a colloidal solution. Next, the block copolymer is added to this colloidal solution and stirred to dissolve uniformly. As the block copolymer, for example, a triblock copolymer obtained by copolymerizing a hydrophilic polyethylene oxide block on both sides of a hydrophobic polypropylene oxide block is suitably used. Subsequently, the pH of the colloidal solution is adjusted using an acid such as hydrochloric acid. By adjusting the pH, the dispersibility of the nanoparticles in the colloidal solution can be controlled. Thereby, a nanoparticle dispersion liquid is adjusted.

  In the second step, the nanoparticle dispersion liquid prepared in the first step is applied to the surface of the substrate 2. Application methods include, for example, brush coating, spray coating, dipping (dipping, dip coating), roll coating, flow coating, curtain coating, knife coating, spin coating, table coating, sheet coating, single wafer coating, die coating, bar Various general coating methods such as coating are appropriately used. At this stage, the coating film may be patterned into an arbitrary shape using a method such as cutting or etching. Further, when attaching the nanoparticles to the surface of the substrate 2, it is preferable that they are removed so that other components such as organic components in the colloidal solution other than the nanoparticles do not exist on the surface of the substrate 2. . As a method for removing other components, for example, a method in which the substrate 2 on which the coating film is formed is immersed in a solution in which nanoparticles are not dissolved but other components can be dissolved, heat treatment, ultraviolet treatment, etc. Thus, there may be mentioned a method in which other components are decomposed and removed while the nanoparticles remain on the substrate 2. This method is appropriately selected in consideration of the durability of the substrate 2 and the like.

  In the third step, a conductive material is formed on the surface of the substrate 2 to which the nanoparticles are attached. Although it does not specifically limit as a conductive material, It is preferable to use what has high electrical conductivity, such as metals, such as aluminum, gold | metal | money, silver, or copper, and conductive carbon, such as a carbon nanotube. As a method for coating the conductive material, an arbitrary method such as a wet process by a reduction reaction such as plating or a dry process such as sputtering or vapor deposition can be employed. Although the production | generation method of the electroconductive material by a reductive reaction is not specifically limited, For example, addition of a reducing agent, electrolytic plating, electroless plating, etc. are mentioned. When the conductive material is coated in this manner, the conductive material can be attached to the exposed surface of the substrate 2 other than the part to which the nanoparticles are attached, using the nanoparticles as a mask.

  In the fourth step, the nanoparticles are removed from the surface of the substrate 2. Examples of the method for removing the nanoparticles include a method for eluting the nanoparticles and a method for physically removing the nanoparticles. Silica nanoparticles are thermally and mechanically strong and resistant to chemicals such as organic solvents, while some chemicals such as acids such as hydrofluoric acid and alkalis such as aqueous sodium hydroxide are used. It is easy to dissolve. As described above, as a method for eluting the nanoparticles, the conductive material and the substrate 2 are difficult to dissolve by utilizing the properties of the selected nanoparticles. For example, an aqueous sodium hydroxide solution in which the silica nanoparticles are dissolved can be used. It is carried out by treatment with an alkaline solution or an acid solution such as hydrofluoric acid. Moreover, as a method of physically removing the nanoparticles, a method of ultrasonically treating the substrate 2 in a liquid can be mentioned. Moreover, you may use combining the method of eluting and the method of removing physically. In this way, the anode layer 3 in which the recess 3a is formed is produced.

  As a manufacturing method different from the manufacturing method described above, for example, the anode layer 3 having the recesses 3a may be manufactured using a nanoimprint technique. Specifically, a translucent material containing a conductive material is formed by spin coating, screen printing, dip coating, die coating, cast coating, spray coating, gravure coating, etc., and then corresponds to a plurality of recesses 3a. The anode layer 3 having the recesses 3a can be obtained by nanoimprinting using a nano stamper having a plurality of protrusions formed thereon. Examples of the conductive material include fine particles of metal such as silver or gold, fine particles of metal oxide such as indium-tin oxide (ITO), indium-zinc oxide (IZO) or tin oxide, and conductive organic materials. (Including a polymer), a dopant (donor or acceptor) -containing organic layer, a mixture of a conductor and a conductive organic material (including a polymer), and the like. Examples of the translucent material include acrylic resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, and diacryl. Examples thereof include phthalate resins, cellulose resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and copolymers of two or more monomers constituting these resins.

  A hole injection layer 41, a hole transport layer 42, and a light emitting layer 43 are stacked on the anode layer 3 thus manufactured. When each of these layers is formed by, for example, vacuum deposition, the deposited film is formed with a constant film thickness with respect to the deposition surface (the anode layer 3 in this example). Recesses 41a, 42a, 43a corresponding to the respective recesses 3a are formed.

  Examples of the material constituting the hole injection layer 41 include organic materials including thiophene, triphenylmethane, hydrazoline, arylamine, hydrazone, stilbene, triphenylamine, and the like. Specifically, polyvinyl carbazole (PVCz), polyethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS), aromatic amine derivatives such as TPD, etc., the above materials may be used alone, or two or more materials May be used in combination.

  The hole transport layer 42 is appropriately selected from the group of compounds having hole transport properties. Examples of this type of compound include 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), N, N′-bis (3-methylphenyl)-(1 , 1′-biphenyl) -4,4′-diamine (TPD), 2-TNATA, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA) , 4,4′-N, N′-dicarbazole biphenyl (CBP), spiro-NPD, spiro-TPD, spiro-TAD, TNB, and the like, triarylamine compounds, amine compounds containing carbazole groups, fluorene Examples thereof include amine compounds containing derivatives, etc. It is not limited to those described above, and any generally known hole transporting material can be used.

Examples of the material constituting the light emitting layer 43 include 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 (Alq ₃ ), tris (4-methyl-8-quinolinato) aluminum complex, Tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, pyran, quinacrid , Rubrene, and derivatives thereof, or a group consisting of 1-aryl-2,5-di (2-thienyl) pyrrole derivative, distyrylbenzene derivative, styrylarylene derivative, styrylamine derivative, and luminescent compounds thereof. Examples thereof include a compound or polymer having a part of the molecule. In addition to compounds derived from fluorescent dyes typified by the above-mentioned compounds, so-called phosphorescent materials, for example, luminescent materials such as Ir complexes, Os complexes, Pt complexes, and europium complexes, or compounds having these in the molecule or high Molecules can be suitably used. These materials are appropriately selected and used as necessary. The light emitting layer 43 made of the above-described material may be formed by a vacuum process, a dry process such as transfer, or a wet process such as spin coating, spray coating, die coating, or gravure printing. May be. In addition to the light emitting layer 43, an electron transport layer and an electron injection layer may be provided in a timely manner.

As the material constituting the cathode layer 5, aluminum (Al) is preferably used, and a layered structure may be formed by combining Al and another electrode material. Such electrode material combinations include alkali metal and Al laminates, alkali metal and silver laminates, alkali metal halides and Al laminates, and alkali metal oxides and Al laminates. Body, alkaline earth metal or laminate of rare earth metal and Al, alloys of these metal species with other metals, and the like. Specifically, a laminate of Al, sodium, sodium-potassium alloy, lithium, magnesium, etc., magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, LiF / Al mixture / laminate, Al / Al ₂ Examples include O ₃ mixtures.

  According to the organic EL element 1 configured as described above, since the concave portion 3a is provided in the anode layer 3, the light emitted from the light emitting layer 43 can be easily transmitted to the substrate 2 through the concave portion 3a. The extraction efficiency can be improved. In addition, the anode layer 3 has high translucency because the portion where the recess 3a is formed is thinned, and the anode layer 3 is continuously formed without interruption, so that high conductivity is obtained. Have. Furthermore, since the opening diameter of the recess 3a increases as it approaches the organic layer 4, the undulation of the recess 3a becomes gentler than in the configuration in which the opening diameter decreases toward the organic layer 4, and the organic layer 4 Is made uniform within a predetermined range. As a result, the distance between the electrode layers (the anode layer 3 and the cathode layer 5) is kept constant, and it is possible to prevent a short circuit from occurring. In addition, since the distance between the central portions P of the plurality of recesses 3a is not uniform, that is, the arrangement of the recesses 3a is not uniform and dispersed, instead of the periodic uneven structure, the wavelength dependence and directivity of the emitted light Therefore, natural light can be emitted.

  Further, since the recesses 41a, 42a and 43a are provided not only in the anode layer 3 but also in each layer of the organic layer 4, it is easy to transmit light at the interface where each layer is in contact, and the light extraction efficiency is further improved. Can do.

  The opening diameter of the concave portion 3a of the anode layer 3 on the surface in contact with the organic layer 4 is preferably 2 nm to 1 μm. In this way, the light emitted from the light emitting layer 43 can easily pass through the interface between the hole injection layer 41 and the anode layer 3, and the light extraction efficiency can be improved.

  Moreover, it is preferable that the maximum film thickness of the anode layer 3 which has the recessed part 3a is 1 nm-500 nm. In this way, the anode layer 3 can achieve both required translucency and conductivity. Here, the maximum film thickness of the anode layer 3 is determined according to the depth of the recess 3a. When the recess 3a has a substantially hemispherical shape as in this example, the maximum film thickness of the anode layer 3 is determined to be slightly larger than the radius of the recess 3a (half the opening diameter of the recess 3a). By so doing, the anode layer 3 has a reduced thickness at the portion where the recess 3a is formed, so that the translucency is enhanced. Therefore, the material constituting the anode layer 3 is not limited to a commonly used transparent material such as ITO, and for example, a highly conductive metal material such as aluminum or silver can be used. In addition, the thickness of the anode layer 3 where the recesses 3a are formed is preferably 30 nm or less in consideration of light transmission. However, since conductivity, transmittance, and the like vary depending on the material used for the anode layer 3, the film thickness is appropriately adjusted according to the required performance.

  A modification of the above embodiment will be described with reference to FIG. In the organic EL element 1 according to this modification, the depths of the recesses 3 a, 41 a, 42 a, 43 a formed in the respective layers are reduced as the distance from the anode layer 3 increases. According to this modification, since the undulations of the concave portions 41a, 42a, 43a of the organic layer 4 are gentle, the film thickness of each of these layers becomes uniform, and a short circuit can be prevented more easily. This configuration is suitable when the organic layer 4 is formed by coating, for example, without vapor deposition. Furthermore, in this modification, the surface of the cathode layer 5 opposite to the organic layer 4 is generally smooth, so that it is easy to attach a sealing cap provided so as to cover the cathode layer 5.

  Next, an example of the above-described embodiment will be specifically described with reference to FIGS. 4A to 4D and compared with a comparative example. 4A to 4D, only the substrate 2 and the anode layer 3 are shown.

Example 1
As the substrate 2, an alkali-free glass plate (Corning “No. 1737” having a refractive index of 1.50 to 1.53 with respect to light having a wavelength of 500 nm) was used. Next, the anode layer 3 having the recesses 3a was produced by the following procedure. First, lysine (L-lysine) was dissolved in water as a basic amino acid to prepare a basic amino acid aqueous solution. Next, tetraethoxysilane (TEOS) was added to the basic amino acid aqueous solution, and the mixture was stirred in a water bath at 60 ° C. at a rotation speed of 500 rpm for 24 hours to prepare a colloidal solution of silica. The raw material molar ratio in this colloidal solution was 1 (TEOS): 154.4 (H ₂ O): 0.02 (L-lysine). In the colloidal solution thus obtained, silica nanoparticles having a particle size of about 15 nm were produced. Subsequently, block copolymer F127 (the following formula (1)) was added to the colloid solution, and the mixture was stirred at 60 ° C. for 24 hours to completely dissolve F127 in the colloid solution.

上記（１）式において、「ＥＯ」はエチレンオキサイドブロック、「ＰＯ」はプロピレンオキサイドブロックを意味し、その下の数字は繰り返し単位数、「ＭＷ」は重量平均分子量、「ＨＬＢ」はＨｙｄｒｏｐｈｉｌｅ−Ｌｉｐｏｐｈｉｌｅ Ｂａｌａｎｃｅ、「ＣＭＣ」は臨界ミセル濃度を意味する。

In the above formula (1), “EO” means an ethylene oxide block, “PO” means a propylene oxide block, the number below it is the number of repeating units, “MW” is a weight average molecular weight, and “HLB” is Hydrophile-Lipophile. Balance, “CMC” means critical micelle concentration.

  The amount of F127 added was set to 1: 1 based on the mass of silica in the colloidal solution. Next, the pH of the colloidal solution was adjusted to 8 using hydrochloric acid, and aged by standing at 60 ° C. for 3 days. And the nanoparticle dispersion liquid was adjusted by diluting this solution 4 times with water (1st process).

  Next, the nanoparticle dispersion was applied to the substrate 2 by dip coating, and the nanoparticles were adhered onto the substrate 2. Subsequently, after the water was evaporated, in order to remove the organic component (lysine, F127) of the nanoparticle dispersion, UV ozone treatment was performed under the conditions of an ultraviolet wavelength of 172 nm, a pressure of 50 Pa, and an irradiation time of 30 min (second Process).

Next, on the surface of the substrate 2 on which silica nanoparticles are dispersed, Al is used as a conductive material by vacuum deposition under a vacuum of 2 × 10 ⁻⁴ Pa or less, and an Al film is formed with a thickness of about 7.5 nm. (Third step). After forming Al, this substrate 2 with Al was subjected to ultrasonic treatment in an aqueous ammonium fluoride solution for 30 minutes to remove silica nanoparticles and obtain an anode layer 3 having a recess 3a (fourth step) ). In this way, an anode layer 3 having a recess 3a on the substrate 2 as shown in FIG.

  Then, on this anode layer 3, polyethylene dioxythiophene / polystyrene sulfonic acid (PEDOT-PSS) (“CLEVIOS PAI4083” manufactured by HC Starck, PEDOT: PSS = 1: 6) has a thickness of 30 nm. Thus, the hole injection layer 41 was obtained by applying with a spin coater and baking at 150 ° C. for 10 minutes. The refractive index at a wavelength of 650 nm of the hole injection layer 41 was 1.55 as measured with a FilTek manufactured by SCI.

  Next, TFB (Poly [(9,9-dioc tylfluorenyl-2,7-diyl) -co- (4,4 ′-(N- (4-sec-butylphenyl)) diphenylamine)]) (American Dye Source) "Hole Transport Polymer ADS259BE") in THF solvent was applied onto the hole injection layer 41 with a spin coater so as to have a film thickness of 12 nm, and a TFB film was prepared at 200 ° C. The hole transport layer 42 was obtained by baking for 10 minutes. The refractive index of the hole transport layer 42 at a wavelength of 650 nm was 1.7 when measured by a FilTek manufactured by SCI.

  Subsequently, a solution obtained by dissolving a red polymer (“Light Emitting polymer ATS111RE” manufactured by American Dye Source) in a THF solvent is applied onto the hole transport layer 42 with a spin coater so that the film thickness becomes 70 nm. The light emitting layer 43 was obtained by baking for 10 minutes at 0 degreeC. The refractive index of the light emitting layer 43 at a wavelength of 650 nm was 1.7 when measured with a FilTek manufactured by SCI.

  In this example, barium Ba (manufactured by high-purity chemical) is formed as an electron injection layer (not shown) on the light-emitting layer 43 with a film thickness of 5 nm, and then Al (high-purity chemical) is formed on the electron injection layer. The cathode layer 5 was formed by vacuum deposition with a film thickness of 80 nm.

  Then, the board | substrate 2 which provided each layer mentioned above was accommodated in the glove box of the dew point-80 degreeC or less dry nitrogen atmosphere, and was conveyed, without exposing to air | atmosphere. In addition, a water-absorbing agent (manufactured by Dynic) was attached to a glass sealing cap (not shown), and an ultraviolet curable resin sealing agent was applied to the outer periphery of the sealing cap in advance. Then, in the glove box, the sealing cap is bonded to the substrate 2 with a sealing agent so as to surround each of the above layers, and each layer is sealed with the sealing cap by irradiating with ultraviolet rays to cure the sealing agent. Organic EL element 1 was obtained.

(Example 2)
An Al film was formed on the surface of the substrate 2 by vapor deposition under a vacuum of 2 × 10 ⁻⁴ Pa or less so as to directly have a film thickness of 5 nm, and the nanoparticle dispersion used in Example 1 was formed thereon. The liquid was applied on the substrate 2 on which an Al film having a thickness of 5 nm was formed by dip coating, and nanoparticles were deposited on the Al film. Next, in order to remove the organic component (lysine, F127) of the nanoparticle dispersion, UV ozone treatment was performed under the conditions of an ultraviolet wavelength of 172 nm, a pressure of 50 Pa, and an irradiation time of 30 min. Subsequently, an Al film is again deposited on the 5 nm thick Al film-coated substrate in which the nanoparticles are dispersed so as to have a thickness of about 2.5 nm by vapor deposition under a vacuum of 2 × 10 ⁻⁴ PaPa or less. A film was formed. After forming Al, the substrate with Al film was subjected to ultrasonic treatment in an aqueous ammonium fluoride solution for 30 minutes to remove the nanoparticles. In this way, an anode layer 3 having a recess 3a on the substrate 2 as shown in FIG. And the organic EL element 1 of Example 2 was obtained by the manufacturing method similar to Example 1 except the anode layer 3. FIG.

(Comparative Example 1)
An Al film was formed on the surface of the substrate 2 by a vapor deposition method under a vacuum of 2 × 10 ⁻⁴ Pa or less so as to directly have a film thickness of 7.5 nm. Thus, an anode layer 3 having no recess on the substrate 2 as shown in FIG. 4C was produced. And the organic EL element of the comparative example 1 was obtained by the manufacturing method similar to Example 1 except the anode layer 3. FIG.

(Comparative Example 2)
An anode layer 3 having a recess 3a on the substrate 2 was produced as shown in FIG. And the organic EL element of the comparative example 2 was obtained by the manufacturing method similar to Example 1 except the anode layer 3. FIG.

The light extraction efficiencies of Examples 1 and 2 and Comparative Examples 1 and 2 manufactured as described above are shown in Table 1 below. Regarding the light extraction efficiency, in Examples 1 and 2 and Comparative Examples 1 and 2, a current was passed between the electrodes so that the current density was 10 mA / cm ^2, and atmospheric radiation was measured with an integrating sphere. And the external quantum efficiency of atmospheric radiation light was computed based on these measurement results. Then, the external quantum efficiency of Comparative Example 1 was set to 1 and compared with Examples 1 and 2.

  As shown in Table 1 above, Example 1 in which the anode layer 3 has the recesses 3a and the organic layer 4 is also provided with the recesses 41a and the like is light extraction efficiency compared to the comparative example 1 in which the recesses 3a are not provided. Improved by about 20%. Further, in Comparative Example 2 in which the opening diameter of the concave portion 3a is small on the surface in contact with the organic layer 4, although the organic layer 4 is also provided with the concave portion 41a and the like, a short circuit occurs during light emission, and the characteristic evaluation is performed. I couldn't. In contrast, in Example 1, the organic layer 4 was provided with the recess 41a and the like, but no short circuit occurred. Moreover, in Example 1, since the recessed part 3a is disperse | distributed and arrange | positioned unevenly, the wavelength dependence and directivity of emitted light are hardly confirmed visually, and more natural light can be radiate | emitted. It was. Also in Example 2, the light extraction efficiency was improved compared to Comparative Example 1.

  The present invention is not limited to the embodiment, and various modifications can be made. In the embodiment described above, the anode layer 3 has the recess 3a and the light from the light emitting layer 43 is extracted from the substrate 2 through the anode layer 3, but the cathode layer 5 is provided with the recess. Alternatively, the light from the light emitting layer 43 may be extracted through the cathode layer 5. As described above, since the anode layer 3 has high translucency due to the provision of the recess 3a, Al, which is generally known as a constituent material of the cathode layer 5, is used as a constituent material of the anode layer 3 on the light extraction side. It can be. That is, at the stage where an Al film having a recess is formed on the substrate 2, the Al film can correspond to both the anode layer and the cathode layer, and the degree of freedom in device manufacturing can be increased.

1 Organic EL device 2 Substrate 3 Anode layer (electrode layer)
3a recess 4 organic layer 41a recess 42a recess 43 light emitting layer 43a recess 5 cathode layer (electrode layer)
P Center of recess

Claims (5)

An organic EL element comprising a substrate, a plurality of organic layers including a light emitting layer provided on the substrate, and a pair of electrode layers sandwiching the organic layer,
At least one of the electrode layers has a plurality of recesses on the surface in contact with the organic layer,
When the distance of the recesses parallel to the substrate is the opening diameter, the opening diameter increases as the organic layer approaches the organic layer, and when the center of the recesses is the center part, the center part of the plurality of recesses is between An organic EL device characterized in that the distance is not uniform.   Of the plurality of organic layers, the organic layer in contact with the electrode layer having the recess has a recess corresponding to each of the recesses of the electrode layer on a surface opposite to the electrode layer side of the organic layer. The organic EL device according to claim 1,   3. The organic EL element according to claim 2, wherein the light emitting layer in the organic layer has a concave portion corresponding to each of the concave portions of the electrode layer on a surface opposite to the electrode layer side of the light emitting layer. .   The organic EL element according to any one of claims 1 to 3, wherein an opening diameter of a concave portion of the electrode layer on a surface in contact with the organic layer is 2 nm to 1 µm.   5. The organic EL element according to claim 1, wherein the electrode layer having the recess has a maximum film thickness of 1 nm to 500 nm.

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