JP2011154843A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can improve light extraction efficiency and can be manufactured without receiving a restriction of the material or film-forming condition of an electrode and a luminous layer or the like. <P>SOLUTION: A nano particle arrangement layer 5 is arranged on the surface of a substrate 1. Then, a first electrode 2, an organic layer including a luminous layer 3, and a second electrode 4 are laminated in this order. By fine unevenness on the surface of the substrate 1 formed by the nano particle arrangement layer 5, fine unevenness can be formed on each surface of the first electrode 2, the luminous layer 3, and the second electrode 4, and a fine concavo-convex structure is formed in the interface of each layers to alleviate total reflection. Furthermore, since the nano particle arrangement layer 5 is formed of a silica nano particle 6, the material and film-forming condition of the electrode and the luminous layer or the like laminated on this do not receive restriction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element used for various applications such as display and illumination.

  FIG. 5 shows an example of the layer structure of an organic electroluminescence element (organic EL element). The transparent electrode 1 has a light transmissive or light reflective first electrode 2, a hole transport layer 8, light emission. The layer 3, the electron transport layer 9, and the light reflective or light transmissive second electrode 4 are sequentially laminated. In the organic EL element in which the first electrode 2 is formed of a light-transmitting anode and the second electrode 4 is formed of a light-reflecting cathode, by applying a voltage between the electrodes 2 and 4, the electron transport layer 9 The electrons injected into the light emitting layer 3 through the hole and the holes injected into the light emitting layer 3 through the hole transport layer 8 are recombined in the light emitting layer 3 to emit light. The light emitted from the light emitting layer 3 is extracted through the light transmissive first electrode 2 and the substrate 1.

  Here, 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. Thus, the light is totally reflected, confined in a medium having a high refractive index, and lost as guided light. Here, the substrate 1 generally used for the organic EL element is generally made of glass from the viewpoints of excellent transparency, strength, low cost, gas barrier properties, chemical resistance, heat resistance, etc. The refractive index of a soda lime glass or the like is 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 first electrode 2 because of its excellent transparency and electrical conductivity. The refractive index of ITO or IZO varies depending on its composition, film formation method, crystal structure, etc., but ITO is approximately 1.7 to 2.3, IZO is approximately 1.9 to 2.4, Has a high refractive index.

  In addition, light-emitting materials, electron-transporting materials, hole-transporting materials, and the like used for organic layers such as the light-emitting layer 3, the hole transport layer 8, and the electron transport layer 9 in an organic EL element have many benzene rings in their molecular structures. There are many π-conjugated bond materials included. For this reason, the refractive index is often about 1.6 to 2.0, which is higher than that of a general organic material.

  Therefore, in a general organic EL element, the refractive index of each layer is such that the atmosphere <substrate <organic layer <first electrode, and the light is emitted obliquely at a large angle from the light emitting layer 3 that is the light source of the organic EL element. The light is easily totally reflected at the interface between the first electrode 2 and the substrate 1 and at the interface between the substrate 1 and the atmosphere. If total reflection tends to occur in this way, the light extraction efficiency for extracting the light emitted from the light emitting layer 3 to the outside through the first electrode 2 and the substrate 1 is lowered.

  Therefore, in order to alleviate total reflection at the interface, it is performed to form fine irregularities at the interface. For example, in Patent Document 1, periodic unevenness is formed on a substrate with a curable resin layer or a polymer film, and an organic layer such as an electrode or a light emitting layer is formed on the unevenness formed with the curable resin layer or the polymer film. An organic EL element in which periodic irregularities are formed on each interface by sequentially forming the layers has been proposed (see Patent Document 1). According to this method, total reflection can be mitigated by the unevenness formed at the interface of each layer, and an improvement in light extraction efficiency can be expected.

  However, when a periodic concavo-convex structure is formed at the interface of each layer as in Patent Document 1, there is a risk that directivity may be generated in light emission or wavelength dependency may be generated as described in Patent Document 2. There is. In Patent Document 1, a curable resin layer or a polymer film is provided on a substrate in order to form a concavo-convex structure at the interface. However, since the curable resin or polymer film has low heat resistance, There is a problem that the materials of the electrodes and organic layers to be laminated on the film and the film forming conditions are limited.

JP 2009-9861 A JP 2006-313667 A

  The present invention has been made in view of the above points, and can improve the light extraction efficiency, and can be manufactured without being limited by materials such as electrodes and light-emitting layers and film formation conditions. An object of the present invention is to provide an electroluminescence element.

  The organic electroluminescence device according to the present invention has a nanoparticle array layer 5 disposed on the surface of a substrate 1, and a first electrode 2, an organic layer including a light emitting layer 3, and a second electrode 4 are laminated in this order. It is characterized by comprising.

  Thus, the substrate 1 formed by the nanoparticle array layer 5 by laminating the first electrode 2, the organic layer including the light emitting layer 3, and the second electrode 4 on the surface of the substrate 1 from above the nanoparticle array layer 5. By forming fine irregularities on the surface of the first electrode 2, the organic layer including the light emitting layer 3, and the second electrode 4, fine irregularities can be formed, and a fine irregular structure is formed at the interface of each layer. Thus, total reflection can be relaxed and light extraction efficiency can be improved. The nanoparticle array layer 5 is formed of nanoparticles, and is not limited by materials such as electrodes and light emitting layers stacked thereon and film formation conditions.

  Moreover, in this invention, the arrangement | sequence of the nanoparticle of said nanoparticle arrangement | sequence layer 5 is random, It is characterized by the above-mentioned.

  The random arrangement of the nanoparticles in this way allows a random uneven structure to be formed at the interface of each layer, and directivity occurs in the light emission like a periodic uneven structure. In this way, wavelength dependency does not occur.

  Further, the present invention is characterized in that the nanoparticle arrangement layer 5 has a structure in which silica nanoparticles 6 are monodispersed.

  As described above, the silica nanoparticles 6 forming the nanoparticle array layer 5 are inorganic compounds and have high heat resistance, and the electrodes stacked thereon are formed as in the case of forming irregularities with a curable resin layer or a polymer film. In addition, the silica nanoparticles 6 are monodispersed, so that a random uneven structure can be formed at the interface of each layer, and light emission is not limited. There is no directivity or wavelength dependency.

  The present invention is also characterized in that the nanoparticle arrangement layer 5 has a mesh structure formed by connecting silica nanoparticles 6 in a linear shape.

  As described above, the silica nanoparticles 6 forming the nanoparticle array layer 5 are inorganic compounds and have high heat resistance, and the electrodes stacked thereon are formed as in the case of forming irregularities with a curable resin layer or a polymer film. In addition, the silica nanoparticle 6 is a mesh formed by linear connection, so that a random uneven structure is formed at the interface of each layer. Thus, there is no directivity or wavelength dependency in the light emission.

  According to the present invention, fine irregularities on the surface of the substrate 1 formed by the nanoparticle array layer 5 cause fine irregularities on the surfaces of the first electrode 2, the organic layer including the light emitting layer 3, and the second electrode 4. It is possible to form a fine concavo-convex structure at the interface of each layer to alleviate total reflection and improve the light extraction efficiency. The material such as the light emitting layer and the film forming conditions are not limited.

BRIEF DESCRIPTION OF THE DRAWINGS It shows an example of embodiment of this invention, (a) is a schematic sectional drawing of the state which provided the nanoparticle arrangement | sequence layer in the board | substrate, (b) is a schematic sectional drawing which shows the layer structure of an organic EL element. . The colloidal solution used in the above is shown, and (a) and (b) are schematic views. The nanoparticle arrangement | sequence layer same as the above is shown, (a) (b) is a schematic perspective view. The nanoparticle arrangement | sequence layer same as the above is shown, (a) is the photograph which printed the SEM image of the state which the silica nanoparticle monodispersed, (b) printed the SEM image of the state which the silica nanoparticle connected in the mesh form It is a photograph. It is a schematic sectional drawing which shows the layer structure of the organic EL element of a prior art example.

  Embodiments of the present invention will be described below.

  In the present invention, the substrate 1 may be any substrate having optical transparency. For example, a transparent glass plate such as soda lime glass or non-alkali glass, a plastic film or a plastic plate produced by an arbitrary method from a resin such as polyester, polyolefin, polyamide, or epoxy, or a fluorine resin can be used. . Moreover, the glass plate which mixed heavy metals, such as lead, may be sufficient.

  In the present invention, first, as shown in FIG. 1A, a nanoparticle array layer 5 is formed on the surface of the substrate 1. The nanoparticle array layer 5 is formed by adhering nano-sized nanoparticles on the surface of the substrate 1 in a state of being randomly arrayed.

  Silica nanoparticles 6 can be used as the nanoparticles. The nanoparticle arrangement layer 5 formed of the silica nanoparticles 6 has a network structure in which the silica nanoparticles 6 are arranged in a monodispersed state, and the silica nanoparticles 6 are linearly connected and branched and circularly connected. There is a mesh structure to be arranged.

  First, the nanoparticle arrangement layer 5 formed with a monodisperse structure of silica nanoparticles 6 will be described. In the nanoparticle array layer 5 having a structure in which the silica nanoparticles 6 are monodispersed, the silica nanoparticles 6 are first prepared and monodispersed in a liquid, and then the liquid is applied to the surface of the substrate 1 to form the silica nanoparticles 6. Can be formed by adhering to the surface of the substrate in a monodispersed state.

  The method for preparing the silica nanoparticles 6 in the liquid is not particularly limited. For example, Non-Patent Document 1 (Masashi Fukao, Satoshi Shimojima, Tatsuya Okubo, one-dimensional arrangement of spherical silica nanoparticles using block copolymer, chemistry The 40th Autumn Meeting of the Society of Engineering (2008)), Non-Patent Document 2 (Ayane Sugawara, Atsushi Shimojima, Tatsuya Okubo, One-dimensional Array of Spherical Silica Nanoparticles by Interface Control, The 74th Annual Meeting of the Society of Chemical Engineers (2009 )). An alkoxysilane can be used as a raw material for the silica nanoparticles 6, and a tetrafunctional alkoxysilane is preferably used as the alkoxysilane. For example, tetraethoxysilane can be used. Here, silica is most suitable as a material for forming the nanoparticles of the present invention because it is easy to obtain nanoparticles with low cost, high transparency, and controllable particle size (Stober et al., J. Colloid lnterface Sci ., 26, 62-69 (1968)). Silica nanoparticles 6 have various advantages such as high heat resistance, high mechanical strength, and durability against chemicals such as organic solvents. Although the magnitude | size of the silica nanoparticle 6 is not specifically limited, It is preferable that it is the range of 10 nm or more and 100 nm or less.

  The silica nanoparticles 6 can be prepared in a liquid by adding an alkoxysilane to a solution in which a basic amino acid is dissolved and heating it to cause hydrolysis and polycondensation of the alkoxysilane. Silica produced by hydrolysis and polycondensation of alkoxysilane in the presence of a basic amino acid becomes a nano-sized sphere, and a colloidal solution 12 in which silica nanoparticles 6 are dispersed can be prepared.

  The liquid used for preparing the colloidal solution 12 in which the silica nanoparticles 6 are dispersed is not particularly limited, but water, alcohols such as methanol, ethanol, propanol, butanol, diethyl ether, dibutyl ether, tetrahydrofuran , Ethers such as dioxane, aliphatic hydrocarbons such as hexane, heptane and octane, aromatic hydrocarbons such as benzene, toluene and xylene, esters such as ethyl acetate and butyl acetate, methyl ethyl ketone and methyl isobutyl ketone And halogenated carbons such as methylene chloride and chloroform.

  Next, the block copolymer is added to the colloidal solution 12 in which the silica nanoparticles 6 are dispersed as described above, and stirred to dissolve uniformly. The block copolymer has different properties of hydrophilicity and hydrophobicity, and a block copolymer in which hydrophilic blocks and hydrophobic blocks are alternately copolymerized can be used. For example, a triblock copolymer obtained by copolymerizing a hydrophilic polyethylene oxide block on both sides of a hydrophobic polypropylene oxide block can be used.

  In this manner, the pH of the colloid solution 12 is adjusted with the block copolymer dissolved in the colloid solution 12. The pH can be adjusted using an acid such as hydrochloric acid or a base such as ammonia. The silica nanoparticles 6 can be monodispersed in the colloidal solution 12 by adjusting the pH. That is, when the pH of the colloid solution 12 is adjusted to be small, the silica nanoparticles 6 are connected in the colloid solution 12. At this time, the density of the components in the colloidal solution can be controlled according to the concentration, temperature, and elapsed time, and a linear structure or a mesh structure in which they are further connected can be formed. In contrast, when the pH of the colloidal solution is adjusted to be large, the silica nanoparticles 6 in the colloidal solution 12 are in a monodispersed state in which the individual particles are uniformly dispersed without agglomerating in a uniform size. Become. FIG. 2A shows a colloidal solution 12 in which silica nanoparticles 6 are monodispersed.

Here, a specific example is given about said method of monodispersing the silica nanoparticle 6 in the colloidal solution 12. FIG. By adding tetraethoxysilane (TEOS) to an aqueous solution of lysine (L-lysine), which is a basic amino acid, and stirring (500 rpm) at 60 ° C. for 24 hours, a colloidal solution 12 of silica nanoparticles 1 having a particle size of about 15 nm is obtained. be able to. The raw material molar ratio at this time is 1 (TEOS): 154.4 (H ₂ O): x (L-lysine). Next, block copolymer F127 (see [Chemical formula 1]) was added to the prepared colloid solution 12, and the mixture was stirred at 60 ° C. for 24 hours to dissolve F127. The amount of F127 added was, by mass ratio, SiO ₂ : F127 = 1: y based on the amount of silica in the colloidal solution 2. Subsequently, pH adjustment was performed using hydrochloric acid. Furthermore, the silica nanoparticles 6 can be dispersed in the colloidal solution 12 by standing at 60 ° C. for a certain time. At this time, when the pH was adjusted at y = 1 and pH 7.2 and left to stand at 60 ° C. for 2 weeks, if x = 0.01, the silica nanoparticles 6 were monodispersed. In addition, when x = 0.02 and y = 1 and the mixture was allowed to stand at 60 ° C. for 5 days after pH adjustment, the silica nanoparticles 1 were monodispersed at pH 8. Monodispersion was also confirmed in the silica nanoparticles 6 having a particle diameter of 30 nm.

  In the above [Chemical 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 the weight average molecular weight, and “HLB” is the Drophile-Lipophile. Balance, “CMC” is the critical micelle concentration.

  After the silica nanoparticles 6 are monodispersed in the colloid solution 12 as described above, the colloid solution 12 is applied to the surface of the substrate 1. When the colloidal solution 12 is applied to the surface of the substrate 1 in this manner, the silica nanoparticles 6 monodispersed in the colloidal solution 12 adhere to the surface of the substrate 1 while being monodispersed. The silica nanoparticles 6 are monodispersed in this way, and in principle, the individual silica nanoparticles 6 are arranged on the substrate 1 in a state where they are not in contact with each other, but some of the silica nanoparticles 6 are in contact with a plurality of particles. There may be some parts. The monodispersed silica nanoparticles 6 may be attached to the entire surface of the substrate 1 or may be attached to a part thereof. FIG. 3A is a view showing a state in which the nanoparticle array layer 5 having a monodispersed structure of the silica nanoparticles 6 is formed by attaching the silica nanoparticles 6 to the surface of the substrate 1 in a monodispersed state.

  Next, the nanoparticle arrangement | sequence layer 5 formed with the mesh structure of the silica nanoparticle 6 is demonstrated. As described above, when the colloid solution 12 in which the silica nanoparticles 6 are dispersed is prepared, when the pH of the colloid solution 12 is adjusted to be large, the silica nanoparticles 6 in the colloid solution 12 have uniform individual particles. When the colloidal solution 12 is adjusted so that the pH of the colloidal solution 12 is reduced, the silica nanoparticles 6 are linearly connected in the colloidal solution 12, A mesh-like mesh structure in which the linearly connected ones are further connected is formed. FIG. 2B illustrates a state in which the silica nanoparticles 6 are connected in a linear or mesh shape in the colloidal solution 12.

  That is, when the pH of the colloid solution 12 is adjusted to less than 8, for example, using an acid such as hydrochloric acid, the silica nanoparticles 6 start to be connected in the colloid solution 12 and are connected linearly. This connection structure is a ball chain-like arrangement in which silica nanoparticles 6 are connected linearly or in a curved shape, and one silica nanoparticle 6 is branched by connecting to three or more silica nanoparticles 6 and connected in a ring shape. Thus, a mesh-like mesh structure is obtained.

Here, a specific example is given about said method of connecting the silica nanoparticle 6 linearly in the colloidal solution 12. FIG. By adding tetraethoxysila (TEOS) to an aqueous solution of lysine (L-lysine), which is a basic amino acid, and stirring (500 rpm) at 60 ° C. for 24 hours, a colloidal solution 12 of silica nanoparticles 6 having a particle size of about 15 nm is obtained. be able to. The raw material molar ratio at this time is 1 (TEOS): 154.4 (H ₂ O): x (L-lysine). Next, block copolymer F127 (see the above [Chemical Formula 1]) was added to the prepared colloidal solution 12, and the mixture was stirred at 60 ° C. for 24 hours to dissolve F127. The amount of F127 added was, by mass ratio, SiO ₂ : F127 = 1: y based on the amount of silica in the colloidal solution 12. Subsequently, pH adjustment was performed using hydrochloric acid. Furthermore, the silica nanoparticles 6 were linearly connected in the colloidal solution 12 by being allowed to stand at 60 ° C. for a certain period of time. At this time, after adjusting the pH at y = 1, pH 7.2, and when allowed to stand at 60 ° C. for 2 weeks, if x = 0.02 or more, the silica nanoparticles 6 were linearly connected. In addition, when x = 0.02 and y = 1 and the mixture was allowed to stand at 60 ° C. for 5 days after pH adjustment, a linear linked structure of silica nanoparticles 6 was confirmed at pH 6.7. Further, when the addition amount of F127 was set to y = 0.5 to 2, a linear connection structure of the silica nanoparticles 6 was confirmed. Furthermore, a linear connection structure was also confirmed in the silica nanoparticles 6 having a particle diameter of 30 nm.

  As described above, after the silica nanoparticles 6 are connected in a linear or mesh shape in the colloid solution 12, the colloid solution 12 is applied to the surface of the substrate 1. When the colloid solution 12 is applied to the surface of the substrate 1 in this way, the silica nanoparticles 6 connected in a linear or mesh shape in the colloid solution 12 adhere to the surface of the substrate 4 to form a mesh structure. The mesh structure of the silica nanoparticles 6 may be such that linear connections may overlap each other, and does not have to be a complete two-dimensional plane. The mesh-structured silica nanoparticles 6 may be attached to the entire surface of the substrate 4 or may be attached to a part thereof. FIG. 3B is a view showing a state in which the silica nanoparticle 6 connected in a linear or mesh form is attached to the surface of the substrate 1 to form a nanoparticle array layer 5 having a mesh structure of the silica nanoparticle 6. .

  Here, the application of the colloidal solution 12 to the surface of the substrate 1 is not particularly limited. For example, brush coating, spray coating, dipping (dipping, dip coating), roll coating, flow coating, curtain coating, Various usual coating methods such as knife coating, spin coating, table coating, sheet coating, single wafer coating, die coating, and bar coating can be selected. Moreover, in order to process a coating film into arbitrary shapes, methods, such as cutting and etching, can also be used.

  Further, when the colloid solution 12 is applied to the surface of the substrate 1 as described above and the silica nanoparticles 6 are adhered to the surface of the substrate 1 to form the nanoparticle array layer 5, other than the silica nanoparticles 6, for example, a colloid solution It is preferable that other components such as basic amino acids in 12 and organic components such as block copolymers are removed so as not to exist on the surface of the substrate 1. As described above, as a method for removing other components, it is necessary to consider the durability of the substrate 1. However, the silica nanoparticles 6 are difficult to dissolve, but the substrate 1 is immersed in a solution that easily dissolves the component to be removed. The silica nanoparticles 6 remain on the substrate 1 by heat treatment, ultraviolet treatment, etc., but other components can be decomposed and volatilized and removed.

After forming the nanoparticle arrangement layer 5 made of the silica nanoparticles 6 on the surface of the substrate 1 as described above, the first electrode 2 is formed thereon. When the first electrode 2 is a light-transmitting anode, the first electrode 2 is an electrode for injecting holes into the light emitting layer 3. For this reason, it is preferable to form the first electrode 2 using an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function, and it is particularly preferable to use a material having a work function of 4 eV or more. Good. Examples of the material of the anode include conductive polymers such as metals such as gold, CuI, ITO (indium-tin oxide), SnO ₂ , ZnO, IZO (indium-zinc oxide), PEDOT, and polyaniline. And a conductive light-transmitting material such as a conductive polymer doped with any acceptor or the like, or a carbon nanotube. The first electrode 2 can be produced, for example, by depositing these electrode materials on the surface of the substrate 1 from above the nanoparticle array layer 5 in a thin film by a method such as vacuum deposition, sputtering, or coating. it can.

  The sheet resistance of the first electrode 2 is preferably several hundred Ω / □ or less, particularly preferably 100 Ω / □ or less. Here, the film thickness of the first electrode 2 varies depending on the material in order to control the light transmittance, sheet resistance, and other characteristics of the first electrode 2 as described above, but is 500 nm or less, preferably 10 to 200 nm. It is better to set the range. Although the case where the first electrode 2 is a light-transmitting anode has been described, the first electrode 2 may be formed as a light-reflecting cathode.

  And when the thin film of the 1st electrode 2 is formed in the surface of the board | substrate 1 from the nanoparticle arrangement | sequence layer 5 in this way, the surface of the board | substrate 1 is formed in the uneven structure by the silica nanoparticle 6 of the nanoparticle arrangement | sequence layer 5. Therefore, the uneven structure of the nanoparticle array layer 5 appears on the surface of the first electrode 2, and the surface of the first electrode 2 is also formed in the uneven structure.

  Next, the hole transport layer 8 is formed on the first electrode 2. The material used for the hole transport layer 8 can be selected from a group of compounds having hole transport properties, for example. 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, and triarylamine compounds, amine compounds containing carbazole groups An amine compound containing a fluorene derivative can be used, and any generally known hole transporting material can be used.

  The hole transport layer 8 can be produced, for example, by depositing these materials on a thin film on the surface of the first electrode 2 by a method such as vacuum deposition, sputtering, or coating. The film thickness of the hole transport layer 8 varies depending on the material and is not particularly limited, but is preferably set in the range of 10 to 200 nm.

  And when the thin film of the hole transport layer 8 is formed on the surface of the layer of the first electrode 2 in this way, the surface of the first electrode 2 is formed in a concavo-convex structure as described above. The uneven structure appears on the surface of the hole transport layer 8, and the surface of the hole transport layer 8 is also formed in the uneven structure.

  Next, the light emitting layer 3 is formed on the hole transport layer 8. As the material used for the light emitting layer 3, any material known as a light emitting material in the organic EL element can be used. For example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyxyl) Norinato) aluminum complex (Alq3), 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, 1-aryl-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, distyrylbenzene derivative, distyrylarylene derivative , And the like can be mentioned distyrylamine derivatives and various fluorescent pigments, not limited thereto. Moreover, it is also preferable to mix and use the light emitting material selected from these compounds suitably. Furthermore, not only a compound that generates fluorescence emission typified by the above-mentioned compound, but also a material system that emits light from a spin multiplet, for example, a phosphorescent material that generates phosphorescence emission, and a compound that includes a part thereof in a part of the molecule Can also be suitably used.

  The light emitting layer 3 may be formed by depositing these materials on a thin film by a dry process such as a vacuum deposition method, a sputtering method, or a transfer method, or a wet method such as spin coating, spray coating, die coating, or gravure printing. A thin film may be formed by a process. The film thickness of the light emitting layer 3 varies depending on the material and is not particularly limited, but is preferably set in the range of 10 to 200 nm.

  And when the thin film of the light emitting layer 3 is formed on the surface of the hole transport layer 8 in this way, the surface of the hole transport layer 8 is formed in an uneven structure as described above. Appearing on the surface of the light emitting layer 3, the surface of the light emitting layer 3 is also formed in an uneven structure.

  Next, the electron transport layer 9 is formed on the light emitting layer 3. The material used for forming the electron transport layer 9 can be appropriately selected from the group of compounds having electron transport properties. Examples of this type of compound include metal complexes known as electron transporting materials such as Alq3, and compounds having a heterocyclic ring such as phenanthroline derivatives, pyridine derivatives, tetrazine derivatives, oxadiazole derivatives, etc. Instead, any generally known electron transport material can be used. It is particularly preferable to use a material having a high charge transporting property.

  The electron transport layer 9 can be produced, for example, by depositing these materials on a thin film on the surface of the light emitting layer 3 by a method such as vacuum deposition, sputtering, or coating. Although the film thickness of the electron carrying layer 9 changes with materials and is not specifically limited, It is good to set to the range of 10-200 nm.

  And when the electron transport layer 9 thin film is formed on the surface of the hole transport layer 8 in this way, the surface of the hole transport layer 8 is formed in an uneven structure as described above. Appears on the surface of the electron transport layer 9, and the surface of the electron transport layer 9 is also formed in a concavo-convex structure.

Next, the second electrode 4 is formed on the electron transport layer 9. When the second electrode 4 is formed as a light reflective cathode, the second electrode 4 serves as an electrode for injecting electrons into the light emitting layer 3. For this reason, it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound and a mixture thereof having a low work function, and it is particularly preferable that the work function is 5 eV or less. Such cathode electrode materials include alkali metals, alkali metal halides, alkali metal oxides, alkaline earth metals, etc., and alloys of these with other metals such as sodium, sodium-potassium alloys, lithium Examples include magnesium, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, and Al / LiF mixture. Aluminum, Al / Al ₂ O ₃ mixture, etc. can also be used. Further, an alkali metal oxide, an alkali metal halide, or a metal oxide may be used as the base of the cathode, and one or more conductive materials such as metals may be stacked and used. For example, an alkali metal / Al laminate, an alkali metal halide / alkaline earth metal / Al laminate, an alkali metal oxide / Al laminate, and the like can be given as examples. Alternatively, the light reflective second electrode 4 may be configured by a combination of a transparent electrode and a light reflective layer. When the cathode is formed as a light transmissive electrode, the second electrode 4 may be formed of a transparent electrode material typified by ITO, IZO or the like. The organic layer at the interface with the second electrode 4 may be doped with an alkali metal such as lithium, sodium, cesium, or calcium, or an alkaline earth metal.

  The second electrode 4 can be produced, for example, by depositing these electrode materials in a thin film on the surface of the substrate 1 from above the electron transport layer 9 by a method such as vacuum deposition, sputtering, or coating. . The film thickness of the second electrode 4 varies depending on the material, but is preferably set in the range of 50 to 200 nm.

  And when the thin film of the 2nd electrode 4 is formed in the surface of the electron carrying layer 9 in this way, since the surface of the electron carrying layer 9 is formed in the uneven structure as mentioned above, the uneven structure of this electron transport layer 9 Appears on the surface of the second electrode 4, and the surface of the second electrode 4 is also formed in an uneven structure.

  As described above, the first electrode 2, the hole transport layer 8, the light emitting layer 3, the electron transport layer 9, and the second electrode 4 are sequentially laminated on the substrate 1, thereby forming a layer as shown in FIG. An organic EL element having a configuration can be produced. The organic layer is formed by the hole transport layer 8, the light emitting layer 3, and the electron transport layer 9. However, it goes without saying that the organic layer is not limited to such a layer configuration. It is also possible to form a layer structure in which layers are further provided.

  In the organic EL element manufactured as described above, the nanoparticle array layer 5 is provided on the surface of the substrate 1, and nano-level fine irregularities are formed on the surface of the substrate 1 by the silica nanoparticles 6. . The first electrode 2, the hole transport layer 8, the light emitting layer 3, the electron transport layer 9, and the second electrode 4 are laminated on the nanoparticle array layer 5. Asperities such as b) are formed, and an uneven structure is formed at the interface of each layer. Therefore, the total reflection of the light emitted from the light emitting layer 3 at the interface between the layers is alleviated, and the extraction efficiency of the light emitted from the substrate 1 can be improved.

  In addition, the silica nanoparticles 6 forming the nanoparticle array layer 5 have high heat resistance, mechanical strength, and chemical resistance. Therefore, the silica nanoparticles 6 are restricted by materials such as electrodes and light emitting layers stacked on the silica nanoparticles 6 or limited to film formation conditions. It is not to receive or receive.

  Further, the nanoparticle array layer 5 has a structure in which silica nanoparticles 6 are monodispersed or a mesh structure in which silica nanoparticles 6 are linearly connected, and the nanoparticle array layer 5 has a structure in which silica nanoparticles 6 are arrayed randomly. Therefore, the unevenness | corrugation formed in the 1st electrode 2, the hole transport layer 8, the light emitting layer 3, the electron carrying layer 9, and the 2nd electrode 4 becomes a random uneven structure. For this reason, there is no occurrence of directivity or wavelength dependency in the emission of light as in the case where a periodic uneven structure is formed at the interface of each layer.

  Next, the present invention will be specifically described with reference to examples.

Example 1
An aqueous solution was prepared by dissolving lysine (L-lysine) as a basic amino acid in water. Then, tetraethoxysilane (TEOS) was added to this basic amino acid aqueous solution and reacted in a water bath at 60 ° C. by stirring at a rotational speed of 500 rpm for 24 hours to prepare a colloidal solution of silica. The raw material molar ratio was 1 (TEOS): 154.4 (H ₂ O): 0.02 (L-lysine). Silica nanoparticles having a particle size of about 15 nm were formed in the colloidal solution thus obtained.

  Next, the block copolymer F127 as shown in [Chemical 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. The amount of F127 added was set to 1: 1 based on the mass of silica in the colloidal solution. Subsequently, hydrochloric acid was used to adjust the pH of the colloidal solution to 8, and the mixture was allowed to stand at 60 ° C. for 3 days for aging (see FIG. 2A).

  This solution was diluted 4 times with water to obtain a coating material. The above is carried out according to Non-Patent Documents 2 and 3.

  Next, this coating material was applied and adhered to the silicon substrate by dip coating. Subsequently, in order to remove the organic component (lysine, F127) of the coating material, 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 (see FIGS. 1A and 3A). . An SEM image of the surface of the substrate treated in this way is shown in FIG. As can be seen in the SEM image, it was confirmed that the silica nanoparticles were arranged in a monodispersed state without bonding between the particles on the substrate. Further, the substrate was changed to a non-alkali glass plate having a thickness of 0.7 mm (“No. 1737” manufactured by Corning), and silica nanoparticles were similarly attached to remove organic components. The glass substrate on which the silica nanoparticles are adhered is transparent when observed with the naked eye. When the haze and total light transmittance are measured with a haze meter (“NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd.), they are 0.08 and 91.9%, respectively. there were.

  Next, sputtering is performed on the surface of the glass substrate provided with the nanoparticle arrangement layer of silica nanoparticles as described above using an ITO (tin-doped indium oxide) target (manufactured by Tosoh Corporation) to form an ITO film having a thickness of 150 nm. did. The glass substrate on which this ITO film was formed was annealed at 200 ° C. for 1 hour in an Ar atmosphere to form a first electrode as a transparent electrode having a sheet resistance of 18Ω / □. When the refractive index was measured by “SCI3000” manufactured by FilmTek, nD = 1.78.

The glass substrate on which the first electrode was formed was subjected to ultrasonic cleaning with pure water, acetone, and isopropyl alcohol for 10 minutes each, then steam cleaned with isopropyl alcohol vapor for 2 minutes, dried, and further UV ozone cleaned for 10 minutes. Subsequently, the glass substrate was set in a vacuum deposition apparatus, and 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD) was thickened under reduced pressure of 5 × 10 ⁻⁵ Pa. Vapor deposition was performed to a thickness of 40 nm, and a hole transport layer was formed on the first electrode serving as the anode. Next, a light emitting layer in which Alq3 was doped with 6% rubrene was provided on the hole transport layer with a thickness of 30 nm. Further, 1,3,5-tri [p- (3-pyridyl) phenyl] benzene (TpPyPhB: [Chemical Formula 2]) was formed to a thickness of 65 nm as an electron transporting layer. A LiF film having a thickness of 1 nm was formed thereon as an electron injection layer.

  Thereafter, as a light-reflective cathode, Al was deposited to a thickness of 80 nm to form a second electrode, and an organic EL element having a layer structure as shown in FIG. 1B was obtained.

(Example 2)
An aqueous solution was prepared by dissolving lysine (L-lysine) as a basic amino acid in water. Then, tetraethoxysilane (TEOS) was added to this basic amino acid aqueous solution and reacted in a water bath at 60 ° C. by stirring at a rotational speed of 500 rpm for 24 hours to prepare a colloidal solution of silica. The raw material molar ratio was 1 (TEOS): 154.4 (H ₂ O): 0.02 (L-lysine). Silica nanoparticles having a particle size of about 15 nm were formed in the colloidal solution thus obtained.

  Next, the block copolymer F127 as shown in [Chemical 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. The amount of F127 added was set to 1: 1 based on the mass of silica in the colloidal solution. Subsequently, hydrochloric acid was used to adjust the pH of the colloidal solution to 7, and the mixture was allowed to stand at 60 ° C. for 3 days for aging (see FIG. 2B).

  This solution was diluted 4 times with water to obtain a coating material. The above is carried out according to Non-Patent Documents 2 and 3.

  Next, this coating material was applied and adhered to the silicon substrate by dip coating. Subsequently, in order to remove the organic component (lysine, F127) of the coating material, 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 (see FIGS. 1A and 3B). . An SEM image of the surface of the substrate thus treated is shown in FIG. As can be seen in the SEM image, the silica nanoparticles are connected in units of several to several tens, forming a mesh structure on the surface of the substrate, and confirming that the nanoparticle array layer is formed on the surface of the substrate It was done. Further, the substrate was changed to a non-alkali glass plate having a thickness of 0.7 mm (“No. 1737” manufactured by Corning), and silica nanoparticles were similarly attached to remove organic components. The glass substrate on which the silica nanoparticles are adhered is transparent when observed with the naked eye. When the haze and total light transmittance are measured with a haze meter (“NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd.), they are 0.09 and 91.8%, respectively. there were.

  Then, the first electrode, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, and the second electrode are formed on the surface of the glass substrate provided with the nanoparticle arrangement layer of the silica nanoparticles in the same manner as in Example 1. As a result, an organic EL element having a layer structure as shown in FIG. 1B was obtained.

(Comparative Example 1)
A non-alkali glass plate having a thickness of 0.7 mm (“No. 1737” manufactured by Corning) was used as the substrate as it was, and the first electrode, hole transport layer, and light emitting layer were formed on the surface of this glass substrate in the same manner as in Example 1. Then, an organic EL device was obtained by forming an electron transport layer, an electron injection layer, and a second electrode.

With respect to the organic EL elements obtained in each of the above Examples and Comparative Examples, 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.

  In addition, a hemispherical lens made of glass was placed on the light emitting surface of the organic EL element through matching oil having the same refractive index as that of glass, and the same measurement as described above was performed to measure the substrate arrival light. Based on these measurement results, the external quantum efficiencies of the atmospheric radiation light and the substrate arrival light were calculated. The external quantum efficiency is the ratio of photons emitted relative to the number of electrons injected into the light emitting layer and recombined. The external quantum efficiency of atmospheric radiation is calculated from the applied current of the organic EL element and the amount of atmospheric radiation. The external quantum efficiency of the light reaching the substrate is calculated from the applied current of the organic EL element and the amount of light reaching the substrate.

  The results are shown in Table 1. In Table 1, the external quantum efficiency of the atmospheric radiation light of Comparative Example 1 was set to 1, and the ratio was obtained and shown.

  As seen in Table 1, it is confirmed that the organic EL elements of Example 1 and Example 2 according to the present invention have an excellent external quantum efficiency ratio as compared with Comparative Example 1.

DESCRIPTION OF SYMBOLS 1 Substrate 2 First electrode 3 Light emitting layer 4 Second electrode 5 Nanoparticle arrangement layer 6 Silica nanoparticle

Claims (4)

  1. An organic electroluminescence device comprising: a nanoparticle array layer disposed on a surface of a substrate; and a first electrode, an organic layer including a light emitting layer, and a second electrode stacked thereon in this order.   2. The organic electroluminescence device according to claim 1, wherein the nanoparticle arrangement of the nanoparticle arrangement layer is random.   The organic electroluminescence device according to claim 1 or 2, wherein the nanoparticle arrangement layer has a structure in which silica nanoparticles are monodispersed.   The organic electroluminescence device according to claim 1 or 2, wherein the nanoparticle array layer has a mesh structure formed by linearly connecting silica nanoparticles.