JP2008112592A - Organic el element having microstructure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an organic EL element provided with a color conversion mode, which enables to relatively inexpensively obtain light with a desired color without unnecessarily complicating the structure of an organic light-emitting layer, while having a light extraction structure for highly efficiently extracting light-emission of the organic light-emitting layer to the outside of the organic EL element. <P>SOLUTION: The organic EL element having a microstructure includes a transparent substrate, which has a microstructure layer on at least either one of its surfaces, a transparent electrode formed on the transparent substrate, and an organic light-emitting layer formed on the transparent electrode while including a light-emitting layer that emits light. At least one microstructure layer is composed so that a fluorescent material is almost uniformly dispersed in the microstructure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL element having a fine structure capable of extracting light with high efficiency and a manufacturing method thereof, and more particularly to an organic EL element used as a surface light source.

  As shown in FIG. 7, the bottom emission type organic EL element is configured by sequentially laminating a transparent electrode 20 (anode), an organic light emitting layer 24, and a metal electrode 22 (cathode) on a transparent substrate 10. Here, the organic light emitting layer 24 may include at least a light emitting layer 26 and a plurality of other layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer. When a DC voltage is applied between the two electrodes, the anode 20 and the cathode 22, holes and electrons are sent to the light emitting layer 26, and recombination occurs in the light emitting layer 26, and the light generated by the energy generated by the recombination 26. The electronic state of the contained organic molecule is excited to an excited state. When this unstable electronic state falls to the ground state, energy is emitted as light from the lower transparent substrate 10 side, and the organic EL element 101 emits light.

  On the other hand, in a top emission type organic EL device, light is extracted from the upper transparent electrode (cathode) side by forming a substrate or an anode from a metal and making a cathode transparent.

  Light emission is generated by the same mechanism in any of the above-described organic EL elements. For example, in the bottom emission organic EL element 101 shown in FIG. 7, the ratio of the amount of light transmitted through the transparent substrate 10 is emitted by the organic light emitting layer 26. It is known that it is about 20% of the amount of light emitted. This decrease in the amount of light is mainly caused by the light guide mode caused by light emission in the layer direction substantially perpendicular to the light extraction direction, reflection or scattering occurring in each layer or on the transparent substrate surface. It is known that light loss is caused by about 60% mainly by the waveguide mode 1 generated by the organic light emitting layer 24 and the transparent electrode 20, and by about 20% by the waveguide mode 2 mainly caused by the transparent substrate 10.

The organic EL element is expected not only as a display but also as a surface light source for illumination such as a light source for indoor illumination and a backlight for liquid crystal. This is because the thickness is much thinner than conventional fluorescent lamps and incandescent lamps, and it is expected to obtain the same level of brightness with low power consumption. An organic EL element used as a display element of a display can be used with a luminance of about 200 cd / m ^2, but generally 8000 cd / m when used as a light source for illumination. A luminance of ² or more is required. Therefore, particularly when used as a light source for illumination, increasing the light extraction efficiency of the organic EL element is an essential technical problem.

  For this reason, various techniques for improving the light extraction efficiency of the organic EL element have been developed. For example, an airgel inserted between a glass substrate and ITO reduces waveguide mode 1 (Non-patent document 1), and a mesa-shaped uneven dot is formed to reduce waveguide mode 1 (non-patent document 2). A microlens is formed on the glass substrate side to reduce the waveguide mode 2, and a 550 nm silica sphere is arranged on the glass substrate side to reduce the waveguide mode 2 (Non-Patent Document 3), and EL dots are formed. In addition, a triangular micromirror is disposed to reduce the waveguide modes 1 and 2 (Non-patent Document 4), and a waveguide mode 1 is reduced using a substrate having a refractive index similar to that of the organic light emitting layer. Has been devised.

  However, all of these light extraction technologies are under development, and have not reached a satisfactory level as a light extraction technology for an organic EL element for a surface light source.

Japanese Patent Laying-Open No. 2005-71920 (paragraphs 12 and 13) Japanese Patent Laying-Open No. 2005-276581 (Claim 1, Paragraph 32) AdvancedMaterials.Vol.13, No.15 (2001) p.1149 Optics Lett., Vol. 22, No. 6 (1997) p.396 Appl.Phys.Lett., Vol.76, No.10 (2000) p.1243 Information Display, 4 & 5/02 (2002) p.22

  In addition, Patent Document 1 discloses a device configuration of a novel organic EL element for a surface light source. A composite light-emitting device (organic EL element) described in Patent Document 1 has a phosphor film placed in a direction substantially perpendicular to a light extraction direction adjacent to a light-emitting medium sandwiched between two electrodes. The phosphor film absorbs the light emitted from the electrode substantially in the horizontal direction and emits light from the phosphor film. Therefore, a part of light emission lost by the waveguide mode 1 can be supplemented by absorption and emission of light by the fluorescent film.

  However, in the invention of Patent Document 1, only light emitted from the fluorescent film in the light extraction direction is supplemented, and only part of the waveguide mode 1 is compensated as compared with the conventional example. In addition, it is considered that the loss due to the waveguide mode 2 is substantially the same as that of a conventional organic EL element for a surface light source.

  On the other hand, Patent Document 2 discloses an invention that mainly compensates for light loss due to the waveguide mode 2. The invention of Patent Document 2 improves the extraction efficiency of light emitted from the organic light emitting layer 24 by providing a plurality of minute convex portions on the lower surface of the transparent substrate 10 in FIG. In other words, the projections prevent light reflection at the interface between the surface of the transparent substrate 10 and the air, and prevent scattering of light transmitted through the transparent substrate 10.

  However, in order to extract light of various colors as a surface light source for illumination, or to obtain a more beautiful white color, various design changes such as selection of a material of the light emitting layer for the desired color are unavoidable. For example, whitening by MPE (Multi-Photon Emission) as shown in FIG. 5 complicates the structure of the organic light emitting layer and increases the manufacturing cost.

  Therefore, the present invention has a light extraction structure for extracting light emitted from the organic light emitting layer to the outside of the organic EL element with high efficiency, and a desired color at a relatively low cost without complicating the structure of the organic light emitting layer. An object of the present invention is to obtain an organic EL element having a color conversion mode capable of obtaining the above light.

  An organic EL device having a microstructure of the present invention is a transparent substrate having a microstructure layer on at least one surface thereof, a transparent electrode formed on the transparent substrate, and formed on the transparent electrode to emit light. An organic light emitting layer including a light emitting layer to be performed, and at least one of the fine structure layers has a fluorescent material substantially uniformly dispersed in the fine structure.

  In the organic EL element having a microstructure according to the present invention, the microstructure layer includes a plurality of convex portions or concave portions, and the shape of the convex portions or concave portions is a cone, a pyramid, a cylinder, a prism, a truncated cone, or a truncated pyramid. Can be included.

  The organic EL element having a microstructure of the present invention is characterized in that the refractive index of the transparent substrate and the microstructure layer is substantially equal.

  In the organic EL device having a microstructure of the present invention, the transparent substrate is preferably a glass substrate, and the microstructure layer is preferably formed of an organic-inorganic hybrid material.

  The organic EL device having a microstructure of the present invention is characterized in that a planarization layer is formed between the transparent substrate and the transparent electrode, and the refractive index of the planarization layer is substantially equal to the refractive index of the transparent electrode. To do.

In the organic EL device having the microstructure according to the present invention, the transparent electrode is made of IZO (Indium Zinc).
Oxide) or ITO (Indium Tin Oxide), and the planarization layer preferably includes a metal oxide of titanium.

  In the organic EL device having the microstructure of the present invention, the fluorescent material may be a fluorescent dye or a fluorescent pigment.

  In the organic EL device having a microstructure of the present invention, the fluorescent pigment is preferably selected from organic dye laser materials, and the fluorescent pigment may be selected from cyanine dyes.

  The organic EL device having a microstructure according to the present invention is characterized in that the fluorescent material that absorbs light emitted from the light emitting layer generates light having a wavelength longer than the wavelength of the light emitted.

  In the organic EL device having a fine structure of the present invention, it is preferable that the light emitting layer emits green or blue light.

  In the organic EL device having a microstructure of the present invention, the fluorescent materials that emit light of different wavelengths may be dispersed in the microstructure layer formed on both surfaces of the transparent substrate. The combined light of the light emission of the light emitting layer and the light emitted from each of the fluorescent materials that has absorbed the light emission may be white light.

  Since the organic EL device having the microstructure of the present invention has a microstructure layer including a plurality of convex portions or concave portions on at least one surface of the transparent substrate, the light extraction efficiency can be improved. That is, assuming that the direction from the organic light emitting layer toward the transparent substrate is the downward direction, by providing the fine structure layer on the lower side (light extraction side) of the transparent substrate, light reflection at the interface between the transparent substrate surface and the air is performed. The light extraction efficiency can be improved by preventing light scattering through the transparent substrate (light extraction function by substrate mode control). Similarly, by providing a fine structure layer on the upper side (transparent electrode side) of the transparent substrate and filling the fine structure layer with a material close to the refractive index of the transparent electrode to form the flattening layer, the flattening layer and the fine structure are formed. Light extraction efficiency can be improved by preventing reflection and scattering of light between layers (light extraction function by thin film mode control).

  In addition, the transparent substrate is a glass substrate, the microstructure layer is formed of an organic-inorganic hybrid material, and the refractive index of the transparent substrate and the microstructure layer is substantially equal, thereby further enhancing the light extraction function by the substrate mode control. Can do.

  Similarly, the transparent electrode is formed from IZO (Indium Zinc Oxide) or ITO (Indium Tin Oxide), and the planarization layer is formed to contain a metal oxide such as titanium, and the refractive index of the planarization layer and the transparent electrode By making it substantially equal to the refractive index, the light extraction function by the thin film mode control can be further enhanced.

  In addition, in the organic EL device having the microstructure of the present invention, since at least one microstructure layer formed on the transparent substrate has a fluorescent material dispersed substantially uniformly in the microstructure, the light emission of the light emitting layer The fluorescent material that has absorbed the light generates light having a wavelength longer than the emission wavelength, whereby mixed light of the light emitted from the light emitting layer and the fluorescent material can be extracted (color conversion mode). Unlike the conventional MPE (Multi-Photon Emission) structure, various mixed lights can be extracted by selecting and combining fluorescent materials and light emitting layer materials at a lower cost without complicating the structure of the organic light emitting layer. . By making the light emitting layer emit blue or green short-wavelength light and selecting a suitable material from fluorescent dyes or fluorescent pigments as the fluorescent material, the above-mentioned various mixed lights can be extracted.

  Furthermore, mixed light of three colors can be extracted by dispersing fluorescent materials that emit light of different wavelengths in the fine structure layers formed on both surfaces of the transparent substrate. By selecting / combining a suitable light emitting layer material and fluorescent material, the synthesized light can be converted into white light to obtain an organic EL device that emits white light.

  As shown in FIG. 1, the organic EL element 1 of the present embodiment includes a transparent substrate 10 having a microstructure layer 12 including a plurality of protrusions 14 on both surfaces, and a transparent electrode 20 formed on the transparent substrate 10. The organic light emitting layer 24 including the light emitting layer 26 that emits light is formed on the transparent electrode 20, and the light reflecting electrode 22 is formed on the organic light emitting layer 24. In the present embodiment, the organic EL element 1 is a bottom emission type, and light is extracted from the transparent electrode 20 downward (in the direction from the organic light emitting layer 24 toward the transparent electrode 20).

  In the organic EL element 1 of the present invention, at least one of the fine structure layers 12 has the fluorescent material dispersed substantially uniformly in the fine structure 12 (convex portion 14).

  The organic light-emitting layer 24 may include a plurality of organic layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer in addition to the light-emitting layer 26. The other organic layers are collectively referred to as the organic light emitting layer 24.

  The structures and materials of the components of the organic EL element 1 other than the fine structure layer 12 such as the organic light emitting layer 24 and the light reflecting electrode 22 may be known configurations and are not particularly limited.

  Accordingly, the transparent substrate 10 may be formed of glass, other transparent resin, or the like, and is not particularly limited. However, it is desirable that the refractive index of the fine structure layer 12 is substantially equal to the refractive index of the transparent substrate 10. The material of the microstructure layer 12 is not particularly limited as long as it is substantially equal to the refractive index of the transparent substrate 10. For example, when a glass substrate having a refractive index of about 1.5 is adopted as the transparent substrate 10, the microstructure layer 12 is refracted with the glass substrate. It is preferable to form the organic / inorganic hybrid material having a close ratio. The difference in refractive index between the transparent substrate 10 and the fine structure layer 12 is preferably within ± 0.01.

  A method of forming the microstructure layer 12 will be described later. A film using an organic-inorganic hybrid material for forming the microstructure layer 12 is obtained by applying a liquid obtained by diluting a metal alkoxide composition in a solvent onto a glass substrate. It can be obtained by curing in the form of a film.

  The metal alkoxide composition preferably contains (a) an organic polysiloxane having a methyl group or a phenyl group, (b) an organic siloxane having a hydroxyl group or a hydrolyzable functional group, and (c) a curing agent.

  Examples of the organic polysiloxane having a methyl group or a phenyl group in (a) above include liquid organic polysiloxanes having a methyl group or a phenyl group and an alkoxy group having 1 to 4 carbon atoms. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

  Examples of the hydrolyzable group in the organic siloxane having a hydroxyl group or a hydrolyzable functional group (b) include an alkoxy group, an acyloxy group, a ketoxime group, an amide group, an alkenyloxy group, and a halogen atom. The The component (b) organosiloxane may have a monovalent organic group or a hydrogen atom. Examples of the monovalent organic group include alkyl groups such as methyl, ethyl, propyl, butyl and hexyl; vinyl , Alkenyl groups such as allyl; aryl groups such as phenyl, tolyl, xylyl; aralkyl groups such as phenethyl and β-phenylpropyl; aminoalkyl groups such as N- (β-aminoethyl) -γ-aminopropyl; Epoxy group-containing groups such as sidoxypropyl and 3,4-epoxycyclohexyl; (meth) acryl group-containing groups such as γ-methacryloxypropyl; mercaptoalkyl groups such as γ-mercaptopropyl; cyanoalkyl groups such as cyanoethyl; β A chloroalkyl group such as chloroethyl and γ-chloroethyl; a chloroalkyl group such as 3,3,3-trifluoropropyl; Examples include a uroalkyl group and the like. The component (b) may contain an alkoxy partial hydrolyzate (liquid silicone resin) as necessary.

  As the curing agent (c), a curing catalyst used in a condensation curable silicone composition is usually used. Specific examples of the curing agent include: organic amines such as triethanolamine; carboxylic acid metal salts such as tin octylate and zinc octylate; organotin compounds such as dibutyltin dilaurate and dibutyltin dioctoate; tetrabutyl titanate, tetrapropyl titanate Quaternary ammonium compounds such as quaternary ammonium carboxylates; amine-based silane cups such as γ-aminopropyltriethoxysilane and N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane A ring agent is mentioned. An organoaluminum compound or boron halide can also be used. Among these, an organic tin compound or a boron halide is preferable. Two or more of these curing agents can be used in combination.

  The solvent used in preparing the solution is not particularly limited as long as it dissolves and disperses the component (a), the component (b), and the component (c). For example, alcohols such as methanol, ethanol and isopropanol; ether alcohols and ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, tetrahydrofuran and dioxane; ketones such as acetone, methyl ethyl ketone and diethyl ketone; methyl acetate and ethyl acetate And esters such as n-butyl acetate; aliphatic hydrocarbons such as n-hexane, gasoline, rubber volatile oil, mineral spirit, and kerosene.

  By applying the metal alkoxide composition as described above to the substrate and performing a dehydration condensation reaction by a hydrolysis reaction of the metal alkoxide at a relatively low temperature, a light-transmitting film in which three-dimensional crosslinking is formed is formed.

  As shown in FIG. 2, the fine structure layer 12 includes a plurality of convex portions 14. Alternatively, the organic / inorganic hybrid material may be formed with a recess (see FIG. 3). The shape of the convex portion or the concave portion includes a cone, a pyramid, a cylinder, a prism, a truncated cone, a truncated pyramid, and the like, and the pitch of the concave and convex portions and the height thereof are preferably 10 nm to 10 μm.

  The fluorescent material is a fluorescent dye 16 as shown in FIG. 2 (a) or a fluorescent pigment 17 as shown in FIG. 2 (b). The fluorescent material such as the fluorescent dye 16 and the fluorescent pigment 17 is substantially uniformly dispersed in at least one microstructure layer 12 formed on both surfaces of the transparent substrate 10. Therefore, the fluorescent material is substantially uniformly dispersed in the convex portions (or concave material) constituting the microstructure layer 12. The fluorescent pigment is preferably selected from organic dye laser materials such as cyanine dyes.

  Further, when the transparent electrode 20 is laminated on the fine structure layer 12 formed on the transparent substrate 10, it is necessary to flatten the fine structure layer 12. In order to increase the light extraction efficiency of the fine structure layer 12, it is preferable to adjust the refractive index of the flattening layer for flattening the fine structure layer 12 to be substantially the same as the refractive index of the transparent electrode 20. Therefore, for example, when IZO (Indium Zinc Oxide) or ITO (Indium Tin Oxide) having a refractive index of about 2.0 is used as the transparent electrode 20, a metal oxide such as aluminum, germanium, or zirconium mainly composed of titanium. Etc. are filled so that the fine structure layer 12 is filled, and a planarization layer is formed, and the refractive index of the planarization layer is approximated to the refractive index of the transparent electrode 20 such as ITO. By adjusting the refractive index of the planarizing layer, the light extraction efficiency by the fine structure layer 12 on the transparent substrate 10 can be increased. Note that the planarization layer may be formed between the transparent substrate 10 and the transparent electrode 20 even when the fine structure layer 12 is not provided.

  In the organic EL element 1 of the present embodiment as described above, the light emitted from the light emitting layer 26 passes through the organic light emitting layer 24, the transparent electrode 20, or is reflected by the light reflecting electrode 22 and then passes through each layer. In some cases, the light passes through the structural layer 12 and the transparent substrate 10 and is extracted to the outside at the same wavelength (the arrow on the left in FIG. 4). On the other hand, the light emitted from the light emitting layer 26 is once absorbed by the fluorescent material in the fine structure layer 12, and light having a wavelength specific to the fluorescent material is re-emitted, transmitted through the transparent substrate 10 and the like, and extracted outside. Also occurs (arrow on the right in FIG. 4).

  In this case, the light re-emitted from the microstructure layer 12 has energy lower than that of the light absorbed by the fluorescent material in principle, that is, the light emitted from the light-emitting layer 26. It becomes longer than the wavelength of the light emitted from 26. Therefore, the extracted light from the organic EL element 1 becomes a mixed light of two colors of light emitted from the light emitting layer 26 and the fluorescent material.

  That is, synthetic light having different wavelengths can be extracted from the organic EL element 1 by selecting and combining various organic materials and fluorescent materials constituting the light emitting layer. When the fluorescent material that has absorbed the light emission of the light emitting layer generates a complementary color of the light emission, white synthetic light can also be obtained. However, as described above, since the emitted light of the light emitting layer 26 needs to have higher energy than the re-emitted light of the fluorescent material, the light emitting layer 26 preferably emits light having a short wavelength of green to blue.

  Next, an example of the manufacturing method of the organic EL element 1 of the present invention will be described. In order to form the microstructure layer 12 on one side or both sides of the transparent substrate 10, a conventional photolithography method may be used. However, in this embodiment, a nanoimprint method that is excellent in mass productivity and can achieve cost reduction is used.

(1) A glass substrate is prepared as the transparent substrate 10, and ultrasonic cleaning is performed using pure water or the like.
(2) The liquid mixture of the organic-inorganic hybrid material and the fluorescent material described above is applied to one side or both sides of the glass substrate using spin coating or the like.
(3) The whole substrate coated with the mixed solution is heated with a hot plate or the like at several tens of minutes to several 10 to 100 ° C. to semi-cure the liquid mixed solution.
(4) The substrate on which the surface has been semi-cured is subjected to thermocompression bonding after being pressure-bonded with a mold manufactured in advance to form the fine structure layer 12. The pressure bonding condition is several 10 to 2000 N / cm ² , and the heating condition is several 10 to 500 ° C. and several 10 minutes.
(5) Release the mold from the substrate and cool the substrate by leaving it alone. By this step, the fine structure layer 12 (FIGS. 3 (a) and (b)) made of convex portions or the fine structure layer 12 (FIGS. 3 (c) and (d)) made of concave portions is formed on one side of the glass substrate. Formed on both sides.
(6) When laminating the transparent electrode 20 such as IZO on the hard microstructured layer 12, the hole portion of the microstructure layer 12 is filled with a metal oxide such as aluminum or germanium mainly composed of titanium. Thus, a planarizing layer for planarizing the fine structure layer 12 is formed.

Thereafter, similar to the known method for manufacturing an organic EL element, the transparent electrode 20 / the organic light emitting layer 24 / the light reflecting electrode 22 are repeatedly formed on the planarized fine structure layer 12 by repeating the lamination and patterning of materials. An example of these materials and thicknesses is transparent electrode IZO (200 nm) / hole transport layer TPD (50 nm) / light emitting layer Alq ₃ (50 nm) / electron injection layer LiF (1 nm) / light reflecting electrode Al (70 nm). The material stacking method is a sputtering method or vacuum deposition.

  The organic light emitting layer 24 and the like are covered with a cap so that the organic light emitting layer 24 does not come into contact with outside air. When covering, the portion surrounded by the transparent substrate 10 and the cap is preferably filled with an inert gas. It is also preferable to place a desiccant on the surface of the cap facing the metal electrode 22.

The organic EL element 1 of the present invention manufactured as described above realizes the light extraction structure and the color conversion mode, which are the objects of the above invention, by the following three functions. That is,
(Function 1) A light extraction function by substrate mode control by providing the fine structure layer 12 below the transparent substrate 10 (light extraction side).
(Function 2) A thin film (flat surface) in which the fine structure layer 12 is provided on the upper side (transparent electrode 20 side) of the transparent substrate 10 and the fine structure layer is filled with a material having a refractive index close to that of the transparent electrode 20 Light extraction function by mode control.
(Function 3) A color conversion mode and a light extraction function by forming the fine structure layers 12 on the upper and lower sides of the transparent substrate 10 by dispersing the fluorescent material substantially uniformly.

  The light extraction efficiency by the above functions is expected as shown in FIG. The graph of FIG. 6 shows that (0) is an organic EL element having no functions 1 to 3, (1) is an organic EL element having only function 1, (2) is an organic EL element having functions 1 and 2, and (3) The light extraction efficiency (%) of the organic EL element having the function 3 is shown.

  The organic EL element 1 of the present invention corresponds to the organic EL element (3) having the function 3, but the light extraction efficiency is higher than that of the organic EL element having the function (1) and / or (2) according to FIG. Is high.

  Moreover, since the organic EL element 1 of the present invention having the function 3 has a color conversion mode unlike the organic EL element having the functions (1) and / or (2), the structure of the organic light emitting layer 24 is complicated. The desired color light can be obtained relatively inexpensively.

  The organic EL element 1 having a fine structure according to the present invention has been described above, but the organic EL element of the present invention is not limited to the above embodiment. In the above embodiment, the fine structure layer 12 in which the fluorescent material is dispersed is formed on both surfaces of the transparent substrate 10, but may be formed only on one surface. If the fine structure layer 12 in which the fluorescent material is dispersed is formed on at least one surface, the light extraction efficiency is lower than that formed on both surfaces, but the organic EL device of the present application having the light extraction structure and the color conversion mode is provided. 1 can be produced.

  The kind of material of the fluorescent dye and fluorescent pigment is not particularly limited to the above examples. In order to obtain a desired color, the fluorescent material can be appropriately selected depending on the combination with the emission color depending on the material and composition of the emission layer.

  Therefore, if fluorescent materials that emit light of different colors are dispersed in the fine structure layer 12 above and below the transparent substrate 10, combined light of the three colors combined with the light emission color of the light emitting layer 26 is generated. It can also be taken out from the organic EL element 1. Accordingly, a white surface light source can be obtained by combining three colors of blue, green, and red.

  Further, the light emitted from the light emitting layer 26 may be fluorescence or phosphorescence. The organic EL element 1 of the present invention can achieve the high light extraction efficiency shown in FIG. 6 regardless of the light emitted from the light emitting layer 26.

  The organic EL element 1 is a bottom emission method, but may be a top emission method. That is, in FIG. 1, the substrate 10 and / or the anode 20 may be formed of metal, and light may be extracted from the cathode side as a transparent electrode. The organic light emitting layer 24 and the electrodes 20 and 22 may be sealed with a transparent cap, and the transparent cap may be provided with a fine structure layer and a color conversion mode.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the gist thereof.

  The present invention can be used in various applications such as a display, a backlight for a liquid crystal display, and lighting inside and outside a building.

It is sectional drawing of the organic EL element with the fine structure of this invention. (a) is the convex part of the fine structure layer which disperse | distributed fluorescent dye, (b) is the convex part of the fine structure layer which disperse | distributed the fluorescent pigment. (a) is a perspective view of a microstructure layer composed of convex portions, (b) is a cross-sectional view of a microstructure layer composed of convex portions, (c) is a perspective view of a microstructure layer composed of concave portions, (d) is sectional drawing of the microstructure layer comprised by a recessed part. It is sectional drawing when the organic EL element with the fine structure of this invention discharge | releases mixed light of 2 colors. It is sectional drawing when the conventional organic EL element discharge | releases mixed light of 2 colors. It is a graph showing the light extraction efficiency of four organic EL elements having different functions. It is a schematic cross section showing a mode that the light discharge | released from a light emitting layer is scattered in the conventional organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 101: Organic EL element 10: Transparent substrate 12: Fine structure layer 14: Convex part 16: Fluorescent dye 17: Fluorescent pigment 20: Transparent electrode (anode)
22: Light reflecting electrode (cathode)
24: Organic light emitting layer 26: Light emitting layer

Claims (15)

A transparent substrate having a microstructure layer on at least one of the surfaces;
A transparent electrode formed on the transparent substrate;
An organic light-emitting layer formed on the transparent electrode and including a light-emitting layer that emits light; and
Including
At least one of the microstructure layers is an organic EL element in which a fluorescent material is dispersed substantially uniformly in the microstructure. The organic EL device according to claim 1, wherein the fine structure layer includes a plurality of convex portions or concave portions. The organic EL element according to claim 2, wherein the shape of the convex portion or the concave portion includes a cone, a pyramid, a cylinder, a prism, a truncated cone, or a truncated pyramid. The organic EL element according to claim 1, wherein the transparent substrate and the fine structure layer have substantially the same refractive index. The organic EL element according to any one of claims 1 to 4, wherein the transparent substrate is a glass substrate, and the fine structure layer is formed of an organic-inorganic hybrid material. The organic EL element according to any one of claims 1 to 5, wherein a planarization layer is formed between the transparent substrate and the transparent electrode. The organic EL element according to claim 6, wherein a refractive index of the planarizing layer is substantially equal to a refractive index of the transparent electrode. The organic EL device according to claim 7, wherein the transparent electrode is made of IZO (Indium Zinc Oxide) or ITO (Indium Tin Oxide), and the planarizing layer includes a metal oxide of titanium. The organic EL device according to any one of claims 1 to 8, wherein the fluorescent material is a fluorescent dye or a fluorescent pigment. The organic EL device according to claim 9, wherein the fluorescent pigment is selected from organic dye laser materials. The organic EL device according to claim 10, wherein the fluorescent pigment is selected from cyanine dyes. The organic EL element according to any one of claims 1 to 11, wherein the fluorescent material that absorbs light emitted from the light emitting layer generates light having a wavelength longer than the wavelength of the light emitted. The organic EL device according to claim 12, wherein the light emitting layer emits green or blue light. The organic EL element according to claim 12 or 13, wherein the fluorescent materials that emit light of different wavelengths are dispersed in the fine structure layer formed on both surfaces of the transparent substrate. The organic EL element according to claim 14, wherein the combined light of the light emission of the light emitting layer and the light emitted from each of the fluorescent materials that has absorbed the light emission is white light.

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