JP2007080890A - Surface light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light emitting element which can improve the extraction efficiency of light. <P>SOLUTION: The surface light emitting element 10 is provided with a transparent substrate 11; and a first electrode 12, a light emitting layer 13 which emits a light by implanting holes and electrons, and a second electrode 14 that are formed in order on the transparent substrate 11. The first electrode 12 has a periodic structure in the perpendicular direction to the normal line of the transparent substrate 11 and it implants holes into the light emitting layer 13. A part of the light emitting layer 13 to which the holes are given has a periodic structure in the perpendicular direction to the normal line of the transparent substrate 11, so that the distribution of refractive index having a periodic structure is formed on the light emitting layer 13. The light emitting layer 13 forms diffractive grating by the refractive index distribution, and a light emitted from the light emitting layer 13 is diffracted in the direction of the transparent substrate 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface light emitting device such as an organic EL device or an inorganic EL device having a light emitting layer.

  Conventionally, various surface light emitting devices have been proposed. For example, a surface light emitting element using electroluminescence (EL) such as an organic EL element or an inorganic EL element emits light by applying voltage on a transparent electrode made of ITO (Indium Tin Oxide) formed on a glass substrate. A light emitting layer is formed. A back electrode made of aluminum or the like is formed on the light emitting layer.

  The light emitting layer is made of an organic compound or the like, and emits light by recombination of holes injected from the transparent electrode and electrons injected from the back electrode. The light emitted from the light emitting layer passes through the transparent electrode and the glass substrate and is emitted from the emission surface of the glass substrate. Part of the light is reflected by the back electrode, reaches the transparent electrode, and is emitted from the exit surface.

  In this surface light emitting device, light having an incident angle of a critical angle or less at the interface between the light emitting layer and the transparent electrode, the interface between the transparent electrode and the glass substrate, and the emission surface is totally reflected to become a waveguide mode. Waveguide is conducted in the transparent electrode and the glass substrate. For this reason, there is a problem that the amount of light emitted from the emission surface is small and the light extraction efficiency is low. In particular, the organic EL element is required to further improve the light extraction efficiency from the viewpoint of life and the like. Improvement of light extraction efficiency is a common problem required for other surface light emitting elements (for example, LEDs are also a kind of surface light emitting elements).

  In order to solve the above problem, Patent Document 1 discloses a surface light emitting element having a diffraction grating. In this surface light emitting device, the diffraction grating is provided at the boundary between the transparent electrode and the glass substrate or the boundary between the light emitting layer and the metal electrode. The light emitted from the light emitting layer is diffracted by the diffraction grating including the light in the waveguide mode, and the incident angle of the light reaching the exit surface of the glass substrate is changed to be larger than the critical angle. Thereby, the light totally reflected at the interface between the transparent electrode and the glass substrate and the emission surface can be reduced, and the light extraction efficiency can be improved.

Patent Document 2 discloses a surface light emitting device in which a substrate is provided with an uneven shape having a roof-shaped inclination, and a light emitting layer and an electrode are configured in parallel to the uneven shape of the substrate. In this surface light emitting element, light emitted from the light emitting layer and not directly directed to the exit surface direction can be reflected by the uneven shape and exit from the exit surface. Thereby, the light extraction efficiency can be improved.
Japanese Patent No. 2911183 (pages 5-7, FIG. 7) Japanese Patent No. 3584575 (5th page, FIG. 2)

  However, the surface light emitting device disclosed in Patent Document 1 includes a diffraction grating that diffracts light emitted from the light emitting layer in a direction that avoids total reflection, but the light emission position and the diffraction position are separated from each other. Therefore, the effect of diffraction is not great, and the light extraction efficiency is not greatly improved.

  Further, in the surface light emitting device disclosed in Patent Document 2, the corners of the uneven shape of the electrode and the light emitting layer are easily damaged because the charges injected into the light emitting layer are concentrated, and the lifetime of the device is shortened.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light emitting device that can further improve the light extraction efficiency and has little deterioration of the device due to charge concentration.

  To achieve the above object, the present invention comprises a substrate, a first electrode, a light emitting layer that emits light by injecting holes and electrons, and a second electrode, which are sequentially formed on the substrate. In the surface light emitting device, in a state where a voltage is applied to the first electrode and the second electrode and holes and electrons are injected into the light emitting layer, the light emitting layer is in a direction normal to the substrate. And a refractive index profile having a periodic structure in a perpendicular direction. According to this configuration, the light emitting layer forms a diffraction grating by the refractive index distribution in a state where a voltage is applied to at least the first electrode and the second electrode.

  The present invention also provides a surface light emitting device comprising a substrate, a first electrode formed in order on the substrate, a light emitting layer that emits light by injecting holes and electrons, and a second electrode. At least one of the first electrode and the second electrode has a periodic structure in a direction perpendicular to the normal direction of the substrate, and a voltage is applied to the first electrode and the second electrode. Then, by injecting holes and electrons into the light emitting layer, the light emitting layer has a refractive index distribution having a periodic structure similar to the periodic structure. According to this configuration, the light emitting layer forms a diffraction grating by the refractive index distribution in a state where a voltage is applied to the first electrode and the second electrode.

  According to the present invention, in the surface light emitting device having the above structure, the pitch of the periodic structure is 0.2 μm or more and 10 μm or less.

  According to the present invention, in the surface light emitting device having the above-described configuration, the periodic structure is two-dimensionally arranged.

  According to the present invention, in the surface light emitting device having the above structure, the light emitting layer is flat.

  According to the present invention, when a voltage is applied to at least the first electrode and the second electrode and the light emitting layer emits light, the light emitting layer has a refractive index distribution having a periodic structure, thereby forming a diffraction grating. . Accordingly, since the emitted light is diffracted in the direction of the transparent substrate without becoming a waveguide mode, the extraction efficiency of the emitted light can be improved.

  In addition, according to the present invention, since the pitch of the periodic structure is 0.2 μm or more and 10 μm or less, even when various types of light emitting materials are used, the emitted light can be easily diffracted in the direction of the transparent substrate 11. Become.

  In addition, according to the present invention, since the periodic structure is a two-dimensional arrangement, light in more directions can be extracted to the outside.

  Further, according to the present invention, since the light emitting layer is flat, the surfaces of the first electrode and the second electrode for injecting holes and electrons are also flat. Therefore, charges are not concentrated locally on the first electrode and the second electrode, so that the surface light emitting element can be hardly deteriorated.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. 1 is a front view of an organic EL element that is a surface light emitting element according to a first embodiment of the present invention, FIG. 2 is a perspective view of a transparent substrate and a first electrode, and FIG. 3 is a perspective view of the transparent substrate and the first electrode. It is a top view. Hereinafter, although the case where a surface light emitting element is an organic EL element is demonstrated, not only this but various surface emitting type light emitting elements may be sufficient. For example, the surface light emitting element may be an inorganic EL element or an LED.

  First, the configuration of the organic EL element 10 will be described. The organic EL element 10 has a first electrode 12 formed on a transparent substrate 11 made of a glass substrate with a two-dimensional period, and emits light on the surface of the transparent substrate 11 on which the first electrode 12 is formed. The layer 13 and the second electrode 14 are sequentially formed. The structures of the transparent substrate 11 and the first electrode 12 will be described later.

As the transparent substrate 11, a material such as glass or resin can be used as long as it is transparent. There are no particular limitations on the type of glass, plastic, and the like, but preferred examples include glass, quartz, and a transparent resin film. Particularly preferred is a resin film that can give flexibility to the organic EL element 10. The surface of the resin film may be formed with an inorganic film, an organic film, or a hybrid film of both, and is preferably a barrier film having a water vapor permeability of 0.01 g / m ² · day · atm or less. Furthermore, a high barrier film having an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻⁵ g / m ² / day or less is preferable.

  As a material for forming this barrier film, any material may be used as long as it has a function of suppressing intrusion of an element such as moisture or oxygen that causes deterioration of the element. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. . Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

  The method for forming this barrier film is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

As the electrode material of the first electrode 12 which is an anode, an electrically conductive compound having a large work function (4 eV or more) is preferably used. Specific examples of such an electrically conductive compound include conductive transparent materials such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), SnO ₂ and ZnO. The first electrode 12 forms a thin film on the transparent substrate 11 by a method such as vapor deposition or sputtering of these electrode materials, and forms a pattern having a desired shape by a technique such as photolithography. When the light emitted from the light emitting layer 13 is taken out from the first electrode 12, it is desirable that the transmittance be greater than 10%, and the sheet resistance is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

As the second electrode 14 serving as the cathode, an electrode material made of a metal having a low work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, or a mixture thereof is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. The second electrode 14 can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode of the second electrode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

  The light emitting layer 13 is made of an organic compound light emitting material such as Alq3 (Tris- (8-hydroxyquinoline) aluminum). The light-emitting layer 13 applies a voltage to the first electrode 12 and the second electrode 14, and is injected from the holes injected from the first electrode 12 that is the anode and the second electrode 14 that is the cathode. It is a layer that recombines with the coming electrons and emits phosphorescence or fluorescence, and the light emitting portion may be in the layer of the light emitting layer 13 or at the interface between the light emitting layer 13 and the adjacent layer.

  The light emitting layer 13 may be configured by stacking a plurality of organic layers separated in function, and other functions such as a charge injection layer, a charge transport layer, and a buffer layer between the light emitting layer 13 and each electrode. A layer may be provided.

  In recent years, since Princeton University has reported organic EL devices using phosphorescence emission from excited triplets (MA Baldo et al., Nature, 395, 151-154 (1998)), room temperature. In recent years, research on phosphorescent materials has been actively conducted (for example, MA Baldo et al., Nature, 403, 17, 750-753 (2000), US Pat. No. 6,097). No. 147, etc.). When an excited triplet is used, the upper limit of the internal quantum efficiency is 100%, so that in principle the emission efficiency is up to four times that of the excited singlet, and the emission efficiency can be significantly improved.

  The 10th International Workshop on Inorganic and Organic Electroluminescence (EL'00, Hamamatsu) reports several reports on phosphorescent compounds. For example, Ikai et al. Uses a hole transporting compound as a host of a phosphorescent compound. In addition, M.M. E. Thompson et al. Use various electron transporting materials as phosphorescent compound hosts doped with a novel iridium complex. Furthermore, Tsutsui et al. Have obtained high luminous efficiency by introducing a hole blocking layer.

  Examples of the host compound of the phosphorescent compound include C.I. Adachi et al. , Appl. Phys. Lett. 77, p. 904 (2000).

  Further, in a device having a light emitting layer each containing a phosphor compound as a host compound and a dopant compound, as an example of applying a carbazole derivative as the host compound, 4,4'-N, N'-dicarbazole-biphenyl (CBP) is the most common. As carbazole derivatives other than CBP, there are polymer types in JP-A Nos. 2001-257076, 2002-105445, etc., and 2001-331179, 2002-75645, etc., among others, carbazole having a specific structure. Derivatives are described.

  In these conventional compounds, there is a problem of a configuration capable of achieving both emission luminance and durability. In particular, for light emission shorter than green, the emission efficiency is lower than that of longer wavelength than green.

  Also in the light emitting layer 13 of the organic EL element 10 of the present invention, the following host compound and phosphorescent compound (also referred to as a phosphorescent compound) are preferably contained.

  Specific examples of known host compounds include compounds described in the following documents. JP 2001-257076 A, JP 2002-308855 A, 2001-313179 A, 2002-319491, 2001-357777, 2002-334786, 2002-8860 No. 2002-334787, No. 2002-15871, No. 2002-334788, No. 2002-43056, No. 2002-334789, No. 2002-75645, No. 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002 -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

The phosphorescent compound can be appropriately selected from known compounds used for the light emitting layer of the organic EL device, and preferably a complex system containing a metal of group 8 to group 10 in the periodic table of elements. Compounds, more preferably iridium compounds, osmium compounds, platinum compounds (platinum complex compounds), and rare earth complexes, and most preferred are iridium compounds.

  The light emitting layer 13 can be formed by forming the above compound by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, and an ink jet method.

  In the present invention, the light emitting layer 13 includes at least three layers having different emission spectra, each having a light emission maximum wavelength in the range of 430 to 480 nm, 510 to 550 nm, and 600 to 640 nm. A layer having an emission maximum wavelength of 430 to 480 nm is hereinafter referred to as a blue light emitting layer, a layer having a wavelength of 510 to 550 nm is referred to as a green light emitting layer, and a layer in the range of 600 to 640 nm is hereinafter referred to as a red light emitting layer. There is no restriction | limiting in particular as a lamination order of a light emitting layer, You may have a nonluminous intermediate | middle layer between each light emitting layer. In the present invention, it is preferable that at least one blue light emitting layer is provided at a position closest to the first electrode 12 in all the light emitting layers.

  Although there is no restriction | limiting in particular in the sum total of the film thickness of the light emitting layer 13, Usually, 2 nm-5 micrometers, Preferably it is chosen in the range of 2-200 nm. In the present invention, it is preferably in the range of 10 to 20 nm.

  The film thickness of each light emitting layer is preferably selected in the range of 2 to 100 nm, and more preferably in the range of 2 to 20 nm. Although there is no restriction | limiting in particular about the film thickness relationship of each light emitting layer of blue, green, and red, It is preferable that the blue light emitting layer (the sum total when there are two or more layers) is the thickest among three light emitting layers.

  Moreover, as a sealing means used for this invention, the method of adhere | attaching a sealing member (not shown) and the transparent substrate 11, the 1st electrode 12, and the 2nd electrode 14 with an adhesive agent, for example is mentioned. it can. The sealing member may be disposed so as to cover the display area of the organic EL element 10 and may be concave or flat. Further, transparency and electrical insulation are not particularly limited. Specific examples include a glass plate, a polymer plate / film, and a metal plate / film.

  The organic EL device 10 according to the present invention includes, for example, an anode / light-emitting layer unit / electron transport layer / cathode, anode / hole transport layer / light-emitting layer unit / electron transport layer, in addition to the above. / Consisting of cathode, anode / hole transporting layer / light emitting layer unit / hole blocking layer / electron transporting layer / consisting of cathode, anode / hole transporting layer / light emitting layer unit / hole blocking layer / electron transporting layer / Cathode buffer layer / made of cathode, anode / anode buffer layer / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode, It is not limited to these. Moreover, you may provide other layers, such as a positive hole injection layer, an intermediate | middle layer, an electron carrying layer, and an electron injection layer.

  Here, an injection layer, a blocking layer, an electron transport layer, and the like used as a constituent layer of the organic EL element of the present invention will be described.

  The injection layer is a layer provided between the electrode and the organic layer in order to lower the driving voltage and improve the light emission luminance, and is provided as necessary. There are an electron injection layer (cathode buffer layer) and a hole injection layer (anode buffer layer), as described above, between the anode and the light emitting layer or hole transport layer, and between the cathode and the light emitting layer or electron transport layer. You may let them.

  The anode buffer layer (hole injection layer) is a phthalocyanine buffer layer typified by copper phthalocyanine, an oxide buffer layer typified by vanadium oxide, an amorphous carbon buffer layer, or a conductive polymer such as polyaniline (emeraldine) or polythiophene. And a polymer buffer layer using

  The cathode buffer layer (electron injection layer) is a metal buffer layer typified by strontium or aluminum, an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, Examples thereof include an oxide buffer layer typified by aluminum oxide. The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

  As described above, the hole blocking (hole blocking) layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

  The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers. The hole transport material has either hole injection or transport and electron barrier properties, and may be either an organic substance or an inorganic substance. A porphyrin compound, an aromatic tertiary amine compound, and It is preferable to use a styrylamine compound, particularly an aromatic tertiary amine compound.

  The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  An electron transport material (also serving as a hole blocking material) used for the electron transport layer adjacent to the cathode side with respect to the light emitting layer may have a function of transmitting electrons injected from the cathode to the light emitting layer. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, thiadiazole derivatives, quinoxaline derivatives, etc. it can. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum. Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.

  The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

  Moreover, although what is called a bottom emission type is shown as an organic EL element in FIG. 1, a top emission type may be used.

  As shown in FIGS. 2 and 3, the first electrode 12 is provided with cylindrical protrusions 12a so as to form a square lattice. A first electrode 12 is embedded between the protrusions 12a, whereby the first electrode 12 is arranged with a two-dimensional period. Since the first electrode 12 is integrated without being divided as shown in FIG. 2, it can have the same potential.

  Next, a method for manufacturing the organic EL element 10 according to the first embodiment will be described. First, a resist that is a photosensitive resin is applied to the surface of the transparent substrate 11. The applied resist is subjected to resist patterning by interference exposure to produce a pattern in which circles are formed on the resist so as to form a square lattice. The transparent substrate 11 on which the resist pattern is formed is etched to a predetermined depth by dry etching to form cylindrical protrusions 12a having the same arrangement as the resist shape on the transparent substrate 11, and then the resist is removed from the transparent substrate 11 Peel off. Subsequently, ITO, which is the material of the first electrode 12, is formed on the surface of the transparent substrate 11 on which the projections 12a are formed by magnetron sputtering so that the gaps between the projections 12a are completely filled and the projections 12a are hidden. When the deposited ITO is polished until the protrusions 12a of the transparent substrate 11 are exposed, the structure shown in FIG. 2 is obtained. On the first electrode 12 where the protrusions 12a appear, Alq3 is vapor-deposited to form the light-emitting layer 13, and aluminum is vapor-deposited on the light-emitting layer 13 to form the second electrode 14. The organic EL element 10 Is completed.

  In the organic EL element 10 thus obtained, when a voltage is applied to the first electrode 12 and the second electrode 14, a portion where holes from the first electrode 12 are not injected into the light emitting layer 13 is Appears in a cylindrical shape arranged to form a square lattice. When the hole or electron is injected into the light emitting layer 13, the refractive index changes by about 0.1% in the case of Alq3. Therefore, in the organic EL element 10 to which a voltage is applied, the light emitting layer 13 has a periodic lattice periodic structure. A refractive index profile is formed. That is, when the voltage is applied to the first electrode 12 and the second electrode 14, the light emitting layer 13 becomes a diffraction grating.

  By applying a voltage to the first electrode 12 and the second electrode 14 of the organic EL element 10, the holes injected from the first electrode 12 and the electrons injected from the second electrode 14 are recombined. The emitted light is diffracted in the direction of the transparent substrate 11 by the diffraction grating simultaneously with the light emission, and is taken out of the organic EL element 10 through the transparent substrate 11. Further, part of the light diffracted to the second electrode 14 side is also reflected by the second electrode 14 and taken out of the organic EL element 10 through the transparent substrate 11. Accordingly, the extraction efficiency of the emitted light is improved as compared with the case where the first electrode 12 is not formed with a two-dimensional periodic structure. In addition, the first electrode 12, the second electrode 14, and the light emitting layer 13 are flat, have no corners, and do not concentrate electrons and holes. The lifetime as a whole can be extended.

  In the first embodiment, Alq3 having a refractive index of 1.8 and an emission wavelength of about 520 nm is used as the light emitting layer 13. Since light having a wavelength of 520 nm has a wavelength in Alq3 of 520 ÷ 1.8≈289 nm, if the pitch a of the square lattice shown in FIG. 3 is set to a value around 289 nm, for example, 300 nm, Alq3 is used. The extraction efficiency of the light emitted from the light emitting layer 13 can be improved.

  In the first embodiment, the arrangement of the protrusions 12a of the first electrode 12 may be a triangular lattice as shown in FIG. In this case, the extraction efficiency of light emitted from the light emitting layer 13 using Alq3 can be improved by setting the pitch b of the triangular lattice to about 300 nm. Note that the arrangement of the protrusions 12a of the first electrode 12 is not limited to a square lattice or a triangular lattice, and may be an oblique lattice, a rectangular lattice, or the like as long as it has a two-dimensional periodic structure. Further, the periodic structure may be one-dimensional, for example, the protrusion 12a of the first electrode 12 may be a rod shape extending in one direction, and the diffraction grating formed on the light emitting layer 13 may be a stripe shape.

  When a light emitting material other than Alq3 is used for the light emitting layer 13, when the wavelength of light emitted from the light emitting layer 13 is λ and the refractive index is n, the pitch of the diffraction grating formed by the light emitting layer 13 By setting d to d≈λ / n, the light extraction efficiency of the light emitting layer 13 can be improved. For example, by setting the pitch d to 0.2 μm or more and 10 μm, it is possible to easily diffract the emitted light in the direction of the transparent substrate 11 even when various kinds of light emitting materials are used.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a front view of an organic EL element which is a surface light emitting element according to the second embodiment, and FIG. 6 is a perspective view of the second electrode and the insulator turned upside down. The second embodiment is the same as the first embodiment except that the second electrode has a two-dimensional periodic structure, not the first electrode, and is substantially the same. Are given the same reference numerals.

  In the second embodiment, in the organic EL element 10, a first electrode 12 and a light emitting layer 13 are sequentially formed on a transparent substrate 11. The insulator 15 is disposed on the light emitting layer 13 so as to form a square lattice, and the second electrode 14 is formed on the light emitting layer 13 and the insulator 15. Therefore, the second electrode 14 has a two-dimensional periodic structure.

    Next, a manufacturing method of the organic EL element 10 according to the second embodiment will be described. First, a first electrode 12 made of ITO is formed on a transparent substrate 11 by magnetron sputtering, and Alq3 is vapor-deposited thereon to form a light emitting layer 13. On this light emitting layer 13, an insulator 15 made of PMMA (polymethyl methacrylate) in a disk shape by ink jet is arranged so as to form a square lattice. On the light emitting layer 13 on which the insulator 15 is disposed, aluminum is vapor-deposited to form a second electrode, and the organic EL element 10 is completed.

  When a voltage is applied to the first electrode 12 and the second electrode 14 in the organic EL element 10 thus obtained, a portion where electrons from the second electrode 14 are not injected into the light emitting layer 13 is square. Appears in a cylindrical shape arranged in a lattice. Therefore, as in the first embodiment, in the organic EL element 10 to which a voltage is applied, a refractive index distribution having a periodic structure of a square lattice is formed in the light emitting layer 13, and the light emitting layer 13 becomes a diffraction grating.

  Also in the second embodiment, when Alq3 is used as the light emitting layer 13, the extraction efficiency of light emitted from the light emitting layer can be improved by setting the pitch of the square lattice formed by the insulator 15 to about 300 nm. Can do. Further, when the insulator 15 forms a triangular lattice, the extraction efficiency of light emitted from the light emitting layer 13 can be improved by setting the pitch to about 300 nm as in the first embodiment.

  Further, in the second embodiment, similarly to the first embodiment, the transparent substrate 11 may be provided with the protrusions 11a, and the first electrodes 12 may be periodically arranged. In this case, the protrusion 11a is provided at a position facing the insulator 15 with the light emitting layer 13 interposed therebetween.

  The present invention can be used for surface light emitting devices such as organic EL devices, inorganic EL devices, and LEDs.

1 is a front view of an organic EL element which is a surface light emitting element according to a first embodiment of the present invention. The perspective view of the transparent substrate and 1st electrode which concern on the 1st Embodiment of this invention The top view of the transparent substrate and 1st electrode which concern on the 1st Embodiment of this invention The top view of the transparent substrate and 1st electrode which concern on another aspect of the 1st Embodiment of this invention The front view of the organic electroluminescent element which is a surface emitting element which concerns on the 2nd Embodiment of this invention. The perspective view of the state which turned over the 2nd electrode and insulator which concern on the 2nd Embodiment of this invention

Explanation of symbols

10 Organic EL device (Surface emitting device)
DESCRIPTION OF SYMBOLS 11 Transparent substrate 12 1st electrode 13 Light emitting layer 14 2nd electrode 15 Insulator

Claims (5)

In a surface light emitting device including a substrate, a first electrode, a light emitting layer that emits light by injecting holes and electrons, and a second electrode, which are sequentially formed on the substrate,
In a state where a voltage is applied to the first electrode and the second electrode and holes and electrons are injected into the light emitting layer, the light emitting layer is in a direction perpendicular to the normal direction of the substrate. A surface light emitting device having a refractive index distribution having a periodic structure. In a surface light emitting device including a substrate, a first electrode, a light emitting layer that emits light by injecting holes and electrons, and a second electrode, which are sequentially formed on the substrate,
At least one of the first electrode and the second electrode has a periodic structure in a direction perpendicular to the normal direction of the substrate, and a voltage is applied to the first electrode and the second electrode Then, by injecting holes and electrons into the light emitting layer, the light emitting layer has a refractive index distribution having a periodic structure similar to the periodic structure.   The surface light-emitting element according to claim 1, wherein a pitch of the periodic structure is 0.2 μm or more and 10 μm or less.   The surface light emitting device according to claim 1, wherein the periodic structure has a two-dimensional arrangement.   The surface light emitting device according to claim 1, wherein the light emitting layer is flat.

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