JP5452691B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light emitting device.

  Conventionally, light emitting devices using organic electroluminescence elements (hereinafter abbreviated as organic EL elements) have been researched and developed in various places.

  As an organic EL element, for example, a transparent electrode serving as an anode, a hole transport layer, a light emitting layer (organic light emitting layer), an electron injection layer, and an electrode serving as a cathode are formed on one surface side of a translucent substrate (transparent substrate). Those having a laminated structure of are known. In this type of organic EL element, light emitted from the light emitting layer by applying a voltage between the anode and the cathode is taken out through the transparent electrode and the translucent substrate.

  The organic EL element is a self-luminous light emitting element, has a relatively high light emission characteristic, and can emit light in various colors, and has a feature such as a display device (for example, Applications such as light emitters such as flat panel displays) and light sources (for example, backlights of liquid crystal display devices and illumination light sources) are expected, and some have already been put into practical use.

  However, in order to apply and deploy organic EL elements for these uses, development of organic EL elements with higher efficiency, longer life, and higher brightness is desired.

  There are mainly three factors that govern the efficiency of the organic EL element: electro-optical conversion efficiency, drive voltage, and light extraction efficiency.

  Regarding the electro-optical conversion efficiency, it has been reported that a phosphorescent material is used as the material of the light emitting layer, so that the external quantum efficiency exceeds 20%. The value of 20% for the external quantum efficiency is considered to be about 100% when converted to the internal quantum efficiency. From the viewpoint of electro-optical conversion efficiency, it can be said that an example of reaching a so-called limit value has been experimentally confirmed. . Further, with respect to the driving voltage, an organic EL element that emits light with relatively high luminance at a voltage about 10 to 20% higher than the voltage corresponding to the energy gap of the light emitting layer has been obtained. Therefore, the improvement in the efficiency of the organic EL element due to the improvement of these two factors (electric-light conversion efficiency, drive voltage) cannot be expected so much.

  On the other hand, the light extraction efficiency of the organic EL element is generally said to be about 20 to 30% (this value varies somewhat depending on the light emission pattern and the layer structure between the anode and the cathode). The light extraction efficiency depends on the total reflection at the interface between the materials with different refractive indexes and the light generated by the materials because the materials that make up the light generating part and the surrounding parts have characteristics such as high refractive index and light absorption. It is considered that the above value is low because light cannot be effectively propagated to the outside world on the side where light emission is observed due to absorption of light. That is, the light extraction efficiency of 20 to 30% means that light that cannot be effectively utilized as so-called light emission accounts for 70 to 80% of the total light emission amount, and the efficiency of the organic EL element due to the improvement of the light extraction efficiency The expected value of improvement is very large.

  By the way, there has been proposed an organic EL device in which a light scattering portion made of a lens sheet is provided on the other surface side (light extraction surface side) of a light-transmitting substrate made of a glass substrate having an organic EL element formed on one surface side. (Patent Document 1). In Patent Document 1, the light scattering portion that comes into contact with air relaxes the reflection or total reflection that occurs on the light extraction surface, and the light scattering portion has a property that it does not absorb light essentially. It is described that can be improved.

Japanese Patent No. 2931111

  In the light emitting device in which the light scattering portion is provided on the other surface of the translucent substrate like the organic EL device disclosed in Patent Document 1, the light extraction efficiency can be improved. The surface is easily scratched, and there is a concern that the optical characteristics may change, and there is a problem in reliability.

  Patent Document 1 also discloses a light-emitting device having a structure in which a glass plate is bonded to an uneven surface side of a light scattering portion provided on the other surface side of a translucent substrate with an epoxy adhesive. .

  However, in an organic EL device having a structure in which a light scattering portion and a glass plate are bonded together with an epoxy adhesive, light extraction efficiency is reduced as compared with a device in which the glass plate is not bonded.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a light-emitting device that can improve light extraction efficiency and reliability.

The light-emitting device of the present invention includes a light-transmitting substrate, an organic EL element having an organic EL layer including a light-emitting layer formed on one surface side of the light-transmitting substrate and interposed between an anode and a cathode; A light emitting device provided on the other surface side of the translucent substrate and having a concavo-convex structure portion for suppressing reflection of light emitted from the organic EL element on the other surface of the translucent substrate, The package substrate which is disposed on the other surface side and at least part of which is formed of a translucent material, covers the side of the organic EL element opposite to the translucent substrate side, and moisture reaches the organic EL element. The package substrate is made of a glass substrate, the translucent substrate is made of a plastic substrate, and the protection portion is an inorganic material thin film or an inorganic material thin film stack. Composed of a membrane and said anode Each of the cathodes is formed to extend to a portion that does not overlap the light emitting layer, and a part of the extended portion is exposed without being covered by the protective portion, and the exposed portion is a pad. The protective part is formed so as to cover a side edge of the light-transmitting substrate and a side edge of a joint part that joins the light-transmitting substrate and the package substrate. To do.

  In the present invention, there are effects that the light extraction efficiency can be improved and the reliability can be improved.

1 is a schematic cross-sectional view of a light emitting device according to Embodiment 1. FIG. It is a principal part schematic plan view same as the above. It is explanatory drawing of the structural example of the uneven structure part same as the above. It is a principal part schematic plan view of the other structural example same as the above. It is a schematic perspective view of the other structural example of the uneven structure part same as the above. It is a schematic perspective view of another structural example of the uneven structure part same as the above. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 2. FIG. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 3. FIG. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 4. FIG. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 5. FIG. It is a principal part schematic plan view of a light-emitting device same as the above. 7 is a schematic cross-sectional view of a light emitting device according to Embodiment 6. FIG.

(Embodiment 1)
Hereinafter, the light emitting device of this embodiment will be described with reference to FIG.

  The light emitting device of the present embodiment includes a translucent substrate 10, an organic EL element 20 formed on one surface side of the translucent substrate 10, and an organic EL element 20 provided on the other surface side of the translucent substrate 10. And the concavo-convex structure portion 30 that suppresses reflection of the light emitted from the other surface. The light emitting device of this embodiment covers the opposite side of the organic EL element 20 from the side of the transparent substrate 10 and the organic EL element 20 on the other surface side of the transparent substrate 10. And a protection unit 50 that prevents moisture from reaching 20. Furthermore, the light emitting device according to the present embodiment includes a spacer 60 that is interposed between the translucent substrate 10 and the package substrate 40 and maintains the distance between the translucent substrate 10 and the package substrate 40 at a predetermined distance. And a space 70 exists between the concavo-convex structure portion 30 and the package substrate 40.

  The translucent substrate 10 is a polyethylene terephthalate that is a kind of plastic substrate that is cheaper than an inexpensive glass substrate such as an alkali-free glass substrate or a soda-lime glass substrate and has a higher refractive index than the glass substrate. A tarato (PET) substrate is used. The plastic material of the plastic substrate is not limited to PET, and for example, polyethylene naphthalate (PEN), polyethersulfone (PES), polycarbonate (PC), and the like may be adopted. What is necessary is just to select suitably according to heat-resistant temperature etc. The translucent substrate 10 is not limited to a plastic substrate, and may be a glass substrate such as the above-described non-alkali glass substrate, soda lime glass substrate, or high refractive index glass substrate.

  However, when a glass substrate is used as the translucent substrate 10, the unevenness on the one surface of the translucent substrate 10 may cause a leakage current of the organic EL element 20 (the organic EL element 20). May cause deterioration). For this reason, when a glass substrate is used as the translucent substrate 10, it is necessary to prepare a glass substrate for forming an element that is polished with high precision so that the surface roughness of the one surface is reduced, and the cost is reduced. It will be high. In addition, about the surface roughness of the said one surface of the translucent board | substrate 10, it is preferable to make arithmetic mean roughness Ra prescribed | regulated by JISB0601-2001 (ISO 4287-1997) below several nm.

  On the other hand, if a plastic substrate is used as the translucent substrate 10, it is possible to obtain a substrate having an arithmetic average roughness Ra of several nanometers or less at a low cost without performing particularly high-precision polishing. There is an advantage that you can.

  The translucent substrate 10 has a translucent material (for example, a glass material such as the above-described plastic material, alkali-free glass, or soda lime glass) at least partially (a portion that overlaps the light emitting region of the organic EL element 20). It is sufficient if it is formed by.

  Moreover, although the planar view shape of the translucent board | substrate 10 is made into the rectangular shape, it is not restricted to a rectangular shape, For example, circular shape, triangular shape, pentagon shape, hexagonal shape, etc. may be sufficient.

  In the organic EL element 20, the organic EL layer 23 interposed between the anode 22 and the cathode 24 includes a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer in this order from the anode 22 side. Here, in the organic EL element 20, the anode 22 is laminated on the one surface side of the translucent substrate 10, and the cathode 24 faces the anode 22 on the side opposite to the translucent substrate 10 side of the anode 22. doing.

  In the organic EL element 20, the anode 22 is formed of a transparent electrode and the cathode 24 is formed of an electrode that reflects light from the light emitting layer. The cathode 24 is formed of a transparent electrode and the anode 24 is formed of a light emitting layer. The electrode may be configured to reflect light, and the positional relationship between the cathode 24 and the anode 22 may be reversed. In short, in the organic EL element 20, the first electrode composed of one of the two electrodes of the anode 22 and the cathode 24 is formed on the translucent substrate 10, and the second electrode composed of the other electrode. First, it is only necessary to face the electrode.

  The stacked structure of the organic EL layer 23 is not limited to the above-described example, and for example, a single layer structure of a light emitting layer, a stacked structure of a hole transport layer, a light emitting layer, and an electron transport layer, a hole transport layer, and a light emitting layer. Or a stacked structure of a light emitting layer and an electron transport layer. A hole injection layer may be interposed between the anode and the hole transport layer. Further, the light emitting layer may have a single layer structure or a multilayer structure. For example, when the desired light emission color is white, the light emission layer may be doped with three types of dopant dyes of red, green, and blue. Alternatively, a laminated structure of a blue hole transporting light emitting layer, a green electron transporting light emitting layer and a red electron transporting light emitting layer may be adopted, or a blue electron transporting light emitting layer and a green electron transporting light emitting layer may be employed. A laminated structure with a red electron transporting light emitting layer may be adopted.

  The anode 22 is an electrode for injecting holes into the light emitting layer, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function, and HOMO (Highest Occupied Molecular). Orbital) It is preferable to use a work function of 4 eV or more and 6 eV or less so that the difference from the level does not become too large. Examples of the electrode material for the anode 22 include ITO, IZO, tin oxide, and zinc oxide, conductive polymers such as PEDOT and polyaniline, and conductive polymers doped with any acceptor, and conductive light such as carbon nanotubes. Mention may be made of permeable materials. Here, the anode 22 may be formed as a thin film on the one surface side of the translucent substrate 10 by a sputtering method, a vacuum evaporation method, a coating method, or the like.

  The sheet resistance of the anode 22 is preferably several hundred Ω / □ or less, particularly preferably 100 Ω / □ or less. Here, the film thickness of the anode 22 varies depending on the light transmittance of the anode 22, sheet resistance, and the like, but is set to 500 nm or less, preferably in the range of 10 nm to 200 nm.

  The cathode 24 is an electrode for injecting electrons into the light emitting layer, and 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 LUMO (Lowest Unoccupied It is preferable to use a material having a work function of 1.9 eV or more and 5 eV or less so that the difference from the molecular orbital level does not become too large. Examples of the electrode material of the cathode 24 include aluminum, silver, magnesium, and alloys of these with other metals, such as magnesium-silver mixtures, magnesium-indium mixtures, and aluminum-lithium alloys. Also, a metal conductive material, a metal oxide, etc., and a mixture of these and other metals, for example, an ultrathin film made of aluminum oxide (here, a thin film of 1 nm or less capable of flowing electrons by tunnel injection) A laminated film with a thin film made of aluminum can also be used. Moreover, when taking out light from the cathode 24 side, ITO, IZO, etc. should just be employ | adopted, for example.

  As a material for the light emitting layer, any material known as a material for an 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, 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, distili And amine derivatives, and various fluorescent pigments, but include those including a material system and its derivatives described above, not limited to these. In addition, it is also preferable to use a mixture of light emitting materials selected from these compounds as appropriate. Further, not only a compound that emits fluorescence, typified by the above compound, but also a material system that emits light from a spin multiplet, for example, a phosphorescent material that emits phosphorescence, and a part thereof are included in a part of the molecule. A compound can also be used suitably. The light emitting layer made of these materials may be formed by a dry process such as vapor deposition or transfer, or by a wet process such as spin coating, spray coating, die coating, or gravure printing. You may do.

  The material used for the hole injection layer can be formed using a hole injection organic material, a metal oxide, a so-called acceptor organic material or inorganic material, a p-doped layer, or the like. Examples of the hole injecting organic material include a material having a hole transport property, a work function of about 5.0 to 6.0 eV, and a strong adhesion to the anode 22, for example. Examples thereof include CuPc and starburst amine. The hole-injecting metal oxide is a metal oxide containing any of molybdenum, rhenium, tungsten, vanadium, zinc, indium, tin, gallium, titanium, and aluminum, for example. In addition, an oxide of a plurality of metals containing any one of the above metals, such as indium and tin, indium and zinc, aluminum and gallium, gallium and zinc, titanium and niobium, etc. It may be. The hole injection layer made of these materials may be formed by a dry process such as vapor deposition or transfer, or by a wet process such as spin coating, spray coating, die coating, or gravure printing. It may be a film.

  The material used for the hole transport layer can be selected from, for example, a group of compounds having hole transport properties. Examples of this type of compound include 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), N, N′-bis (3-methylphenyl)-(1 , 1′-biphenyl) -4,4′-diamine (TPD), 2-TNATA, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA) 4,4′-N, N′-dicarbazole biphenyl (CBP), spiro-NPD, spiro-TPD, spiro-TAD, TNB, and the like, arylamine compounds, amine compounds containing a carbazole group, An amine compound containing a fluorene derivative can be exemplified, and any generally known hole transporting material can be used.

The material used for the electron transport layer can be 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 Alq ₃ and compounds having a heterocyclic ring such as phenanthroline derivatives, pyridine derivatives, tetrazine derivatives, and oxadiazole derivatives. Instead, any generally known electron transport material can be used.

The material of the electron injection layer is, for example, a metal fluoride such as lithium fluoride or magnesium fluoride, a metal halide such as sodium chloride or magnesium chloride, aluminum, cobalt, zirconium, Titanium, vanadium, niobium, chromium, tantalum, tungsten, manganese, molybdenum, ruthenium, iron, nickel, copper, gallium, zinc, Si, and other metal oxides, nitrides, carbides, oxynitrides, etc., for example, oxidation Any insulating material such as aluminum, magnesium oxide, iron oxide, aluminum nitride, silicon nitride, silicon carbide, silicon oxynitride, boron nitride, silicon compounds including SiO ₂ and SiO, carbon compounds, etc. It can be selected and used. These materials can be formed into a thin film by being formed by a vacuum deposition method or a sputtering method.

  As the package substrate 40, an alkali-free glass substrate which is a cheaper glass substrate than a high refractive index glass substrate is used. However, the present invention is not limited to this, and for example, a soda lime glass substrate may be used. Moreover, since the glass substrate used for the package substrate 40 is not for forming the organic EL element 20, a glass substrate having an arithmetic average roughness Ra of several hundred nm or more can be used.

  The translucent substrate 10 on which the organic EL element 20 is formed is bonded to the package substrate 40 over the entire circumference of the translucent substrate 10. Here, the joint portion 29 that joins the translucent substrate 10 and the package substrate 40 is, for example, an adhesive film, a thermosetting resin, an ultraviolet curable resin, an adhesive (for example, an epoxy resin, an acrylic resin, a silicone resin, or the like). ) Or the like.

  Further, the protection unit 50 is composed of a SiN film. An organic material such as an epoxy resin or a silicone resin may be used as the material of the protection unit 50, but it is preferable to use an inorganic material in order to improve moisture resistance. Therefore, the protection unit 50 is preferably formed of a thin film such as a silicon nitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum nitride film, or a laminated film of these thin films.

  However, the organic EL element 20 is formed by extending the anode 22 and the cathode 24 to a portion that does not overlap the light emitting layer on the one surface of the translucent substrate 10, and a part of these extended portions is formed. It is exposed without being covered by the protection unit 50, and the exposed portions constitute the pads 122 and 124. Note that the pad 122 and the anode 22, and the pad 124 and the cathode 24 are not limited to the same material, but may be formed of different materials.

  By the way, in the light emitting device of the present embodiment, the space 70 exists between the concavo-convex structure portion 30 provided on the other surface side of the translucent substrate 10 and the package substrate 40 as described above.

  By the way, the refractive index of each of the light emitting layer of the organic EL element 20 and the translucent substrate 10 is larger than the refractive index of air that is an external atmosphere from which light is extracted. Therefore, when the space between the translucent substrate 10 and the package substrate 40 is an air atmosphere without the above-described uneven structure portion 30 being provided, the first medium made of the translucent substrate 10 is used. Total reflection occurs at the interface between the air and the second medium made of air, and light incident on the interface is reflected at an angle greater than the total reflection angle. Then, the light reflected at the interface between the first medium and the second medium is multiple-reflected inside the organic EL layer 23 or the translucent substrate 10 and attenuated without being extracted outside, so that the light extraction efficiency is lowered. To do. Also, light extraction efficiency is further reduced because Fresnel reflection occurs for light incident on the interface between the first medium and the second medium at an angle less than the total reflection angle.

  On the other hand, in this embodiment, since the above-mentioned concavo-convex structure part 30 is provided in the above-mentioned other surface side of translucent substrate 10 which forms organic EL element 20 in the above-mentioned one surface side, The light extraction efficiency to the outside of the organic EL device configured with the translucent substrate 10 can be improved.

  As shown in FIGS. 1 and 2, the concavo-convex structure portion 30 has a two-dimensional periodic structure in which a large number of protrusions 31 are periodically arranged in a two-dimensional plane parallel to the one surface of the translucent substrate 10. have.

  In the example shown in FIG. 2, the protrusion 31 has a quadrangular pyramid shape, but the shape of the protrusion 31 is not limited to the quadrangular pyramid shape as shown in FIG. 2 and FIG. 3A, and FIG. May be a triangular pyramid shape as shown in FIG. 3, a hexagonal pyramid shape as shown in FIG. 3C, or a conical shape as shown in FIG. 3D (in FIG. 3D, they are adjacent to each other). The projections 31 are connected to each other, and the boundary between the projections 31 in a plan view is a straight line). In short, the protrusion 31 may have a cone shape other than the quadrangular pyramid shape. Further, the protrusion 31 may be hemispherical.

  Further, the period P of the two-dimensional periodic structure indicates that the wavelength in the medium is λ (the wavelength in vacuum is divided by the refractive index of the medium when the wavelength of light emitted from the light emitting layer is in the range of 300 to 800 nm. Value), it is desirable to set appropriately within a range of 1/4 to 10 times the wavelength λ.

  When the period P is set in the range of 5λ to 10λ, for example, the light extraction efficiency is improved by the geometrical optical effect, that is, the area of the surface where the incident angle is less than the total reflection angle. Further, when the period P is set in a range of λ to 5λ, for example, the light extraction efficiency is improved by the action of extracting light having a total reflection angle or more by diffracted light. In addition, when the period P is set in the range of λ / 4 to λ, the effective refractive index near the concavo-convex structure portion 30 gradually decreases as the distance from the one surface of the translucent substrate 10 increases. It is equivalent to interposing a thin film layer having a refractive index intermediate between the refractive index of the medium of the concavo-convex structure portion 30 and the refractive index of the medium of the space 70 between the translucent substrate 10 and the space 70, It becomes possible to reduce Fresnel reflection. In short, if the period P is set in a range of λ / 4 to 10λ, reflection (total reflection or Fresnel reflection) can be suppressed, and light extraction efficiency is improved. However, the upper limit of the period P for improving the light extraction efficiency by the geometric optical effect is applicable up to 1000λ. In addition, the concavo-convex structure portion 30 does not necessarily have a periodic structure such as a two-dimensional periodic structure, and the light extraction efficiency can be improved even in a concavo-convex structure with a random concavo-convex size or a non-periodic concavo-convex structure. When uneven structures of different sizes coexist (for example, an uneven structure with a period P of 1λ and an uneven structure of 5λ or more coexist), the unevenness with the largest occupation ratio in the uneven structure portion 30 among them. The light extraction effect of the structure becomes dominant. Also, as for the shapes of the many protrusions 31, a plurality of types of shapes may be mixed. For example, as shown in FIG. 4, a hexagonal pyramidal protrusion 31 (31a) and a conical protrusion 31 (31b). ) May be mixed.

  The concavo-convex structure portion 30 is configured by a prism sheet (for example, a light diffusion film such as LIGHTUP (registered trademark) GM3 manufactured by Kimoto Co., Ltd.), but is not limited thereto. For example, the concavo-convex structure 30 may be formed on the other surface of the translucent substrate 10 by an imprint method (nanoimprint method), or the translucent substrate 10 may be formed by injection molding, and an appropriate mold Alternatively, the concavo-convex structure portion 30 may be directly formed on the translucent substrate 10.

  Here, an example of a method for forming the concavo-convex structure portion 30 by the imprint method will be briefly described.

  First, on the other surface of the translucent substrate 10 made of a PET substrate, from a high refractive index transparent material (for example, a thermosetting resin in which titanium oxide nanoparticles are mixed), which is the basis of the concavo-convex structure portion 30. A transfer layer to be formed is formed by spin coating. Next, the mold having a concavo-convex pattern designed according to the shape of the concavo-convex structure portion 30 is pressed against the transfer layer to deform and harden the transfer layer (for example, thermosetting), thereby forming the concavo-convex structure portion 30. Then, the mold is separated from the concavo-convex structure portion 30. Here, as the mold, for example, a Ni mold in which microscopic projections having a period of 2 μm and a height of 2 μm (for example, a quadrangular pyramid or a cone) are patterned in a two-dimensional array may be used.

  The imprinting method is not limited to the thermal imprinting method (thermal nanoimprinting method) using a thermosetting resin as a transparent material for the transfer layer as described above. A printing method (photo nanoimprint method) may be adopted. In this case, the transfer layer made of a low-viscosity photocurable resin layer is deformed by a mold, and thereafter, the photocurable resin is cured by irradiating with ultraviolet rays so that the mold is separated from the transfer layer. . In the imprint method, if the mold for molding is made once, the concavo-convex structure portion 30 can be formed with good reproducibility, and the cost can be reduced.

  In the light emitting device of this embodiment, it is important that a space 70 exists between the surface (uneven surface) of the uneven structure portion 30 and the package substrate 40. If the surface of the concavo-convex structure portion 30 is an interface between the concavo-convex structure portion 30 and the package substrate 40, there is a refractive index interface between the package substrate 40 and external air. Then, total reflection occurs again. On the other hand, since the light of the organic EL element 20 can be once extracted into the space 70, the interface between the air that is the medium of the space 70 and the package substrate 40, and the interface between the package substrate 40 and external air. Thus, total reflection loss does not occur.

  By the way, in the light emitting device of the present embodiment, each projection 31 of the concavo-convex structure portion 30 is interposed between the translucent substrate 10 and the package substrate 40, and between the translucent substrate 10 and the package substrate 40. This also serves as a spacer 60 for keeping the distance at a predetermined distance.

  In the light emitting device of the present embodiment described above, the package substrate 40 which is disposed on the other surface side of the translucent substrate 10 and at least part of which is formed of a translucent material, and the translucency in the organic EL element 20 are used. Since the protective portion 50 that covers the side opposite to the substrate 10 side and prevents moisture from reaching the organic EL element 20 is provided, a plastic having a high refractive index glass substrate or a barrier layer provided as the translucent substrate 10 Water resistance and moisture resistance can be improved without using a substrate.

  In the light emitting device of this embodiment, the spacer 60 is interposed between the translucent substrate 10 and the package substrate 40 and maintains the distance between the translucent substrate 10 and the package substrate 40 at a predetermined distance. And there is a space 70 between the concavo-convex structure portion 30 and the package substrate 40, so that the total reflection loss of the light emitted from the organic EL element 20 and reaching the package substrate 40 can be reduced, and the concavo-convex structure The light extraction efficiency can be improved as compared with the case where the space 70 does not exist between the portion 30 and the package substrate 40. Moreover, the light emitting device according to the present embodiment includes the spacer 60 that is interposed between the translucent substrate 10 and the package substrate 40 and maintains the distance between the translucent substrate 10 and the package substrate 40 at a predetermined distance. As a result, the concave-convex structure portion 30 can be prevented from being damaged, and the distance between the translucent substrate 10 and the package substrate 40 can be maintained at a predetermined distance, so that the translucent substrate 10 bends. Can be prevented, optical characteristics can be stabilized, and reliability can be improved. Here, if the protrusions 31 are periodically arranged in the concavo-convex structure portion 30, the distance between the translucent substrate 10 and the package substrate 40 can be kept more stably at a predetermined distance. Further, by forming the protrusions 31 of the concavo-convex structure portion 30 in a conical or hemispherical shape and reducing the contact area between the protrusions 31 also used as the spacers 60 and the package substrate 40, the light extraction efficiency can be improved. . On the other hand, with respect to the concavo-convex structure portion 30, as shown in FIG. 5, a large number of concave portions 32 constituting the concavo-convex structure portion 30 are conical (in the illustrated example, a quadrangular pyramid shape. In the case where a plurality of concave portions 31 constituting the concave-convex structure portion 30 are formed in the hemispherical concave portion 32 as shown in FIG. In either case, the portion 33 between the adjacent recesses 32 constitutes the spacer 60, and the portion 33 is brought into surface contact with the package substrate 40, whereby the distance between the translucent substrate 10 and the package substrate 40 is increased. The predetermined distance can be maintained more stably. Here, the part 33 and the package substrate 40 may be fixed by an adhesive or the like. However, in the structure of the concavo-convex structure portion 30 in FIGS. 5 and 6, it is preferable that the area of the portion 33 between the adjacent recesses 32 is not excessively large in order to suppress a decrease in light extraction efficiency.

  In addition, the light emitting device of the present embodiment includes a large number of spacers 60, and each spacer 60 can improve the light extraction efficiency and can be manufactured as compared with the case where the spacers 60 and the concavo-convex structure portion 30 are separate. Becomes easier.

  Further, in the light emitting device of this embodiment, if a plastic substrate is employed as the light transmissive substrate 10, the light transmissive substrate 10 is refracted as compared with a general glass substrate such as a soda lime glass substrate or an alkali-free glass substrate. Since a thing with a high rate can be used, the total reflection loss in the interface of the organic EL element 20 and the translucent board | substrate 10 can be reduced. Further, the cost can be reduced as compared with the case where a glass substrate is used as the translucent substrate 10.

  In the light emitting device of the present embodiment, the atmosphere of the space 70 described above is an air atmosphere, but the space 70 is selected from the group of vacuum, inert gas (for example, argon gas), nitrogen gas, and dry air. If one atmosphere is set, the arrival of moisture to the organic EL element 20 can be more reliably suppressed and the reliability is improved as compared with the case of an air atmosphere.

  Further, in the light emitting device of this embodiment, a plastic substrate without a barrier layer is used as the translucent substrate 10, and a glass substrate such as a soda lime glass substrate or a non-alkali glass substrate is used as the package substrate 40. Therefore, it is possible to reduce the cost and to prevent the long-term reliability of the organic EL element 20 from being deteriorated due to ultraviolet rays from the outside.

In the light emitting device of the present embodiment, a loss due to Fresnel reflection (Fresnel loss) occurs when light passes through the package substrate 40, so it is desirable to reduce the Fresnel loss when transmitted through the package substrate 40. As a means for suppressing the Fresnel loss, for example, an anti-reflection coat (hereinafter abbreviated as an AR film) made of a single-layer or multilayer dielectric film is provided on at least one surface of the package substrate 40 in the thickness direction. It is conceivable to provide it. Here, when the AR film is formed of, for example, a magnesium fluoride film having a refractive index n of 1.38, if the design wavelength λ ₀ is 550 nm, the thickness of the AR film is λ ₀ / 4n = 550 / ( 4 × 1.38) = 99.6 nm. Similarly, when the AR film is composed of, for example, an aluminum oxide film having a refractive index n of 1.58, if the design wavelength λ ₀ is 550 nm, the thickness of the AR film is λ ₀ / 4n = 550 / (4 × 1.58) = 87.0 nm. The AR film may be a stacked film (two-layer AR film) of a magnesium fluoride film having a thickness of 99.6 nm and an aluminum oxide film having a thickness of 87.0 nm. Note that a material other than magnesium fluoride or aluminum oxide may be adopted as the material of the dielectric film.

  In the light emitting device of this embodiment, by providing an AR film on at least one surface, preferably both surfaces, in the thickness direction of the package substrate 40, Fresnel loss can be reduced and light extraction efficiency can be improved.

(Embodiment 2)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 7, each of the organic EL elements 20 is disposed on one side of the package substrate 40 facing the light transmissive substrate 10. External connection electrodes 42 and 44 that are electrically connected to the pads 122 and 124 through connection portions 132 and 134 made of bonding wires (for example, metal wires such as gold wires and aluminum wires) are formed. Is different. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1. FIG.

  In the present embodiment, the connection portions 132 and 134 that electrically connect the pads 122 and 124 of the organic EL element 20 and the external connection electrodes 42 and 44 are configured by bonding wires. May be composed of a conductive paste (eg, silver paste) or a metal film.

  By the way, in the light emitting device according to the present embodiment, the protection unit 50 that prevents the moisture from reaching the organic EL element 20 described in the first embodiment is formed so as to cover the side edges of the translucent substrate 10 and the bonding portion 29. It is. Accordingly, it is possible to prevent moisture from entering from the side edge of the translucent substrate 10 and the side edge of the bonding portion 29, and the reliability is further improved.

(Embodiment 3)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the second embodiment. As shown in FIG. 8, the protection unit 50 is configured by a second glass substrate, and the protection unit 50 made of the glass substrate includes: The difference is that the glass substrate constituting the package substrate 40 is sealed through a joint 80 made of frit glass. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 2, and description is abbreviate | omitted.

  In the light emitting device of the present embodiment, the package substrate 40 is made of a first glass substrate, and the protection unit 50 is made of a second glass substrate. The second glass substrate has a surface facing the first glass substrate. Since the entire circumference of the peripheral portion is sealed to the first glass substrate side by the joining portion 80 made of frit glass, when the joining portion 80 is made of an adhesive made of an organic material such as an epoxy resin. Compared with moisture resistance, it can improve.

  Moreover, as a 2nd glass substrate which comprises the protection part 50, using the glass substrate (for example, an alkali free glass substrate, a soda-lime glass substrate, etc.) of the same glass material as the 1st glass substrate of the board | substrate 40 for packages, If the linear expansion coefficients of the second glass substrate and the first glass substrate are made the same, it is possible to prevent warpage of the package substrate 40 due to a difference in linear expansion coefficient between the package substrate 40 and the protection unit 50. In addition, variations in optical characteristics due to warpage of the package substrate 40 can be reduced, and the reliability of the joint 80 can be increased.

  In the light emitting device according to the present embodiment, a sealing medium (for example, a liquid such as silicone oil or paraffin oil, or silicone is provided in an airtight space surrounded by the package substrate 40, the protection unit 50, and the bonding unit 80. , Resin such as paraffin and wax) 90 is enclosed. Therefore, it is possible to more reliably prevent moisture from reaching the organic EL element 20 from the outside, and the reliability is improved. In addition, since the heat generated in the organic EL element 20 can be efficiently radiated through the medium 90, the temperature rise of the organic EL element 20 can be suppressed, and the life can be extended. The current flowing to the organic EL element 20 can be increased to increase the luminance.

  Here, in the light emitting device of the present embodiment, when the medium 90 is a liquid, the bonding wires constituting the connecting portions 132 and 134 and the connecting portions between the bonding wires and the pads 122 and 124 and the external connection electrodes 42 and 44 are used. Therefore, there is a concern that impurities such as metals are eluted into the medium 90 and reliability is lowered. Therefore, in the present embodiment, the connection parts 132 and 134 are covered with a covering part 150 made of a sealing material (for example, silicone resin). Therefore, since the connection parts 132 and 134 are covered with the covering part 150, the reliability is improved. Moreover, in this embodiment, since the coating | coated part 150 is formed so that the surrounding part of the translucent board | substrate 10 may be covered over the perimeter (that is, the planar view shape of the coating | coated part 150 is frame shape), It is possible to more reliably prevent the medium 90 from leaking into the space 70 between the uneven structure portion 50 and the package substrate 40.

  However, the airtight space described above does not necessarily need to enclose the medium 90, and may be an inert gas atmosphere or a vacuum atmosphere. In these cases, moisture is applied to the surface of the protection unit 50 facing the organic EL element 20. It is preferable to provide a water absorbing material to be adsorbed. As this type of water-absorbing material, for example, a calcium oxide-based desiccant (getter containing calcium oxide) may be used.

(Embodiment 4)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the third embodiment, and is different in that some of the protrusions 31 of the many protrusions 31 form a spacer 60 as shown in FIG. Just do it. In FIG. 9, two types of protrusions 31 having different heights are mixed, and the protrusions 31 having a large height dimension constitute the spacer 60. In addition, the same code | symbol is attached | subjected and demonstrated to the component similar to Embodiment 3. FIG.

  In short, in Embodiment 3, all of the many protrusions 31 constituting the concavo-convex structure portion 30 constitute the spacer 60, whereas in the light emitting device of this embodiment, a large number of the concavo-convex structure portion 30 is constituted. A part of the protrusion 31 constitutes the spacer 60.

  Thus, in the light emitting device of this embodiment, the light extraction efficiency can be improved as compared with the case where the spacer 60 and the concavo-convex structure portion 30 are separate bodies, and the light extraction efficiency can be improved while improving the light extraction efficiency. The degree of freedom in designing the height dimension is increased.

  However, in this embodiment, it is preferable to provide the protrusions 31 to be the spacers 60 at regular intervals, and by providing them at regular intervals, it is possible to prevent the translucent substrate 10 from being partially bent.

(Embodiment 5)
The basic configuration of the light emitting device of this embodiment is substantially the same as that of the fourth embodiment, and as shown in FIGS. 10 and 11, the spacer 60 is configured by a wall-like rib different from the protrusion 31 of the concavo-convex structure portion 30. Is different. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 4, and description is abbreviate | omitted.

  Thus, in the light emitting device according to the present embodiment, the protrusion 31 of the concavo-convex structure portion 30 can be more reliably prevented from being damaged, and the degree of freedom in designing the protrusion 31 of the concavo-convex structure portion 30 is increased. Here, if the translucent substrate 10 is formed by injection molding, the concavo-convex structure portion 30 and the spacer 60 can be easily and simultaneously formed.

  In the present embodiment, the spacers 60 made of wall-like ribs are provided in a stripe shape in plan view. However, the spacers 60 are not limited to the stripe shape, and may be provided in a lattice shape, for example.

(Embodiment 6)
The basic configuration of the light emitting device of the present embodiment shown in FIG. 12 is substantially the same as that of the fourth embodiment. Both the anode 22 and the cathode 24 of the organic EL element 20 are made of transparent electrodes, and the light emitting device is far from the translucent substrate 10. The difference is that a light reflecting member 25 that reflects light from the light emitting layer is disposed on the surface of the second electrode (the cathode 24 in the illustrated example) opposite to the light transmissive substrate 10 side. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 4, and description is abbreviate | omitted.

  The light reflecting member 25 may be in direct contact with the second electrode, or, as shown in FIG. 12, the light generated in the light emitting layer interferes between the light reflecting member 25 and the second electrode. A light-transmitting layer 26 (hereinafter referred to as a light-transmitting layer 26) having a thickness that does not occur may be interposed.

  The light reflective member 25 may be a member having so-called specular reflectivity, or a member having light scattering / diffuse reflectivity. As the member having specular reflectivity, any reflector that substantially exhibits specular reflection, such as a metal film such as Al or Ag, or a reflective film made of a dielectric multilayer film, can be used. The light reflecting member 25 having light scattering / diffuse reflecting properties is, for example, a metal film or dielectric formed on a reflective surface composed of a layer of particles such as barium oxide and titanium oxide, or a surface having an uneven shape. It is formed of a reflective film composed of a multilayered body film or a light-transmitting layer having a light scattering property, a light diffusing property, and a diffractive property provided on a layer having a specular reflection property.

  The light transmissive layer 26 interposed between the light reflective member 25 and the second electrode is preferably a light transmissive insulating layer. The material of this insulating layer is not particularly limited as long as it is not contrary to the gist of the present invention. As this insulating layer, for example, a light transmissive material such as silicon oxide, silicon nitride, lithium fluoride, magnesium fluoride is deposited Spin coating, dip coating, coating, ink jet printing, gravure printing, screens, layers formed by film deposition methods such as sputtering, sputtering, and CVD, and inorganic and organic resins It is formed by applying or arranging a layer formed by coating by an appropriate coating method such as a printing method or a printing method, a sheet made of an organic material or an inorganic material, a film, a gel, a seal, a plate, etc. Examples include layers. The refractive index of this insulating layer is preferably equal to that of the second electrode.

  Further, the thickness that does not cause interference with the light generated in the light emitting layer is not particularly limited as long as it is on the order of several times the wavelength of the light, but is, for example, about 1 μm to 3 mm. If the thickness of the light-transmitting insulating layer is in such a range, the angle dependency of the emission spectrum is further reduced.

  Further, the light-transmitting insulating layer interposed between the light reflecting member 25 and the second electrode may have light scattering properties, and in this case, the angle dependency of the emission spectrum is further reduced. Become so. As such an insulating layer, for example, a material containing a light scattering component (for example, particles, foil, etc. having a different refractive index from the peripheral material forming the insulating layer) in the above light-transmitting insulating layer, A combination of materials with a refractive index interface inside, for example, a layer made of one material and a layer made of the other material on a layer with irregularities, and exhibiting scattering properties by causing layer separation with surrounding materials It can be formed of a combination of materials, or a layer containing reflective particles, foil, surface, or the like.

  In other embodiments, both the anode 22 and the cathode 24 of the organic EL element 20 may be configured by transparent electrodes. In this case, the second electrode (see FIG. In the example shown, a light reflective member 25 is preferably provided on the surface of the cathode 24) opposite to the light transmissive substrate 10 side, and a light transmissive layer is provided between the light reflective member 25 and the second electrode. 26 may be interposed.

DESCRIPTION OF SYMBOLS 10 Translucent board | substrate 20 Organic EL element 30 Uneven structure part 31 Protrusion 32 Recess 40 Package substrate 50 Protection part 60 Spacer 70 Space

Claims (1)

An organic EL element having a light-transmitting substrate, an organic EL layer formed on one surface side of the light-transmitting substrate and having a light-emitting layer interposed between an anode and a cathode; A light emitting device provided with a concavo-convex structure portion that is provided on a surface side and suppresses reflection of light emitted from the organic EL element on the other surface, and is disposed on the other surface side of the translucent substrate. A package substrate at least partially formed of a light-transmitting material; and a protective portion that covers a side of the organic EL element opposite to the light-transmitting substrate and prevents moisture from reaching the organic EL element. The package substrate is made of a glass substrate, the translucent substrate is made of a plastic substrate, and the protective part is made of a thin film of an inorganic material or a laminated film of a thin film of an inorganic material, Each of the anode and the cathode is The Yes and formed to extend to the site which does not overlap with the light-emitting layer, some of these extended portions are exposed without being covered by the protection unit, the exposed sites constitute a pad, The light-emitting device , wherein the protection part is formed so as to cover a side edge of the translucent substrate and a side edge of a joint part that joins the translucent substrate and the package substrate .

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