JP2021170498A - Light emitting device - Google Patents

Abstract

To provide a light emitting device enabling light extraction efficiency to be more reliably improved and enabling view angle dependency to be reduced.SOLUTION: A light emitting device 10 according to one embodiment comprises: a substrate 12; a first electrode layer 14 provided on the substrate; an intermediate structure 16 provided on the first electrode layer and including a light emitting layer 161; and a second electrode layer 18 provided on the intermediate structure. One of the first electrode layer and the second electrode layer is a translucent electrode layer, and the other is a light reflective electrode layer. When a peak wavelength in a color-matching function corresponding to green color in an XYZ colorimetric system is defined as λG [nm], an optical distance in the intermediate structure between a light-emitting position 165 of light having the wavelength λG and the translucent electrode layer is within any one of a first range of 140-200 nm, a second range of 400-460 nm, and a third range of 680-720 nm, and an optical distance between the light emitting position and the light reflective electrode layer is odd-number times of λG/4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a light emitting device.

As an example of the light emitting device, the organic electroluminescence device (organic EL device) described in Patent Document 1 is known. The light emitting device described in Patent Document 1 includes a substrate having light transmission, a light diffusion layer provided on the surface of the substrate, a light transmission electrode provided on the surface of the light diffusion layer, and the light transmission. It has a light-reflecting electrode paired with a sex electrode, and a plurality of light emitting layers provided at a distance between the light-transmitting electrode and the light-reflecting electrode.

Patent No. 5830194

The light emitting device described in Patent Document 1 is used, for example, in a lighting device. In this case, it is preferable that the light extraction efficiency from the light emitting device is high and the viewing angle dependence is low. In Patent Document 1, the optical distance between each light emitting position (for example, the center position of each light emitting layer) and the light reflecting electrode is λ / 4 in order to realize high light extraction efficiency and reduce the viewing angle dependence. It is designed so that the value deviates from an odd multiple of.

However, in the above design, it is considered that the light extraction efficiency is actually reduced because the cavity effect between each light emitting position (for example, the center position of each light emitting layer) and the light reflecting electrode is reduced.

Therefore, an object of the present invention is to provide a light emitting device capable of more reliably improving the light extraction efficiency and reducing the viewing angle dependence.

The light emitting device according to one aspect of the present invention includes a substrate, a first electrode layer provided on the substrate, an intermediate structure including the light emitting layer, and the intermediate structure. A second electrode layer provided on the body is provided, and one of the first electrode layer and the second electrode layer is a translucent electrode layer and the other is a light-reflecting electrode layer. When the peak wavelength in the color matching function corresponding to green in the color system is λ _G [nm], the optical distance between the light emitting position _{of the wavelength λ G in the intermediate structure and the translucent electrode layer.} Is within any of the first range of 140 nm to 200 nm, the second range of 400 nm to 460 nm, and the third range of 680 nm to 720 nm, and the optical distance between the light emitting position and the light reflecting electrode layer. Is an odd multiple of _{λ G / 4.}

In the above configuration, the light emitted at the light emitting position is output from the translucent electrode layer side. When the optical distance between the light emitting position and the translucent electrode layer is in any of the first to third ranges, the viewing angle dependence is reduced. Further, if the optical distance between the light-reflecting electrode layer and the light-reflecting electrode layer is an _{odd multiple of λ G} / 4, the light directly directed from the light emitting position to the light-transmitting electrode layer and the light reflected from the light-emitting position by the light-reflecting electrode layer. The light extraction efficiency is improved by the interference effect (or cavity effect) with the light directed to the translucent electrode layer. Therefore, in the light emitting device, the light extraction efficiency can be improved and the viewing angle dependence can be reduced.

The light emitting layer may output white light. In this case, the light emitting device can be applied to, for example, a lighting device.

The light emitting layer has a first light emitting layer and a second light emitting layer adjacent to the first light emitting layer and laminated on the first light emitting layer, and light emitted from the second light emitting layer. May be the complementary color of the light emitted from the first light emitting layer. In this case, white light can be output from the light emitting device.

The first electrode layer may contain silver or a silver alloy. In this case, the thickness of the first electrode layer may be 8 nm or more and 35 nm or less.

The light emitting device according to the embodiment further includes a high refractive index layer provided between the substrate and the first electrode layer and having a higher refractive index than the substrate, and the substrate is a translucent substrate. The first electrode layer may be the translucent electrode layer. In this case, light is output from the translucent substrate side. In the above configuration, reflection between the light-transmitting substrate and the high-refractive index layer can be prevented, so that light can be extracted more efficiently from the translucent substrate side.

The optical distance between the light emitting position and the light reflecting electrode layer may be 100 nm or more and 155 nm or less.

When the peak wavelengths in the color matching functions corresponding to red and blue in the XYZ color system are λ _R [nm] and λ _B [nm], respectively, the light emission position and wavelength λ _{of the wavelength λ R in the intermediate structure are The optical distance between each of the light emitting positions of B} and the translucent electrode layer is within any of the first range, the second range, and the third range, and has a wavelength of λ _R. The optical distance between the light emitting position and the light reflecting electrode layer is an _{odd multiple of λ R} / 4, and _{the optical distance between the light emitting position of wavelength λ B} and the light reflecting electrode layer is It may be an odd multiple of _{λ B / 4.}

According to the present invention, it is possible to provide a light emitting device capable of more reliably improving the light extraction efficiency and reducing the viewing angle dependence.

FIG. 1 is a schematic diagram for explaining the configuration of an organic electroluminescence device (organic EL device) which is an example of a light emitting device according to an embodiment. FIG. 2 is a drawing showing the result of simulation A. FIG. 3 is a drawing showing the result of simulation B. FIG. 4 is a drawing showing the result of simulation C.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same elements are designated by the same reference numerals, and duplicate description will be omitted. The dimensional ratios in the drawings do not always match those described.

FIG. 1 is a schematic diagram for explaining the configuration of an organic electroluminescence device (organic EL device) which is an example of a light emitting device according to an embodiment. The organic EL device 10 shown in FIG. 1 includes a substrate 12, a first electrode layer 14, an intermediate structure 16, and a second electrode layer 18. The organic EL device 10 is a light emitting device that outputs white light. The organic EL device 10 may include a high refractive index layer 20 between the substrate 12 and the first electrode layer 14. In the present embodiment, the bottom emission type organic EL device will be described, and the case where the first electrode layer 14 functions as an anode (or a part thereof) and the second electrode layer 18 functions as a cathode will be described.

[substrate]
The substrate 12 is a translucent substrate having translucency with respect to light (including visible light having a wavelength of 400 nm to 800 nm) emitted by the organic EL device (electronic device) 10 to be manufactured. The transmittance of the substrate 12 can be 40% to 92% in visible light. An example of the thickness of the substrate 12 is 30 μm to 700 μm.

The substrate 12 may be a rigid substrate such as a glass substrate and a silicon substrate, or a flexible substrate such as a plastic substrate and a polymer film. The flexible substrate is a substrate having a property of being able to bend the substrate without shearing or breaking even when a predetermined force is applied to the substrate. The substrate 12 may further have a barrier layer having a moisture barrier function. The barrier layer may have a function of barriering gas (for example, oxygen) in addition to a function of barriering water.

[High refractive index layer]
The high refractive index layer 20 is provided on the substrate 12 and has a higher refractive index than the substrate 12. The high refractive index layer 20 functions as an antireflection layer. An example of the high refractive index layer 20 is a metal oxide layer. Examples of the material of the high refractive index layer 20 include indium oxide, zinc oxide, tin oxide, and indium tin oxide. The thickness of the high refractive index layer 20 can be determined in consideration of translucency. An example of the thickness of the high refractive index layer 20 is 10 nm to 150 nm, preferably 45 nm to 55 nm. The high refractive index layer 20 may be a part of the anode.

The high refractive index layer 20 can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method include a vacuum deposition method, a sputtering method, an ion plating method, and a CVD method. Examples of the coating method include an inkjet printing method, a slit coating method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a spray coating method, a screen printing method, a flexographic printing method, and an offset printing method. Examples include a printing method and a nozzle printing method.

[First electrode layer]
The first electrode layer 14 is provided on the substrate 12. As shown in FIG. 1, in the form in which the organic EL device 10 includes the high refractive index layer 20, the first electrode layer 14 is provided on the high refractive index layer 20. The first electrode layer 14 is, for example, a metal layer. The material of the first electrode layer 14 is at least one selected from the group consisting of, for example, silver (Ag), gold (Au), aluminum (Al), copper (Cu), iron (Fe) and molybdenum (Mo). Includes metal or silver alloys. The first electrode layer 14 preferably contains silver or a silver alloy.

The first electrode layer 14 is a translucent electrode layer having translucency with respect to the light output by the organic EL device 10. The thickness of the first electrode layer 14 can be determined in consideration of translucency, light extraction efficiency, electrical conductivity, and the like. An example of the thickness of the first electrode layer 14 is 8 nm to 35 nm.

The first electrode layer 14 can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method include a vacuum deposition method, a sputtering method, an ion plating method, and a CVD method. Examples of the coating method include an inkjet printing method, a slit coating method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a spray coating method, a screen printing method, a flexographic printing method, and an offset printing method. Examples include a printing method and a nozzle printing method.

[Intermediate structure]
The intermediate structure 16 has a light emitting layer 161. The light emitting layer 161 is a functional layer having a function of emitting light (including visible light), and outputs white light in the present embodiment. The light emitting layer 161 is an organic layer containing an organic substance. The light emitting layer 161 is usually composed of an organic substance that mainly emits at least one of fluorescence and phosphorescence, or a dopant material that assists the organic substance. Dopant materials are added, for example, to improve luminous efficiency and change the emission wavelength. The organic substance may be a small molecule compound or a high molecular compound.

Examples of organic substances that are luminescent materials that mainly emit at least one of fluorescence and phosphorescence include the following pigment-based materials, metal complex-based materials, and polymer-based materials.

(Dye material)
Examples of the dye-based material include cyclopendamine derivatives, tetraphenylbutadiene derivative compounds, triphenylamine derivatives, oxaziazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, pyrrole derivatives, and thiophene ring compounds. , Pylin ring compounds, perinone derivatives, perylene derivatives, oligothiophene derivatives, oxaziazole dimers, pyrazoline dimers, quinacridone derivatives, coumarin derivatives and the like.

(Metal complex material)
Examples of the metal complex material include rare earth metals such as Tb, Eu, and Dy, or Al, Zn, Be, Ir, and Pt as the central metal, and oxadiazole, thiadiazol, phenylpyridine, phenylbenzoimidazole, and quinoline. Examples of metal complexes having a structure as a ligand include metal complexes that emit light from a triple-term excited state such as iridium complexes and platinum complexes, aluminum quinolinol complexes, benzoquinolinol berylium complexes, and benzoxazolyl zinc complexes. Examples thereof include a benzothiazole zinc complex, an azomethylzinc complex, a porphyrin zinc complex, and a phenanthroline europium complex.

(Polymer-based material)
As the polymer-based material, a polyparaphenylene vinylene derivative, a polythiophene derivative, a polyparaphenylene derivative, a polysilane derivative, a polyacetylene derivative, a polyfluorene derivative, a polyvinylcarbazole derivative, and the above-mentioned dye-based material and metal complex-based luminescent material are polymerized. Things and so on.

In the present embodiment, the light emitting layer 161 has a first light emitting layer 161A and a second light emitting layer 161B.

The first light emitting layer 161A is arranged on the first electrode layer 14 side of the second light emitting layer 161B. The first light emitting layer 161A contains a material that emits red light. Examples of the material that emits red light include a coumarin derivative, a thiophene ring compound and a polymer thereof, a polyparaphenylene vinylene derivative, a polythiophene derivative, and a polyfluorene derivative. As the material that emits red light, a polyparaphenylene vinylene derivative, a polythiophene derivative, a polyfluorene derivative, and the like, which are polymer materials, are preferable.

The second light emitting layer 161B is adjacent to the first light emitting layer 161A and is laminated on the first light emitting layer 161A. The second light emitting layer 161B includes a material that emits blue light and a material that emits green light. Examples of the material that emits blue light include dystilyl arylene derivatives, oxadiazole derivatives, and polymers thereof, polyvinylcarbazole derivatives, polyparaphenylene derivatives, polyfluorene derivatives, and the like. As the material that emits blue light, a polyvinyl carbazole derivative, a polyparaphenylene derivative, a polyfluorene derivative, or the like, which is a polymer material, is preferable. Examples of the material that emits green light include quinacridone derivatives, coumarin derivatives and polymers thereof, polyparaphenylene vinylene derivatives, polyfluorene derivatives and the like. As the material that emits green light, a polyparaphenylene vinylene derivative, a polyfluorene derivative, or the like, which is a polymer material, is preferable.

The intermediate structure 16 includes at least one of a conductive layer 162 and a hole injection layer 163 between the first electrode layer 14 and the light emitting layer 161 (specifically, the first light emitting layer 161A in the configuration shown in FIG. 1). You may.

The conductive layer 162 is adjacent to the first electrode layer 14 and is laminated on the first electrode layer 14. The conductive layer 162 has translucency. The conductive layer 162 may be a part of the anode. Examples of the material of the conductive layer 162 include indium tin oxide (abbreviated as ITO) and indium zinc oxide (abbreviated as IZO).

The conductive layer 162 can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method and the coating method can be the same as the examples given in the method of forming the first electrode layer 14.

In the form in which the organic EL device 10 includes the high refractive index layer 20 and the conductive layer 162, it is a laminate having the high refractive index layer 20, the first electrode layer 14 and the conductive layer 162, and is on the high refractive index layer 20. , The first electrode layer 14 and the conductive layer 162 are laminated in this order, and the laminated body may be an anode.

The transmittance in the visible region of the laminated structure including the substrate 12 and the laminated body (the laminated body having the high refractive index layer 20, the first electrode layer 14 and the conductive layer 162) is, for example, 40% to 90%, and the reflectance is Can be, for example, 4% -40%. In other words, the material, thickness, and the like of the substrate 12, the high refractive index layer 20, the first electrode layer 14, and the conductive layer 162 can be set so that the above-mentioned transmittance and reflectance can be realized. The same applies when the substrate 12 and the laminated structure do not have at least one of the high refractive index layer 20 and the conductive layer 162.

The hole injection layer 163 is formed from the first electrode layer 14 (the conductive layer 162 in the form in which the intermediate structure 16 includes the conductive layer 162) to the light emitting layer 161 (specifically, the first light emitting layer 161A in the configuration shown in FIG. 1). ) Is a functional layer having a function of improving the hole injection efficiency. The hole injection layer 163 may be an inorganic layer or an organic layer. The hole injection material constituting the hole injection layer 163 may be a low molecular weight compound or a high molecular weight compound.

Examples of the low molecular weight compound include metal oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide, metal phthalocyanine compounds such as copper phthalocyanine, and carbon.

Polymeric compounds include, for example, polythiophene derivatives such as polyaniline, polythiophene, polyethylenedioxythiophene (PEDOT), polypyrrole, polyphenylene vinylene, polythienylene vinylene, polyquinoline and polyquinoxaline, and derivatives thereof; aromatic amine structures. Examples thereof include conductive polymers such as polymers containing the above in the main chain or the side chain.

The hole injection layer 163 can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method and the coating method can be the same as the examples given in the method of forming the first electrode layer 14.

The intermediate structure 16 may include an electron transport layer 164 between the light emitting layer 161 and the second electrode layer 18.

The electron transport layer 164 is a functional layer having a function of receiving electrons from the second electrode layer 18 and transporting electrons to the light emitting layer 161 (specifically, the second light emitting layer 161B in the configuration shown in FIG. 1).

The electron transport layer 164 is an organic layer containing an electron transport material. A known material can be used as the electron transport material. Examples of the electron transporting material constituting the electron transporting layer 164 include oxadiazole derivative, anthracinodimethane or its derivative, benzoquinone or its derivative, naphthoquinone or its derivative, anthraquinone or its derivative, tetracyanoanthraquinodimethane or its derivative. , Fluolenone derivative, diphenyldicyanoethylene or its derivative, diphenoquinone derivative, or metal complex of 8-hydroxyquinoline or its derivative, polyquinolin or its derivative, polyquinoxalin or its derivative, polyfluorene or its derivative and the like.

The electron transport layer 164 can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method and the coating method can be the same as the examples given in the method of forming the first electrode layer 14.

[Second electrode layer]
The second electrode layer 18 is provided on the intermediate structure 16. The second electrode layer 18 is a reflective electrode layer. The second electrode layer 18 may have a reflectance of 70% or more, more preferably 90% or more.

Examples of the material of the second electrode layer 18 include alkali metals, alkaline earth metals, transition metals, and elements of Group 13 of the periodic table. Specific examples of the material of the second electrode layer 18 include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, ittrium, indium, and cerium. Metals such as samarium, europium, terbium, itterbium, alloys of two or more of the metals, one or more of the metals, and gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten, Examples include alloys with one or more of tin, graphite, graphite interlayer compounds, and the like. Examples of alloys include magnesium-silver alloys, magnesium-indium alloys, magnesium-aluminum alloys, indium-silver alloys, lithium-aluminum alloys, lithium-magnesium alloys, lithium-indium alloys, calcium-aluminum alloys and the like.

The thickness of the second electrode layer 18 is set in consideration of electrical conductivity and durability. The thickness of the second electrode layer 18 is usually 10 nm to 10 μm, preferably 20 nm to 1 μm, and more preferably 50 nm to 500 nm.

Examples of the method for forming the second electrode layer 18 include an inkjet printing method, a slit coating method, a gravure coating method, a screen printing method, a spray coating method and other coating methods, a vacuum deposition method, a sputtering method, and a lamination in which a metal thin film is thermocompression bonded. Law etc. can be mentioned.

When the wavelength corresponding to the peak of the green color matching function in the XYZ color system (hereinafter, may be referred to as “peak wavelength”) is referred to as λ _G [nm], the intermediate structure 16 included in the organic EL device 10 The optical distance (optical thickness) nd1 between the emission position 165 (see FIG. 1) of light having a wavelength of λ _G and the first electrode layer 14 is 140 nm to 200 nm, which is the first range, 400 nm to 460 nm. It is within any of the second range of 680 nm to 720 nm and the third range of 680 nm to 720 nm. The third range may be 680 nm to 720 nm.

The light emitting positions 165 are positions where charge recombination occurs, and there are actually a plurality of light emitting positions. In the present embodiment, since each layer constituting the organic EL device 10 is assumed to be a flat layer, a plurality of light emitting positions 165 may exist substantially on the same plane. Therefore, in FIG. 1, the light emitting position 165 is shown as a surface, specifically, as an interface between the first light emitting layer 161A and the second light emitting layer 161B. Since the first light emitting layer 161A and the second light emitting layer 161B are included in the light emitting layer 161, the light emitting position 165 is located in the light emitting layer 161. As described above, since the light emitting position 165 is a position where charge recombination occurs, the position is not limited to the position of the interface between the first light emitting layer 161A and the second light emitting layer 161B, and is not limited to the position of the interface between the first light emitting layer 161A and the second light emitting layer 161B. It may be inside the light emitting layer 161B or the surface of the light emitting layer 161. In the manufactured organic EL device 10, the light emitting position 165 is, for example, the result of calculating the light emitting intensity angle distribution and the light emitting intensity angle distribution when the light emitting position is changed for each wavelength of the emitted light by the transfer matrix method. It can be identified by matching. As a method of calculating the emission intensity angle distribution by the transfer matrix method, the simulation program setfos developed by FLUXIM can be used.

The peak wavelength of the color matching function means a wavelength corresponding to the maximum value in the curve represented by the color matching function, and the wavelength λ _G is, for example, 555 nm in CIE 1931.

Optical distance nd1 is the intermediate structure 16 and emission position 165 of the layer to light in the thickness and the wavelength lambda _G optical distance (a layer for light having a wavelength lambda _G of a plurality of layers present between the first electrode layer 14 It is the sum of the products of the refractive indexes). In other words, the thickness of the plurality of layers existing between the light emitting position 165 and the first electrode layer 14 in the intermediate structure 16 is the optical distance in consideration of the refractive index of _{each layer with respect to light having a wavelength of λ G.} It is set to realize nd1. If a layer contains a plurality of materials, the optical distance for light with a wavelength lambda _G of the layer, by the sum of the values obtained by multiplying the refractive index and thickness with respect to light having a wavelength lambda _G of a plurality of materials in the layer It is possible (hereinafter, the same applies).

In the example shown in FIG. 1, the optical distance nd1 is _{the product of the thickness t1 of the conductive layer 162 and the refractive index of the conductive layer 162 with respect to the wavelength λ G} , the thickness t2 of the hole injection layer 163, and the hole injection layer 163. the product of the refractive index for the wavelength lambda _G of the sum of the product of the refractive index and the thickness t3 of the first light-emitting layer 161A with respect to the wavelength lambda _G of the first light-emitting layer 161A. In other words, the thicknesses t1 to t3 are set so as to satisfy the optical distance nd1 in consideration of the refractive indexes of the conductive layer 162, the hole injection layer 163, and the first light emitting layer 161A with _{respect to the wavelength λ G.} NS.

An example of thickness t1 is 10 nm to 200 nm. An example of thickness t2 is 10 nm to 110 nm. An example of thickness t3 is 10 nm to 60 nm.

The optical distance nd2 between the second electrode layer 18 which is the light-reflecting electrode layer and the light emitting position 165 is an odd multiple of _{λ G / 4.} In this specification, an odd multiple of lambda _{G /} 4 is a concept including a certain tolerance with respect to an odd multiple of λ _{G /} 4. A certain allowable range is set in consideration of, for example, a manufacturing error, a range normally allowed when light is intensified due to thin film interference, and the like, for example, ± 5 (preferably 2.) with respect to an odd multiple of _{λ G / 4.} 5) nm. The optical distance nd2 is, for example, 100 nm or more and 155 nm or less.

Optical distance nd2 is the intermediate structure 16 and emission position 165 of the layer to light in the thickness and the wavelength lambda _G optical distance (a layer for light having a wavelength lambda _G of a plurality of layers present between the second electrode layer 18 It is the sum of the products of the refractive indexes). In other words, the thickness of the plurality of layers existing between the light emitting position 165 and the second electrode layer 18 in the intermediate structure 16 is the optical distance in consideration of the refractive index of _{each layer with respect to light having a wavelength of λ G.} It is set to realize nd2.

In the example shown in FIG. 1, the optical distance nd2 is the product of the thickness t4 of the second light emitting layer 161B and the _{refractive index of the second light emitting layer 161B with respect to the wavelength λ G,} and the thickness t5 of the electron transport layer 164 and electron transport. It is the sum of the product of the refractive index with respect to _{the wavelength λ G} of the thickness t5 of the layer 164. In other words, the thickness t4 and the thickness t5 are set so as to satisfy the optical distance nd2 in consideration of the refractive indexes of the second light emitting layer 161B and the electron transporting layer 164 with _{respect to the wavelength λ G.}

An example of thickness t4 is 50 nm-80 nm. An example of thickness t5 is 10 nm to 30 nm.

The organic EL device 10 is formed on the substrate 12 in the order of the first electrode layer 14, the intermediate structure 16, and the second electrode layer 18 by the method exemplifying the first electrode layer 14, the intermediate structure 16, and the second electrode layer 18. Manufactured by In the form in which the intermediate structure 16 has a multi-layer structure, the intermediate structure 16 may be formed in order from the layer adjacent to the first electrode layer 14.

In order to manufacture the organic EL device 10 so as to have the optical distance nd1 and the optical distance nd2, the intermediate structure 16 has the intermediate structure 16 so that the optical distance nd1 and the optical distance nd2 are within the illustrated ranges by, for example, a simulation in advance. The thickness of each layer may be set.

In the organic EL device 10, the light emitting layer 161 emits light by energizing the organic EL device 10 via the first electrode layer 14 and the second electrode layer 18. Since the second electrode layer 18 is the reflective electrode layer and the first electrode layer 14 is the transmissive electrode layer, the light output from the light emitting layer 161 is emitted from the substrate 12 side. Since the light emitting layer 161 contains a material that emits red light, a material that emits green light, and a material that emits blue light, white light is output from the organic EL device 10. The organic EL device 10 that outputs white light functions as, for example, a lighting device.

Since the optical distance nd1 is included in any of the first to third ranges, the viewing angle dependence of the organic EL device 10 can be reduced. This point will be described in detail with reference to the simulation results. When the optical distance nd2 is _{an odd multiple of λ G} / 4, the light directly from the luminous position 165 toward the substrate 12 side (light extraction side) and the light reflected by the second electrode layer 18 toward the second electrode layer 18 High luminous efficiency, that is, high light extraction efficiency can be obtained due to the interference effect (or cavity effect) with the light. Therefore, in the configuration of the organic EL device 10, high light extraction efficiency can be realized and viewing angle dependence can be reduced.

When the first electrode layer 14 contains silver or a silver alloy, high conductivity is realized, so that power efficiency can be improved. Further, in the first electrode layer 14 containing silver or a silver alloy, excellent surface flatness can be realized in the first electrode layer 14, so that the light emission unevenness of the organic EL device 10 can be reduced. The thickness of the first electrode layer 14 containing silver or a silver alloy is preferably 8 nm or more and 35 nm or less. If the thickness of the first electrode layer 14 is less than 8 nm, the conductivity decreases, and if the thickness of the first electrode layer 14 is larger than 35 nm, the reflectance of the first electrode layer 14 increases, and the light extraction efficiency increases. Decreases. Therefore, if the thickness of the first electrode layer 14 is within the above range, high light extraction efficiency can be realized while enabling high conductivity.

In the form in which the organic EL device 10 includes the high refractive index layer 20, reflection at the interface between the substrate 12 and the high refractive index layer 20 is prevented, so that the light extraction efficiency can be further improved.

Next, the action and effect of the organic EL device 10 will be described based on the simulation results.

The configuration shown in FIG. 1 was adopted as the simulation model. That is, the simulation was carried out using an organic EL device in which the high refractive index layer 20, the first electrode layer 14, the intermediate structure 16 and the second electrode layer 18 were laminated on the substrate 12 from the substrate 12 side. The intermediate structure 16 includes a conductive layer 162, a hole injection layer 163, a first light emitting layer 161A, a second light emitting layer 161B, and an electron transport layer 164. In the intermediate structure 16, the conductive layer 162 and hole injection The layer 163, the first light emitting layer 161A, the second light emitting layer 161B, and the electron transport layer 164 were laminated in this order. For convenience of explanation, the organic EL device as a simulation model is referred to as an organic EL device 10M. As shown in FIG. 1, the light emitting position 165 of the wavelength λ _G was set as the interface between the first light emitting layer 161A and the second light emitting layer 161B. The first light emitting layer 161A emits red light, and the second light emitting layer 161B emits blue and green, so that the organic EL device 10M emits white light.

<Simulation A>
In simulation A, in the organic EL device 10M, silver is assumed as the material of the first electrode layer 14, the thickness of the first electrode layer 14 is 14 nm, aluminum is assumed as the material of the second electrode layer 18, and the second electrode layer 18 is used. The thickness of the electrode layer 18 was set to 200 nm.

When the set of the optical distance nd1 and the optical distance nd2 is referred to as (nd1, nd2), in the simulation A, the organic EL is used for a plurality of (nd1, nd2) in which the sum of the optical distance nd1 and the optical distance nd2 is constant. The correlated color temperature difference ΔCCT when white light was output from the device 10M was calculated. The correlated color temperature difference ΔCCT is the difference between the color temperature at the radiation angle of 0 ° and the color temperature at the radiation angle of 70 °, where the thickness direction of the substrate 12 is the radiation angle of 0 °.

FIG. 2 is a drawing in which the correlated color temperature difference ΔCCT is mapped to the set of the optical distance nd1 and the optical distance nd2, and is an optical distance nd1 and nd2 dependent map of the correlated color temperature difference ΔCCT. In FIG. 2, the correlated color temperature difference ΔCCT is maximized while changing the thicknesses of the first light emitting layer 161A and the second light emitting layer 161B so that the sum of the optical distance nd1 and the optical distance nd2 is constant (nd1, The correlated color temperature difference ΔCCT with respect to nd2) is mapped. In FIG. 2, the correlated color temperature difference ΔCCT for 90 sets (nd1, nd2) is mapped. The wavelength at the right end of the mapping image shown in FIG. 2 is 720 nm.

FIG. 2 shows that the dark-colored region has a small correlated color temperature difference ΔCCT, in other words, a small viewing angle dependence. Therefore, from FIG. 2, it was verified that the viewing angle dependence was small when the optical distance nd1 was in any of the first to third ranges.

<Simulation B>
In the simulation B, the simulation was carried out under the same conditions as in the simulation A except that the thickness of the first electrode layer 14 was set to 8 nm. The result of simulation B is as shown in FIG. The drawing method of FIG. 3 is the same as that of simulation A.

Also in FIG. 3, the dark-colored region shows that the correlated color temperature difference ΔCCT is small, in other words, the viewing angle dependence is small. Therefore, also in Simulation B, it was verified from FIG. 3 that the viewing angle dependence was small if the optical distance nd1 was in any of the first to third ranges.

In the above simulations A and B, the optical distance nd1 is set with reference to the light emission position 153 of _{the wavelength λ G} corresponding to the peak of the green color matching function (XYZ color system) as described above. .. Wavelength λ _G is the peak wavelength λ _R [nm] (specifically, 599 nm in CIE 1931) of the red color matching function (XYZ color system) and the peak wavelength λ of the blue color function (XYZ color system). _It is located between B [nm] (specifically, 446 nm in CIE 1931). Therefore, by setting the optical distance nd1 by setting the light emission position 165 of the wavelength λ _G as a reference, the viewing angle dependence of red and blue is also reduced, and as a result, the viewing angle dependence of the entire white light is reduced. Is considered to be decreasing.

As described above, since the viewing angle dependence of the entire white light is reduced by setting the optical distance nd1 by setting the light emission position 165 _{of the wavelength λ G as a reference, the organic EL device 10 is used.} Easy to design. Therefore, it is easy to manufacture the organic EL device 10. Since the wavelength λ _G is a wavelength corresponding to the peak of the color matching function (XYZ color system), the viewing angle dependence actually experienced by the user who receives the light from the organic EL device 10 can be reduced.

<Simulation C>
The layer structure of the organic EL device 10M used in simulation C was the same as in simulation A. In the simulation C, when the set of the optical distance nd1 and the optical distance nd2 is referred to as (nd1, nd2), the organic EL is used for a plurality of (nd1, nd2) in which the sum of the optical distance nd1 and the optical distance nd2 is constant. The total optical radiance in the thickness direction of the substrate 12 when white light was output from the device 10M was calculated.

FIG. 4 is a drawing in which the total luminous flux radiance (au) is mapped to the set of the optical distance nd1 and the optical distance nd2, and is an optical distance nd1 and nd2 dependent map of the total luminous flux radiance. In FIG. 4, the total luminous flux radiance is maximized while changing the thickness of the first light emitting layer 161A and the second light emitting layer 161B so that the sum of the optical distance nd1 and the optical distance nd2 is constant (nd1, nd2). ) Is mapped to the total luminous flux radiance. In FIG. 4, the total luminous flux radiance for 90 sets (nd1, nd2) is mapped.

In FIG. 4, the light-colored region shows that the total luminous flux radiance is large. In this simulation, the peak wavelength λ _R , the peak wavelength λ _G, and the peak wavelength λ _B are 599 nm, 555 nm, and 446 nm, respectively. Therefore, the wavelength range on the vertical axis of FIG. 4 includes λ _G / 4 and its vicinity. Therefore, it can be understood that high light extraction efficiency can be realized by setting the optical distance nd2 to _{an odd multiple of λ G / 4.}

The various embodiments of the present invention have been described above. However, the present invention is not limited to the various embodiments illustrated, and various modifications can be made without departing from the spirit of the present invention.

The light emitting position may be any position in the light emitting layer where charge recombination occurs, and may not be the interface between the first light emitting layer and the second light emitting layer as illustrated.

In a form in which the light emitting layer includes a first light emitting layer and a second light emitting layer, and the organic EL device outputs white light, the light emitted from the second light emitting layer is a complementary color of the light emitted from the first light emitting layer. could be.

The light emitting layer is said to have a laminated structure including two layers of a first light emitting layer and a second light emitting layer, but is not limited to the two layers. For example, a layer for each color to be output may be provided, such as a light emitting layer for red, a light emitting layer for green, and a light emitting layer for blue. The light emitting layer may be one layer containing a plurality of light emitting materials.

In the organic EL device, _{the optical distance between the light emitting position of the wavelength λ R and} the light emitting position of the wavelength λ _B and the first electrode layer (translucent electrode layer) in the intermediate structure is the above-mentioned first. It is within any of the 1st to 3rd ranges, _{and the optical distance between the light emitting position of the wavelength λ R} and the second electrode layer (light reflective electrode layer) is an odd multiple of _{λ R / 4.} , The condition that the optical distance between the light emitting position of the wavelength λ _B and the second electrode layer (light reflective electrode layer) is _{an odd multiple of λ B} / 4 may be further satisfied. If such a condition is satisfied, the viewing angle dependence is further reduced. The _{odd multiple of λ R} / 4 is a concept that includes a certain allowable range (for example, ± 5 (preferably 2.5) nm). Similarly, _{odd multiples of λ B} / 4 are concepts that include a certain tolerance (eg ± 5 (preferably 2.5) nm).

The intermediate structure may include an electron injection layer between the second electrode layer and the electron transport layer (the light emitting layer if the electron transport layer does not exist). The electron injection layer is a functional layer having a function of improving the electron injection efficiency from the second electrode layer to the light emitting layer (specifically, the second light emitting layer in the configuration shown in FIG. 1). The electron injection layer may be an inorganic layer or an organic layer. As the material constituting the electron injection layer, the optimum material is appropriately selected according to the type of the light emitting layer. Examples of materials constituting the electron injection layer include alkali metals, alkaline earth metals, alkali metals and alloys containing one or more of alkaline earth metals, alkali metals or alkali earth metal oxides, and halides. , Carbonate, or a mixture of these substances. Examples of alkali metals, alkali metal oxides, halides, and carbonates include lithium, sodium, potassium, rubidium, cesium, lithium oxide, lithium fluoride, sodium oxide, sodium fluoride, potassium oxide, potassium fluoride. , Rubidium oxide, rubidium fluoride, cesium oxide, cesium fluoride, lithium carbonate and the like. Examples of alkaline earth metals, oxides of alkaline earth metals, halides, and carbonates include magnesium, calcium, barium, strontium, magnesium oxide, magnesium fluoride, calcium oxide, calcium fluoride, and barium oxide. Examples thereof include barium fluoride, strontium oxide, strontium fluoride, magnesium carbonate and the like.

In addition to this, a layer obtained by mixing a conventionally known electron-transporting organic material and an organometallic complex of an alkali metal can be used as an electron injection layer.

The electron injection layer can be formed by a dry film forming method, a plating method, a coating method, or the like. Examples of the dry film forming method and the coating method can be the same as the examples given in the method of forming the first electrode layer. The electron injection layer may be a part of the second electrode layer.

The organic EL device is not limited to a form that emits light from the substrate side, and may be an organic EL device (top emission type organic EL device) that outputs light from the side opposite to the substrate. In this case, the first electrode layer is a reflective electrode layer, and the second electrode layer is a translucent electrode layer. The embodiment in which the first electrode layer is an anode (or a part thereof) and the second electrode layer is a cathode has been described, but the second electrode layer is an anode (or a part thereof) and the first electrode layer is a cathode. There may be.

The example of the light emitting device is not limited to an organic EL device having an intermediate structure, for example, using an organic material for the light emitting layer, and may be, for example, a device in which the light emitting layer is entirely made of an inorganic material.

10 ... Organic EL device (light emitting device), 12 ... Substrate (translucent substrate), 14 ... First electrode layer, 16 ... Intermediate structure, 18 ... Second electrode layer, 20 ... High refractive index layer, 161 ... Light emission layer. 161A ... 1st light emitting layer, 161B ... 2nd light emitting layer, 165 ... Light emitting position.

Claims (8)

With the board
The first electrode layer provided on the substrate and
An intermediate structure provided on the first electrode layer and including a light emitting layer, and
A second electrode layer provided on the intermediate structure and
With
One of the first electrode layer and the second electrode layer is a translucent electrode layer, and the other is a light-reflecting electrode layer.
When the peak wavelength in the color matching function corresponding to green in the XYZ color system is λ _G [nm], between _{the light emitting position of the wavelength λ G in} the intermediate structure and the translucent electrode layer. The optical distance is within one of the first range of 140 nm to 200 nm, the second range of 400 nm to 460 nm, and the third range of 680 nm to 720 nm.
The optical distance between the light emitting position and the light reflecting electrode layer is an odd multiple of _{λ G / 4.}
Luminescent device. The light emitting layer outputs white light.
The light emitting device according to claim 1. The light emitting layer
The first light emitting layer and
A second light emitting layer adjacent to the first light emitting layer and laminated on the first light emitting layer,
Have,
The light emitted from the second light emitting layer is a complementary color of the light emitted from the first light emitting layer.
The light emitting device according to claim 1 or 2.
Luminescent device. The first electrode layer contains silver or a silver alloy.
The light emitting device according to any one of claims 1 to 3. The thickness of the first electrode layer is 8 nm or more and 35 nm or less.
The light emitting device according to claim 4. A high refractive index layer provided between the substrate and the first electrode layer and having a higher refractive index than the substrate is further provided.
The substrate is a translucent substrate and
The first electrode layer is the translucent electrode layer.
The light emitting device according to any one of claims 1 to 4. The optical distance between the light emitting position and the light-reflecting electrode layer is 100 nm or more and 155 nm or less.
The optical device according to any one of claims 1 to 6. When the peak wavelengths in the color matching functions corresponding to red and blue in the XYZ color system are λ _R [nm] and λ _B [nm], respectively, the light emission position and wavelength λ _{of the wavelength λ R in the intermediate structure are The optical distance between each of the light emitting positions of B} and the translucent electrode layer is within any of the first range, the second range, and the third range.
The optical distance between the light emitting position of the wavelength λ _R and the light-reflecting electrode layer is an odd multiple of _{λ R / 4.}
The optical distance between the light emitting position of the wavelength λ _B and the light-reflecting electrode layer is an odd multiple of _{λ B / 4.}
The light emitting device according to any one of claims 1 to 7.

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