JP2005150042A - Organic el light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a top emission type organic EL light emitting element in which light emission efficiency improved without causing multiplex interference while maintaining carrier balance. <P>SOLUTION: In the organic EL light emitting element in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially laminated, the organic EL layer includes a hole injection layer, a reflecting layer to make the positive hole pass through, a hole transfer layer, and an organic light emitting layer in this order. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic EL light emitting device, and more particularly, to a top emission device, and more particularly to an organic EL light emitting device in which the efficiency is improved by controlling interference without breaking the carrier balance.

  Organic EL light-emitting elements have high visibility due to being self-luminous, and excellent impact resistance and ease of handling due to being completely solid elements, and attention is paid to their use as light-emitting elements in various display devices. Has been.

  In recent years, active matrix displays have been actively developed for organic EL displays formed by arranging a plurality of organic EL light emitting elements in a matrix. An active matrix display is formed by forming an organic EL layer and a uniformly formed transparent electrode on a substrate having a plurality of switching elements (such as TFTs or MIMs) connected one-to-one with pixels or sub-pixels. Produced. However, there is a large variation in characteristics between switching elements or between organic EL layers of each pixel or sub-pixel, and at present, it is necessary to provide various drive circuits on the substrate together with the switching elements in order to correct the variation. . The need for such a complex circuit results in an increase in the number of TFTs required to drive a single pixel or subpixel, which in turn reduces the area of the transparent region on the substrate. In such a situation, it seems that the “top emission” method in which light is extracted from the opposite side (upper electrode side) of the substrate is more advantageous than the “bottom emission” method in which light is extracted from the substrate side. It is becoming.

  The structure of the organic EL light-emitting element is based on the structure of an anode / organic EL layer / cathode. The organic EL layer includes an organic light-emitting layer, and if necessary, a hole injection layer, a hole transport layer, and an electron injection. A structure provided with a layer and / or an electron transport layer is known. In such an EL element, the thickness of each layer constituting the organic EL layer, for example, the thickness of each of the hole injection layer, the hole transport layer, the light emitting layer, and the electron injection layer is controlled, and the maximum light extraction efficiency and Many attempts have been made to obtain the highest brightness.

  For example, in an organic EL light emitting device having the structure of a conventional bottom emission type substrate / transparent anode / hole transporting light emitting layer / electron transporting layer / reflective cathode, the film thickness of the electron transporting layer is controlled to 30 to 60 nm. A technique for improving the light extraction efficiency is disclosed (see Patent Document 1). This indicates that the distance between the light emitting layer and the reflective cathode is an important factor. Further, in an organic EL light emitting device having the same configuration, the film thickness of the electron transport layer is controlled, and light generated in the light emitting layer and directed to the substrate is emitted from the light emitting layer and reflected by the reflective cathode. A technique is disclosed in which the light traveling toward the substrate interferes in phase with each other to substantially increase the light from the light-emitting layer and at the same time reduce the viewing angle dependency of luminance (see Patent Document 2). Furthermore, a technique for improving the color purity of light emitted from the element by selecting the optical film thickness of the transparent anode and the organic EL layer is disclosed (see Patent Document 3).

JP-A-4-137485 JP-A-4-328295 Japanese Patent No. 2846571

  When in-phase interference is used, the extraction efficiency for light of a specific wavelength that satisfies the interference condition can be improved, but the extraction efficiency for light of other wavelengths cannot be improved. In order to realize high light extraction efficiency in a wide wavelength range, it is necessary to prevent multiple interference in the wavelength range. In order to prevent the occurrence of multiple interference in a top emission type organic EL light emitting device having the structure of substrate / reflective anode / hole injection transport layer / organic light emitting layer / electron injection transport layer / transparent cathode, the interference is It is necessary to adjust the optical path length of a hole injection transport layer (for example, including a transparent conductive oxide layer, a hole injection layer, a hole transport layer, etc.) existing between the reflective electrode and the organic light emitting layer.

  On the other hand, in the organic EL layer material system currently used, since the electron mobility in the organic EL layer is smaller than the hole mobility, the organic light emitting layer tends to have more holes than electrons. There is. On the other hand, conventionally, the electron injecting and transporting layer is made thin and the hole injecting and transporting layer is made thick to maintain the carrier balance, thereby preventing the light emission efficiency of the organic EL light emitting element from being lowered. Therefore, there is a need for a method for improving the light extraction efficiency in a wide wavelength range while preventing the occurrence of multiple interference and maintaining an appropriate carrier balance.

  In view of the above, it is an object of the present invention to provide a top emission type organic EL light emitting device that can improve the light emission efficiency and the color purity by controlling the interference while maintaining the carrier balance.

  The organic EL light-emitting device according to the first embodiment of the present invention is an organic EL light-emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially stacked. A layer, a reflective layer through which holes pass, a hole transport layer, and a light emitting layer are included in this order. The reflective layer may be formed of a material selected from the group consisting of metals, alloys, conductive polymers, and conductive compounds.

  An organic EL light emitting device according to a second embodiment of the present invention is an organic EL light emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially laminated. A high refractive index layer that allows holes to pass therethrough, a hole transport layer, and a light emitting layer in this order, wherein the high refractive index layer has a higher refractive index than the other layers of the organic EL layer. The high refractive index layer may be formed using a transparent conductive oxide.

  The organic EL light emitting device according to the third embodiment of the present invention is an organic EL light emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially laminated. A first hole layer, a second hole layer having a higher refractive index than the first hole layer, and a light emitting layer in contact with the second hole layer, wherein the first and second hole layers Is arranged between the light emitting layer and the metal anode. The first hole layer may be formed of a high molecular weight organic material, and the second hole layer may be formed of a low molecular weight organic material.

  According to the present invention, it is possible to obtain an organic EL light emitting element which can control interference without destroying the carrier balance and give good luminous efficiency and color purity.

  The organic EL light emitting device of the first embodiment of the present invention is shown in FIG. 1 includes a reflective anode 2, a transparent anode 3, a hole injection layer 4, a reflective layer 5, a hole transport layer 6, an organic light emitting layer 7, an electron transport layer 8, and a buffer layer on a substrate 1. 9 and the transparent cathode 10 are sequentially laminated.

  The reflective anode 2 is preferably a single layer film or a laminated film having a reflectance of 50% or more, preferably 70% or more in the wavelength range of light emitted from the organic EL light emitting layer (preferably the entire visible light region). The reflective anode 2 is formed using a highly reflective metal such as Al, Ag, Mo, W, Ni, Cr, an amorphous alloy such as NiP, NiB, CrP, and CrB, or a microcrystalline alloy such as NiAl. In particular, since the reflective electrode 2 serves as a base for a layer laminated thereon, it is preferably formed using an amorphous alloy or a microcrystalline alloy having good flatness. Particularly preferred is a film in which an ultrathin metal film having a high reflectance is laminated on an amorphous material film (for example, CrB / Ag, CrB / Al). The reflective anode 2 can be formed using any means known in the art such as vapor deposition (resistance heating or electron beam heating), sputtering, ion plating, laser ablation, and the like.

The transparent anode 3 is a layer that may be optionally provided, and using any means known in the art such as sputtering, ion plating, laser ablation, SnO ₂ , In ₂ O ₃ , ITO , IZO, ZnO: Al, and can be formed from a known material including a conductive metal oxide. The transparent anode 3 preferably has a transmittance of 80% or more, more preferably 90% or more with respect to light having a wavelength of 400 to 800 nm. The reflective anode 2 and the transparent anode 3 integrally function as an anode. The reflective anode 2 is a layer provided mainly to provide low electrical resistance, and the transparent anode 3 is a layer provided mainly to provide a work function suitable for hole injection, forming a continuous layer. It is desirable to have a film thickness of 20 nm or more, preferably 20 to 40 nm, sufficient for this purpose.

  The organic EL layer of the organic EL light emitting device of the present embodiment includes a hole injection layer 4, a reflective layer 5, a hole transport layer 6, and an organic light emitting layer 7, and an electron transport layer 8 as necessary. A desirable layer configuration of the organic EL layer is hole injection layer 4 / reflection layer 5 / hole transport layer 6 / organic light emitting layer 7 / electron transport layer 8.

  The hole injection layer 4 is a layer for facilitating injection of holes from the anode (the reflective anode 2 or the transparent anode 3) into the organic material layer. The hole injection layer 4 can be formed using phthalocyanines (such as copper phthalocyanine) or indanthrene compounds. The hole injection layer 4 can be formed using any means known in the art such as vapor deposition.

  The reflective layer 5 is a layer provided between the hole injection layer 4 and the hole transport layer 6. The reflective layer 5 is formed of a material having high reflectivity while allowing holes injected from the anode to pass therethrough. In order not to form a potential barrier against the passage of holes, the reflective layer 5 desirably has a work function of 4.5 eV or more, preferably 4.8 eV or more, more preferably 5.0 eV or more. The reflective layer desirably has a reflectance of 50% or more, more preferably 85% or more, with respect to light in the visible light region. The reflective layer 5 is made of a metal such as Ag, Al, or Rh or an alloy thereof; halogens such as iodine or bromine, arsenic pentafluoride, boron trifluoride, or polyacetylene doped with perchloric acid, polypyrrole, or polyaniline. It can be formed using a conductive polymer; or an electrically conductive compound containing a conductive oxide such as vanadium oxide or molybdenum oxide. The reflective layer 5 desirably has a thickness of 20 nm or more, preferably 20 to 40 nm, sufficient to form a continuous layer.

  The hole transport layer 6 is a layer for transporting holes injected from the anode to the organic light emitting layer 7, and at the same time, a layer for blocking the movement of electrons injected from the cathode. Examples of the material for the hole transport layer 6 include TPD, N, N′-bis (1-naphthyl) -N, N′-diphenylbiphenylamine (α-NPD), 4,4 ′, 4 ″ -tris (N— Includes triarylamine-based materials such as 3-tolyl-N-phenylamino) triphenylamine (m-MTDATA), N, N, N ′, N′-tetrabiphenyl-4,4′-biphenylenediamine (TBPB) A known material can be used, and the hole transport layer 6 can be formed using any means known in the art such as vapor deposition.

  The organic light emitting layer 7 is a layer that emits light by recombination of holes injected from the anode and electrons injected from the cathode. The organic light emitting layer 7 can be formed using any known material. For example, in order to obtain light emission from blue to blue-green, for example, optical brighteners such as benzothiazole series, benzimidazole series, benzoxazole series, metal chelated oxonium compounds, styrylbenzene series compounds, aromatic dimethylidin series Materials such as compounds are preferably used. Alternatively, by adding a dopant (perylene, quinacridones, rubrene, etc.) to a host compound (distyrylarylene compound, TPD, aluminum tris (8-quinolinolate) (Alq), etc.), light in various wavelength ranges is emitted. The organic light emitting layer 7 may be formed.

  The electron transport layer 8 is a layer for transporting electrons injected from the cathode to the organic light-emitting layer 7, and at the same time, is a layer for preventing movement of holes injected from the anode. Examples of the material for the electron transport layer 8 include oxadiazole derivatives such as 2- (4-biphenyl) -5- (pt-butylphenyl) -1,3,4-oxadiazole (PBD), triazole derivatives, Triazine derivatives, phenylquinoxalines, aluminum quinolinol complexes (eg, Alq), and the like can be used. The electron transport layer 8 can be formed using any means known in the art such as vapor deposition.

  Alternatively, each of the hole injection layer 4, the hole transport layer 6, the organic light emitting layer 7, and the electron transport layer 8 is made of a material in which the above low molecular material is dispersed in a polymer, or the above low molecular material is polymerized. You may form using the material chemically combined with the chain. Polymers that can be used include polyesters, polyimides, acrylic resins, epoxy resins, and the like. More preferably, a polyimide formed by applying and heating a material obtained by chemically bonding the above-described low molecular weight material to polyamic acid is used. When such a polymer material is used, each layer can be formed by a known method such as a spin coating method, a casting method, or an LB method.

The buffer layer 9 is a layer for facilitating the injection of electrons from the transparent cathode 10 into the organic material layer and at the same time preventing damage to the organic material layer in the sputtering process used for forming the transparent cathode 10. As a material of the buffer layer 9, an alkali metal, an alkaline earth metal, or an alloy containing them having a work function of less than 4.8 eV, preferably less than 4.0 eV, more preferably less than 3.7 eV can be used. For example, Al, AlLi, Ag, MgAg, AgLi, or the like can be used. Alternatively, a laminate of the above material and an electron injecting transparent material such as an alkali metal or alkaline earth metal fluoride may be used. As the electron injecting transparent material, for example, LiF, MgF ₂ , CaF, NaF, SiO, Sb ₂ O ₃ or the like can be used. In the organic EL light-emitting device of the present invention, in order to extract light from the organic light-emitting layer to the outside through the buffer layer, it is desirable that the film thickness of the buffer layer 9 is 20 nm or less, more preferably 10 nm or less, to impart transparency. . The buffer layer 9 can be formed using any means known in the art such as vapor deposition.

  The transparent cathode 10 can be formed by the same method using the same material as the transparent anode 3. The transparent electrode 3 preferably has a transmittance of 80% or more, more preferably 90% or more with respect to light having a wavelength of 400 to 800 nm. In order to improve luminous efficiency, it is desirable that the transparent cathode 10 has a thickness that provides a sufficiently low resistivity, preferably 30 nm or more, and more preferably within a range of 100 to 300 nm. Moreover, since the film thickness of the transparent electrode 10 also affects interference, the film thickness may be obtained according to interference conditions or experimentally.

  In the organic EL light emitting device of this embodiment, the light emitted from the organic light emitting layer 7 to the anode side is reflected at the interface between the reflective layer 5 and the hole transport layer 6 and the organic light emitting layer 7 to the transparent cathode 10. By not causing multiple interference with the light emitted to the side, it is possible to achieve high light extraction efficiency not only in the characteristic wavelength but also in a wide wavelength range.

  In order not to cause multiple interference, the organic light emitting layer 7 and the hole transporting layer satisfy the following formula (1) with respect to the wavelength λ (400 to 700 nm) of light emitted from the organic light emitting layer. It is necessary to set a film thickness of 6.

(In the formula, n _OEM and d _OEM are the refractive index and film thickness of the organic light emitting layer 7, n _HTL and d _HTL are the refractive index and film thickness of the hole transport layer 6, and m is an integer of 1 or more. is there)

When the refractive indexes n _OEM and n _HTL of the hole transport layer 6 and the organic light emitting layer 7 formed of a low molecular material were measured using an ellipsometer, each refractive index was 1.85 (450 nm), 1.75 ( 530 nm) and 1.72 (620 nm). Further, the organic light emitting layer 7 needs to have a thickness of 20 to 60 nm in order to obtain light having a desired intensity. Therefore, when the wavelength λ is in the range of 400 to 700 nm, it is desirable that the thickness of the hole transport layer 6 be less than 46 nm in order to control interference (prevent multiple interference). Further, in order to smoothly transport holes to the organic light emitting layer 7, the hole transport layer 6 preferably has a thickness of 10 nm or more.

  Further, in the organic EL light emitting device of this embodiment, the balance of carriers injected into the organic light emitting layer 7 is such that the total film thickness of the hole injection layer 4 / reflective layer 5 / hole transport layer 6 and the electron transport layer 8. / Maintained by changing the ratio with the total film thickness of the buffer layer 9. Desirably, the thickness of the hole injection layer 4 is changed to maintain the carrier balance. In the organic EL light emitting device of the present embodiment, the total thickness of the hole injection layer 4 / reflection layer 5 / hole transport layer 6 is in the range of 40 to 260 nm, and the thickness of the hole injection layer 4 is 20 nm. It is desirable to be within a range of ˜240 nm.

  An organic EL light emitting device according to the second embodiment of the present invention is shown in FIG. The organic EL light emitting device shown in FIG. 2 has the same layer configuration as that of the first embodiment except that the high refractive index layer 11 is formed instead of the reflective layer 5. The layers other than the high refractive index layer can be formed from the same material as in the first embodiment.

The high refractive index layer 11 is formed of a material having a high refractive index while allowing holes injected from the anode to pass therethrough. In order not to form a potential barrier against the passage of holes, the high refractive index layer 11 desirably has a work function of 4.5 eV or more, preferably 4.8 eV or more, more preferably 5.0 eV or more. The high refractive index layer 11 preferably has a refractive index of 2.0 or more, preferably 2.0 to 3.0 in the visible light region. The high refractive index layer 11 can be formed using a conductive metal oxide such as SnO ₂ , In ₂ O ₃ , ITO, IZO, ZnO: Al. It is particularly desirable to use IZO having a refractive index of 2.2 (450 nm) and 2.0 (620 nm) when measured with an ellipsometer.

  In the organic EL light emitting device of the present embodiment, the light emitted from the organic light emitting layer 7 to the anode side is reflected by the interface between the hole injection layer 4 and the high refractive index layer 11 and the organic light emitting layer 7 transmits the transparent cathode. By not causing multiple interference with the light emitted to the 10 side, it is possible to ensure color purity and achieve high light extraction efficiency not only in the characteristic wavelength but also in a wide wavelength range.

  In order to prevent multiple interference, the organic light-emitting layer 7 and the hole transport layer satisfy the following formula (2) with respect to the wavelength λ (400 to 700 nm) of the light emitted from the organic light-emitting layer. 6 and the film thickness of the high refractive index layer 11 must be set.

(In the formula, n _OEM and d _OEM are the refractive index and film thickness of the organic light emitting layer 7, n _HTL and d _HTL are the refractive index and film thickness of the hole transport layer 6, and n _TOL and d _TOL are high. (The refractive index and the film thickness of the refractive index layer 11 and m is an integer of 1 or more)

  In the present embodiment, the high refractive index layer 11 desirably has a thickness of 10 to 40 nm, preferably 10 to 30 nm, sufficient to form a continuous layer. Also in this embodiment, it is desirable to control interference by the film thickness of the hole transport layer 6. Although depending on the refractive index and film thickness of the high refractive index layer 11, when the wavelength λ is in the range of 400 to 700 nm, the thickness of the hole transport layer 6 is desirably less than 89 nm. Further, in order to smoothly transport holes to the organic light emitting layer 7, the hole transport layer 6 preferably has a thickness of 10 nm or more.

  In the organic EL light-emitting device of this embodiment, the balance of carriers injected into the organic light-emitting layer 7 is such that the total thickness of the hole injection layer 4 / high refractive index layer 11 / hole transport layer 6 and the electron transport layer 8. / Maintained by changing the ratio with the total film thickness of the buffer layer 9. Desirably, the thickness of the hole injection layer 4 is changed to maintain the carrier balance. In the organic EL light emitting device of this embodiment, the total thickness of the hole injection layer 4 / the high refractive index layer 11 / the hole transport layer 6 is in the range of 40 to 260 nm, and the film thickness of the hole injection layer 4 is. Is preferably in the range of 20 to 240 nm.

  An organic EL light emitting device of the third embodiment of the present invention is shown in FIG. 3 includes a reflective anode 2, a transparent anode 3, a first hole layer 12, a second hole layer 13, an organic light emitting layer 7, an electron transport layer 8, a buffer layer 9 on a substrate 1. It has a structure in which transparent cathodes 10 are sequentially laminated. Each layer excluding the first hole layer 12 and the second hole layer 13 can be formed using the same material as in the first embodiment.

  The first hole layer 12 is a layer formed from a polymer material in which a hole injecting material or a hole transporting material is dispersed in a polymer. As the hole-injecting material to be dispersed, phthalocyanines (such as copper phthalocyanine) or indanthrene compounds can be used. As the hole transporting material to be dispersed, triarylamine compounds such as TPD, α-NPD, m-MTDATA, and TBPB can be used. Moreover, as a polymer which forms a polymeric material, polyester, a polyimide, an acrylic resin, an epoxy resin, etc. are included, More preferably, polyester or a polyimide can be used. Alternatively, the first hole layer 12 may be formed of a polymer material in which the above-described hole injecting material or hole transporting material is chemically bonded to the above polymer molecule. For example, polyimide formed by chemically bonding the above-described hole injecting material or hole transporting material to polyamic acid and heating it can be used. By forming the first hole layer 12 using such a polymer material, the refractive index can be lowered to about 1.5. The first hole layer 12 can be formed by a known method such as a spin coating method, a casting method, or an LB method.

  The second hole layer 13 is a layer formed from a hole injecting material or a hole transporting material, and is preferably a layer formed from a hole transporting material. As the hole transporting material, triarylamine compounds such as TPD, α-NPD, m-MTDATA, and TBPB can be used. Since these materials have a refractive index of 1.85 (450 nm), 1.75 (530 nm), and 1.72 (620 nm), the first hole layer 12 using a polymer material is sufficiently interposed between the materials. It is possible to give a difference in refractive index.

  In the organic EL light emitting device of this embodiment, the refractive index of the second hole layer 13 is made larger than the refractive index of the first hole layer 12, and the first hole layer 12 / second hole layer 13 The light from the organic light emitting layer 7 is reflected at the interface. The refractive index of the second hole layer 13 is desirably 10% or more, preferably 15% or more, more preferably 20% or more larger than the refractive index of the first hole layer 12. The light emitted from the organic light emitting layer 7 to the anode side is reflected by the interface between the first hole layer 12 and the second hole layer 13 and the light emitted from the organic light emitting layer 7 to the transparent cathode 10 side. By avoiding multiple interference between the color wavelength and the wavelength, it is possible to ensure color purity and achieve high light extraction efficiency not only in the characteristic wavelength but also in a wide wavelength range.

  In order to prevent multiple interference, the organic light emitting layer 7 and the second hole are satisfied so as to satisfy the following formula (3) with respect to the wavelength λ (400 to 700 nm) of the light emitted from the organic light emitting layer. It is necessary to set the film thickness of the layer 13.

(In the formula, n _OEM and d _OEM are the refractive index and film thickness of the organic light emitting layer 7, n _SHL and d _SHL are the refractive index and film thickness of the second hole layer 13, and m is an integer of 1 or more. Is)

  Since the organic light emitting layer 7 needs to have a thickness of 20 to 60 nm in order to obtain light having a desired intensity, interference is controlled by the film thickness of the second hole layer 13 in this embodiment as well (multiple interference is reduced). To prevent). When the wavelength λ is in the range of 400 to 700 nm, it is desirable that the thickness of the second hole layer 13 is less than 100 nm in order to control interference.

  On the other hand, the first hole layer 12 can form a continuous layer to form a reflective surface, and has a film thickness sufficient to maintain carrier balance in cooperation with the second hole layer 13. It is preferable. The first hole layer 12 has a thickness of 20 to 200 nm.

  In the above embodiment, the organic EL light emitting element having a single light emitting part has been described. However, the organic EL light emitting element of the present invention may be an element in which a plurality of independent light emitting parts are arranged in a matrix. . For example, as shown in FIG. 4, an active matrix driving type organic EL light emitting element can be formed using a switching element such as TFT or MIM. In the element of FIG. 4, a plurality of TFTs 21 are provided on a substrate, and a planarization insulating film 22 is provided so as to cover the TFTs. The sources of the plurality of TFTs 21 and the reflective anodes 2 divided into a plurality of portions are connected in a one-to-one relationship through the openings provided in the planarization insulating film 22. Similarly, a transparent anode 3 divided into a plurality of portions may be provided on the reflective anode 2. A hole injection layer 4, a reflection layer 5, a hole transport layer 6, an organic light emitting layer 7, an electron transport layer 8, a buffer layer 9, and a transparent cathode 10 are further stacked thereon. The transparent cathode 10 in the element of FIG. 4 is a single electrode that is not divided into a plurality of portions. Although the structure of the first embodiment with the constituent layers of the transparent anode 3 or higher is shown in FIG. 4, it is needless to say that the structures of the second and third embodiments may be used.

  Alternatively, each of the reflective anode, the transparent anode if present, and the transparent cathode can be composed of a plurality of portions having a line shape to form a passive matrix drive type organic EL light emitting device. is there. In this case, the line shape of the reflective anode extends in a direction orthogonal to the direction in which the line shape of the transparent cathode extends. Each of the line-shaped portions of the transparent anode is formed on the line-shaped portion of the reflective anode.

  Further, as described above, an organic EL display may be formed by combining an organic EL light emitting element having a plurality of independent light emitting portions and a color filter or a color conversion filter. A multicolor display can be formed by using a color filter or a color conversion filter having a plurality of types of color transmission parts or color conversion parts (for example, red, green, and blue). The color filter and the color conversion filter may be laminated on the transparent cathode 10 of the organic EL light emitting device of the present invention. Alternatively, a color filter and a color conversion filter separately formed on another transparent substrate may be bonded to the organic EL light emitting device of the present invention to form a multicolor display.

(Example 1)
A reflective anode 2 was formed by depositing CrB having a thickness of 100 nm on a glass substrate by a DC sputtering method. Deposition by the DC sputtering method was performed at room temperature using Ar as the sputtering gas and applying a sputtering power of 300 W. Subsequently, the reflective anode 2 was dried (150 ° C.) and UV-treated (room temperature and 150 ° C.).

The substrate on which the reflective anode 2 was formed was placed in a seven-chamber vapor deposition apparatus, and an organic EL layer was formed. During film formation, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁵ Pa. As the evaporation source, a resistance heating crucible made of quartz, Mo, BN, or PBN was used depending on the material of each layer. A hole injection layer 4, a reflection layer 5, a hole transport layer 6, an organic light emitting layer 7, an electron transport layer 8, a buffer layer 9, and a cathode 10 were sequentially formed without breaking the vacuum. The vapor deposition rate of each organic material was 2-4 liters / s. The hole injection layer 4 is copper phthalocyanine (CuPc) having a thickness of 60 nm, the reflection layer 5 is Ag having a thickness of 20 nm (reflectance 95%), and the hole transport layer 6 is TBPB having a thickness of 20 nm (refractive index 1.. 85), 40 nm-thick 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVBi, refractive index 1.85) as the organic light-emitting layer 7, and 20 nm-thick Alq as the electron transport layer 8. Lamination was performed by vapor deposition. Subsequently, MgAg having a thickness of 5 nm was stacked as the buffer layer 9 by vapor deposition. Next, IZO (In ₂ O ₃ -10% ZnO) as a sputtering target and IZO with a film thickness of 30 nm were laminated by a DC sputtering method using Ar as a sputtering gas to obtain a transparent cathode 10.

  The device fabricated as described above was moved to a glove box (both oxygen and moisture concentrations of several ppm or less) without being exposed to the atmosphere, and a getter agent was applied to a portion where the laminate was not provided. An ultraviolet curable adhesive was applied to the peripheral edge of the substrate outside the agent, and UV sealing was performed using a glass substrate.

(Example 2)
A reflective anode 2 was formed by depositing CrB having a thickness of 100 nm on a glass substrate by a DC sputtering method. Deposition by the DC sputtering method was performed at room temperature using Ar as the sputtering gas and applying a sputtering power of 300 W. Subsequently, the reflective anode 2 was dried (150 ° C.) and UV-treated (room temperature and 150 ° C.).

The substrate on which the reflective anode 2 was formed was placed in a seven-chamber vapor deposition apparatus, and an organic EL layer was formed. During film formation, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁵ Pa. As the evaporation source, a resistance heating crucible made of quartz, Mo, BN, or PBN was used depending on the material of each layer. A hole injection layer 4, a high refractive index layer 11, a hole transport layer 6, an organic light emitting layer 7, an electron transport layer 8, a buffer layer 9, and a cathode 10 were sequentially formed without breaking the vacuum. The vapor deposition rate of each organic material was 2-4 liters / s. 60 nm thick copper phthalocyanine (CuPc) as the hole injection layer 4, 10 nm thick IZO (refractive index 2.2) as the high refractive index layer 11, and 20 nm thick TBPB as the hole transport layer 6, A 40 nm thick DPVBi as the organic light emitting layer 7 and a 20 nm thick Alq as the electron transport layer 8 were laminated by vapor deposition. Subsequently, MgAg having a thickness of 5 nm was stacked as the buffer layer 9 by vapor deposition. Next, IZO (In ₂ O ₃ -10% ZnO) as a sputtering target and IZO with a film thickness of 30 nm were laminated by a DC sputtering method using Ar as a sputtering gas to obtain a transparent cathode 10.

  The device fabricated as described above was moved to a glove box (both oxygen and moisture concentrations of several ppm or less) without being exposed to the atmosphere, and a getter agent was applied to a portion where the laminate was not provided. An ultraviolet curable adhesive was applied to the peripheral edge of the substrate outside the agent, and UV sealing was performed using a glass substrate.

(Example 3)
A reflective anode 2 was formed by depositing CrB having a thickness of 100 nm on a glass substrate by a DC sputtering method. Deposition by the DC sputtering method was performed at room temperature using Ar as the sputtering gas and applying a sputtering power of 300 W. Subsequently, the reflective anode 2 was dried (150 ° C.) and UV-treated (room temperature and 150 ° C.).

  Next, on the reflective anode 2, a polyester in which CuPc was molecularly dispersed was applied by a spin coating method to form a first hole layer 12 (refractive index 1.5) having a thickness of 40 nm. The first hole layer 12 contained CuPc in a content of 50% by mass based on its total weight.

The substrate on which the first hole layer 12 was formed was placed in a seven-chamber vapor deposition apparatus, and an organic EL layer was formed. During film formation, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁵ Pa. As the evaporation source, a resistance heating crucible made of quartz, Mo, BN, or PBN was used depending on the material of each layer. The second hole layer 13, the organic light emitting layer 7, the electron transport layer 8, the buffer layer 9, and the cathode 10 were sequentially formed without breaking the vacuum. The vapor deposition rate of each organic material was set to 2-4 Å / s. TBPB having a thickness of 20 nm was stacked as the second hole layer 13, DPVBi having a thickness of 40 nm was stacked as the organic light emitting layer 7, and Alq having a thickness of 20 nm was stacked as the electron transport layer 8 by a deposition method. Subsequently, MgAg having a thickness of 5 nm was stacked as the buffer layer 9 by vapor deposition. Next, IZO (In ₂ O ₃ -10% ZnO) as a sputtering target and IZO with a film thickness of 30 nm were laminated by a DC sputtering method using Ar as a sputtering gas to obtain a transparent cathode 10.

  The device fabricated as described above was moved to a glove box (oxygen concentration, moisture concentration of several ppm or less) without being exposed to the atmosphere, and a getter agent was applied to a portion where the above laminate was not provided. An ultraviolet curable adhesive was applied to the peripheral edge of the substrate outside the agent, and UV sealing was performed using a glass substrate.

(Comparative Example 1)
An organic EL light emitting device was formed in the same manner as in Example 1 except that the thickness of the hole injection layer 4 and the hole transport layer 6 was set to 10 nm and the high refractive index layer 11 was not formed. . The film thickness of each layer of the element of this example is for controlling interference to obtain good color purity.

(Comparative Example 2)
An organic EL light emitting device was formed in the same manner as in Example 1 except that the high refractive index layer 11 was not formed. The film thickness of each layer of the element of this example is for obtaining a good carrier balance.

(Evaluation)
The organic EL light-emitting devices of Examples 1 and 2 and Comparative Examples 1 and 2 were caused to emit light by applying a voltage that passed a current having a current density of 1.0 × 10 ⁻² A / cm ² . Luminance and spectrum were measured. The film thicknesses of the layers constituting the organic EL layer are shown in Table 1, the current density and luminance of each organic EL light emitting element are shown in Table 2, and the emission spectrum of each organic EL light emitting element is shown in FIG. Note that the emission spectrum shown in FIG. 5 is normalized with the luminance at the maximum emission wavelength of each element as 1.0.

  The organic EL light-emitting device of Comparative Example 1 gave the desired emission spectrum equivalent to the devices of Example 1 and Example 2, but the luminance was significantly reduced and it was found that the efficiency was reduced. This is presumably because the balance of carriers injected into the organic light emitting layer is lost.

  On the other hand, the organic EL light emitting device of Comparative Example 2 did not give a desired emission spectrum. This is presumably because the interference control was insufficient and the light component on the short wavelength side was not emitted to the outside. Further, since a part of the light emission could not be extracted, the luminance (that is, efficiency) slightly decreased as compared with the elements of Example 1 and Example 2.

  Compared with the device of the comparative example, the organic EL light emitting devices of Examples 1 to 3 according to the present invention gave good efficiency together with a desired spectrum. This is presumably because good carrier balance and interference control could be achieved by providing a high refractive index layer or adjusting the refractive index of the material.

It is a schematic sectional drawing which shows the organic EL light emitting element of the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the organic EL light emitting element of the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the organic EL light emitting element of the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the active matrix drive type organic electroluminescent light emitting element of this invention. It is a graph which shows the emission spectrum of the organic electroluminescent light emitting element of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Reflective anode 3 Transparent anode 4 Hole injection layer 5 Reflective layer 6 Hole transport layer 7 Organic light emitting layer 8 Electron transport layer 9 Buffer layer 10 Transparent cathode 11 High refractive index layer 12 First hole layer 13 Second positive layer Pore layer 21 TFT
22 Planarized insulating film

Claims (8)

  In the organic EL light emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially laminated, the organic EL layer includes a hole injection layer, a reflective layer that allows holes to pass through, a hole transport layer, and An organic EL light emitting device comprising organic light emitting layers in this order. When the refractive index and film thickness of the organic light emitting layer are n _OEM and d _OEM, and the refractive index and film thickness of the hole transport layer are n _HTL and d _HTL , λ is in the range of 400 to 700 nm. for,

The organic EL light emitting device according to claim 1, wherein the relationship is satisfied.   2. The organic EL light emitting device according to claim 1, wherein the reflective layer is made of a material selected from the group consisting of metals, alloys, conductive polymers, and conductive compounds.   In an organic EL light emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially stacked, the organic EL layer is a hole injection layer, a high refractive index layer that allows holes to pass through, and hole transport. An organic EL light emitting device comprising a layer and an organic light emitting layer in this order, wherein the high refractive index layer has a higher refractive index than other layers of the organic EL layer.   The organic EL light-emitting element according to claim 4, wherein the high refractive index layer is formed of a transparent conductive oxide. The refractive index and film thickness of the organic light emitting layer are n _OEM and d _OEM , the refractive index and film thickness of the hole transport layer are n _HTL and d _HTL, and the refractive index and film thickness of the high refractive layer are n _TOL. , D _TOL , for λ in the range of 400-700 nm,

The organic EL light emitting device according to claim 4, wherein the relationship is satisfied.   In the organic EL light emitting device in which a substrate, a metal anode, an organic EL layer, and a transparent cathode are sequentially laminated, the organic EL layer includes a first hole layer formed of a polymer material, a first positive layer, and a first positive layer. A second hole layer having a higher refractive index than the hole layer; and an organic light emitting layer in contact with the second hole layer, wherein the first and second hole layers are the light emitting layer and the metal. An organic EL light emitting device, which is disposed between an anode and an anode. Wherein the refractive index and thickness of the light-emitting layer _{n OEM,} and _{d OEM,} the second hole-refractive index of the layer and the thickness _{n SHL,} when the _{d SHL,} the λ in the range of 400~700nm for,

The organic EL light-emitting element according to claim 7, wherein the relationship is satisfied.

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