JP2011096406A - Light emitting element, light emitting device, display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element, along with a light emitting device, a display device, and electronic equipment equipped with the same, having superior emission characteristic (emission efficiency, low drive voltage) and long emission life. <P>SOLUTION: The light emitting element 1 includes a positive electrode 3, a negative electrode 8, a first light emitting layer 42 provided between the positive electrode 3 and the negative electrode 8, a second light emitting layer 62 provided between the negative electrode 8 and the first light emitting layer 42, an electron suction layer 54 which is provided between the first light emitting layer 42 and the second light emitting layer 62 and has an electron suction property, an electron transportation layer 51 which is provided between the first light emitting layer 42 and the electron suction layer 54 and has electron transportation property, a diffusion preventing layer 52 which is provided between the electron suction layer 54 and the electron transportation layer 51 to prevent diffusion of material between these layers. A carrier generation layer 5 is provided to generate positive hole and electron. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  An organic electroluminescence element (so-called organic EL element) is a light emitting element having a structure in which at least one light emitting organic layer is interposed between an anode and a cathode. In such a light-emitting element, when an electric field is applied between the cathode and the anode, electrons are injected from the cathode side into the light-emitting layer and holes are injected from the anode side. The excitons are generated by the recombination of holes with holes, and when the excitons return to the ground state, the energy is released as light.

As such a light-emitting element, for example, one having two or more light-emitting layers between a cathode and an anode and an intermediate layer (carrier generation layer) provided between these light-emitting layers is known. (For example, refer to Patent Document 1).
In such a light emitting device, an electric field is applied between the anode and the cathode, whereby electrons and holes are generated from the intermediate layer and supplied to the adjacent light emitting layer. Therefore, in addition to holes and electrons supplied from the anode and the cathode, holes and electrons supplied from the intermediate layer can be used for light emission of each light emitting layer. Such a light-emitting element can emit light with higher luminance than a light-emitting element having a single light-emitting layer, and is excellent in light emission efficiency. In addition, the light emitting layer can emit light with relatively high luminance even when used at a lower current than a light emitting element having a single light emitting layer, so that the light emitting element is not easily deteriorated and, as a result, has a long light emission lifetime. .

In the light-emitting element described in Patent Document 1, a layer composed of an electron transporting material doped with an electron donor material and a layer composed of a hole transporting material doped with an electron acceptor material are stacked. By using the intermediate layer, the amount of carriers generated in the intermediate layer is increased and the driving voltage of the light emitting element is reduced.
However, the light emitting device according to Patent Document 1 has a problem in that the dopant material is diffused between two layers constituting the intermediate layer, and as a result, the carrier generation layer in the intermediate layer is reduced. For this reason, the conventional light emitting device cannot sufficiently extend its life.

JP 2007-598448 A

  An object of the present invention is to provide a light emitting element having excellent light emission characteristics (light emission efficiency, low driving voltage) and a long light emission lifetime, a light emitting device including the light emitting element, a display device, and an electronic apparatus.

Such an object is achieved by the present invention described below.
The light emitting device of the present invention comprises an anode,
A cathode,
A first light emitting layer that is provided between the anode and the cathode and emits light when energized between the anode and the cathode;
A second light emitting layer that is provided between the cathode and the first light emitting layer and emits light when energized between the anode and the cathode;
Provided between the first light-emitting layer and the second light-emitting layer, and provided between the first light-emitting layer and the electron-withdrawing layer. Having an electron transport layer, and a diffusion prevention layer that is provided between the electron withdrawing layer and the electron transport layer and prevents diffusion of a material between these layers, and generates holes and electrons. And a carrier generation layer.
Accordingly, each of the first light-emitting layer and the second light-emitting layer can emit light, so that the light emission efficiency of the light-emitting element can be improved and the driving voltage can be reduced as compared with a light-emitting element having only one light-emitting layer. Can be reduced.
In particular, since the diffusion preventing layer is provided between the electron withdrawing layer and the electron transporting layer, it is possible to prevent the material from being diffused between the electron withdrawing layer and the electron transporting layer due to heat generation of the light emitting element. Therefore, the carrier generation layer can stably generate holes and electrons over a long period of time. As a result, the lifetime of the light emitting element can be extended.

In the light emitting device of the present invention, the electron transport layer preferably includes an electron transport material and an electron donor material.
Thereby, the electrons attracted by the electron withdrawing layer can be efficiently injected into the electron transporting layer and efficiently transported to the anode side through the electron transporting layer.
In the light emitting device of the present invention, it is preferable that the diffusion prevention layer is configured to include an electron transporting material without including an electron donor material.
Thereby, the electrons attracted by the electron withdrawing layer can be efficiently transported to the electron transporting layer through the diffusion preventing layer, and the electron donor material can be prevented from diffusing into the electron withdrawing layer.

In the light emitting device of the present invention, the electron donor material is preferably an alkali metal or an alkali metal compound.
Thereby, the electrons attracted by the electron withdrawing layer can be efficiently injected into the electron transporting layer and efficiently transported to the anode side through the electron transporting layer.
In the light emitting device of the present invention, the carrier generation layer is provided between the diffusion preventing layer and the electron withdrawing layer, and includes an electron injection layer made of an electron injecting material without including the electron transporting material. It is preferable to provide.
Thereby, the electrons attracted by the electron withdrawing layer can be efficiently injected into the diffusion preventing layer.

In the light emitting device of the present invention, it is preferable that the electron injection layer is provided so as to have a portion that exists in a plane direction and a portion that does not exist in contact with the electron withdrawing layer.
Thereby, it is possible to efficiently inject electrons attracted by the electron withdrawing layer into the diffusion preventing layer while preventing an increase in driving voltage of the light emitting element.
In the light emitting device of the present invention, the average thickness of the electron injection layer is preferably 0.2 to 1.0 nm.
When an electron injection layer is formed using a vacuum deposition method or the like so as to have such a thickness, an electron injection layer having a portion that exists in the plane direction and a portion that does not exist can be obtained relatively easily and reliably. .

In the light emitting device of the present invention, the average thickness of the diffusion preventing layer is preferably 10 to 30 nm.
Thereby, the diffusion preventing layer can prevent the diffusion of the material between the electron withdrawing layer and the electron transporting layer while suppressing the driving voltage of the light emitting element.
In the light emitting device of the present invention, it is preferable that the electron withdrawing layer includes an organic cyanide compound having an aromatic ring.
An organic cyanide compound having an aromatic ring has excellent electron withdrawing properties. Therefore, the amount of holes and electrons generated in the carrier generation layer can be increased by configuring the electron withdrawing layer by including an organic cyanide compound having an aromatic ring.

In the light emitting device of the present invention, the organic cyanide compound is preferably a hexaazatriphenylene derivative.
The hexaazatriphenylene derivative has particularly excellent electron withdrawing properties.
In the light emitting device of the present invention, a hole transporting layer having a hole transporting property may be provided between the second light emitting layer and the carrier generating layer so as to be in contact with the electron withdrawing layer. preferable.
Thereby, the electron withdrawing layer can efficiently withdraw electrons from the hole transport layer. As a result, the amount of holes and electrons generated in the carrier generation layer can be increased.

The light-emitting device of the present invention includes the light-emitting element of the present invention.
Accordingly, a light emitting device having excellent light emission characteristics (light emission efficiency, low driving voltage) and a long light emission lifetime can be provided.
The display device of the present invention includes the light emitting device of the present invention.
Accordingly, it is possible to provide a display device that has excellent light emission characteristics (light emission efficiency, low driving voltage) and a long light emission lifetime and can display a high-quality image over a long period of time.
An electronic apparatus according to the present invention includes the display device according to the present invention.
Accordingly, an electronic device that has excellent light emission characteristics (light emission efficiency, low driving voltage) and a long light emission lifetime and can display high-quality images over a long period of time can be provided.

It is a figure which shows typically the longitudinal cross-section of the light emitting element concerning suitable embodiment of this invention. It is a longitudinal cross-sectional view which shows embodiment of the display apparatus to which the display apparatus of this invention is applied. 1 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which an electronic apparatus of the present invention is applied. It is a perspective view which shows the structure of the mobile telephone (PHS is also included) to which the electronic device of this invention is applied. It is a perspective view which shows the structure of the digital still camera to which the electronic device of this invention is applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a light-emitting element, a display device, and an electronic device of the invention will be described with reference to the accompanying drawings.
FIG. 1 schematically shows a longitudinal section of a light emitting device according to a preferred embodiment of the present invention. In the following description, for convenience of explanation, the upper side in FIG. 1 will be described as “upper” and the lower side as “lower”.
Such a light emitting element (electroluminescence element) 1 includes an anode 3, a first light emitting part (first light emitting unit) 4, a carrier generation layer 5, a second light emitting part (second light emitting unit) 6, The electron injection layer 7 and the cathode 8 are laminated in this order.
In other words, the light-emitting element 1 includes a laminate 15 in which the first light-emitting portion 4, the carrier generation layer 5, the second light-emitting portion 6, and the electron injection layer 7 are laminated in this order between two electrodes (anode 3 and the cathode 8).

The first light-emitting portion 4 is a laminate in which a hole transport layer 41, a first light-emitting layer 42, and an electron transport layer 43 are laminated in this order from the anode 3 side to the cathode 8 side. The second light emitting unit 6 is a stacked body in which a hole transport layer 61, a second light emitting layer 62, and an electron transport layer 63 are stacked in this order from the anode 3 side to the cathode 8 side.
The entire light-emitting element 1 is provided on the substrate 2 and is sealed with a sealing member 9.

In such a light emitting element 1, carriers (electrons and holes) are generated in the carrier generation layer 5 by applying a driving voltage between the anode 3 and the cathode 8. Then, holes are supplied (injected) from the anode 3 side to the first light emitting layer 42, and electrons are supplied from the carrier generation layer 5. In addition, electrons are supplied (injected) from the cathode 8 side to the second light emitting layer 62, and holes are supplied (injected) from the carrier generation layer 5. As a result, holes and electrons recombine in each light emitting layer, and excitons (excitons) are generated by the energy released during the recombination, and energy (fluorescence or phosphorescence) is generated when the excitons return to the ground state. ) Is emitted (emitted).
In this way, the first light emitting layer 42 and the second light emitting layer 62 can each emit light. Therefore, such a light-emitting element 1 can improve the light emission efficiency and reduce the driving voltage as compared with a light-emitting element having only one light-emitting layer.

The substrate 2 supports the anode 3. Since the light-emitting element 1 of the present embodiment is configured to extract light from the substrate 2 side (bottom emission type), the substrate 2 and the anode 3 are substantially transparent (colorless transparent, colored transparent, or translucent), respectively. Has been.
Examples of the constituent material of the substrate 2 include resin materials such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate, quartz glass, and soda glass. Such glass materials can be used, and one or more of these can be used in combination.
Although the average thickness of such a board | substrate 2 is not specifically limited, It is preferable that it is about 0.1-30 mm, and it is more preferable that it is about 0.1-10 mm.

In the case where the light emitting element 1 is configured to extract light from the side opposite to the substrate 2 (top emission type), the substrate 2 can be either a transparent substrate or an opaque substrate.
Examples of the opaque substrate include a substrate made of a ceramic material such as alumina, an oxide film (insulating film) formed on the surface of a metal substrate such as stainless steel, and a substrate made of a resin material. It is done.

Hereinafter, each part which comprises the light emitting element 1 is demonstrated sequentially.
[anode]
The anode 3 is an electrode that injects holes into the first light emitting unit 4 described later. As a constituent material of the anode 3, it is preferable to use a material having a large work function and excellent conductivity.
Examples of the constituent material of the anode 3 include oxides such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , and Al-containing ZnO, Au, Pt, and Ag. Cu, alloys containing these, and the like can be used, and one or more of these can be used in combination.
The average thickness of the anode 3 is not particularly limited, but is preferably 10 to 200 nm, and more preferably 50 to 150 nm.

[First light emitting unit]
As described above, the first light emitting unit 4 includes the hole transport layer 41, the first light emitting layer 42, and the electron transport layer 43.
(Hole transport layer)
The hole transport layer 41 has a function of transporting holes injected from the anode 3 to the first light emitting layer 42.

  As the constituent material of the hole transport layer 41, various p-type polymer materials and various p-type low-molecular materials can be used alone or in combination. For example, N, N ′ shown in the following chemical formula 1 -Di (1-naphthyl) -N, N'-diphenyl-1,1'-diphenyl-4,4'-diamine (NPD), N, N'-diphenyl-N, N'-bis (3-methylphenyl) ) -1,1′-diphenyl-4,4′-diamine (TPD) and other tetraarylbenzidine derivatives, tetraaryldiaminofluorene compounds or derivatives thereof (amine compounds), etc., and one of these or Two or more kinds can be used in combination.

Among the above-mentioned, the hole transport material preferably has a benzidine structure, and more preferably tetraarylbenzidine or a derivative thereof. Thereby, holes are efficiently injected from the anode into the hole transport layer 41, and holes can be efficiently transported to the first light emitting layer 42.
The average thickness of such a hole transport layer 41 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 10 to 100 nm.

(First light emitting layer)
The first light emitting layer 42 includes a light emitting material.
In the luminescent material, electrons are supplied (injected) from the cathode 8 side, and holes are supplied (injected) from the anode 3 side, whereby the holes and electrons are recombined and released upon this recombination. Exciton (exciton) is generated by the generated energy, and energy (fluorescence or phosphorescence) is emitted (emitted) when the exciton returns to the ground state.
Such a light-emitting material is not particularly limited, and various fluorescent materials and various phosphorescent materials can be used alone or in combination of two or more.

  Examples of the red fluorescent material include perylene derivatives such as tetraaryldiindenoperylene derivatives shown in the following chemical formula 2, europium complexes, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, porphyrin derivatives, Nile red, 2- (1 , 1-dimethylethyl) -6- (2- (2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H-benzo (ij) quinolizin-9-yl) ethenyl) -4H-pyran-4H-ylidene) propanedinitrile (DCJTB), 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), and the like.

  Examples of blue fluorescent materials include distyryldiamine derivatives, distyryl derivatives, fluoranthene derivatives, pyrene derivatives, perylene and perylene derivatives, anthracene derivatives, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, chrysene derivatives, phenanthrene derivatives, dianthrene derivatives, Styrylbenzene derivative, tetraphenylbutadiene, 4,4′-bis (9-ethyl-3-carbazovinylene) -1,1′-biphenyl (BCzVBi), poly [(9.9-dioctylfluorene-2,7-diyl) -Co- (2,5-dimethoxybenzene-1,4-diyl)], poly [(9,9-dihexyloxyfluorene-2,7-diyl) -ortho-co- (2-methoxy-5- {2 -Ethoxyhexyloxy} phenylene-1 4-diyl)], poly [(9,9-dioctyl-2,7-diyl) - co - (ethyl benzene)], BD102 (product name, include Idemitsu Kosan Co., Ltd.).

  Examples of green fluorescent materials include coumarin derivatives, quinacridone derivatives, 9,10-bis [(9-ethyl-3-carbazole) -vinylenyl] -anthracene, poly (9,9-dihexyl-2,7-vinylene full) Orenylene), poly [(9,9-dioctylfluorene-2,7-diyl) -co- (1,4-diphenylene-vinylene-2-methoxy-5- {2-ethylhexyloxy} benzene)], poly [ (9,9-dioctyl-2,7-divinylenefluorenylene) -ortho-co- (2-methoxy-5- (2-ethoxylhexyloxy) -1,4-phenylene)] and the like.

The yellow fluorescent material is, for example, a compound having a naphthacene skeleton such as a rubrene-based material, in which an aryl group (preferably a phenyl group) is substituted at any position (preferably 2 to 6) with an aryl group (preferably a phenyl group). Compounds, monoindenoperylene derivatives and the like can be used.
Examples of the red phosphorescent material include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. At least one of the ligands of these metal complexes includes a phenylpyridine skeleton, a bipyridyl skeleton, and a porphyrin skeleton. And the like. More specifically, tris (1-phenylisoquinoline) iridium, bis [2- (2′-benzo [4,5-α] thienyl) pyridinate-N, C ³ ′] iridium (acetylacetonate) (btp2Ir ( acac)), 2,3,7,8,12,13,17,18-octaethyl-12H, 23H-porphyrin-platinum (II), bis [2- (2′-benzo [4,5-α] thienyl ) Pyridinate-N, C ³ '] iridium, bis (2-phenylpyridine) iridium (acetylacetonate).

Examples of the blue phosphorescent material include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. More specifically, bis [4,6-difluorophenyl pyridinium sulfonate -N, ^{C 2} '] - picolinate - iridium, tris [2- (2,4-difluorophenyl) pyridinate -N, ^{C 2']} iridium , bis [2- (3,5-trifluoromethyl) pyridinate -N, ^{C 2} '] - picolinate - iridium, bis (4,6-difluorophenyl pyridinium sulfonate -N, ^{C 2')} iridium (acetylacetonate ).

  Examples of the green phosphorescent material include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. Among these, at least one of the ligands of these metal complexes preferably has a phenylpyridine skeleton, a bipyridyl skeleton, a porphyrin skeleton, or the like. More specifically, fac-tris (2-phenylpyridine) iridium (Ir (ppy) 3), bis (2-phenylpyridinate-N, C2 ′) iridium (acetylacetonate), fac-tris [5 -Fluoro-2- (5-trifluoromethyl-2-pyridine) phenyl-C, N] iridium.

In addition to the light emitting material, the first light emitting layer 42 may include a host material using the light emitting material as a guest material. Such a first light emitting layer 42 can be formed, for example, by doping a host material with a light emitting material as a guest material as a dopant.
A host material that uses a light-emitting material as a guest material recombines holes and electrons to generate excitons, and the exciton energy is transferred to the light-emitting material (Felster transfer or Dexter transfer) to emit light. Has the function of exciting the material.

Such a host material is not particularly limited, but when the light emitting material is a fluorescent material, for example, a naphthacene system such as rubrene and its derivatives, distyrylarylene derivatives, and bis p-biphenylnaphthacene shown in the following chemical formula 3 Materials, anthracene materials, perylene derivatives such as bis-orthobiphenylyl perylene, pyrene derivatives such as tetraphenylpyrene, distyrylbenzene derivatives, stilbene derivatives, distyrylamine derivatives, bis (2-methyl-8-quinolinolato) (p -Phenylphenolato) aluminum (BAlq), quinolinolato metal complexes such as tris (8-quinolinolato) aluminum complex (Alq ₃ ), triarylamine derivatives such as tetraphenylamine tetramers, arylamine derivatives, oxadiazole Derivatives, Derivatives, carbazole derivatives, oligothiophene derivatives, benzopyran derivatives, triazole derivatives, benzoxazole derivatives, benzothiazole derivatives, quinoline derivatives, coronene derivatives, amine compounds, 4,4'-bis (2,2'-diphenylvinyl) biphenyl (DPVBi), IDE120 (product name, manufactured by Idemitsu Kosan Co., Ltd.) and the like can be mentioned, and one or more of these can be used in combination. Preferably, IDE120 (made by Idemitsu Kosan Co., Ltd.), anthracene-based material, and dianthracene-based material are preferable when the light-emitting material is blue or green, and rubrene or rubrene derivative, naphthacene-based material when the light-emitting material is red, Perylene derivatives are preferred.

  As the host material, when the light-emitting material includes a phosphorescent material, for example, 3-phenyl-4- (1′-naphthyl) -5-phenylcarbazole, 4,4′-N, N′-dicarbazole biphenyl ( Quinolinolato metal complexes such as carbazole derivatives such as CBP), phenanthroline derivatives, triazole derivatives, tris (8-quinolinolato) aluminum (Alq), bis- (2-methyl-8-quinolinolato) -4- (phenylphenolato) aluminum N-dicarbazolyl-3,5-benzene, poly (9-vinylcarbazole), 4,4 ′, 4 ″ -tris (9-carbazolyl) triphenylamine, 4,4′-bis (9-carbazolyl)- Carbarisol group-containing compounds such as 2,2′-dimethylbiphenyl, 2,9-dimethyl-4,7-diphe Le-1,10-phenanthroline (BCP) and the like, it may be used singly or in combination of two or more of them.

When the light emitting material (guest material) and the host material as described above are used, the content (doping amount) of the light emitting material in the first light emitting layer 42 is preferably 0.1 to 10 wt%. More preferably, it is 5 to 5 wt%. Luminous efficiency can be optimized by setting the content of the light emitting material within such a range.
The average thickness of the first light emitting layer 42 is not particularly limited, but is preferably 10 to 100 nm, more preferably 10 to 70 nm, and further preferably 10 to 50 nm.
In the present embodiment, the first light emitting layer is described as an example having a single light emitting layer, but the first light emitting layer is a laminated body provided with a plurality of light emitting layers. Also good. In this case, the light emission colors of the plurality of light emitting layers may be the same or different. In the case where the first light-emitting layer has a plurality of light-emitting layers, an intermediate layer may be provided between the light-emitting layers.

(Electron transport layer)
The electron transport layer 43 has a function of transporting electrons injected from the carrier generation layer 5 to the first light emitting layer 42. In addition, the electron transport layer 43 blocks holes that have passed through the first light-emitting layer 42, thereby inhibiting the reduction of the Li compound in the carrier generation layer 5, which will be described later, by the holes, or degrading the carrier generation layer 5. It has a function to prevent it.

As a constituent material (electron transport material) of the electron transport layer 43, for example, 8-quinolinol or its derivative such as tris (8-quinolinolato) aluminum (Alq ₃ ) shown in the following chemical formula 4 is used as a ligand. Examples include quinoline derivatives such as organometallic complexes, oxadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and a combination of one or more of these. Can be used.

Although the average thickness of the electron carrying layer 43 is not specifically limited, It is preferable that it is 10-100 nm, and it is more preferable that it is 10-50 nm. Thereby, the electrons injected from the carrier generation layer 5 can be suitably transported to the first light emitting layer 42, and the holes that have passed through the first light emitting layer 42 can be suitably blocked.
The electron transport layer 43 may be provided as necessary, and may be omitted depending on the configuration of the electron transport layer 51 of the carrier generation layer 5 described later.

[Carrier generation layer]
The carrier generation layer 5 has a function of generating carriers (holes and electrons).
The carrier generation layer 5 is formed by laminating an electron transport layer 51, a diffusion prevention layer 52, an electron injection layer 53, and an electron withdrawing layer 54 in this order from the anode 3 side to the cathode 8 side.
According to such a carrier generation layer 5, since the diffusion preventing layer 52 is provided between the electron withdrawing layer 54 and the electron transporting layer 51, the electron withdrawing layer 54 and the electron transporting layer due to heat generation of the light emitting element 1 or the like. It is possible to prevent the material from being diffused between the layers 51. Therefore, the carrier generation layer 5 can stably generate holes and electrons over a long period of time. As a result, the lifetime of the light emitting element 1 can be extended.

Note that the electron injection layer 53 may be provided as necessary and can be omitted.
In addition, the average thickness of the carrier generation layer 5 is preferably 5 to 40 nm, and more preferably 10 to 30 nm. Thereby, the function (carrier generation function) of the carrier generation layer 5 can be sufficiently exhibited while preventing the drive voltage of the light emitting element 1 from increasing.

Hereinafter, each layer constituting the carrier generation layer 5 will be sequentially described in detail.
(Electron transport layer)
The electron transport layer 51 is provided between the first light emitting layer 42 and the electron withdrawing layer 54 described above, and has a function of transporting electrons from the electron attracting layer 54 side to the first light emitting layer 42 side.
Such an electron transport layer 51 may be formed using an electron transport material having an electron transport property as a main material, but in addition to an electron transport material having an electron transport property, an electron injection property having an electron injection property. It is preferable to include a material (electron donor material).

  Thereby, electrons attracted by the electron withdrawing layer 54 can be efficiently injected into the electron transport layer 51 and can be efficiently transported to the anode 3 side through the electron transport layer 51. Further, when the electron transport layer 51 is configured by adding (doping) an electron donor material to the electron transport material, in the electron transport layer 51, the electron transport material receives electrons from the electron donor material, and radicals are generated. It becomes an anionic state. Therefore, the amount of carrier generation in the carrier generation layer 5 can be increased.

As the electron transporting material used for the electron transporting layer 51, the same electron transporting material used for the electron transporting layer 43 described above can be used.
That is, as an electron transporting material used for the electron transport layer 51, for example, a quinoline derivative such as an organometallic complex having an 8-quinolinol or its derivative such as tris (8-quinolinolato) aluminum (Alq ₃ ) as a ligand. Oxadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like, and one or more of these can be used in combination.

Moreover, as an electron injectable material (electron donor material) used for the electron carrying layer 51, various inorganic insulating materials and various inorganic semiconductor materials are mentioned, for example.
Examples of such inorganic insulating materials include alkali metal chalcogenides (oxides, sulfides, selenides, tellurides), alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides. Of these, one or two or more of these can be used in combination.

Examples of the alkali metal chalcogenide include Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO.
Examples of the alkaline earth metal chalcogenide include CaO, BaO, SrO, BeO, BaS, MgO, and CaSe.
Examples of the alkali metal halide include CsF, LiF, NaF, KF, LiCl, KCl, and NaCl.
Examples of the alkaline earth metal halide include CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ , and BeF ₂ .

In addition, as the inorganic semiconductor material, for example, an oxide including at least one element of Li, Na, Ba, Ca, Sr, Yb, Al, Ga, In, Cd, Mg, Si, Ta, Sb, and Zn , Nitrides, oxynitrides, and the like, and one or more of these can be used in combination.
In particular, as the electron injecting material (electron donor material) used for the electron transport layer 51, it is preferable to use an alkali metal or an alkali metal compound. Thereby, the electron injection property of the electron transport layer 51 can be further improved while making the electron transport property of the electron transport layer 51 excellent. In particular, alkali metal compounds (alkali metal chalcogenides, alkali metal halides, and the like) have a very small work function, and the light-emitting element 1 can obtain high luminance by forming the electron transport layer 51 using the work function. It becomes.

The electron transport layer 51 has a function of blocking holes, like the electron transport layer 43 of the first light emitting unit 4 described above.
When the electron transport layer 51 is composed of an electron transport material and an electron injection material, the electron transport material is used as a host material, the electron injection material is used as a guest material, and electrons are injected into the electron transport material by co-evaporation or the like. The electron transport layer 51 can be formed by doping the conductive material.

Further, when the electron transport layer 51 is configured using an electron transport material and an electron injection material, the content (dope amount) of the electron injection material in the electron transport layer 51 is 0.1 to 20 wt%. Is preferable, and it is more preferable that it is 0.5-10 wt%. By setting the content of the electron injecting material in such a range, both the electron transporting property and the electron injecting property of the electron transporting layer 51 can be excellent in a balanced manner.
The average thickness of the electron transport layer 51 is not particularly limited, but is preferably 10 to 100 nm, and more preferably 10 to 50 nm. Thereby, the electrons attracted by the electron withdrawing layer 54 can be efficiently transported to the anode 3 side, and the holes that have passed through the first light emitting unit 4 can be blocked.

(Diffusion prevention layer)
The diffusion preventing layer 52 is provided between an electron withdrawing layer 54 described later and the electron transporting layer 51 described above, and has a function of preventing material diffusion between these layers.
In this embodiment, the diffusion prevention layer 52 is provided between the electron transport layer 51 and the electron injection layer 53 so as to be in contact therewith.
As a constituent material of the diffusion preventing layer 52, while allowing the electrons to be transported from the electron withdrawing layer 54 to the electron transporting layer 51, as described above, the layer between the electron withdrawing layer 54 and the electron transporting layer 51 is used. Although it will not specifically limit if diffusion of material can be prevented, For example, the thing similar to the electron transport material of the electron carrying layer 51 mentioned above can be used.
That is, as the constituent material of the diffusion preventing layer 52, for example, quinoline derivatives such as organometallic complexes having an 8-quinolinol or its derivative such as tris (8-quinolinolato) aluminum (Alq ₃ ) as a ligand, oxadi An azole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, and the like can be used, and one or more of these can be used in combination.

In particular, it is preferable that the diffusion preventing layer 52 includes an electron transporting material without including an electron injecting material (electron donor material).
Thereby, the electrons attracted by the electron withdrawing layer 54 can be efficiently transported to the electron transporting layer 51 through the diffusion preventing layer 52, and the electron donor material can be prevented from diffusing into the electron withdrawing layer 54. it can.

The average thickness of the diffusion preventing layer 52 is preferably 10 to 30 nm, more preferably 10 to 25 nm, and still more preferably 10 to 20 nm.
Thereby, the diffusion prevention layer 52 can prevent the diffusion of the material between the electron withdrawing layer 54 and the electron transporting layer 51 while suppressing the driving voltage of the light emitting element 1.
On the other hand, if the thickness of the diffusion preventing layer 52 is less than the lower limit value, the diffusion preventing layer 52 may not exhibit the above-described diffusion preventing effect depending on the material or film quality of the diffusion preventing layer 52. . On the other hand, when the thickness of the diffusion preventing layer 52 exceeds the upper limit, the driving voltage of the light emitting element 1 tends to increase depending on the material, film quality, etc. of the diffusion preventing layer 52.
Moreover, it is preferable that the electron mobility of the material (electron transport material) which comprises the diffusion prevention layer 52 is 10 ^<-5 > ^-10 < ^-3 > [cm < ² > / V * s]. Thereby, when the thickness of the diffusion preventing layer 52 falls within the above range, an increase in the driving voltage of the light emitting element 1 can be suppressed. Note that Alq3, which is a typical electron transporting material, has an electron mobility of about 10 ⁻⁵ [cm ² / V · s].

(Electron injection layer)
The electron injection layer 53 is provided between the diffusion preventing layer 52 and the electron withdrawing layer 54 and has a function of injecting electrons from the electron attracting layer 54 side to the diffusion preventing layer 52 side.
In particular, the electron injection layer 53 is made of an electron injecting material without containing an electron transporting material. Thereby, electrons attracted by the electron withdrawing layer 54 can be efficiently injected into the diffusion preventing layer 52.
As a constituent material of such an electron injection layer 53, the same material as the electron injection material (electron donor material) used for the electron transport layer 51 described above can be used.
That is, examples of the electron injecting material constituting the electron injecting layer 53 include various inorganic insulating materials and various inorganic semiconductor materials.
Examples of such inorganic insulating materials include alkali metal chalcogenides (oxides, sulfides, selenides, tellurides), alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides. Of these, one or two or more of these can be used in combination.

Examples of the alkali metal chalcogenide include Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO.
Examples of the alkaline earth metal chalcogenide include CaO, BaO, SrO, BeO, BaS, MgO, and CaSe.
Examples of the alkali metal halide include CsF, LiF, NaF, KF, LiCl, KCl, and NaCl.
Examples of the alkaline earth metal halide include CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ , and BeF ₂ .

In addition, as the inorganic semiconductor material, for example, an oxide including at least one element of Li, Na, Ba, Ca, Sr, Yb, Al, Ga, In, Cd, Mg, Si, Ta, Sb, and Zn , Nitrides, oxynitrides, and the like, and one or more of these can be used in combination.
In particular, it is preferable to use an alkali metal or an alkali metal compound as the electron injecting material constituting the electron injecting layer 53. Thereby, the electron injection property of the electron injection layer 53 can be improved more.

Moreover, it is preferable that the electron injection layer 53 is provided so as to have a portion in contact with the electron withdrawing layer 54 and a portion that does not exist in the plane direction. Thereby, it is possible to efficiently inject electrons attracted by the electron withdrawing layer 54 into the diffusion preventing layer 52 while preventing an increase in driving voltage of the light emitting element 1.
The average thickness of the electron injection layer 53 is preferably 0.2 to 1.0 nm, more preferably 0.2 to 0.8 nm, and 0.3 to 0.7 nm. Further preferred.
When the electron injection layer 53 is formed using a vacuum deposition method or the like so as to have such a thickness, it is possible to obtain the electron injection layer 53 having a portion that exists in the plane direction and a portion that does not exist relatively easily and reliably. Can do.

(Electronic suction layer)
The electron withdrawing layer (electron extraction layer) 54 is provided between the first light emitting layer 42 and the second light emitting layer 62 and is adjacent to the cathode 8 side (in the present embodiment, the second light emitting unit 6). The hole transport layer 61) has a function of attracting (withdrawing) electrons. Electrons attracted by the electron withdrawing layer 54 are injected into a layer adjacent to the anode 3 (in this embodiment, the electron transport layer 51).
Such an electron withdrawing layer 54 is composed of an organic compound having an electron withdrawing property as a main material.

As the organic compound having electron withdrawing property, an organic cyanide compound having an aromatic ring (hereinafter also referred to as “aromatic ring-containing organic cyanide compound”) is preferably used.
The aromatic ring-containing organic cyan compound has excellent electron withdrawing properties. Therefore, the amount of holes and electrons generated in the carrier generation layer 5 can be increased by forming the electron withdrawing layer by including an organic cyanide compound having an aromatic ring.

  The electron withdrawing layer 54 mainly composed of an aromatic ring-containing organic cyanide compound draws electrons from the hole transport material constituting the hole transport layer 61 by being in contact with an adjacent layer (hole transport layer 61). Can do. As a result, when the electron withdrawing layer 54 and the hole transporting layer 61 are in contact with each other, electrons are not present on the electron withdrawing layer 54 side in the vicinity of the interface between the electron withdrawing layer 54 and the hole transporting layer 61 even if no voltage is applied. And holes are generated on the hole transport layer 61 side. When a driving voltage is applied between the anode 3 and the cathode 8 in such a state, holes generated near the interface between the electron withdrawing layer 54 and the hole transporting layer 61 are moved toward the cathode 8 by the driving voltage. It is transported and contributes to the light emission of the second light emitting layer 62. In addition, electrons generated near the interface between the electron withdrawing layer 54 and the hole transport layer 61 are transported to the anode 3 side by the driving voltage, and contribute to light emission of the first light emitting layer 42. The generation of holes and electrons by the electron withdrawing layer 54 as described above is continuously performed while the drive voltage is applied, and these holes and electrons are generated by the second light emitting layer 62. It contributes to the light emission of the first light emitting layer 42.

In addition, the aromatic ring-containing organic cyanide compound is a relatively stable compound and can easily form the electron withdrawing layer 54 by a vapor deposition method such as vapor deposition. For this reason, it can use suitably for manufacture of the light emitting element 1, the quality of the manufactured light emitting element 1 becomes easy to be stabilized, and the yield of the light emitting element 1 becomes a high thing.
Such an aromatic ring-containing organic cyan compound is not particularly limited as long as it can exhibit the functions as described above, but is preferably a hexaazatriphenylene derivative into which a cyano group is introduced, for example, It is more preferable to use a hexaazatriphenylene derivative as shown in Chemical formula 5.

In the chemical formula 5, R1 to R6 are each independently a cyano group (—CN), a sulfone group (—SO ₂ R ′), a sulfoxide group (—SOR ′), a sulfonamide group (—SO ₂ NR ′ _2). ), A sulfonate group (—SO ₃ R ′), a nitro group (—NO ₂ ), or a trifluoromethane (—CF ₃ ) group, and at least one of R 1 to R 6 has a cyano group. R ′ is an alkyl group having 1 to 60 carbon atoms, an aryl group, or a heterocyclic group that is substituted or unsubstituted with an amine group, an amide group, an ether group, or an ester group.

Such a compound is excellent in function as an aromatic ring-containing organic cyanide compound. Therefore, the electron withdrawing layer 54 formed using such a compound can sufficiently extract electrons from the adjacent layer (hole transport layer 61), and transports the preferably extracted electrons to the anode 3 side. can do.
In particular, as the aromatic ring-containing organic cyan compound, in the compounds shown in Chemical Formula 5 as described above, it is preferable that all of R1 to R6 are cyano groups. That is, as the aromatic ring-containing organic cyan compound, it is preferable to use hexacyanohexaazatriphenylene as shown in the following chemical formula (6). Such a compound has a plurality of cyano groups having a high electron-withdrawing property. Therefore, the electron withdrawing layer 54 formed using such a compound can extract electrons more efficiently from the constituent materials of the adjacent layers (such as the hole transporting material of the hole transporting layer 61), and the carrier ( The amount of generation of electrons and holes) can be increased.

Further, the aromatic ring-containing organic cyanide compound is preferably present in an amorphous state in the electron withdrawing layer 54. Thereby, the effect of the aromatic ring-containing organic cyanide compound as described above can be obtained more remarkably. Note that the aromatic ring-containing organic cyanide compound is in an amorphous state by forming the electron withdrawing layer 54 by a vapor deposition method such as vapor deposition.
Further, the average thickness of the electron withdrawing layer 54 is preferably 5 to 40 nm, and more preferably 10 to 30 nm. Thereby, the function (electron attracting property) of the electron withdrawing layer 54 as described above can be sufficiently exhibited while preventing the drive voltage of the light emitting element 1 from increasing.

[Second light emitting unit]
As described above, the second light emitting unit 6 includes the hole transport layer 61, the second light emitting layer 62, and the electron transport layer 63.
(Hole transport layer)
The hole transport layer 61 has a function of transporting holes injected from the carrier generation layer 5 (the electron withdrawing layer 54) to the second light emitting layer 62. The hole transport layer 61 also has a function of preventing electrons from reaching the carrier generation layer 5 and deteriorating the carrier generation layer 5 by blocking electrons that have passed through the second light emitting layer 62. ing.

In particular, the hole transport layer 61 is provided between the second light emitting layer 62 and the carrier generation layer 5 so as to be in contact with the carrier generation layer 5.
Thereby, as described above, the electron withdrawing layer 54 can efficiently withdraw electrons from the hole transport layer 61. As a result, the amount of holes and electrons generated in the carrier generation layer 5 can be increased.

As the constituent material of the hole transport layer 61, the same constituent material as that of the hole transport layer 41 can be used.
In particular, among the above-described materials, the hole transport material constituting the hole transport layer 61 is preferably an amine compound, and N, N′-di (1-naphthyl) -N, N′— shown in Chemical Formula 2 above. Diphenyl-1,1′-diphenyl-4,4′-diamine (NPD) is more preferable. Such a compound comes into contact with the carrier generation layer 5 (electron withdrawing layer 54), whereby electrons are quickly extracted, and holes are generated and injected.
The average thickness of the hole transport layer 61 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 10 to 100 nm. Accordingly, holes can be transported suitably to the second light emitting layer 62, and electrons that have passed through the second light emitting layer 62 can be suitably blocked.

(Second light emitting layer)
The second light emitting layer 62 includes a light emitting material.
Such a light-emitting material is not particularly limited, and a light-emitting material similar to that of the first light-emitting layer 42 described above can be used. The light emitting material used for the second light emitting layer 62 may be the same as or different from the light emitting material of the first light emitting layer 42. In order to achieve the desired color of light emitted from the light emitting element 1, the light emitting material of the first light emitting layer 42 and the light emitting material of the second light emitting layer 62 can be appropriately selected and used in combination. .

In addition to the light emitting material, the second light emitting layer 62 may include a host material using the light emitting material as a guest material.
When the light emitting material (guest material) and the host material as described above are used, the content (dope amount) of the light emitting material in the second light emitting layer 62 is preferably 0.1 to 10 wt%. More preferably, it is 5 to 5 wt%. Luminous efficiency can be optimized by setting the content of the light emitting material within such a range.

The average thickness of the second light emitting layer 62 is not particularly limited, but is preferably 10 to 100 nm, more preferably 10 to 70 nm, and further preferably 10 to 50 nm.
In the present embodiment, the second light emitting layer is described as an example having one light emitting layer, but the first light emitting layer is a laminated body provided with a plurality of light emitting layers. Also good. In this case, the light emission colors of the plurality of light emitting layers may be the same or different. In the case where the second light emitting layer has a plurality of light emitting layers, an intermediate layer may be provided between the light emitting layers.

(Electron transport layer)
The electron transport layer 63 has a function of transporting electrons injected from the cathode 8 through the electron injection layer 7 to the second light emitting layer 62.
As a constituent material (electron transporting material) of the electron transport layer 63, the same material as the electron transport layer 43 described above can be used.
Although the average thickness of the electron carrying layer 63 is not specifically limited, It is preferable that it is 10-100 nm, and it is more preferable that it is 10-50 nm.

[Electron injection layer]
The electron injection layer 7 has a function of improving the electron injection efficiency of the cathode and the like.
Examples of the constituent material (electron injection material) of the electron injection layer 7 include various inorganic insulating materials and various inorganic semiconductor materials.
Examples of such inorganic insulating materials include alkali metal chalcogenides (oxides, sulfides, selenides, tellurides), alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides. Of these, one or two or more of these can be used in combination. By forming the electron injection layer using these as main materials, the electron injection property can be further improved. In particular, an alkali metal compound (alkali metal chalcogenide, alkali metal halide, etc.) has a very small work function, and the light-emitting element 1 can be obtained with high luminance by forming the electron injection layer 7 using the work function. Become.

Examples of the alkali metal chalcogenide include Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO.
Examples of the alkaline earth metal chalcogenide include CaO, BaO, SrO, BeO, BaS, MgO, and CaSe.
Examples of the alkali metal halide include CsF, LiF, NaF, KF, LiCl, KCl, and NaCl.
Examples of the alkaline earth metal halide include CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ , and BeF ₂ .

In addition, as the inorganic semiconductor material, for example, an oxide including at least one element of Li, Na, Ba, Ca, Sr, Yb, Al, Ga, In, Cd, Mg, Si, Ta, Sb, and Zn , Nitrides, oxynitrides, and the like, and one or more of these can be used in combination.
The average thickness of the electron injection layer 7 is not particularly limited, but is preferably about 0.1 to 1000 nm, more preferably about 0.2 to 100 nm, and about 0.2 to 50 nm. Further preferred.

[cathode]
The cathode 8 is an electrode that injects electrons into the second light emitting unit 6 through the electron injection layer 7 described above. As a constituent material of the cathode 8, a material having a small work function is preferably used.
Examples of the constituent material of the cathode 8 include Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, Yb, Ag, Cu, Al, Cs, Rb, and alloys containing these. These can be used alone or in combination of two or more thereof (for example, a multi-layer laminate).

In particular, when an alloy is used as the constituent material of the cathode 8, it is preferable to use an alloy containing a stable metal element such as Ag, Al, or Cu, specifically, an alloy such as MgAg, AlLi, or CuLi. By using such an alloy as a constituent material of the cathode 8, the electron injection efficiency and stability of the cathode 8 can be improved.
The average thickness of the cathode 8 is not particularly limited, but is preferably about 100 to 400 nm, and more preferably about 100 to 200 nm.
In addition, since the light emitting element 1 of this embodiment is a bottom emission type, the light transmittance of the cathode 8 is not particularly required.

[Sealing member]
The sealing member 9 is provided so as to cover the anode 3, the laminated body 15, and the cathode 8, and has a function of hermetically sealing them and blocking oxygen and moisture. By providing the sealing member 9, effects such as improvement in reliability of the light emitting element 1 and prevention of deterioration / deterioration (improvement in durability) can be obtained.
Examples of the constituent material of the sealing member 9 include Al, Au, Cr, Nb, Ta, Ti, alloys containing these, silicon oxide, and various resin materials. In addition, when using the material which has electroconductivity as a constituent material of the sealing member 9, in order to prevent a short circuit, it is required between the sealing member 9 and the anode 3, the laminated body 15, and the cathode 8. Accordingly, it is preferable to provide an insulating film.
Further, the sealing member 9 may be formed in a flat plate shape so as to face the substrate 2 and be sealed with a sealing material such as a thermosetting resin.

According to the light emitting element 1 configured as described above, holes and electrons are generated in the carrier generation layer 5 by applying a voltage between the anode 3 and the cathode 8. The generated electrons are transported to the first light emitting layer 42 and recombined with holes injected from the anode 3 to contribute to light emission. The generated holes are transported to the second light emitting layer 62 and recombined with electrons injected from the cathode 8, thereby contributing to light emission.
Thereby, since the light emitting element 1 can each emit the 1st light emitting layer 42 and the 2nd light emitting layer 62, while improving the light emission efficiency compared with the light emitting element with a single light emitting layer. The driving voltage can be reduced.

In particular, since the diffusion preventing layer 52 is provided between the electron withdrawing layer 54 and the electron transporting layer 51, the mutual material between the electron withdrawing layer 54 and the electron transporting layer 51 due to heat generation of the light emitting element 1 or the like. Diffusion can be prevented. Therefore, the carrier generation layer 5 can stably generate holes and electrons over a long period of time. As a result, the lifetime of the light emitting element 1 can be extended.
The light emitting element 1 configured as described above can be manufactured, for example, as follows.

[1] First, the substrate 2 is prepared, and the anode 3 is formed on the substrate 2.
The anode 3 is, for example, a chemical vapor deposition method (CVD) such as plasma CVD or thermal CVD, a dry plating method such as vacuum deposition, a wet plating method such as electrolytic plating, a thermal spraying method, a sol-gel method, a MOD method, or a metal foil. It can be formed by using, for example, bonding.
[2] Next, the first light-emitting portion 4 is formed on the anode 3.
The first light emitting unit 4 can be provided by sequentially forming the hole transport layer 41, the first light emitting layer 42 and the electron transport layer 43 on the anode 3.
Each layer as described above can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering, or the like.

Alternatively, a liquid material obtained by dissolving the constituent materials of each layer in a solvent or dispersing in a dispersion medium is supplied onto the anode 3 (or a layer above it) and then dried (desolvent or dedispersion medium). Can be formed.
As a method for supplying the liquid material, for example, various coating methods such as a spin coating method, a roll coating method, and an ink jet printing method can be used. By using such a coating method, the layers constituting the first light emitting unit 4 can be formed relatively easily.
Examples of the solvent or dispersion medium used for the preparation of the liquid material include various inorganic solvents, various organic solvents, and mixed solvents containing these.

The drying can be performed, for example, by standing in an atmospheric pressure or a reduced pressure atmosphere, heat treatment, or blowing an inert gas.
Prior to this step, the upper surface of the anode 3 may be subjected to oxygen plasma treatment. Thereby, it is possible to impart lyophilicity to the upper surface of the anode 3, remove (clean) organic substances adhering to the upper surface of the anode 3, adjust the work function near the upper surface of the anode 3, and the like. .
Here, the oxygen plasma treatment conditions include, for example, a plasma power of about 100 to 800 W, an oxygen gas flow rate of about 50 to 100 mL / min, a conveyance speed of the member to be treated (anode 3) of about 0.5 to 10 mm / sec, and a substrate. The temperature of 2 is preferably about 70 to 90 ° C.

[3] Next, the carrier generation layer 5 is formed on the first light emitting unit 4.
The carrier generation layer 5 can be formed by sequentially laminating an electron transport layer 51, a diffusion prevention layer 52, an electron injection layer 53, and an electron withdrawing layer 54 on the first light emitting unit 4.
Each layer constituting the carrier generation layer 5 can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering, or the like.
In addition, a material formed by dissolving the material of the layer constituting the carrier generation layer 5 in a solvent or dispersing in a dispersion medium is supplied onto the first light emitting unit 4 and then dried (desolvent or dedispersion medium). Can also be formed.

[4] Next, the second light-emitting portion 6 is formed on the carrier generation layer 5.
The second light emitting unit 6 can be formed in the same manner as the first light emitting unit 4.
[5] Next, the electron injection layer 7 is formed on the second light emitting unit 6.
When an inorganic material is used as the constituent material of the electron injection layer 7, the electron injection layer 7 is formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum vapor deposition or sputtering, and application and baking of inorganic fine particle ink. Etc. can be used.

[6] Next, the cathode 8 is formed on the electron injection layer 7.
The cathode 8 can be formed by using, for example, a vacuum deposition method, a sputtering method, joining of metal foils, application and firing of metal fine particle ink, or the like.
The light emitting element 1 is obtained through the steps as described above.

Finally, the sealing member 9 is covered so as to cover the obtained light emitting element 1 and bonded to the substrate 2.
The light emitting element 1 as described above can be used, for example, in a light emitting device (the light emitting device of the present invention).
Since such a light-emitting device includes the light-emitting element 1 as described above, the light-emitting device is driven at a relatively low voltage, has high light emission efficiency and a long light emission lifetime, and has high reliability.
Further, such a light emitting device can be used as a light source used for illumination, for example.
Moreover, the light-emitting device used for a display apparatus can be comprised by arrange | positioning the several light emitting element 1 in a light-emitting device in matrix form.

Next, an example of a display device to which the display device of the present invention is applied will be described.
FIG. 2 is a longitudinal sectional view showing an embodiment of a display device to which the display device of the present invention is applied.
A display device 100 illustrated in FIG. 2 includes a light emitting device 101 including a plurality of light emitting elements 1R, 1G, and 1B provided corresponding to the sub-pixels 100R, 100G, and 100B, and color filters 19R, 19G, and 19B. ing. Here, the display device 100 is a display panel having a top emission structure. The driving method of the display device is not particularly limited, and may be either an active matrix method or a passive matrix method.

The light emitting device 101 includes a substrate 21, light emitting elements 1R, 1G, and 1B, and a driving transistor 24.
A plurality of driving transistors 24 are provided on the substrate 21, and a planarizing layer 22 made of an insulating material is formed so as to cover these driving transistors 24.
Each driving transistor 24 includes a semiconductor layer 241 made of silicon, a gate insulating layer 242 formed on the semiconductor layer 241, a gate electrode 243 formed on the gate insulating layer 242, a source electrode 244, and a drain electrode. H.245.
On the planarization layer 22, light emitting elements 1R, 1G, and 1B are provided corresponding to the driving transistors 24, respectively.

  In the light emitting element 1 </ b> R, a reflective film 32, a corrosion preventing film 33, an anode 3, a laminate (organic EL light emitting unit) 15, a cathode 8, and a cathode cover 34 are laminated in this order on the planarization layer 22. In the present embodiment, the anode 3 of each light emitting element 1R, 1G, 1B constitutes a pixel electrode and is electrically connected to the drain electrode 245 of each driving transistor 24 by a conductive portion (wiring) 27. Moreover, the cathode 8 of each light emitting element 1R, 1G, 1B is a common electrode.

The configurations of the light emitting elements 1G and 1B are the same as the configuration of the light emitting element 1R. In FIG. 2, the same reference numerals are assigned to the same configurations as those in FIG. 1. Further, the configuration (characteristics) of the reflective film 32 may be different among the light emitting elements 1R, 1G, and 1B depending on the wavelength of light.
A partition wall 31 is provided between the adjacent light emitting elements 1R, 1G, and 1B.
In addition, an epoxy layer 35 made of an epoxy resin is formed on the light emitting device 101 thus configured so as to cover it.

The color filters 19R, 19G, and 19B are provided on the epoxy layer 35 described above corresponding to the light emitting elements 1R, 1G, and 1B.
The color filter 19R converts the white light W from the light emitting element 1R into red (R). The color filter 19G converts the white light W from the light emitting element 1G into green (G). The color filter 19B converts the white light W from the light emitting element 1B into blue (B). By using such color filters 19R, 19G, and 19B in combination with the light emitting elements 1R, 1G, and 1B, a full color image can be displayed.

A light shielding layer 36 is formed between the adjacent color filters 19R, 19G, and 19B. Thereby, it is possible to prevent the unintended subpixels 100R, 100G, and 100B from emitting light.
A sealing substrate 20 is provided on the color filters 19R, 19G, 19B and the light shielding layer 36 so as to cover them.

The display device 100 as described above may be a single color display, and color display is also possible by selecting a light emitting material used for each light emitting element 1R, 1G, 1B.
Since such a display device 100 (the display device of the present invention) uses the light emitting device as described above, it is driven at a relatively low voltage, has excellent durability (long emission life), and excellent light emission efficiency. It is. Therefore, a high-quality image can be displayed over a long period of time with low power consumption.
Such a display device 100 (the display device of the present invention) can be incorporated into various electronic devices. Since such an electronic device uses the display device as described above, it is possible to increase the light emission efficiency and reduce the driving voltage while maintaining excellent durability. Therefore, a high-quality image can be displayed over a long period.

FIG. 3 is a perspective view showing the configuration of a mobile (or notebook) personal computer to which the electronic apparatus of the present invention is applied.
In this figure, a personal computer 1100 includes a main body 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display. The display unit 1106 is rotatable with respect to the main body 1104 via a hinge structure. It is supported by.
In the personal computer 1100, the display unit included in the display unit 1106 is configured by the display device 100 described above.

FIG. 4 is a perspective view showing a configuration of a mobile phone (including PHS) to which the electronic apparatus of the present invention is applied.
In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204 and a mouthpiece 1206, and a display unit.
In the cellular phone 1200, the display unit is configured by the display device 100 described above.

FIG. 5 is a perspective view showing a configuration of a digital still camera to which the electronic apparatus of the present invention is applied. In this figure, connection with an external device is also simply shown.
Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an imaging device such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to display based on an imaging signal from the CCD, and functions as a finder that displays an object as an electronic image.
In the digital still camera 1300, the display unit is configured by the display device 100 described above.

A circuit board 1308 is installed inside the case. The circuit board 1308 is provided with a memory that can store (store) an imaging signal.
A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side of the case 1302 (on the back side in the illustrated configuration).
When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory of the circuit board 1308.

  In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the data communication input / output terminal 1314 as necessary. Further, the imaging signal stored in the memory of the circuit board 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation.

  The electronic apparatus of the present invention includes, for example, a television, a video camera, a viewfinder type, in addition to the personal computer (mobile personal computer) in FIG. 3, the mobile phone in FIG. 4, and the digital still camera in FIG. Monitor direct-view video tape recorder, laptop personal computer, car navigation system, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, security TV Monitors, electronic binoculars, POS terminals, devices equipped with touch panels (for example, cash dispensers and automatic ticket vending machines for financial institutions), medical devices (for example, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiographs, ultrasound diagnostic devices, internal Endoscope display device), fish finder, various measuring instruments, Vessels such (e.g., gages for vehicles, aircraft, and ships), a flight simulator, various monitors, and a projection display such as a projector.

The light emitting element, the light emitting device, the display device, and the electronic device of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.
For example, the light-emitting element described above has been described as having two light-emitting layers, but the present invention is not limited to this. For example, the light-emitting element may have three or more light-emitting layers. In this case, a carrier generation layer may be provided between at least one of the light emitting layer layers.
In the light-emitting element described above, the light-emitting portion (light-emitting unit) has been described as including a hole transport layer, a light-emitting layer, and an electron transport layer. However, the present invention is not limited thereto, and at least one light-emitting layer is included. For example, it may be composed only of a light emitting layer, or may have a layer such as an electron injection layer or a hole injection layer.

Next, specific examples of the present invention will be described.
1. Production of light emitting device (Example 1)
<1> First, a transparent glass substrate having an average thickness of 0.5 mm was prepared. Next, an ITO electrode (anode) having an average thickness of 100 nm was formed on the substrate by sputtering.
And after immersing a board | substrate in order of acetone and 2-propanol and ultrasonically cleaning, the oxygen plasma process was performed.

<2> Next, on the ITO electrode, N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (shown in Chemical Formula 1) NPD) was deposited by a vacuum deposition method to form a hole transport layer having an average thickness of 50 nm (a hole transport layer of the first light emitting portion).
<3> Next, tris (8-quinolinolato) aluminum (Alq ₃ ) shown in Chemical Formula 4 as a light emitting material is vapor-deposited on the hole transport layer by a vacuum vapor deposition method, so that the first light emission with an average thickness of 50 nm is obtained. A layer was formed.

<4> Next, tris (8-quinolinolato) aluminum (Alq ₃ ) shown in Chemical Formula 4 and Li ₂ O are vapor-deposited on the first light-emitting layer by a vacuum evaporation method, and the average thickness is 30 nm. An electron transport layer (an electron transport layer of a carrier generation layer) was formed. The content of (8-quinolato) lithium complex (Liq) and Li ₂ O in this electron transport layer was set to 90:10 by volume ratio.
<5> Next, on the electron transport layer, tris (8-quinolinolato) aluminum (Alq ₃ ) shown in Chemical Formula 4 was deposited by a vacuum deposition method to form a diffusion prevention layer having an average thickness of 10 nm.

<6> Next, Li ₂ O was vapor-deposited on the diffusion prevention layer by a vacuum vapor deposition method to form an electron injection layer (an electron injection layer of a carrier generation layer) having an average thickness of 0.5 nm.
<7> Next, on the electron injection layer, hexacyanohexaazatriphenylene as shown in Chemical Formula 6 was deposited by a vacuum deposition method to form an electron withdrawing layer having an average thickness of 30 nm. As a result, a carrier generation layer including an electron transport layer, a diffusion prevention layer, an electron injection layer, and an electron withdrawing layer was obtained.

<8> Next, on the carrier generation layer, N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine represented by Chemical Formula 1 above. (NPD) was deposited by a vacuum deposition method to form a hole transport layer having an average thickness of 80 nm.
<9> Next, on the hole transport layer, tris (8-quinolinolato) aluminum (Alq ₃ ) shown in Chemical Formula 4 as a light emitting material is deposited by a vacuum vapor deposition method, and second light emission with an average thickness of 80 nm. A layer was formed.
<10> Next, lithium fluoride (LiF) was formed on the second light-emitting layer by a vacuum evaporation method to form an electron injection layer with an average thickness of 1.0 nm.

<11> Next, Al was formed into a film by the vacuum evaporation method on the electron injection layer. Thereby, a cathode having an average thickness of 100 nm made of Al was formed.
<12> Next, a glass protective cover (sealing member) was placed over the formed layers, and fixed and sealed with an epoxy resin.
Through the above steps, the anode, the hole transport layer, the first light emitting layer, the carrier generation layer (electron transport layer, diffusion preventing layer, electron injection layer, electron withdrawing layer), hole transport layer, second layer are formed on the substrate. A light emitting device (tandem light emitting device) in which the light emitting layer, the electron injection layer, and the cathode were laminated in this order was manufactured.

(Example 2)
A light emitting device was manufactured in the same manner as in Example 1 except that the average thickness of the diffusion preventing layer was changed to 20 nm.
(Example 3)
A light emitting device was manufactured in the same manner as in Example 1 except that the average thickness of the diffusion preventing layer was changed to 30 nm.

(Comparative Example 1)
A light emitting device (non-tandem light emitting device) was manufactured in the same manner as in Example 1 except that the formation of the carrier generation layer and the second light emitting layer was omitted.
(Comparative Example 2)
A light emitting device was manufactured in the same manner as in Example 1 except that the formation of the diffusion preventing layer and the electron injection layer of the carrier generation layer was omitted.

2. Evaluation 2-1. Evaluation of Luminous Efficiency For each example and each comparative example, a constant current was passed through the light emitting element using a direct current power source so that the luminance was 1000 cd / m ² while measuring with a luminance meter. Then, the driving voltage and current density at that time were measured, and light emission efficiency (cd / A, luminance per current) was obtained from the relationship between the measured current density and luminance.

2-2. Evaluation of Luminous Life For each example and each comparative example, first, a constant current was passed through the light emitting element using a direct current power source so that the luminance was 1000 cd / m ² while measuring with a luminance meter. Then, a constant current was continuously supplied to the light emitting element with the current density at that time, and during that time, luminance was measured using a luminance meter, and a time (LT80) during which the luminance was 80% of the initial luminance was measured.
The results of the above evaluations are shown in Table 1 together with the configurations of the carrier generation layers of the examples and comparative examples. In Table 1, the hexacyanohexaazatriphenylene shown in Chemical Formula 6 is indicated by “HAT-CN6”.

As is clear from Table 1, each of the light-emitting elements in each example has an extremely long life, a low driving voltage, and a high light-emitting efficiency as compared with the light-emitting element of Comparative Example 1.
In addition, the light emitting device of Example 1 was able to achieve a longer life while achieving the same low driving voltage and high light emission efficiency as compared with the light emitting device of Comparative Example 2.
In addition, the light emitting elements of Examples 2 and 3 were able to achieve higher light emission efficiency and longer life while realizing the same low driving voltage as compared with the light emitting element of Comparative Example 2.

Here, although the light emitting element of Comparative Example 2 has a longer life compared to the light emitting element of Comparative Example 1, it has a shorter life than the light emitting element of the present invention. This is considered to be because Li ₂ O in the electron transport layer of the carrier generation layer diffuses into the electron withdrawing layer and inhibits the action of separating the electrons attracted by the electron withdrawing layer to the electron transporting layer side.
On the other hand, in the light emitting device of each example of the present invention, the diffusion preventing layer prevents Li ₂ O in the electron transport layer of the carrier generation layer from diffusing into the electron withdrawing layer. It is thought that the lifetime was longer.

In the light emitting device of each example, the electron injection layer composed of Li ₂ O alone is in contact with the electron withdrawing layer, but Li ₂ O alone grows to a particle size that cannot pass through the gaps in the organic film. to so do not be Li 2 _O diffuses from the electron injection layer formed of Li 2 _O alone into the electron withdrawing layer. In contrast, the light emitting device of the Comparative Example, the electron transport layer in contact with the electron-withdrawing layer is doped with Li 2 _O in an organic film, the Li 2 _O is enough to fit through the gap of the organic film grain Since it can grow only to the diameter, it is considered that Li ₂ O diffused from the electron transport layer doped with Li ₂ O to the organic film to the electron withdrawing layer.

  DESCRIPTION OF SYMBOLS 1, 1G, 1R, 1B ... Light emitting element 2 ... Board | substrate 3 ... Anode 4 ... 1st light emission part 41 ... Hole transport layer 42 ... 1st light emission layer 43 ... Electron transport layer 5 ... ... carrier generation layer 51 ... electron transport layer 52 ... diffusion prevention layer 522 ... part 53 ... electron injection layer 54 ... electron withdrawing layer 6 ... second light emitting part 61 ... hole transport layer 62 ... Second light emitting layer 63... Electron transport layer 7... Electron injection layer 8... Cathode 9... Sealing member 15 .. Laminated body 19B, 19G, 19R. Device 100R, 100G, 100B: Sub-pixel 20: Sealing substrate 21: Substrate 22 ... Planarization layer 24 ... Driving transistor 241 ... Semiconductor layer 242 ... Gate insulating layer 243 ... Gate electrode 244 ... ... Source electrode 245 ... Drain electrode 27 ... Wiring 31 ... Partition 32 ... Reflective film 33 ... Corrosion prevention film 34 ... Cathode cover 35 ... Epoxy layer 36 ... Shading layer 1100 ... Personal computer 1102 ... Keyboard DESCRIPTION OF SYMBOLS 1104 ...... Main-body part 1106 ...... Display unit 1200 ...... Cell-phone 1202 ...... Operation button 1204 …… Earpiece 1206 …… Mouthpiece 1300 …… Digital still camera 1302 …… Case (body) 1304 …… Light receiving unit 1306 ... Shutter button 1308 ... Circuit board 1312 ... Video signal output terminal 1314 ... Input / output terminal for data communication 1430 ... TV monitor 1440 ... Personal computer W ... White light

Claims (14)

The anode,
A cathode,
A first light emitting layer that is provided between the anode and the cathode and emits light when energized between the anode and the cathode;
A second light emitting layer that is provided between the cathode and the first light emitting layer and emits light when energized between the anode and the cathode;
Provided between the first light-emitting layer and the second light-emitting layer, and provided between the first light-emitting layer and the electron-withdrawing layer. Having an electron transport layer, and a diffusion prevention layer that is provided between the electron withdrawing layer and the electron transport layer and prevents diffusion of a material between these layers, and generates holes and electrons. A light-emitting element comprising a carrier generation layer.   The light-emitting element according to claim 1, wherein the electron transport layer includes an electron transport material and an electron donor material.   The light-emitting element according to claim 2, wherein the diffusion preventing layer includes an electron transporting material without including an electron donor material.   The light-emitting element according to claim 2, wherein the electron donor material is an alkali metal or an alkali metal compound.   The carrier generation layer is provided between the diffusion preventing layer and the electron withdrawing layer, and includes an electron injection layer made of an electron injection material without including the electron transport material. The light emitting element in any one.   The light-emitting element according to claim 5, wherein the electron injection layer is provided so as to have a portion in contact with the electron withdrawing layer and a portion that does not exist in a plane direction.   The light emitting device according to claim 5 or 6, wherein an average thickness of the electron injection layer is 0.2 to 1.0 nm.   The light emitting device according to any one of claims 1 to 7, wherein the diffusion prevention layer has an average thickness of 10 to 30 nm.   The light emitting device according to claim 1, wherein the electron withdrawing layer includes an organic cyanide compound having an aromatic ring.   The light emitting device according to claim 9, wherein the organic cyanide compound is a hexaazatriphenylene derivative.   11. The hole transport layer having a hole transport property is provided between the second light emitting layer and the carrier generation layer so as to be in contact with the electron withdrawing layer. The light emitting element of description.   A light-emitting device comprising the light-emitting element according to claim 1.   A display device comprising the light-emitting device according to claim 12.   An electronic apparatus comprising the display device according to claim 13.

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