JP2012059419A - Light-emitting element, display device and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element arranged to prevent the change in the balance of light emission by more than one light-emitting layer and have an elongated life, and to provide a highly reliable display device and an electronic device, both having such light-emitting element.SOLUTION: The light-emitting element 1 of the invention has: an anode 3; a cathode 13; a red light-emitting layer (first light-emitting layer) 6 provided between the anode 3 and cathode 13 and caused to emit light by forcing current to run between the anode 3 and cathode 13; a blue light-emitting layer (second light-emitting layer) 8 provided between the cathode 13 and red light-emitting layer 6 and caused to emit light by forcing current to run between the anode 3 and cathode 13; and an intermediate layer 7 provided between the red and blue light-emitting layers 6 and 8 in contact therewith, and made of an insulative inorganic material.

Description

  The present invention relates to a light emitting element, a display device, and an electronic device.

  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 device, by applying an electric field between the cathode and the anode, electrons are injected into the light emitting layer from the cathode side and holes are injected from the anode side, and electrons and holes are injected into the light emitting layer. Recombination generates excitons, and when the excitons return to the ground state, the energy is emitted as light.

As such a light emitting element, one having a plurality of light emitting layers and an intermediate layer provided between the light emitting layers is known (for example, see Patent Document 1). In such a light-emitting element, the amount of recombination of holes and electrons in each light-emitting layer is adjusted by limiting the movement of carriers (electrons and holes) between the light-emitting layers in the intermediate layer, and as a result The light emission balance of each light emitting layer can be adjusted.
However, in the conventional light emitting device, since the intermediate layer is composed of an organic compound such as a general hole transport material or electron transport material, the intermediate layer is not sufficiently resistant to carriers, and the light emission balance is changed. There was a problem that. That is, the conventional light emitting device cannot maintain the light emission balance of the plurality of light emitting layers in a predetermined state over a long period of time.

Japanese Patent Laid-Open No. 2005-10091

  An object of the present invention is to provide a light-emitting element capable of preventing a change in the light emission balance of a plurality of light-emitting layers and extending the lifetime, and a highly reliable display device and electronic apparatus including the light-emitting element. It is in.

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;
An intermediate layer is provided between the first light emitting layer and the second light emitting layer so as to be in contact with the first light emitting layer and made of an insulating inorganic material.
Thereby, it is possible to prevent a change in the light emission balance of the plurality of light emitting layers and to extend the life.

In the light emitting device of the present invention, the inorganic material is preferably one or a combination of two or more of metal oxides, metal nitrides, and metal fluorides.
Such an inorganic material is excellent in insulation. Therefore, carrier movement between the first light-emitting layer and the second light-emitting layer can be effectively limited.
In the light emitting device of the present invention, the inorganic material is an alkali metal oxide, an alkali metal nitride, an alkali metal fluoride, an alkaline earth metal oxide, an alkaline earth metal nitride, or an alkaline earth metal fluoride. It is preferable to use one or a combination of two or more.
Such an inorganic material is excellent in insulation and electron injection. Therefore, the intermediate layer made of such an inorganic material can effectively limit the movement of holes while efficiently injecting electrons from the second light emitting layer to the first light emitting layer. As a result, the lifetime can be increased and the light emission efficiency of the light emitting element can be improved.

In the light emitting device of the present invention, the inorganic material is preferably a metal fluoride.
Such an inorganic material is excellent in insulation and electron injection. Therefore, the intermediate layer made of such an inorganic material can effectively limit the movement of holes while efficiently injecting electrons from the second light emitting layer to the first light emitting layer. As a result, the lifetime can be increased and the light emission efficiency of the light emitting element can be improved.
In the light emitting device of the present invention, the average thickness of the intermediate layer is preferably 1 nm or more and 5 nm or less.
Thereby, the flow of carriers between the first light emitting layer and the second light emitting layer can be appropriately limited.

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;
A third light emitting layer that is provided between the cathode and the second light emitting layer and emits light when energized between the anode and the cathode;
A first intermediate layer formed of an insulating inorganic material provided between and in contact with the first light emitting layer and the second light emitting layer;
It has a 2nd intermediate | middle layer comprised by the inorganic material which has the insulating property provided between the said 2nd light emitting layer and the said 3rd light emitting layer, and is characterized by the above-mentioned.
Thereby, it is possible to prevent a change in the light emission balance of the plurality of light emitting layers and to extend the life. Further, since the three light emitting layers can emit light in a balanced manner, the light emission efficiency is also excellent.

The display device of the present invention includes the light emitting element of the present invention.
Thereby, a high-quality image can be displayed over a long period of time, and a display device with excellent reliability can be provided.
An electronic apparatus according to the present invention includes the display device according to the present invention.
Accordingly, a high-quality image can be displayed over a long period of time, and an electronic device having excellent reliability can be provided.

It is a figure which shows typically the longitudinal cross-section of the light emitting element which concerns on 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 according to the invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram schematically showing a longitudinal section of a light emitting device according to an 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”.
A light-emitting element (electroluminescence element) 1 shown in FIG. 1 emits white light by emitting R (red), G (green), and B (blue).

Such a light emitting device 1 includes an anode 3, a hole injection layer 4, a hole transport layer 5, a red light emitting layer (first light emitting layer) 6, an intermediate layer 7 (first intermediate layer), and a blue light emitting layer ( (Second light emitting layer) 8, intermediate layer 9 (second intermediate layer), green light emitting layer (third light emitting layer) 10, electron transport layer 11, electron injection layer 12, and cathode 13 are laminated in this order. It will be.
In other words, the light-emitting element 1 includes the hole injection layer 4, the hole transport layer 5, the red light-emitting layer 6, the intermediate layer 7, the blue light-emitting layer 8, the intermediate layer 9, the green light-emitting layer 10, the electron transport layer 11, and the electrons. A laminated body 14 in which the injection layer 12 is laminated in this order is interposed between two electrodes (between the anode 3 and the cathode 13).

The entire light emitting element 1 is provided on the substrate 2 and sealed with a sealing member 15.
In such a light emitting device 1, electrons are supplied (injected) from the cathode 13 side to the light emitting layers of the red light emitting layer 6, the blue light emitting layer 8, and the green light emitting layer 10, and the anode 3 side. Holes are supplied (injected). In each light emitting layer, holes and electrons recombine, 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). Thereby, the light emitting element 1 emits white light.

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 hole transport layer 5 through a hole injection layer 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 about 10 to 200 nm, and more preferably about 50 to 150 nm.

(cathode)
On the other hand, the cathode 13 is an electrode that injects electrons into the electron transport layer 11 via an electron injection layer 12 described later. As a constituent material of the cathode 13, a material having a small work function is preferably used.
Examples of the constituent material of the cathode 13 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 13, 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 the constituent material of the cathode 13, the electron injection efficiency and stability of the cathode 13 can be improved.
Although the average thickness of such a cathode 13 is not specifically limited, It is preferable that it is about 100-10000 nm, and it is more preferable that it is about 200-500 nm.
In addition, since the light emitting element 1 of this embodiment is a bottom emission type, the light transmittance of the cathode 13 is not particularly required.

(Hole injection layer)
The hole injection layer 4 has a function of improving the hole injection efficiency from the anode 3.
The constituent material (hole injection material) of the hole injection layer 4 is not particularly limited. For example, copper phthalocyanine or 4,4 ′, 4 ″ -tris (N, N-phenyl-3-methylphenyl) Amino) triphenylamine (m-MTDATA), N, N′-bis- (4-diphenylamino-phenyl) -N, N′-diphenyl-biphenyl-4-4′-diamine represented by the following formula (1) Etc.

The average thickness of the hole injection layer 4 is not particularly limited, but is preferably about 5 to 150 nm, and more preferably about 10 to 100 nm.
The hole injection layer 4 can be omitted.

(Hole transport layer)
The hole transport layer 5 has a function of transporting holes injected from the anode 3 through the hole injection layer 4 to the red light emitting layer 6.
As the constituent material of the hole transport layer 5, various p-type high molecular materials and various p-type low molecular materials can be used alone or in combination. For example, N, represented by the following formula (2) N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPD), N, N′-diphenyl-N, N′-bis (3- And tetraarylbenzidine derivatives such as methylphenyl) -1,1′-diphenyl-4,4′-diamine (TPD), tetraaryldiaminofluorene compounds or derivatives thereof (amine compounds), etc. Species or a combination of two or more can be used.

The average thickness of the hole transport layer 5 is not particularly limited, but is preferably about 10 to 150 nm, and more preferably about 10 to 100 nm.
The hole transport layer 5 can be omitted.

(Red light emitting layer)
The red light emitting layer (first light emitting layer) 6 includes a red light emitting material (first light emitting material) that emits red light (first color).
Such a red light emitting material is not particularly limited, and various red fluorescent materials and red phosphorescent materials can be used singly or in combination.

  The red fluorescent material is not particularly limited as long as it emits red fluorescence. For example, perylene derivatives such as tetraaryldiindenoperylene derivatives represented by the following formula (3), europium complexes, benzopyran derivatives, rhodamine derivatives , Benzothioxanthene derivative, porphyrin derivative, 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-dimethylamino) Styryl) -4H-pyran (DCM) and the like.

The red phosphorescent material is not particularly limited as long as it emits red phosphorescence, and examples thereof include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. Among the ligands of these metal complexes, And those having at least one of phenylpyridine skeleton, bipyridyl skeleton, 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).

  Further, as a constituent material of the red light emitting layer 6, in addition to the red light emitting material as described above, a host material (first host material) to which the red light emitting material is added as a guest material may be used. This host material recombines holes and electrons to generate excitons, and excites the red light-emitting material by transferring the exciton energy to the red light-emitting material (Felster movement or Dexter movement). It has a function. Such a host material can be used by, for example, doping a host material with a red light emitting material, which is a guest material, as a dopant.

Such a first host material is not particularly limited as long as it exhibits the above-described function with respect to the red light emitting material to be used. When the red light emitting material includes a red fluorescent material, for example, Styrylarylene derivatives, naphthacene derivatives, compounds represented by the following formula (4), anthracene derivatives such as 2-t-butyl-9,10-di (2-naphthyl) anthracene (TBADN), perylene derivatives, distyrylbenzene derivatives, A distyrylamine derivative, a quinolinolato-based metal complex such as tris (8-quinolinolato) aluminum complex (Alq ₃ ), a triarylamine derivative such as a tetramer of triphenylamine, an oxadiazole derivative, and the following formula (5): Rubrene and its derivatives, silole derivatives, dicarbazole derivatives , Oligothiophene derivatives, benzopyran derivatives, triazole derivatives, benzoxazole derivatives, benzothiazole derivatives, quinoline derivatives, 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi), etc. One species can be used alone, or two or more species can be used in combination.
Further, when the red light emitting material includes a red phosphorescent material, examples of the first host material include 3-phenyl-4- (1′-naphthyl) -5-phenylcarbazole, 4,4′-N, N ′. -Carbazole derivatives, such as dicarbazole biphenyl (CBP), etc. are mentioned, Among these, it can also be used individually by 1 type or in combination of 2 or more types.

  When the red light emitting layer 6 contains a host material, the content (dope amount) of the red light emitting material in the red light emitting layer 6 is preferably 0.01 to 10 wt%, and preferably 0.1 to 5 wt%. Is more preferable. By setting the content of the red light emitting material in such a range, the light emission efficiency can be optimized, and the red light emitting layer is balanced with the light emitting amount of the blue light emitting layer 8 and the green light emitting layer 10 described later. 6 can emit light.

(Middle layer)
The intermediate layer 7 (first intermediate layer) is provided between and in contact with the red light emitting layer 6 described above and a blue light emitting layer 8 described later. The intermediate layer 7 has a function of adjusting the amount of electrons transported from the blue light emitting layer 8 to the red light emitting layer 6. The intermediate layer 7 has a function of adjusting the amount of holes transported from the red light emitting layer 6 to the blue light emitting layer 8. With these functions, the red light emitting layer 6 and the blue light emitting layer 8 can each emit light efficiently.

In particular, the intermediate layer 7 is made of an insulating inorganic material (hereinafter also referred to as “insulating inorganic material”).
Thus, since the intermediate layer 7 has insulation properties, it retains electrons in the vicinity of the interface with the blue light emitting layer 8 (interface on the cathode 13 side) and the interface with the red light emitting layer 6 (on the anode 3 side). Holes can be retained near the interface)). Therefore, the amount of holes and electrons that pass through the intermediate layer 7 can be controlled. As a result, the light emitting element 1 can cause each light emitting layer provided on both sides of the intermediate layer 7 to emit light in a balanced manner.

In addition, since the intermediate layer 7 is made of an inorganic material, the intermediate layer 7 is less likely to deteriorate than the case where the intermediate layer 7 is made of an organic compound. Maintained. As a result, in the light-emitting element 1, each light-emitting layer can emit light in a well-balanced manner over a long period of time, and the life can be extended. That is, it is possible to prevent a change in the light emission balance of the plurality of light emitting layers and to extend the life.
Further, the intermediate layer 7 is configured to allow electrons and holes to pass through the tunnel effect while appropriately blocking electrons and holes as described above. The degree of such a tunnel effect can be controlled by the thickness of the intermediate layer 7.

  Therefore, the average thickness of the intermediate layer 7 is preferably such that electrons and holes can pass through the tunnel effect. Specifically, the average thickness is preferably 1 nm or more and 5 nm or less, and preferably 1 nm or more and 4 nm or less. Is more preferably 1 nm or more and 3 nm or less. Thereby, the flow of carriers (holes and electrons) between the red light emitting layer 6 and the blue light emitting layer 8 can be appropriately limited.

On the other hand, if the average thickness of the intermediate layer 7 is less than the lower limit value, depending on the type of the insulating inorganic material, the film quality of the intermediate layer 7 may become non-uniform, resulting in variations in characteristics or carrier flow. In some cases, it may be difficult to suitably exhibit the function of limiting the above. On the other hand, when the average thickness of the intermediate layer 7 exceeds the upper limit value, the driving voltage tends to increase.
As the material constituting the intermediate layer 7, various insulating inorganic materials can be used. For example, metal (typical metal and transition metal) or metalloid nitride, oxynitride, chalcogenide (oxidation) Products, sulfides, selenides, tellurides), halides, and the like.

The nitride or nitride oxide includes a nitride containing at least one element of Li, Na, Ba, Ca, Sr, Yb, Al, Ga, In, Cd, Mg, Si, Ta, Sb and Zn, or Examples thereof include oxynitrides.
Examples of chalcogenides include oxides such as SiO ₂ , Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, BeO, BaO, Li ₂ O, GeO ₂ , and Al ₂ O ₃ . , Sulfides such as Na ₂ S and BaS, and selenides such as Na ₂ Se and CaSe.

Examples of the halide include CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ , BeF ₂ , CsF, LiF, NaF, KF, LiCl, KCl, NaCl, and the like.
Among the insulating inorganic materials described above, the inorganic material used for the intermediate layer 7 is preferably a combination of one or more of metal oxides, metal nitrides, and metal fluorides. Such an inorganic material is excellent in insulation. Therefore, the movement of carriers between the red light emitting layer 6 and the blue light emitting layer 8 can be effectively limited.

In particular, the inorganic material used for the intermediate layer 7 is one of alkali metal oxide, alkali metal nitride, alkali metal fluoride, alkaline earth metal oxide, alkaline earth metal nitride, and alkaline earth metal fluoride. It is preferable to use seeds or a combination of two or more.
Such an inorganic material is excellent in insulation and electron injection. Therefore, the intermediate layer 7 made of such an inorganic material can efficiently inject electrons from the blue light emitting layer 8 to the red light emitting layer 6. As a result, the light emission efficiency of the light emitting element 1 can be improved.

Further, the inorganic material used for the intermediate layer 7 is preferably a metal fluoride, and particularly preferably LiF.
Such an inorganic material is excellent in insulation and electron injection. Therefore, the intermediate layer 7 made of such an inorganic material can efficiently inject electrons from the blue light emitting layer 8 to the red light emitting layer 6. As a result, the light emission efficiency of the light emitting element 1 can be improved.
In addition, when the intermediate layer 7 is used in combination of two or more of the insulating inorganic materials as described above, the intermediate layer 7 may be composed of a mixed material obtained by mixing two or more insulating inorganic materials, or different insulating materials. A plurality of layers made of a conductive inorganic material may be laminated.

(Blue light emitting layer)
The blue light emitting layer (second light emitting layer) 8 includes a blue light emitting material (second light emitting material) that emits blue light (second color).
Such a blue light emitting material is not particularly limited, and various blue fluorescent materials and blue phosphorescent materials can be used alone or in combination of two or more.

  The blue fluorescent material is not particularly limited as long as it emits blue fluorescence. For example, a distyrylamine derivative such as a distyryldiamine compound represented by the following formula (6), a fluoranthene derivative, a pyrene derivative, perylene And perylene derivatives, anthracene derivatives, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, chrysene derivatives, phenanthrene derivatives, distyrylbenzene derivatives, 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-dioctylfluorene-2,7-diyl) -co- (ethyl Nilbenzene)] and the like, and one of these may be used alone or two or more of them may be used in combination.

The blue phosphorescent material is not particularly limited as long as it emits blue phosphorescence, and examples thereof 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 ).

Further, the blue light emitting layer 8 may contain a host material. As a host material that can be used for the blue light emitting layer 8, a host material similar to the host material for the red light emitting layer 6 described above can be used.
When the blue light emitting layer 8 contains a host material, the content (doping amount) of the blue light emitting material in the blue light emitting layer 8 is preferably 0.01 to 20 wt%, and more preferably 1 to 15 wt%. preferable. By setting the content of the blue light emitting material within such a range, the light emission efficiency can be optimized, and the blue light emitting layer is balanced with the light emitting amount of the red light emitting layer 6 and the green light emitting layer 10 described later. 8 can emit light.

(Middle layer)
The intermediate layer 9 (second intermediate layer) is provided between and in contact with the blue light emitting layer 8 described above and a green light emitting layer 10 described later. The intermediate layer 9 has a function of adjusting the amount of electrons transported from the green light emitting layer 10 to the blue light emitting layer 8. The intermediate layer 9 has a function of adjusting the amount of holes transported from the blue light emitting layer 8 to the green light emitting layer 10. With these functions, the blue light emitting layer 8 and the green light emitting layer 10 can each emit light efficiently.

In particular, the intermediate layer 9 is made of an inorganic material having an insulating property like the intermediate layer 7 described above.
Thus, since the intermediate layer 9 has insulating properties, it retains electrons near the interface with the green light-emitting layer 10 (interface on the cathode 13 side) and the interface with the blue light-emitting layer 8 (on the anode 3 side). Holes can be retained near the interface)). Therefore, the amount of holes and electrons passing through the intermediate layer 9 can be controlled. As a result, the light emitting element 1 can cause each light emitting layer provided on both sides of the intermediate layer 9 to emit light in a balanced manner.

In addition, since the intermediate layer 9 is made of an inorganic material, the intermediate layer 9 is less likely to be deteriorated compared to the case where the intermediate layer 9 is made of an organic compound, and the above-described function of the intermediate layer 9 is longer. Maintained. As a result, it is possible to prevent a change in the light emission balance of the plurality of light emitting layers and to extend the life.
As the constituent material of the intermediate layer 9, the same constituent material as that of the intermediate layer 7 described above can be used, and may be the same as or different from the constituent material of the intermediate layer 7.

  The average thickness of the intermediate layer 9 is preferably such that electrons and holes can pass through the tunnel effect as in the case of the intermediate layer 7 described above, and specifically, preferably 1 nm or more and 5 nm or less. It is more preferably 1 nm or more and 4 nm or less, and further preferably 1 nm or more and 3 nm or less. Thereby, the flow of carriers (holes and electrons) between the blue light emitting layer 8 and the green light emitting layer 10 can be appropriately limited.

The average thickness of the intermediate layer 9 may be the same as or different from the average thickness of the intermediate layer 7 described above.
Further, when the intermediate layer 9 is used in combination of two or more kinds of insulating inorganic materials, the intermediate layer 9 may be made of a mixed material obtained by mixing two or more kinds of insulating inorganic materials, or may be made of different insulating inorganic materials. The plurality of layers may be laminated.
The intermediate layer 9 can be omitted.

(Green light emitting layer)
The green light emitting layer (third light emitting layer) 10 includes a green light emitting material (third light emitting material) that emits green light (third color).
Such a green light emitting material is not particularly limited, and various green fluorescent materials and green phosphorescent materials can be used singly or in combination.

  The green fluorescent material is not particularly limited as long as it emits green fluorescence. For example, a quinacridone such as a coumarin derivative, a quinacridone derivative represented by the following formula (7) and a derivative thereof, 9,10-bis [(9 -Ethyl-3-carbazole) -vinylenyl] -anthracene, poly (9,9-dihexyl-2,7-vinylenefluorenylene), 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)], etc., and one of these may be used alone or two or more may be used. It can also be used in conjunction seen.

The green phosphorescent material is not particularly limited as long as it emits green phosphorescence, and examples thereof 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-phenyl-pyridinium sulfonate -N, ^{C 2} ') iridium (acetylacetonate), fac - tris [ 5-fluoro-2- (5-trifluoromethyl-2-pyridine) phenyl-C, N] iridium.

Further, the green light emitting layer 10 may contain a host material. As the host material of the green light emitting layer 10, the same host material as the host material of the red light emitting layer 6 described above can be used.
When the green light emitting layer 10 contains a host material, the content (dope amount) of the green light emitting material in the green light emitting layer 10 is preferably 0.01 to 20 wt%, more preferably 1 to 15 wt%. preferable. By setting the content of the green light emitting material in such a range, the light emission efficiency can be optimized, and the green light emitting layer 10 can be formed while balancing the light emitting amount of the red light emitting layer 6 and the blue light emitting layer 8. Can emit light.

(Electron transport layer)
The electron transport layer 11 has a function of transporting electrons injected from the cathode 13 through the electron injection layer 12 to the green light emitting layer 10.

As a constituent material (electron transport material) of the electron transport layer 11, for example, 8-quinolinol and its derivatives such as tris (8-quinolinolato) aluminum (Alq ₃ ) represented by the following formula (8) are used as a ligand. Quinoline derivatives such as organometallic complexes, azaindolizine derivatives such as compounds represented by the following formula (9), oxadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives These can be used, and one or more of these can be used in combination.

In addition, when the electron transport layer 11 is used in combination of two or more of the electron transport materials as described above, the electron transport layer 11 may be composed of a mixed material in which two or more electron transport materials are mixed, or different. You may be comprised by laminating | stacking the some layer comprised with the electron transport material.
When the electron transport layer 11 is formed by laminating a plurality of layers made of different electron transport materials, the constituent material of the anode side layer (first electron transport layer) is an electron in the green light emitting layer 10. Any quinoline derivative such as an anthracene derivative or an organometallic complex having an 8-quinolinol or its derivative such as tris (8-quinolinolato) aluminum (Alq ₃ ) as a ligand can be used. In addition, as a constituent material of the cathode side layer (second electron transport layer), the electron injection layer 12 can receive electrons and inject electrons into the first electron transport layer. For example, an azaindolizine derivative such as a compound represented by the above formula (9), a pyridine derivative, a phenanthrin derivative, or the like is preferably used.

The average thickness of the first electron transport layer is preferably thinner than the average thickness of the second electron transport layer, and is 0.1 times the average thickness of the second electron transport layer. More preferably, it is 0.4 times or less. Thereby, the electron transport property and the electron injection property of the electron transport layer 11 can be made excellent.
Although the average thickness of the electron carrying layer 11 is not specifically limited, It is preferable that it is about 0.5-100 nm, and it is more preferable that it is about 1-50 nm.

(Electron injection layer)
The electron injection layer 12 has a function of improving the efficiency of electron injection from the cathode 13.
Examples of the constituent material (electron injection material) of the electron injection layer 12 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 obtain high luminance by forming the electron injection layer 12 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 12 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.

(Sealing member)
The sealing member 15 is provided so as to cover the anode 3, the laminate 14, and the cathode 13, and has a function of hermetically sealing them and blocking oxygen and moisture. By providing the sealing member 15, 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 15 include Al, Au, Cr, Nb, Ta, Ti, alloys containing these, silicon oxide, various resin materials, and the like. In addition, when using the material which has electroconductivity as a constituent material of the sealing member 15, in order to prevent a short circuit, it is required between the sealing member 15 and the anode 3, the laminated body 14, and the cathode 13. Accordingly, it is preferable to provide an insulating film.
Further, the sealing member 15 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 device 1 configured as described above, since the intermediate layer 7 suitably adjusts the transport balance of holes and electrons between the red light emitting layer 6 and the blue light emitting layer 8, the red light emitting layer 6 and The blue light emitting layer 8 can emit light in a balanced and efficient manner. Similarly, since the intermediate layer 9 suitably adjusts the transport balance of holes and electrons between the blue light emitting layer 8 and the green light emitting layer 10, the blue light emitting layer 8 and the green light emitting layer 10 are balanced and efficiently. Can emit light.

For this reason, the light emitting element 1 can emit R (red), G (green), and B (blue) in a well-balanced manner to emit white light.
In particular, in the light emitting element 1, since the intermediate layers 7 and 9 are each made of an inorganic material, the intermediate layers 7 and 9 are prevented from being deteriorated by electrons and holes. As a result, the red light emitting layer 6, the blue light emitting layer 8, and the green light emitting layer 10 can emit light in a balanced manner (that is, white light emission in the present embodiment) over a long period of time.
The above light emitting element 1 can be manufactured as follows, for example.

[1] First, the substrate 2 is prepared, and the anode 3 is formed on the substrate 2.
The anode 3 is formed by, for example, chemical vapor deposition (CVD) such as plasma CVD or thermal CVD, dry plating such as vacuum deposition, wet plating such as electrolytic plating, sputtering, thermal spraying, sol-gel, MOD. It can be formed by bonding metal foils or the like.

[2] Next, the hole injection layer 4 is formed on the anode 3.
The hole injection layer 4 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, the hole injection layer 4 is dried (desolvent or desolvent) after supplying the hole injection layer forming material obtained by, for example, dissolving the hole injection material in a solvent or dispersing in a dispersion medium onto the anode 3. It can also be formed by using a dispersion medium.

As a method for supplying the hole injection layer forming 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 hole injection layer 4 can be formed relatively easily.
Examples of the solvent or dispersion medium used for the preparation of the hole injection layer forming material include various inorganic solvents, various organic solvents, or 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 hole transport layer 5 is formed on the hole injection layer 4.
The hole transport layer 5 can be formed, for example, by a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering.
Further, by supplying a hole transport layer forming material obtained by dissolving a hole transport material in a solvent or dispersing in a dispersion medium onto the hole injection layer 4, drying (desolvation or dedispersion medium) is performed. Can also be formed.

[4] Next, the red light emitting layer 6 is formed on the hole transport layer 5.
The red light emitting layer 6 can be formed by a vapor phase process using, for example, a CVD method, a dry plating method such as vacuum deposition or sputtering, or the like.
[5] Next, the intermediate layer 7 is formed on the red light emitting layer 6.
The intermediate layer 7 can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition, sputtering, or the like.

[6] Next, the blue light emitting layer 8 is formed on the intermediate layer 7.
The blue light emitting layer 8 can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering.
[7] Next, the intermediate layer 9 is formed on the blue light emitting layer 8.
The intermediate layer 9 can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum evaporation or sputtering.

[8] Next, the green light emitting layer 10 is formed on the intermediate layer 9.
The green light emitting layer 10 can be formed, for example, by a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering.
[9] Next, the electron transport layer 11 is formed on the green light emitting layer 10.
The electron transport layer 11 can be formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition, sputtering, or the like.

[10] Next, the electron injection layer 12 is formed on the electron transport layer 11.
When an inorganic material is used as the constituent material of the electron injection layer 12, the electron injection layer 12 is formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering, and application and baking of inorganic fine particle ink. Etc. can be used.
[11] Next, the cathode 13 is formed on the electron injection layer 12.
The cathode 13 can be formed by using, for example, a vacuum deposition method, a sputtering method, bonding of metal foil, 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 15 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 as, for example, a light source. Moreover, a display apparatus (display apparatus of this invention) can be comprised by arrange | positioning the several light emitting element 1 in matrix form.
The driving method of the display device is not particularly limited, and may be either an active matrix method or a passive matrix method.

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.
The display device 100 shown in FIG. 2 includes a substrate 21 and a plurality of light emitting elements 1 _R , 1 _G , 1 _B and color filters 19 _R , 19 _G provided corresponding to the sub-pixels 100 _R , 100 _G , 100 _B. , 19 _B and a plurality of driving transistors 24 for driving the light emitting elements 1 _R , 1 _G , 1 _B , respectively. Here, the display device 100 is a display panel having a top emission structure.

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 planarizing layer, light emitting elements 1 _R , 1 _G , 1 _B are provided corresponding to the driving transistors 24.
In the light emitting element 1 _R , a reflective film 32, a corrosion preventing film 33, an anode 3, a laminate (organic EL light emitting unit) 14, a cathode 13, and a cathode cover 34 are laminated in this order on the planarizing layer 22. In this embodiment, the anode 3 of each light emitting element 1 _R , 1 _G , 1 _B constitutes a pixel electrode, and is electrically connected to the drain electrode 245 of each driving transistor 24 by a conductive portion (wiring) 27. Yes. The cathodes 13 of the light emitting elements 1 _R , 1 _G , 1 _B are common electrodes.

The configurations of the light emitting elements 1 _G and 1 _B are the same as the configuration of the light emitting element 1 _R. 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 between the light emitting elements 1 _R , 1 _G , and 1 _B depending on the wavelength of light.
A partition wall 31 is provided between the adjacent light emitting elements 1 _R , 1 _G , 1 _B. An epoxy layer 35 made of an epoxy resin is formed on the light emitting elements 1 _R , 1 _G , 1 _B so as to cover them.

The color filters 19 _R , 19 _G , and 19 _B are provided on the epoxy layer 35 described above corresponding to the light emitting elements 1 _R , 1 _G , and 1 _B.
The color filter 19 _R is for converting the white light W from the light emitting element 1 _R red. The color filter 19 _G is for converting the white light W from the light emitting element 1 _G to green. The color filter 19 _B is for converting the white light W from the light emitting element 1 _B to blue. By using such color filters 19 _R , 19 _G and 19 _{B in combination} with the light emitting elements 1 _R , 1 _G and 1 _B , a full color image can be displayed.

A light shielding layer 36 is formed between the adjacent color filters 19 _R , 19 _G , and 19 _B. Thereby, it is possible to prevent the unintended subpixels 100 _R , 100 _G , and 100 _B from emitting light.
A sealing substrate 20 is provided on the color filters 19 _R , 19 _G , 19 _B and the light shielding layer 36 so as to cover them.
The display device 100 as described above may be a monochrome display, and color display is also possible by selecting a light emitting material used for each light emitting element 1 _R , 1 _G , 1 _B.

Such a display device 100 (the display device of the present invention) can be incorporated into various electronic devices.
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 input / output terminal 1314 for data communication 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 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, in the above-described embodiment, the light emitting element has three light emitting layers. However, the light emitting layer may be two layers or four or more layers. Further, the emission color of the light emitting layer is not limited to R, G, and B in the above-described embodiment. Moreover, the luminescent color of a some light emitting layer may mutually be the same, or may differ. Further, when the light emitting colors of the plurality of light emitting layers are different from each other, the stacking order of the light emitting layers is not particularly limited.
Moreover, the intermediate | middle layer should just be provided between the at least 1 interlayer of light emitting layers, and may have an intermediate | middle layer of two or more layers.

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 50 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, a tetraamine compound represented by the above formula (1) was deposited on the ITO electrode by a vacuum deposition method to form a hole injection layer having an average thickness of 50 nm.
<3> Next, on the hole injection layer, N, N′-bis (1-naphthyl) -N, N′-diphenyl [1,1′-biphenyl] -4, represented by the formula (2), 4′-diamine (α-NPD) was deposited by a vacuum deposition method to form a hole transport layer having an average thickness of 20 nm.

<4> Next, the constituent material of the red light emitting layer was vapor-deposited on the hole transport layer by a vacuum vapor deposition method to form a red light emitting layer (first light emitting layer) having an average thickness of 20 nm.
As a constituent material of the red light emitting layer, a tetraaryldiindenoperylene derivative (RD-1) represented by the above formula (3) is used as a red light emitting material (guest material), and a host material is represented by the above formula (5). Rubrene derivative (RB) was used. The content (dope concentration) of the light emitting material (dopant) in the red light emitting layer was 1.0 wt%.

<5> Next, the constituent material of the intermediate layer was deposited on the red light emitting layer (first light emitting layer) by a vacuum vapor deposition method to form an intermediate layer having an average thickness of 1 nm. LiF was used as a constituent material of the intermediate layer.
<6> Next, the constituent material of the red light emitting layer was vapor-deposited on the intermediate layer by a vacuum vapor deposition method to form a red light emitting layer (second light emitting layer) having an average thickness of 20 nm.
As a constituent material of the red light emitting layer, a tetraaryldiindenoperylene derivative (RD-1) represented by the above formula (3) is used as a red light emitting material (guest material), and a host material is represented by the above formula (5). Rubrene derivative (RB) was used. The content (dope concentration) of the light emitting material (dopant) in the red light emitting layer was 1.0 wt%.

<7> Next, tris (8-quinolinolato) aluminum (Alq ₃ ) represented by the above formula (8) is formed on the red light emitting layer (second light emitting layer) by a vacuum deposition method, and the average thickness is measured. A 5 nm first electron transport layer was formed.
<8> Next, an azaindolizine derivative represented by the formula (9) was formed on the first electron transport layer by a vacuum deposition method, thereby forming a second electron transport layer having an average thickness of 25 nm. .
Thereby, an electron transport layer in which the first electron transport layer and the second electron transport layer were laminated was obtained.

<9> Next, on the second electron transport layer of the electron transport layer, lithium fluoride (LiF) was formed by a vacuum vapor deposition method to form an electron injection layer having an average thickness of 1 nm.
<10> 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 150 nm made of Al was formed.
<11> Next, a glass protective cover (sealing member) was placed over the formed layers, and fixed and sealed with an epoxy resin.
The light emitting device was manufactured through the above steps.

(Example 2)
A light emitting device was manufactured in the same manner as in Example 1 except that the average thickness of the intermediate layer was 5 nm.
Example 3
The average thickness of the first light emitting layer was set to 10 nm, and an intermediate layer (second intermediate layer) and a third light emitting layer were sequentially formed between the second light emitting layer and the first electron transporting layer. Except for the above, a light emitting device was manufactured in the same manner as in Example 1 described above.

Specifically, after the formation of the second light-emitting layer, the constituent material of the intermediate layer is deposited on the second light-emitting layer by a vacuum evaporation method, and an intermediate layer (second intermediate layer) having an average thickness of 1 nm is formed. Formed. LiF was used as a constituent material of the intermediate layer.
Then, the constituent material of the red light emitting layer was vapor-deposited on the second intermediate layer by a vacuum evaporation method to form a red light emitting layer (third light emitting layer) having an average thickness of 10 nm.

As a constituent material of the red light emitting layer, a tetraaryldiindenoperylene derivative (RD-1) represented by the above formula (3) is used as a red light emitting material (guest material), and a host material is represented by the above formula (5). Rubrene derivative (RB) was used. The content (dope concentration) of the light emitting material (dopant) in the red light emitting layer was 1.0 wt%.
Then, similarly to Example 1 described above, a first electron transport layer, a second electron transport layer, an electron injection layer, and a cathode were sequentially formed on the third light emitting layer, followed by sealing.
A light emitting device was manufactured as described above.

(Comparative Example 1)
A light emitting device was manufactured in the same manner as in Example 1 except that the intermediate layer and the second light emitting layer were omitted and the average thickness of the first light emitting layer was 40 nm.
(Comparative Example 2)
As a constituent material of the intermediate layer, an organic material, specifically, N, N′-bis (1-naphthyl) -N, N′-diphenyl [1,1′-biphenyl]-represented by the formula (2) is used. Example 1 except that a mixed material of 4,4′-diamine (α-NPD) and a rubrene derivative (RB) represented by the formula (5) was used, and the average thickness of the intermediate layer was 10 nm. In the same manner as in Example 1, a light emitting device was produced.
Here, in forming the intermediate layer, α-NPD and rubrene derivative (RB) were co-deposited by a vacuum evaporation method to form the intermediate layer. The weight ratio of α-NPD and rubrene derivative (RB) in the intermediate layer was set to 1: 1.

(Comparative Example 3)
The intermediate layer and the second light emitting layer are omitted, the average thickness of the first light emitting layer is 40 nm, and the intermediate layer is replaced between the first light emitting layer and the second light emitting layer to transport holes. A light emitting device was manufactured in the same manner as in Example 1 except that the layer was provided between the first light emitting layer and the first light emitting layer.
(Comparative Example 4)
A light emitting device was manufactured in the same manner as in Example 1 except that the second light emitting layer was omitted and the average thickness of the first light emitting layer was 40 nm.

2. Evaluation 2-1. Evaluation of Luminous Life For each Example and each Comparative Example, while measuring the luminance using a luminance meter, a constant current was applied to the light emitting element using a DC power source at a current density such that the initial luminance was 60000 cd / m ^2. In the meantime, the luminance was measured using a luminance meter, and the time during which the luminance was 90% of the initial luminance (LT90) was measured. And the time of LT90 in a comparative example was normalized as 1.00, and the time of LT90 of each comparative example and each example was relatively evaluated.

2-2. Evaluation of luminous efficiency For each example and each comparative example, while measuring the luminance using a luminance meter, a current was passed through the light emitting element using a direct current power source so that the luminance was 60000 cd / m ² . The current was measured. Further, the driving voltage applied to the light emitting element at this time was measured in the same manner.
2-3. Evaluation of light emission balance For each example and each comparative example, while measuring the luminance using a luminance meter, a current was passed through the light emitting element using a DC power source so that the luminance was 60000 cd / m ² . The chromaticity was measured using a chromaticity meter.
The evaluation results are shown in Table 1.

  As is clear from Table 1, each of the light emitting devices of each example was excellent in light emission balance and had a longer life than the light emitting device of Comparative Example 1 serving as a reference. In particular, the life was longer in the case of two intermediate layers than in the case of one intermediate layer. On the other hand, when the intermediate layer was used between the hole transport layer or the electron transport layer, the lifetime was shortened. Further, when an organic material was used as the intermediate layer, a long life effect was not so much seen.

DESCRIPTION OF SYMBOLS 1, 1 _B , 1 _G , 1 _R ... Light emitting element 2 ... Substrate 3 ... Anode 4 ... Hole injection layer 5 ... Hole transport layer 6 ... Red light emitting layer (1st light emitting layer) 7 …… Intermediate layer 8 …… Blue light emitting layer (second light emitting layer) 9 …… Intermediate layer (second intermediate) 10 …… Green light emitting layer (third light emitting layer) 11 …… Electron transporting layer 12 …… Electron injection layer 13... Cathode 14... Laminate 15... Sealing member 19 _B , 19 _G , 19 _R ... Color filter 100 .. Display device 100 _B , 100 _G , 100 _R. 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 wall 32 …… Reflection film 33 …… Corrosion prevention film 3 4 ... Cathode cover 35 ... Epoxy layer 36 ... Light shielding layer 1100 ... Personal computer 1102 ... Keyboard 1104 ... Main body 1106 ... Display unit 1200 ... Mobile phone 1202 ... Operation buttons 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

Claims (8)

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;
A light-emitting element comprising: an intermediate layer that is provided between and in contact with the first light-emitting layer and the second light-emitting layer and is formed of an insulating inorganic material.   The light emitting device according to claim 1, wherein the inorganic material is one or a combination of two or more of metal oxides, metal nitrides, and metal fluorides.   The inorganic material includes one or more of alkali metal oxides, alkali metal nitrides, alkali metal fluorides, alkaline earth metal oxides, alkaline earth metal nitrides, and alkaline earth metal fluorides. The light emitting device according to claim 2, which is a combination.   The light emitting device according to claim 2, wherein the inorganic material is a metal fluoride.   The light emitting device according to any one of claims 1 to 4, wherein an average thickness of the intermediate layer is 1 nm or more and 5 nm or less. 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;
A third light emitting layer that is provided between the cathode and the second light emitting layer and emits light when energized between the anode and the cathode;
A first intermediate layer formed of an insulating inorganic material provided between and in contact with the first light emitting layer and the second light emitting layer;
A light emitting element comprising: a second intermediate layer formed of an insulating inorganic material provided between and in contact with the second light emitting layer and the third light emitting layer.   A display device comprising the light-emitting element according to claim 1.   An electronic apparatus comprising the display device according to claim 7.

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