JP5077055B2 - LIGHT EMITTING ELEMENT, DISPLAY DEVICE, AND ELECTRONIC DEVICE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element which makes in good balance a plurality of light-emitting layers laminated emit lights and is improved in durability (lifetime), to provide a display which includes this light-emitting element and can display a high-quality image for a long period, and to provide electronic equipment. <P>SOLUTION: The light-emitting element 1 includes a cathode 12, an anode 3, a first light-emitting layer 6 which is installed between the cathode 12 and the anode 3 and emits red light, a second light-emitting layer 8 which is installed between the first light-emitting layer 6 and the cathode 12 and emits blue light, and an interlayer 7 which is installed between the first light-emitting layer 6 and the second light-emitting layer 8 so as to contact these, and includes a function to restrict movement of electrons from the second light-emitting layer 8 to the first light-emitting layer 6. The interlayer 7 is constituted including a naphthalene derivative. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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 device, for example, a device in which a plurality of light emitting layers having different colors are stacked between a cathode and an anode is known (see, for example, Patent Document 1).

In the light emitting element according to Patent Document 1, an intermediate layer that restricts the movement of carriers (particularly, holes) is provided between two light emitting layers. As a result, the amount of carriers injected into each light emitting layer can be optimized, and the two light emitting layers can emit light in a balanced manner.
However, the light emitting device according to Patent Document 1 has low durability because the intermediate layer is composed only of a general hole transporting material or electron transporting material. This is considered to be due to the electrochemically unstable intermediate layer that has become an anionic state due to the injection of electrons into the intermediate layer and is degraded by decomposition or the like.

JP 2007-287681 A

  An object of the present invention is to provide a light emitting element that can emit light in a balanced manner and improve durability (life), and to display a high-quality image over a long period of time. An object of the present invention is to provide a display device and an electronic device that can be used.

Such an object is achieved by the present invention described below.
The light emitting device of the present invention comprises a cathode,
The anode,
A first light-emitting layer provided between the cathode and the anode and configured to include a first light-emitting material that emits light in a first color;
A second light-emitting layer that is provided between the first light-emitting layer and the cathode and includes a second light-emitting material that emits light in a second color different from the first color;
An intermediate provided between the first light emitting layer and the second light emitting layer so as to be in contact therewith and having a function of restricting the movement of electrons from the second light emitting layer to the first light emitting layer. And having a layer
The intermediate layer includes a naphthalene derivative represented by a general formula C _x H _y (where x and y are natural numbers, respectively), a hole transporting material having higher hole transportability than the naphthalene derivative, It is characterized by including.
Accordingly, the first light emitting layer and the second light emitting layer can emit light with a good balance, and the durability (life) of the light emitting element can be improved.
Here, since the intermediate layer includes a hole transporting material having a hole transporting property higher than that of the naphthalene derivative in addition to the naphthalene derivative, the intermediate layer is formed from the first light emitting layer. Thus, the amount of holes moving to the second light emitting layer can be easily adjusted.

In the light emitting device of the present invention, the naphthalene derivative preferably has a molecular weight of 400 to 1,000.
Thereby, a homogeneous intermediate layer can be formed relatively easily by the vapor phase film forming method. In addition, the crystallinity of the naphthalene derivative can be suppressed to prevent the intermediate layer from being altered or deteriorated.

In the light emitting device of the present invention, it is preferable that the naphthalene derivative has two or more naphthyl groups introduced therein.
As a result, the intermediate layer can be made homogeneous and excellent in durability while the electronic block property and electronic resistance of the naphthalene derivative are excellent.
In the light emitting device of the present invention, the absorption peak wavelength of the naphthalene derivative is preferably less than 450 nm.
In the second light-emitting layer, an anthracene derivative is generally used as a host material that uses the first light-emitting material as a guest material. Since the absorption peak wavelength of the anthracene derivative is about 450 nm, by setting the absorption peak wavelength of the naphthalene derivative in the range as described above, the intermediate layer can be relatively easily and reliably separated from the second light emitting layer by the first light emitting layer. The movement of electrons to the light emitting layer can be restricted.

In the light emitting device of the present invention, the naphthalene derivative preferably has an electron affinity of 2 to 3 eV.
Thereby, an intermediate | middle layer can restrict | limit the movement of the electron from a 2nd light emitting layer to a 1st light emitting layer, optimizing the molecular weight of a naphthalene derivative.
In the light emitting device of the present invention, the ionization potential of the hole transporting material is preferably 5 to 6.2 eV.
Accordingly, holes can be smoothly transferred from the first light emitting layer to the second light emitting layer through the intermediate layer while optimizing the molecular weight of the naphthalene derivative.

In the light emitting device of the present invention, it is preferable that an ionization potential of a material which is hardly oxidized among the materials constituting the intermediate layer is 5 to 6.2 eV .

In the light emitting device of the present invention, the hole transporting material preferably contains an amine compound.
The amine compound is excellent in hole transportability. Therefore, holes can be transferred very smoothly from the first light emitting layer to the second light emitting layer through the intermediate layer.
In the light emitting device of the present invention, it is preferable that the intermediate layer includes an electron transporting material having an electron transporting property higher than that of the naphthalene derivative in addition to the naphthalene derivative.
Thereby, the amount of electrons moving from the second light emitting layer to the first light emitting layer via the intermediate layer can be easily adjusted.

In the light emitting device of the present invention, the electron transporting material preferably contains an anthracene derivative or a dianthracene derivative.
An anthracene derivative or a dianthracene derivative is not only excellent in electron transport properties, but also excellent in electron resistance. Therefore, it is possible to easily adjust the amount of electrons moving from the second light emitting layer to the first light emitting layer through the intermediate layer while making the intermediate layer excellent in durability.

In the light-emitting element of the present invention, the second light-emitting layer includes a second host material using the second light-emitting material as a guest material in addition to the second light-emitting material, The second host material preferably contains an anthracene derivative.
Thereby, the intermediate layer can restrict the movement of electrons from the second light emitting layer to the first light emitting layer relatively easily and reliably.

In the light-emitting element of the present invention, the first light-emitting layer includes a host material that uses the first light-emitting material as a guest material in addition to the first light-emitting material. The light emitting material preferably contains a tetracene derivative or a perylene derivative.
As a result, holes from the first light emitting layer to the second light emitting layer can be more smoothly passed through the intermediate layer relatively easily and reliably.

In the light emitting device of the present invention, a third light emitting material that is provided between the second light emitting layer and the cathode and emits light in a third color different from the first color and the second color is provided. It is preferable to include a third light-emitting layer that is included.
Thereby, durability can be aimed at, making the 1st light emitting layer, the 2nd light emitting layer, and the 3rd light emitting layer emit light with good balance.

In the light-emitting element of the present invention, the first light-emitting material emits red light, the second light-emitting material and the third light-emitting material emit one green light, and the other It is preferable that it emits blue light.
Thereby, R (red), G (green), and B (blue) can be light-emitted with good balance, and white light can be emitted.
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.
An electronic apparatus according to the present invention includes the display device according to the present invention.
Thereby, a high quality image can be displayed over a long period of time.

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 first light emitting layer (red light emitting layer) 6, an intermediate layer 7, and a second light emitting layer (blue light emitting layer) 8. The third light emitting layer (green light emitting layer) 9, the electron transport layer 10, the electron injection layer 11, and the cathode 12 are laminated in this order.
In other words, the light emitting element 1 includes the hole injection layer 4, the hole transport layer 5, the first light emitting layer 6, the intermediate layer 7, the second light emitting layer 8, the third light emitting layer 9, and the electron transport layer 10. A laminate 15 in which the electron injection layer 11 and the cathode 12 are laminated in this order is interposed between two electrodes (between the anode 3 and the cathode 12).

The entire light emitting element 1 is provided on the substrate 2 and is sealed with a sealing member 13.
In such a light emitting element 1, electrons are supplied (injected) from the cathode 12 side to the light emitting layers of the first light emitting layer 6, the second light emitting layer 8, and the third light emitting layer 9. In addition, holes are supplied (injected) from the anode 3 side. 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 R (red), G (green), and B (blue) to emit 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.

(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), tetraamine compounds represented by the following chemical formula 1 and derivatives thereof, and the like can be used, and one or more of these can be used in combination.

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 first light emitting layer 6.
As the constituent material of the hole transport layer 5, various p-type polymer materials and various p-type low-molecular materials can be used alone or in combination. For example, N, N′— Di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPD), N, N′-diphenyl-N, N′-bis (3-methylphenyl) Tetraarylbenzidine derivatives such as -1,1′-diphenyl-4,4′-diamine (TPD), tetraaryldiaminofluorene compounds or derivatives thereof (amine compounds), and the like, one or two of these A combination of more than one species 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.

(First light emitting layer)
The first light-emitting layer 6 includes a first light-emitting material that emits light in a first color and a first host material that uses the first light-emitting material as a guest material. Such a first light-emitting layer 6 can be formed, for example, by doping the first host material as a dopant with the first light-emitting material that is a guest material.

The first light emitting material is a red light emitting material that emits red light.
Such a red light emitting material is not particularly limited, and a red fluorescent material can be suitably used by using various red fluorescent materials and red phosphorescent materials in combination of one or more kinds.
The red fluorescent material is not particularly limited as long as it emits red fluorescence. For example, perylene derivatives, 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) quinolidin-9-yl) ethenyl)- 4H-pyran-4H-ylidene) propanedinitrile (DCJTB), 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -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).

Among the above-mentioned, the red light emitting material preferably contains a perylene derivative. A perylene derivative is a light-emitting material with particularly high luminous efficiency. The perylene derivative has a particularly excellent function of capturing electrons. For this reason, the electrons injected from the cathode 12 side can be reliably captured by the first light-emitting layer 6 and can be prevented from being injected into the hole transport layer 5. As a result, it is possible to prevent the constituent materials of the hole injection layer 4 and the hole transport layer 5 from being reduced and deteriorated by electrons.
In particular, as the perylene derivative used for the red light-emitting material, for example, a tetraphenyldiindenoperylene derivative such as a compound as shown in the following chemical formula 3 is preferably used.

The first host material having such a red light emitting material as a guest material recombines holes and electrons to generate excitons, and transfers the exciton energy to the red light emitting material (Förster transfer). Or a Dexter movement) to excite the red light emitting material.
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, tetracene derivatives (naphthacene derivatives) such as bis p-biphenylylnaphthacene shown in the following chemical formula 4, perylene derivatives such as bis-ortho-biphenylylperylene shown in chemical formula 5, distyrylbenzene derivatives, distyrylamine Derivatives, quinolinolato metal complexes such as tris (8-quinolinolato) aluminum complex (Alq ₃ ), triarylamine derivatives such as tetramers of triphenylamine, oxadiazole derivatives, silole derivatives, dicarbazole derivatives, oligothiophene derivatives , Benzopyran derivatives, triazole derivatives Examples include benzoxazole derivatives, benzothiazole derivatives, quinoline derivatives, 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi), and one of these is used alone or in combination of two or more. It can also be used.

Among these, the first light emitting material preferably includes a tetracene derivative or a perylene derivative as described above. Thereby, holes from the first light emitting layer 6 to the second light emitting layer 8 can be transferred more smoothly through the intermediate layer 7.
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 material (guest material) and the host material as described above are used, the content (doping amount) of the red light emitting material in the first light emitting layer 6 is preferably 0.1 to 10 wt%. More preferably, it is 1-5 wt%. By setting the content of the red light emitting material in such a range, the light emission efficiency can be optimized, and the amount of light emitted from the second light emitting layer 8 and the third light emitting layer 9 described later is balanced. In addition, the first light emitting layer 6 can emit light.

In addition, the red light-emitting material as described above has a relatively small band gap, easily captures holes and electrons, and easily emits light. Therefore, by providing the red light-emitting layer on the anode 3 side, the blue light-emitting layer and the green light-emitting layer 9 which have a large band gap and are difficult to emit light can be used as the cathode 12 side, and each light-emitting layer can emit light in a balanced manner.
Moreover, the average thickness of the 1st light emitting layer 6 is although it does not specifically limit, It is preferable that it is 1-100 nm, It is more preferable that it is 3-50 nm, It is further more preferable that it is 5-30 nm.

(Middle layer)
The intermediate layer 7 is provided between and in contact with the first light-emitting layer 6 and the second light-emitting layer 8 described later.
The intermediate layer 7 has a function of limiting the movement of electrons from the second light emitting layer 8 to the first light emitting layer 6 (electron blocking property). As a result, a necessary amount of electrons can be supplied to the second light emitting layer 8. In other words, electrons can be supplied to the first light emitting layer 6 and the second light emitting layer 8 in a balanced manner. As a result, the first light emitting layer 6 and the second light emitting layer 8 can emit light with a desired balance in a well-balanced manner.

  The second intermediate layer 7 also has a function of preventing exciton energy from moving between the first light emitting layer 6 and the second light emitting layer 8. With this function, excitons generated in the first light-emitting layer 6 are reliably recombined in the first light-emitting layer 6 to emit light, and excitons generated in the second light-emitting layer 8 are second emitted. The layer 8 can reliably recombine and emit light. As a result, the first light emitting layer 6 and the second light emitting layer 8 can each emit light efficiently.

In particular, the intermediate layer 7 includes a naphthalene derivative.
Accordingly, the first light emitting layer and the second light emitting layer can emit light with a good balance, and the durability (life) of the light emitting element can be improved.
Naphthalene derivatives have excellent electron blocking properties. Therefore, the function of restricting the movement of electrons from the second light emitting layer 8 to the first light emitting layer 6 as described above can be more reliably exhibited. In particular, as will be described later, when an anthracene derivative is used as the second host material of the second light-emitting layer 8, the intermediate layer 7 containing a naphthalene derivative can exhibit excellent electron blocking properties.

Naphthalene derivatives are also extremely excellent in resistance to electrons (electron resistance). Therefore, the intermediate layer 7 containing a naphthalene derivative is excellent in durability. As a result, the durability of the light emitting element 1 can be improved.
The naphthalene derivative used for the intermediate layer 7 can be selected according to the constituent material, thickness, and driving voltage of the light-emitting element 1 of each light-emitting layer, and the function of the intermediate layer 7 as described above (at least electron blocking property). Any naphthalene derivative can be used as long as it can exhibit the above.

Moreover, it is preferable that the molecular weight of a naphthalene derivative is 400-1000, It is more preferable that it is 500-1000, It is further more preferable that it is 600-1000. When the molecular weight is within this range, the naphthalene derivative can be formed relatively easily by a vapor phase film forming method such as vapor deposition. Since the intermediate layer 7 formed using the vapor deposition method is uniform, the characteristics of the light-emitting element 1 can be improved. In addition, since the crystallinity of the naphthalene derivative can be suppressed, it is possible to prevent the crystal state in the intermediate layer 7 from changing even when the temperature of the intermediate layer 7 is increased by driving the light emitting element 1 or the like. Thereby, alteration, deterioration, etc. of the intermediate layer 7 can be prevented, and as a result, it is possible to prevent the characteristics of the intermediate layer 7 (and thus the characteristics of the light emitting element 1) from changing (fluctuating). In this case, the naphthalene derivative is preferably represented by the general formula C _x H _y (where x and y are natural numbers, respectively).

  On the other hand, when the molecular weight of the naphthalene derivative is less than the lower limit, the crystallinity of the naphthalene derivative becomes too high, and when the intermediate layer 7 is heated during driving of the light emitting element 1 or the like, As a result, the characteristics of the intermediate layer 7 (and thus the characteristics of the light-emitting element 1) may change (change). In addition, it is difficult to control the rate when forming a film by a vapor deposition method such as vapor deposition. On the other hand, when the molecular weight of the naphthalene derivative exceeds the above upper limit, it is difficult to form a film because it is easily decomposed and modified during vapor phase film formation such as vapor deposition.

Moreover, as a naphthalene derivative having a molecular weight in the range as described above, it is preferable to use one having two or more naphthyl groups introduced therein. Thereby, it is possible to make the intermediate layer 7 homogeneous and excellent in durability while improving the electronic block property and electron resistance of the naphthalene derivative.
Further, the absorption peak wavelength of the naphthalene derivative is preferably less than 450 nm, and more preferably 300 to 450 nm. In general, an anthracene derivative is used for the second light emitting layer 8 as a second host material of a second light emitting material described later. Since the absorption peak wavelength of the anthracene derivative is about 450 nm, by setting the absorption peak wavelength of the naphthalene derivative in the range as described above, the intermediate layer 7 can be relatively easily and reliably formed from the second light emitting layer 8 to the second light emitting layer 8. The movement of electrons to one light emitting layer 6 can be restricted.

Further, the electron affinity (LUMO level) of the naphthalene derivative having the absorption peak wavelength in the range as described above is preferably 2 to 3 eV, and more preferably 2 to 2.5 eV. Thereby, the intermediate layer 7 can restrict the movement of electrons from the second light emitting layer 8 to the first light emitting layer 6 while optimizing the molecular weight of the naphthalene derivative.
The ionization potential (HOMO level) of a naphthalene derivative having an absorption peak wavelength in the range as described above is preferably 5 to 6.2 eV, more preferably 5 to 5.8 eV. More preferably, it is 7 to 5.8 eV. Thereby, holes can be smoothly transferred from the first light emitting layer 6 to the second light emitting layer 8 through the intermediate layer 7 while optimizing the molecular weight of the naphthalene derivative.
From the above viewpoint, examples of the naphthalene derivative in the intermediate layer 7 include compounds shown in the following chemical formula 6.

The content of the naphthalene derivative in the intermediate layer 7 is not particularly limited, but is preferably 10 to 100 wt%, more preferably 50 to 90 wt%, and further preferably 60 to 80 wt%. preferable.
In addition to the naphthalene derivative as described above, the intermediate layer 7 preferably includes a hole transporting material having a hole transporting property higher than that of the naphthalene derivative. In general, it is difficult for a naphthalene derivative to satisfy the ionization potential as described above. Therefore, the hole transportability of the intermediate layer 7 is improved by configuring the intermediate layer 7 to include a naphthalene derivative and a hole transporting material. In this case, by adjusting the content of the hole transporting material in the intermediate layer 7, the amount of holes moving from the first light emitting layer 6 to the second light emitting layer 8 through the intermediate layer 7 can be easily adjusted. Can be adjusted.

  Such a hole transport material is not particularly limited, and the same material as the hole transport material of the hole transport layer 5 as described above can be used. An amine compound such as a compound is preferably used. Such an amine compound is excellent in hole transportability. Therefore, when the hole transporting material in the intermediate layer 7 contains an amine compound, holes are transferred from the first light emitting layer 6 to the second light emitting layer 8 through the intermediate layer 7 very smoothly. be able to.

The content of the hole transporting material (amine-based material) in the intermediate layer 7 is not particularly limited, but is preferably 0 to 50 wt%, more preferably 10 to 50 wt%, More preferably, it is -40 wt%.
Moreover, it is preferable that the intermediate | middle layer 7 is comprised including the electron transport material which has an electron transport property higher than a naphthalene derivative other than the naphthalene derivative mentioned above. In general, naphthalene derivatives have extremely high electron blocking properties. On the other hand, the intermediate layer 7 must transport electrons from the second light emitting layer 8 to the first light emitting layer 6 to some extent. Therefore, the intermediate layer 7 includes a naphthalene derivative and an electron transporting material to improve the electron transport property of the intermediate layer 7. In this case, the amount of electrons moving from the second light emitting layer 8 to the first light emitting layer 6 through the intermediate layer 7 can be easily adjusted by adjusting the content of the electron transporting material in the intermediate layer 7. can do.

  Such an electron transporting material is not particularly limited, and the same electron transporting material as that of the electron transporting layer 10 as described later can be used. In particular, anthracene such as a compound shown in Chemical Formula 7 below can be used. It is preferable to use a derivative or a dianthracene derivative (hereinafter also simply referred to as “anthracene derivative”). In general, anthracene derivatives are excellent in electron transport properties. Therefore, when the electron transporting material in the intermediate layer 7 contains an anthracene compound, the amount of electrons moving from the second light emitting layer 8 to the first light emitting layer through the intermediate layer 7 is easily adjusted. be able to. In addition, anthracene derivatives are excellent in electron resistance. Therefore, the durability of the mid layer 7 can be made excellent.

The content of the electron transporting material (anthracene derivative) in the intermediate layer 7 is not particularly limited, but is preferably 0 to 50 wt%, more preferably 10 to 50 wt%, and 20 to 40 wt%. % Is more preferable.
Moreover, although the average thickness of the intermediate | middle layer 7 is not specifically limited, It is preferable that it is 1-100 nm, It is more preferable that it is 3-50 nm, It is further more preferable that it is 5-30 nm. Accordingly, the intermediate layer 7 can more reliably prevent exciton energy transfer between the first light emitting layer 6 and the second light emitting layer 8 while suppressing the driving voltage.

  On the other hand, when the average thickness of the intermediate layer 7 exceeds the upper limit, depending on the constituent material of the intermediate layer 7, the driving voltage becomes remarkably high, or the light emission of the light emitting element 1 (particularly white light emission) becomes difficult. Sometimes. On the other hand, if the average thickness of the intermediate layer 7 is less than the lower limit value, the intermediate layer 7 may be formed between the first light emitting layer 6 and the second light emitting layer 8 depending on the constituent material of the intermediate layer 7, the driving voltage, and the like. It is difficult to prevent or suppress energy transfer due to excitons between them, and the resistance of the intermediate layer 7 to carriers and excitons tends to decrease.

(Blue light emitting layer)
The second light-emitting layer 8 includes a second light-emitting material that emits light in the second color and a second host material that uses the second light-emitting material as a guest material. Similar to the first light emitting layer 6 described above, the second light emitting layer 8 can be formed, for example, by doping the second host material as a dopant with the second light emitting material as a guest material. it can.
The second light emitting material is a blue light emitting material that emits blue light.
Such a blue light-emitting material is not particularly limited, and a blue fluorescent material can be suitably used by using various blue fluorescent materials and blue phosphorescent materials in combination of one or more.

  The blue fluorescent material is not particularly limited as long as it emits blue fluorescence. For example, a distyryldiamine derivative, a distyryl derivative, a fluoranthene derivative, a pyrene derivative, a perylene and a perylene derivative, such as a compound shown in the following chemical formula 8, 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-dihexyloxy) Fluorene-2,7-diyl) -ortho Co- (2-methoxy-5- {2-ethoxyhexyloxy} phenylene-1,4-diyl)], poly [(9,9-dioctylfluorene-2,7-diyl) -co- (ethylnylbenzene) Among these, one kind can be used alone or two or more kinds can be used in combination.

In particular, since the distyryldiamine derivative such as the compound shown in Chemical Formula 8 as described above has an excellent function of capturing holes, the second light-emitting layer 8 contains the distyryldiamine derivative. The second light emitting layer 8 can emit light efficiently.
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 ).

  As the second host material, the same material as the first host material of the first light emitting layer 6 described above can be used, but an anthracene derivative such as the compound shown in Chemical Formula 7 as described above is used. Is preferred. When the second host material in the second light emitting layer 8 contains an anthracene derivative, the intermediate layer 7 moves electrons from the second light emitting layer 8 to the first light emitting layer 6 relatively easily and reliably. Can be limited.

When the blue light emitting material (guest material) and the second host material as described above are used, the content (dope amount) of the blue light emitting material in the second light emitting layer 8 is 0.1 to 20 wt%. Is preferable, and it is more preferable that it is 5-20 wt%. By setting the content of the blue light emitting material in such a range, the light emission efficiency can be optimized, and the balance with the light emission amount of the first light emitting layer 6 described above and the third light emitting layer 9 described later. The second light emitting layer 8 can emit light while taking
The average thickness of the second light emitting layer 8 is not particularly limited, but is preferably 1 to 100 nm, more preferably 5 to 60 nm, and further preferably 10 to 40 nm.

(Green light emitting layer)
The third light-emitting layer 9 includes a third light-emitting material that emits light in the third color and a third host material that uses the third light-emitting material as a guest material. Similar to the first light emitting layer 6 described above, the third light emitting layer 9 can be formed, for example, by doping a third host material as a dopant with a third light emitting material as a guest material. it can.

The third light emitting material is a green light emitting material that emits green light.
Such a green light emitting material is not particularly limited, and a green fluorescent material can be suitably used by using various green fluorescent materials and green phosphorescent materials in combination of one or more kinds.
The green fluorescent material is not particularly limited as long as it emits green fluorescence. For example, a coumarin derivative, a quinacridone derivative such as a compound shown in the following chemical formula 9, 9,10-bis [(9-ethyl-3-carbazole, etc. ) -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)] and the like, and one of these may be used alone or two or more of them may be used in combination.

  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-phenylpyridinate-N, C2 ′) iridium (acetylacetonate), fac-tris [5 -Fluoro-2- (5-trifluoromethyl-2-pyridine) phenyl-C, N] iridium.

As the third host material, the same material as the first host material of the first light emitting layer 6 described above can be used, but an anthracene derivative such as the compound shown in Chemical Formula 7 as described above is used. Is preferred.
When the green light emitting material (guest material) and the third host material as described above are used, the content (dope amount) of the green light emitting material in the third light emitting layer 9 is 0.1 to 20 wt%. Is preferable, and it is more preferable that it is 1-20 wt%. By setting the content of the green light emitting material within such a range, it is possible to optimize the light emission efficiency, and to balance the light emission amounts of the first light emitting layer 6 and the second light emitting layer 8 described above. In addition, the third light emitting layer 9 can emit light.
Moreover, the average thickness of the 3rd light emitting layer 9 is although it does not specifically limit, It is preferable that it is 1-100 nm, It is more preferable that it is 5-60 nm, It is further more preferable that it is 10-40 nm.

(Electron transport layer)
The electron transport layer 10 has a function of transporting electrons injected from the cathode 12 through the electron injection layer 11 to the third light emitting layer 9.
Examples of the constituent material (electron transporting material) of the electron transport layer 10 include quinolines such as organometallic complexes having 8-quinolinol or a derivative thereof such as tris (8-quinolinolato) aluminum (Alq ₃ ) as a ligand. Derivatives, oxadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like can be used, and one or more of these can be used in combination.
Although the average thickness of the electron carrying layer 10 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 11 has a function of improving the efficiency of electron injection from the cathode 12.
Examples of the constituent material (electron injection material) of the electron injection layer 11 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, 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 have high luminance by forming the electron injection layer 11 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 11 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 12 is an electrode that injects electrons into the electron transport layer 10 via the electron injection layer 11 described above. As a constituent material of the cathode 12, it is preferable to use a material having a small work function.
Examples of the constituent material of the cathode 12 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 12, 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 12, the electron injection efficiency and stability of the cathode 12 can be improved.
Although the average thickness of such a cathode 12 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 cathode 12 is not particularly required to have light transmittance.

(Sealing member)
The sealing member 13 is provided so as to cover the anode 3, the laminate 15, and the cathode 12, and has a function of hermetically sealing them and blocking oxygen and moisture. By providing the sealing member 13, effects such as improvement in reliability of the light emitting element 1, prevention of deterioration / deterioration (improvement in durability), and the like can be obtained.

Examples of the constituent material of the sealing member 13 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 13, in order to prevent a short circuit, it is required between the sealing member 13 and the anode 3, the laminated body 15, and the cathode 12. Accordingly, it is preferable to provide an insulating film.
Further, the sealing member 13 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.
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 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, a hole transport layer forming material obtained by dissolving a hole transport material in a solvent or dispersing in a dispersion medium is supplied onto the hole injection layer 4 and then dried (desolvent or dedispersion medium). Can also be formed.

[4] Next, the first light emitting layer 6 is formed on the hole transport layer 5.
The first light emitting layer 6 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.
[5] Next, the intermediate layer 7 is formed on the first 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.
Further, as described above, when the intermediate layer 7 is composed of a naphthalene derivative and a hole transporting material and / or an electron transporting material, for example, a hole transporting material and / or an electron transporting material and a naphthalene derivative are used. The intermediate layer 7 can be formed by co-evaporation.

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

[8] Next, the electron transport layer 10 is formed on the third light emitting layer 9.
The electron transport layer 10 can be formed by a vapor phase process using, for example, a CVD method, a dry plating method such as vacuum deposition, sputtering, or the like.
Further, the electron transport layer 10 is formed by supplying an electron transport layer forming material obtained by, for example, dissolving an electron transport material in a solvent or dispersing in a dispersion medium onto the third light emitting layer 9 and then drying (desolving the solvent). Alternatively, it can be formed by dedispersing medium).

[9] Next, the electron injection layer 11 is formed on the electron transport layer 10.
When an inorganic material is used as the constituent material of the electron injection layer 11, the electron injection layer 11 is formed by, for example, a vapor phase process using a CVD method, a dry plating method such as vacuum deposition or sputtering, or coating and baking of inorganic fine particle ink. Etc. can be used.
[10] Next, the cathode 12 is formed on the electron injection layer 11.
The cathode 12 can be formed using, for example, a vacuum evaporation method, a sputtering method, bonding of metal foil, application and baking of metal fine particle ink, and the like.
The light emitting element 1 is obtained through the steps as described above.
Finally, the sealing member 13 is covered so as to cover the obtained light emitting element 1 and bonded to the substrate 2.

According to the light emitting element 1 configured as described above, since the intermediate layer 7 includes the naphthalene derivative, the stacked light emitting layers (particularly, three layers in the present embodiment) are balanced. While making it light-emit, durability (life) can be improved.
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. Since such a display device uses the light emitting element 1 as described above, a high-quality image can be displayed over a long period of time.
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, a plurality of light emitting elements 1R, 1G, and 1B and color filters 19R, 19G, and 10B provided corresponding to the sub-pixels 100R, 100G, and 100B, and each light emitting element 1R. And a plurality of driving transistors 24 for driving 1G and 1B, 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 planarization layer, 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 prevention film 33, an anode 3, a laminate (organic EL light emitting unit) 15, a cathode 12, and a cathode cover 34 are laminated in this order on a 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 12 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. An epoxy layer 35 made of an epoxy resin is formed on the light emitting elements 1R, 1G, and 1B so as to cover them.

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. The color filter 19G converts the white light W from the light emitting element 1G into green. The color filter 19B converts the white light W from the light emitting element 1B into blue. 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.
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, a high-quality image can be displayed over a long period of time.

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 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. Even when there are two or more light emitting layers, white light can be emitted by appropriately setting the emission spectrum of each light emitting layer.
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 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, the compound represented by Chemical Formula 1 was deposited on the ITO electrode by a vacuum deposition method to form a hole injection layer having an average thickness of 40 nm.
<3> Next, the compound represented by Chemical Formula 2 was vapor-deposited on the hole injection layer by a vacuum vapor deposition method to form a hole transport layer having an average thickness of 20 nm.
<4> Next, a first light-emitting material (red light-emitting material) and a first host material are vapor-deposited on the hole transport layer by a vacuum evaporation method, and the first light-emitting layer (red light-emitting layer) having an average thickness of 10 nm is deposited. Layer).
Here, the compound represented by Chemical Formula 3 was used as the first light-emitting material (guest material), and the compound represented by Chemical Formula 4 was used as the first host material. The content (dope concentration) of the first light emitting material (dopant) in the first light emitting layer was 1.5 wt%.

<5> Next, the constituent material of the intermediate layer (naphthalene derivative and amine compound) was vapor-deposited on the first light-emitting layer by vacuum vapor deposition (co-evaporation) to form an intermediate layer having an average thickness of 10 nm.
As the constituent material of the intermediate layer, the compound represented by the chemical formula 6 described above was used as the naphthalene derivative, and the compound represented by the chemical formula 2 described above was used as the amine compound. Further, the content of the naphthalene derivative in the intermediate layer was 80 wt%, and the content of the amine compound in the intermediate layer was 20 wt%.

<6> Next, a second light-emitting material (blue light-emitting material) and a second host material are deposited on the intermediate layer by a vacuum evaporation method, and a second light-emitting layer (blue light-emitting layer) having an average thickness of 25 nm is formed. Formed.
Here, the compound represented by the chemical formula 8 described above was used as the second light-emitting material, and the compound represented by the chemical formula 7 described above was used as the second host material. Further, the content (dope concentration) of the second light emitting material (dopant) in the second light emitting layer was 5.0 wt%.

  <7> Next, the third light emitting material (green light emitting material) and the constituent material of the third host material are vapor-deposited on the second light emitting layer by a vacuum evaporation method, and the third light emission having an average thickness of 25 nm is performed. A material (green light emitting layer) was formed. The compound represented by the chemical formula 9 described above was used as the third light-emitting material (guest material), and the compound represented by the chemical formula 7 described above was used as the third host material. Further, the content (dope concentration) of the third light emitting material (dopant) in the third light emitting layer was 8.0 wt%.

<8> Next, on the third light-emitting layer, tris (8-quinolinolato) aluminum (Alq ₃ ) was formed by a vacuum evaporation method to form an electron transport layer having an average thickness of 20 nm.
<9> Next, on the electron transport layer, lithium fluoride (LiF) was formed by a vacuum deposition method to form an electron injection layer having an average thickness of 0.5 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.
Through the above steps, a light emitting device as shown in FIG. 1 was manufactured.

( Reference example )
A light emitting device was manufactured in the same manner as in Example 1 except that the intermediate layer was composed of a naphthalene derivative and an anthracene derivative.
Here, the compound represented by the chemical formula 6 described above was used as the naphthalene derivative, and the compound represented by the chemical formula 7 described above was used as the anthracene derivative. The content of the naphthalene derivative in the intermediate layer was 70 wt%, and the content of the anthracene derivative in the intermediate layer was 30 wt%.

(Example 2 )
A light emitting device was produced in the same manner as in Example 1 except that the intermediate layer was composed of a naphthalene derivative, an amine compound and an anthracene derivative.
Here, the compound represented by Chemical Formula 6 described above was used as the naphthalene derivative, the compound represented by Chemical Formula 2 was used as the amine compound, and the compound represented by Chemical Formula 7 was used as the anthracene derivative. The content of the naphthalene derivative in the intermediate layer was 65 wt%, the content of the amine compound in the intermediate layer was 20 wt%, and the content of the anthracene derivative in the intermediate layer was 15 wt%.

(Comparative example)
A light emitting device was manufactured in the same manner as in Example 1 except that the intermediate layer was formed only from the compound (NPD) represented by Chemical Formula 2 described above.
Here, the thickness of the intermediate layer was 7 nm.

2. Evaluation 2-1. Evaluation of luminous efficiency
About the reference example, each Example, and the comparative example, 100 mA / cm < ² > constant current was sent through the light emitting element using DC power supply, and the brightness | luminance (initial brightness | luminance) was measured using the luminance meter. The results are shown in Table 1. Incidentally, reference examples, in each of the examples and the ratio Comparative Examples were measured for five light emitting elements respectively luminance. Table 1 also shows drive voltages for the reference example, each example, and the comparative example.

2-2. Evaluation of luminous lifetime
With respect to the reference example, each example, and the comparative example, a constant current of 100 mA / cm ² was continuously supplied to the light emitting element using a direct current power source, while the luminance was measured using a luminance meter, and the luminance was 50% of the initial luminance. % Time (LT50) was measured. The results are shown in Table 1. In Reference Examples, Examples and Comparative Examples, half-life values were measured for five light emitting elements.

2-3. Evaluation of chromaticity
For the reference example, each example, and each comparative example, a constant current of 100 mA / cm ² was passed through the light emitting element using a DC power source, and the chromaticity (x, y) of light was obtained using a chromaticity meter. Moreover, about a reference example, each Example, and a comparative example, the relationship between a wavelength and radiance is shown to FIGS.
As is clear from Table 1, the light-emitting elements of the reference example and each example are superior in durability while maintaining the same chromaticity balance and light-emitting efficiency as compared with the light-emitting element of the reference comparative example. I understand that.

It is a figure which shows typically the longitudinal cross-section of the light emitting element concerning 1st 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. It is a graph which shows the relationship between the wavelength of a light emitting element in Example 1 of this invention, and radiance. It is a graph which shows the relationship between the wavelength of a light emitting element and the radiance in the reference example of this invention. It is a graph which shows the relationship between the wavelength of a light emitting element in Example 2 of this invention, and radiance. It is a graph which shows the relationship between the wavelength of the light emitting element in a comparative example, and radiance.

Explanation of symbols

  1, 1G, 1R, 1B: Light-emitting element 2 ... Substrate 3 ... Anode 4 ... Hole injection layer 5 ... Hole transport layer 6 ... First light-emitting layer 7 ... Intermediate layer 8 ... First Second light emitting layer 9... Third light emitting layer 10... Electron transport layer 11... Electron injection layer 12 ... Cathode 13 ... Sealing member 15 ... Laminate 19B, 19G, 19R ... Color filter 100 ... ... Display 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 wall 32 …… Reflection film 33 …… Corrosion prevention film 34 …… 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 …… Speaker 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 (16)

A cathode,
The anode,
A first light-emitting layer provided between the cathode and the anode and configured to include a first light-emitting material that emits light in a first color;
A second light-emitting layer that is provided between the first light-emitting layer and the cathode and includes a second light-emitting material that emits light in a second color different from the first color;
An intermediate provided between the first light emitting layer and the second light emitting layer so as to be in contact therewith and having a function of restricting the movement of electrons from the second light emitting layer to the first light emitting layer. And having a layer
The intermediate layer includes a naphthalene derivative represented by a general formula C _x H _y (where x and y are natural numbers, respectively), a hole transporting material having higher hole transportability than the naphthalene derivative, A light-emitting element comprising:   The light emitting device according to claim 1, wherein the naphthalene derivative has a molecular weight of 400 to 1,000.   The light-emitting element according to claim 2, wherein the naphthalene derivative has two or more naphthyl groups introduced therein.   The light emitting device according to any one of claims 1 to 3, wherein an absorption peak wavelength of the naphthalene derivative is less than 450 nm.   The light-emitting element according to claim 4, wherein the naphthalene derivative has an electron affinity of 2 to 3 eV. The light emitting device according to claim 4, wherein an ionization potential of the hole transporting material is 5 to 6.2 eV. 6. The light emitting device according to claim 1 , wherein an ionization potential of a material that is hardly oxidized among materials constituting the intermediate layer is 5 to 6.2 eV .   The light emitting device according to claim 7, wherein the hole transporting material contains an amine compound.   The light emitting device according to claim 1, wherein the intermediate layer includes an electron transporting material having an electron transporting property higher than that of the naphthalene derivative in addition to the naphthalene derivative.   The light-emitting element according to claim 9, wherein the electron transporting material contains an anthracene derivative or a dianthracene derivative.   The second light emitting layer includes a second host material that uses the second light emitting material as a guest material in addition to the second light emitting material, and the second host material includes: The light-emitting device according to claim 1, comprising an anthracene derivative.   The first light-emitting layer includes a host material that uses the first light-emitting material as a guest material in addition to the first light-emitting material, and the first light-emitting material includes a tetracene derivative or The light emitting device according to claim 1, comprising a perylene derivative.   A third light emitting material that is provided between the second light emitting layer and the cathode and includes a third light emitting material that emits light in a third color different from the first color and the second color; The light emitting device according to claim 1, comprising the light emitting layer.   The first light emitting material emits red light, and the second light emitting material and the third light emitting material emit light in green and the other emits blue light. The light emitting device according to claim 13.   A display device comprising the light-emitting element according to claim 1.   An electronic apparatus comprising the display device according to claim 15.

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