JP2012204794A - Organic electroluminescent element and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element whose life characteristics including deterioration in luminance and increase in driving voltage can be improved while enhancing luminous efficiency, and to provide a display device using the same.SOLUTION: An organic layer 14 comprising, in the following order, a hole supply layer 14A (a hole injection layer 14a and a hole transport layer 14b), a light-emitting layer 14B, and an electron transport layer 14C containing an arylpyridine derivative is laminated on an anode 13, and a cathode 15 is formed on the organic layer 14 to obtain the organic electroluminescent element. The electron transport layer 14C is formed so as to have a thickness greater than that of the hole supply layer 14A, thereby adjusting the amount of holes and electrons to be injected into the light-emitting layer 14B.

Description

  The present invention relates to an organic electroluminescent element that emits light using an organic electroluminescence (EL) phenomenon and a display device.

  An organic electroluminescent element (organic EL element) using an organic material EL has been attracting attention as a light emitting element having an organic layer including a light emitting layer between an anode and a cathode and capable of emitting light with high luminance by low voltage direct current drive. ing.

  In the organic electroluminescence device, various studies have been made on the layer configuration of an organic layer including a light emitting layer and the material configuration of each layer for the purpose of improving luminous efficiency and lifetime characteristics. For example, as disclosed in Patent Document 1, an organic electroluminescent device using a nitrogen-containing heterocyclic compound having a high electron mobility as a constituent material of an electron injection layer and an electron transport layer between a light emitting layer and a cathode has been proposed. .

JP 2007-291092 A

  However, in the organic electroluminescent element described in Patent Document 1, the electron mobility of the nitrogen-containing heterocyclic compound is high, so that the carrier balance in the light emitting layer when an electric field is applied collapses, and the supply of electrons is excessive. There was a problem that it was easy to become. For this reason, the deterioration of the light emitting layer is promoted, the light emission efficiency of the organic electroluminescent element is lowered, and the life is shortened.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an organic electroluminescent element capable of improving lifetime characteristics including suppressing luminance deterioration and increasing driving voltage while improving luminous efficiency, and the present invention. It is to provide a display device using the above.

  The organic electroluminescent device according to the present invention includes an anode, a hole supply layer formed on the anode, a light emitting layer, and an arylpyridine derivative represented by the formula (1), and is thicker than the hole supply layer. An organic layer having an electron supply layer in this order and a cathode formed on the organic layer are provided.

（Ａｒ１は核炭素数６〜５０個の芳香族炭化水素基あるいはその誘導体である。Ｘは少なくともピリジニル基を含有する芳香族複素環基あるいはその誘導体である。ｍは１〜５の整数であり、ｎは１〜６の整数である。但し、ｍが２以上の場合にはＡｒ１はそれぞれ同一の基あるいは異なる基でもよい。ｎが２以上の場合にはＸはそれぞれ同一の基あるいは異なる基でもよい。）

(Ar1 is an aromatic hydrocarbon group having 6 to 50 nuclear carbon atoms or a derivative thereof. X is an aromatic heterocyclic group or a derivative thereof containing at least a pyridinyl group. M is an integer of 1 to 5. , N is an integer of 1 to 6. However, when m is 2 or more, Ar1 may be the same group or different groups, and when n is 2 or more, X is the same group or different groups. May be.)

  A display device according to the present invention includes a plurality of the organic electroluminescent elements provided on a substrate.

  In the organic electroluminescent element of the present invention and the display device including the same, the organic supply layer is thicker than the hole supply layer among the organic layers including the hole supply layer, the light emitting layer, and the electron supply layer. It is possible to adjust the amount of electrons supplied from the electron supply layer to the light emitting layer.

  According to the organic electroluminescent element of the present invention and the display device using the same, the thickness of the electron supply layer is larger than that of the hole supply layer among the organic layers including the hole supply layer, the light emitting layer, and the electron supply layer. Thus, the amount of electrons supplied from the electron supply layer to the light emitting layer is adjusted, and electrons and holes can be supplied to the light emitting layer without excess or deficiency. Thereby, deterioration of the light emitting layer due to excessive supply of electrons can be suppressed. That is, it is possible to improve the life characteristics while improving the light emission efficiency.

It is sectional drawing of the organic electroluminescent element which concerns on the 1st Embodiment of this invention. It is a figure showing the structure of the display apparatus provided with the organic electroluminescent element shown in FIG. FIG. 3 is a diagram illustrating an example of a pixel drive circuit illustrated in FIG. 2. It is sectional drawing showing the structure of the display area shown in FIG. It is sectional drawing of the organic electroluminescent element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the organic electroluminescent element which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the organic electroluminescent element which concerns on the 4th Embodiment of this invention. It is a top view showing schematic structure of the module containing the display apparatus of the said embodiment. It is a perspective view showing the external appearance of the application example 1 of the display apparatus of the said embodiment. (A) is a perspective view showing the external appearance seen from the front side of the application example 2, (B) is a perspective view showing the external appearance seen from the back side. 12 is a perspective view illustrating an appearance of application example 3. FIG. 14 is a perspective view illustrating an appearance of application example 4. FIG. (A) is a front view of the application example 5 in an open state, (B) is a side view thereof, (C) is a front view in a closed state, (D) is a left side view, and (E) is a right side view, (F) is a top view and (G) is a bottom view. It is a characteristic view showing the relationship between the voltage in an Example and the film thickness of an electron supply layer. It is a characteristic view showing the relationship between the brightness | luminance and the film thickness of an electron supply layer in an Example.

Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings.
1. First Embodiment (Organic electroluminescence device in which an organic layer composed of a hole supply layer, a light emitting layer and an electron supply layer is sandwiched between an anode and a cathode)
1-1 (organic electroluminescence device)
1-2 (display device)
2. Second Embodiment (Organic electroluminescence device having a two-layer structure electron supply layer)
3. Third Embodiment (Organic electroluminescence device having an electron supply layer having a three-layer structure)
4). Fourth Embodiment (Organic electroluminescence device having an organic layer of tandem structure)

(First embodiment)
(Organic electroluminescence device)
FIG. 1 shows a cross-sectional configuration of an organic electroluminescent element 11 according to a first embodiment of the present invention. The organic electroluminescent element 11 has a structure in which an anode 13, an organic layer 14, and a cathode 15 are laminated on a substrate 12 in this order. Among these layers, the organic layer 14 is formed by laminating, for example, a hole supply layer 14A (a hole injection layer 14a and a hole transport layer 14b), a light emitting layer 14B, and an electron supply layer 14C in this order from the anode 13 side.

  The organic electroluminescence device 11 emits light emitted when holes injected from the anode 13 and electrons injected from the cathode 15 recombine in the light emitting layer 14B on the side opposite to the substrate 12 (cathode 15). This is an organic electroluminescence device of a top emission method (top emission method) that extracts light from the side).

  The substrate 12 is a support on which the organic electroluminescent elements 11 are arranged and formed on one main surface side. The material constituting the substrate 12 may be a known material, for example, quartz, glass, metal foil, or a resin film or sheet. Of these, quartz and glass are preferable. In the case of resin, methacrylic resins represented by polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate ( Polyesters such as PBN) or polycarbonate resins. However, in order to suppress water permeability and gas permeability, a laminated structure or surface treatment is required.

The anode 13 preferably has a high work function from the vacuum level of the electrode material in order to inject holes efficiently. Specifically, for example, chromium (Cr), gold (Au), an alloy of tin oxide (SnO ₂ ) and antimony (Sb), an alloy of zinc oxide (ZnO) and aluminum (Al), a silver (Ag) alloy Alternatively, oxides of these metals and alloys can be used alone or in a mixed state.

  Further, the anode 13 may have a laminated structure of a first layer having excellent light reflectivity and a second layer having a light transmittance and a large work function provided thereon. Here, it is preferable to use an alloy mainly containing Al as the first layer. As the subcomponent, an element having a work function relatively smaller than that of Al as the main component is used. As such a minor component, it is preferable to use a lanthanoid series element. The work function of the lanthanoid series elements is not large, but inclusion of these elements improves the stability of the anode and improves the hole injection property of the anode. In addition to lanthanoid series elements, elements such as silicon (Si) and copper (Cu) may be used as subcomponents.

  The content of subcomponents in the Al alloy layer constituting the first layer is, for example, about 10 wt% or less in total in the case of neodymium (Nd), nickel (Ni), titanium (Ti) or the like that stabilizes Al. It is preferable. Thereby, the Al alloy layer can be stably maintained in the manufacturing process of the organic electroluminescent element while maintaining the reflectance in the Al alloy layer as the first layer. Further, processing accuracy and chemical stability can be obtained. Furthermore, the conductivity of the anode 13 and the adhesion to the substrate 12 are also improved. Since the metal such as Nd has a small work function, an amine-based material generally used for the hole supply layer 14A described later has a large hole injection barrier. In that case, a layer in which an acceptor material such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4-TCNQ) is mixed with an amine material, By forming a p-doped layer such as oxythiophene-polystyrene sulfonic acid (PEDOT-PSS) at the interface of the anode 13, the hole injection barrier can be reduced, and an increase in driving voltage can be suppressed. In addition, by using an azatriphenylene derivative described later, it is possible to stabilize the element while suppressing an increase in driving voltage.

  For the second layer, an oxide of Al alloy, an oxide of molybdenum (Mo), an oxide of zirconium (Zr), an oxide of Cr, and an oxide of tantalum (Ta) can be used. For example, in the case where the second layer is an Al alloy oxide layer (including a natural oxide film) containing a lanthanoid series element as a subcomponent, the lanthanoid series element oxide contains this because it has a high light transmittance. The light transmittance of the second layer is improved. Thereby, the reflectance at the surface of the first layer is kept high. Moreover, the electron injection characteristic of the anode 13 is improved by using a transparent conductive layer such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) for the second layer. In addition, since ITO and IZO have a large work function, it is possible to improve the carrier injection efficiency and improve the adhesion between the anode 13 and the substrate 12 by using the ITO and IZO on the side in contact with the substrate 12, that is, the first layer. it can.

  When the driving method of the display device configured using the organic electroluminescent element 11 is an active matrix method, the anode 13 is patterned for each pixel and is a driving thin film transistor (illustrated) provided on the substrate 12. No connection). In this case, a partition 16 (see FIG. 4) is provided on the anode 13, and the surface of the anode 13 of each pixel is exposed from the opening of the partition 16.

  The hole supply layer 14A (the hole injection layer 14a and the hole transport layer 14b) is a buffer layer for increasing the efficiency of hole injection into the light emitting layer 14B and preventing leakage. The film thickness of the hole supply layer 14A depends on the overall structure of the device, particularly the relationship with the electron supply layer 14C described later, but is preferably 1 nm to 100 nm, for example, and more preferably 20 nm to 70 nm.

  The constituent material of the hole supply layer 14A may be appropriately selected in relation to the electrode and the material of the adjacent layer. For example, benzine, styrylamine, triphenylamine, porphyrin, triphenylene, azatriphenylene, tetracyanoquinodimethane. , Triazole, imidazole, oxadiazole, polyarylalkane, phenylenediamine, arylamine, oxazole, anthracene, fluorenone, hydrazone, stilbene or their derivatives, or polysilane compounds, vinylcarbazole compounds, thiophene compounds or aniline compounds Heterocyclic conjugated monomers, oligomers or polymers such as compounds can be used.

  Further, specific materials for the hole supply layer 14A include α-naphthylphenylphenylenediamine, porphyrin, metal tetraphenylporphyrin, metal naphthalocyanine, hexacyanoazatriphenylene, 7,7,8,8-tetracyanoquino. Dimethane (TCNQ), F4-TCNQ, tetracyano 4,4,4-tris (3-methylphenylphenylamino) triphenylamine, N, N, N ′, N′-tetrakis (p-tolyl) p-phenylenediamine , N, N, N ′, N′-tetraphenyl-4,4′-diaminobiphenyl, N-phenylcarbazole, 4-di-p-tolylaminostilbene, poly (paraphenylene vinylene), poly (thiophene vinylene), And poly (2,2′-thienylpyrrole).

  However, by using the compounds represented by the following formulas (2) to (5), holes supplied from the hole supply layer 14A to the light emitting layer 14B with respect to the electron supply from the electron supply layer 14C described later to the light emitting layer 14B. Supply is optimized.

（Ｒ１〜Ｒ６は各々独立して、水素原子、ハロゲン原子、ヒドロキシル基、アミノ基、アリールアミノ基、炭素数２０以下のカルボニル基、炭素数２０以下のカルボニルエステル基、炭素数２０以下のアルキル基、炭素数２０以下のアルケニル基、炭素数２０以下のアルコキシル基、炭素数３０以下のアリール基、炭素数３０以下の複素環基、ニトリル基、シアノ基、ニトロ基、またはシリル基から選ばれる置換基あるいはそれらの誘導体である。隣接するＲ１〜Ｒ６は互いに結合して環状構造を形成してもよい。Ｘ１〜Ｘ６は各々独立して、炭素原子もしくは窒素原子である。）

(R1 to R6 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an arylamino group, a carbonyl group having 20 or less carbon atoms, a carbonyl ester group having 20 or less carbon atoms, or an alkyl group having 20 or less carbon atoms. A substituent selected from an alkenyl group having 20 or less carbon atoms, an alkoxyl group having 20 or less carbon atoms, an aryl group having 30 or less carbon atoms, a heterocyclic group having 30 or less carbon atoms, a nitrile group, a cyano group, a nitro group, or a silyl group And adjacent R1 to R6 may be bonded to each other to form a cyclic structure. X1 to X6 are each independently a carbon atom or a nitrogen atom.)

  Note that the azatriphenylene derivative represented by the above formula (2) is preferably used for the hole injection layer 14a because X is replaced by a nitrogen atom to increase the nitrogen content in the compound.

（Ａ０〜Ａ２は、各々独立して、水素原子、ハロゲン原子、ヒドロキシル基、アルデヒド基、カルボニル基、カルボニルエステル基、アルキル基、アルケニル基、環状アルキル基、アルコキシ基、アリール基、アミノ基、複素環基、シアノ基、ニトリル基、ニトロ基、あるいはシリル基によって置換された炭素数６〜３０の芳香族炭化水素基である。）

(A0 to A2 are each independently a hydrogen atom, halogen atom, hydroxyl group, aldehyde group, carbonyl group, carbonyl ester group, alkyl group, alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, complex, (It is an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted by a cyclic group, a cyano group, a nitrile group, a nitro group, or a silyl group.)

（Ａ３〜Ａ６は、各々独立して、水素原子、ハロゲン原子、ヒドロキシル基、アルデヒド基、カルボニル基、カルボニルエステル基、アルキル基、アルケニル基、環状アルキル基、アルコキシ基、アリール基、アミノ基、複素環基、シアノ基、ニトリル基、ニトロ基、あるいはシリル基によって置換された炭素数６〜２０の芳香族炭化水素基である。Ａ３およびＡ４、Ａ５とＡ６は各々連結基を介して結合していてもよい。ＹはＮとの結合部位以外の環炭素に、各々独立して水素原子、ハロゲン原子、ヒドロキシル基、アルデヒド基、カルボニル基、カルボニルエステル基、アルキル基、アルケニル基、環状アルキル基、アルコキシ基、アリール基、アミノ基、複素環基、シアノ基、ニトリル基、ニトロ基、またはシリル基によって置換されたベンゼン、ナフタレン、アントラセン、フェナントレン、ナフタセン、フルオランテンまたはペリレンからなる２価の芳香族炭化水素基である。ｍは１以上の整数である。）

(A3 to A6 are each independently a hydrogen atom, halogen atom, hydroxyl group, aldehyde group, carbonyl group, carbonyl ester group, alkyl group, alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, An aromatic hydrocarbon group having 6 to 20 carbon atoms substituted by a cyclic group, a cyano group, a nitrile group, a nitro group, or a silyl group, A3 and A4, A5 and A6 are bonded via a linking group. Y may be independently a hydrogen atom, a halogen atom, a hydroxyl group, an aldehyde group, a carbonyl group, a carbonyl ester group, an alkyl group, an alkenyl group, a cyclic alkyl group, or a ring carbon other than the bonding site with N. Substituted by alkoxy group, aryl group, amino group, heterocyclic group, cyano group, nitrile group, nitro group, or silyl group Benzene, naphthalene, anthracene, phenanthrene, naphthacene, a divalent aromatic hydrocarbon radical consisting of fluoranthene or perylene .m is an integer of 1 or more.)

（Ａ７〜Ａ１２は各々独立して水素原子、ハロゲン原子、ヒドロキシル基、アルデヒド基、カルボニル基、カルボニルエステル基、アルキル基、アルケニル基、環状アルキル基、アルコキシ基、アリール基、アミノ基、複素環基、シアノ基、ニトリル基、ニトロ基、あるいはシリル基によって置換された炭素数６〜２０の芳香族炭化水素基である。隣接するＡ７およびＡ８、Ａ９およびＡ１０、Ａ１１およびＡ１２は、各々連結基を介して結合していてもよい。Ｚ１〜Ｚ３はＮとの結合部位以外の環炭素に、各々独立して水素原子、ハロゲン原子、ヒドロキシル基、アルデヒド基、カルボニル基、カルボニルエステル基、アルキル基、アルケニル基、環状アルキル基、アルコキシ基、アリール基、アミノ基、複素環基、シアノ基、ニトリル基、ニトロ基、またはシリル基によって置換されたベンゼン、ナフタレン、アントラセン、フェナントレン、ナフタセン、フルオランテンまたはペリレンからなる２価の芳香族炭化水素基である。ｐ，ｑおよびｒは１以上の整数である。）

(A7 to A12 are each independently hydrogen atom, halogen atom, hydroxyl group, aldehyde group, carbonyl group, carbonyl ester group, alkyl group, alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, heterocyclic group. , An aromatic hydrocarbon group having 6 to 20 carbon atoms substituted by a cyano group, a nitrile group, a nitro group, or a silyl group, and adjacent A7 and A8, A9 and A10, A11 and A12 are each a linking group. Z1 to Z3 each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an aldehyde group, a carbonyl group, a carbonyl ester group, an alkyl group, or a ring carbon other than the bonding site with N. Alkenyl group, cyclic alkyl group, alkoxy group, aryl group, amino group, heterocyclic group, cyano group, nitrile group Benzene substituted by a nitro group or a silyl group, naphthalene, anthracene, phenanthrene, naphthacene, a divalent aromatic hydrocarbon radical consisting of fluoranthene or perylene .p, q and r is an integer of 1 or more.)

  Specific examples of the azatriphenylene derivative represented by the formula (2) include compounds such as the following formula (2-1).

  Specific examples of the amine derivative represented by the formula (3) include compounds such as the following formulas (3-1) to (3-9).

  Specific examples of the diamine derivative represented by the formula (4) include compounds such as the following formulas (4-1) to (4-84).

  Specific examples of the triarylamine multimer represented by the formula (5) include compounds such as the following formulas (5-1) to (5-15).

  These compounds may be used in either the hole injection layer 14a or the hole transport layer 14b, but it is preferable to use a compound having a high nitrogen content in the hole injection layer 14a. This is because the hole injection barrier from the anode 13 can be reduced. In addition, since the electron supply layer 14C in the present embodiment has enhanced electron supply capability to the light emitting layer 14B, azatriphenylene having a high hole injection property is provided at the anode interface in order to obtain a better carrier balance. It is preferable to use a derivative.

  The light emitting layer 14B is a region where holes injected from the anode 13 side and electrons injected from the cathode 15 side are recombined when an electric field is applied to the anode 13 and the cathode 15. Although the thickness of the light emitting layer 14B depends on the entire configuration of the element, it is preferably, for example, 1 nm to 100 nm, and more preferably 5 nm to 50 nm.

  Although the light emitting layer 14B may be a single layer, for example, a plurality of light emitting layers (for example, three layers 14r, 14g, and 14b (not shown)) having different emission colors may be stacked. The light emitting layer 14r is a red light emitting layer, the light emitting layer 14g is a green light emitting layer, and the light emitting layer 14b is a blue light emitting layer. The stacking order of the light emitting layers 14r, 14g, and 14b is appropriately determined from the adjustment of the optical path length according to the carrier transport property of each of the light emitting layers 14r, 14g, and 14b and the emission wavelength of light extraction. A light emitting layer separation layer (not shown) may be provided between the red light emitting layer 14r, the green light emitting layer 14g, and the blue light emitting layer 14b. The light emitting layer separation layer is made of, for example, an amine derivative, and the thickness is preferably 0.1 nm to 20 nm, and more preferably 1 to 10 nm. The film thicknesses of the light emitting layers 14r, 14g, and 14b of the respective colors are preferably set as follows. For example, the red light emitting layer 14r is 5 nm to 15 nm, the green light emitting layer 14g is 5 nm to 15 nm, and the blue light emitting layer 14b is 5 nm to 15 nm, but is not limited thereto.

  The material constituting the light emitting layer 14B is a charge injection function (holes can be injected from the anode 13 or the hole supply layer 14A when an electric field is applied, while electrons are injected from the cathode 15 or the electron supply layer 14C. ), Transport function (function to move injected holes and electrons by the force of electric field), and light emission function (function to provide a field for recombination of electrons and holes and connect them to light emission) It is preferable. As such a material, a fluorescent light emitting material and a phosphorescent light emitting material can be used. Specific examples of the fluorescent light-emitting material include a styryl derivative, an anthracene derivative, a naphthacene derivative, and an aromatic amine as a host material. In particular, the styryl derivative is preferably a distil derivative, a tristil derivative, a tetrastil derivative, or a styrylamine derivative. Further, an excellent carrier balance can be maintained by using an anthracene derivative, particularly an asymmetric anthracene compound. Furthermore, the aromatic amine is preferably a compound having 2 to 4 nitrogen atoms substituted with an aromatic ring group. Specific examples of the phosphorescent light emitting material include a carbazole derivative or a quinoline complex derivative as a host material.

  When a plurality of light emitting layers are stacked, it is preferable to use a hole transporting material as a host material for the light emitting layer on the anode side. Thereby, the hole injection from the anode 13 is stabilized.

  Examples of luminescent dopants include, for example, styrylbenzene dyes, oxazole dyes, perylene dyes, coumarin dyes, laser dyes such as acridine dyes, and polyaromatics such as anthracene derivatives, naphthacene derivatives, pentacene derivatives, and chrysene derivatives. Select from fluorescent materials such as hydrocarbon materials, pyromethene skeleton compounds or metal complexes, quinacridone derivatives, cyanomethylenepyran derivatives (DCM, DCJTB), benzothiazole compounds, benzimidazole compounds, metal chelated oxinoid compounds, etc. Can be used. The doping concentration of each of these fluorescent materials is preferably 0.5% or more and 15% or less in terms of film thickness ratio. A known phosphorescent dopant having a desired emission color can also be used. Specific examples include amines having a stilbene structure, aromatic amines, perylene derivatives, coumarin derivatives, borane derivatives, pyran derivatives, iridium complexes, platinum complexes, and rhenium complexes. Of these, phosphorescent dopant materials of iridium complexes, platinum complexes and rhenium complexes are preferably used.

  The light emitting layer 14B may be formed by a coating method such as an ink jet, for example, in addition to a film formation by a vacuum evaporation method. In this case, the high molecular material and the low molecular material are, for example, toluene, xylene, anisole, cyclohexanone, mesitylene (1,3,5-trimethylbenzene), bsidecumene (1,2,4-trimethylbenzene), dihydrobenzofuran, 1, Organics such as 2,3,4-tetramethylbenzene, tetralin, cyclohexylbenzene, 1-methylnaphthalene, p-anisyl alcohol, dimethylnaphthalene, 3-methylbiphenyl, 4-methylbiphenyl, 3-isopropylbiphenyl, monoisopropylnaphthalene It dissolves in a solvent using at least one kind and forms using this mixed solution.

The electron supply layer 14C is for transporting electrons injected from the cathode 15 to the light emitting layer 14B. The thickness of the electron supply layer 14C depends on the overall structure of the device, but is formed thicker than the hole supply layer 14A. This maintains a balance between the amount of holes supplied from the hole supply layer to the light emitting layer 14B and the amount of electrons supplied from the electron supply layer 14C to the light emitting layer 14B. The thickness of the electron supply layer 14C is preferably designed to satisfy the following relationship. When the thickness of the electron supply layer 14C is d1, and the thickness of the entire organic layer 14 is d2, the light emitting layer is designed by satisfying the relationship of 0.90> d ₁ / d ₂ > 0.30. It becomes easy to balance supply of holes and electrons to 14B. From the above, the electron supply layer 14C is preferably, for example, 70 nm to 300 nm, and more preferably 120 nm to 250 nm.

  As a material for the electron supply layer 14C, an organic material having an excellent electron transport ability is preferably used, and specifically, an arylpyridine derivative represented by the following formula (6) is preferably used. This stabilizes the supply of electrons to the light emitting layer 14B, and compensates for stable driving while being highly efficient.

（Ａｒ１は核炭素数６〜５０個の芳香族炭化水素基あるいはその誘導体である。Ｘは少なくともピリジニル基を含有する芳香族複素環基あるいはその誘導体である。ｍは１〜５の整数であり、ｎは１〜６の整数である。但し、ｍが２以上の場合にはＡｒ１はそれぞれ同一の基あるいは異なる基でもよい。ｎが２以上の場合にはＸはそれぞれ同一の基あるいは異なる基でもよい。）

(Ar1 is an aromatic hydrocarbon group having 6 to 50 nuclear carbon atoms or a derivative thereof. X is an aromatic heterocyclic group or a derivative thereof containing at least a pyridinyl group. M is an integer of 1 to 5. , N is an integer of 1 to 6. However, when m is 2 or more, Ar1 may be the same group or different groups, and when n is 2 or more, X is the same group or different groups. May be.)

  Specific examples of the arylpyridine derivative represented by the formula (6) include compounds such as the following formulas (6-1) to (6-58).

  By using an arylpyridine derivative having such a high electron supply capability, even if the electron supply layer 14C is formed to be thicker than the total film thickness of the hole supply layer 14A, a high electron with a low driving voltage can be obtained. Supply efficiency can be maintained. Further, by forming the electron supply layer 14C in a thick film, a short circuit between the anode 13 and the cathode 15 is prevented.

  Note that the electron supply layer 14C may contain a compound other than the arylpyridine derivative represented by the formula (6). Examples of compounds other than arylpyridine derivatives include alkali metals, alkaline earth metals, rare earth metals and their oxides, composite oxides, fluorides, carbonates, and the like.

  The cathode 15 is made of, for example, a material having a thickness of 2 nm to 15 nm, good light transmittance, and a small work function. The cathode 15 may be a single layer, but here has a structure in which, for example, the first layer 15A and the second layer 15B are stacked in this order from the anode 13 side.

The first layer 15A is preferably formed of a material having a small work function and good light transmittance. Specifically, for example, _{Li 2 O, Cs 2 Co 3} , Cs 2 SO 4, MgF, alkali metal oxides such as LiF and CaF _2, alkali metal fluorides, alkaline earth metal oxides, alkaline earth fluorides Is mentioned. The second layer 15B is made of a material having light transmissivity such as a thin MgAg electrode and a Ca electrode and having good conductivity.

  The first layer 15A and the second layer 15B are formed by a technique such as a vacuum deposition method, a sputtering method, or a plasma CVD method. When the driving method of the display device configured using the organic electroluminescent element is an active matrix method, the cathode 15 is insulated from the anode 13 by the partition wall 16 and the organic layer 14 that cover the periphery of the anode 13. In this state, a solid film may be formed on the substrate 12 and used as a common electrode for each pixel.

  The cathode 15 may be a mixed layer containing an organic light emitting material such as an aluminum quinoline complex, a styrylamine derivative, or a phthalocyanine derivative. In this case, a layer having optical transparency such as MgAg may be additionally provided as a third layer (not shown). Needless to say, the cathode 15 is not limited to the laminated structure as described above, and an optimum combination and laminated structure may be taken according to the structure of the device to be manufactured. For example, the cathode 15 of the present embodiment includes an inorganic layer (first layer 15A) that promotes functional separation of each electrode layer, that is, injection of electrons into the organic layer 14, and an inorganic layer (second layer 15B) that controls the electrode. Is a laminated structure in which However, the inorganic layer that promotes electron injection into the organic layer 14 may also serve as the inorganic layer that controls the electrode, and these layers may be configured as a single layer structure. Moreover, it is good also as a laminated structure which formed transparent electrodes, such as ITO, on this single layer structure.

  Further, when the organic electroluminescent element 11 has a cavity structure, it is preferable to use a transflective material for the cathode 15. As a result, emitted light that has been subjected to multiple interference between the light reflecting surface on the anode 13 side and the light reflecting surface on the cathode 15 side is extracted from the cathode 15 side. In this case, the optical distance between the light reflecting surface on the anode 13 side and the light reflecting surface on the cathode 15 side is defined by the wavelength of light to be extracted, and the film thickness of each layer is set so as to satisfy this optical distance. Suppose that it is done. In such a top emission type organic electroluminescence device, it is possible to improve the light extraction efficiency to the outside and control the emission spectrum by positively using this cavity structure.

(Display device)
FIG. 2 shows a configuration of the display device 10 including the organic electroluminescent element 11 (red organic electroluminescent element 11R, green organic electroluminescent element 11G, blue organic electroluminescent element 11B) of the present embodiment. The display device 10 is used as an organic EL television device or the like. For example, a plurality of organic electroluminescent elements 11 are arranged in a matrix as a display region 110 on a substrate 12. Around the display area 110, a signal line driving circuit 120 and a scanning line driving circuit 130, which are drivers for displaying images, are provided. In addition, the combination of the adjacent organic electroluminescent elements 11R, 11G, and 11B constitutes one pixel (pixel).

  A pixel drive circuit 140 is provided in the display area 110. FIG. 3 illustrates an example of the pixel driving circuit 140. The pixel drive circuit 140 is an active drive circuit formed below the anode 13. That is, the pixel drive circuit 140 includes a drive transistor Tr1 and a write transistor Tr2, a capacitor (holding capacitor) Cs between the transistors Tr1 and Tr2, a first power supply line (Vcc), and a second power supply line (GND). ), The organic electroluminescent element 11 (11R, 11G, 11B) connected in series to the driving transistor Tr1. The drive transistor Tr1 and the write transistor Tr2 are configured by a general thin film transistor (TFT), and the configuration may be, for example, an inverted staggered structure (so-called bottom gate type) or a staggered structure (top gate type). There is no particular limitation.

  In the pixel driving circuit 140, a plurality of signal lines 120A are arranged in the column direction, and a plurality of scanning lines 130A are arranged in the row direction. The intersection of each signal line 120A and each scanning line 130A corresponds to one of the organic electroluminescent elements 11 (subpixel). Each signal line 120A is connected to the signal line drive circuit 120, and an image signal is supplied from the signal line drive circuit 120 to the source electrode of the write transistor Tr2 via the signal line 120A. Each scanning line 130A is connected to the scanning line driving circuit 130, and a scanning signal is sequentially supplied from the scanning line driving circuit 130 to the gate electrode of the writing transistor Tr2 via the scanning line 130A.

FIG. 4 illustrates a part of a cross-sectional configuration of the display region 110 illustrated in FIG. Each of the organic electroluminescent elements 11 (11R, 11G, and 11B) has a driving transistor Tr1 and a planarization insulating film (not shown) of the pixel driving circuit 140 between the substrate 12 and the substrate 12 as described above. The anode 13, the partition 16, the organic layer 14 including the light emitting layer 14 </ b> B, and the cathode 15 are stacked in this order. Furthermore, the organic electroluminescent element 11 is covered with a protective layer 20, and further, a sealing layer 20 made of glass or the like is provided on the protective layer 20 with an adhesive layer (not shown) such as a thermosetting resin or an ultraviolet curable resin interposed therebetween. The substrate 30 is sealed by being bonded over the entire surface. The protective layer 20 includes a silicon nitride (typically Si ₃ N ₄ ) film, a silicon oxide (typically SiO ₂ ) film, a silicon nitride oxide (SiNxOy: composition ratio X> Y) film, and an oxynitridation A silicon (SiOxNy: composition ratio X> Y) film, a thin film mainly composed of carbon such as DLC (Diamond like Carbon), a CN (Carbon Nanotube) film, or the like is used. These films preferably have a single layer structure or a stacked structure. In particular, the protective layer 20 made of nitride has a dense film quality and has an extremely high blocking effect against moisture, oxygen, and other impurities that adversely affect the organic electroluminescent element 11.

The protective layer 20 has a thickness of 2 to 3 μm, for example, and may be made of either an insulating material or a conductive material. As the insulating material, an inorganic amorphous insulating material such as amorphous silicon (α-Si), amorphous silicon carbide (α-SiC), amorphous silicon nitride (α-Si _1-x N _x ), amorphous carbon (α -C) is preferred. Such an inorganic amorphous insulating material does not constitute grains, and thus has low water permeability and becomes a good protective film.

  The sealing substrate 30 is located on the cathode 15 side of the organic electroluminescent element 11 and seals the organic electroluminescent element 11 together with an adhesive layer (not shown). The sealing substrate 30 is made of a material such as glass that is transparent to the light generated by the organic electroluminescent element 11. The sealing substrate 30 is provided with, for example, a color filter and a light-shielding film (not shown) as a black matrix, and takes out the light generated in the organic electroluminescent element 11 and each organic electroluminescent element. The external light reflected in the wiring between 11 is absorbed and the contrast is improved.

  The color filter includes a red filter, a green filter, and a blue filter (all not shown), which are arranged in order. Each of the red filter, the green filter, and the blue filter is, for example, rectangular and has no gap. These red filter, green filter and blue filter are each composed of a resin mixed with a pigment, and by selecting the pigment, the light transmittance in the target red, green or blue wavelength region is high, The light transmittance in the wavelength range is adjusted to be low. A corresponding color filter is provided on each of the organic electroluminescent elements 11R, 11G, and 11B.

The light-shielding film is formed of, for example, a black resin film having an optical density of 1 or more mixed with a black colorant, or a thin film filter using thin film interference. Of these, a black resin film is preferable because it can be formed inexpensively and easily. The thin film filter is formed by, for example, laminating one or more thin films made of metal, metal nitride, or metal oxide, and attenuating light by utilizing interference of the thin film. Specific examples of the thin film filter include those in which Cr and chromium oxide (III) (Cr ₂ O ₃ ) are alternately laminated.

  Here, each layer from the anode 13 to the cathode 15 constituting the organic electroluminescence elements 11R, 11G, and 11B is formed by vacuum deposition, ion beam (EB), molecular beam epitaxy (MBE), sputtering, OVPD. It can be formed by a dry process such as (Organic Vapor Phase Deposition) method.

  Further, in addition to the above methods, the organic layer 14 is applied by a laser transfer method, a spin coating method, a dipping method, a doctor blade method, a discharge coating method, a spray coating method, an ink jet method, an offset printing method, a letterpress printing method. , Intaglio printing method, screen printing method, microgravure coating method and other wet process can be used. Depending on the nature of each organic layer and each member, dry process and wet process can be used together I do not care.

(Operations and effects of the organic electroluminescent element 11 and the display device 1)
In the display device 10, a scanning signal is supplied to each pixel from the scanning line driving circuit 130 via the gate electrode of the writing transistor Tr2, and an image signal is held from the signal line driving circuit 120 via the writing transistor Tr2. The capacitance Cs is held. That is, the driving transistor Tr1 is controlled to be turned on / off according to the signal held in the holding capacitor Cs, whereby the driving current Id is injected into the organic electroluminescent elements 11R, 11G, and 11B, and the holes and electrons are recombined. Light emission occurs. This light is transmitted through the anode 13 and the substrate 12 in the case of bottom emission (bottom emission), and in the case of top emission (top emission), the cathode 15, a color filter (not shown), and the sealing substrate 30. Is taken out through.

  At that time, in an organic electroluminescence device composed of a conventionally used material having a high electron mobility, electrons from the electron transport layer to the light emitting layer with respect to the amount of holes supplied from the hole supply layer to the light emitting layer. There was a large amount of supply, and electrons were likely to be excessive in the light emitting layer. For this reason, deterioration of the light emitting layer is likely to occur, leading to a decrease in the life characteristics of the organic electroluminescent element and the display device including the same.

  In contrast, in the present embodiment, it is possible to adjust the amount of electrons supplied from the electron supply layer 14C to the light emitting layer 14B by making the thickness of the electron supply layer 14C thicker than the hole supply layer 14A. Become. However, generally, when the film thickness of the electron supply layer 14C or the hole supply layer 14A is increased, the amount of electrons or holes supplied to the light emitting layer 14B is reduced. However, by using an arylpyridine derivative having high electron mobility as a material for the electron supply layer 14C having a thick film as in the present embodiment, a sufficient amount of electrons supplied to the light emitting layer 14B can be ensured. . That is, the amount of electrons supplied from the electron supply layer 14C to the light emitting layer 14B is adjusted, and electrons and holes are supplied to the light emitting layer 14B without excess or deficiency.

  Thus, in the organic electroluminescent element 11 and the display device 10 using the same according to the present embodiment, the electron supply layer 14C is made thicker than the hole supply layer 14A. And holes are supplied, the deterioration of the light emitting layer 14B is reduced, and the drive deterioration is suppressed. That is, the deterioration of the light emitting layer 14B due to excessive supply of electrons is suppressed and the light emission efficiency is improved, and the lifetime of the organic electroluminescent element 11 and the display device 10 using the same is improved. In addition, since an arylpyridine derivative having a high electron mobility is used for the electron supply layer 14C, the electron supply efficiency can be maintained at a low driving voltage, so that power consumption can be reduced. Therefore, the organic electroluminescent element 11 and the display device 10 having excellent long-term reliability are realized.

  In addition, by forming the electron supply layer 14C thick, the carrier recombination region in the light emitting layer 14B can be arranged at a position away from the cathode 15, so that the cathode 15 is formed by sputtering or the like. Damage to the recombination region can be reduced.

  Note that the organic electroluminescent element 11 is not limited to the active matrix type as in the display device 10 of the present embodiment, and can be applied to a passive type display device, and similar effects can be obtained. . In the case of a passive display device, one of the cathode 15 or the anode 13 is configured as a signal line, and the other is configured as a scanning line.

  Hereinafter, other embodiments of the present invention will be described. In each embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

(Second Embodiment)
Although the configuration of the display device according to the present embodiment is not illustrated, a plurality of organic electroluminescent elements 21R, 21G, and 21B corresponding to red, green, and blue are arranged in a matrix in the display area as in the first embodiment. Display areas arranged in a shape are formed. A pixel driving circuit is provided in the display area. Similar to the first embodiment, a signal line driving circuit and a scanning line driving circuit, which are video display drivers, are provided around the display area.

  FIG. 5 illustrates a cross-sectional configuration of the organic electroluminescent element 21 according to the second embodiment. Similar to the first embodiment, the organic electroluminescent element 21 has a configuration in which an anode 13, an organic layer 24, and a cathode 15 are stacked in this order on a substrate 12. This organic electroluminescent element 21 is different from the first embodiment in that two electron supply layers 24C (24c, 24d) in the organic layer 24 are provided.

  Specifically, the following formula (7A), formula (7B) and formula (7C) are provided between the first electron supply layer 24c made of arylpyridine and the light emitting layer 24B described in the first embodiment. The second electron supply layer 24b made of the benzimidazole derivative shown in FIG.

  A13 in the above formula (7A), formula (7B) and formula (7C) is a polycycle in which an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and an aromatic ring having 3 to 40 carbon atoms are condensed. It is a C6-C120 hydrocarbon group or nitrogen-containing heterocyclic group having an aromatic hydrocarbon group, or a derivative thereof. L is a single bond, and is an aromatic hydrocarbon group or nitrogen-containing heterocyclic group having 6 to 60 carbon atoms. R1 and R2 are each independently a hydrogen atom or a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, a nitrogen-containing heterocyclic group, or 1 to 20 carbon atoms. Or an derivative thereof. n is an integer of 0 to 4, and m is an integer of 0 to 2. However, when m is 2 or more, R1 may be the same group or different groups. When n is 2 or more, R2 may be the same group or different groups.

  Specific examples of the benzimidazole derivatives shown in Formula (7A), Formula (7B) and Formula (7C) include compounds such as Formula (7-1) to Formula (7-176) below. In Formulas (7-1) to (7-176), HAr is a benzimidazole skeleton containing R1 and R2 in Formulas (7A) to (7C), and L is Formulas (7A) to (7C). Corresponds to L in the middle. Ar2 and Ar3 correspond to A13 in the formulas (7A) to (7C), and are bonded to L in the order of Ar2 and Ar3.

  The compound constituting the second electron supply layer 24b may be an imidazole derivative other than the compounds represented by the above formulas (7-1) to (7-176). Specifically, L is not limited to a single bond, an arylene group, a pyridinylene group, or a quinolinylene group, but may be a fluorenin group or a derivative thereof.

  In addition to the effects of the first embodiment, the organic electroluminescent element 21 of the present embodiment has the following effects. By inserting the second electron supply layer 24d made of a benzimidazole derivative into the light emitting layer 14B side of the electron supply layer 24c described in the first embodiment, it is possible to optimally adjust the amount of electrons, There is no excess or deficiency of holes and electrons, and a carrier balance with a sufficiently large carrier supply amount can be obtained. Thereby, high luminous efficiency is obtained. Furthermore, since a voltage change during driving hardly occurs, a low-cost constant current driving circuit can be applied to the driving circuit.

(Third embodiment)
Although the configuration of the display device according to the present embodiment is not illustrated, a plurality of organic electroluminescent elements 31 (31R, 31G, and 31B) of red, green, and blue are displayed in the display area, as in the first embodiment. Display areas arranged in a matrix are formed. A pixel driving circuit is provided in the display area. Similar to the first embodiment, a signal line driving circuit and a scanning line driving circuit, which are video display drivers, are provided around the display area.

  FIG. 6 illustrates a cross-sectional configuration of the organic electroluminescent element 31 according to the third embodiment. The organic electroluminescent element 31 is different from the first embodiment in that three electron supply layers 34C (34c, 34d, 34e) in the organic layer 34 are provided.

  More specifically, a third compound composed of a dibenzimidazole derivative represented by the following formula (8) is provided between the first electron supply layer 34c composed of the arylpyridine derivative and the light emitting layer 34B described in the first embodiment. The electron supply layer 34e is provided. Further, the second electron transport layer 34d made of the benzimidazole derivative shown in the second embodiment is provided on the first electron transport layer made of the arylpyridine derivative, that is, on the cathode 15 side. Each of the electron supply layers 34c, 34d, 34e has a thickness of 5 nm or more, and particularly preferably 10 nm or more. The total thickness of the electron supply layer 34C is preferably 70 nm or more. Note that the second electron transport layer 34d may be omitted.

（Ｙ１〜Ｙ８は、各々独立して水素原子、炭素数６〜６０個のアリール基、アルケニル基、ピリジル基、キノリル基、炭素数１〜２０個のアルキル基、炭素数１〜２０個のアルコキシ基または炭素数５〜６０個の脂肪族環基あるいはそれらの誘導体である。なお、Ｙ７とＹ８は連結基を介して環構造を形成してもよい。）

(Y1 to Y8 are each independently a hydrogen atom, an aryl group having 6 to 60 carbon atoms, an alkenyl group, a pyridyl group, a quinolyl group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. Or an aliphatic cyclic group having 5 to 60 carbon atoms or a derivative thereof, Y7 and Y8 may form a ring structure via a linking group.)

  Specific examples of the benzimidazole derivative represented by the formula (8) include compounds such as the following formulas (8-1) to (8-21).

  In the organic electroluminescent element 31 of the present embodiment, the hole supply layer 34A and the electron supply layer 34C are further increased than the organic electroluminescent element 11 in the first embodiment and the organic electroluminescent element 21 in the second embodiment. It is possible to balance the carrier supplied from the carrier. That is, higher electron injection can be stably supplied to the light emitting layer 33B, and higher efficiency and longer life can be achieved without causing an increase in driving voltage.

(Fourth embodiment)
Although the configuration of the display device according to the present embodiment is not illustrated, the configuration is the same as that of the display device described in the second embodiment and the third embodiment.

  FIG. 7A shows a cross-sectional configuration of the organic electroluminescent element 41 in the fourth embodiment. Similar to the first embodiment, the organic electroluminescent element 4 has a configuration in which an anode 13, an organic layer 44, and a cathode 15 are stacked in this order on a substrate 12. The organic electroluminescent element 4 in the present embodiment has a tandem structure in which two organic layers (first organic layer 44-1 and second organic layer 44-2) are stacked. Different from form.

  Specifically, for example, the first organic layer 44-1 and the second organic layer 44-2 having the same configuration as that of the organic layer 14 described in the first embodiment include the electron supply layer 17A and the hole injection. The layers are stacked via the charge generation layer 17 having a structure in which the layer 17B is stacked.

  The electron supply layer 17A is provided on the anode 13 side and supplies electrons to the light emitting layer 44B1 on the first organic layer 44-1 side. Examples of the material for the electron supply layer 17A include electron donating metals such as alkali metals, alkaline earth metals, and rare earth metals, or compounds thereof. Specifically, for example, Alq3 doped with magnesium (Mg) can be used. Further, the electron supply layer 17A may be a mixed layer in which an organic material is added in addition to the electron donating metal. Organic materials that can be added to the electron supply layer 17A are, for example, the materials of the formula (6-1) to the formula (6-58) and the second electron supply layer 24d shown as the material of the first electron supply layer 24c. Examples of the formula (7-1) to the formula (7-176) are given.

  The hole injection layer 17B is provided on the cathode 15 side and injects holes into the light emitting layer 44B2 on the second organic layer 44-2 side. Specifically, the hole injection layer 17B extracts electrons from the second organic layer 44-2 side and supplies electrons to the first organic layer 44-1 side through the electron supply layer 17A. Holes generated by the extraction of electrons are supplied to the light emitting layer 44B2 of the second organic layer 44-2. As the material of the hole injection layer 17B, a compound having a LUMO level greater than 4.5 eV is preferable. Specifically, the compound may be hexanitrile azatriphenylene represented by the above formula (2-1) or the following formula (9). The indicated compounds can be used.

As shown in FIG. 7B, the charge generation layer 17 is an electron injection layer 17C made of an electron injection material between the electron supply layer 17A and the electron supply layer 44C of the first organic layer 44-1. May be provided. As a material for the electron injection layer 17C, for example, lithium oxide (LiO ₂ ), cesium carbonate (CsCO ₃ ), or a mixture of these oxides and composite oxides can be used. The electron injection layer 17C is not limited to these materials. For example, alkaline earth metals such as calcium (Ca) and barium (Ba), alkali metals such as Li and Cs, indium (In) and Mg are used. A metal having a small work function, or an oxide or composite oxide thereof may be used. Furthermore, a mixture or alloy in which two or more of these oxides and composite oxides are combined to improve safety may be used.

  In the organic electroluminescent element 41 of the present embodiment, since the organic layer has a tandem structure in which two organic layers (first organic layer 44-1 and second organic layer 44-2) are stacked, the first implementation described above. In addition to the effect of the embodiment, the luminous efficiency is further improved, and the extension of the lifetime in the first embodiment has a synergistic effect, so that an organic electroluminescence device having an extremely long lifetime is obtained. Furthermore, since an electron supply layer arylpyridine derivative having a high electron mobility is used for the electron supply layer 44C in a large film thickness ratio, organic electroluminescence having a tandem structure in which the organic layers 44-1 and 44-2 have large film thicknesses. Even in the element, the driving voltage can be kept low.

In addition, although the case where two organic layers 44-1 and 44-2 were laminated | stacked here was shown here, you may laminate | stack not only this but three layers or more. Increasing the number of stacked layers can further improve the light emission efficiency. The theoretical luminous efficiency in the case where two organic layers 44-1 and 44-2 are stacked as in the organic electroluminescent device 41 of the present embodiment has no change in lm / W, and the current efficiency cd / A is 2 When it is doubled or three layers are stacked, it is tripled.

Note that the thickness of the electron supply layer 44C in the case of a tandem element is preferably designed to satisfy the following relationship. When the film thickness of the electron supply layer 44C of the first organic layer 44-1 is d1a and the film thickness of the entire first organic layer 44-1 is d2a, 0.90> d1a / d2a> 0.30. By designing so as to satisfy the relationship, the supply balance of holes and electrons to the light emitting layer 44B of the first organic layer 44-1 can be easily balanced. Similarly to the first organic layer 44-1, when the film thickness of the electron supply layer 44C of the second organic layer 44-2 is d1b and the film thickness of the entire second organic layer 44-2 is d2b, By designing so as to satisfy the relationship of 0.90> d1b / d2b> 0.30, it becomes easy to balance supply of holes and electrons to the light emitting layer 44B of the second organic layer 44-2. From the above, the electron supply layer 14C of the first organic layer 44-1 or the second organic layer 44-2 is, for example, preferably 70 nm to 300 nm, and more preferably 120 nm to 250 nm. Note that it is not always necessary for both the first organic layer 44-1 and the second organic layer 44-2 to satisfy the above-mentioned film thickness relationship, and the first organic layer 44-1 or the second organic layer 44-2 is Any one may satisfy the above relationship. Further, in a tandem element in which three or more layers are stacked, it is sufficient that any organic layer in the element satisfies the above formula. For example, the electron supply of the n-th n-th organic layer 44-n from the anode side When the thickness of the layer 44C is d1n and the total thickness of the n-th organic layer 44-1 is d2n, the layer 44C may be designed to satisfy the relationship of 0.90> d _1n / d _2n > 0.30.

(Modules and application examples)
Hereinafter, application examples of the display device including the organic electroluminescent elements 11, 21, 31 or 41 described in the first to fourth embodiments will be described. This display device displays an externally input video signal or an internally generated video signal as an image or video, such as a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, or a video camera. The present invention can be applied to display devices for electronic devices in all fields.

(module)
The display device including the organic electroluminescent elements 11, 21, 31 or 41 described in the first to fourth embodiments is, for example, a module as shown in FIG. Embedded in various electronic devices. In this module, for example, a region 210 exposed from the protective layer 20 and the sealing substrate 30 is provided on one side of the substrate 11, and wirings of the signal line driving circuit 120 and the scanning line driving circuit 130 are provided in the exposed region 210. An external connection terminal (not shown) is formed by extending. The external connection terminal may be provided with a flexible printed circuit (FPC) 220 for signal input / output.

(Application example 1)
FIG. 9 shows an appearance of a television apparatus to which the display device including the organic electroluminescent elements 11, 21, 31 or 41 described in the first to fourth embodiments is applied. This television apparatus has, for example, a video display screen unit 300 including a front panel 310 and a filter glass 320, and the video display screen unit 300 is configured by the display device according to the above embodiment.

(Application example 2)
FIG. 10 illustrates an appearance of a digital camera to which the display device including the organic electroluminescent elements 11, 21, 31, or 41 described in the first to fourth embodiments is applied. The digital camera includes, for example, a flash light emitting unit 410, a display unit 420, a menu switch 430, and a shutter button 440, and the display unit 420 is configured by the display device according to the above embodiment. .

(Application example 3)
FIG. 11 illustrates an appearance of a notebook personal computer to which the display device including the organic electroluminescent elements 11, 21, 31, or 41 described in the first to fourth embodiments is applied. The notebook personal computer has, for example, a main body 510, a keyboard 520 for inputting characters and the like, and a display unit 530 for displaying an image. The display unit 530 is a display device according to the above embodiment. It is comprised by.

(Application example 4)
FIG. 12 shows an appearance of a video camera to which the display device including the organic electroluminescent elements 11, 21, 31, or 41 described in the first to fourth embodiments is applied. This video camera has, for example, a main body 610, a subject photographing lens 620 provided on the front side surface of the main body 610, a start / stop switch 630 at the time of photographing, and a display 640. Reference numeral 640 denotes the display device according to the above embodiment.

(Application example 5)
FIG. 13 shows an appearance of a mobile phone to which the display device including the organic electroluminescent elements 11, 21, 31, or 41 described in the first to fourth embodiments is applied. For example, the mobile phone is obtained by connecting an upper housing 710 and a lower housing 720 with a connecting portion (hinge portion) 730, and includes a display 740, a sub-display 750, a picture light 760, and a camera 770. Yes. The display 740 or the sub-display 750 is configured by the display device according to the above embodiment.

(Example)
Next, specific examples of the present invention will be described. In addition, Examples 1-1 to 1-8, 3-1 to 3-10 and Comparative Examples 1-1 to 1-6 correspond to the first to third embodiments, and the organic layer 14 (24 , 34) are organic electroluminescent elements 11, 21, 31 provided with one (14C), two (24C) and three (34C) electron supply layers. Examples 2-1 to 2-4 and Comparative Example 2 correspond to the fourth embodiment, and have an tandem structure in which two organic layers 44-1 and 44-2 are stacked. 41. The organic electroluminescent elements 11 (21, 31, 41) of Examples 1 to 3 were generated when the holes injected from the anode 13 and the electrons injected from the cathode 15 were recombined in the light emitting layer 14B. This is an organic electroluminescence device of a top emission type constituted by a resonator structure in which light emission is resonated between the anode 13 and the cathode 15 and taken out from the cathode 15 side opposite to the substrate 12.

First, as the anode 13, an AlNd alloy layer containing 10 wt% Nd was formed with a thickness of 120 nm. Here, the end face of the AlNd alloy layer in the anode 13 becomes the first end face P ₁ of the resonator structure. Next, a cell for an organic electroluminescent element was produced by masking an area other than the light emitting area of 2 mm × 2 mm with an insulating film (not shown) by SiO ₂ vapor deposition. Subsequently, after forming hexanitrile azatriphenylene shown in the formula (2) on the anode 13 as a hole supply layer 14A with a deposition rate of 0.2 to 0.4 nm / sec and a film thickness of 10 nm, a hole transport layer is formed. A compound represented by the formula (4-42) as 14b was formed by a vacuum deposition method at a deposition rate of 0.2 to 0.4 nm / sec and a film thickness of 30 nm.

  Next, the light emitting layer 14B was formed on the hole transport layer 14b using a fluorescent material or a phosphorescent material. As a specific example of the fluorescent material, the compound represented by the formula (10) was used as the host material, and the compound represented by the formula (11) was used as the guest material. As a specific example of the phosphorescent material, the compound represented by the formula (12) is used as the host material, and the compound represented by the formula (13) is used as the guest material so that the dopant concentration is 5% in the film thickness ratio. It was formed with a film thickness of 40 nm by a vacuum deposition method.

  Subsequently, the electron supply layer 14C (24C, 34C) was formed on the light-emitting layer 14B (24B, 34B) with each film thickness using, for example, an arylpyridine derivative represented by the formula (6-58).

  After forming the organic layer 14 as described above, as the first layer 15a of the cathode 15, LiF is formed with a film thickness of about 0.3 nm (deposition rate˜0.01 nm / sec) by vacuum evaporation, and then As the second layer 15b, MgAg was formed to a thickness of 10 nm by a vacuum deposition method, and the cathode 15 having a two-layer structure was provided. In this case, the surface of the second layer 15b on the organic layer 14 side is the second end surface P2 of the resonator structure. The organic electroluminescent element 11 (21, 31) was produced as described above.

  Further, in the organic electroluminescent elements 41 of Examples 2-1 to 2-4 (Comparative Example 2) having a tandem structure, after forming the electron supply layer 44C1, the LiF layer is 0.5 nm as the connection layer 17, and Alq3 + Mg (10 %) Layer and 10 nm of hexanitrile azatriphenylene layer were sequentially deposited. On the connection layer 17, the second organic layer 44-2 was formed in the same manner as the organic layer 14 and the cathode 15 was formed. Thus, an organic electroluminescent element 41 was produced.

With respect to the organic electroluminescent elements 11, 21, 31, 41 produced as described above, the voltage (V) and current efficiency (cd / A) at a current density of 10 mAcm ⁻² were measured. Further, the efficiency ratio and the voltage difference ΔV from the initial voltage when the initial efficiency after 500 hours of constant current driving at 50 ° C. and 30 mAcm ⁻² was set to 1 were measured.

  Table 1 is a list of materials used as the light emitting layer 14B (24B, 34B) and the electron supply layer 14C (24C, 34C) of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-6. is there. Table 2 is a list of materials used as the light emitting layers 44B1 and 44B2 and the electron supply layers 44C1 and 44C2 of Examples 2-1 to 2-4 and Comparative Example 2. Tables 3 and 4 list measurement results of driving voltage (V), luminous efficiency (cd / A), luminance ratio after 500 hours, and voltage increase (ΔV) after 500 hours in Examples 1 and 2. Table 5 is a list of materials used as the light emitting layer 14B (24B, 34B) and the electron supply layer 14C (24C, 34C) of Examples 3-1 to 3-10. Table 6 is a list of measurement results of the drive voltage (V) and the luminance ratio after 500 hours in Example 3. FIG. 14 shows the relationship between the driving voltage and the film thickness of the benzimidazole derivative, which is the material of the second electron supply layer 24d, based on the results in Table 6. FIG. 15 shows the relationship between the film thickness of the dibenzimidazole derivative, which is the material of the third electricity supply layer 34e, and the luminance ratio after 500 hours based on the results in Table 6.

  As can be seen from Tables 3 and 4, the hole supply layers 14A to 34A (the hole injection layers 14a to 34a, the hole transport layers 14b to 34b) are 40 nm, and the electron supply layers 14C to 34C are 120 nm, 140 nm, or 160 nm. Thus, by forming in a thick film, luminous efficiency is improved as compared with Comparative Examples 1 and 2. Further, it can be seen from the result of the luminance ratio after 500 hours that there is almost no decrease in luminance, and that the increase in drive voltage is suppressed by one digit or two digits or more as compared with Comparative Examples 1 and 2. Such a result is not obtained even when the electron supply layers 14C to 34C are formed in a thick film by using a conventionally used material (Alq3). That is, the luminous efficiency is improved by making the film thickness of the electron supply layers 14C to 34C using the compounds represented by the above formulas (6), (7) and (8) thicker than the hole supply layers 14A to 34A. It can be seen that the lifetime characteristics are improved. In addition, the luminous efficiency was significantly improved by increasing the film thickness of the electron supply layer 14C (24C, 34C) in Example 1.

  From FIG. 14, the driving voltage was reduced by laminating the second electron supply layer 24 d made of a benzimidazole derivative between the first electron supply layer 24 c and the cathode 15. From FIG. 15, the luminance ratio after 500 hours, that is, the life characteristics is improved by inserting the third electron supply layer 34e made of a dibenzimidazole derivative between the first electron supply layer 34c and the light emitting layer 34B. I understand that

  The present invention has been described with reference to the first to fourth embodiments and examples. However, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made.

  For example, the material and thickness of each layer described in the above embodiment and the like, or the film formation method and film formation conditions are not limited, and other materials and thicknesses may be used, or other film formation methods and film formation may be performed. It is good also as film | membrane conditions.

  In the first embodiment, the configuration of the organic electroluminescent elements 11R, 11G, and 11B has been specifically described. However, it is not necessary to include all layers, and further include other layers. May be.

  Furthermore, although the case of an active matrix display device has been described in the above embodiment, the present invention can also be applied to a passive matrix display device. Furthermore, the configuration of the pixel driving circuit for active matrix driving is not limited to that described in the above embodiment, and a capacitor or a transistor may be added as necessary. In that case, a necessary driving circuit may be added in addition to the signal line driving circuit 120 and the scanning line driving circuit 130 described above in accordance with the change of the pixel driving circuit.

  In addition, although the display device described in the first embodiment has been described as an example provided with organic electroluminescent elements of red, green, and blue, three colors may not necessarily be provided. Further, the present invention can be applied to a display device including organic electroluminescent elements of these three colors, for example, yellow. Furthermore, in each organic electroluminescent element 11R (11), 11G, 11B, layers other than the light emitting layer 14B may be shared. Further, in the green light emitting element 11G and the blue light emitting element 11B, an electron transport layer 14D made of different materials may be provided so as to be suitable for the respective light emitting layers 14BG and 14CB.

  The organic electroluminescent elements 11 to 41 described in the above-described embodiments and the like have a resonator structure in which, for example, in the organic electroluminescent element 11, the emitted light is resonated and extracted between the anode 13 and the cathode 15, The color purity of the extracted light can be improved, and the intensity of the extracted light near the center wavelength of resonance can be improved. In this case, the reflective end face of the anode 13 on the light emitting layer 14B side is the first end P1 (not shown), the reflective end face of the cathode 15 on the light emitting layer 14B side is the second end P2 (not shown), and the organic layer 14 is In the case of a resonator structure in which the light generated in the light emitting layer 14B is resonated and extracted from the second end portion P2 side as the resonance portion, it is between the first end portion P1 and the second end portion P2 of the resonator. The optical distance L is set so as to satisfy the following formula (1). In practice, the optical distance L is preferably selected so as to be a positive minimum value satisfying the expression (1).

In the above formula (1), L is the optical distance between the first end P1 and the second end P2, and Φ is the phase shift Φ ₁ of the reflected light generated at the first end P1 and the second end. The sum (Φ = Φ ₁ + Φ ₂ ) (rad) of the phase shift Φ ₂ of the reflected light generated at P 2, λ is the peak wavelength of the spectrum of light desired to be extracted from the second end P 2 side, and m is positive when L is positive Each represents an integer. In the formula (1), L and λ may have the same unit. For example, the unit is (nm).

In the organic light emitting device 11, the optical distance L ₁ between the maximum light emission position of the light emitting layer 14B and the first end P1 satisfies the following formula (2), and the maximum light emission position and the second end P2 The optical distance L2 between them is adjusted so as to satisfy the following formula (3). Here, the maximum light emission position refers to a position having the highest light emission intensity in the light emission region. For example, in the case where light is emitted from both the anode 13 side and the cathode 15 side of the light emitting layer 14B, the interface having the larger emission intensity is used.

In the above formula (2), tL ₁ is the optical theoretical distance between the first end P1 and the maximum light emission position, a ₁ is the correction amount based on the light emission distribution in the light emitting layer 14B, and λ is the spectrum of the light to be extracted. , Φ ₁ represents the phase shift (rad) of the reflected light generated at the first end P1, and m ₁ represents 0 or an integer.

In the above formula (3), tL ₂ is the optical theoretical distance between the second end portion P2 and the maximum light emission position 13E, a ₂ is the correction amount based on the light emission distribution in the light emitting layer 14B, and λ is the light to be extracted. The peak wavelength of the spectrum, Φ ₂ represents the phase shift (rad) of the reflected light generated at the second end P2, and m ₂ represents 0 or an integer.

  The above formula (2) indicates that when light directed toward the anode 13 out of the light generated in the light emitting layer 14B is reflected by the first end P1 and returned, the phase of the return light and the phase at the time of light emission Is the same, and is in a relationship of strengthening with the light emitted toward the cathode 15 among the emitted light. Further, when the light traveling toward the cathode 15 out of the light generated in the light emitting layer 14B is reflected and returned by the second end portion P2, the expression (3) indicates the phase of the return light and the phase during light emission. In order to have a strengthening relationship with the light emitted toward the anode 13.

In the organic electroluminescent element 11 of the present embodiment, the electron transport layer 14d is formed thicker than the total film thickness of the hole supply layer 14A, so that m ₁ > m ₂ in the above formulas (2) and (3). It is possible to design as follows. Thereby, the light extraction efficiency can be increased.

The optical theory distance tL ₂ of formula (2) optical theory distance tL ₁ and Equation (3) of, when considering that there is no spread in the light-emitting area, the first end portion P1 or the second end portion P2 This is a theoretical value in which the amount of phase change at the time and the amount of phase change due to progress cancel each other, and the phase of the return light and the phase at the time of light emission are the same. However, since the light emission part is usually wide, correction amounts a ₁ and a ₂ based on the light emission distribution are added in the expressions (2) and (3).

Although the correction amounts a ₁ and a ₂ vary depending on the light emission distribution, the maximum light emission position is on the cathode 15 side of the light emitting layer 14B, and the light emission distribution extends from the maximum light emission position to the anode 13 side, or the maximum light emission position is light emission. When it is on the anode 13 side of the layer 14B and the light emission distribution spreads from the maximum light emission position to the cathode 15 side, it can be obtained, for example, by the following formula (4).

  In the formula (4), b is a value within the range of 2n ≦ b ≦ 6n when the light emission distribution in the light emitting layer 14B extends from the maximum light emission position to the anode 13, and the direction from the maximum light emission position to the cathode 15 Is a value in the range of −6n ≦ b ≦ −2n, s is a physical property value (1 / e attenuation distance) regarding the light emission distribution in the light emitting layer 13C, and n is a peak of the spectrum of light to be extracted. It is an average refractive index between the first end P1 and the second end P2 at the wavelength λ.

  In the case of a top-surface light emitting device configured with a resonator structure in which emitted light is resonated and extracted between the anode 13 and the cathode 15, the cathode 15 preferably has the following configuration. For example, the second cathode 15B is configured using a semi-transmissive reflective material such as Mg—Ag, and the emitted light is resonated between the second cathode 15B and the anode 13. The second cathode 15B is made of, for example, a transparent SiNx compound, and is formed as a sealing electrode for suppressing electrode deterioration.

  In the first to fourth embodiments and examples, the top emission organic electroluminescence elements 11 to 41 are described. However, the present invention is not limited to this, and at least light emission is performed between the anode and the cathode. The present invention can be widely applied to an organic electroluminescence device formed by sandwiching an organic layer having layers. In other words, the cathode, organic layer, and anode are stacked in order from the substrate side, and the electrode located on the substrate side (the lower electrode as the cathode or anode) is made of a transparent material and positioned on the opposite side of the substrate. The electrode (upper electrode as a cathode or anode) is made of a reflective material, so that it can be applied to a bottom emission type (so-called transmission type) organic electroluminescence device in which light is extracted only from the lower electrode side. is there.

  Furthermore, as long as it is an organic electroluminescent element in which an organic layer is sandwiched between a pair of electrodes (anode and cathode) and an electrode between them, other components (for example, an inorganic compound layer or an inorganic component) may be included. I do not care.

  11, 21, 31, 41... Organic electroluminescent element, 12... Substrate, 13... Anode, 14, 24, 34, 44-1, 44-2 ... organic layer, 14 A, 24 A, 34 A, 44 A 1, 44 A 2. Supply layer, 14a, 24a, 34a, 44a1, 44a2 ... hole injection layer, 14b24b, 34b, 44b1, 44b2 ... hole transport layer, 14B, 24B, 34B, 44B1, 44B2 ... light emitting layer, 14C, 24C, 34C, 44C1, 44C2 ... electron supply layer, 24c, 34c ... first electron supply layer, 24d, 34d ... second electron supply layer, 34e ... third potential supply layer, 15 ... cathode, 16 ... partition, 17 ... charge Generation layer, 17A ... electron supply layer, 17B ... hole injection layer, 17C ... electron injection layer, 20 ... protective layer, 30 ... substrate for sealing

Claims (12)

The anode,
An organic layer including a hole supply layer formed on the anode, a light emitting layer, and an arylpyridine derivative represented by the formula (1), and an electron supply layer having a thickness larger than that of the hole supply layer in this order. When,
An organic electroluminescent device comprising: a cathode formed on the organic layer.

(Ar1 is an aromatic hydrocarbon group having 6 to 50 nuclear carbon atoms or a derivative thereof. X is an aromatic heterocyclic group or a derivative thereof containing at least a pyridinyl group. M is an integer of 1 to 5. , N is an integer of 1 to 6. However, when m is 2 or more, Ar1 may be the same group or different groups, and when n is 2 or more, X is the same group or different groups. May be.) The electron supply layer includes a first electron supply layer including the arylpyridine in order from the light emitting layer side, and a benzimidazole derivative represented by any one of the formulas (2A), (2B), and (2C). The organic electroluminescent element according to claim 1, which is formed by laminating two electron supply layers.

(A is a C1-C20 carbon atom having a C1-C20 alkyl group, a C1-C20 alkoxy group, and a polycyclic aromatic hydrocarbon group condensed with a C3-C40 aromatic ring. A hydrogen group, a nitrogen-containing heterocyclic group, or a derivative thereof, L is a single bond, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a nitrogen-containing heterocyclic group, and R 1 is independently a hydrogen atom or A halogen atom, an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, a nitrogen-containing heterocyclic group, an alkoxy group having 1 to 20 carbon atoms, or a derivative thereof; (It is an integer from 0 to 4, and m is an integer from 0 to 2.) The electron supply layer includes a third electron supply layer containing a dibenzimidazole derivative represented by the formula (3) in order from the light emitting layer side and a first electron supply layer containing the arylpyridine in order from the light emitting layer side. The organic electroluminescent element according to claim 1 formed.

(Y1 to Y8 are each independently a hydrogen atom, an aryl group having 6 to 60 carbon atoms, an alkenyl group, a pyridyl group, a quinolyl group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. Or an aliphatic cyclic group having 5 to 60 carbon atoms or a derivative thereof, Y7 and Y8 may form a ring structure via a linking group.)   The electron supply layer includes, in order from the light emitting layer side, a third electron supply layer containing a dibenzimidazole derivative represented by the formula (4), a first electron supply layer containing the arylpyridine, and a benzimidazole represented by the formula (3). The organic electroluminescent element according to claim 1, wherein a second electron supply layer containing a derivative is laminated.   The organic electroluminescence device according to claim 1, wherein the hole supply layer has a thickness of 1 nm to 100 nm.   The organic electroluminescent element according to claim 5, wherein the electron supply layer has a thickness of 70 nm to 300 nm.   2. The organic electroluminescence device according to claim 1, wherein the relationship between the film thickness d <b> 1 of the electron supply layer and the film thickness d <b> 2 of the organic layer is 0.30 <d1 / d2 <0.90.   The organic electroluminescent element according to claim 1, wherein the light emitting layer includes a phosphorescent material as a host material.   The organic electroluminescent device according to claim 8, wherein the phosphorescent material is a carbazole derivative or a quinolinol complex derivative.   The organic electroluminescent element according to claim 1, which has a tandem structure in which at least two organic layers are stacked via a charge generation layer.   The organic electroluminescence device according to claim 10, wherein the charge generation layer has a structure in which an electron supply layer and a hole injection layer are laminated in order from the anode side. Provided with a plurality of organic electroluminescent elements on the substrate,
The organic electroluminescent element is:
The anode,
An organic layer including a hole supply layer formed on the anode, a light emitting layer, and an arylpyridine derivative represented by the formula (1), and an electron supply layer having a thickness larger than that of the hole supply layer in this order. When,
A display device comprising: a cathode formed on the organic layer.

(Ar1 is an aromatic hydrocarbon group having 6 to 50 nuclear carbon atoms or a derivative thereof. X is an aromatic heterocyclic group or a derivative thereof containing at least a pyridinyl group. M is an integer of 1 to 5. , N is an integer of 1 to 6. However, when m is 2 or more, Ar1 may be the same group or different groups, and when n is 2 or more, X is the same group or different groups. May be.)

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