JP5620163B2 - Organic thin film electroluminescent element, lighting device and self-assembled monolayer material used therefor - Google Patents

Description

  The present invention relates to an organic thin film electroluminescent element, a lighting device, and a self-assembled monolayer material used therefor.

  An organic thin film electroluminescent element (hereinafter referred to as “organic EL element”) having a structure in which at least one light emitting organic compound layer (organic electroluminescence layer) is sandwiched between a cathode and an anode is compared with an inorganic EL element. Thus, the applied voltage can be greatly reduced, and various light emitting elements can be manufactured (see, for example, Non-Patent Documents 1 to 3 and Patent Documents 1 to 3).

  At present, in order to obtain a higher performance organic EL element, various device structures including material development and improvement have been proposed, and active research is being conducted.

  In addition, for this organic EL element, various luminescent color elements, high luminance and high efficiency elements have already been developed, and there are various practical applications such as use as a pixel of a display device and use as a light source. It is being considered. Among them, one of the major challenges is to achieve both long life and low cost. Polymer organic EL elements continue to be considered as the leading technology for cost reduction. However, there is a problem in extending the service life, and one of the factors is the interface. Further, development of organic-inorganic hybrid LEDs (for example, see Non-Patent Document 4 and Patent Document 4) is being promoted as a new method for reducing costs, but the problem of the interface cannot be avoided in the same manner.

JP-A-10-153967 Japanese Patent Laid-Open No. 10-12377 Japanese Patent Laid-Open No. 11-40358 JP 2007-53286 A

Appl. Phys. Lett. 51 (12), 913, 1987 Appl. Phys. Lett. 71 (1), 34, 1997 Nature 357, 477, 1992 Appl. Phys. Lett. 89, 183510, 2006

  Therefore, the object of the present invention is to reduce the cost of high-molecular organic EL elements and organic-inorganic hybrid LEDs that can be expected to reduce costs, as well as low-molecular organic EL elements that are more expensive to reduce interface degradation. It is an object of the present invention to provide an organic thin film electroluminescent element having a low cost, a high efficiency and a long lifetime, and an illumination device including the light emitting element.

  Such an object is achieved by the present invention described below.

  (1) An anode and a cathode, one or more organic compound layers sandwiched between the anode and the cathode, and an energy barrier for the main carrier of one or more layers between the layers, and energy for the opposite carrier This is achieved by an organic thin film electroluminescent device characterized by having a self-assembled monolayer that does not serve as a barrier. The “carrier” shown here is an electron or a hole, and the “main carrier” means a carrier on the side that is principally the main component in the layer or interface. For example, it is an electron at the cathode / electron transport layer interface, and a hole at the light emitting layer / hole transport layer interface. “No energy barrier” means that the energy difference estimated from the energy level of a single component is not a barrier for the carrier.

  Thereby, the organic thin film electroluminescent element which has a low molecular and high molecular material which can express the outstanding luminous efficiency with a long lifetime is obtained.

(2) an anode and a cathode, one or more organic compound layers sandwiched between the anode and the cathode, at least between the anode and the organic compound layer, or between the cathode and the organic compound layer A self-assembled monomolecule having at least one metal oxide thin film between them and having an energy barrier for one or more main carriers between each layer and not an energy barrier for the opposite carriers This is achieved by an organic thin film electroluminescent device characterized by having a film.
An energy diagram when the main carrier is an electron is shown in FIG. Although this energy diagram shows an organic-inorganic hybrid LED as an example, the present invention is not limited to this. The bottom of each square shows the highest energy level of the highest occupied orbital level (HOMO) or valence band (VB), and the upper side shows the lowest energy level of the lowest unoccupied orbital level (LUMO) or conduction band (CB). Shows the rank. If the hole injection is sufficient, the holes are accumulated at the interface of the electron injecting metal oxide layer 6. In the conventional type having no self-assembled monolayer, the radical cation of the organic compound layer 4 is in direct contact with the surface of the metal oxide, so that the organic compound is further deteriorated. However, when a self-assembled monolayer having a site where the radical cation is stable is disposed on the electron injecting metal oxide layer 6, the radical cation does not directly contact the metal oxide surface, and the local electric field can be stably observed. Can be generated. At this time, the self-assembled monolayer can realize an energy level in which holes are easily injected, that is, a state having no energy barrier, and an energy level in which electrons cannot be injected, that is, a state having an energy barrier. If possible, the driving can be realized more preferably. Electron injection is directly injected into the organic compound layer 4 by tunneling. This also prevents carrier recombination on the self-assembled monolayer. The opposite is true when the main carrier is a hole.

  (3) More preferably, it is achieved by an organic thin film electroluminescent device in which a self-assembled monomolecular film exists on the metal oxide thin film interface.

  (4) More preferably, the metal oxide thin film is achieved by an organic thin film electroluminescent device including a titanium oxide thin film.

  As a result, an organic thin film electroluminescent device having an organic / inorganic hybrid LED structure that does not require a sealing structure in principle and capable of exhibiting excellent luminous efficiency at low cost and long life can be obtained.

(5) By using a self-assembled monolayer material in which the self-assembled monolayer is represented by the general formula (1), an organic thin-film electroluminescent device that is inexpensive, has a long life and is highly efficient can be obtained.
General formula

_{However, R 1, R 2, R} 3 is an alkoxy group or a halogen atom, X is a linking group, Y is a functional group. Y represents a functional group in which the radical cation has a stable structure at the interface where the main carrier is an electron, and the radical anion has a stable structure at the interface where the main carrier is a hole.

  (6) When using a self-assembled monolayer material in which the total length of the molecular chain connected to Si, the linking group X, and the functional group Y is 2 nm or less, the main carrier can be injected well by the tunneling mechanism, so it is cheaper. A long-life and high-efficiency organic thin film electroluminescent device can be obtained.

  (7) An illuminating device provided with these organic thin film electroluminescent elements is obtained.

  Thereby, the illuminating device which can express the outstanding luminous efficiency with low cost and long lifetime is obtained.

According to the present invention, it is possible to provide an organic thin-film light-emitting element that is inexpensive, highly efficient, and has a long lifetime, and a lighting device including the same.

It is an energy diagram in the case of the organic thin film electroluminescent element which has the organic inorganic hybrid LED structure in this invention. It is a figure which shows typically the longitudinal cross-section of Embodiment 1 of the organic thin film electroluminescent element which has the organic inorganic hybrid LED structure in this invention. It is a figure which shows typically the longitudinal cross-section of Embodiment 2 of the organic thin film electroluminescent element using the polymeric material in this invention. It is a graph which shows the result of having evaluated initial brightness | luminance with respect to the light emitting element manufactured in Example 1 and Comparative Examples 1-1 and 1-2. It is a graph which shows the result of having evaluated the current half life by the constant voltage drive with respect to the light emitting element manufactured in Example 1 and Comparative Examples 1-1 and 1-2. It is a graph which shows the result of having evaluated initial brightness | luminance with respect to the light emitting element manufactured in Example 2 and Comparative Example 2. FIG. It is a graph which shows the result of having evaluated the current half life by the constant voltage drive with respect to the light emitting element manufactured in Example 2 and Comparative Example 2. FIG.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an organic thin film electroluminescent element and an illuminating device of the invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 2 is an energy diagram in the case of an organic thin film electroluminescent device having an organic-inorganic hybrid LED structure in the present invention. FIG. 3 is an energy diagram in the case of an organic thin film electroluminescent device having a polymer organic EL structure in the present invention. Here, an organic-inorganic hybrid thin film electroluminescent element will be described as an example.

  2 includes an organic compound between a cathode (one electrode) 3, an anode (the other electrode) 5, and between the cathode 3 and the anode 5 (between a pair of electrodes). A layer 4 is inserted, and a hole injecting metal oxide layer 7 is provided between the organic compound layer 4 and the anode 5, and an electron injecting metal oxide layer 6 is provided between the organic compound layer 4 and the cathode 3. Are provided respectively. The entire light emitting element 1 is provided on the substrate 2. This light emitting element is thus completed. Here, the sealing structure is not necessary in principle. However, there is no problem even if the sealing structure is used from the viewpoint of maintaining the insulating properties of the electrodes.

  The substrate 2 serves as a support for the light-emitting element 1 and is also a support for directly producing a cathode here. The light emitting element 1 of the present embodiment is not limited in the light extraction direction, and is configured to extract light from the substrate 2 side (bottom emission type) and from the anode 5 on the side opposite to the substrate 2. There are three possible cases: a configuration for taking out (top emission type) and a case where both are possible (transparent type). In the case of the bottom emission type, each of the substrate 2 and the cathode 3 is substantially transparent (colorless transparent, colored transparent, or translucent).

  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 of the 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.

  Unlike the normal organic EL element, the cathode 3 in this structure is not subject to the restriction of reducing the work function. In other words, a material having a large work function can be used, which is desirable for obtaining stability in the atmosphere. Other required characteristics are excellent electrical conductivity, and excellent transmissivity in the case of bottom emission type and transparent type. The same applies to the anode 5, and it is desirable to use a material having a large work function, excellent conductivity, and excellent transparency in the case of the top emission type and the transparent type.

Examples of constituent materials of the cathode 3 and the anode 5 include ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , and Al-containing ZnO. Examples thereof include oxides such as Au, Pt, Ag, Cu, and alloys containing these, and one or more of these can be used in combination.

  The average thickness of the cathode 3 is not particularly limited, but is preferably about 10 to 200 nm, and more preferably about 30 to 150 nm. Even when an opaque material such as Au, Pt, Ag, or Cu is used, the cathode can be used as a bottom emission type or a transparent type cathode by setting the average thickness to about 10 to 30 nm, for example.

  On the other hand, the average thickness of the anode 5 is not particularly limited, but is preferably about 10 to 10000 nm, and more preferably about 30 to 150 nm. Even when an opaque material such as Au, Pt, Ag, or Cu is used, it can be used as a top emission type or transparent type anode by setting the average thickness to about 10 to 30 nm, for example.

  The organic compound layer 4 is a layer responsible for light emission, and is a layer containing at least a light emitting material. Therefore, the light emitting material and the hole transporting organic material may be mixed or stacked. As a constituent material of the light emitting material, various polymer light emitting materials (polymer materials) and various low molecular light emitting materials (low molecular materials) can be used alone or in combination.

  As the light emitting material, various polymer light emitting materials (polymer materials) and various low molecular weight light emitting materials (low molecular materials) can be used alone or in combination.

  Examples of the polymer light-emitting material include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), poly (alkyl, phenylacetylene) (PAPA), and poly (para-para-). Fenvinylene) (PPV), poly (2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly (para-phenvinylene) (CN-PPV), poly (2-dimethyloctyl) Polyparaphenylene vinylene compounds such as silyl-para-phenylene vinylene (DMOS-PPV), poly (2-methoxy, 5- (2′-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV), poly ( 3-alkylthiophene) (PAT), poly (oxypropylene) Polythiophene compounds such as riol (POPT), poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-alt-benzothiadiazole) (F8BT), α, ω-bis [N, N′-di (Methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7-zyl] (PF2 / 6am4), poly (9,9-dioctyl-2,7-divinylenefluore Polyfluorene compounds such as nyl-ortho-co (anthracene-9,10-diyl), poly (para-phenylene) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO-PPP) A polyparaphenylene compound such as poly (N-vinylcarbazole) (PVK), Polysilane compounds such as li (methylphenylsilane) (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylylphenylsilane) (PBPS), and boron compounds described in Japanese Patent Application No. 2010-28273 Based polymer materials and the like.

On the other hand, as a low-molecular light-emitting material, for example, a tricoordinate iridium complex having a 2,2′-bipyridine-4,4′-dicarboxylic acid represented by the following chemical formula 2 as a ligand, Factory (2- Phenylpyridine) iridium (Ir (ppy) ₃ ), 8-hydroxyquinoline aluminum (Alq ₃ ), tris (4-methyl-8quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinoline zinc (Znq ₂ ), (1,10-phenanthroline) -tris- (4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-dionate) europium (III) (Eu (TTA) ₃ (phen)) 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphine various metal complexes such as platinum (II), Benzene compounds such as rubenzene (DSB) and diaminodistyrylbenzene (DADSB), naphthalene compounds such as naphthalene and nile red, phenanthrene compounds such as phenanthrene, chrysene and chrysene compounds such as 6-nitrochrysene Perylene compounds such as perylene, N, N′-bis (2,5-di-t-butylphenyl) -3,4,9,10-perylene-di-carboximide (BPPC), and coronene Coronene compounds, anthracene compounds such as anthracene and bisstyrylanthracene, pyrene compounds such as pyrene, 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM) pyran compounds, acridine like acrylic Compounds, stilbene compounds such as stilbene, thiophene compounds such as 2,5-dibenzoxazole thiophene, benzoxazole compounds such as benzoxazole, benzimidazole compounds such as benzimidazole, 2,2 ′ -(Para-phenylenedivinylene) -benzothiazole compounds such as bisbenzothiazole, bistyryl (1,4-diphenyl-1,3-butadiene), butadiene compounds such as tetraphenylbutadiene, naphthalimide, etc. Naphthalimide compounds, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, 1,2,3,4,5-pentaphenyl- 1,3-cyclopenta Cyclopentadiene compounds such as ene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyridine compounds such as pyrrolopyridine and thiadiazolopyridine, 2,2 ′, 7,7′-tetraphenyl- Spiro compounds such as 9,9′-spirobifluorene, metal or metal-free phthalocyanine compounds such as phthalocyanine (H ₂ Pc) and copper phthalocyanine, and JP2009-155325A and Japanese Patent Application No. 2010-28273 The boron compound material described in the above.
In the case of a polymer organic thin film electroluminescent device, the hole transporting organic material used as the hole injection / transport layer promotes the transport of holes in the organic compound layer.

  As the hole transporting organic material, various p-type polymer materials and various p-type low molecular materials can be used alone or in combination.

  Examples of the p-type polymer material (organic polymer) include polyarylamines, fluorene-arylamine copolymers, fluorene-bithiophene copolymers, poly (N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, Examples thereof include polyalkylthiophene, polyhexylthiophene, poly (p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof.

  Moreover, the said compound can also be used as a mixture with another compound. As an example, the polythiophene-containing mixture includes poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS).

On the other hand, examples of p-type low molecular weight materials include 1,1-bis (4-di-para-triaminophenyl) cyclohexane and 1,1′-bis (4-di-para-tolylaminophenyl). Arylcycloalkane compounds such as -4-phenyl-cyclohexane, 4,4 ′, 4 ″ -trimethyltriphenylamine, N, N, N ′, N′-tetraphenyl-1,1′-biphenyl-4 , 4′-diamine, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (TPD1), N, N′-diphenyl- N, N′-bis (4-methoxyphenyl) -1,1′-biphenyl-4,4′-diamine (TPD2), N, N, N ′, N′-tetrakis (4-methoxyphenyl) -1, 1′-biphenyl-4,4′-diamine (TPD3), , N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD), arylamine compounds such as TPTE, N, N, N ′, N′-tetraphenyl-para-phenylenediamine, N, N, N ′, N′-tetra (para-tolyl) -para-phenylenediamine, N, N, N ′, N′-tetra (meta-) Phenylenediamine compounds such as (tolyl) -meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilbene, and 4-di-para-tolylaminostilbene stilbene compounds, oxazole-based compounds such as _{O x} Z, triphenylmethane, triphenylmethane compounds such as m-MTDATA, 1- Pyrazoline compounds such as enyl-3- (para-dimethylaminophenyl) pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxa Diazole, oxadiazole compounds such as 2,5-di (4-dimethylaminophenyl) -1,3,4, -oxadiazole, anthracene, anthracene such as 9- (4-diethylaminostyryl) anthracene Compound, fluorenone, 2,4,7, -trinitro-9-fluorenone, 2,7-bis (2-hydroxy-3- (2-chlorophenylcarbamoyl) -1-naphthylazo) fluorenone such as fluorenone, polyaniline Aniline compounds like silane Compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) pyrrolopyrrole, fluorene compounds such as fluorene, porphyrins, porphyrins such as metal tetraphenylporphyrin Compounds, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, metal or metal-free phthalocyanine compounds such as iron phthalocyanine, copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium Metallic or metal-free naphthalocyanine compounds such as phthalocyanine, N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine, N, N, N ′, N′-tetraphenylbenzidine Benzidine like Compounds, and the like.

  The average thickness of the organic compound layer 4 is not particularly limited, but is preferably about 10 to 150 nm, and more preferably about 40 to 100 nm.

The organic compound layer 4 transports holes injected from the hole injecting metal oxide layer 7 and receives electrons from the electron injecting metal oxide layer 6. Holes and electrons recombine, and excitons (excitons) are generated by the energy released during the recombination, and energy (fluorescence and phosphorescence) is emitted (emitted) when the excitons return to the ground state. .
Among these, as a constituent material of the organic compound layer 4, a material mainly composed of a polymer light-emitting material is preferable. A polymer material that can be formed by a liquid phase process can make more contact surfaces with the electron injecting metal oxide layer 6. Thereby, it can be made more excellent in luminous efficiency.
In particular, as a constituent material of the organic compound layer 4, a polymer mainly composed of polyfluorene or a derivative thereof, a polymer composed of a boron compound described in JP-A No. 2009-155325, or a Japanese Patent Application No. 2010-28273. A light emitting material mainly composed of a polymer described in No. 1 is preferred. Thereby, the said effect can be improved more.

  The electron injecting metal oxide layer 6 injects electrons from the cathode 3 and transports them to the organic compound layer 4.

A metal oxide constituting such an electron injecting metal oxide layer 6 is preferably one having a high energy level of a conduction band, and is not particularly limited. However, titanium oxide (TiO ₂ ), zinc oxide (ZnO), Examples include tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO ₂ ), and the like, and one or more of these may be used in combination. Can do.

  The film forming method of the electron injecting metal oxide layer 6 is not particularly limited, and a chemical vapor deposition method (CVD) such as plasma CVD, thermal CVD, laser CVD, or vacuum vapor deposition, which is a vapor deposition method. , Dry plating methods such as sputtering and ion plating, thermal spraying methods, and wet plating methods such as electrolytic plating, immersion plating and electroless plating, which are liquid phase film forming methods, sol-gel methods, MOD methods, spray pyrolysis methods Printing techniques such as a doctor blade method using a fine particle dispersion, a spin coating method, an ink jet method, and a screen printing method can be used. In this structure, the spray pyrolysis method was used.

  The average thickness of the electron injecting metal oxide layer 6 is not particularly limited, but is preferably about 1 to 1000 nm, and more preferably about 20 to 200 nm.

  The hole injecting metal oxide layer 7 injects holes from the anode 5 and transports them to the organic compound layer 4.

The metal oxide constituting the hole-injecting metal oxide layer 7 is preferably a compound having a large work function, and is not particularly limited. For example, vanadium oxide (V ₂ O ₅ ), molybdenum oxide (MoO ₃₎ ), Ruthenium oxide (RuO ₂ ) and the like, and one or more of these can be used in combination.

  Among these, those containing vanadium oxide or molybdenum oxide as the main component are particularly suitable. By using vanadium oxide or molybdenum oxide as a main material, the hole injecting metal oxide layer 7 can be made particularly excellent in the above-described ability.

  In particular, vanadium oxide or molybdenum oxide has a high hole transport property in itself, so that it is possible to suitably prevent a decrease in the efficiency of hole injection from the anode 5 to the organic compound layer 4. is there.

  The film forming method of the hole injecting metal oxide layer 7 is not particularly limited, and a chemical vapor deposition method (CVD) such as plasma CVD, thermal CVD, laser CVD, or vacuum, which is a vapor deposition method, Dry plating methods such as vapor deposition, sputtering and ion plating, thermal spraying methods, and liquid plating methods such as electrolytic plating, immersion plating, electroless plating, etc., sol-gel method, MOD method, spray pyrolysis Printing techniques such as a method, a doctor blade method using a fine particle dispersion, a spin coating method, an ink jet method, and a screen printing method can be used. In this structure, a vacuum deposition method was used.

  The average thickness of the hole injecting metal oxide layer 7 is not particularly limited, but is preferably about 1 to 1000 nm, and more preferably about 5 to 50 nm.

  These are suitable structures for organic-inorganic hybrid LEDs.

  The present invention is characterized in that a self-assembled monomolecular film is formed at the interface between the electron injecting metal oxide layer 6 and the organic compound layer 4 having this structure.

  The material of the self-assembled monomolecular film is subject to oxidation resistance and reduction resistance, and details are described below.

R ₁ , R ₂ , and R ₃ may be the same or different. Alkoxides such as methoxy and ethoxy groups, and halogens such as chlorine and fluorine are conceivable.

X is a linking group that connects to a functional group, and examples of the linking group include an aliphatic hydrocarbon group that may have a carbon-heteroelement bond or an arylene group that may be substituted.
Here, examples of the aliphatic hydrocarbon group include straight-chain, branched or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms.
Specific examples of the saturated hydrocarbon group include, for example, methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene. Group, dodecamethylene group, octadecyl group, methylmethylene group, dimethylmethylene group, methylethylene group, methyleneethylene group, ethylethylene group, 1,2-dimethylethylene group, 1-methyltrimethylene group, 1-methyltetramethylene group 1,3-dimethyltrimethylene group, 1-ethyl-4-methyl-tetramethylene group, cyclohexylene group and the like. Specific examples of the unsaturated hydrocarbon group include a vinylene group, an ethynylene group, a propenylene group, a 2-butenylene group, a 2-butynylene group, and a 1-vinylethylene group. Further, these hydrocarbon groups may have a carbon-heteroelement bond in the main chain.
For example,

One or two or more bonds such as the above may be contained in the linking group.
The arylene group which may be substituted is an arylene group having one or more benzene rings which may have a substituent, and two or more benzene rings which may have a substituent are condensed. A bisarylene group in which two or more benzene rings which may have a substituent are connected via an arylene group or a divalent group, and a heteroaromatic ring group which may further have a substituent, Specifically,

(In the formula, R represents a substituent, and n Rs may be the same or different. N represents an integer of 0 to 8. P represents a divalent group. Q represents —NH—, -N (Ph)-, -N (Et)-, -O-, -S-).
Here, R is preferably an alkyl group, an alkenyl group, an aryl group, an alkoxyl group, or an amino group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a tert-butyl group. Examples of the alkenyl group include a vinyl group, an allyl group, and a 2-butenyl group.
Examples of the aryl group include a phenyl group, a xylyl group, and a mesityl group. Examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the amino group include a diethylamino group and a diphenylamino group. The divalent is a group _{P, -CH 2 -, - C} (CH 3) 2 -, - CHCH 3 -, - CH (C 2 H 5) -, - CH (C 3 H 7) - _{, -C (cyclo-C 5 H} 10) -, - CH (C 6 H 4) -, - C (C 2 H 5) 2 -, - C (C 8 H 17) 2 -, - O -, - _{S -, - SO -, -} SO 2 -, - SO 3 -, - CO -, - COO -, - NH -, - N (Ph) -, - N (C 2 H 5) -, - CONH-, -NHCONH- and the like.
A group in which an aliphatic hydrocarbon group and an arylene group are linked directly or via a carbon-heteroelement bond can also be regarded as a linking group X.

Y is a functional group, and is a site that accumulates (maintains) carriers in the device. Therefore, those having a molecular structure that can be maintained by adding electrons or holes are candidates. For example, the (cathode) side radical cation whose main carrier is an electron is a stable material (A), and the (anode) side radical anion whose main carrier is a hole is a stable material (B). Moreover, a material (C) in which both radical cation and radical anion are stable can be mentioned. Specifically, materials used as an electron transport material, that is, pyridine, quinoline, oxadiazole, triazole, silole, benzothiadiazole, benzimidazole, and further, JP2009-155325A and Japanese Patent Application No. 2010- Boron compound materials described in 28273 are candidates for (A), and materials used as hole transport materials, that is, triphenylamine, thiophene, and the like are candidates for (B). Furthermore, materials used as bipolar materials, ie, carbazole, are candidates for (C).
Y may be substituted for a plurality of linking groups X.

  As an example, a synthesis method of F8TES having dioctylfluorene in Y is shown below.

A diethyl ether solution (53 mL) containing 2-bromo-9,9-dioctylfluorene (5.0 g, 10.6 mmol) synthesized with reference to non-patent literature (Dalton Transactions, 2003, p. 74-84) is used. While stirring at 78 ° C., a hexane solution of normal butyl lithium (1.56 M, 6.8 mL, 10.6 mmol) was added dropwise. This solution was stirred at -78 ° C for 1 hour, warmed to room temperature, and further stirred for 2 hours. The mixture was cooled again to −78 ° C., and slowly added to a diethyl ether solution (80 mL) of chlorotriethoxysilane (4.23 g, 21.3 mmol) prepared in another container using a cannula at −78 ° C. The reaction solution was stirred at −78 ° C. for 1 hour and then stirred at room temperature overnight. The mixture was cooled again to −78 ° C., and a small amount of water was added to stop the reaction. Hexane was added, and the organic layer was washed with water and dried over magnesium sulfate. After filtration, the filtrate was concentrated with a rotary evaporator, and the residue was purified by silica gel column chromatography (hexane: ethyl acetate = 20: 1) to give 2-triethoxysilyl-9,9-dioctylfluorene (F8TES) to 0. 33 g was obtained. (Yield 6%)
As a film forming method, a spin coating method, a dipping method, an ultrasonic method, or the like can be selected. The optimum method varies depending on R ₁ , R ₂ , R _3, Y, and the like responsible for bonding with the electron injecting metal oxide layer 6, but the optimum method capable of forming a monomolecular layer is selected.
Although not particularly required in this structure, a sealing material generally used can be used as a constituent material of the sealing structure. For example, Al, Au, Cr, Nb, Ta, Ti or alloys containing these, silicon oxide, various resin materials, and the like can be given.

  Such a light emitting element 1 can be manufactured as follows, for example.

  Below, the case where the organic compound layer 4 comprises a high molecular material as a main material is demonstrated as a representative.

  [1] First, the substrate 2 is prepared, and the cathode 3 is formed on the substrate 2.

  The cathode 3 may be, for example, a chemical vapor deposition method (CVD) such as plasma CVD, thermal CVD, or laser CVD, a dry plating method such as vacuum deposition, sputtering, or ion plating, a vapor deposition method such as a thermal spraying method, or an electrolytic plating. It can be formed using a wet plating method such as immersion plating or electroless plating, a liquid phase film forming method such as a sol-gel method or a MOD method, or a metal foil bonding. FTO is difficult to sputtering, and CVD or spray pyrolysis is used.

  [2] Next, after cleaning the cathode 3, an electron injecting metal oxide layer 6 is formed.

  As the cleaning method, an aqueous solvent using a neutral detergent, an alcohol solvent such as isopropanol, an organic solvent such as acetone, heating, cleaning using UV ozone, or the like can be used alone or in combination. The electron injecting metal oxide layer 6 can be formed by using, for example, the above-described vapor deposition method or liquid deposition method.

  [3] Next, after cleaning the upper surface of the electron injecting metal oxide layer 6, a self-assembled monolayer 8 is formed. The cleaning method is the same as [2]. Among them, UV ozone cleaning is publicly used to satisfactorily form a self-assembled monolayer. The self-assembled monolayer material is prepared by diluting the general formula (1) with an alcohol polar organic solvent, forming the film by a film formation method such as spin coating, rinsing with the dilution solvent, and further ultrasonicating with the same dilution solvent. Wash. Then, the self-assembled monolayer 8 is formed through an immobilization process by heating at 60 ° C. to 180 ° C.

  [4] Next, a light-emitting polymer material is formed as the organic compound layer 4 on the upper surface of the self-assembled monolayer 8. Of course, it is possible to mix a hole transporting material in this, and it is also possible to form a layer in which a light-emitting polymer material is first formed and a hole transporting material is formed thereon. Here, an example of single-layer film formation is shown. Lamination can be achieved by repeating this.

  First, the polymer material constituting the organic compound layer 4 is dissolved in a solvent (liquid medium) to prepare a liquid material.

  Examples of the solvent include inorganic solvents such as nitric acid, sulfuric acid, ammonia, hydrogen peroxide, water, carbon disulfide, carbon tetrachloride, ethylene carbonate, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK). , Ketone solvents such as methyl isopropyl ketone (MIPK) and cyclohexanone, alcohol solvents such as methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol (DEG) and glycerin, diethyl ether, diisopropyl ether, 1,2-dimethoxyethane (DME) ), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), diethylene glycol ethyl ether Ether solvents such as carbitol), cellosolv solvents such as methyl cellosolve, ethyl cellosolve and phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane and cyclohexane, and aromatic hydrocarbons such as toluene, xylene and benzene. Solvent, aromatic heterocyclic compound solvent such as pyridine, pyrazine, furan, pyrrole, thiophene, methylpyrrolidone, amide solvent such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), Halogen compound solvents such as chlorobenzene, dichloromethane, chloroform, 1,2-dichloroethane, ester solvents such as ethyl acetate, methyl acetate, ethyl formate, sulfur compound solvents such as dimethyl sulfoxide (DMSO), sulfolane, acetonitrile, propio Tolyl, nitriles such as acrylonitrile, formic acid, acetic acid, trichloroacetic acid, various organic solvents such as an organic acid solvents such as trifluoroacetic acid, or mixed solvents containing them.

  Among these, as the solvent, a nonpolar solvent is suitable, for example, an aromatic hydrocarbon solvent such as xylene, toluene, cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, tetramethylbenzene, pyridine, pyrazine, furan, Examples include aromatic heterocyclic compound solvents such as pyrrole, thiophene, and methylpyrrolidone, and aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane. These can be used alone or in combination.

  Next, this liquid material is supplied onto the electron injecting metal oxide layer 6 to form a liquid film.

  Examples of the method for supplying the liquid material include spin coating, casting, micro gravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, and screen printing. Various coating methods such as a printing method, a flexographic printing method, an offset printing method, and an inkjet printing method can be used. According to such a coating method, a liquid film can be formed relatively easily.

  Next, the solvent is removed from the liquid film.

  [5] Next, the hole injecting metal oxide layer 7 is formed on the organic compound layer 4.

  The hole injecting metal oxide layer 7 can be formed using, for example, the vapor phase film formation method or the liquid phase film formation method as described above.

  Among these, the hole injecting metal oxide layer 7 is more preferably formed using a vapor phase film forming method. According to the vapor deposition method, the organic compound layer 4 can be formed cleanly and in good contact with the anode 5 without breaking the surface, and as a result, the above-described effects become more remarkable.

  [6] Next, the anode 5 is formed on the hole injecting metal oxide layer 7 as a final step.

  The anode 5 can be formed using, for example, a vacuum deposition method, a sputtering method, a metal foil bonding, or the like.

  This structure is completed, but if it is to be performed, a sealing step may be performed thereafter.

  The light emitting element 1 of the present invention is manufactured through the above steps.

Such a light emitting element 1 can be used as, for example, a light source.
(Embodiment 2)
Since the basic mode and many manufacturing methods are the same as those in the first embodiment, the method for manufacturing the light-emitting element 11 is different from that in the first embodiment in the case where the organic compound layer 4 is formed of a high molecular material as a main material. An example is illustrated with a portion at the center.

  [1] First, the substrate 2 is prepared, and the anode 5 is formed on the substrate 2.

  For the anode 5, the same film forming method as described in Embodiment 1 [1] can be used.

  [2] Next, the hole injection / transport layer 17 is formed on the anode 5.

  As a material for forming the hole injection / transport layer 17, in particular, a dispersion of 3,4-polyethylenediosithiophene / polystyrene sulfonic acid (PEDOT / PSS), that is, 3,4-polyethylenedioxythiophene is added to polystyrene sulfonic acid. A dispersion obtained by mixing and further dispersing in water is preferably used.

  The material for forming the hole injection / transport layer 17 is not limited to the above, and various materials can be used. For example, a material obtained by dispersing polystyrene, polypyrrole, polyaniline, polyacetylene or a derivative thereof in an appropriate dispersion medium such as the aforementioned polystyrene sulfonic acid can be used.

  [3] Next, the self-assembled monolayer 8 is formed on the upper surface of the hole injection / transport layer 17. Unlike Embodiment 1, only UV ozone cleaning is performed, and an environment in which the self-assembled monolayer 8 is easily formed is prepared. Since many of the hole injection / transport layers 17 are also soluble in polar solvents (aqueous and alcoholic solvents), the diluted solvent of the self-assembled monolayer material is diluted with a nonpolar solvent and rinsed with the same nonpolar solvent. Is used. Other steps are the same as those in the first embodiment [3].

  [4] Same as Embodiment 1 [4].

  [5] Next, the cathode 3 is formed on the organic compound layer 4.

  The cathode 3 can be formed using, for example, a vacuum evaporation method, a sputtering method, a metal foil bonding, or the like. For the cathode, a metal having a small work function (4 eV or less) that is not used in the first embodiment is preferably used.

  This structure is completed, but if it is to be performed, a sealing step may be performed thereafter.

  The light emitting element 11 of the present invention is manufactured through the above steps.

  Such a light emitting element 11 can be used as, for example, a light source.

  Next, specific examples of the present invention will be described.

1. Production of light emitting device (Example 1)
A method for manufacturing the organic-inorganic hybrid thin film electroluminescent element of Embodiment 1 having a polymer material in the organic layer will be specifically described.
[1] A commercially available transparent glass substrate with ITO having an average thickness of 0.7 mm was prepared.
[2] A titanium oxide (TiO ₂ ) layer (electron-injecting metal oxide layer) having an average thickness of 2 nm was formed on the ITO electrode by sputtering.
[3]

A solution was prepared by diluting the self-assembled monomolecular material F8TES obtained in 1 to 1% with ethanol. The substrate obtained in [2] was washed with isopropanol and acetone, followed by UV ozone cleaning for 20 minutes, and the 1% solution was formed into a film by spin coating (2000 rpm). Immediately after that, rinsing with ethanol was performed, and ultrasonic cleaning with ethanol was further performed for 10 minutes. After rinsing, immobilization was performed at 90 ° C. for 10 minutes using a hot plate.
[4] A polyfluorene derivative ADS133YE manufactured by ADS was dissolved in xylene at 1%, applied onto the TiO ₂ layer (electron-injecting metal oxide layer) by a spin coating method (1000 rpm), and then dried. The drying condition of the liquid material was room temperature in the atmosphere. This completes the organic compound layer.
[5] The production of the hole injecting metal oxide layer and the production process of the anode are carried out in a vacuum vapor deposition machine. Here, a molybdenum oxide (MoO ₃ ) layer (hole-injecting metal oxide layer) was deposited on the organic compound layer with an average thickness of 10 nm.
[6] In the continuous process of [5], gold (Au) (anode) was vapor-deposited with an average thickness of 30 nm.

(Example 2)
[1] A method for producing the polymer organic thin film electroluminescent device of the second embodiment will be specifically described.
A commercially available transparent glass substrate with ITO having an average thickness of 0.7 mm was prepared.
[2] After the substrate of [1] is cleaned with UV ozone for 20 minutes, H.V. is a polythiophene derivative as a hole injection / transport material on the substrate. C. PEDOT: PSS manufactured by Starck Co., Ltd. was applied. Here, Baytron P AI4083 was used to form a film by spin coating (2000 rpm). This was formed into a film by baking at 200 ° C. for 10 minutes in the atmosphere to form the hole injection / transport layer 17.
[3] Self-assembled monomolecular material B8TES

A solution was prepared by diluting 1% with ethanol. The substrate on which the hole injecting / transporting layer obtained in [2] was formed was subjected to UV ozone cleaning for 20 minutes, and then the 1% solution was formed by spin coating (2000 rpm). Immediately after that, rinsing with toluene was performed, followed by ultrasonic cleaning with toluene for 10 minutes. After rinsing, immobilization was performed at 90 ° C. for 10 minutes using a hot plate.
[4] A polyfluorene derivative ADS133YE manufactured by ADS was dissolved in xylene at 1%, applied onto the TiO ₂ layer (electron-injecting metal oxide layer) by a spin coating method (1000 rpm), and then dried. The drying condition of the liquid material was room temperature in the atmosphere. This completes the organic compound layer.
[5] The cathode fabrication process is performed in a vacuum vapor deposition machine. Aluminum having an average thickness of 10 nm was deposited on the organic compound layer, and aluminum having an average thickness of 200 nm was deposited as a continuous process.
(Comparative Example 1-1)
The process example 1 [3] is changed to the process [3-2] below. Other than that produced the light emitting element similarly to Example 1. FIG. That is, an organic-inorganic hybrid thin film electroluminescent device having a self-assembled monomolecular film having polarization in the molecule was manufactured.
[3-2] Aminopropyltrimethoxysilane (APTMS) manufactured by Shin-Etsu Chemical Co., Ltd. is used as a self-assembled monolayer material.
A solution was prepared by diluting the self-assembled monomolecular material APTMS with methanol to 1%. The substrate obtained in [2] was washed with isopropanol and acetone, followed by UV ozone cleaning for 20 minutes, and a film was formed by immersion for 1 minute in the 1% solution. Immediately after that, rinsing with methanol was performed, and ultrasonic cleaning with methanol was further performed for 10 minutes. After rinsing, immobilization was performed at 90 ° C. for 10 minutes using a hot plate.

(Comparative Example 1-2)
A light emitting device was produced in the same manner as in Example 1 except that Step 1 [3] was omitted. That is, an organic-inorganic hybrid thin film electroluminescent device without only a self-assembled monolayer was manufactured.

(Comparative Example 2)
A light emitting device was produced in the same manner as in Example 2 except that Step 2 [3] was omitted. That is, a polymer organic thin film electroluminescent device having no self-assembled monolayer.

2. Evaluation The light emitting devices manufactured in each of Examples and Comparative Examples were evaluated for initial luminance and current half-life under constant voltage driving.

  The luminance measurement was performed by applying a voltage from 0 V to 4 V with a DC power source and measuring with a luminance meter.

Further, from the results of non-patent literature (J. Am. Chem. Soc. 127, 10227, 2005) and the like, it is assumed that the energy level of a self-assembled monolayer can be approximated by the value of its functional group. The F8TES in 1 will have a HOMO of 5.7 eV and a LUMO of 2.8 eV. Moreover, the HOMO of B8TES in Example 2 is 6.7 eV, and the LUMO is 3.8 eV. The organic compound F8BT used this time has a HOMO of 5.9 eV and a LUMO of 3.3 eV. From the viewpoint of electrons, which are the main carriers in Example 1, there is a 1.4 eV energy barrier from TiO ₂ having a CB of 4.2 eV to the self-assembled monolayer F8TES, while the positive carrier, which is the opposite carrier, is present. In the hole, there is no energy barrier from F8BT to F8TES. Similarly, from the hole which is the main carrier in Example 2, there is an energy barrier from PEODT: HOS of PSS (5.1 eV) to HOMO of B8TES to 1.6 eV, while it is the opposite carrier. In electrons, carrier injection without an energy barrier is possible from F8BT to B8TES. Moreover, since APTMS used in Comparative Example 1-1 is an insulator, it is considered that there is a large energy barrier for both electrons and holes. These three self-assembled monolayer materials all have a molecular chain length of 2 nm or less. Normally, assuming a carrier injection mechanism by tunneling, 2 nm or less is considered good, and from this, main carriers are injected well.

  The results are shown in FIGS.

4 and 6 show the initial characteristics (voltage-luminance) of each example and comparative example. It can be seen that each of the light emitting elements of each example exhibits the same or higher luminance than the light emitting element of the comparative example. This indicates that charge injection is performed well and quenching is reduced. This indicates that the self-assembled monolayer has an effect on the initial characteristics (luminance). In the initial characteristics, it can be seen that the self-assembled monolayer APTMS having an energy barrier also shows the same effect in the main carrier that does not show cation stability and in the opposite carrier shown in Comparative Example 1-1. Although not shown here, the values of current density were almost the same in each example and each comparative example. Therefore, the magnitude of the luminance shows the magnitude of the efficiency as it is, and the self-assembled monolayer is efficient. It was also shown that it works effectively.
5 and 7 show the life characteristics (time-current) of each example and each comparative example. Each of the light-emitting elements in each example is shown to be excellent in long-term stability as compared with all corresponding light-emitting elements of comparative examples. More specifically, since the horizontal axis is a logarithmic display, it was shown that there was an improvement effect over several digits. What is interesting is that when Example 1 and Comparative Example 1-1 were compared, there was a large difference in long-term stability even though the initial characteristics were equivalent. This indicates that a self-assembled monolayer that does not belong to this concept has no effect on the device lifetime. Further, in reality, the lifetime characteristics are worse than those of Comparative Example 1-2 that does not include a self-assembled monolayer, and the self-assembled monolayer promotes deterioration.
The mechanism of these results will be described using Example 1 and Comparative Examples 1-1 and 1-2 as examples.
The driving mechanism of this device is that holes are accumulated at the electron-injecting metal oxide layer / organic compound layer interface, and electrons are injected to emit light (see Non-Patent Document 4). For this reason, at the interface described above, the radicalized organic compound is in direct contact with the metal oxide layer, and chemical degradation there cannot be ignored. As a result, deteriorated substances having no bonds are accumulated on the metal oxide layer, which inhibits carrier injection and causes further deterioration. This is the deterioration mechanism of Comparative Example 1-2 that does not have a self-assembled monolayer. In the present invention, a self-assembled monolayer was inserted into this interface. Holes are similarly accumulated at the electron injecting metal oxide layer / organic compound layer interface. In Example 1, since there is no energy barrier, holes move smoothly on the self-assembled monolayer and still exist stably. In addition, due to the presence of the anchor portion (Si—O—), a situation in which the metal oxide layer does not directly contact can be realized. Since the distance is about 1 nm, there is no hindrance to electron injection. As a result, we believe that long-term stability has been achieved. On the other hand, in Comparative Example 1-1, holes are not easily injected into the self-assembled monolayer due to the existence of an energy barrier. However, since APTMS itself has a dipole, electron injection using it is promoted, and the initial characteristics are improved as compared with Comparative Example 1-2. However, the organic compound or the hole-injected self-assembled monolayer itself at the interface of the self-assembled monolayer / organic compound layer is radicalized and causes chemical degradation, which inhibits carrier injection and causes further degradation. I guess it has become. Originally, since APTMS has a strong dipole, it is considered that deterioration is promoted more than Comparative Example 1-2, which has nothing.
These results provide an effective technique for deterioration at the interface, which is one problem in thin film devices. Conventional degradation mitigation methods have been developed to reduce the interface as much as possible. However, the use of the interface is also an essential advantage of the thin film device, and the present situation is that the element characteristics are often deteriorated. This method provides a method of maintaining the characteristics, strengthening the interface, which is one of the deterioration factors, by chemical bonding, and maintaining the deposited carriers stably for a long period of time. As a result, long-term stability of the thin film device was realized. For the reasons as described above, it is considered that the technology can be generally used for thin film devices having the same deterioration mechanism.

  DESCRIPTION OF SYMBOLS 1 ... Organic-inorganic hybrid type thin film electroluminescent element 2 ... Substrate 3 ... Cathode 4 ... Organic compound layer 5 ... Anode 6 ... Electron injection metal oxide layer 7 ... Hole injection metal oxide layer 8 …… Self-assembled monolayer 11 …… Polymer organic thin film electroluminescent device 17 …… Hole injection / transport layer

Claims (5)

An anode and a cathode on the substrate; and one or more organic compound layers sandwiched between the anode and the cathode; and an electron injecting metal oxide layer on the cathode on the substrate the a, adjacent to the electronic injection metal oxide layer becomes an energy barrier for electrons, have a self-assembled monolayer that do not energy barrier for holes, to the self-assembled monolayer on The organic compound layer is adjacent to the organic compound layer provided adjacent to the highest occupied orbital or the highest energy level of the valence band is the highest occupied orbital or valence of the electron injecting metal oxide layer. An organic thin film electroluminescent device characterized by being higher than the highest energy level of the electron band . 2. The organic thin film electroluminescent device according to claim 1, wherein the metal oxide thin film forming the electron injecting metal oxide layer includes a titanium oxide thin film. A self-assembled monomolecular film provided in the organic thin film electroluminescent device according to claim 1 or 2 is obtained from a compound represented by the following general formula (1): Materials.

In the formula, R ₁ , R ₂ and R ₃ are alkoxyl groups or halogen atoms, X is a linking group, and Y is a functional group. Y represents a functional group in which a radical cation is a stable structure at an interface where the main carrier is an electron, and a radical anion is a stable structure at an interface where the main carrier is a hole. The self-assembled monolayer material according to claim 3, wherein the molecular chain length of Si-XY of the self-assembled monolayer material is 2 nm or less. An illuminating device comprising the organic thin film electroluminescent element according to claim 1.

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