JP2008263112A - Organic light-emitting device using dibenzofluoranthene derivative - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light-emitting device capable of ensuring very high efficient and luminous optical output and high durability. <P>SOLUTION: The organic light-emitting device comprises a positive electrode and a negative electrode, as well as an organic compound layer sandwiched between the positive electrode and the negative electrode. The layer comprising the organic compound contains at least one kind of dibenzofluoranthene derivatives represented by formula [I] (in the formula, R<SB>1</SB>to R<SB>14</SB>are each independently a hydrogen atom, an alkyl group, a straight chain or branched alkoxy group, a substituted or non-substituted aryl group, a substituted or non-substituted heterocyclic group, a substituted amino group, or a halogen atom). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic light emitting device, and more particularly to an organic light emitting device using a dibenzofluoranthene derivative.

  An organic light-emitting element is an element in which a thin film containing a fluorescent organic compound or a phosphorescent organic compound is sandwiched between an anode and a cathode. Further, by injecting electrons and holes (holes) from each electrode to generate excitons of a fluorescent compound or a phosphorescent compound, the organic light emitting device emits light when the excitons return to the ground state. .

  Furthermore, the organic light emitting element can emit light from ultraviolet to infrared by changing the type of the fluorescent organic compound. Recently, various fluorescent organic compounds have been actively researched. Specific examples include Patent Documents 1 to 5 and the like.

  Recent advances in organic light-emitting devices are remarkable, and their features include high brightness, a wide variety of emission wavelengths, high-speed response, and reduction in thickness and weight of light-emitting devices with a low applied voltage. From this, the organic light emitting element has suggested the possibility to a wide use.

  However, under the present circumstances, light output with higher brightness or higher conversion efficiency is required. In addition, there are still many problems in terms of durability, such as changes over time due to long-term use and deterioration due to atmospheric gas containing oxygen or moisture. Furthermore, it is necessary to emit blue, green, and red light with good color purity when considering application to a full-color display or the like, but these problems have not been sufficiently solved.

  By the way, a compound having a fluoranthene skeleton has been proposed and studied as a material for an organic light emitting device. Specific examples include Patent Document 6, Patent Document 7, and the like.

US Pat. No. 5,151,629 US Pat. No. 5,409,783 US Pat. No. 5,382,477 JP-A-9-202878 JP-A-9-227576 Japanese Patent Laid-Open No. 10-189247 Japanese Patent Laid-Open No. 10-189248

  An object of the present invention is to provide an organic light emitting device having extremely high efficiency and high luminance light output and having extremely high durability. Another object of the present invention is to provide an organic light emitting device that is easy to manufacture and can be manufactured at a relatively low cost.

  The organic light-emitting device of the present invention comprises an anode, a cathode, and a layer made of an organic compound sandwiched between the anode and the cathode. The layer made of the organic compound is represented by the following general formula [I]. It contains at least one dibenzofluoranthene derivative.

(Wherein R _{1 to} R ₁₄ each represents a hydrogen atom, an alkyl group, a linear or branched alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted amino group or a halogen atom, respectively. To express.)

  According to the present invention, it is possible to provide an organic light emitting device that has extremely high efficiency and high luminance light output and is extremely durable. The organic light-emitting device of the present invention can realize high-efficiency light emission by using a dibenzofluoranthene derivative in a layer made of an organic compound, preferably a light-emitting layer. In addition, the organic light-emitting device of the present invention is an excellent organic light-emitting device because it maintains a high luminance for a longer period than a conventional organic light-emitting device using a compound.

  The organic light emitting device of the present invention includes an anode, a cathode, and a layer made of an organic compound sandwiched between the anode and the cathode. The organic light emitting device of the present invention preferably emits light by applying a voltage to the anode and the cathode.

  Hereinafter, the organic light emitting device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a first embodiment of the organic light-emitting device of the present invention. In the organic light emitting device 10 of FIG. 1, an anode 2, a light emitting layer 3, and a cathode 4 are sequentially provided on a substrate 1. This organic light emitting device 10 is useful when the light emitting layer 3 is composed of an organic compound having all of hole transport ability, electron transport ability, and light emitting performance. Moreover, it is useful also when the light emitting layer 3 is comprised by mixing the organic compound which has the characteristics in any one of hole transport ability, electron transport ability, and luminescent property.

  FIG. 2 is a cross-sectional view showing a second embodiment of the organic light emitting device of the present invention. In the organic light emitting device 20 of FIG. 2, an anode 2, a hole transport layer 5, an electron transport layer 6 and a cathode 4 are sequentially provided on a substrate 1. This organic light emitting device 20 is useful when a light emitting organic compound having either hole transporting property or electron transporting property and an organic compound having only electron transporting property or only hole transporting property are used in combination. In the organic light emitting device 20, the hole transport layer 5 or the electron transport layer 6 also serves as the light emitting layer.

  FIG. 3 is a cross-sectional view showing a third embodiment of the organic light-emitting device of the present invention. An organic light emitting device 30 in FIG. 3 is obtained by inserting the light emitting layer 3 between the hole transport layer 5 and the electron transport layer 6 in the organic light emitting device 20 in FIG. The organic light emitting device 30 has functions of separating carrier transport and light emission, and organic compounds having hole transport property, electron transport property, and light emission property can be used in appropriate combination. For this reason, the degree of freedom of material selection is greatly increased, and various organic compounds having different emission wavelengths can be used, so that the emission hue can be diversified. Furthermore, it becomes possible to effectively confine carriers or excitons in the central light emitting layer 3 to improve the light emission efficiency of the organic light emitting element 30.

  FIG. 4 is a cross-sectional view showing a fourth embodiment of the organic light emitting device of the present invention. An organic light emitting device 40 in FIG. 4 is obtained by providing a hole injection layer 7 between the anode 2 and the hole transport layer 5 in the organic light emitting device 30 in FIG. 3. The organic light emitting device 40 is effective in lowering the voltage because the adhesion between the anode 2 and the hole transport layer 5 or the hole injection property is improved by providing the hole injection layer 7.

  FIG. 5 is a cross-sectional view showing a fifth embodiment of the organic light-emitting device of the present invention. The organic light emitting device 50 in FIG. 5 is different from the organic light emitting device 30 in FIG. 3 in that the layer (hole / exciton blocking layer 8) that prevents holes or excitons (excitons) from passing to the cathode 4 side is It is inserted between the electron transport layer 6. By using an organic compound having a very high ionization potential as the hole / exciton blocking layer 8, the light emission efficiency of the organic light emitting device 50 is improved.

  FIG. 6 is a cross-sectional view showing a sixth embodiment of the organic light emitting device of the present invention. An organic light emitting device 60 of FIG. 6 is obtained by inserting a hole / exciton blocking layer 8 between the light emitting layer 3 and the electron transport layer 6 in the organic light emitting device 40 of FIG. By using an organic compound having a very high ionization potential as the hole / exciton blocking layer 8, the light emission efficiency of the organic light emitting device 60 is improved.

  However, FIGS. 1 to 6 are very basic device configurations, and the configuration of the organic light-emitting device of the present invention is not limited thereto. For example, an insulating layer, an adhesive layer, or an interference layer may be provided at the interface between the electrode and the organic layer. Moreover, the hole transport layer 5 may be composed of two layers having different ionization potentials. Further, an electron barrier layer or the like may be provided as necessary.

  The organic light-emitting device of the present invention is characterized in that the layer made of an organic compound contains at least one dibenzofluoranthene derivative represented by the following general formula [I].

In the formula [I], R _{1 to} R ₁₄ are each a hydrogen atom, an alkyl group, a linear or branched alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted amino group, or a halogen. Represents an atom.

Examples of the alkyl group represented by R _{1 to} R ₁₄ include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a tertiary butyl group, an octyl group, and a cyclohexyl group. At this time, a hydrogen atom in the alkyl group may be substituted with a fluorine atom to form, for example, a trifluoromethyl group.

Examples of the alkoxy group represented by R _{1 to} R ₁₄ include a methoxy group, an ethoxy group, and a tertiary butyloxy group. At this time, a hydrogen atom in the alkoxy group may be substituted with a fluorine atom, for example, a trifluoromethyloxy group.

As aryl groups represented by R _{1 to} R ₁₄ , phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group, fluoranthenyl group, anthryl group, phenanthryl group, pyrenyl group, tetracenyl group, pentacenyl group, triphenylenyl Group, perylenyl group and the like.

The heterocyclic group represented by R ₁ to R _14, a thienyl group, a pyrrolyl group, a pyridyl group, oxazolyl group, oxadiazolyl group, thiazolyl group, thiadiazolyl group and the like.

Examples of the substituted amino group represented by R _{1 to} R ₁₄ include a dimethylamino group, a diethylamino group, a dibenzylamino group, a diphenylamino group, a ditolylamino group, and a dianisolylamino group.

Examples of the halogen atom represented by R _{1 to} R ₁₄ include fluorine, chlorine, bromine, and iodine.

  From the viewpoint of suppressing concentration quenching when used in an organic light emitting device, the aryl group and the heterocyclic group that may be substituted with the heterocyclic group include alkyl groups such as a methyl group, an ethyl group, and a propyl group, and a phenyl group. , Aryl groups such as biphenyl groups, heterocyclic groups such as thienyl groups, pyrrolyl groups, pyridyl groups, amino groups such as dimethylamino groups, diethylamino groups, dibenzylamino groups, diphenylamino groups, ditolylamino groups, dianisolylamino groups , Halogen atoms such as fluorine, chlorine, bromine and iodine.

  Hereinafter, specific structural formulas of dibenzofluoranthene derivatives are shown below. However, these are merely representative examples, and the present invention is not limited thereto.

  Examples of the layer made of an organic compound containing the dibenzofluoranthene derivative of the general formula [I] include, for example, the light emitting layer 3, the hole transport layer 5, the electron transport layer 6, and the hole injection layer shown in FIGS. 7 and a hole / exciton blocking layer 8. Of these layers, the dibenzofluoranthene derivative may be contained only in a single layer, or may be contained in a plurality of layers. In addition, the dibenzofluoranthene derivative contained in these layers may be one type or two or more types.

  The layer made of an organic compound containing a dibenzofluoranthene derivative is preferably the light emitting layer 3. Here, the light emitting layer 3 may be composed of only a dibenzofluoranthene derivative, but is preferably composed of a host and a guest. The dibenzofluoranthene derivative of the general formula [I] is preferably a host. Moreover, the guest here is a compound that emits light mainly in response to recombination of holes and electrons in the light emitting region of the organic light emitting device, and other compounds (hosts) that form the light emitting region. It is included.

  When the light emitting layer is composed of a carrier transporting host and guest, the main process leading to light emission consists of the following several processes.

(1) Electron / hole transport in the light-emitting layer (2) Exciton generation of the host (3) Excitation energy transfer between host molecules (4) Excitation energy transfer from host to guest Desired energy transfer in each process Luminescence occurs in various deactivation processes and competition.

  Needless to say, in order to increase the light emission efficiency of the organic light emitting device, the emission quantum yield of the light emission center material itself is increased. However, how to efficiently transfer energy between the host and the host or between the host and the guest is also a big problem. Further, although the cause of the deterioration of light emission due to energization is not clear at present, it is assumed that it is related to the environmental change of the light emitting material due to at least the luminescent center material itself or its surrounding molecules.

  Here, when the dibenzofluoranthene derivative represented by the general formula [I] is used as a host or guest of the light emitting layer, the light emitting efficiency of the organic light emitting device is improved, high luminance is maintained for a long period, and current deterioration is reduced. Can do.

  When the dibenzofluoranthene derivative represented by the general formula [I] is used as a guest, the content thereof is preferably 50% by weight or less based on the total weight of the light emitting layer. More preferably, it is 0.1 to 30% by weight. Particularly preferred is 0.1 to 15% by weight.

  On the other hand, when the dibenzofluoranthene derivative represented by the general formula [I] is used as a host, the guest is not particularly limited, and the compounds described below can be appropriately used depending on the desired emission color. In addition to the guest, if necessary, a hole transporting compound, an electron transporting compound and the like can be doped together and used.

  Next, other constituent members constituting the organic light emitting device of the present invention will be described.

  The organic light emitting device of the present invention uses a dibenzofluoranthene derivative represented by the general formula [I] as a constituent material of an organic compound, preferably a light emitting layer. Moreover, as a material which comprises the layer which consists of organic compounds, a well-known hole transport compound, a luminescent compound, an electron transport compound etc. can be used together as needed.

  Examples of these compounds are given below.

  The anode material should have a work function as large as possible. For example, a metal simple substance such as gold, platinum, nickel, palladium, cobalt, selenium, vanadium or an alloy thereof, or a metal oxide such as tin oxide, zinc oxide, indium tin oxide (ITO), or zinc indium oxide can be used. In addition, conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene sulfide can also be used. These electrode materials may be used alone or in combination.

  On the other hand, a cathode material having a small work function is preferable. For example, a single metal such as lithium, sodium, potassium, cesium, calcium, magnesium, aluminum, indium, silver, lead, tin, chromium, or an alloy in which a plurality of these metals are combined can be used. It is also possible to use a metal oxide such as indium tin oxide (ITO). Moreover, the cathode may be composed of a single layer or a plurality of layers.

  Although it does not specifically limit as a board | substrate used with the organic light emitting element of this invention, Transparent substrates, such as opaque board | substrates, such as a metal board | substrate and a ceramic board | substrate, glass, quartz, a plastic sheet, are used. It is also possible to control the color light by using a color filter film, a fluorescent color conversion filter film, a dielectric reflection film or the like on the substrate.

  In addition, a protective layer or a sealing layer can be provided for the purpose of preventing contact with oxygen, moisture, or the like on the manufactured element. Examples of the protective layer include inorganic material films such as diamond thin films, metal oxides, and metal nitrides, polymer films such as fluorine resins, polyparaxylene, polyethylene, silicone resins, and polystyrene resins, and photocurable resins. It is done. Alternatively, the device itself can be packaged with an appropriate sealing resin by covering the device with glass, a gas-impermeable film, metal, or the like.

  In the organic light-emitting device of the present invention, the layer containing the dibenzofluoranthene compound represented by the general formula [I] and the layer containing another organic compound are generally constituted by a vacuum deposition method or an appropriate solvent. A thin film is formed by an application method in which a member to be dissolved is applied. In particular, when a film is formed by a coating method, the film can be formed in combination with an appropriate binder resin.

  The binder resin can be selected from a wide range of binder resins such as polyvinyl carbazole resin, polycarbonate resin, polyester resin, polyarylate resin, polystyrene resin, acrylic resin, methacrylic resin, butyral resin, polyvinyl acetal resin, diallyl phthalate resin. , Phenol resin, epoxy resin, silicone resin, polysulfone resin, urea resin and the like, but are not limited thereto. Moreover, you may mix these 1 type, or 2 or more types as a single or copolymer polymer.

  In the organic light-emitting device of the present invention, the thickness of the layer containing the dibenzofluoranthene derivative represented by the general formula [I] is preferably less than 10 μm, more preferably 0.5 μm or less, still more preferably 0.8 μm. It is 01 μm to 0.5 μm.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Synthesis example 1
[Exemplary Compound No. Synthesis of A-2]

  Under a nitrogen atmosphere, 165 ml (0.165 mol) of a 1 mol / l tetrahydrofuran solution of p-tolylmagnesium bromide represented by the above formula (2) was added to a 300 ml reaction vessel and cooled to 0 ° C. Next, to this solution, 7.5 g (0.0412 mol) of acenaphthenequinone represented by the above formula (1) was added little by little over 30 minutes, and then the temperature was raised to 30 ° C. and stirred at this temperature for 24 hours. did.

  After completion of the reaction, 10% sulfuric acid was added to make it acidic. Next, 1.5 L of distilled water was added and extracted with ethyl acetate (3 × 500 mL). The extracted organic layers were combined, washed sequentially with saturated aqueous sodium hydrogen carbonate and saturated brine, and dried over anhydrous magnesium sulfate. Next, the desiccant was filtered off and the solution was concentrated under reduced pressure to obtain a crude product as a yellow solid. The crude product was purified by silica gel column column chromatography (developing solvent: hexane / ethyl acetate = 10/1) to obtain 13.2 g of intermediate (3) (yield = 87.4%).

  Under a nitrogen atmosphere, 236 ml of trifluoromethanesulfonic acid and 11.8 g (32.2 mmol) of intermediate (3) were added to a 500 ml reaction vessel, and the mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction solution was poured onto ice (600 g), and the organic layer was extracted with toluene (500 mL × 4 times). The extracted organic layers were combined, washed sequentially with distilled water and saturated brine, and dried over anhydrous magnesium sulfate. The desiccant was filtered off, and the solution was concentrated under reduced pressure to obtain 7.03 g of a crude product as a yellow solid. By recrystallizing 1.00 g of the obtained solid from toluene, 0.60 g (1.8 mmol, yield = 39%) of yellow solid A-2 was obtained.

The structure of A-2 was confirmed by ¹ H-NMR measurement.

¹ H-NMR (CDCl ₃ , 500 MHz) σ (ppm): 8.77 (d, 2H, J = 8 Hz), 8.56 (s, 2H), 8.50 (d, 2H, J = 7 Hz), 7.85 (d, 2H, J = 8 Hz), 7.68 (t, 2H, J = 7 Hz), 7.55 (d, 2H, J = 8 Hz), 2.67 (s, 6H).

Example 1
On the glass substrate, indium tin oxide (ITO) was formed as an anode with a film thickness of 120 nm by a sputtering method. This was ultrasonically washed successively with acetone and isopropyl alcohol (IPA), then boiled and washed with IPA and then dried. Further, UV / ozone cleaning was performed. The substrate thus treated was used as a transparent conductive support substrate.

  Next, a chloroform solution of Compound 1 represented by the following formula was formed on this transparent conductive support substrate with a film thickness of 20 nm by a spin coating method to form a hole transport layer.

Next, another organic layer and an electrode layer forming a cathode were continuously formed by vacuum deposition by resistance heating in a vacuum chamber of 10 ⁻⁵ Pa to produce an organic light emitting device.

  Specifically, as the light emitting layer, exemplified compound No. 1 which is a guest is used. A-2 and compound 2 represented by the following formula, which is a host, were exemplified as Compound No. Co-evaporation was performed so that the content of A-2 was 5% by weight with respect to the total weight of the light emitting layer. At this time, the thickness of the light emitting layer was set to 20 nm. Next, Bphen (manufactured by Dojin Chemical Laboratories) was deposited as an electron transport layer with a film thickness of 30 nm. Next, LiF was vapor-deposited with a film thickness of 0.5 nm as the first metal electrode layer. Finally, Al was deposited as a second metal electrode layer with a film thickness of 150 nm. In this way, an organic light emitting device was produced.

  The characteristics of the obtained organic light emitting device were evaluated. About the current-voltage characteristic, it measured by Hured Packard company * microammeter 4140B. Further, the emission luminance was measured with BM7 manufactured by Topcon Corporation. In the organic light emitting device of this example, good light emission was observed when a voltage was applied. Further, when a voltage was applied to the device under a nitrogen atmosphere for 100 hours, it was confirmed that the light emission continued well.

  As described above, the organic light emitting device using the compound represented by the general formula [I] as the guest of the light emitting layer can obtain good light emission and is excellent in durability.

  Furthermore, the organic light-emitting element can also be manufactured by using a vacuum deposition method, a casting method, or the like, and a relatively inexpensive and large-area element can be easily manufactured.

It is sectional drawing which shows 1st embodiment in the organic light emitting element of this invention. It is sectional drawing which shows 2nd embodiment in the organic light emitting element of this invention. It is sectional drawing which shows 3rd embodiment in the organic light emitting element of this invention. It is sectional drawing which shows 4th embodiment in the organic light emitting element of this invention. It is sectional drawing which shows 5th embodiment in the organic light emitting element of this invention. It is sectional drawing which shows 6th embodiment in the organic light emitting element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Light emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer 7 Hole injection layer 8 Hole / exciton blocking layer 10, 20, 30, 40, 50, 60 Organic light emitting device

Claims (3)

An anode and a cathode;
A layer made of an organic compound sandwiched between the anode and the cathode, and
The organic light-emitting device, wherein the layer made of the organic compound contains at least one dibenzofluoranthene derivative represented by the following general formula [I].

(Wherein R _{1 to} R ₁₄ each represents a hydrogen atom, an alkyl group, a linear or branched alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted amino group or a halogen atom, respectively. To express.)   The organic light-emitting element according to claim 1, wherein the layer made of the organic compound is a light-emitting layer.   The organic light emitting device according to claim 1, wherein the organic light emitting device emits light by applying a voltage between the anode and the cathode.

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