JP4835467B2 - ORGANIC LIGHT EMITTING ELEMENT AND MANUFACTURING METHOD THEREOF - Google Patents

Description

The present invention relates to an organic light emitting device and a method for manufacturing the same.

An organic light emitting element is an element containing an organic compound (organic light emitting material) that emits light by current injection from a pair of electrodes. The energy when the electrons supplied from the cathode and the holes supplied from the anode are recombined in the organic light emitting material is taken out as light.

Such an organic light emitting device has a light emitting layer containing at least an organic light emitting material between an anode and a cathode, as described in Non-Patent Document 1 by Tang et al. Of Eastman Kodak Company.

Here, since the difference between the lowest unoccupied molecular orbital (LUMO) level of organic compounds and the vacuum level is generally small, the cathode material and the organic light emitting material are used for electron injection from the cathode to the organic light emitting material. There is a big energy barrier between them.
As a measure to alleviate this energy barrier and increase the light emission efficiency of the light emitting device, it is made of a low work function metal such as an alkali metal or alkaline earth metal between the cathode and the light emitting layer using a vacuum deposition method. It has been proposed to insert an intermediate layer. [For example, Non-Patent Document 2]

In addition, a method has been proposed in which an intermediate layer made of a fluoride or oxide of these low work function metals is inserted between the cathode and the light emitting layer using a vacuum deposition method. [For example, Non-Patent Document 3]

In addition, by simultaneously vacuum-depositing an electron transporting organic molecule and a low work function metal such as an alkali metal (hereinafter referred to as co-evaporation), the low work function metal and the electron transporting organic molecule are disposed between the cathode and the light emitting layer. A method of inserting an intermediate layer including a layer has also been proposed. [For example, Patent Document 1]

Appl. Phys. Lett., 51 (1987) pp.913 J. Appl. Phys., 88 (2000) pp.3618 Appl. Phys. Lett., 70 (1997) pp.152 JP 10-270171

A vapor deposition method is used to form the intermediate layer in these conventional techniques.
However, the formation of the intermediate layer by vapor deposition requires a vacuum device that requires a high degree of vacuum, and there is a problem that a large and expensive device must be used.
Further, when manufacturing a large element, there is a problem that a large vacuum apparatus is required and the equipment cost becomes expensive.
Furthermore, in the formation of the intermediate layer by the vacuum vapor deposition apparatus, it takes time to obtain the required degree of vacuum, so that there is a problem that the processing capacity at the time of mass production is low.
An object of the present invention is to provide an organic light-emitting device that can easily form an intermediate layer under atmospheric pressure and has excellent luminous efficiency.

As a result of diligent research to solve the above problems, the present invention has been achieved.
That is, the present invention is an organic light emitting device having a light emitting layer between a cathode and an anode, and an intermediate layer in contact with the cathode between the light emitting layer and the cathode, wherein the intermediate layer is Provided is an organic light-emitting device comprising at least one metal complex selected from an alkali metal complex and an alkaline earth metal complex, and a polymer compound.
Further, the present invention includes a step of forming a film of the intermediate layer using a composition containing the polymer compound, a solvent, and one or more metal complexes selected from the alkali metal complexes and alkaline earth metal complexes. The manufacturing method of the said organic light emitting element containing is provided.

The organic light-emitting device of the present invention can be easily produced and has excellent luminous efficiency.

  The organic light-emitting device of the present invention is an organic light-emitting device having a light-emitting layer between a cathode and an anode, and an intermediate layer in contact with the cathode between the light-emitting layer and the cathode, the intermediate layer Is an organic light emitting device comprising one or more metal complexes selected from alkali metal complexes and alkaline earth metal complexes, and a polymer compound.

As the layer structure of the organic light emitting device of the present invention,
Anode / light emitting layer / intermediate layer / cathode anode / hole injection layer / light emitting layer / intermediate layer / cathode anode / hole injection layer / light emitting layer / intermediate layer / cathode anode / light emitting layer / electron transport layer / intermediate layer / cathode Anode / hole injection layer / light emitting layer / electron transport layer / intermediate layer / cathode and the like.

Examples of the alkali metal complex and alkaline earth metal complex contained in the intermediate layer in contact with the cathode of the organic light emitting device of the present invention include metal complexes with diketone compounds, pyridine metal complexes, quinolinol metal complexes, and the like. The metal complex is preferred. Among metal complexes with diketone compounds, acetylacetonate metal complexes (where the metal complex ligand is acetylacetonate) are more preferred.
As the acetylacetonate metal complex, an alkali metal complex (for example, lithium / acetylacetonate, sodium / acetylacetonate) or an alkaline earth metal complex (for example, barium / acetylacetonate, calcium / acetylacetonate) is used. However, lithium acetylacetonate is more preferable from the viewpoint of electron injection performance.

The polymer compound contained in the intermediate layer in contact with the cathode of the organic light-emitting device of the present invention is preferably a conductive polymer, and polyphenylene vinylene polymer compounds, polyfluorene polymer compounds, and the like can be used. Preferred are polyfluorene polymers such as (2,7-9,9 di-n-octyl fluorenediyl) (2,7-9,9 diisoamyl fluorenediyl) copolymer compound.

The polymer compound having a weight average molecular weight of usually 10,000 to 1,000,000 can be used, but about 100,000 to 500,000 is preferable from the viewpoint of solubility.

  When the total weight of the layers in contact with the cathode is 100% by weight, the weight of the metal complex is usually 5% by weight to 50% by weight, and preferably 10% by weight to 30% by weight.

The light emitting layer of the organic light emitting device of the present invention can inject holes from the anode or the hole injection layer when an electric field is applied, and can inject electrons from the cathode or the electron injection layer. It has a function of moving electrons and holes) by the force of an electric field, a field of recombination of electrons and holes, and a function of connecting this to light emission.
As the organic light-emitting material that can be used for the light-emitting layer, low-molecular light-emitting materials and polymer light-emitting materials that can emit fluorescence or phosphorescence can be used. From the viewpoint of forming a light-emitting layer by a coating method. Polymer light emitting materials are preferred.
Polymer light-emitting materials include known polymer light-emitting materials such as polyfluorene derivatives (PF), polyparaphenylene vinylene derivatives (PPV), polyphenylene derivatives (PP), polyparaphenylene derivatives (PPP), and polyvinylcarbazole (PVK). ), Polythiophene derivatives, polydialkylfluorene (PDAF), polyfluorenebenzothiadiazole (PFBT), polyalkylthiophene (PAT), polysilanes such as polymethylphenylsilane (PMPS), and the like can be suitably used.
Further, when a polymer light emitting material is used as the light emitting material of the light emitting layer, the light emitting layer is composed of polymer dye materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene. Further, a low molecular dye material such as tetraphenylbutadiene, Nile red, coumarin 6 or quinacridone may be contained.

  The anode of the organic light emitting device of the present invention supplies holes to a hole injection layer, a hole transport layer, a light emitting layer and the like. The cathode material is preferably one having a work function of 4.5 eV or more. As the material of the anode, a metal, an alloy, a metal oxide, an electrically conductive compound, a mixture thereof, or the like can be used. Specifically, conductive metal oxides such as tin oxide, zinc oxide, indium oxide, and indium tin oxide (ITO), or metals such as gold, silver, chromium, and nickel, and these conductive metal oxides and metals Mixtures or laminates with copper, inorganic conductive materials such as copper iodide and copper sulfide, polyaniline, organic conductive materials such as PEDOT (poly (3,4-ethylenedioxythiophene), polypyrrole, and these and ITO Examples include laminates.

  The cathode of the organic light-emitting device of the present invention supplies electrons to an intermediate layer in contact with the cathode, and the cathode material includes metals, alloys, metal halides, metal oxides, electrically conductive compounds or these A mixture or the like can be used. Specific examples of cathode materials include gold, silver, lead, aluminum, alloys or mixed metals [sodium-potassium alloy, sodium-potassium mixed metal, lithium-aluminum alloy, lithium-aluminum mixed metal, magnesium-silver alloy or Magnesium-silver mixed metal, etc.], rare earth metals [indium, ytterbium, etc.] and the like can be mentioned, and aluminum is preferable from the viewpoint of electrical bonding with the intermediate layer in contact with the cathode.

When the organic light emitting device of the present invention has a hole injection layer and a hole transport layer,
The hole injection layer has a function of injecting holes from the anode, a function of transporting holes, and a function of blocking electrons injected from the cathode.
The hole transport layer has a function of transporting holes, and may have a function of injecting holes from the anode and a function of blocking electrons injected from the cathode.
As materials for the hole injection layer and hole transport layer (hole injection material, hole transport material), known materials can be appropriately selected and used. Specific examples include carbazole derivatives, triazole derivatives, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic Tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds, porphyrin compounds, polysilane compounds, poly (N-vinylcarbazole) derivatives, organic silane derivatives, and polymers containing these. It is. Also include conductive polymer oligomers such as aniline copolymers, thiophene oligomers, polythiophenes, and organic conductive materials such as PEDOT (poly (3,4-ethylenedioxythiophene), polyfluorene polymers, polypyrrole). The material may be a single component or a composition comprising a plurality of components, and the hole injection layer and the hole transport layer may be one or more of the materials. It may be a single layer structure consisting of, or a multilayer structure consisting of a plurality of layers having the same composition or different compositions.

The preferred film thickness of each layer of the organic light-emitting device of the present invention varies depending on the type of material and the layer structure, and is not particularly limited. Since a high applied voltage is required and the efficiency is lowered, the range of several nm to 1 μm is usually preferable.

In the organic light emitting device of the present invention, the device structure is a light emitting device having a light emitting layer between a cathode and an anode, and an intermediate layer in contact with the cathode between the light emitting layer and the cathode, There is no particular limitation as long as the intermediate layer contains at least one selected from an alkali metal complex and an alkaline earth metal complex and a polymer compound, but an anode made of indium tin oxide (ITO) is formed on a glass or plastic substrate. The hole injection layer is formed thereon, the hole transport layer is formed thereon, the light emitting layer is formed thereon, and the intermediate layer in contact with the cathode is formed thereon. A structure in which a cathode is formed thereon is desirable, and more preferably, the cathode is aluminum.

In the organic light-emitting device of the present invention, the formation method of each layer is not particularly limited, and a known method can be used. However, a coating method [casting method, spin coating method, bar coating method, blade method can be used in that the manufacturing process can be simplified. It is preferable to form a film by a coating method, a roll coating method, gravure printing, screen printing, an ink jet method, or the like. In the coating method, a layer can be formed by preparing a coating solution containing a component of a layer to be formed and a solvent, and coating and drying the coating solution on a desired layer (or electrode). The coating liquid may contain a resin as a host material or / and a binder, and the resin can be dissolved in a solvent or dispersed. As the resin, non-conjugated polymers (for example, polyvinyl carbazole) and conjugated polymers (for example, polyfluorene-based polymers) can be used. More specifically, for example, polyvinyl chloride, polycarbonate, Polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, poly (N-vinylcarbazole), hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine A resin, an unsaturated polyester resin, an alkyd resin, an epoxy resin, a silicon resin, or the like can be selected according to the purpose. The coating solution (solution) may contain an antioxidant, a viscosity modifier, and the like as subcomponents depending on the purpose.

As the solvent contained in the coating solution (solution), a stable solvent in which the components of the layer to be formed are uniformly dissolved or dispersed can be appropriately selected from known solvents. Examples of such solvents include alcohols (methanol, ethanol, isopropyl alcohol, etc.), ketones (acetone, methyl ethyl ketone, etc.), organic chlorines (chloroform, 1,2-dichloroethane, etc.), aromatic hydrocarbons [ Benzene, toluene, xylene, etc.], aliphatic hydrocarbons [normal hexane, cyclohexane, etc.], amides [dimethylformamide, etc.], sulfoxides [dimethyl sulfoxide, etc.], and the like. The solvent may be a single component or a mixture of a plurality of components.

In the ink jet method, known components can be used for ink ejection and reproducibility. For example, in order to suppress evaporation from the nozzle, a high boiling point solvent [anisole, bicyclohexylbenzene, etc.] can be used as a component. Moreover, it is preferable that the viscosity of a solution shall be 1-100 mPa * s by selecting a component.

In the method for producing an organic light-emitting device of the present invention, the intermediate layer in contact with the cathode is composed of a polymer compound (preferably a conductive polymer), a solvent, one or more selected from an alkali metal complex and an alkaline earth metal complex. The manufacturing method including the process of forming into a film using the composition containing this is preferable.
In the composition that can be used in this production method, the weight% of the polymer compound relative to the weight of the composition may be a concentration of 0.1% to 2.5%, but is 0.25% to 1.5% from the viewpoint of film formability. Things are preferable.

As the solvent, toluene, xylene, tetrahydrofuran or the like is used, and xylene is more preferable from the viewpoint of solubility and film formability.
The solid content by weight of the alkali metal complex and alkaline earth metal complex with respect to the solid content in the composition is usually from 5% by weight to 50% by weight, preferably from 10% by weight to 30% by weight.
By using this composition, an intermediate layer in contact with the cathode excellent in electron injectability can be formed under atmospheric pressure by a coating method or a printing method.

  The use of the organic light-emitting device of the present invention is not particularly limited, but it can be used for illumination light sources, sign light sources, backlight light sources, display devices, printer heads, and the like. As the display device, a known drive technology, drive circuit, or the like can be used, and a segment type, a dot matrix type, or the like can be selected.

Example 1
The structure and manufacturing method of the light emitting device in the present invention will be described below with reference to FIG.
On the glass substrate on which the ITO anode was formed, a hole injection material solution was formed by spin coating to form a hole injection layer having a thickness of 60 nm. The formed glass substrate was heat-treated at 200 ° C. for 10 minutes to insolubilize the hole injection layer. Here, a PEDOT: PSS solution (poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid, product name Baytron) available from Stark Vitec Co., Ltd. was used as the hole injection material solution.

Next, a hole transporting polymer material was prepared and dissolved in a xylene solvent at a weight concentration of 0.5% to obtain a hole transporting polymer material solution 1. The hole transporting polymer material solution 1 was formed on the glass substrate having the hole injection layer formed thereon by spin coating to form a hole transport layer having a thickness of 20 nm. The formed glass substrate was heat-treated at 200 ° C. for 15 minutes to insolubilize the hole transport layer. Here, HT12 manufactured by Summation Co., Ltd. was used as the hole transporting polymer material.

Next, a polymer light emitting material was prepared and dissolved in a xylene solvent at a weight concentration of 1.4% to obtain a polymer light emitting material solution 1. The polymer light-emitting material solution 1 was formed on the glass substrate having the hole transport layer formed thereon by spin coating to form a light-emitting layer having a thickness of 80 nm. The formed glass substrate was heat-treated at 200 ° C. for 15 minutes to insolubilize the light emitting layer. Here, BP361 manufactured by Summation Co., Ltd. was used as the polymer light emitting material.

Next, an electron transporting polymer material was prepared and dissolved in a xylene solvent at a weight concentration of 0.5% to obtain an electron transporting polymer material solution 1. Furthermore, lithium metal acetylacetonate which is an alkali metal complex was dissolved in a methanol solvent at a weight concentration of 2% to obtain a metal complex solution 1. Here, the electron transporting polymer material is a polyfluorene polymer (2,7-9,9 di-n-octyl fluorenediyl) (2,7-9,9 diisoamyl fluorenediyl) copolymer compound. is there.
Next, the electron transporting polymer material solution 1 and the metal complex solution 1 are mixed so that the metal complex compound is 1% by weight, 10% by weight, 30% by weight, and 50% by weight in the total solid content in the solution. The polymer solution 1, 2, 3, 4 was produced by stirring.

Subsequently, the polymer solution 1 or 2 or 3 or 4 was formed on the light emitting layer-formed glass substrate by a spin coating method to form an intermediate layer in contact with the cathode having a thickness of 20 nm. The formed glass substrate was heat-treated at 130 ° C. for 45 minutes to evaporate the solvent.
Subsequently, 100 nm of aluminum was deposited at a rate of 1 liter / s on the glass substrate on which the intermediate layer had been formed with a vacuum vapor deposition apparatus to form a cathode.
Next, the cathode-formed glass substrate is sealed using a two-component mixed epoxy resin and a sealing glass plate, and the metal complex content (1 wt%, 10 wt%, 30 wt%, 50 wt%) is obtained. Accordingly, organic light-emitting elements 1, 2, 3, and 4 were designated.

Comparative Example 1
A light emitting device was produced by the same production method as described above except that the intermediate layer in contact with the cathode did not contain lithium acetylacetonate, and an organic light emitting device 0 was obtained.

A constant voltage / current power source was prepared, and the organic light emitting device was made to emit light by current injection by applying voltage by connecting the ITO anode of the manufactured organic light emitting device to the anode of the power source and the aluminum cathode to the cathode of the power source. . Table 1 shows the light emission efficiency characteristics of the respective light emitting elements.

As is apparent from Table 1, the luminous efficiency of the element of the present invention (light emitting elements 1 to 4) having a layer containing lithium acetylacetonate and a polyfluorene polymer is not containing lithium acetylacetonate. Compared to a device containing a fluorene polymer (light-emitting device 0), it is significantly higher.
As mentioned above, although the Example of this invention was given, this invention is not limited to these Examples.

1 is a schematic diagram of a structure of a light-emitting element according to the present invention.

Claims (7)

An organic light emitting device having a light emitting layer between a cathode and an anode, and an intermediate layer in contact with the cathode between the light emitting layer and the cathode, wherein the intermediate layer comprises an alkali metal complex and an alkaline earth An organic light-emitting device comprising at least one metal complex selected from metal complexes and a polyfluorene-based polymer compound. The organic light-emitting device according to claim 1, wherein the metal complex is a metal complex with a diketone compound. The organic light-emitting device according to claim 2, wherein the metal complex with the diketone compound is an acetylacetonate metal complex. The organic light-emitting device according to claim 1, wherein the alkali metal complex is a lithium acetylacetonate complex. The organic light-emitting device according to claim 1, wherein the polymer compound is a conductive polymer. The organic light-emitting device according to claim 1, wherein the weight of the metal complex is 5% by weight or more and 50% by weight or less when the total weight of the intermediate layer is 100% by weight. The intermediate | middle layer is formed into a film using the composition containing the said high molecular compound, a solvent, and the 1 or more types of metal complex chosen from the said alkali metal complex and alkaline-earth metal complex. The manufacturing method of the organic light emitting element in any one of.

Images