JP2001284052A - Organic light emitting device - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] In a coating type light emitting device, a carrier having a high light emitting efficiency is realized by improving a carrier transporting ability of a light emitting layer, and a dye having a high quantum efficiency such as a laser dye is introduced. In this case, an organic light-emitting element is realized in which concentration quenching hardly occurs and light emission with high color purity and high efficiency from a dye can be obtained. SOLUTION: By using a copolymer composed of a monomer containing a charge-transporting molecule and a monomer containing a light-emitting molecule as a light-emitting layer, a high carrier-transporting ability of the light-emitting layer can be exhibited even in a coating-type element, and luminous efficiency can be improved. . Further, by using a copolymer containing a monomer containing a light-emitting molecule and a monomer containing another light-emitting molecule as a light-emitting layer, a highly efficient light-emitting element with high color purity can be obtained.
Specifically, in an organic light-emitting device having at least one light-emitting layer 3 between the positive electrode 2 and the negative electrode 4, the light-emitting layer has a monomer (A) containing a charge transporting molecule and a monomer (A) containing a light-emitting molecule ( B) An organic light-emitting device comprising a copolymer comprising:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device used for a flat light source or a flat display.

[0002]

2. Description of the Related Art An electroluminescent element has attracted attention as a display element such as a flat display because it has high visibility due to self light emission and can be made thin. Above all, an organic EL element using an organic compound as a light-emitting element can achieve a desired emission color by being able to be driven at a low voltage, being easy to increase in area, and selecting an appropriate dye as compared with an inorganic EL element. It has features such as being easily obtained, and is being actively developed as a next-generation display.

As an EL element using an organic light-emitting material, blue light emission is obtained by applying a voltage of 30 V to an anthracene vapor-deposited film having a thickness of 1 μm or less (Thi).
n Solid Films, 94 (1982) 171). However, this device did not provide sufficient luminance even when a high voltage was applied, and it was necessary to further improve the luminous efficiency.

On the other hand, Tang et al. Have a transparent electrode (anode),
By stacking a hole transport layer, an electron transporting light emitting layer, and a cathode using a metal having a low work function, the luminous efficiency was improved, and a luminance of 1000 cd / m ² was realized with an applied voltage of 10 V or less. (Appl. Phys. Lett., 51 (1987) 913). Here, the layers (organic layer and metal) other than the transparent electrode are formed by a vacuum evaporation method.

Further, a device having a three-layer structure in which a light emitting layer is sandwiched between a hole transport layer and an electron transport layer (Jpn. J. Appl Phys., 27 (19)
88) L269), and an element (J. Appl. Phys., 65 (1989) 3610) that obtains light emission from a dye doped in a light emitting layer.

The method of doping the light emitting layer with a dye is an effective method for improving the luminous efficiency and increasing the color of light emitted. That is, in the light-emitting layer, a host having a high quantum efficiency such as a laser dye is used as a guest, and the guest is doped into a host material capable of sustaining the injection of holes and electrons. Light emission of the guest material due to energy transfer from the material or light emission from an excited state due to carrier trap of the guest material can be obtained. Therefore, even in the conventional method, even a dye that could not be used for the light emitting layer as a single film because of a low charge transport property or concentration quenching occurred, it was possible to introduce the dye into the light emitting layer by using the doping method described above. The range of material selection has expanded. Generally, the doping amount of a dye used as a guest material is about 10% or less of a host material, and a material having a large concentration quenching, such as a red light-emitting material, has an extremely large amount of 0.1 to several%. A small amount of doping is required. It is very difficult to control such a small amount of doping by a dry process such as a vacuum evaporation method. When the doping concentration is increased, the luminous efficiency is lowered due to the concentration quenching as described above, and when the doping concentration is small, the luminescence of the host material is increased, and luminescence with good color purity from the guest material alone cannot be obtained.

On the other hand, there is a method of forming an element by a so-called wet film forming method such as a spin coating method or a casting method for forming an element by the above-mentioned dry process (for example, Japanese Patent Laid-Open No. 3-790). And JP-A-3-171.
No. 590).

That is, the hole transport layer, the electron transport layer,
At least one or more materials forming the light emitting layer are dissolved in a suitable solvent together with a polymer binder, and this is applied to the electrode surface to form a light emitting layer. Further, an electrode is formed on the light emitting layer by a vapor deposition method or the like. Is what you do. According to this method, even a small amount of doping, which was difficult to control in the dry process as described above, can be realized relatively easily because only a predetermined amount of the host and guest materials need be dissolved in the solvent. Hereinafter, the organic light emitting device thus manufactured is referred to as a coating type light emitting device with respect to a conventional stacked light emitting device.

[0009] In addition to the above points, the coating type light emitting element is
(1) It is possible to use materials that are difficult to form in a dry process, (2) it can be manufactured at low cost, (3) it is thermally stable,
There are advantages such as.

The light emitting layer of the conventional coating type light emitting device is constituted by dispersing a perinone derivative or tris (8-quinolinolato) aluminum as a light emitting material in polyvinyl carbazole (Japanese Unexamined Patent Publication No. 3-790), and emitting light in polycarbonate. Examples of such a material include those in which tris (8-quinolinolato) aluminum and tetraphenylbenzidine are dispersed (Japanese Patent Laid-Open No. 3-171590).

[0011]

Although the coating type light emitting device has the above-mentioned advantages, it has a problem that the luminous efficiency is lower than that of the conventional laminated type light emitting device.

One of the causes of the low luminous efficiency of the coating type light emitting device is that the carrier transport ability of the polymer layer is low. That is, in the case of a stacked light emitting element using low molecules,
The charge transport layer and the light-emitting layer are made of almost a single material except for the case where a small amount of doping is performed, and since the distance between molecules is small, charge transfer between molecules is likely to occur. In the case of a light-emitting device, one or more kinds of charge transporting materials or light-emitting materials are dispersed in a polymer binder, and the intermolecular distance is larger than that of a low-molecular stacked device, so that intermolecular charge transfer hardly occurs.

Further, as described above, the coating type light emitting device can relatively easily realize a small amount of doping as compared with the low molecular weight laminated type device. If the temperature is low, sufficient light emission from the guest cannot be obtained.

The present invention solves the above-mentioned problems, and realizes a high luminous efficiency by improving the carrier transporting ability of the luminescent layer in a coating type light emitting device, and furthermore, a dye having a high quantum efficiency such as a laser dye. The present invention realizes an organic light-emitting device in which concentration quenching is less likely to occur when the compound is introduced, and high-efficiency light emission with good color purity from a dye is obtained.

[0015]

Means for Solving the Problems As a result of intensive studies to achieve the above object, we have found that a light emitting layer comprising a copolymer comprising a monomer containing a charge transporting molecule and a monomer containing a light emitting molecule. As a result, it has been found that even in a coating type element, a high carrier transport ability of the light emitting layer is exhibited, and the light emitting efficiency can be improved. Furthermore, they have found that a highly efficient light-emitting element with high color purity can be obtained by using a copolymer of a monomer containing a light-emitting molecule and a monomer containing another light-emitting molecule as a light-emitting layer.

Specifically, the organic light-emitting device according to the first aspect of the present invention is an organic light-emitting device having at least one light-emitting layer between a positive electrode and a negative electrode, wherein the light-emitting layer is a charge-transporting molecule. Is an organic light-emitting device comprising a copolymer comprising a monomer (A) containing a luminescent molecule and a monomer (B) containing a luminescent molecule.

Further, the invention of claim 2 of the present application is an organic light-emitting device in which the charge-transporting molecule of the monomer (A) according to claim 1 has a hole-transporting property.

According to a third aspect of the present invention, there is provided an organic light emitting device wherein the charge transporting molecule of the monomer (A) according to the second aspect contains a carbazole derivative.

Further, the invention of claim 4 of the present application is an organic light emitting device wherein the charge transporting molecule of the monomer (A) according to claim 2 contains an aromatic amine compound.

The invention of claim 5 of the present application is an organic light-emitting device in which the charge-transporting molecule of the monomer (A) according to claim 1 has an electron-transporting property.

According to a sixth aspect of the present invention, there is provided an organic light emitting device wherein the charge transporting molecule of the monomer (A) according to the fifth aspect contains an oxadiazole derivative.

According to a seventh aspect of the present invention, there is provided an organic light emitting device wherein the charge transporting molecule of the monomer (A) according to the fifth aspect contains a triazole derivative.

According to an eighth aspect of the present invention, there is provided an organic light emitting device wherein the charge transporting molecule of the monomer (A) according to the fifth aspect contains a quinolinol complex or a derivative thereof.

Further, the invention of claim 9 of the present application provides
8. The luminescent molecule of the monomer (B) described in 8 is an organic luminescent device containing an oxadiazole derivative.

[0025] The invention of claim 10 of the present application is the invention of claim 1.
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, is an organic light-emitting device containing a quinolinol complex or a derivative thereof.

The invention of claim 11 of the present application is directed to claim 1
The luminescent molecule of the monomer (B) according to any one of the above (1) to (8) is an organic light emitting device containing a coumarin derivative.

The invention of claim 12 of the present application is directed to claim 1
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, is an organic light-emitting device containing a phenoxazone derivative.

Further, the invention of claim 13 of the present application is the invention of claim 1
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, is an organic light-emitting device containing rubrene or a derivative thereof.

Further, the invention of claim 14 of the present application is the invention of claim 1
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, wherein the organic light-emitting device contains perylene or a derivative thereof.

Further, the invention of claim 15 of the present application is the invention of claim 1
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, is an organic light-emitting device containing quinacridone or a derivative thereof.

Further, the invention of claim 16 of the present application is the invention of claim 1
The light-emitting molecule of the monomer (B) according to any one of Items 1 to 8, is an organic light-emitting device containing an anthracene derivative.

Further, the invention of claim 17 of the present application is the invention of claim 1
8. The luminescent molecule of the monomer (B) according to any one of the above (8) to (8) is an organic light emitting device containing a styryl derivative.

The organic light-emitting device according to the invention of claim 18 is the organic light-emitting device having at least one light-emitting layer between a positive electrode and a negative electrode, wherein the light-emitting layer is a monomer containing a light-emitting molecule (C ) And a monomer (D) containing another luminescent molecule.

[0034] The invention of claim 19 of the present application is the invention of claim 1.
8. An organic light-emitting device wherein the luminescent molecule of the monomer (C) according to 8 is a substance capable of sustaining injection of holes and electrons.

Further, the invention of claim 20 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) described in any one of 8 to 19 is an organic light-emitting device that emits light by energy transfer from the excited state of the luminescent molecule of the monomer (C).

Further, the invention of claim 21 of the present application is the invention of claim 1
20. An organic light-emitting device according to any one of Items 8 to 20, wherein the luminescent molecule of the monomer (D) has a smaller negative reduction potential than the luminescent molecule of the monomer (C).

Further, the invention of claim 22 of the present application is the invention of claim 1
The luminescent molecule of the monomer (C) according to any one of 8 to 21 is an organic light-emitting device containing an oxadiazole derivative.

Further, the invention of claim 23 of the present application is the invention of claim 1
The luminescent molecule of the monomer (C) according to any one of 8 to 21 is an organic light-emitting device containing a quinolinol complex or a derivative thereof.

The invention of claim 24 of the present application is directed to claim 1
The luminescent molecule of the monomer (C) according to any one of 8 to 21 is an organic light-emitting device containing an anthracene derivative.

Further, the invention of claim 25 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) according to any one of 8 to 24 is an organic light-emitting device containing a coumarin derivative.

Further, the invention of claim 26 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) according to any one of 8 to 24 is an organic light-emitting device containing a phenoxazone derivative.

Further, the invention of claim 27 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) described in 8 to 24 is an organic light-emitting device containing rubrene or a derivative thereof.

Further, the invention of claim 28 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) according to any one of items 8 to 24 is an organic light-emitting device containing perylene or a derivative thereof.

Further, the invention of claim 29 of the present application is the invention of claim 1
The luminescent molecule of the monomer (D) according to any one of items 8 to 24 is an organic light-emitting device containing quinacridone or a derivative thereof.

The invention of claim 30 of the present application is directed to claim 1
The luminescent molecule of the monomer (D) according to any one of items 8 to 24 is an organic light-emitting device containing a styryl derivative.

Further, the invention of claim 31 of the present application is
31. The organic light-emitting device according to any one of Items 30 to 30, wherein the light-emitting layer contains a low-molecular charge transporting material.

Further, the invention of claim 32 of the present application is the invention of claim 1
32. The organic light-emitting device according to any one of items 31 to 31, further comprising a hole injection layer between the positive electrode and the light-emitting layer.

Further, the invention of claim 33 of the present application is the invention of claim 1
33. The organic light-emitting device according to any one of Items 32 to 32, further comprising an electron injection layer between the negative electrode and the light-emitting layer.

[0049]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing one example of the organic light emitting device according to the present invention. In FIG. 1, 1 is a substrate, 2 is a positive electrode, 3 is a light emitting layer, and 4 is a negative electrode.

The substrate 1 is only required to support the organic light-emitting device of the present invention. A transparent substrate such as glass or a resin film such as polycarbonate, polymethyl methacrylate, or polyethylene terephthalate, or an opaque substrate such as silicon is used. be able to.

At least one of the positive electrode 2 and the negative electrode 4 needs to be transparent or translucent. Light emitted from the light emitting layer is extracted to the outside through one or both electrodes. Usually, a transparent electrode such as indium tin oxide (ITO) or tin oxide is often used as the positive electrode 2, but a metal electrode such as NI, Au, Pt, or Pd may be used. For the purpose of improving the transparency or reducing the resistivity of the ITO film, a film forming method such as sputtering, electron beam evaporation, or ion plating is employed. The film thickness is determined from the required sheet resistance value and visible light transmittance. However, since the organic light emitting element has a relatively high driving current density, it is used at a thickness of 1000 mm or more to reduce the sheet resistance value. Is often done. Examples of the cathode 4 include alloys of metals such as Al, Ag, and Au, metals having low work functions such as MgAg alloys and AlLi alloys, and metals having relatively large work functions and stable metals.
A stacked electrode of a metal having a low work function and a metal having a high work function, such as / Al and LiF / Al, can be used.
A vapor deposition method or a sputtering method is preferred for forming these negative electrodes. In FIG. 1, although the structure is such that the substrate / positive electrode / light-emitting layer / negative electrode is arranged from the bottom, it is not always necessary to stack in this order. It may be in order. In FIG. 1, when only the electrode on the substrate 1 side, that is, the positive electrode 2 is transparent and the negative electrode 4 is opaque, the substrate 1 also needs to be a transparent substrate in order to extract light emission to the outside.

The light-emitting layer 3 is made of a copolymer composed of a monomer (A) containing a charge-transporting molecule and a monomer (B) containing a light-emitting molecule, or a monomer (C) containing a light-emitting molecule and another light-emitting molecule. A copolymer consisting of a monomer (D) containing a hydrophilic molecule is used.

As the monomer (A), for example, monomers having a vinyl group represented by the following general formulas (1) to (7) are used.

[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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[0059]

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[0060]

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In formulas (1) to (7), X is an arylene group or an alkylene group, and Y1 is a charge transporting molecule. As the charge transporting molecule Y1, it is preferable to use a carbazole derivative, an aromatic amine compound as the hole transporting molecule, and an oxadiazole derivative, a triazole derivative, a quinolinol complex or a derivative thereof as the electron transporting molecule. As the monomer (B), for example, a monomer having a vinyl group represented by the following general formulas (Chem. 8) to (Chem. 14) is used.

[0062]

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[0063]

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[0064]

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[0065]

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[0066]

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[0067]

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[0068]

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In formulas (8) to (14),
Represents an arylene group or an alkylene group, and Y2 represents a luminescent molecule. Examples of the luminescent molecule Y2 include an oxadiazole derivative, a quinolinol complex or a derivative thereof, a carbazole derivative, an aromatic amine compound, a coumarin derivative, a phenoxazone derivative, rubrene or a derivative thereof, a perylene or a derivative thereof, a quinacridone or a derivative thereof, an anthracene derivative, It is preferable to use styryl derivatives.

As the monomer (C), for example, monomers having a vinyl group represented by the following general formulas (Formula 15) to (Formula 21) are used.

[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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[0077]

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In formulas (15) to (21),
X is an arylene group or an alkylene group, and Y3 is a luminescent molecule. It is preferable that the light-emitting molecule Y3 be a substance that can continuously inject holes and electrons. Further, as the monomer (D), for example, the following general formulas (Chemical Formula 22) to (Chemical Formula 2)
The monomer having a vinyl group shown in 8) is used.

[0079]

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[0080]

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[0081]

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[0082]

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[0083]

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[0084]

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[0085]

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In formulas (22) to (28),
X is an arylene group or an alkylene group, and Y4 is a luminescent molecule. The luminescent molecule Y4 preferably emits light by energy transfer from the excited state of the luminescent molecule Y3 of the monomer (C). Alternatively, the luminescent molecule Y4 of the monomer (D) preferably has a smaller negative reduction potential than the luminescent molecule Y3 of the monomer (C).

That is, similarly to the conventional doped light emitting device, after the light emitting molecule Y3 is excited by injection of electric charge,
Energy transfer occurs from the light-emitting molecule Y3 in the excited state to the light-emitting molecule Y4, and light emission from Y4 is obtained. Alternatively, when the luminescent molecule Y4 has a negative reduction potential smaller than that of the luminescent molecule Y3, the trapping of the charge injected into the Y3 excites the Y4 and emits light.

As the luminescent molecule Y3 of the monomer (C), it is preferable to use an oxadiazole derivative, the quinolinol complex shown or a derivative thereof, an aromatic amine compound, and a carbazole derivative. As the luminescent molecule Y4 of the monomer (D), it is preferable to use a coumarin derivative, a phenoxazone derivative, rubrene or a derivative thereof, perylene or a derivative thereof, quinacridone or a derivative thereof, an anthracene derivative, or a styryl derivative.

A conventional coating type light emitting device is a device in which a hole transporting polymer such as polyvinyl carbazole is used as a light emitting layer between a positive electrode and a negative electrode, and tris (8-quinolinolato) is used.
A material in which a light emitting material such as aluminum is dispersed is sandwiched. When a voltage is applied between both electrodes of the device in the forward direction, holes are injected from the positive electrode and electrons are injected from the negative electrode into the light emitting layer, and then holes and electrons are recombined in the light emitting layer. In response, the light emitting material emits fluorescence or phosphorescence. In this case, holes injected from the electrodes are mainly transported in polyvinyl carbazole, and electrons are mainly transported in tris (8
-Quinolinolato) transported through aluminum. Then, electrons and holes are recombined in tris (8-quinolinolato) aluminum, and light emission is generated in response to the recombination.

As described above, the luminous efficiency of the device depends on the charge transport capability of the device, and the charge transport capability is affected by the intermolecular distance in the device. In the case of the conventional coating type light emitting device, since the low molecular compound is dispersed in the polymer, the intermolecular distance responsible for each charge transport is larger than that of the low molecular stack type, and therefore the charge transport ability of the light emitting layer is low. . On the contrary,
When a copolymer comprising a monomer (A) containing a charge-transporting molecule and a monomer (B) containing a luminescent molecule is used as in the organic light-emitting device of the present invention, the charge-transporting portion and the luminescent portion are chemically bonded. Charge is transported efficiently,
Luminous efficiency is improved.

As another example of the conventional coating type light emitting device,
For example, a material in which an electron transporting material such as an oxadiazole derivative and a light emitting material such as a coumarin derivative are dispersed in a hole transporting polymer such as polyvinyl carbazole is used as a light emitting layer. In this case, holes are transported in polyvinyl carbazole, and electrons are transported in the oxadiazole derivative, and electrons and holes are recombined in the coumarin derivative, which is a light emitting material, to emit light.

In the light emitting device, since the hole and electron transport materials are present in the light emitting layer, the charge transporting ability is relatively large. However, in the light emitting material having poor charge transporting property, electrons and holes are recombined. In order to form an excited state, both carriers need to be injected into the luminescent material over the barrier, and this barrier causes a reduction in luminous efficiency.

On the other hand, in the light emitting device of the present invention, the light emitting efficiency is improved by including a low molecular charge transporting material in the light emitting layer made of the copolymer. That is, for example, an electron-transporting low-molecular compound in a copolymer composed of a monomer containing a hole-transporting molecule such as a carbazole derivative as a light-emitting layer and a monomer containing a light-emitting molecule having a low charge-transporting property such as a coumarin derivative Is introduced. As a result, electron injection into the luminescent molecule has the same barrier as in the above-described conventional device. However, in the hole injection, since the hole transporting molecule and the luminescent molecule are chemically bonded, As a result, the barrier becomes smaller, thereby improving the luminous efficiency as compared with the related art. As the electron transporting low-molecular compound, any compound may be used, but preferably an oxadiazole derivative, a triazole derivative, a quinolinol complex or a derivative thereof may be used.

Contrary to the above, for example, the hole transport in a copolymer comprising a monomer containing an electron transporting molecule such as an oxadiazole derivative and a monomer containing a light emitting molecule having a low charge transporting property such as a coumarin derivative. Low molecular weight compounds may be introduced. Any low-molecular compound having a hole-transporting property may be used, but a carbazole derivative, an aromatic amine compound, a stilbene compound, or the like is preferably used.

On the other hand, when the light emitting layer is doped with a dye, as described above, the doping control of the coating type light emitting element is relatively easy as compared with the low molecular weight stacked type light emitting element.
The problem of a decrease in luminous efficiency due to concentration quenching remains in both the low-molecular stack type and the coating type. This is because the guest material is agglomerated in the host material, and light emission from a single molecule disappears due to intermolecular interaction. On the other hand, by using a copolymer composed of a monomer (C) containing a light-emitting molecule, which is a host material of a conventional device, and a monomer (D) containing another light-emitting molecule, which is a guest material, in the light-emitting layer, Since the luminescent molecule is fixed in the polymer, the interaction between molecules due to aggregation as in the related art hardly occurs, and the concentration quenching hardly occurs.
Therefore, a highly efficient light-emitting element having better color purity than a light-emitting element using a conventional doping method can be obtained.

In the light emitting layer using a copolymer in which these two kinds of light emitting molecules are combined, a low molecular charge transport material may be contained in the light emitting layer. In this case, the low molecular compound to be introduced may be a hole transporting material, an electron transporting material, or both, depending on the charge transporting performance of the copolymer.

In the light emitting device of the present invention, a hole injection layer can be inserted between the positive electrode and the light emitting layer. By inserting an appropriate hole injection layer, the operating voltage of the light emitting element can be reduced. In other words, when holes are injected from the positive electrode into the light emitting layer, the difference between the ionization potential or work function of the positive electrode and the ionization potential of the hole transporting substance in the light emitting layer acts as an injection barrier. The voltage will be high. On the other hand, a hole injection layer is inserted between the light emitting layer and the positive electrode, and the ionization potential or work function of the hole injection material is different from the ionization potential or work function of the positive electrode and the hole transport in the light emitting layer. When the potential is between the ionization potentials of the active substance, the above-described hole injection barrier is relaxed, so that the operating voltage is also reduced. As the hole injection layer, for example, a polymer such as a polyaniline derivative or a polythiophene derivative may be formed by a coating method or the like, or an amorphous film of amorphous carbon or the like may be formed by a sputtering method, a CVD method, or the like. Alternatively, a low molecular compound such as a phthalocyanine-based compound or an aromatic amine compound may be formed by an evaporation method or the like. Further, these layers may be laminated.

On the other hand, an electron injection layer may be inserted between the negative electrode and the light emitting layer. As in the case of the hole injection layer, the operation voltage of the light emitting element can be reduced by inserting an appropriate electron injection layer. That is, when electrons are injected from the negative electrode into the light emitting layer, the difference between the work function of the negative electrode and the electron affinity of the electron transporting substance in the light emitting layer becomes an injection barrier. turn into. On the other hand, an electron injection layer is inserted between the light emitting layer and the negative electrode,
When the electron affinity or work function of the electron injecting material is between the work function of the negative electrode and the electron affinity of the electron transporting substance in the light emitting layer, the aforementioned electron injection barrier is relaxed, and the operating voltage is also reduced. Lower. Examples of the electron injecting layer include ordinary electron transporting materials such as quinolinol complexes, oxadiazole derivatives and triazole derivatives, metal phthalocyanines such as dilithium phthalocyanine and disodium phthalocyanine, and 4,4,8,8-tetrakis (1H-pyrazole). -1-yl) An organic boron complex compound such as pyrazaball or the like can be formed by an evaporation method.

Of course, there is no problem if both the hole injection layer and the electron injection layer are inserted.

The method for producing the copolymer of the present invention is not particularly limited as long as the monomers used are polymerized. Examples of the polymerization method include radical polymerization and cationic polymerization. In the case of radical polymerization, as a polymerization initiator, for example, azoisobutyronitrile (AIB)
An azo compound such as N), a peroxide such as benzoyl peroxide (BPO), a dithiocarbamate derivative such as tetraethyluram disulfide, or the like can be used. Further, in the case of cationic polymerization, for example, Lewis acids such as trifluoroborate and tin tetrachloride, inorganic acids such as sulfuric acid and hydrochloric acid, and cation exchange resins can be used as the polymerization initiator. Examples of the polymerization solvent include hydrocarbon solvents such as benzene, toluene, xylene, hexane, and cyclohexane; halogenated hydrocarbon solvents such as chloroform, carbon tetrachloride, and chlorobenzene; N, N-dimethylformamide;
Use of amide solvents such as N-dimethylacetamide, N-methyl-2-pyrrolidone, N, N-dimethylsulfoxide, ether solvents such as diphenyl ether, dioxane and tetrahydrofuran, ketone solvents such as cyclohexylbenzophenone and cyclohexanone. Can be.

The average molecular weight of the copolymer is not particularly limited, but is preferably 10,000 to 1,000,000
Is good.

Next, the present invention will be described in more detail based on specific embodiments.

Example 1 An organic light-emitting device having the structure shown in FIG. 1 was manufactured as follows. A glass substrate having a thickness of 0.7 mm was used as a substrate 1, and ITO was formed thereon as a positive electrode 2 by a sputtering method. ITO film thickness is about 1000
(4) The sheet resistance was set to about 15 Ω / □, and patterned into a desired shape by photolithography.

The material used for the light emitting layer 3 was synthesized as follows. 400 mg of N-vinylcarbazole represented by the formula (29) and 200 mg of a compound containing an oxadiazole derivative represented by the formula (30) were dissolved in 20 ml of toluene, 10 mg of AIBN was added, and the mixture was stirred at 70 ° C. for 5 hours.

[0105]

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[0106]

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This solution was dropped into 200 ml of methanol to coagulate and collect the polymer. The recovered polymer was dissolved in THF (20 ml) and added dropwise to 200 ml of methanol again to recover the precipitated polymer. The obtained polymer was dried under reduced pressure at 50 ° C. for 1 day to obtain a target copolymer. This copolymer contained 80 mol% of the structure represented by the formula (29) and 20 mol% of the structure represented by the formula (30), and had a molecular weight of about 28,000.

The copolymer 30 synthesized as described above
0 mg of a 30: 1 mixed solvent of toluene and chloroform.
and stirred for 1 day. This solution was spin-coated on the glass substrate with ITO, which had been previously washed and subjected to oxygen plasma treatment, to obtain a light-emitting layer 3. Spin coating is performed at 500 rpm in a sealed state using a spinner.
The heat treatment was performed for 10 seconds at 1000 rpm for 30 seconds, and then heat treatment was performed at 110 ° C. for 1 minute using a hot plate. The thickness of the light emitting layer 3 was about 1000 °.

Next, a Li / Al laminated electrode was formed as the cathode 4 by a vacuum evaporation method. Film formation is about 5 × 10
Performed under ^-6 Torr, after 10Å deposited first Li at a rate of about 0.5 Å / sec, and 1500Å depositing Al at about 30 Å / sec. The desired shape of the cathode was obtained using a mask.

When a voltage was applied to the organic light emitting device thus produced in the direction shown in FIG. 1, the device emitted blue light. Table 1 shows the current efficiency (cd / A) at this time.

[0111]

[Table 1]

Example 2 A copolymer was prepared in the same manner as in Example 1 using 400 mg of a compound containing an aromatic amine represented by the formula (31) and 300 mg of a compound containing a quinolinol complex represented by the formula (32). Synthesized.

[0113]

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[0114]

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In the obtained copolymer, the structure represented by the formula (31) was 55 mol%, and the structure represented by the formula (32) was 45 mol%.
It had a molecular weight of about 32,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 3 500 mg of a compound containing an oxadiazole derivative represented by the formula (33) was added to a compound of the formula (3)
Compound 100 containing quinacridone derivative shown in 4)
A copolymer was synthesized in the same manner as in Example 1 using mg.

[0118]

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[0119]

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In the obtained copolymer, the structure represented by the formula (33) was 80 mol%, and the structure represented by the formula (34) was 20 mol%.
It had a molecular weight of about 40,000.

This copolymer was used as a light-emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 4 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of the compound containing the triazole derivative represented by the formula (35) and 100 mg of the compound containing the quinacridone derivative represented by the formula (34). did.

[0123]

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In the obtained copolymer, the structure represented by the formula (35) was 80 mol%, and the structure represented by the formula (34) was 20 mol%.
It had a molecular weight of about 40,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 5 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of the compound containing the quinolinol complex represented by the formula (32) and 100 mg of the compound containing rubrene represented by the formula (36). .

[0127]

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In the obtained copolymer, the structure represented by the formula (32) was 85 mol%, and the structure represented by the formula (36) was 15 mol%.
It had a molecular weight of about 42,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 6 A copolymer was prepared in the same manner as in Example 1 using 500 mg of a compound containing an aromatic amine represented by the formula (31) and 25 mg of a compound containing a phenoxazone derivative represented by the formula (37). Synthesized.

[0131]

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The obtained copolymer contained 92 mol% of the structure represented by the formula (31) and 8 mol% of the structure represented by the formula (37), and had a molecular weight of about 28,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 7 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of N-vinylcarbazole represented by the formula (29) and 100 mg of a perylene-containing compound represented by the formula (38).

[0135]

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In the obtained copolymer, the structure represented by the formula (29) was 90 mol%, and the structure represented by the formula (38) was 10 mol%.
It had a molecular weight of about 30,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 8 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of N-vinylcarbazole represented by the formula (29) and 50 mg of a compound containing quinacridone represented by the formula (34).

The obtained copolymer contained 95 mol% of the structure represented by the formula (29) and 5 mol% of the structure represented by the formula (34), and had a molecular weight of about 28,000.

This copolymer was used as a light-emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 9 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of the compound containing an aromatic amine represented by the formula (31) and 200 mg of the compound containing anthracene represented by the formula (39). did.

[0142]

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In the obtained copolymer, the structure represented by the formula (31) was 65 mol%, and the structure represented by the formula (39) was 35 mol%.
It had a molecular weight of about 30,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 10 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of N-vinylcarbazole represented by the formula (29) and 50 mg of a compound containing a styryl derivative represented by the formula (40).

[0146]

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The obtained copolymer contained 95 mol% of the structure represented by the formula (29) and 5 mol% of the structure represented by the formula (40), and had a molecular weight of about 28,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 11 500 mg of a compound containing an oxadiazole derivative represented by the formula (30) was added to a compound of the formula (4)
100 mg of a compound containing the coumarin derivative shown in 1)
Was used to synthesize a copolymer in the same manner as in Example 1.

[0150]

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In the obtained copolymer, the structure represented by the formula (30) was 80 mol%, and the structure represented by the formula (41) was 20 mol%.
It had a molecular weight of about 30,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 12 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of a compound containing a quinolinol complex represented by the formula (32) and 100 mg of a compound containing a coumarin derivative represented by the formula (42). did.

[0154]

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In the obtained copolymer, the structure represented by the formula (32) was 80 mol%, and the structure represented by the formula (42) was 20 mol%.
It had a molecular weight of about 30,000.

This copolymer was used as a light-emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 13 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of a compound containing a quinolinol complex represented by the formula (32) and 25 mg of a compound containing a phenoxazone derivative represented by the formula (37). did.

The obtained copolymer contained 92 mol% of the structure represented by the formula (32) and 8 mol% of the structure represented by the formula (37), and had a molecular weight of about 28,000.

This copolymer was used as a light-emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 14 Example 1 was carried out using 500 mg of the anthracene-containing compound represented by the formula (39) and 100 mg of the perylene-containing compound represented by the formula (38).
A copolymer was synthesized in the same manner as described above.

In the obtained copolymer, the structure represented by the formula (32) was 75 mol%, and the structure represented by the formula (38) was 25 mol%.
It had a molecular weight of about 30,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 15 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of a compound containing a quinolinol complex represented by the formula (32) and 100 mg of a compound containing a quinacridone derivative represented by the formula (34). did.

In the obtained copolymer, the structure represented by the formula (32) was 75 mol%, and the structure represented by the formula (34) was 25 mol%.
It had a molecular weight of about 32,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 16 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of a compound containing a quinolinol complex represented by the formula (32) and 50 mg of a compound containing a styryl derivative represented by the formula (42). did.

In the obtained copolymer, the structure represented by the formula (32) was 85 mol%, and the structure represented by the formula (42) was 15 mol%.
It had a molecular weight of about 28,000.

This copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

Example 17 A copolymer was synthesized in the same manner as in Example 1 using 500 mg of the compound containing anthracene represented by the formula (39) and 100 mg of the compound containing a coumarin derivative represented by the formula (41). .

In the obtained copolymer, the structure represented by the formula (39) was 88 mol%, and the structure represented by the formula (41) was 12 mol%.
It had a molecular weight of about 30,000.

The copolymer was used as a light emitting layer in Example 1
An organic light-emitting device was produced in the same manner as described above. Table 1 shows the evaluation results of the device.

(Example 18) As a light emitting layer, 300 mg of the copolymer synthesized in Example 3 and N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 '
-A mixture of 150 mg of biphenyl-4,4'-diamine was dissolved in a mixed solvent of toluene and chloroform 1: 1.
Spin coating was performed on the substrate with ITO in the same manner as in Example 1. Otherwise, the procedure of Example 1 was followed to fabricate an organic light-emitting device.

Table 1 shows the evaluation results of this device.

(Example 19) As a light emitting layer, 300 mg of the copolymer synthesized in Example 6 and 2- (4-biphenyl) -5- (4-tertbutylphenyl) -1,3,4-
A mixture of 150 mg of oxadiazole was dissolved in a mixed solvent of toluene and chloroform 1: 1 and spin-coated on a substrate with ITO in the same manner as in Example 1. Otherwise, the procedure of Example 1 was followed to fabricate an organic light-emitting device.

Table 1 shows the evaluation results of this device.

(Example 20) In the organic light emitting device of Example 3, a commercially available polythiophene derivative was inserted as a hole injection layer between the positive electrode and the light emitting layer. The hole injection layer was formed by a spin coating method similarly to the light emitting layer, and the thickness was set to about 150 °. Otherwise in the same manner as in Example 3, an organic light-emitting device was manufactured.

Table 1 shows the evaluation results of this device.

(Example 21) In the organic light emitting device of Example 6, 4 was used as an electron injection layer between the cathode and the light emitting layer.
8,8-Tetrakis (1H-pyrazol-1-yl) pyrazaball was inserted. The electron injection layer is formed by a vacuum evaporation method, and 4,8,8-tetrakis (1H-
Pyrazol-1-yl) pyrazaball at about 0.3 l / s
After forming a film at a rate of 10 ° C. at an ec rate, Li /
An Al laminated electrode was formed in the same manner as in Example 6.

Table 1 shows the evaluation results of the device.

Comparative Example 1 As a light emitting layer, 500 mg of polyvinyl carbazole and 100 mg of perylene were dissolved in 60 ml of a mixed solvent of toluene and chloroform 1: 1.
Spin coating was performed on the substrate with ITO in the same manner as in Example 1. Otherwise, the procedure of Example 1 was followed to fabricate an organic light-emitting device.

Table 1 shows the evaluation results of this device.

As can be seen from Table 1, in Example 7 and Comparative Example 1, luminous efficiency was higher in Example 7 even though carbazole and perylene were contained in the same ratio. This is because in Example 7, both substances are chemically bonded, and charges transported in the polymer are efficiently injected into perylene of the side chain.

Comparative Example 2 A polymer was synthesized in the same manner as in Example 1 using only the compound containing the quinolinol complex represented by the formula (32). Obtained polymer 300
mg and 15 m of the phenoxazone derivative represented by the formula (43).
g of toluene and chloroform 1: 1 mixed solvent 30 ml
And spin-coated on a substrate with ITO in the same manner as in Example 1.

[0184]

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Otherwise, the procedure of Example 1 was followed to fabricate an organic light-emitting device.

Table 1 shows the evaluation results of the device.

(Comparative Example 3) Tris (8-
A film in which (quinolinolato) aluminum and the phenoxazone derivative represented by the formula (43) were deposited at a weight ratio of 20: 1 was used. The light emitting layer was formed on a substrate with ITO by using a vacuum evaporation method. The film formation rate was 10 ° / sec of tris (8-quinolinolato) aluminum and 0.5 ° / sec of the phenoxazone derivative, and both substances were deposited from separate boats. Subsequently, a Li / Al electrode was formed in the same manner as in Example 1 to obtain an organic light emitting device.

Table 1 shows the evaluation results of the device.

In Example 13 and Comparative Examples 2 and 3, despite the fact that tris (8-quinolinolato) aluminum and the phenoxazone derivative were contained in the same ratio, Example 1 was used.
3 has higher luminous efficiency. This is because, in Comparative Examples 2 and 3, the phenoxazone derivative was condensed in the light emitting layer to cause concentration quenching, and the luminous efficiency was reduced.
In the above, since the phenoxazone derivative is bonded to the polymer linear chain, these condensation hardly occurs, and concentration quenching hardly occurs.

In this example, a copolymer containing a monomer containing a charge-transporting molecule and a monomer containing a light-emitting molecule, or a copolymer containing a monomer containing a light-emitting molecule and another monomer containing a light-emitting molecule was used. But
It may be a copolymer composed of three types of monomers or four or more types of monomers each containing a charge transporting molecule, a luminescent molecule, and another luminescent molecule.

[0191]

As described above, according to the organic light-emitting device of the present invention, the light-emitting layer contains a copolymer composed of a monomer containing a charge transporting molecule and a monomer containing a light-emitting molecule. Since the charge transporting portion and the light emitting portion are chemically bonded, the charge is efficiently transported, and the luminous efficiency is improved.

Further, according to another organic light-emitting device of the present invention, the light-emitting layer contains a copolymer comprising a monomer containing a light-emitting molecule and a monomer containing another light-emitting molecule. Since the molecules are fixed in the polymer, a decrease in efficiency due to quenching of the concentration of the luminescent molecule can be prevented, and luminous efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an organic light emitting device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 positive electrode 3 light emitting layer 4 negative electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Sato 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Term (reference) 3K007 AB03 CA01 CA03 CA06 CB01 DB03 EB00

Claims (33)

[Claims] 1. An organic light emitting device having at least one light emitting layer between a positive electrode and a negative electrode, wherein the light emitting layer comprises:
An organic light-emitting device comprising a copolymer comprising a monomer (A) containing a charge transporting molecule and a monomer (B) containing a light-emitting molecule. 2. The organic light emitting device according to claim 1, wherein the charge transporting molecule of the monomer (A) has a hole transporting property. 3. The organic light emitting device according to claim 2, wherein the charge transporting molecule of the monomer (A) contains a carbazole derivative. 4. The organic light emitting device according to claim 2, wherein the charge transporting molecule of the monomer (A) contains an aromatic amine compound. 5. The organic light-emitting device according to claim 1, wherein the charge-transporting molecule of the monomer (A) has an electron-transporting property. 6. The organic light emitting device according to claim 5, wherein the charge transporting molecule of the monomer (A) contains an oxadiazole derivative. 7. The organic light emitting device according to claim 5, wherein the charge transporting molecule of the monomer (A) contains a triazole derivative. 8. The organic light emitting device according to claim 5, wherein the charge transporting molecule of the monomer (A) contains a quinolinol complex or a derivative thereof. 9. The organic light emitting device according to claim 1, wherein the light emitting molecule of the monomer (B) contains an oxadiazole derivative. 10. The luminescent molecule of the monomer (B),
The organic light-emitting device according to any one of claims 1 to 8, comprising a quinolinol complex or a derivative thereof. 11. The luminescent molecule of the monomer (B),
A coumarin derivative is contained therein.
9. The organic light-emitting device according to any one of 8. 12. The luminescent molecule of the monomer (B),
The organic light-emitting device according to claim 1, further comprising a phenoxazone derivative. 13. The luminescent molecule of the monomer (B),
9. The organic light emitting device according to claim 1, comprising rubrene or a derivative thereof. 14. The luminescent molecule of the monomer (B),
The organic light-emitting device according to any one of claims 1 to 8, comprising perylene or a derivative thereof. 15. The luminescent molecule of the monomer (B),
The organic light-emitting device according to any one of claims 1 to 8, comprising quinacridone or a derivative thereof. 16. The luminescent molecule of the monomer (B),
The organic light-emitting device according to claim 1, further comprising an anthracene derivative. 17. The luminescent molecule of the monomer (B),
A styryl derivative is contained.
9. The organic light-emitting device according to any one of 8. 18. An organic light emitting device having at least one light emitting layer between a positive electrode and a negative electrode, wherein the light emitting layer contains a monomer (C) containing a light emitting molecule and another light emitting molecule. An organic light-emitting device comprising a copolymer comprising a monomer (D). 19. The luminescent molecule of the monomer (C),
The organic light emitting device according to claim 18, wherein the organic light emitting device is a substance capable of sustaining injection of holes and electrons. 20. The luminescent molecule of the monomer (D),
19. The light emitting device emits light by energy transfer from the excited state of the luminescent molecule of the monomer (C).
Or an organic light-emitting device according to item 19. 21. The luminescent molecule of the monomer (D),
The organic light-emitting device according to any one of claims 18 to 20, wherein the organic light-emitting device has a negative reduction potential smaller than that of the light-emitting molecule of the monomer (C). 22. The luminescent molecule of the monomer (C),
The organic light-emitting device according to any one of claims 18 to 21, comprising an oxadiazole derivative. 23. The luminescent molecule of the monomer (C),
The organic light-emitting device according to any one of claims 18 to 21, comprising a quinolinol complex or a derivative thereof. 24. The luminescent molecule of the monomer (C),
The organic light-emitting device according to claim 18, further comprising an anthracene derivative. 25. The luminescent molecule of the monomer (D),
19. A coumarin derivative is contained.
25. The organic light-emitting device according to any one of the above items. 26. The luminescent molecule of the monomer (D),
The organic light-emitting device according to any one of claims 18 to 24, comprising a phenoxazone derivative. 27. The luminescent molecule of the monomer (D),
The organic light-emitting device according to any one of claims 18 to 24, comprising rubrene or a derivative thereof. 28. The luminescent molecule of the monomer (D),
The organic light-emitting device according to any one of claims 18 to 24, comprising perylene or a derivative thereof. 29. The luminescent molecule of the monomer (D),
The organic light-emitting device according to any one of claims 18 to 24, comprising quinacridone or a derivative thereof. 30. The luminescent molecule of the monomer (D),
19. A composition containing a styryl derivative.
25. The organic light-emitting device according to any one of the above items. 31. The organic light-emitting device according to claim 1, wherein the light-emitting layer contains a low-molecular charge transport material. 32. The organic light emitting device according to claim 1, further comprising a hole injection layer between the positive electrode and the light emitting layer. 33. The organic light emitting device according to claim 1, further comprising an electron injection layer between the cathode and the light emitting layer.