JP2003163086A - Organic el cell and organic el display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL cell and an organic EL display to realize a large area, high definition, low cost, and high light emission efficiency at the same time. <P>SOLUTION: The organic EL cell 10 comprises, a Hall injection layer 16, a phosphorescent light emitting layer 18, and a cathode 20 laminated in this order on the board 12 with an anode 14. The Hall injection layer 16 contains organic solvent-insoluble macromolecules as a main component. The organic solvent-insoluble macromolecules are made by polymerization of low molecular molecules and high molecular molecules existent in materials forming the Hall injection layer 16 in the process of forming the Hall injection layer 16. The organic solvent-insoluble macromolecules are insoluble in an organic solvent utilized in pasting and forming the light emitting layer 18. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic EL element and an organic EL display.

[0002]

2. Description of the Related Art Research and development of organic EL devices (organic electroluminescent devices) using a luminescent polymer soluble in an organic solvent as a material have been actively carried out for phenylene vinylene-based and fluorene-based polymers. There is.

In this case, as a film forming method, a coating method such as a spin coating method, a printing method or an ink jet method is adopted. In particular, the inkjet method is expected as a practical pixel forming method for a full-color display, and a small full-color prototype panel has already been proposed.

Organic EL using such a luminescent polymer
The element (hereinafter, also referred to as a polymer EL element) is more suitable for a display material than an organic EL element formed by a vacuum deposition method, which uses a light emitting low molecule described later as a material. This is advantageous in that a large-area, high-definition display can be obtained and that the display can be obtained at low cost.

On the other hand, an organic EL element using a light-emitting low molecule as a material (hereinafter, this may be referred to as a low-molecular EL element) is also considered as a means for realizing an extremely high luminous efficiency. , Research is becoming more active. This utilizes phosphorescence, which is light emission from the triplet excited state of an organic compound, and as such an organic compound,
For example, metal complexes of platinum and iridium have been reported. A low-molecular-weight EL device using a phosphorescent organic compound has an emission quantum efficiency of about 8%, which exceeds the emission quantum efficiency of about 5% that an EL device using a conventional fluorescent compound has. Very recently, it has been reported that an emission quantum efficiency as high as 15% can be achieved by devising the device configuration (Appl. Phys. Lett., Vol. 77, pp. 904 (200
0)).

A doped polymer EL device in which the above-mentioned low molecular weight phosphorescent organic compound is dispersed in a polymer has been reported (Appl. Phys. Lett., Vol. 77, pp. 904 (2000)). . For example, it is said that an element obtained by doping an N-vinylcarbazole polymer (PVK polymer) with an iridium complex can obtain an emission quantum efficiency of about 4%. Such a doped polymer EL device has a large area, which is an advantage of each of the polymer EL device and the low molecule EL device described above.
It can be said that the device can realize high definition and low cost and high light emission efficiency at the same time. Also,
Most recently, phosphorescence emission from a polymer in which the side chain of a polymer is substituted with a phosphorescent organic compound has also been reported (ICEL-3, Abstr
act, O-18 (2001)).

By the way, an EL element using a polymer generally needs to be applied with a high voltage in order to obtain light emission, and this also applies to the above-mentioned doped polymer EL element. In order to improve this problem, for example, a mixture of polyethylenedioxyphenylene and porsulphonic acid (hereinafter PE) is provided between the anode and the light emitting layer.
Notated as DOT: PPS. (3) is inserted as a hole injecting layer and injected light is emitted to realize light emission at a low applied voltage.

[0008]

However, the PED
Since OT: PPS is a high conductor having a very small band gap, energy generated by the excited state of the light emitting component of the light emitting layer moves to the interface with PEDOT: PPS and disappears, resulting in a decrease in light emitting efficiency. To do.

On the other hand, the band gap is large,
In other words, an insulating hole injection material such as triphenyldiamine (TPD) or its derivative α
The use of triphenylamine dimers such as -NPD has been investigated. However, when forming a light emitting layer by a coating method using a solution of an organic solvent in which a polymer light emitting material is dissolved on a hole injection layer formed using these materials,
There is a problem that the hole injection layer is attacked by the organic solvent.

The present invention has been made in view of the above problems, and an organic EL element and an organic EL capable of simultaneously achieving a large area, high definition, low cost, and high luminous efficiency. It is intended to provide a display.

[0011]

The organic EL device according to the present invention is an organic EL device having an anode, a hole injection layer, a light emitting layer and a cathode, the hole injection layer containing an organic solvent insoluble polymer as a main component. And the light emitting layer contains a phosphorescent organic compound.

Thus, when the phosphorescent light-emitting layer is formed by the coating method, the hole injection layer is not attacked by the organic solvent, and the stable hole injection layer can be formed, resulting in a large area and high definition. Thus, it is possible to obtain an organic EL element that can simultaneously realize high cost and low cost, and high luminous efficiency. Further, since it can be handled at low voltage and low current, it is possible to obtain an organic EL element having a long life. Such an organic EL element can be suitably applied to a display, a lighting fixture, a light source, or the like.

In this case, when the light emitting layer is formed by applying a solution in which the material containing the phosphorescent organic compound is dissolved in an organic solvent, the light emitting layer is formed more easily and cheaply than the vapor deposition method. can do.

Further, in this case, when the organic solvent insoluble in the organic solvent-insoluble polymer is the organic solvent used for forming the light emitting layer by coating, the above-described effects of the present invention can be suitably obtained.

In this case, it is preferable that the organic solvent-insoluble polymer is a polymer obtained by polymerizing one or more organic compounds.

At this time, the polymer is the above 1 or 2
It is produced by applying the above organic compounds by a coating method to form a coating film, and then polymerizing the one or more organic compounds to form the coating film in the hole injection layer. As a result, the hole injection layer can be formed easily and inexpensively as compared with the vapor deposition method.

At this time, the organic compound is a low molecular weight monomer, and the polymer forms the hole injection layer by a vacuum vapor deposition polymerization method using the low molecular weight monomer as a vapor deposition material. Once generated, it is preferable.

At this time, it is preferable that the organic solvent-insoluble polymer contains an aromatic tertiary amine structure.

The organic EL display according to the present invention is characterized in that the above organic EL elements are formed in a matrix on a flexible substrate.

As a result, a large area, high definition, low cost, and high luminous efficiency can be realized at the same time, and a long-life and flexible organic EL display can be obtained. .

In this case, the light emitting layer of the organic EL element is
When formed by the coating method, it is possible to obtain an organic EL display which is easier to manufacture and cheaper than the vapor deposition method. Further, an organic EL display having a large screen suitable as a color display can be obtained.

In this case, if a pixel is formed by the organic EL element and two or more thin film transistors,
An organic EL display having a high response speed can be obtained.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the organic EL element and the organic EL display according to the present invention (hereinafter referred to as the present embodiment examples) will be described below.

First, the organic EL element according to this embodiment will be described.

As shown in FIG. 1, the organic EL element 10 according to the present embodiment has a hole injection layer 16, a light emitting layer 18, and a cathode 20 in this order on a substrate 12 on which an anode 14 is formed. It has a laminated structure.

The hole injection layer 16 contains an organic solvent insoluble polymer as a main component.

The organic solvent-insoluble polymer is produced by reacting the chemical structural components present in the material forming the hole injection layer 16 with each other in the process of forming the hole injection layer 16 to polymerize the organic solvent insoluble polymer. It has been changed into a molecule.

Preferred examples of the above chemical structural component include triphenylamine (1) and carbazole (2), which are tertiary amines represented by the following formula, and pyrazoline.

[0029]

[Chemical 1] In addition to the above, the chemical structure component may include an aromatic ring such as thiophene, phenylene, p-phenylene vinylene, and fluorene, a condensed ring or a hetero ring.

The organic compound containing one or more kinds of the above chemical structures is used as a material, and a chemical reaction is performed to polymerize these organic compounds to obtain a polymer, and the hole injection layer 16 is formed by the process. The hole injection layer 16 containing a solvent-insoluble polymer as a main component can be obtained.

That is, for example, a triphenylamine dimer (MS having reaction sites at both ends as shown by the following formula)
Bayerl, Macromol, Rapid Commun. Vol. 20, pp. 224 (1999))
Was used as a material, and a solution prepared by dissolving this triphenylamine dimer in an organic solvent and adding an appropriate reaction initiator was applied to the anode 14 provided on the substrate 12 as described later to obtain the solution. A method of irradiating the coating film (layer) with ultraviolet rays can be used.

[0032]

[Chemical 2] Further, as an organic compound similar to the above, a triphenylamine dimer having a reaction site represented by the following formula can also be used.

[0033]

[Chemical 3] This makes it possible to obtain a hole injection layer made of a polymer in which a triphenylamine dimer is three-dimensionally bound. This polymer is insoluble in a general-purpose organic solvent, in other words, an organic solvent-insoluble polymer. Here, the organic solvent in which the polymer is insoluble is preferably an organic solvent used when the light emitting layer described below is formed by coating. That is,
The organic solvent-insoluble polymer is a polymer that is insoluble in the organic solvent used when forming the light emitting layer by coating. This point is the same for the other examples below.

Also, using a triphenylamine-containing polyetherketone, which is a polymer represented by the following formula, as a material,
When this is irradiated with ultraviolet rays, a cross-linking reaction occurs between the polyetherketones containing triphenylamine, and it can be made into an organic solvent-insoluble polymer (Proceedings of the 54th SPSJ Academic Lecture Meeting No.3, pp.445). (1993)).

[0035]

[Chemical 4] In the above-mentioned polymerization method using ultraviolet rays, it is essential that the formed polymer retains a triphenylamine structure, which is a unit structure (component) of hole transport, depending on the properties of the polymer material used. Then, the ultraviolet irradiation conditions, the heating conditions during the thermal polymerization, etc. are appropriately selected. This also applies to other methods described below.

In addition, for example, two kinds of monomers represented by the following formula (3), which have reaction sites at both ends, are simultaneously vacuum-deposited and polymerized on the anode provided on the substrate to form the following formula. A polymer containing a triphenylamine structure represented by the following formula (5) can be obtained by further performing heat treatment in a vacuum via the form of the intermediate compound represented by the formula (4). At this time, a polymer having a predetermined structure can be obtained by controlling the vapor deposition rates of the two kinds of monomers to 1: 1 (the same rate). The polymer obtained has a rigid molecular structure and is insoluble in organic solvents. This method is called a vacuum vapor deposition polymerization method.

[0037]

[Chemical 5] In addition, the following formula may be used as the vapor deposition polymerization method similar to the above.

[0038]

[Chemical 6] In addition, the method for obtaining a polymer by reacting an organic compound when forming the hole injection layer and the method for using the polymer as the material for forming the hole injection layer are not limited to those described above. The hole injection layer 16 may be formed by a coating method by directly using a polymer that has water and is soluble in alcohol. Such water-soluble or alcohol-soluble polymers are generally insoluble in organic solvents. As the polymer, for example, a polymer having an ionic functional group such as a sulfonium group, a hydroxyl group, an ammonium group or a carboxyl group, or a functional group such as alkoxy can be preferably used.

The light emitting layer 18 contains a phosphorescent organic compound as a light emitting component.

The above phosphorescent organic compound is, for example, a metal complex organic compound containing a transition metal or a rare earth metal, is soluble in an organic solvent, and can form a uniform thin film from an organic solvent solution. In particular, a high molecular weight organic compound is preferable. In this case, a mixture of a high molecular weight organic compound and a low molecular weight phosphorescent compound may be used, or the high molecular weight organic compound itself may be directly bonded to the fluorescent compound. As a typical chemical structure thereof, a metal complex of iridium or platinum represented by the following formula is suitable.

[0041]

[Chemical 7] The substrate 12 is made of a transparent material. As the substrate made of a transparent material, in addition to a general-purpose glass substrate, a flexible substrate such as a plastic film or a metal film can be used.

When the plastic film is used, a material excellent in heat resistance, dimensional stability, solvent resistance, electric insulation, workability, low air permeability and low hygroscopicity is used. Examples of such a material include polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyether sulfone, polyarylate, and polyimide.

When using a metal film, an insulating layer is formed on the surface of the metal film which is in contact with the anode.

A flexible organic EL element 10 can be obtained by using such a flexible substrate 12.

It is preferable to provide a moisture permeation preventive layer (gas barrier layer) on any one surface or both surfaces of the substrate 12. As the material of the moisture permeation preventive layer, inorganic substances such as silicon nitride and silicon oxide are suitable. The moisture permeation preventive layer can be formed by a high frequency sputtering method or the like.

If necessary, a hard coat layer or an undercoat layer may be provided.

The anode 14 is formed of a light transmissive material.
As the light-transmitting material, in addition to general-purpose ITO, indium oxide, tin oxide, indium oxide-zinc oxide alloy, and the like can be preferably used. Further, the anode 14 is
It may be a thin film of a metal such as gold, platinum or silver magnesium.

As the material of the cathode 20, it is preferable to use an alkali metal having a low work function such as lithium or potassium, or an alkaline earth metal such as magnesium or calcium, from the viewpoint of excellent electron injection. Stable aluminum is also suitable as a material for the cathode 20.

Further, the cathode 20 may be a layer containing two or more kinds of materials in order to achieve both stability and electron injectability, and those materials are disclosed in JP-A-2-15595 and JP-A-2-15595. What was described in 5-121172 publication etc. can be used.

When aluminum is used for the cathode 20, the thickness of about 0.01 to 100 nm of cesium, barium, calcium, strontium or another alkali metal or alkaline earth metal is used at the interface between the aluminum and the light emitting layer 18. A thin layer may be provided.

The organic E according to the embodiment described above
A method of manufacturing the L element 10 will be described.

Each of the anode 14 and the cathode 20 can be formed by a known method such as a vacuum vapor deposition method, a sputtering method, an ion plating method. Further, the anode 14 and the cathode 20, and particularly the anode 14 among them, are preferably patterned by chemical etching such as photolithography or physical etching such as laser. Alternatively, a mask may be overlapped and patterned by vacuum vapor deposition, sputtering, or the like.

As described above, the hole injection layer 16 may be formed by a coating method using a solvent prepared by dissolving an organic compound in an organic solvent, a vapor deposition method, a vacuum vapor deposition polymerization method, etc., depending on the form of the organic solvent used. It can be formed by a method appropriately selected from the film forming methods.

Among the above methods, the use of the coating method makes it possible to form the hole injection layer 16 more easily and cheaply than the vapor deposition method. At this time, as the organic solvent, for example, chloroform, xylene, toluene, hexane, dichloromethane or the like can be used. The hole injection layer 16 formed by coating contains a polymer of the organic compound as a main component. This polymer is formed in a form insoluble in an organic solvent used at least when forming a light emitting layer 18 described later by a coating method.

The light emitting layer 18 is formed by a coating method such as a spin coating method, a printing method or an ink jet method. In this case, the phosphorescent organic compound is applied using a solution in which an organic solvent such as chloroform is dissolved. The coating method is
It is preferable because the manufacturing cost is low. Among them, particularly in the inkjet method, when forming a large number of pixels, each pixel can be separately coated with different kinds of organic compounds, so that full color can be easily realized. When the phosphorescent organic compound has a relatively low molecular weight, it may be formed by a vacuum vapor deposition method.

In order to improve the luminous efficiency, a laminated structure having an electron transport layer or a hole transport layer together with the light emitting layer 18 may be used, and an electron injection layer may be further provided.

Organic EL element 10 according to the present embodiment
When forming the phosphorescent emitting layer 18 by a coating method,
The hole injection layer 16 is not attacked by the organic solvent, and the stable hole injection layer 16 can be formed.
A large area, high definition, low cost, and high luminous efficiency can be realized at the same time. Further, since it can be handled at low voltage and low current, it is possible to obtain an organic EL element having a long life.

Next, the organic EL display according to this embodiment will be described.

The organic EL display according to this embodiment includes the organic EL element 10 according to this embodiment. The organic EL element 10 uses, for example, a plastic film as the substrate 12.

In the organic EL display according to the present embodiment, two or more thin film transistors are arranged in each pixel unit of the organic EL element 10 according to the present embodiment, and the organic EL display is activated by addressing and driving by the thin film transistors. It is a matrix type display.
At this time, an organic transistor is preferably used as the thin film transistor.

The above-mentioned organic EL display is preferably formed by a coating method, particularly an ink jet method or a printing method.

The organic EL display according to the present embodiment can simultaneously realize a large area, high definition, low cost, and high luminous efficiency, and has a long life and high cost. Has a response speed.

The organic EL display according to the present embodiment is flexible because it uses the organic transistor and the flexible substrate in combination.

Further, in the organic EL display according to this embodiment, since the light emitting layer of the organic EL element is formed by the coating method, a large screen suitable as a color display can be obtained easily and inexpensively.

[0065]

EXAMPLES The present invention will be further described with reference to examples.
The present invention is not limited to the embodiments described below.

A glass substrate having an ITO film (anode) having a thickness of 150 nm formed on its upper surface was prepared.

An organic compound having a triphenylamine structure represented by the following formula and 4- (thio-phenoxyphenylene) diphenyl-sulfonium hexafluoroantimolarate as a reaction initiator were dissolved in chloroform to obtain 1% by mass. A solution was prepared.

[0068]

[Chemical 8] This solution was applied onto the ITO film by spin coating to form a film having a thickness of about 100 nm.

After sufficiently drying the formed glass substrate,
A hole injection layer was obtained by irradiating a glass substrate with a mercury lamp to cause a polymerization reaction in the above-mentioned organic compound during film formation and change it into a polymer (polymer) insoluble in an organic solvent.

A hole-transporting polymer (PVK) represented by the following formula (6), a phosphorescent metal complex represented by the following formula (7), and an electron-transporting polymer represented by the following formula (8) are prepared. A solution dissolved in dichloroethane was applied on the hole injection layer by spin coating to form a light emitting layer having a thickness of 100 nm. At this time, the content of the phosphorescent metal complex (7) in the light emitting layer was 8% by mass. Furthermore, a thickness of 10 is formed on the light emitting layer.
nm of calcium and 100 nm of thickness of aluminum were continuously vacuum-deposited to form a cathode, and an organic EL device (polymer EL device) was obtained.

[0071]

[Chemical 9] When a voltage was applied to the organic EL device, green light emission of the phosphorescent polymer was obtained at a voltage of 4V. At this time, 6%
The emission quantum efficiency of was obtained.

[0072]

According to the organic EL device of the present invention, the hole injection layer contains an organic solvent-insoluble polymer as a main component, and the light emitting layer contains a phosphorescent organic compound. It is possible to realize high efficiency and high emission efficiency at the same time. In addition, it is possible to obtain a long-life organic EL element.

Further, according to the organic EL element of the present invention, the light emitting layer is formed by applying a solution in which a material containing a phosphorescent organic compound is dissolved in an organic solvent. The light emitting layer can be formed at low cost.

According to the organic EL device of the present invention, the polymer is formed by coating one or more organic compounds by a coating method to form a coating film, and then polymerizing the one or more organic compounds. The hole injection layer is formed by forming the coating film on the hole injection layer, so that the hole injection layer can be formed easily and inexpensively as compared with the vapor deposition method.

Further, according to the organic EL display of the present invention, since the above organic EL elements are formed in a matrix on the flexible substrate, the area is increased, the definition is increased, and the cost is reduced. High luminous efficiency can be realized at the same time, and it has a long life and is flexible.

Further, the organic EL display according to the present invention has a high response speed because the pixel is formed by the organic EL element and two or more thin film transistors.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an organic EL element according to an embodiment of the present invention.

[Explanation of symbols]

10 Organic EL element 12 substrates 14 Anode 16 hole injection layer 18 Light-emitting layer 20 cathode

Claims (9)

[Claims] 1. An organic EL device having an anode, a hole injection layer, a light emitting layer and a cathode, wherein the hole injection layer contains an organic solvent insoluble polymer as a main component, and the light emitting layer contains a phosphorescent organic compound. An organic EL device characterized in that 2. The organic EL device according to claim 1, wherein the light emitting layer is formed by applying a solution in which a material containing the phosphorescent organic compound is dissolved in an organic solvent. 3. The organic EL device according to claim 2, wherein the organic solvent in which the organic solvent-insoluble polymer is insoluble is an organic solvent used when forming and forming the light emitting layer. 4. The organic EL device according to claim 1, wherein the organic solvent-insoluble polymer is a polymer obtained by polymerizing one or more organic compounds. 5. The polymer is applied with the one or more organic compounds by a coating method to form a coating film,
5. The organic EL device according to claim 4, wherein the organic EL device is produced by polymerizing the one or more organic compounds to form the coating film on the hole injection layer. 6. The organic compound is a low molecular weight monomer, and the polymer is produced by forming the hole injection layer by a vacuum vapor deposition polymerization method using the low molecular weight monomer as a vapor deposition material. The organic EL element according to claim 4, wherein 7. The organic solvent-insoluble polymer is aromatic 3
The organic EL device according to any one of claims 1 to 6, comprising a primary amine structure. 8. An organic EL display comprising the organic EL element according to claim 1 formed in a matrix on a flexible substrate. 9. The active matrix organic EL display according to claim 8, wherein a pixel is formed by the organic EL element and two or more thin film transistors.