JP2003007467A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescence element, which has high luminescence efficiency, by making luminescence of high luminosity possible. SOLUTION: Concerning to the organic electroluminescense element, which has a luminescence layer, which is formed between both electrode layers of a positive electrode layer and a negative electrode layer, and has a host agent and a dope agent, which emits phosphorescence, a bipolar nature is provided by using oxadiazole group expressed with formula 1 or an electron transportation nature substance, which has triazole group expressed with formula 2, and using an electron hole transportation nature substance, which has carbazolyl group expressed with formula 3, as a host agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device capable of emitting light with high brightness.

[0002]

2. Description of the Related Art Conventionally, from US Pat. No. 6,097,147, there is known an organic electroluminescence device having a multi-layered structure having a light emitting layer containing a substance emitting phosphorescence.

In this case, the theoretical limit of the internal quantum efficiency in the case of light emission by the excited singlet state, that is, in the case of emitting light only by using fluorescence, is 25%, whereas the light emission by phosphorescence is in the triplet state. Since the excitation energy of 1 contributes to light emission, the theoretical limit of the internal quantum efficiency may be considered to be 100%. Therefore, it can be expected that the light emission efficiency defined by the light emission luminance with respect to the drive voltage is improved.

By the way, in the embodiment of the above-mentioned conventional example,
Carbazole biphenyl (hereinafter also referred to as CBP) shown in [Chemical Formula 24] was used as a host agent in the light emitting layer, and as a doping agent in the light emitting layer,

[0005]

[Chemical 29]

2, 3, 7, 8, 12, shown in [Chemical Formula 29]
Using 13,17,18-octaethyl-21H, 23H-platinum (II) porphine (hereinafter also referred to as PtOEP), CBP as a host agent acts as an exciton to cause PtOEP as a dopant to emit phosphorescence.

However, the CBP has hole mobility due to the carbazolyl group contained in the structure. Therefore, when the holes and electrons injected from the respective electrode layers of the anode layer and the cathode layer recombine with each other and act as excitons, they should originally diffuse into the light emitting layer. CBP, which is a host agent, is unevenly distributed on the cathode layer side in the light emitting layer. Along with this, the light emitting region is also concentrated at the interface portion with the thin film layer (hole blocking layer, electron transporting layer, etc.) on the cathode layer side adjacent to the light emitting layer, and sufficient emission brightness may not be obtained. Such a problem becomes particularly noticeable as the driving voltage of the organic electroluminescence element increases, and is shown as a decrease in quantum efficiency. Then, this becomes a factor that hinders the desired improvement of the luminous efficiency.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an organic electroluminescence device which enables high brightness light emission and has high light emission efficiency.

[0009]

In order to solve the above problems, the present invention comprises a light emitting layer formed between both electrode layers of an anode layer and a cathode layer and having a host agent and a dopant emitting phosphorescence. In the organic electroluminescence device, the host agent is constructed so as to have a bipolar property, that is, have a dual polarity of radical cationization and radical anionization. Since this one has both hole mobility and electron mobility, it does not concentrate on the specific interface side in the light emitting layer,
The emission brightness can be improved.

Further, in this case, if a hole transporting substance and an electron transporting substance are used as the host agent, the host agent is surely provided with a bipolar property, that is, a double polarity which easily forms radical cation and radical anion. it can.

Further, in this case, the electron transporting substance used as the host agent is preferably composed of a compound having an oxadiazole group represented by the structural formula [Chemical Formula 1].

As a compound having an oxadiazole group represented by the above [Chemical formula 1], a compound represented by the following [Chemical formula 2]
-(4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, (hereinafter P
Also called BD. ), 2,5-bis (1-
Naphthyl) -1.3.4-oxadiazole (hereinafter B
Also called ND. ), 2,5-bis (4-
Biphenylyl) -1,3,4-oxadiazole (hereinafter also referred to as BBD), 1,3,5-tri (5- (4-tert-butylphenyl) -1,3,4 shown in [Chemical Formula 5]
-Oxadiazole) phenyl (hereinafter also referred to as OXD-1), 1,3-di (5- (4-ter) shown in [Chemical Formula 6]
t-butylphenyl) -1,3,4-oxadiazole) phenyl (hereinafter also referred to as OXD-7), or
It is possible to use one or more of the oxadiazole-based polymer compounds represented by [Chemical Formula 7] or [Chemical Formula 8].

It is also preferable to use a compound having a triazole group represented by the structural formula [Chem. 9] as the electron transporting substance used as the host agent.

The compound having a triazole group represented by the above [Chemical formula 9] is represented by the following [Chemical formula 10]:
(4-biphenylyl) -5- (4-tert-butylphenyl) -4-phenyl-1,2,4-triazole (hereinafter also referred to as TAZ), 3, shown in [Chemical Formula 11]
4,5-tri (1-naphthyl) -1,2,4-triazole, 3,5-di (4-biphenylyl) -4-phenyl-1,2,4-triazole shown in [Chemical Formula 12], 13-] 4- (1-naphthyl) -3,5-diphenyl-1,2,4-triazole shown in [Chemical Formula 14]
3,5-tri (5- (4-tert-butylphenyl)
-1-Phenyl-1,3,4-triazole) phenyl, 1,3-di (5- (4-tert) shown in [Chemical Formula 15]
-Butylphenyl) -1-phenyl-1,3,4-triazole) phenyl, or [Chemical Formula 16] to [Chemical Formula 1]
It is possible to use one or more of the triazole-based polymer compounds represented by the general formula [8].

Further, for these electron transporting substances,
As the hole-transporting substance used for the host agent,
It is preferable to use a compound having a carbazolyl group represented by [9].

As the compound having a carbazolyl group, carbazole represented by [Chemical Formula 20], [Chemical Formula 21]
N methylcarbazole represented by [Chemical Formula 22], N vinylcarbazole represented by [Chemical Formula 23], N phenylcarbazole represented by [Chemical Formula 24], CBP represented by [Chemical Formula 24], poly (N-vinylcarbazole) represented by [Chemical Formula 25] (hereinafter PVK It is also possible to use one or more of the polycarbazole compounds represented by the general formula [Chemical Formula 26].

When a compound represented by the general formula [Chemical formula 27] or [Chemical formula 28] is used as a phosphorescent emitting dopant for the host agent having a bipolar property as described above, such a dopant is used. Emits phosphorescence when excited by a host agent that is diffused / dispersed in the light-emitting layer, so that in an organic electroluminescent element including a light-emitting layer having these host agent and dopant, the light-emitting region is not unevenly distributed. Highly bright light can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a basic structure of an organic electroluminescence device having a device structure laminated in multiple layers for the purpose of improving luminous efficiency. The element structure of the organic electroluminescence element is such that each of the hole transport layer 20, the electron block layer 30, the light emitting layer 40, the hole block layer 50, and the electron transport layer 60 is formed on the anode layer 10 formed on a substrate (not shown). The thin film layer has a multi-layered structure in which the anode layer 10 and the cathode layer 70 are sequentially laminated between both electrode layers, and the light emitting layer 40 includes a light emitting layer doping agent 41 and a light emitting layer host agent 42. Has been done.

In the element structure shown in FIG. 1, for the anode layer 10, a transparent conductive substance formed on a transparent insulating support such as a glass substrate is used, and its material is tin oxide or oxide. Indium, indium tin oxide (I
Conductive oxides such as TO) or metals such as gold, silver and chromium, inorganic conductive substances such as copper iodide and copper sulfide,
Conductive polymers such as polythiophene, polypyrrole, and polyaniline can be used.

When the cathode layer 70 is made of a transparent material, the anode layer 10 may be made of an opaque material.

In addition, in the device structure shown in FIG.
The cathode layer 70 includes lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, boron, aluminum, copper, silver,
A simple substance such as gold or an alloy can be used. Further, these may be laminated and used. It can also be formed by a wet process using tetrahydroaluminate. In this case, examples of the tetrahydroaluminate used for the cathode layer 70 include lithium aluminum hydride, potassium aluminum hydride, magnesium aluminum hydride, and aluminum calcium hydride. Among these, lithium aluminum hydride is particularly excellent in the electron injection property into the electron transport layer.

The hole transport layer 20 is a layer for transporting holes injected from the anode layer 10, and is an organic layer containing a hole transporting organic substance. As an example of the hole transport layer organic compound, PVK represented by [Chemical Formula 25], a polycarbazole compound represented by [Chemical Formula 26],

[0023]

[Chemical 30]

Poly (para-phenylene vinylene) shown in [Chemical Formula 30],

[0025]

[Chemical 31]

It is preferably composed of a polymer such as N-phenylpolycarbazole represented by the chemical formula [31]. Alternatively, carbazole represented by [Chemical Formula 20], N methylcarbazole represented by [Chemical Formula 21], N vinylcarbazole represented by [Chemical Formula 22], N phenylcarbazole represented by [Chemical Formula 23],
CBP shown in [Chemical 24],

[0027]

[Chemical 32]

N, N'-diphenyl-shown in [Chemical Formula 32]
N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (hereinafter also referred to as TPD),

[0029]

[Chemical 33]

N, N'-diphenyl-shown in [Chemical Formula 33]
N, N′-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (hereinafter, also referred to as NPD)

[0031]

[Chemical 34]

4,4'-bis (10-
Phenothiazinyl) biphenyl,

[0033]

[Chemical 35]

Examples include copper phthalocyanine shown in [Chemical Formula 35].

Further, the electron block layer 30 is the cathode layer 70.
Electrons injected into the light emitting layer 40 from the anode layer 10 as they are.
It is a layer for blocking electrons in order to prevent it from passing through, and is composed of an electron blocking substance. As the electron blocking substance, for example, PV shown in [Chemical Formula 25]
K, poly (para-phenylene vinylene) represented by [Chemical Formula 30], CBP represented by [Chemical Formula 24], TPD represented by [Chemical Formula 32], NPD represented by [Chemical Formula 33], represented by [Chemical Formula 34] 4,4′-bis (10-phenothiazinyl) biphenyl,

[0036]

[Chemical 36]

2,4,6-triphenyl-1,3,5-triazole represented by the formula:

[0038]

[Chemical 37]

Examples thereof include Florene shown in [Chemical Formula 37].

Further, the light emitting layer 40 has a doping agent 41 and a host agent 42, and in order to disperse the doping agent 41 and the host agent 42 uniformly, it is possible to add a binder polymer.

The host agent 42 is used for the anode layer 10 and the cathode layer 7.
A substance which is activated when the holes and electrons respectively injected from 0 are recombined in the light emitting layer 40 and acts as excitons, and is a PBD shown in [Chemical Formula 2] and a BBD shown in [Chemical Formula 3].
ND, BBD shown in [Chemical Formula 4], OXD- shown in [Chemical Formula 5]
1, OXD-7 shown in [Chemical Formula 6], or an oxadiazole-based polymer compound represented by [Chemical Formula 7] or [Chemical Formula 8], TAZ shown in [Chemical Formula 10], and 3 shown in [Chemical Formula 11]. ，
4,5-tri (1-naphthyl) -1,2,4-triazole, 3,5-di (4-biphenylyl) -4-phenyl-1,2,4-triazole shown in [Chemical Formula 12], 13-] 4- (1-naphthyl) -3,5-diphenyl-1,2,4-triazole shown in [Chemical Formula 14]
3,5-tri (5- (4-tert-butylphenyl)
-1-Phenyl-1,3,4-triazole) phenyl, 1,3-di (5- (4-tert) shown in [Chemical Formula 15]
-Butylphenyl) -1-phenyl-1,3,4-triazole) phenyl,

[0042]

[Chemical 38]

[0043]

[Chemical Formula 39]

[0044]

[Chemical 40]

Triazole polymer compounds represented by [Chemical Formula 38] to [Chemical Formula 40], carbazole represented by [Chemical Formula 20], N-methylcarbazole represented by [Chemical Formula 21],
N vinylcarbazole represented by [Chemical Formula 22], N phenylcarbazole represented by [Chemical Formula 23], CB represented by [Chemical Formula 24]
P, poly (N-vinylcarbazole) represented by [Chemical Formula 25]
(Hereinafter also referred to as PVK), a carbazole compound such as a polycarbazole compound represented by the general formula [Chemical Formula 26],

[0046]

[Chemical 41]

(R in the chemical formula [Chemical Formula 41] independently represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group,
Indicates any of the heterocyclic groups. ) Show. ) A polyfluorene compound having [Chemical Formula 41] as a repeating unit, and the like.

It is also possible to use two or more of these host agents in combination. Such combined use is, for example, an oxadiazole-based compound represented by [Chemical Formula 2] to [Chemical Formula 8] having an electron transporting property or [Chemical Formula 10] to [Chemical Formula 15] and [Chemical Formula 38].
When a carbazole compound represented by [Chemical formula 20] to [Chemical formula 26] having a hole-transporting property is used in combination with the triazole-based compound represented by [Chemical formula 40], a specific interface side of the light emitting region is obtained. There is an effect that uneven distribution of can be prevented.

On the other hand, the dopant 41 of the light emitting layer 40 is a substance which emits phosphorescence by the excitation energy of the host agent 42 which is an exciton,

[0050]

[Chemical 42]

A tri (2phenylpyridine) iridium complex represented by [Chemical Formula 42] (hereinafter also referred to as Ir (ppy) ₃ ),

[0052]

[Chemical 43]

[0053]

[Chemical 44]

[0054]

[Chemical formula 45]

[0055]

[Chemical formula 46]

[0056]

[Chemical 47]

[0057]

[Chemical 48]

(In the chemical formula [Chemical Formula 48], acac is

[0059]

[Chemical 49]

A functional group represented by [Chemical Formula 49] is shown. following
The same applies to the chemical formulas shown in [Chemical Formula 50] to [Chemical Formula 54]. )

[0061]

[Chemical 50]

[0062]

[Chemical 51]

[0063]

[Chemical 52]

[0064]

[Chemical 53]

[0065]

[Chemical 54]

Examples include iridium complex compounds represented by [Chemical formula 43] to [Chemical formula 48] and [Chemical formula 50] to [Chemical formula 54], PtOEP represented by [Chemical formula 29], and the like.

Examples of the binder polymer that can be added to the light emitting layer 40 include polystyrene, polyvinylbiphenyl, polyvinylphenanthrene, polyvinylanthracene, polyvinylperylene, poly (ethylene-co-vinylacetate), polybutadiene cis and tran.
s, poly (2-vinylnaphthalene), polyvinylpyrrolidone, polystyrene, poly (methylmethacrylate),
Poly (vinyl acetate), poly (2-vinyl pyridine-co-styrene), polyacenaphthylene, poly (acrylonitrile-co-butadiene), poly (benzyl methacrylate), poly (vinyltoluene), poly (styrene-co-) Acrylonitrile), poly (4-vinylbiphenyl), polyethylene glycol and the like.

Further, the hole blocking layer 50 is the anode layer 10
The holes injected into the light emitting layer 40 from the cathode layer 70 as they are.
It is a layer for blocking holes in order to prevent the holes from passing through and is composed of a hole blocking substance. Examples of the hole blocking substance include PB shown in [Chemical Formula 2].
D, BND shown in [Chemical Formula 3], BB shown in [Chemical Formula 4]
D, OXD-1 shown in [Chemical Formula 5], [Chemical Formula 7] or [Chemical Formula 8]
An oxadiazole-based polymer compound as shown in
0] shown in FIG.

[0069]

[Chemical 55]

Bathocuproine (hereinafter referred to as B
Also called CP. ),

[0071]

[Chemical 56]

Tris (8-hydroxyquinolinato) aluminum (hereinafter also referred to as Alq3) shown in [Chemical Formula 56],

[0073]

[Chemical 57]

4,4'-bis (1,1) shown in [Chemical Formula 57]
-Diphenylethenyl) biphenyl (hereinafter DPVBi
Also called. ),

[0075]

[Chemical 58]

4,4'-bis (1,1-bis (4-methylphenyl) ethenyl) biphenyl (hereinafter also referred to as DTVBi) represented by [Chemical Formula 58],

[0077]

[Chemical 59]

[0078]

[Chemical 60]

Examples thereof include triazole polymer compounds represented by [Chemical Formula 59] and [Chemical Formula 60].

The electron transport layer 60 is a layer for transporting electrons injected from the cathode layer 70 and contains an electron transport agent. The electron transport agent is composed of an electron transporting polymer,
Further, a structure containing a low molecule having an electron transport property is possible.

Here, as an example of the electron transporting low molecule,
PBD shown in [Chemical Formula 2], BND shown in [Chemical Formula 3], BBD shown in [Chemical Formula 4], OXD-1 shown in [Chemical Formula 5], OXD-7 shown in [Chemical Formula 6], and shown in [Chemical Formula 10] TAZ, 3,4,5-tri (1-naphthyl) -1, shown in [Chemical Formula 11]
2,4-triazole, 3,5-di (4-biphenylyl) -4-phenyl-1,2,4-triazole shown in [formula 12], 4- (1-naphthyl) -shown in [formula 13]
3,5-diphenyl-1,2,4-triazole, 1,3,5-tri (5- (4-tert-
Butylphenyl) -1-phenyl-1,3,4-triazole) phenyl, 1,3-di (5-
(4-tert-butylphenyl) -1-phenyl-
1,3,4-triazole) phenyl, Alq3 shown in [Chemical Formula 56], DPVBi shown in [Chemical Formula 57], [Chemical Formula 58]
Examples thereof include DTVBi.

As examples of the electron transporting polymer, oxadiazole-based polymer compounds represented by [Chemical formula 7] and [Chemical formula 8], [Chemical formula 38] to [Chemical formula 40] and [Chemical formula 5]
9], a triazole-based polymer compound represented by [Chemical Formula 60],

[0083]

[Chemical formula 61]

(In the chemical formula [Chemical Formula 61], each R independently represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group or a heterocyclic group.] [Chemical Formula 61] is contained in the repeating unit. Examples thereof include polyfluorene compounds.

The element structures shown in FIGS. 2 to 4 can be obtained by modifying the basic structure of the organic electroluminescence element shown in FIG. 1 in order to further improve the luminous efficiency and simplify the structure.

The element structure of the organic electroluminescent element shown in FIG. 2 shows the first embodiment of the organic electroluminescent element of the present invention. Although the electron blocking layer 30 and the hole blocking layer 50 in FIG. 1 are omitted, in FIG. 2, the hole transporting layer 20 has an electron blocking effect and the electron transporting layer 60 has a hole blocking effect. The luminous efficiency can be maintained.

The element structure of the organic electroluminescence element shown in FIG. 3 is the same as the element structure shown in FIG.
The electron block layer 30 is omitted.

In the element structure of the organic electroluminescence element shown in FIG. 4, the electron blocking layer 30 and the hole blocking layer 50 are omitted from the element structure shown in FIG. 1, and the cathode layer 70 and the electron transport layer 60 are formed. An electron injection layer 61 made of an electron injection material is added between them.

Examples of the electron injecting substance include lithium fluoride, lithium oxide,

[0090]

[Chemical formula 62]

Examples thereof include 8-hydroxyquinolinato lithium (hereinafter also referred to as Liq) represented by [Chemical Formula 62].

Next, with reference to FIG. 2 as a first embodiment of the present invention, a method for manufacturing an organic electroluminescence element will be described.

First, the anode layer 10 is formed by a vapor deposition method or a sputtering method on a transparent insulating support, which is a substrate (not shown), such as a glass substrate.

Next, a first solution is prepared by dissolving or dispersing the hole transporting polymer or the hole transporting low molecule in a solvent. Here, it is also possible to further dissolve or disperse the binder polymer in the first solution. Then, the hole transport layer 20 is formed on the anode layer 10 by a wet method using the first solution.

Further, a second solution is prepared by dissolving or dispersing the doping agent 41 and the host agent 42 of the light emitting layer 40 in a solvent. Here, it is also possible to further dissolve or disperse the binder polymer in the second solution. Then, the hole transport layer 2 is formed by the wet method using the second solution.
The light emitting layer 40 is formed on the transparent layer 0.

Further, a third solution is prepared by dissolving or dispersing the electron transporting polymer or the electron transporting low molecule in a solvent. Here, the binder polymer can be further dissolved or dispersed in the third solution. The electron transport layer 6 is formed on the light emitting layer 40 by a wet method using the third solution.
Form 0.

The solubility parameter of the solvent used in the second solution is determined by the substance contained in the hole transport layer 20 (hole transporting polymer or hole transporting low molecule at the film formation temperature of the light emitting layer 40). , Etc.) outside the soluble range. Light emitting layer 40 by a wet method using such a solvent
In the formation of, the organic substance contained in the lower hole transport layer 20 is not dissolved.

The solubility parameter of the solvent used in the third solution is determined by the substances contained in the light emitting layer 40 (the dopant 41, the host agent 42, the binder polymer, etc.) at the film formation temperature of the electron transport layer 60. Has a value outside the soluble range. When the electron transport layer 60 is formed by the wet method using such a solvent, the organic substance contained in the lower light emitting layer 40 is not dissolved.

At this time, the solvent used for the above-mentioned first to third solutions is evaporated by natural drying to form the hole transport layer 20, the light emitting layer 40 and the electron transport layer 60. In this case, there is no need to perform treatments such as heating, polymerization by irradiation of ultraviolet rays, curing, etc. Therefore, the manufacturing process is simple and the production efficiency can be improved.

The wet method used in the present invention includes ordinary coating methods such as casting method, blade coating method, dip coating method, spin coating method, spray coating method, roll coating method and ink jet coating method. .

Finally, the cathode layer 70 is formed on the electron transport layer 60 by using the vapor deposition method or the like to obtain the organic electroluminescence device of the present invention.

The solubility parameter SP is defined by SP = {(ΔH-RT) / V} ^1/2 at the absolute temperature T of the liquid having a molar evaporation heat ΔH and a molar volume V. However, in the above formula, SP is a solubility parameter (unit: (cal / cm ³ ) ^1/2 ), ΔH is a heat of molar evaporation (unit: cal / mol), and R is a gas constant (unit: cal / mol). (Mol · K)), T is the absolute temperature (unit: K), and V is the molar volume (unit: cm ^3).
/ Mol).

FIG. 3 shows a second embodiment of the organic electroluminescent device of the present invention. The light emitting layer 40 is formed before the formation of the electron transport layer 60 during the manufacturing process of the device structure shown in FIG. A hole blocking substance such as PBD shown in [Chemical Formula 2] is formed on the hole blocking layer 50 by a wet method to form an electron on the hole blocking layer 50 in the same manner as in FIG. It is obtained through a manufacturing process in which the transport layer 60 and the cathode layer 70 are sequentially formed.

FIG. 4 shows a third embodiment of the organic electroluminescent device of the present invention. During the process of manufacturing the device structure shown in FIG. 2, the electron transport layer 60 is formed before the formation of the cathode layer 70. An electron injecting substance such as lithium fluoride is deposited thereon by an evaporation method to form an electron injecting layer 61, and then a cathode layer 70 is formed on the electron injecting layer 61 in the same manner as in FIG. Obtained through steps.

[0105]

[Example] [Example 1] I subjected to oxygen plasma treatment
On a TO substrate (commercial ITO, manufactured by Asahi Glass Co., Ltd .: 20Ω / □ or less), NPD shown in [Chemical Formula 33] was deposited as a hole transport layer at a vacuum degree of 10 ⁻³ Pa by a vacuum deposition apparatus at a deposition rate of 1 nm / s.
OXD-1 (ionization potential of 6.1 eV, electron affinity 2.4 eV) shown in [Chemical formula 5] and CBP (ionization potential of 6.15 eV) shown in [Chemical formula 5] as a light emitting layer. , Electron affinity 2.33e
V) and Ir (ppy) ₃ (ionization potential 5.3 eV, electron affinity 3.04 eV) shown in [Chemical Formula 42],
Co-evaporate at a vapor deposition rate of 1 nm / sec so that the weight ratio of each is 1: 1: 0.03, form a film with a thickness of 20 nm, and deposit Alq3 shown in [Chemical Formula 56] as an electron transport layer at a vapor deposition rate of 1 nm. / Sec to form a film with a thickness of 50 nm, and finally,
Aluminum and lithium were co-evaporated at a vapor deposition rate of 1 nm / sec so that the lithium content was 1% to form a cathode, thereby forming the device structure shown in FIG.

At this time, 5V (driving voltage, the same applies hereinafter), 1
mA / cm ² (current density, the same below) 500 cd /
m ² (brightness, the same below), 6.5 V, 10 mA / cm ²
At 4,500 cd / m ² of green light emission was obtained. [Comparative Example 1] An element structure shown in Fig. 2 was prepared in the same manner as in [Example 1] except that only CBP was used as the light emitting layer host material.
In this, 5V, 400cd / m ² at 1 mA / cm ^2, and, 6.5V, the emission of green 3200cd / m ² at 10 mA / cm ² was obtained. [Comparative Example 2] A device structure shown in Fig. 2 was prepared in the same manner as in [Example 1] except that only OXD-1 was used as the light emitting layer host material. In this case, 5V, 500cd / m ² at 1mA / cm ^2,
And, 4100cd / m ² 6.5V, at 10 mA / cm ²
A green emission of was obtained. [Example 2] to [Example 5] A device structure shown in Fig. 2 was prepared in the same manner as in [Example 1] except that the compounds shown in [Table 1] below were used instead of OXD-1. Luminescence having the luminous efficiency shown in [Table 1] was obtained.

[0107]

[Table 1]

[Chemical Formula 3] used as a host agent in [Example 3]
BND indicated by Ir is a dopant having an electron affinity of Ir (pp
y) Since it is almost equal to ₃ (3.04 eV), energy transfer from the host agent to the doping agent cannot be performed efficiently. Therefore, it has an oxadiazole group like BND,
[Example 1] (Using OXD-1), [Example 2] (Using PBD), [Example 4] (Using BBD), [Example 5] (OXD
The luminance is lower than that of (-7 use). In order to make an efficient device, a host agent having an electron affinity smaller than that of the dopant is required. Similarly, regarding the ionization potential, an efficient device can be obtained by selecting a host agent having an ionization potential higher than that of the doping agent. This applies not only to the electron-transporting host agent as described above, but also to the hole-transporting host agent. [Example 6] to [Example 11] Instead of OXD-1,
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 1] except that the compounds shown in [Table 2] were used, light emission with the luminous efficiency shown in [Table 2] was obtained.

[0109]

[Table 2]

[Example 12] to [Example 15] [Example 1]
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 1] except that the compound shown in [Table 3] below was used instead of CBP, the emission efficiency shown in [Table 3] was obtained. Was given.

[0111]

[Table 3]

[Example 16] to [Example 27] [Example 1]
Replace Ir (ppy) ₃ in the light emitting layer with the following [Table 4]
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 1] except that the doping agent shown in Table 1 was used, the light emission with the emission efficiency shown in [Table 4] was obtained.

[0113]

[Table 4]

Example 28 The electron transport layer was replaced with Alq3.
The same as [Example 1] except that it is formed by OXD-1.
The device structure shown in FIG. At this time, 5.5V,
1 mA / cm²At 500 cd / m²And 7V, 10mA
/ Cm²At 4700 cd / m²A green emission of was obtained. Example 29 Hole blocking between light emitting layer and electron transporting layer
Vacuum level of 10^-3Pa, vapor deposition rate 0.1 nm / s
The BCP shown in [Chemical Formula 55] is 6 nm by vacuum deposition with ec.
3 is the same as in [Example 1] except that the film is formed with the thickness of
A device structure was created. At this time, 5.2V, 1mA / c
m²At 500 cd / m²And 6.7V, 10mA / cm
²At 4500 cd / m²A green emission of was obtained. [Example 30] In [Example 1], the electron transport layer and the cathode layer were separated.
A vacuum degree of 10 is used as an electron injection layer in between.^-3Pa, vapor deposition rate
Lithium fluoride by vacuum deposition under 0.1 nm / sec conditions
And the cathode is made of aluminum.
As shown in FIG. 4, the same as in [Example 1] except that the um was replaced.
A device structure was created. At this time, 5V, 1mA / cm²
At 500 cd / m², And 6.5 V, 10 mA / cm²so
4,500 cd / m²A green emission of was obtained. [Example 31] Gel permeation chromatography
Polystyrene-equivalent weight average amount measured by
Say quantity. ) 1,100,000 PV shown in [Chemical Formula 25]
Dissolve 6 mg of K in 1 ml of 1,2 dichloroethane,
Solution 1 was prepared. ITO treated with oxygen plasma
On the substrate (commercial ITO, manufactured by Asahi Glass Co., Ltd .: 20Ω / □ or less)
Spin coating Solution 1 at 1000 rpm for 1 second
A hole transport layer having a thickness of 50 nm was obtained. On hole transport layer
The vacuum degree of 10^-3Pa, vapor deposition rate 1
OXD-1, CBP and Ir (ppy) at nm / sec₃
And so that the weight ratio of each becomes 1: 1: 0.03
Co-evaporated to form a light-emitting layer with a thickness of 20 nm, and the deposition rate
Alq3 is vapor-deposited at 1 nm / sec and a 50 nm film thickness is applied.
A child transport layer is formed, and finally aluminum and lithium
At a deposition rate of 1 nm / se so that the lithium content is 1%.
Co-evaporate with c to form the cathode and form the device structure shown in FIG.
I made it. At this time, 7V, 1mA / cm²At 500 cd /
m², And 8.3V, 10mA / cm²At 4500 cd /
m²Green light emission was obtained. Example 32 The material of the hole transport layer was changed from PVK to [Chemical formula 31]
Except that the polymer (molecular weight 60,000) shown in was changed to
The device structure shown in FIG. 2 was prepared in the same manner as in [Example 31].
It was At this time, 6V, 1mA / cm²At 500 cd / m²Over
7.3V, 10mA / cm ²At 4500 cd / m²Green
A color emission was obtained. [Example 33] As PVK having a molecular weight of 1,100,000
Dissolve 6 mg with 1 ml of 1,2 dichloroethane and dissolve
Liquid 1 was prepared. 1.25 mg as OXD-1 and CB
1.25 mg as P and Ir (ppy)₃As 0.1
7 mg and a binder polymer having a molecular weight of 115,000
Polyvinyl biphenyl 2.5mg and xylene 1ml
It melt | dissolved and created the solution 2. Perform oxygen plasma treatment
On the ITO substrate (commercial ITO, manufactured by Asahi Glass Co., Ltd .: 20Ω /
□ or less) and spin coat solution 1 at 1000 rpm for 1 second.
To obtain a hole transport layer having a thickness of 50 nm. further,
Spin Solution 2 on the hole transport layer at 1000 rpm for 1 second
A 20-nm light emitting layer was obtained by coating. Vacuum deposition
Degree of vacuum 10^-3Deposition rate of Alq3 is 1n with Pa
The electron transport layer is formed with a thickness of 50 nm at m / sec.
Later, aluminum and lithium were replaced with 1% lithium.
Co-deposition at a vapor deposition rate of 1 nm / sec so that the cathode
Then, the device structure shown in FIG. 2 was formed. At this time, 9
V, 1 mA / cm²At 480 cd / m², And 10.5
V, 10 mA / cm²At 4500 cd / m²Green emission
was gotten. [Example 34] to [Example 37] Instead of OXD-1,
[Example 33] except that the compounds shown in Table 5 were used.
When the device structure shown in FIG. 2 was created in the same manner as in [Table 5]
Luminescence having the luminous efficiency shown in was obtained.

[0115]

[Table 5]

[Example 38] to [Example 43] OXD-1
Except that the compounds shown in [Table 6] below were used instead of
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 33], light emission having the light emission efficiency shown in [Table 6] was obtained.

[0117]

[Table 6]

[Example 44] to [Example 47] Except that compounds shown in the following [Table 7] were used in place of CBP,
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 33], light emission having the light emission efficiency shown in [Table 7] was obtained.

[0119]

[Table 7]

[Example 48] to [Example 59] I of solution 2
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 33] except that the compound shown in [Table 8] below was used instead of r (ppy) ₃ , the emission with the emission efficiency shown in [Table 8] was obtained. was gotten.

[0121]

[Table 8]

Example 60 Solution 2 was added with 2.5 mg of a polymer represented by [Chemical Formula 7] (molecular weight 60,000) and C
BP2.5mg and Ir (ppy) ₃ 0.17mg
An element structure shown in FIG. 2 was prepared in the same manner as in [Example 33] except that and were dissolved in 1 ml of xylene. At this time, 480 cd / m ² 9 V at 8 V and 1 mA / cm ²
Green emission of 4500 cd / m ² was obtained at 0 mA / cm ² . [Example 61] [Example 60] except that the solution 2 was prepared by using the polymer represented by [Chemical formula 8] (molecular weight 60,000) instead of the polymer represented by [Chemical formula 7]. Similarly, the device structure shown in FIG. 2 was prepared. At this time, 8V, 1mA / cm
² at 480 cd / m ² and 9 V, 10 mA / cm ² at 4
A green light emission of 500 cd / m ² was obtained. [Example 62] to [Example 64] Solution 2 was replaced with the polymer represented by [Chemical formula 7], and [Chemical formula 38] to [Chemical formula 38] shown in [Table 9] below.
When the device structure shown in FIG. 2 was prepared in the same manner as in [Example 60] except that the polymer represented by [Chemical Formula 40] (each molecular weight 60,000) was used, the luminous efficiency shown in [Table 9] was obtained. Luminescence was obtained.

[0123]

[Table 9]

[Example 65] Solution 2 was prepared by converting N-phenylpolycarbazole (molecular weight 60,00) shown in [Chemical Formula 31] into
0) 2.5 mg, OXD-1 2.5 mg and Ir (ppy) ₃ 0.17 mg xylene 1 m
A device structure shown in FIG. 2 was prepared in the same manner as in [Example 33] except that the device structure was dissolved in 1 to prepare the device structure. At this time, 7V, 1mA /
cm ² 480 cd / m ² 8V, 10 mA / cm ² 4
A green light emission of 500 cd / m ² was obtained. [Example 66] PVK6m having a molecular weight of 1,100,000
g with 1 ml of 1,2-dichloroethane to give solution 1
It was created. 1.25 mg as OXD-1 and 1.25 mg as CBP and 0.17 m as Ir (ppy) ₃ .
g and 2.5 mg of polyvinyl biphenyl having a molecular weight of 100,000 as a binder polymer were dissolved in 1 ml of xylene to prepare a solution 2. Solution 3 was prepared by dissolving 2.5 mg of PBD and 2.5 ml of polystyrene having a molecular weight of 50,000 as a binder polymer in 1 ml of cyclohexane.

Solution 1 was placed on an ITO substrate that had been subjected to oxygen plasma treatment (commercial ITO, manufactured by Asahi Glass Co., Ltd .: 20 Ω / □ or less).
5 by spin coating at 1000 rpm for 1 second
A hole transport layer of 0 nm was obtained. Solution 2 on the hole transport layer,
20n by spin coating at 1000 rpm for 1 second
A light emitting layer of m was obtained. Further, the solution 3 is applied on the light emitting layer for 10 times.
An electron transport layer of 50 nm was obtained by spin coating at 00 rpm for 1 second.

[0126] Finally, using a vacuum deposition apparatus, aluminum
And lithium are vapor-deposited so that the lithium content is 1%.
A cathode was formed by co-evaporation at 1 nm / sec. At this time,
9.5V, 1mA / cm²At 480 cd / m²  And 1
0.5V, 10mA / cm²At 4500 cd / m²Green
A color emission was obtained. [Example 67] The solution 2 was prepared by mixing the polymer (formula 7)
2.5 mg of offspring and CBP and Ir (pp
y)₃0.17 mg and dissolved in 1 ml of xylene
2 except that the elements shown in FIG.
Created a child structure. At this time, 8.5V, 1mA / cm²
At 480 cd / m²And 9V, 10mA / cm²At 45
00 cd / m²A green emission of was obtained. [Example 68] The solution 1 was replaced with PVK by [Chemical formula 31]
It was prepared using the polymer (molecular weight 60,000) shown below.
Otherwise, the device structure shown in FIG. 2 was prepared in the same manner as in [Example 67].
did. At this time, 8V, 1mA / cm²At 480 cd / m²
And 9.0V, 10mA / cm ²At 4500 cd / m²of
Green light emission was obtained. [Example 69] The solution 3 was replaced with the oxadia compound represented by the [formula 7].
5 as a sol polymer compound (molecular weight 60,000)
except that it was prepared by dissolving mg in 1 ml of cyclohexane.
The device structure shown in FIG. 2 was prepared in the same manner as in [Example 68].
It was At this time, 7V, 1mA / cm²At 460 cd / m²Over
7.5V, 10mA / cm ²At 4300 cd / m²Green
It was a color emission.

[0127]

As is clear from the above description, the host agent of the light emitting layer used in the present invention has a bipolar property, that is, a double polarity which is easily converted into radical cation and radical anion. It becomes possible to excite the dopant without uneven distribution and to emit phosphorescence. In the organic electroluminescence device having the light emitting layer formed in this way, high-luminance light emission can be obtained without the light emitting region in the light emitting layer being concentrated in a specific portion.

[Brief description of drawings]

FIG. 1 is a device structure of an organic electroluminescence device.

FIG. 2 is a first embodiment of the device structure of the present invention.

FIG. 3 is a second embodiment of the device structure of the present invention.

FIG. 4 is a third embodiment of the device structure of the present invention.

[Explanation of symbols]

10 Anode layer 40 light emitting layer 41 Dope 42 Host agent 70 cathode layer

Claims (10)

[Claims] 1. An organic electroluminescence device comprising a light emitting layer formed between both electrode layers of an anode layer and a cathode layer, the host agent and a phosphorescent emitting dopant, wherein the host agent has a bipolar property. An organic electroluminescence device characterized by: 2. The organic electroluminescence device according to claim 1, wherein the host material having a bipolar property comprises a hole transporting substance and an electron transporting substance. 3. The electron-transporting substance used as the host agent is represented by the following formula: The organic electroluminescent device according to claim 2, comprising a compound having an oxadiazole group represented by the structural formula [Chemical Formula 1]. 4. The compound having an oxadiazole group is represented by: [Chemical 3] [Chemical 4] [Chemical 5] [Chemical 6] [Chemical 7] [Chemical 8] The organic electroluminescent device according to claim 3, comprising one or more compounds represented by structural formulas [Chemical Formula 2] to [Chemical Formula 8]. 5. The electron-transporting substance used as the host agent is represented by: The organic electroluminescent device according to claim 2, comprising a compound having a triazole group represented by the structural formula [Chemical formula 9]. 6. The compound having a triazole group is represented by: [Chemical 11] [Chemical 12] [Chemical 13] [Chemical 14] [Chemical 15] [Chemical 16] (In the general formula [Chemical Formula 16], X ₅ is any of hydrogen, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group and a heterocyclic group, and X ₆ is an aliphatic hydrocarbon group, an aromatic group. Each of them is independently selected from a hydrocarbon group, an ether group and a heterocyclic group.) (In the general formula [Chemical Formula 17], X ₇ is any of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group and a heterocyclic group, and X ₈ and X ₉ are hydrogen and an aliphatic hydrocarbon group. , An aromatic hydrocarbon group, an ether group, or a heterocyclic group, each of which is independently selected. (In the general formula [Chemical Formula 18], X ₁₀ and X ₁₁ are each independently selected from hydrogen, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group, and a heterocyclic group.) Structural formula [ The organic electroluminescence device according to claim 5, which is composed of one or more kinds of compounds represented by Chemical formulas 10 to 15 or general formulas 16 to 18. 7. The hole-transporting substance used as the host agent is represented by: 7. The organic electroluminescence device according to claim 2, comprising a compound having a carbazolyl group represented by the structural formula [Chemical Formula 19]. 8. The compound having a carbazolyl group is represented by: [Chemical 21] [Chemical formula 22] [Chemical formula 23] [Chemical formula 24] [Chemical 25] [Chemical formula 26] (R in the general formula [Chemical Formula 26] is independently hydrogen,
It represents any of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group and a heterocyclic group. 8. The organic electroluminescence device according to claim 7, which is composed of one or more kinds of compounds represented by the structural formulas [Chemical Formula 20] to [Chemical Formula 25] or the general formula [Chemical Formula 26]. 9. The doping agent is represented by: (In the general formula [Chemical Formula 27], Ar represents an aryl group, X ₁₂ and X.
₁₃ are each independently an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group or a heterocyclic group, and Ar and X
_An aromatic ring may be condensed with ₁₂ and n is an integer of 1 or more and 3 or less. The organic electroluminescence device according to claim 1, comprising a compound represented by the general formula [Chemical Formula 27]. 10. The molecular structure of the dopant is: (In the general formula [Chemical Formula 28], R1 to R8 each independently represent hydrogen, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an ether group, or a heterocyclic group, and / or Rn adjacent thereto. (In the formula, n is an integer of 1 or more and 8 or less), the aromatic ring may be condensed.) The compound of the formula [Chemical Formula 28]. The organic electroluminescence device according to item 1.