JP2003026641A - Binaphthyl compound, method for producing the same and organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binaphthyl compound giving an organic electroluminescent element, having excellent heat-resistance, driving stability and drivable at a low voltage and keeping a stable luminescent property even at a high temperature, a method for producing the compound and an organic electroluminescent element produced by using the same. SOLUTION: The binaphthyl compound is expressed by general formula (1) (Ar1 to Ar4 are each a monocyclic or condensed ring group of a 5- or 6-membered aromatic hydrocarbon group; (m) and (n) are each an integer of 0-4; m+n>=1; and the naphthalene ring may have arbitrary substituents). The binaphthyl compound is produced by the Ullmann reaction. The organic electroluminescent element has a hole transfer layer containing the binaphthyl compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel binaphthyl compound, a method for producing the same, and an organic electroluminescent device. More specifically, the present invention relates to a thin film device that emits light by applying an electric field to a light emitting layer made of an organic compound. The present invention relates to a binaphthyl compound suitable as a material for forming a hole transport layer provided in an organic electroluminescent device as described above, a method for producing the same, and an organic electroluminescent device having a layer containing the binaphthyl compound formed therein.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescent (EL) element, Zn which is a II-VI group compound semiconductor of an inorganic material has been used.
It is general that S, CaS, SrS, etc. are doped with Mn or a rare earth element (Eu, Ce, Tb, Sm, etc.), which is the emission center, but the EL element made from the above inorganic material is 1). AC drive is required (50 to 1000Hz), 2) high drive voltage (up to 200V), 3) full color is difficult (especially blue), and 4) peripheral drive circuit cost is high. .

However, in recent years, in order to improve the above problems,
EL devices using organic thin films have been developed. In particular, in order to improve the light emission efficiency, the type of the electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transport layer made of an aromatic diamine and a light emitting layer made of an aluminum complex of 8-hydroxyquinoline are formed. Development of organic electroluminescent device equipped with (Appl. Phys. Lett., Vol. 51,
913, 1987), the light emission efficiency is greatly improved as compared with the conventional EL device using a single crystal such as anthracene, and it is close to practical characteristics.

In addition to the electroluminescent device using the low molecular weight material as described above, poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy)- 1,4-phenylene vinylene], poly (3-alkylthiophene), and other electroluminescent devices, and devices in which polymers such as polyvinylcarbazole are mixed with low-molecular emitting materials and electron transfer materials Is also being developed.

In order to apply the organic electroluminescent device to a light source such as a flat panel display or a backlight,
It is necessary to secure sufficient reliability of the element. However, the conventional organic electroluminescent device has insufficient heat resistance, and the current-
The voltage characteristics were shifted to the high voltage side, the life was shortened due to local Joule heat generation when the device was driven, and deterioration such as generation and increase of non-light emitting portions (dark spots) was unavoidable.

[0006] The main cause of these deteriorations is the deterioration of the thin film shape of the organic layer. It is considered that the deterioration of the shape of the thin film is a temperature rise due to heat generation when the device is driven and is caused by crystallization (or aggregation) of the organic amorphous thin film. It is considered that this low heat resistance results from the low glass transition temperature (hereinafter abbreviated as Tg) of the material.

Low molecular weight (molecular weight: about 400 to 600)
Many of these compounds, especially hole transport materials, have a low melting point and high symmetry. Typical aromatic amine compounds that have been often used as hole transporting materials for organic electroluminescence devices are shown below.

[0008]

[Chemical 7]

[0009]

[Chemical 8]

[0010]

[Chemical 9]

The Tg of the aromatic diamine (A-1) is 65.
C, and the Tg of N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (usually called TPD) is 60 ° C, starburst Tg of type aromatic triamine (A-2) is 75 ℃ (J.Phys.Che
m., 97, 6240, 1993), and the Tg of 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (A-3) having an α-naphthyl group introduced. Is 96 ° C (Technical report of IEICE, OME95-54, 1995).

In the organic amorphous thin film formed from these aromatic amine compounds, crystallization occurs due to temperature rise,
In the two-layer device structure of the hole transport layer and the light emitting layer, mutual diffusion phenomenon occurs. As a result, a deterioration phenomenon in which the light emission characteristics of the element, especially the driving voltage becomes high appears, and finally the driving life is shortened. In addition, it is desirable that the Tg of the hole transporting material is higher, because the temperature rise in the steps of vapor deposition, baking (annealing), wiring, sealing, etc. is expected during the production of the element other than when the element is driven.

On the other hand, attempts have been made to use polymer materials instead of low molecular weight compounds as hole transport materials for organic electroluminescent devices. For example, polyvinylcarbazole (Technical Report of IEICE, OME90-38, 1990) ), Polysilane (Appl.Phys.Lett., 59, 2760, 1991),
Polyphosphazene (The 42nd Annual Meeting of the Polymer Society of Japan, I-8
-07 and I-8-08, 1993) have been reported. However, although polyvinylcarbazole has a high Tg of 200 ° C., it has a problem such as hole trapping and has a low durability.
Polysilane has a short driving life of several seconds due to photodegradation and the like, and polyphosphazene has a high ionization potential and does not show characteristics exceeding conventional aromatic diamines.

In addition to this, an aromatic diamine compound is added to polycarbonate or polymethylmethacrylate in an amount of 30 to 80.
A hole-transporting layer dispersed by weight% is also being studied (Jpn.
J. Appl. Phys., Vol. 31, L960, p. 1992), a low molecular weight compound acts as a plasticizer to lower Tg, and the device characteristics are also lower than when an aromatic diamine compound is used alone.

As described above, at present, in order to put the organic electroluminescence device into practical use, there are serious problems in heat resistance and driving life of the device.

The heat resistance of the organic electroluminescent device is not improved,
The instability of the light emission characteristic is a serious problem as a light source for a facsimile, a copying machine, a backlight of a liquid crystal display or the like, and is an undesirable characteristic as a display element for a flat panel display or the like. This is especially serious when considering application to in-vehicle displays.

Incidentally, JP-A-9-255948, JP-A-10-255948 and JP-A-11-15.
Japanese Patent No. 2253 describes an organic electroluminescence device having a hole transport layer containing the following binaphthyl compound and the like.

[0018]

[Chemical 10]

The above-mentioned binaphthyl compound has a relatively high Tg and is effective in improving the heat resistance and driving stability of the organic electroluminescence device, but further improvement is desired.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional circumstances, and has excellent heat resistance and driving stability, can be driven at a low voltage, and has stable light emission characteristics even at high temperatures. It is an object of the present invention to provide a novel binaphthyl compound capable of realizing a sustainable organic electroluminescent device, a method for producing the same, and an organic electroluminescent device using the binaphthyl compound.

[0021]

The binaphthyl compound of the present invention is characterized by being represented by the following general formula (I).

[0022]

[Chemical 11]

(In the general formula (I), Ar ₁ , Ar ₂ and A
r _3, Ar ₄ each independently substituents of may 5 or 6-membered ring which may have aromatic hydrocarbon ring or aromatic heterocyclic ring, represents a monocyclic or fused ring group, and Ar ₁ Ar ₂ , Ar ₃ and Ar ₄
May combine with each other to form a ring. m and n each represent an integer of 0 to 4, and m + n ≧ 1. Further, the naphthalene ring in the formula other than -NAr ₁ Ar ₂ and -NAr ₃ Ar _4, which may have a substituent. )

That is, the present inventors have studied to improve the problem of steric hindrance at the time of introducing a substituent into the binaphthyl skeleton and to further improve the heat resistance and other properties of the binaphthyl compound. As a aromatic amine having a skeleton, a high Tg, and not only in terms of properties but also in terms of synthesis, a binaphthyl compound represented by the above general formula (I) and a method for producing the same have been found, and the present invention has been achieved. did.

The binaphthyl compound of the present invention represented by the above general formula (I) has a very high Tg of 100 ° C. or higher because of its molecular structure. Therefore, by using this binaphthyl-based compound, it is possible to easily obtain an amorphous thin film that does not crystallize, and even if it is in a high temperature state of 100 ° C. or higher, it is adjacent to the layer containing the binaphthyl-based compound. Mutual diffusion of molecules with the organic layer is sufficiently suppressed.

Such a binaphthyl compound of the present invention can be prepared by the method for producing a binaphthyl compound of the present invention.
For example, it is manufactured as follows.

(1) A binaphthyl derivative represented by the following general formula (III) is reacted with an aromatic amine derivative represented by the following general formulas (IVa) and (IVb).

[0028]

[Chemical 12]

(In the general formula (III), X₁And X_TwoAre each
Independently represent a halogen atom, m and n are represented by the general formula (I)
It is synonymous with opening. Further, the naphthalene ring in the formula is X₁
And X _TwoBesides, it may have an arbitrary substituent. )

[0030]

[Chemical 13]

(Ar ₁ and Ar ₂ in the general formula (IVa),
Ar ₃ and Ar ₄ in the general formula (IVb) have the same meanings as in the general formula (I). )

(2) A binaphthyl derivative represented by the following general formula (V) is reacted with an aromatic halogen compound represented by the following general formula (VI).

[0033]

[Chemical 14]

(In the general formula (V), m and n have the same meanings as in the general formula (I). Further, the naphthalene ring in the formula has an arbitrary substituent in addition to -NH _2. Good too.)

[0035]

[Chemical 15]

(In the general formula (VI), X'represents a halogen atom, and Ar 'represents Ar ₁ to Ar in the general formula (I).
Synonymous with ₄ . )

The organic electroluminescent device of the present invention has such a layer containing the binaphthyl compound of the present invention between the anode and the cathode, and preferably comprises a cathode and a layer containing the binaphthyl compound. It has a light emitting layer in between.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

The binaphthyl compound of the present invention is represented by the above general formula (I). Naphthalene ring in the general formula (I), -NAr ₁ Ar ₂ and -NAr ₃ Ar ₄ may have an arbitrary substituent in addition to, but preferred are a halogen atom for the substituent, a hydroxyl group, a substituent An alkyl group which may have, an alkoxy group which may have a substituent,
One or two or more substituents selected from the group consisting of an alkenyl group which may have a substituent and an alkoxycarbonyl group which may have a substituent. The compound represented by the general formula (I) is more preferably the compound represented by the following general formula (II).

[0040]

[Chemical 16]

(In the general formula (II), Ar ₁ , Ar ₂ and A
r ₃ , Ar ₄ , m and n have the same meanings as in formula (I), and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom, a halogen atom or a hydroxyl group. An alkyl group which may have a substituent, an alkoxy group which may have a substituent, an alkenyl group which may have a substituent or an alkoxycarbonyl group which may have a substituent. Represent )

In the general formulas (I) and (II), Ar ₁ ,
Ar ₂ , Ar ₃ and Ar ₄ each independently represent an aromatic hydrocarbon ring such as a phenyl group, a naphthyl group or an anthryl group, or an aromatic heterocycle such as a pyridyl group or a thienyl group, all of which are substituted. It may have a group.

The substituent of the aromatic hydrocarbon ring and / or the aromatic heterocycle of Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ is a halogen atom;
An alkyl group having 6 to 6 carbon atoms; an alkenyl group having 2 to 7 carbon atoms such as a vinyl group; an alkoxycarbonyl group having 2 to 7 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; Alkoxy group; aromatic hydrocarbon group such as phenyl group; aryloxy group such as phenoxy group, benzyloxy group; diethylamino group,
Examples thereof include dialkylamino groups such as diisopropylamino group and methylethylamino group.

Further, Ar ₁ and Ar ₂ and / or Ar ₃ and Ar ₄ may be bonded to each other to form a ring. In this case, a specific example of the ring to be formed has a substituent. Examples thereof include a carbazole ring, a phenoxazine ring, an iminostilbene ring, a phenothiazine ring, an acridone ring, an acridine ring and an iminodibenzyl ring which may be present. Of these, a carbazole ring is preferable.

M and n each represent an integer from 0 to 4, and m + n ≧ 1. Particularly preferred are m = 1 and n = 1.

When m and / or n is 2 or more, 1
2 or more Ar contained in each molecule ₁, Ar_Two, Ar_Three
And Ar_FourEach independently represents the group described above.

R _{1 to} R ₆ are preferably each independently a hydrogen atom: a halogen atom; a hydroxyl group; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; an α-group such as a trifluoromethyl group and a trichloromethyl group. Haloalkyl group; alkenyl group having 2 to 7 carbon atoms such as vinyl group and allyl group; alkoxycarbonyl group having 2 to 7 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; 1 to 6 carbon atom such as methoxy group and ethoxy group And the alkoxy group.

Particularly preferred as R _{1 to} R ₆ are independently a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms.

Particularly preferably, R ₃ and R ₄ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and all of R ₁ , R ₂ , R ₅ and R ₆ are It is a hydrogen atom.

The compound represented by the general formula (I) is synthesized according to the method of the present invention, for example, by the following route.

First, a binaphthyl derivative represented by the following general formula (IIIa), specifically, in the following general formula (IIIa), iodide in which X ₁ and X ₂ are iodine and the following general formula (IVa) The secondary amine derivative represented by the aromatic amine derivative represented by Ullmann reaction (Organic Synthes
is, Vol. 1, p. 544) to produce a monosubstituted compound represented by the following general formula (VII).

[0052]

[Chemical 17]

(In formula (IIIa), X ₁ and X ₂ each independently represent a halogen atom, and R _{1 to} R ₆ , m and n have the same meanings as in formulas (I) and (II). )

[0054]

[Chemical 18]

(Ar ₁ and Ar ₂ in the general formula (IVa) have the same meanings as in the general formula (I).)

[0056]

[Chemical 19]

After the obtained monosubstituted product is separated by column chromatography, this and the secondary amine derivative represented by the following general formula (IVb) are subjected to the Ullmann reaction in the same manner as above to carry out the desired general formula (I). An aromatic amine compound represented by

[0058]

[Chemical 20]

(Ar ₃ and Ar ₄ in the general formula (IVb) have the same meanings as in the general formula (I).)

In the general formula (I), --NAr ₁
In the case of a compound in which Ar ₂ and -NAr ₃ Ar ₄ are the same group, the target compound is obtained by a single Ullmann reaction using a double amount of the secondary amine derivative without separating the above monosubstituted compound. be able to.

In the above general formula (I), Ar _{1 to} Ar ₄
The binaphthyl compounds having the same substituents can also be synthesized by the following method.

A binaphthyl derivative represented by the following general formula (Va) is converted into a compound represented by the following general formula (VI), for example, an iodide in which X'is iodine in the above general formula (VI), in the same manner as above. Ullmann reaction to obtain the final product.

[0063]

[Chemical 21]

(In the general formula (Va), R _{1 to} R ₆ , m and n have the same meanings as in the general formulas (I) and (II).)

[0065]

[Chemical formula 22]

(In the general formula (VI), X'represents a halogen atom, and Ar 'represents Ar ₁ to Ar in the general formula (I).
Synonymous with ₄ . )

Specific preferred examples of the binaphthyl compound represented by the above general formula (I) are shown in Tables 1 to 14, but not limited thereto. In addition, in the following table, R ₁ ~
If no substituents are specifically mentioned for R ₆ , then they are hydrogen atoms.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

[0074]

[Table 7]

[0075]

[Table 8]

[0076]

[Table 9]

[0077]

[Table 10]

[0078]

[Table 11]

[0079]

[Table 12]

[0080]

[Table 13]

[0081]

[Table 14]

The structure of the organic electroluminescent device of the present invention using the binaphthyl compound of the present invention will be described below with reference to the drawings.

1 and 2 are cross-sectional views schematically showing an embodiment of the organic electroluminescence device of the present invention. 1 is a substrate, 2 is an anode, 3 is an anode buffer layer, 4 is a hole transport layer, Reference numeral 5 represents a light emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.

The substrate 1 serves as a support for the organic electroluminescent device, and a quartz plate, a glass plate, a metal plate or a metal foil, a plastic film or a sheet, etc. are used. In particular, a glass plate and a transparent synthetic resin sheet such as polyester, polymethacrylate, polycarbonate and polysulfone are preferable. When a synthetic resin is used for the substrate, it is necessary to pay attention to the gas barrier property. If the gas barrier property of the substrate is low, the organic electroluminescent device may be deteriorated by the outside air passing through the substrate. Therefore, when a synthetic resin is used for the substrate, it is preferable to provide a dense silicon oxide film or the like on one surface or both surfaces of the substrate to enhance the gas barrier property.

An anode 2 is provided on the substrate 1. Anode 2
Plays a role of injecting holes into the hole transport layer 4. The anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a conductive metal oxide such as an oxide of indium and / or tin, a halogenated metal such as copper iodide, carbon black, Alternatively, it is formed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline. The anode 2 is usually formed on the substrate 1 by sputtering, vacuum deposition or the like in many cases. When forming the anode 2 with fine particles of metal such as silver, fine particles of copper iodide, carbon black, fine particles of conductive metal oxide, fine particles of conductive polymer, etc., a suitable binder resin solution is used. It can also be formed by a method of dispersing and coating on the substrate 1. Further, when the anode 2 is formed of a conductive polymer, a polymerized thin film may be directly formed on the substrate 1 by electrolytic polymerization, or a method of applying a conductive polymer solution on the substrate 1 may be used. Phys. Lett., Volume 60, 2711, 19
1992). The anode 2 usually has a single layer structure, but may have a laminated structure of a plurality of materials if desired.

The anode 2 may be opaque, but is preferably transparent. Normally, the visible light transmittance is 60.
% Or more, particularly preferably 80% or more, the anode 2
In order to ensure this transparency, the thickness of the layer is preferably about 5 to 1000 nm, particularly about 10 to 500 nm. When it may be opaque, the thickness of the anode 2 is arbitrary, and if desired, it may be formed of metal to serve also as the substrate 1.

In the case of the device having the structure shown in FIG. 1, the hole transport layer 4 is provided on the anode 2. The conditions required for the material of the hole transport layer 4 are that the hole injection efficiency from the anode 2 is high and that the injected holes can be efficiently transported. For that purpose, it is required that the ionization potential is low, the transparency to visible light is high, the hole mobility is high, the stability is high, and trap impurities are not easily generated during manufacturing or use. To be done. In addition to the above general requirements, the element is required to have heat resistance of 100 ° C. or higher depending on the application. Therefore, a material having a Tg value of 100 ° C. or higher is preferable.

The binaphthyl compound of the present invention represented by the general formula (I) sufficiently satisfies these conditions. Therefore, in the organic electroluminescent device of the present invention, the binaphthyl compound of the present invention can be used as the cathode 7 described later. It is preferably used as a layer-forming material having a hole injecting / transporting property provided between the light emitting layer 5 and the light emitting layer 5.

In the following, the case where the binaphthyl compound of the present invention is used as the material of the hole transport layer 4 will be described as an example.

The hole transport layer 4 containing the binaphthyl compound represented by the general formula (I) is formed on the anode 2 by a coating method or a vacuum deposition method. In the case of the coating method, a coating solution prepared by dissolving the binaphthyl compound of the present invention in a solvent, and further adding an additive such as a binder resin or a coatability improving agent that does not become a hole trap to the solution if necessary. May be coated on the anode 2 by a known coating method such as a spin coating method and dried. As the binder resin, polycarbonate, polyarylate, polyester or the like is used. Since the hole mobility decreases when the amount of the binder resin in the hole transport layer 4 is large, it is preferable to use the binder resin so that the content of the binder resin in the hole transport layer 4 is 50% by weight or less.

In the case of the vacuum vapor deposition method, the crucible containing the binaphthyl compound of the present invention is placed in a vacuum container, and the anode 2 is arranged so as to face the crucible. After evacuating the inside of the vacuum container to about 10 ⁻⁴ Pa with a vacuum pump, the crucible is heated to evaporate the binaphthyl compound, and the generated vapor is deposited on the anode 2.

The hole transport layer 4 may be formed by using one kind of the binaphthyl compound of the present invention alone, or may be formed by mixing two or more kinds as necessary. Also,
An aromatic diamine other than the binaphthyl compound of the present invention may be contained within a range that does not impair the performance of the device of the present invention.

The hole transport layer 4 further includes, as an acceptor, a metal complex and / or a metal salt of an aromatic carboxylic acid (JP-A-4-320484), a benzophenone derivative and a thiobenzophenone derivative (JP-A-5-320). 295361), fullerenes (JP-A-5-331458), etc.
^It may be doped at a concentration of ⁻³ to 10% by weight to generate holes as free carriers. In this way, the drive voltage can generally be lowered.

The content of the binaphthyl compound of the present invention in the hole transport layer 4 is preferably 50% by weight or more, and more preferably 80% by weight or more in the layer.

The thickness of the hole transport layer 4 is usually 10 to 300 nm.
, Preferably 30 to 100 nm. As described above, the thin hole transport layer 4 is preferably formed by the vacuum evaporation method, which makes it easy to uniformly form a thin film.

In order to improve the contact between the anode 2 and the hole transport layer 4, an anode buffer layer 3 may be provided between the cathode 2 and the hole transport layer 4 as shown in FIG. The conditions required for the material used for the anode buffer layer 3 include that it can form a uniform thin film with good contact with the anode 2 and that it is thermally stable, that is, has a high melting point and glass transition temperature. Particularly, the melting point is preferably 300 ° C. or higher, and the glass transition temperature is preferably 100 ° C. or higher.
Further, it has a low ionization potential, facilitates hole injection from the anode 2, and has a high hole mobility.

As a material for the anode buffer layer 3, a porphyrin derivative or a phthalocyanine compound has hitherto been disclosed (Japanese Unexamined Patent Publication No. Sho.
63-295695), a starbust type aromatic triamine (JP-A-4-308688), a hydrazone compound (JP-A-4-320483), an alkoxy-substituted aromatic diamine derivative (JP-A-4-220995). ), P- (9-anthryl) -N, N'-di-p-tolylaniline (JP-A-3-11148).
5), polythienylene vinylene, poly-p-phenylene vinylene (JP-A-4-145192), polyaniline (Appl. Phys. Lett., 64, 1245, 1994) and other organic compounds, , Sputtered carbon film (JP-A-8-31573)
Gazette) and metal oxides such as vanadium oxide, ruthenium oxide, molybdenum oxide (The 43rd Joint Lecture on Applied Physics, 27a-SY-9, 1996).

Among these, as the compound often used as the anode buffer layer material, a porphine compound or a phthalocyanine compound can be mentioned. These compounds may have a central metal or may be metal-free.

Preferred specific examples of these compounds include the following compounds. Porphyrin 5,10,15,20-tetraphenyl-21H, 23H-porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine-
Porphine cobalt (II) 5,10,15,20-tetraphenyl-21H, 23H-porphine-
Porphin copper (II) 5,10,15,20-tetraphenyl-21H, 23H-porphine-
Porphine Zinc (II) 5,10,15,20-Tetraphenyl-21H, 23H-Porphine-
Porphine vanadium (IV) oxide 5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphine 29H, 31H-phthalocyanine copper (II) phthalocyanine zinc (II) phthalocyanine titanium phthalocyanine oxide magnesium phthalocyanine lead phthalocyanine copper ( II) 4,4 ', 4'',4'''-Tetraaza-29H, 31H-phthalocyanine

The anode buffer layer 3 can also be formed into a thin film in the same manner as the hole transport layer 4, but when formed of an inorganic material, a sputtering method, an electron beam evaporation method, or a plasma CVD method is further adopted. You can also

The thickness of the anode buffer layer 3 is usually 3-100.
nm, preferably 10 to 50 nm.

A light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is formed of a material that efficiently recombines electrons injected from the cathode 7 and holes injected from the anode between the electrodes to which an electric field is applied, and efficiently emits light by the recombination.

As a material satisfying such a condition, an aromatic compound such as tetraphenyl butadiene (see JP-A-57 / 57)
-51781), a metal complex such as an aluminum complex of 8-hydroxyquinoline (JP-A-59-194393),
Metal complex of 10-hydroxybenzo [h] quinoline (JP-A-6-322362), mixed-ligand aluminum chelate complex (JP-A-5-198377, JP-A-5-198378).
JP-A-5-214332, JP-A-6-172751), and cyclopentadiene derivative (JP-A-2-289675).
JP-A No. 2-289676), oxadiazole derivative (JP-A No. 2-216791), bisstyrylbenzene derivative (JP-A No. 1-245087).
JP-A-2-222484), perylene derivatives (JP-A-2-189890 and JP-A-3-791), coumarin compounds (JP-A-2-191694 and JP-A-3-792),
Rare earth complex (JP-A-1-256584), distyrylpyrazine derivative (JP-A-2-252793), p-phenylene compound (JP-A-3-33183), thiadiazolopyridine derivative (JP-A-3-256183) 37292), pyrrolopyridine derivative (JP-A-3-37293), naphthyridine derivative (JP-A-3-203982), silole derivative (Chemical Society of Japan 70th Annual Meeting, 2D1 02 and 2D1 03, 1996).
Year).

For the purpose of improving the driving life of the device, it is effective to dope the fluorescent dye with the light emitting layer material as a host material. For example, using a metal complex such as an aluminum complex of 8-hydroxyquinoline as a host material,
Naphthalacene derivatives represented by rubrene (Japanese Patent Application Laid-Open No. 4-33
5087) and quinacridone derivatives (JP-A-5-70773).
No.), condensed polycyclic aromatic rings such as perylene (JP-A-5-
(198377 gazette) is doped with 0.1 to 10% by weight of the host material, so that the light emission characteristics of the device, particularly the driving stability can be greatly improved.

The thickness of the light emitting layer 5 is usually 10 to 200 nm, preferably 30 to 100 nm.

The light emitting layer 5 can also be formed by the same method as the hole transporting layer 4, but a vacuum deposition method is usually used. As a method of doping the host material of the light emitting layer 5 with the fluorescent dye such as the naphthacene derivative, the quinacridone derivative, and perylene, there are a method by co-evaporation and a method in which an evaporation source is mixed in a predetermined concentration in advance.

When each of the above dopants is doped in the light emitting layer 5, it is usually doped uniformly in the thickness direction of the light emitting layer 5, but there may be a concentration distribution in the thickness direction. For example, it may be doped only in the vicinity of the interface on the hole transport layer 4 side, or conversely, may be doped only in the vicinity of the interface on the cathode 7 side.

On the light emitting layer 5, an electron transport layer 6 may be further laminated as shown in FIG. 2 in order to improve the light emitting efficiency of the organic electroluminescent device. The material for forming the electron transport layer 6 is required to allow easy electron injection from the cathode 7 and have a large electron transport capability. As such an electron transporting material, the materials already mentioned as the material for forming the light emitting layer 8
-Aluminum complex of hydroxyquinoline, oxadiazole derivative (Appl. Phys. Lett., 55, 1489, 198)
9 years) and polymethylmethacrylate (PMM)
A) dispersed in resin (Appl. Phys. Lett., 61
Vol., 2793, 1992), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine (Phys. Stat. Sol.
(a), Vol. 142, p. 489, 1994), n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide and the like.

The thickness of the electron transport layer 6 is usually 5 to 200 n.
m, preferably 10-100 nm.

The electron transport layer 6 is formed by laminating on the light emitting layer 5 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum vapor deposition method is used.

The cathode 7 plays a role of injecting electrons into the light emitting layer 5. The material used as the cathode 7 is the anode 2
Although it is possible to use the same material as that used for the above, a metal having a low work function is preferable for efficient electron injection, and tin, magnesium, indium, calcium, aluminum, silver, or another suitable material is preferable. Metals or alloys thereof are used.

As a specific example, a magnesium-silver alloy,
Examples include low work function alloy electrodes such as magnesium-indium alloy and aluminum-lithium alloy.

The film thickness of the cathode 7 is usually the same as that of the anode 2.

For the purpose of protecting the cathode 7 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere on the cathode 7 in order to increase the stability of the device. As the stable metal layer, metals such as aluminum, silver, nickel, chromium, gold and platinum are used.

Furthermore, inserting an extremely thin film (0.1 to 5 nm) of LiF, Li ₂ O, etc. at the interface between the cathode 7 and the light emitting layer 5 or the electron transport layer 6 is also an effective method for improving the efficiency of the device. Yes, preferred (Appl. Phys. Lett., 70, 152, 1997
Year; IEEE Trans. Electron. Devices, 44, 1245, 19
1997).

Further, the cathode 7 and the light emitting layer 5 or the electron transport layer 6
An interfacial layer made of an organic compound may be provided between the two in order to improve the contact with. Examples of compounds used for the cathode interface layer include aromatic diamine compounds (JP-A-6-267658) and quinacridone compounds (JP-A-6-267658).
330031), naphthacene derivative (JP-A-6-330032), organic silicon compound (JP-A-6-325871), organic phosphorus compound (JP-A-5-325872), N-
Compounds having a phenylcarbazole skeleton (JP-A-8-
60144), N-vinylcarbazole polymer (Japanese Patent Laid-Open No. 8-60145) and the like.

The thickness of such an interface layer is usually 2 to 100.
nm, preferably 5 to 30 nm.

Further, instead of providing the interface layer, the light emitting layer 5
Alternatively, a region containing 50% by weight or more of the material of the interface layer may be provided in the vicinity of the interface of the electron transport layer 6 on the cathode 7 side.

It is also possible to have a structure opposite to that of FIG. 1, that is, a cathode 7, a light emitting layer 5, a hole transporting layer 4, and an anode 2 may be laminated in this order on the substrate, and as described above, at least one It is also possible to provide the organic electroluminescent element of the present invention between two highly transparent substrates. Similarly, it is also possible to stack the layers in a structure opposite to that of each layer structure shown in FIG.
Further, in addition to the layers shown in FIGS. 1 and 2, any layer may be provided between the anode or cathode and the light emitting layer.

The organic electroluminescent device of the present invention is either a single device, a device having a structure arranged in an array, or a structure having an anode and a cathode arranged in an XY matrix. Can also be applied in.

According to such an organic electroluminescence device, the hole transport layer contains a compound having a binaphthyl skeleton and a high Tg, so that an organic electroluminescence device excellent in heat resistance and driving stability is provided. To be done.

Since the binaphthyl compound of the present invention can be basically used for the hole injecting / transporting layer, it is not limited to the hole transporting layer in FIGS. It can be adopted for any of the layers provided.

[0123]

EXAMPLES Next, the present invention will be described more specifically with reference to Synthesis Examples, Examples and Comparative Examples. However, the present invention is limited to the description of the following Examples unless the gist thereof is exceeded. is not.

Synthesis Example 1: Synthesis of Exemplified Compound (6) Using 1,1-bi-2-naphthol as a starting material, known literature J. A.
m. Chem. Soc., 101,3035 (1979), Tetrahedron Asym.,
According to the method described in 1825, (1997), Chem. Let., 411 (1985), etc., a binaphthyl compound represented by the following structural formula (No. (6) in Table 2) was synthesized.

[0125]

[Chemical formula 23]

5.5 g of 2,2'-dimethoxy-6,6'-diiodo-1,1'-binaphthalene having the structural formula shown below.
(9.71 mmol), potassium carbonate 4.36 g (31.6 mmol), copper 0.6
8g (10.7mmol), diphenylamine 4.10g (24.3mmol)
15 ml of tetraethylene glycol dimethyl ether was added to the mixture, and the mixture was reacted under nitrogen at 220 ° C. for 8 hours.

[0127]

[Chemical formula 24]

After completion of the reaction, the reaction solution was poured into methanol and the precipitate was separated by filtration. Further, excess potassium carbonate was removed by washing with water, chloroform and the like were added, and insoluble matter was separated by filtration. The solvent was removed by concentration or the like to obtain 4.5 g of a yellowish brown powder.

The product was purified by sublimation to recover 3.07 g. The yield was 48.7%. Mass spectrometry of this compound confirmed that it had a molecular weight of 648 and that it was the target compound by IR spectrum and NMR spectrum. The melting point was measured and found to be 307.6 ° C. Further, when measured by differential thermal analysis using a DSC-20 manufactured by Seiko Instruments Inc., Tg showed a high value of 126 ° C.

The IR absorption spectrum is shown in FIG. The absorption peaks are as follows. IR (cm ^-1 ): 3034, 2933, 2833 (C-
H) 1588, 1492 (C-C) 1350 (C-N), 1257 (C-O-C) ¹ H-NMR (CDCl ₃ (δ = ppm)): 3.78.
(S, 6H), 7.00 (tt, 4H), 7.06
(M, 4H), 7.13 (dd, 8H), 7.23 (d
d, 8H), 7.34 (d, 2H), 7.40 (s, 2)
H), 7.71 (d, 2H)

Example 1 An organic electroluminescent device having the structure shown in FIG. 2 was produced by the following method.

A transparent conductive film of indium tin oxide (ITO) having a thickness of 120 nm deposited on a glass substrate (manufactured by Geomatec Co., Ltd .; electron beam film-formed product; sheet resistance 15 Ω) was subjected to ordinary photolithography and hydrochloric acid etching. 2
The anode 2 was formed by patterning into a stripe having a width of mm. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, pure water, and ultrasonic cleaning with isopropyl alcohol, and then dried by nitrogen blow.
Finally, ultraviolet ozone cleaning was performed.

Next, as the anode buffer layer 3, an aromatic diamine-containing polyether (D-1) having the following structure; weight average molecular weight 25000; glass transition temperature 199 ° C.) and this (D-
1% of the following compound (E-1) was spin-coated on the above glass substrate under the following conditions. Solvent 1,2-dichloroethane Coating solution concentration 30 [mg / ml] Spinner rotation speed 2500 [rpm] Spinner rotation time 25 [second] Drying condition 90 minutes

[0134]

[Chemical 25]

[0135]

[Chemical formula 26]

By the above spin coating, the anode buffer layer 3 having a uniform film thickness of 30 nm was formed.

Next, the substrate 1 coated with the anode buffer layer 3 was placed in a vacuum vapor deposition apparatus. After performing rough evacuation of the above equipment with an oil rotary pump, the degree of vacuum in the equipment is 2 x 10
It was evacuated using an oil diffusion pump equipped with a liquid nitrogen trap until it became ^-6 Torr (about 2.7 x 10 ^-4 Pa) or less.

Ceramic crucible placed in this device
Put the Exemplified Compound (6) into the tantalum wire around the crucible
It vaporized by heating with a heater. The temperature of the crucible at this time
The temperature was controlled in the range of 276 to 303 ° C. Degree of vacuum during vapor deposition
2.8 x 10^-6Torr (about 3.7 × 10 ^-FourPa), deposition rate 0.2 ~
A hole transport layer 4 having a film thickness of 20 nm was formed at 0.3 nm / sec.

Subsequently, as the material of the light emitting layer 5, aluminum 8-hydroxyquinoline complex represented by the following structural formula, Al (C ₉ H ₆ NO) ₃ (B-1), was vapor-deposited in the same manner as the hole transport layer. I went.

[0140]

[Chemical 27]

At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex was controlled in the range of 282 to 310 ° C. The degree of vacuum during vapor deposition is 2.8 × 10 ^-6 Torr (approximately 3.7 × 10 ^-4 P
a), evaporation rate is 0.3-0.4 nm / sec, and light-emitting layer 5 with a film thickness of 75 nm
Was deposited.

The substrate temperature during vacuum deposition of the hole transport layer 4 and the light emitting layer 5 was kept at room temperature.

Here, the element on which the light emitting layer 5 has been vapor-deposited is once taken out from the vacuum vapor deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is used as a cathode vapor deposition mask for the ITO stripe of the anode 2. The elements were closely attached so as to be orthogonal to each other. This element was placed in another vacuum evaporation system, and the vacuum degree inside the system was 2 × 10 ⁻⁶ Torr as in the organic layer.
It was evacuated to r (about 2.7 × 10 ^-4 Pa) or less.

Subsequently, lithium fluoride was vapor-deposited using a molybdenum boat so that the film thickness would be 0.3 nm. The degree of vacuum during vapor deposition was 2.8 × 10 ⁻⁶ Torr (about 3.7 × 10 ⁻⁴ Pa). Further, aluminum was vapor-deposited on the upper portion of the aluminum using a molybdenum boat so as to have a film thickness of 100 nm to form a cathode 6. The degree of vacuum during vapor deposition is 3.5 × 10 ⁻⁵ Torr (approximately 4.6 ×
10 ⁻³ Pa), and the vapor deposition time was 3 minutes and 46 seconds.

The substrate temperature during deposition of the cathode 6 was kept at room temperature.

As described above, an organic electroluminescence device having a light emitting area portion having a size of 2 mm × 2 mm was obtained. Table 15 shows the light emission characteristics of this device.

In Table 15, the luminous brightness is a value at a current density of 250 mA / cm ² , the luminous efficiency is a value at 100 cd / m ² , the brightness / current is the slope of the brightness-current density characteristic, and the voltage is 100 cd / m 2. The values at ² are shown.

As shown in Table 15, the light emission starting voltage of this device was 2.3 V, and the use of the hole transporting layer containing the exemplified compound (6) achieved the lowering of the driving voltage, resulting in high brightness and high efficiency. It can be seen that the device of No. 1 was obtained.

Example 2 Rubrene (C-1) having the structure shown below was used in the light emitting layer 5.2.
An organic electroluminescence device was produced in the same manner as in Example 1 except that the film was uniformly doped at a concentration of 4% by weight in the film thickness direction.
Table 15 shows the light emission characteristics of this device. As is clear from Table 15, the improvement of the luminous efficiency was achieved by the doping of rubrene.

[0150]

[Chemical 28]

Comparative Example 1 Example 1 was repeated except that the aromatic diamine (A-3) was used as the material of the hole transport layer 4 instead of the exemplified compound (6).
An organic electroluminescent device was prepared in the same manner as in. Table 15 shows the light emission characteristics of this device. As shown in Table 15, the light emission starting voltage of this device was as high as 3.0V.

[0152]

[Table 15]

[0153]

As described above in detail, according to the present invention, T
A binaphthyl compound having a high g and being thermally stable is provided.

By using such a binaphthyl compound of the present invention in the hole transporting layer, an element having improved heat resistance can be obtained, further low voltage driving is possible, and an organic electric field exhibiting stable emission characteristics is obtained. A light emitting device can be obtained.

Therefore, the organic electroluminescent device according to the present invention is used in the field of flat panel displays (for example, wall-mounted televisions for OA computers) and light sources (for example, light sources for copiers, liquid crystal displays, etc.) that take advantage of its characteristics as a surface light emitter. It is considered to be applied to backlight sources of measuring instruments), display boards, and marker lights, and its technical value is particularly great as an on-vehicle display element that is required to have light resistance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of an organic electroluminescence device of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the embodiment of the organic electroluminescent element of the present invention.

FIG. 3 is the binaphthyl compound I synthesized in Synthesis Example 1.
It is an R spectrum.

[Explanation of symbols]

1 substrate 2 anode 3 Anode buffer layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 cathode

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3K007 AB02 AB03 AB06 AB11 AB14                       BA06 CA01 CB01 DA01 DB03                       EB00                 4H006 AA01 AA02 AB92 AC52 BJ50                       BP30 BU48

Claims (8)

[Claims] 1. A binaphthyl compound represented by the following general formula (I): [Chemical 1] (In the general formula (I), Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ each independently represent a 5- or 6-membered aromatic hydrocarbon ring or aromatic heterocycle which may have a substituent, It represents a monocyclic group or a condensed ring group, and Ar ₁ and Ar ₂ , or Ar ₃ and Ar ₄ may be bonded to each other to form a ring, m and n each represent an integer of 0 to 4, and m + n ≧ 1. Further, the naphthalene ring in the formula may have any substituent other than —NAr ₁ Ar ₂ and —NAr ₃ Ar _4. ) 2. In the general formula (I), naphthalene
The ring has -NAr ₁Ar₂And -NAr₃Ar_FourOther than
Even if the substituent has a halogen atom, a hydroxyl group, or a substituent
Good alkyl group, optionally substituted alkoxy
Group, alkenyl group which may have a substituent and substituent
A group consisting of alkoxycarbonyl groups which may have
It is selected from the group consisting of:
Chill compound. 3. A binaphthyl compound is represented by the following general formula (II):
The binaphthyl compound according to claim 1 or 2, characterized in that: [Chemical 2] (In the general formula (II), Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , m and n have the same meanings as in the general formula (I), and R ₁ ,
R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group which may have a substituent, an alkoxy group which may have a substituent. ,
It represents an alkenyl group which may have a substituent or an alkoxycarbonyl group which may have a substituent. ) 4. In the general formula (I) or (II), Ar
_{4. 1} and Ar ₂ and / or Ar ₃ and Ar ₄ are bonded to each other to form a ring.
The binaphthyl compound according to the item. 5. A binaphthi represented by the following general formula (III):
Represented by the following general formulas (IVa) and (IVb)
A contract characterized by reacting with an aromatic amine derivative
The binaphthyl system according to any one of claims 1 to 4.
Compound manufacturing method. [Chemical 3] (X in the general formula (III)₁And X_TwoAre each independently halogen
Represents a hydrogen atom, and m and n have the same meaning as in formula (I).
Is. Further, the naphthalene ring in the formula is X₁And X _TwoOther than
In addition, it may have an arbitrary substituent. ) [Chemical 4] (Ar in the general formula (IVa)₁And Ar_Two, The general formula (IV
Ar in b)_ThreeAnd Ar_FourIs the same as in general formula (I)
Righteous. ) 6. A binaphthyl derivative represented by the following general formula (V) is reacted with an aromatic halogen compound represented by the following general formula (VI).
A method for producing the binaphthyl compound according to any one of 1. [Chemical 5] (In the general formula (V), m and n have the same meanings as in the general formula (I). Further, the naphthalene ring in the formula may have an arbitrary substituent in addition to -NH ₂ . ) [Chemical 6] (In the general formula (VI), X'represents a halogen atom and Ar '
Is synonymous with Ar ₁ to Ar ₄ in the general formula (I). ) 7. The method according to any one of claims 1 to 4 between the anode and the cathode.
10. An organic electroluminescent device having a layer containing the binaphthyl compound according to any one of 1. 8. The organic electroluminescent device according to claim 7, further comprising a light emitting layer between the cathode and the layer containing the binaphthyl compound.