JPH06122874A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain the subject element, having a higher luminous intensity and high durability at a practical level and useful as a planar light source, a flat display, etc., by forming a layer containing a specific organic compound. CONSTITUTION:The objective element is obtained by forming a layer containing an organic compound of formula I [R1 is (substituted)phenyl, biphenyl, benzyl, etc.; R2 and R3 are (substituted)alkyl, aryl, nitro, etc.], e.g. a compound of formula II. Although an element having a construction of, e.g. substrate/anode/ luminous layer/cathode, substrate/anode/positive hole injecting layer/luminous layer/cathode or substrate/anode/luminous layer/electron injecting layer/cathode is cited as the element, this compound of formula I is preferably used in the luminous layer or the electron injecting layer. Furthermore, the luminous layer is preferably formed into a film having 20-150nm thickness thereof by a vacuum deposition, a casting methods, etc. The electron injecting layer is preferably formed into a film having 30-200nm thickness thereof according to the similar method.

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, and more particularly to an organic electroluminescence device used for flat light sources, flat displays and the like.

[0002]

2. Description of the Related Art Organic electroluminescent devices are
It is composed of an organic light emitting layer and a pair of counter electrodes sandwiching the layer, and its light emission is recombined in the light emitting layer by electrons injected from one electrode and holes injected from the other electrode. It occurs when the luminescent material is excited to a higher energy level, and when the excited luminescent material returns to its original ground state, it emits energy as light. In this way, the carrier injection type electroluminescence element is
Since the use of organic compound thin films, those having strong emission intensity have been obtained. For example, U.S. Pat.No. 3,530,325 uses a single crystal anthracene or the like as a light emitter, and JP-A-59-194393 discloses a combination of a hole injection layer and an organic light-emitting layer, JP-A-63-295695. Is a combination of a hole injection transport layer and an organic electron injection transport layer, and
Jpn.Journal of Applied Physics, vol.27, No2, P26
9 to 271 disclose a combination of a hole transfer layer, a light emitting layer, and an electron transfer layer, and these have improved the emission intensity.

However, in the conventional organic electroluminescence device having the above-mentioned structure, although the emission intensity has been improved, there is a problem in durability and the emission intensity and durability of practical level have not yet been reached. . Therefore, it has been desired to develop an organic electroluminescence device having higher emission intensity and higher durability.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a practical level organic electroluminescent device having higher emission intensity and higher durability. .

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have made up a pair of counter electrodes and one or a plurality of organic compound layers sandwiched by these counter electrodes. In the electroluminescence device described above, at least one or more layers containing an organic compound represented by the following general formula [1] or [2] are provided to achieve an organic electroluminescence device. I found a thing.

[0006]

[Chemical 3]

(R ₁ represents a substituted or unsubstituted phenyl group, biphenyl group, benzyl group, alkyl group or alkoxy group, and R ₂ and R ₃ represent substituted or unsubstituted alkyl group, alkoxy group or aralkyl group. , An aryl group, a substituted or unsubstituted alkylamine group, a halogenated alkyl group, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a substituted or unsubstituted heterocyclic group, and the like, R ₂ = R ₃ , R ₂ It does not matter which ≠ R _3. )

[0008]

[Chemical 4]

(R ₁ and R ₂ are substituted or unsubstituted alkyl group, alkoxy group, aralkyl group, aryl group, substituted,
It represents an unsubstituted alkylamino group, a halogenated alkyl group, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a substituted or unsubstituted heterocyclic group, etc., and may be any of R ₁ = R ₂ and R ₁ ≠ R _2. Absent. ) As the substituents of the phenyl group, biphenyl group and benzyl group represented by R _{1 in} the general formula [1], alkyl groups such as methyl group, ethyl group, propyl group and butyl group; methoxy group, ethoxy group and propoxy group. Base,
Alkoxy group such as butoxy group; substituted or unsubstituted amino group such as amino group, dimethylamino group, diethylamino group, di-t-butylamino group, hydrogen atom, chlorine atom, bromine atom, iodine atom, fluorine atom And halogen atoms such as. Further, as the alkyl group represented by R ₁ ,
Substituted or unsubstituted alkyl group such as methyl group, ethyl group, propyl group, butyl group; substituted or unsubstituted alkoxy group such as methoxy group, ethoxy group, propoxy group, butoxy group, etc. as alkoxy group; as alkylamino group Is a substituted or unsubstituted alkylamino group such as dimethylamino group, diethylamino group or di-t-butylamino group;
Examples of the carboxylic acid and its derivative include a substituted or unsubstituted alkoxycarbonyl group such as a carboxyl group, a methoxycarbonyl group and an ethoxycarbonyl group; examples of the halogen atom include a chlorine atom, a bromine atom, an iodine atom and a fluorine atom. A particularly preferred substituent of R ₁ is
Examples thereof include an alkyl group, a phenyl group and a biphenyl group.
Further, R ₂ , R ₃ in the general formula [1] and the general formula [2]
In the above, alkyl groups represented by R ₁ and R ₂ are substituted or unsubstituted alkyl groups such as methyl group, ethyl group, propyl group and butyl group; and alkoxy groups are methoxy group, ethoxy group, propoxy group, butoxy group. A substituted or unsubstituted alkoxy group such as a group; an aralkyl group which is a substituted or unsubstituted aralkyl group such as a benzyl group; an aryl group which is a substituted or unsubstituted aryl group such as a phenyl group, a naphthyl group or a biphenyl group; As the heterocyclic group, a substituted or unsubstituted heterocyclic group such as a pyridyl group, a triazolyl group, a thiazolyl group, a pyrrolyl group, a furyl group, an oxazolyl group, a benzimidazolyl group, or a benzothiazolyl group; a halogen atom, a chlorine atom or a bromine atom , Iodine atom, and fluorine atom.

Specific examples of the compounds represented by the general formulas [1] and [2] are shown below. However, these are merely specific examples, and the present invention is not limited thereto.

[0011]

[Chemical 5]

[0012]

[Chemical 6]

[0013]

[Chemical 7]

[0014]

[Chemical 8]

[0015]

[Chemical 9]

[0016]

[Chemical 10]

[0017]

[Chemical 11]

[0018]

[Chemical 12]

The structure of the organic electroluminescence device of the present invention has various modes, but basically it is composed of an organic light emitting layer and a pair of counter electrodes sandwiching the layer.
Specifically, (1) substrate / anode / light emitting layer / cathode (see FIG.
(1)), (2) substrate / anode / hole injection layer / light emitting layer / cathode (FIG. 1 (2)), (3) substrate / anode / light emitting layer / electron injection layer / cathode (FIG. 1 (3)) ), (4) substrate / anode / hole injecting layer / light emitting layer / electron injecting layer / cathode (FIG. 1 (4)), but the present invention is not necessarily limited to this configuration. A plurality of light emitting layers, a hole injection layer, and an electron injection layer may be provided, or a hole injection layer / light emitting layer, a light emitting layer / electron injection layer, and a hole injection layer / light emitting layer may be repeatedly laminated in each. , A mixed layer of an electron injection material and a light emitting material between the light emitting layer and the electron injection layer, a mixed layer of a hole injection material and a light emitting material between the hole injection layer and the light emitting layer, or each other. You may provide the layer of. The compounds of the general formulas [1] and [2] of the present invention are preferably used in the electron injection layer or the light emitting layer.

The light emitting layer is formed by a vapor deposition method, a spin coating method, a casting method or the like, and its film thickness is preferably 10 to 1000 nm, more preferably 20 to 150 nm. The hole injection layer is formed by a vapor deposition method, a spin coating method, a casting method, or the like, and its film thickness is preferably 10 to 1000 nm, more preferably 40 to 1000 nm.
It is 200 nm. The electron injection layer is formed by vapor deposition, spin coating,
It is formed by a casting method or the like, and its film thickness is preferably 10 to 1000 nm, more preferably 30 to 200 nm.

The substrate 1 is made of soda glass, non-fluorescent glass,
Glass plates such as phosphoric acid-based glass and silicic acid-based glass, quartz, acrylic resin, styrene-based resin, polycarbonate-based resin, epoxy-based resin, polyethylene, polyester, silicone-based resin and other plastic plates and plastic films, metal plates such as alumina. And metal foils are used.

The anode 2 preferably has a work function larger than 4 eV, such as carbon, aluminum, vanadium, iron,
Cobalt, nickel, chromium, copper, zinc, tungsten, silver, tin, platinum, gold and other metals and alloys thereof, zinc oxide, indium oxide, ITO, complex compounds such as tin oxide or indium oxide such as NESA, iodine Compounds such as copper oxide, mixtures of oxides and metals such as ZnO: Al, SnO ₂ : Sb, and derivative polymers such as poly (3-methylthiophene), polypyrrole, and polyaniline are used. The film thickness is preferably 10 to 1000 nm, more preferably 10
~ 200 nm.

The cathode 3 preferably has a work function of more than 4 eV, such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese, aluminum, silver, tin and lead. Metals and alloys thereof, aluminum / aluminum oxide composites and the like are used. The film thickness is preferably 10 to 1000 nm,
More preferably, it is 10 to 900 nm.

When light is extracted from the electrodes, at least one of the anode 2 and the cathode 3 is transparent or semitransparent with a transmittance of 10% or more, and only the anode 2 is transparent or semitransparent with a transmittance of 10% or more. When it is transparent, it is desirable that the substrate 1 is also transparent or semi-transparent.

Specific examples of the light emitting substance used in the light emitting layer 4 include oxinoid compounds (JP-A-63-295695, JP-A-2-15595, in addition to the organic compounds represented by the above general formulas).
2-66873, etc.), perylene compounds (“S
oluble Perylen Fluorenscent Dyes with Photostabil
, vol.115, P2927 (1982) ”,“ Jpn. Journal of App
lied Phyisics, vol.27, No2, P269 (1988) "," Bul
l.Chem.Soc.Jpn.vol.25, P411 (1952) ", European Patent 553,
353A1, JP-A-55-36849, JP-A-2-66873, etc.), coumarin compound (JP-A-57-51781, JP-A-2-66873, etc.), azacoumarin Compounds (described in JP-A-3-792, etc.), oxazole compounds (US Pat. No. 3,257,203, JP-A-3-93763)
Nos. 1 and 2), oxadiazole compounds (as described in US Pat. No. 3,189,447, JP-A-2-216791, etc.), perinone compounds (JP-A-2-88689, JP-A-2-88689, 2)
-289676, etc.), pyrrolopyrrole compounds (described in JP-A-2-296891, etc.), naphthalene compounds (JP-A-57-51781, JP-A-2-255789, etc.) Compound), anthracene compound (JP
56-46234, those described in JP-A-2-66873, etc.), fluorene compounds (JP-A-54-110837, JP-A-31683)
-162485), pyrene compounds (described in JP-A-57-51781, JP-A-3-162485, etc.), coronene compounds (described in JP-A-3-162485, etc.) ), A quinolone compound and an azaquinolone compound (described in JP-A No. 3-162483), a pyrazoline and a pyrazolone derivative (US Pat. Nos. 3,180,729 and 4,
278,746, JP-A-55-88064, JP-A-2-220394, 3-1
62486) and stilbene compounds (US Pat. No. 4,356,429, JP-A-57-51781, 61-2103).
63, 61-228451, 61-14642, 61-72255,
62-47646, 62-30255, 60-94462, 63-149
No. 652, JP-A Nos. 1-173034 and 1-245087, etc.), diphenoquinone compounds (“Polymer Prepri
nts, Japan, vol.37, p681 (1988) ", JP-A-3-152184, etc.) and styryl compounds (JP-A-1-24).
Nos. 5087 and 2-222484), butadiene compounds (described in US Pat. No. 4,356,429, JP 57-51781 etc.), anthracene compounds (JP
3-178942), cyanine compounds (described in JP-A-2-66873), acridine compounds (described in JP-A-57-51781), 8-hydroxyquinoline compounds Metal complexes of JP-A 2-8287 and 2-
8290), a complex of a Schiff salt and a group III metal (such as those described in JP-A 1-297490),
A fluorescent substance such as an oxine metal complex (described in JP-A No. 3-176993) or a rare earth complex (described in JP-A No. 1-256584) can be used.

Specific examples of the hole injecting compound having a hole transporting ability used for the hole injecting layer 5 include triazole compounds (described in US Pat. No. 3,112,197),
Oxadiazole derivatives (described in US Pat. No. 3,189,447), imidazole derivatives (Japanese Patent Publication No. 37-160)
96, etc.), polyarylalkane derivatives (US Pat. No. 3,615,402, Japanese Examined Patent Publication No. 45-555, Japanese Patent Laid-Open No. 5)
1-93224, 56-36656, etc.), pyrazoline derivatives and pyrazolone derivatives (US Patent 3,180,
729, JP-A-55-88064, JP-A-57-45545, etc.) and phenylenediamine derivatives (US Pat.
5,404, JP-B-51-10105, JP-A-54-53435, etc.), arylamine derivatives (US Pat.
175,961, JP-B-49-65702, JP-A-56-223437, West German Patent 1,110,518, etc.), oxazole derivatives (US Pat. No. 3,257,203, etc.), styryl anthracene derivatives (* Kaisho 56-462
34, etc.), fluorenone derivatives (described in JP-A-54-110837), hydrazone derivatives (US Pat. No. 3,717,462, JP-A-54-59143, JP-A-3-138654). Etc.), stilbene derivatives (described in JP-A-61-210363, JP-A-1-200262, etc.), porphyrin compounds (JP-A-63-29569).
5, those described in JP-A No. 2-1295), aromatic tertiary amine compounds and styrylamine compounds (US Pat. No. 4,127,412, JP-A-53-27033, JP-A-63-295695, JP-A No. 63-295695). 1-274154, 3-111485, etc.), butadiene compounds (those described in JP-A-3-111484, etc.), polystyrene derivatives (those described in JP-A-3-95291, etc.) ), Hydrazone derivatives (JP-A-3-
No. 137187), triphenylmethane derivative, tetraphenylbenzidine derivative (JP-A-3-54
Those described in No. 289) etc. can be used. Particularly preferably, a porphyrin compound and an aromatic third group
A primary amine compound and a styrylamine compound.

Specific examples of the electron injecting compound having an electron transporting ability used in the electron injecting layer 6 include nitro-substituted fluorenone derivative thiopyrandioxide derivatives and diphenoquinone derivatives (" Polymer Preprints, Japan, vol.37, No3, P681, (1
988) ”, those described in JP-A-3-152184, etc.), perylene tetracarboxyl derivatives (“ Jpn. Journal of A
pplied Physics, vol.27, No2, P269 (1988) "" Bull.C
hem.Soc.Jpn., vol.25, P411 (1952) ", etc.), anthraquinodimethane derivative (JP-A-57-149).
No. 259, 63-104061, etc.), a fluoronylidene methane derivative (JP-A-60-69657,
No. 61-148159, etc.), anthrone derivatives (the ones described in JP-A Nos. 61-225151 and 61-233750, etc.), and oxadiazole derivatives (JP-A No. 61-225151).
Compounds such as those described in 3-79692), perinone derivatives (described in JP-A-2-289676, etc.) and quinoline complex derivatives can be used.

[0028]

EXAMPLES The present invention will be described in detail with reference to examples.

Example 1 A substrate (P110E-H-PS manufactured by Nippon Sheet Glass Co., Ltd.) having a 150 nm ITO film formed on glass as an anode was patterned into a desired shape and then polished with water using an alumina abrasive. went. After washing with water, ultrasonically wash with water twice for 10 minutes and then 90 ℃
Was dried with hot air.

[0030] Next to this board, put compound shown in the following "Formula 13" the (A-1) to tungsten board (Japan Backs Metal Co., Ltd. SF208), 8.0 × 10 ^-7 Torr of 0.2nm under vacuum conditions / A hole injection layer of about 80 nm was formed at a film formation rate of sec.

Then, Compound Example No. 36 while maintaining a vacuum
Molybdenum boat (Japan Bucks Metal Co., Ltd. SS-1
-9), and an electron injection layer of about 60 nm was formed at a film formation rate of 0.2 nm / sec under a vacuum condition of 8.0 × 10 ^-7 Torr.

Furthermore, Mg:
Ag (10: 1 atomic ratio alloy) was vacuum-deposited at 50 nm to form a cathode.

An external power source was connected to the thus obtained organic electroluminescence device, a DC voltage of 18 V was applied, and the maximum luminance at that time was measured. Further, continuous lighting was performed by applying a direct current voltage of 18 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C., and the time at which the brightness was reduced to half was measured. The results are shown in Table 1.

Examples 2 to 6 The compounds used in the electron injection layer were replaced with the compounds shown in Table 1, and organic electroluminescent elements were obtained in the same manner as in Example 1. The characteristics are shown in Table 1.

Comparative Example (1) An element was prepared and measured in the same manner as in Example 1 except that the compound (B-1) described in "Chemical Formula 13" was used for the electron injection layer. The results are shown in Table 1.

[0036]

[Table 1]

Examples 7 to 12 Same as Example 1 except that the compound (A-2) described in "Chemical Formula 13" was used for the hole injection layer and the compound shown in Table 2 was used for the electron injection layer. Then, an organic electroluminescence device was prepared and measured. The results are shown in Table 2.

Comparative Example (2) A device was prepared and measured in the same manner as in Example 7 except that the compound (B-2) shown in Chemical formula 13 was used for the electron injection layer. The results are shown in Table 2.

[0039]

[Table 2]

[0040]

[Chemical 13]

Examples 13 to 23 A substrate (P110E-H-PS manufactured by Nippon Sheet Glass Co., Ltd.) on which ITO was deposited to a thickness of 150 nm on a glass as an anode was patterned into a desired shape, and was then treated with water using an alumina abrasive. Polished. After washing with water, ultrasonic washing with water was performed twice for 10 minutes, and further dried with hot air at 90 ° C.

Next, the above compound (A
-2) 0.03 g, 0.045 g of the compounds shown in Table 3 as an electron injection substance, 0.045 g of polymethacrylate which has been purified by reprecipitation twice as a binder resin, and these are dissolved in 10 ml of 1,2-dichloroethane. A coating liquid was prepared. This coating solution was applied to the above-mentioned substrate by a spin coater (Mikasa Co., Ltd. 1
H-D3 type) was applied under the conditions of 1000 rpm / 15 sec. To obtain a coating film of about 100 nm.

Further, under this vacuum condition of 8.0 × 10 ^-4 Torr, 50 nm of Mg: Ag (10: 1 atomic ratio alloy) was vacuum-deposited at a film forming rate of 0.2 nm / sec to form a cathode.

An external power source was connected to the thus obtained organic electroluminescent device, a direct current voltage of 18 V was applied, and the maximum luminance at that time was measured. Further, continuous lighting was performed by applying a DC voltage of 18 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C., and the time at which the brightness was reduced to half was measured. The results are shown in Table 3.

[0045]

[Table 3]

[0046]

By using the specific organic compound according to the present invention, it is possible to obtain an organic electroluminescence device which is sufficiently practical for emission intensity and durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an organic thin film electroluminescent element showing an embodiment of the present invention.

[Explanation of symbols]

 1 substrate 2 anode 3 cathode 4 light emitting layer 5 hole injection layer 6 electron injection layer

Claims (2)

[Claims] 1. An organic electroluminescence device comprising at least one layer containing an organic compound represented by the following general formula [1]. [Chemical 1] (R ₁ is a substituted or unsubstituted phenyl group, biphenyl group,
Represents a benzyl group, an alkyl group or an alkoxy group, R ₂ ,
R ₃ is a substituted or unsubstituted alkyl group, alkoxy group, aralkyl group, aryl group, substituted or unsubstituted alkylamine group, halogenated alkyl group, hydrogen atom, halogen atom, nitro group, cyano group, substituted or unsubstituted It represents a substituted heterocyclic group and may be either R ₂ = R ₃ or R ₂ ≠ R ₃ . ) 2. An organic compound represented by the following general formula [2]
Characterized by providing at least one layer containing
And an organic electroluminescent device. [Chemical 2](R₁, R₂Is a substituted or unsubstituted alkyl group, alkoxy
Groups, aralkyl groups, aryl groups, substituted and unsubstituted alkyl groups
Luamino group, halogenated alkyl group, hydrogen atom, halogen
Atom, nitro group, cyano group, substituted or unsubstituted heterocyclic group
And R ₁= R₂, R₁≠ R₂It doesn't matter which
Yes. )