JPH06248260A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain an electroluminescent element, constructed from the anode, the cathode and a layer, sandwiched therebetween and comprising a specific organic compound as a constituent component, capable of sustaining luminous performance for a long period, excellent in durability and useful as a low-power consumption illuminant, etc. CONSTITUTION:The electroluminescent element is constructed from the anode such as nickel, the cathode such as silver and one or plural layers sandwiched therebetween. The one or more layers thereof are constructed from an organic compound of the formula [Ar is (substituted)alkyl, (substituted)aryl or (substituted)heterocyclic aromatic group].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a light emitting layer made of a light emitting material, and can directly convert electric energy into light energy by applying an electric field, and can be used as a conventional incandescent lamp, fluorescent lamp or light emitting diode. In contrast, the present invention relates to an electroluminescent device that enables realization of a low power consumption light emitter, a micro volume light emitter, a light weight light emitter, or a large-area planar light emitter.

[0002]

2. Description of the Related Art In recent years, with the diversification and space saving of information equipment, there is an increasing need for a flat display device which consumes less power and occupies less space than a CRT. Liquid crystal, plasma displays, etc. are available as such flat display elements. Recently, in particular, self-emission type displays have a clear display.
In addition, there are increasing expectations for organic electroluminescent devices that can be driven with a constant DC voltage. A device structure of an organic electroluminescent device has so far been a two-layer structure (a structure in which a hole transport layer and a light emitting layer are formed between a hole injection electrode and an electron injection electrode (SH
-A structure) (JP-A-59-194393, Appl.
Phys. Lett. 51, 913 (1987), or a structure in which a light emitting layer and an electron transport layer are formed between a hole injecting electrode and an electron injecting electrode (SH-B structure) (USP).
No. 5,085947, JP-A-2-25092, A
ppl. Phys. Lett. 55, 1489 (198
9)), or a three-layer structure (a structure in which a hole transport layer, a light emitting layer, and an electron transport layer are formed between a hole injection electrode and an electron injection electrode (DH structure) (Appl. Phys. Le).
tt. 57, 531 (1990)) has been reported.

As the hole injecting electrode, Au or IT is used.
An electrode material having a large work function such as O (indium tin oxide) is used, and Ca, Mg, A is used as the electron injection electrode.
Electrode materials having a low work function such as 1 and the like and alloys thereof are used. Until now, the hole transport layer, the light emitting layer,
Various organic compounds have been reported as materials that can be used for the electron transport layer. Examples of organic materials used for these are aromatic tertiary amines for the hole transport layer, and aluminum trisoxine for the light emitting layer material (JP-A-59-194393, JP-A-63-29569).
5), styrylamine derivatives, styrylbenzene derivatives and the like (JP-A-2-209988), and as the electron transport layer, oxadiazole derivatives and the like (Journal of the Chemical Society of Japan N
o. 11, p1540 (1991) has been reported.
Up to now, by using various element structures and organic materials, an element with high-luminance light emission of 1000 cd / m ² or more and a driving voltage of about 10 V has been obtained initially. In the organic material, a decrease in light output and an increase in driving voltage are observed in a few hours, and there is a big problem in the long-term durability of the EL element. Particularly in blue light emitting devices, the search for materials has not been sufficiently conducted, and many problems such as improvement in light emission efficiency remain. Carrier injection type electroluminescent devices using organic compounds as light emitters, including these examples, have a short history of research and development, and it cannot be said that the material research and device research have been sufficiently conducted. The reality is that there are many problems such as further improvement of brightness, control of emission wavelength, and improvement of durability.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to have sufficient luminance and excellent durability for long-term emission performance. It is to provide an organic electroluminescence device (organic EL device).

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies on the constituent elements of an organic EL device for solving the above problems, and as a result, have formed an anode and a cathode and one or more layers sandwiched between them. In the electroluminescent layer element constituted by the organic compound layer, the electroluminescent element effective for the above problems is obtained by forming at least one of the organic compound layers as a layer containing a specific thiazole compound as a constituent component. I found what I could offer.

[0006] Further, an electroluminescent device containing one or more light emitting layers and one or more electron transport layers as components between the anode and the cathode, or one or more hole transport layers and one layer between the anode and the cathode. In an electroluminescent device containing the above light emitting layer and one or more electron transport layers as constituent elements, at least one of the electron transport layers is more effective by using a layer containing a specific thiazole compound as a constituent component. It has been found that an electroluminescent device can be provided.

Further, an electroluminescent device containing one or more hole transport layers and one or more light emitting layers as components between the anode and the cathode, or one or more hole transport layers between the anode and the cathode. And an electroluminescent device having one or more light emitting layers and one or more electron transport layers as constituent elements, or an electroluminescent device having an organic single layer device structure in which a light emitting layer is formed between an anode and a cathode, It has been found that the same effective electroluminescent device can be provided by forming at least one of the layers as a layer containing a specific thiazole compound as a constituent.

That is, according to the present invention, in an electroluminescent device composed of an anode and a cathode and one or a plurality of layers of an organic compound sandwiched therebetween, at least one of the organic compound layers is Provided is an electroluminescent device comprising a layer containing an organic compound represented by the general formula (I) (Chemical Formula 1) as a constituent component.

[Chemical 1] (In the formula, Ar represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic aromatic ring.) Further, according to the present invention, between the anode and the cathode. , An electroluminescent device containing one or more light emitting layers and one or more electron transport layers as constituent elements, or one or more hole transport layers and one or more light emitting layers and one or more electron transports between an anode and a cathode. In an electroluminescent device containing a layer as a constituent element, at least one of the electron transport layers is a layer containing an organic compound represented by the general formula (I) (Formula 1) as a constituent component. And an electroluminescent device containing at least one hole transport layer and at least one light emitting layer as constituent elements between the anode and the cathode, or between the anode and the cathode. An electroluminescent device containing the above hole transport layer and one or more light emitting layers and one or more electron transport layers as constituent elements, or an electric field having an organic single layer device structure in which a light emitting layer is formed between an anode and a cathode. In the light-emitting device, at least one of the light-emitting layers is a layer containing an organic compound represented by the general formula (I) (Chemical formula 1) as a constituent component.

The present invention is one in which a specific thiazole compound is contained in at least one layer of the organic compound layer as described above. The compound represented by the general formula (I) (Formula 1) will be described below. A specific example will be described. However, the present invention is not limited to these.

Examples of Ar in the thiazole compound represented by the general formula (I) include the following. First,
When Ar is an alkyl group, the alkyl group has 1 carbon atom.
-6, preferably a linear or branched alkyl group having 1 to 4 carbon atoms. Further, Ar is an aryl group,
Heterocyclic aromatic rings include phenyl, naphthyl, anthryl, acenaphthenyl, fluorenyl, pyrenyl, phenanthryl, styryl, pyrimidyl, furanyl, pyrrolyl, thiophenyl, quinolyl, benzofuranyl, benzothiophenyl, indolyl, carbazolyl, benzoxazolyl, quinoxalyl. Etc.

A substituent of Ar in the general formula (I)
Then, the following groups can be specifically mentioned. (1) Halogen atom, hydrogen atom, trifluoromethyl
Group, cyano group, nitro group, (2) alkyl group; preferably C₁~ C₆Especially C₁~
C_FourIs a linear or branched alkyl group. (3) Aryl group; carbocyclic or heterocyclic aromatic ring
Yes, phenyl, naphthyl, anthryl, acenaphthenic
Le, fluorenyl, phenanthryl, indenyl, pyret
Nyl, pyridyl, pyrimidyl, furanyl, pyronyl, thiyl
Ophenyl, quinolyl, benzofuranyl, benzothiof
Phenyl, indolyl, carbazolyl, benzoxazoli
, Quinoxalyl, benzimidazolyl, pyrazolyl,
Dibenzofuranyl, dibenzothiophenyl, etc.
These aryl groups also include halogen atoms, hydroxyl groups, and cyano groups.
Group, nitro group, alkyl group, aryl group, alkoxy
It may be substituted with a group, an amino group or the like. (4) Alkoxy group (-OR¹): R¹Is defined in (2)
Represents an alkyl group. (5) Aryloxy group; defined as the aryl group in (3)
The defined group is shown. (6) Alkylthio group (-SR²): R²Is defined in (2)
The group represented by Acyl group such as alkyl group, acetyl group, benzoyl group,
Or represents an aryl group as defined in (3),
R such as a dil group and a morpholyl group³And R^FourIs a nitrogen atom
You may form a ring jointly. Also like the urolysyl group
It may form a ring in cooperation with the carbon atom on the aryl group. (8) Alkoxycarbonyl group (-COOR^Five): R^FiveIs
Alkyl group defined in (2) or defined in (3)
Represents an aryl group. (9) Acyl group (-COR^Five), A sulfonyl group (-SO₂
R^Five), Carbamoyl group  And R^FiveRepresents the meaning defined above. However, R³And R
^FourForm a ring with a carbon atom on the aryl group in
Except when (10) Methylenedioxy group or methylenedithio group, etc.
An alkylenedioxy group or an alkylenedithio group. (11) Styryl group (-CH = CH-C₆H_Five-R^Five) R^FiveIs a substituent or hydrogen atom defined in (1) to (10)
Represents

Next, specific examples of the thiazole compound represented by the above general formula (I) used in the present invention are shown below.

[Table 1]

The electroluminescent device according to the present invention is obtained by subjecting the above-described organic compound to a vacuum deposition method, a solution coating method, or the like.
The thickness of the entire organic compound layer is smaller than 0.5 μm, more preferably, the organic compound layer is formed by thinning each organic compound layer to a thickness of 10 nm to 100 nm, and the organic compound layer is directly or indirectly sandwiched between the anode and the cathode. It is composed of In addition, when the constituent organic compound is extremely rich in thin film forming ability, it is possible to form a layer with a film thickness of 10 nm or less. Also, a plurality of other substances may be added as an additive to each organic compound layer.

The electroluminescent device of the present invention is one in which a bias is electrically applied to the light emitting layer to cause light to be emitted. However, a short pinhole may cause a short circuit and the device may not function as an element. For formation, it is desirable to use a compound having excellent film forming properties together. Further, it is possible to form an organic compound layer by combining a compound having such excellent film-forming property with a polymer binder. Examples of the polymer binder that can be used in this case include polystyrene, polyvinyltoluene, poly-N-vinylcarbazole, polymethylmethacrylate, polymethylacrylate, polyester, polycarbonate and polyamide.

As the anode material, nickel, gold, platinum,
Palladium, alloys of these, or tin oxide (Sn
O ₂ )), tin oxide-indium (ITO), copper iodide and other metals having a large work function, alloys and compounds thereof,
Further, a polyalkylthiophene such as poly (3-methylthiophene) or a conductive polymer such as polypyrrole or polyarylene vinylene can be used. It may be a laminate of a metal and a conductive polymer. On the other hand, as the cathode material, silver, tin, lead, calcium, magnesium, manganese, indium, aluminum, or an alloy thereof having a small work function is used. At least one of the materials used as the anode and the cathode is preferably sufficiently transparent in the emission wavelength region of the device. Specifically 8
It is desirable to have a light transmittance of 0% or more. But,
In the case of an edge emitting device, it is preferable that both electrodes have high light reflectance.

The electroluminescent device of the present invention is constructed by laminating each of the above layers on a transparent substrate such as glass or a plastic film in order to improve the stability of the device, particularly moisture in the atmosphere. In order to protect against oxygen, a separate protective layer is provided, or the entire device is placed in the cell,
Silicon oil, a desiccant, or the like may be enclosed, or may be enclosed in a vacuum cell.

The present invention will be described in more detail below with reference to the drawings. 1 to 7, 1 is a substrate, 2 and 4 are electrodes, 3a is a light emitting layer, 3b is an electron transport layer, and 3c is a hole transport layer. FIG. 1 shows a structure in which an electrode 2 is provided on a substrate, a light emitting layer 3a is independently provided on the electrode 2, and an electrode is provided thereon. 2 shows an electrode 2 and a light emitting layer 3a in FIG.
The hole transport layer 3c is provided between the two. FIG. 3 shows an electron transport layer 3b provided between the light emitting layer 3a and the electrode 4 in FIG. In FIG. 4, the hole transport layer 3c is provided between the electrode 2 and the light emitting layer 3a in FIG. Although typical configuration examples have been illustrated above, these are the most basic configuration examples, and layers for improving charge transportability may be inserted in various places. For example, in FIG.
2 is a case where the hole transport layer 3c is composed of at least two layers or more in FIG. 2, and FIG. 6 is a case where the electron transport layer 3b is composed of at least two or more layers in FIG. Further, FIG. 7 shows a case where either or both of the hole transport layer and the electron transport layer in FIG. 4 are composed of at least two layers. It is also applied to the case where a tandem type laminated structure having a plurality of light emitting layers is adopted. Also,
In the present invention, it is desirable that the transparent anode is formed on the transparent substrate to have the structure shown in FIGS. 1 to 7, but the reverse structure may be adopted depending on the case.

As the various materials used in combination in the present invention, any materials can be used as long as they have functions such as hole transporting property, electron transporting property, and light emitting property.
For example, the following conventionally known ones can be used.

The material for the light emitting layer is preferably a substance which has strong fluorescence in a solid state and forms a dense film in a thin film of 50 nm or less. All the conventionally known materials that have been used for the light emitting layer of the organic EL device so far are the organic EL of the present invention
It can be applied to devices. For example, a metal chelated oxinoid compound (8-hydroxyquinoline metal complex) (JP-A-49-194393, JP-A-63-295).
695), butadiene derivatives such as 1,4 diphenylbutadiene and tetraphenylbutadiene, coumarin derivatives, benzoxazole derivatives, oxadiazole derivatives, oxazole derivatives, thiadiazole derivatives,
Styrylamine derivatives, bisstyrylbenzene derivatives (JP-A-2-247277), trisstyrylbenzene derivatives (JP-A-3-296595), bisstyrylanthracene derivatives (JP-A-3-163186), perinone derivatives, aminopyrene derivatives and the like have excellent light emission. It is a layer material. Specific examples of the light emitting layer material useful in the present invention are shown below.

[0020]

[Table 3- (1)]

[0021]

[Table 3- (2)]

[0022]

[Table 3- (3)]

As the hole transport layer material, all the materials which have been used as the hole transport layer material so far can be used, but at least two aromatic tertiary amines are contained and the aromatic tertiary amine is contained. Compounds in which is a monoarylamine, diarylamine, triarylamine are preferred. USP as a typical useful aromatic tertiary amine
No. 4,175,960, USP No. 4,53
The compounds disclosed in 9,507, 63-264692 can be utilized. Also, USP N
o. Porphyrin derivatives (phthalocyanines) disclosed in 4,720,432 are also useful compounds. Specific examples of useful hole transport layer materials are shown below.

[0024]

[Table 4- (1)]

[0025]

[Table 4- (2)]

As the electron transport layer material, all known materials which have been used as the electron transport layer material so far can be used. One preferable electron transporting material is a compound containing at least one oxadiazole ring which is an expression unit having an electron transporting ability. Representative useful oxadiazole compounds are described in Appl. Phys. Let
t55, 1489 (1989) and the Chemical Society of Japan 15
40 (1991). Furthermore, preferred organic materials for use in the electron transport layer of the laminated electroluminescent device of the present invention are metal chelated oxinoid compounds including chelates of 8-hydroxyquinoline. further,
Other preferred electron transport layer materials include butadiene derivatives such as 1,4 diphenylbutadiene and tetraphenylbutadiene, coumarin derivatives, bisstyrylbenzene derivatives, bisstyrylanthracene derivatives, benzoxazole derivatives, oxadiazole derivatives, oxazole derivatives, Examples thereof include thiadiazole derivatives, naphthalimide derivatives, perylenetetracarboxylic acid diimide derivatives, quinacridone derivatives and the like. Specific examples of these are shown below.

[0027]

[Table 5]

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 A hole-transporting layer having a thickness of 50 nm formed of a diamine derivative represented by the hole-transporting material C-12 on a glass substrate having an indium tin oxide (ITO) anode having a surface resistance of 20 Ω / □, the above general formula ( I) structural formula No. A 50-nm-thick light-emitting layer made of the compound 12 and a 200-nm-thick anode made of a MgAg alloy having an atomic ratio of 10: 1 were sequentially laminated by vacuum vapor deposition to prepare an electroluminescence device as shown in FIG. The degree of vacuum during vapor deposition is about 0.7 × 10 ⁻⁶ torr, and the substrate temperature is room temperature. When a direct current power supply was connected to the anode and cathode of the device thus produced through a lead wire, the applied voltage was 20 V at a current density of 50 mA / cm ² , and clear green light emission was confirmed for a long time. At this time, the emission wavelength had a peak at 520 nm and the luminance was 800 cd / m ² . In addition, clear luminescence was recognized even after this device was stored at room temperature for one month.

Example 2 A light emitting layer having a thickness of 50 nm made of the diamine derivative represented by the light emitting layer material (B-8) on a glass substrate having an indium tin oxide (ITO) electrode having a surface resistance of 20 Ω / □.
The compound of the general formula (I) No. 50 nm thick electron transport layer consisting of 12 compounds, 10: 1 atomic ratio of MgAg
An anode made of an alloy and having a thickness of 200 nm was successively deposited by vacuum vapor deposition to manufacture an electroluminescence device as shown in FIG.
The degree of vacuum during vapor deposition is about 0.7 × 10 ⁻⁶ torr, and the substrate temperature is room temperature. When a direct current power supply was connected to the anode and cathode of the device thus produced through a lead wire, the applied voltage was 8 V at a current density of 30 mA / cm ² .
And clear blue-green light emission was confirmed for a long time. The emission wavelength at this time has a peak at 475 nm,
The brightness was 230 cd / m ² . In addition, clear luminescence was observed in this device even after storage for 1 month at room temperature.

Example 3 An electroluminescent device as shown in FIG. 3 was produced in the same manner as in Example 2 except that the compound B-1 as the light emitting layer material was used as the light emitting layer. When a direct current power source was connected to the anode and cathode of the element thus created through lead wires,
Applied voltage is 9.5 V at current density of 30 mA / cm ² .
The clear green emission was confirmed for a long time. At this time, the emission wavelength had a peak at 510 nm and the brightness was 650 cd / m ² . In addition, clear luminescence was observed in this device even after storage at room temperature for 1 month.

Example 4 A hole transport layer having a film thickness of 350Å using the hole transport layer material C-12, a light emitting layer having a film thickness of 150Å using the light emitting layer material B-8, and an electron transport layer having the general formula Compound N of (I)
o. An electron-transporting layer having a film thickness of 500 Å was laminated using the compound of No. 12 to manufacture an electroluminescence device as shown in FIG. When a direct current power supply was connected to the anode and cathode of the device thus produced through a lead wire, the current density was 30 mA /
In cm ² , the applied voltage was 8.5 V, and clear blue light emission was confirmed for a long time. At this time, the emission wavelength had a peak at 480 nm and the brightness was 320 cd / m ² . In addition, clear luminescence was observed in this device even after storage at room temperature for 1 month.

Comparative Example 1 In Example 2, the compound No. 1 of the general formula (I) used for the electron transport layer was used. 12 except that the compound represented by the electron transport layer material D-1 was used in place of the compound of 12.
An electroluminescent device was produced in the same manner as in Example 2. When this device was made to emit light in the same manner as in Example, blue-green light emission was observed, but this device did not emit light after storage for one month at room temperature.

[0033]

In the electroluminescent device of the present invention, the compound represented by the general formula (I) (Chemical formula 1) is used as a constituent material of the organic compound. It has excellent properties.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electroluminescent device in which a light emitting layer is sandwiched between two electrodes.

FIG. 2 is a schematic cross-sectional view of an electroluminescent device having a light emitting layer and a hole transport layer sandwiched between two electrodes.

FIG. 3 is a schematic cross-sectional view of an electroluminescent device having a light emitting layer and an electron transport layer sandwiched between two electrodes.

FIG. 4 is a schematic cross-sectional view of an electroluminescent device in which a hole transport layer, a light emitting layer, and an electron transport layer are sandwiched between two electrodes in that order.

FIG. 5 is a schematic cross-sectional view of an electroluminescence device having two or more hole transport layers in FIG.

FIG. 6 is a schematic cross-sectional view of an electroluminescent device having two or more electron transport layers in FIG.

FIG. 7 is a schematic cross-sectional view of an electroluminescent device in which one or both of a hole transport layer and an electron transport layer in FIG. 4 is composed of at least two layers.

[Explanation of symbols]

1 ... Substrate, 2, 4 ... Electrode, 3a ... Light emitting layer, 3b ...
... electron transport layer, 3c ... hole transport layer.

Front page continuation (72) Inventor Masafumi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. An electroluminescent device comprising an anode and a cathode and one or a plurality of layers of an organic compound sandwiched therebetween, wherein at least one of the organic compound layers has the following general formula (I) ( An electroluminescent device comprising a layer containing an organic compound represented by Chemical formula 1) as a constituent component. [Chemical 1] (In the formula, Ar represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic aromatic ring.) 2. An electroluminescent device containing one or more light emitting layers and one or more electron transport layers as constituent elements between an anode and a cathode, or one or more hole transport layers and one layer between an anode and a cathode. In the electroluminescent device containing the above light emitting layer and one or more electron transport layers as constituent elements, at least one of the electron transport layers comprises the organic compound represented by the general formula (I) according to claim 1. An electroluminescent device comprising a layer as a constituent component. 3. An electroluminescent device containing, as components, one or more hole transport layers and one or more light emitting layers between an anode and a cathode, or one or more hole transport layers between an anode and a cathode. An electroluminescent device comprising one or more light emitting layers and one or more electron transport layers as constituent elements, or an electroluminescent device having an organic single layer device structure in which a light emitting layer is formed between an anode and a cathode, wherein At least one layer is a layer containing the organic compound represented by the general formula (I) according to claim 1 as a constituent component.