JPH059471A - Organic electroluminescent device - Google Patents

Abstract

(57) [Summary] [Structure] At least one layer has the formula (1) An organic electroluminescent device which is a layer containing a compound represented by. [Effect] It has extremely good performance such as low voltage driving, high light emission intensity and high durability, and is extremely valuable in practical use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device capable of directly exchanging electric energy for light energy.

[0002]

2. Description of the Related Art As an electroluminescent device, one having a structure in which inorganic compound thin films are laminated is conventionally known, and a part thereof has already been put to practical use. Although these inorganic thin film layered electroluminescent devices have the advantage of high emission brightness, they have a high driving voltage of 100V to 200V and a high voltage endurance driving I
It has the drawbacks that C is required, the degree of freedom in hue selection is low because light emission is a bright line, and power consumption is large.

On the other hand, in recent years, an organic thin film laminated electroluminescent device has been devised and rapidly developed for practical use. For example, a report by Saito et al. (C. Adachi, S. Tok)
ito, Tsutsui, S .; Saito, Jp
n. J. Appl. Phyo. , Volume 27, L
269 pages and L7131 pages, 1988)
Indicated by. This is an element having a structure in which an organic light emitting thin layer is sandwiched between an electron transporting organic thin layer and a hole transporting thin layer, and electrodes are provided on both sides thereof. Compared with the inorganic thin film laminated type electroluminescent device, such an organic thin film laminated type electroluminescent device has a wide range of emission wavelengths and a wide range because of the existence of various light emitting materials, and the driving voltage is 10 V or less. It has attracted a great deal of attention because it has sufficient brightness and can easily be made large in area. However, under the present circumstances, there is a problem in durability performance that the emission luminance gradually decreases when used for a long time.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electroluminescent device which has good light resistance and high luminance driven by a low voltage.

[0005]

Means for Solving the Problems As a result of intensive studies on the constituent elements of the light emitting layer for solving the above problems, the present inventors have confirmed that the durability performance greatly varies depending on the type of the hole transport layer. Among them, the inventors have found that a fluorene-based amine compound is extremely effective as a hole transport compound, and completed the present invention.

That is, according to the present invention, in an organic electroluminescent device composed of one or more multi-layered organic compounds between two electrodes, at least one layer is represented by the following general formula (1):

[0007]

[Chemical 1]

[Wherein R¹Is an alkyl group or aralkyl
R group, R², R³, R^FourAnd R ^FiveIs a hydrogen atom,
A kill group, an alkoxy group or a halogen atom is shown. 〕so
A layer containing a compound represented by
Machine electroluminescent device.

Specific examples of R ¹ in the general formula (1) include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, n-hexyl group, 3,5,5-
Examples thereof include alkyl groups such as trimethylhexyl group, n-dodecyl group, n-hexadecyl group and n-octadecyl group, aralkyl groups such as benzyl group, 2-phenylethyl group and 4-methylbenzyl group, and R ² and R ³ , R ⁴ and R ⁵ include hydrogen atom, alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group and n-butyl group, methoxy group, ethoxy group, i-propyloxy group. Examples thereof include alkoxy groups such as groups, chlorine atoms, fluorine atoms, halogen atoms such as bromine atoms.

Next, the structure of the organic electroluminescent device of the present invention will be described with reference to the drawings. FIG. 1 is an example of a cross-sectional view of an electroluminescent device according to the present invention. In FIG. 1, 1
Is a substrate, 2 is an anode, 3 is a cathode, 4 is a power source, 5 is a light emitting layer,
6 is a hole transport layer, and 7 is an electron transport layer.

A glass substrate is generally used as the substrate 1, but a photomask grade polished non-alkali borosilicate glass is preferable.

The anode 2 is paired with the cathode 3 and is for applying an electric field to each layer constituting the organic electroluminescence device, such as nickel, gold, platinum, palladium tin oxide, indium tin oxide (ITO) and the like. Thin films of are preferred. The film thickness is 50 to 1000 Å, but in the case of an opaque electrode, it is necessary to set it to 300 Å or less. On the other hand, examples of the material of the cathode 3 include silver, tin, lead, magnesium, manganese, aluminum, and alloys thereof.

For the hole transport layer 6, a fluorenyldiphenylamine derivative represented by the general formula (1) is used.
It is preferable that the thin film has a thickness of 00 Å or less, particularly 300 Å to 1000 Å. On the other hand, as a material used for the electron transport layer 7, an oxadiazole compound or a perinone derivative represented by the following (Chemical Formula 2) is used, and has a thickness of 500Å to 3000Å, preferably 700Å to 1500Å.

[0014]

[Chemical 2]

The material used for the light emitting layer 5 is a dye showing strong fluorescence in a solid state, and compounds having various structures can be mentioned. Typical examples are shown below.

[0016]

[Chemical 3]

The thickness of the thin film of the luminous body is 500Å to 4000
Å, preferably 1000Å to 2000Å.

The hole transport layer and the electron transport layer are for transporting holes and electrons injected from the electrode to the light emitting layer, and are generated by recombination of the holes and electrons injected in the light emitting layer. Energy is used to generate the excited singlet state of the fluorescent molecule, and the excited singlet state emits fluorescence. Note that the electron transport layer 7 can be omitted when a material that easily injects electrons is selected as the material of the light emitting layer 5.

The organic electroluminescent device according to the present invention is the substrate 1
It can be manufactured by laminating each of the above-mentioned layers in a thin film state on the surface of. The film is formed by a vacuum vapor deposition method, a casting method, a Langmuir-Brosette method, or the like.

[0020]

In the organic electroluminescent device of the present invention, at least one of the organic thin film layers contains the compound represented by the general formula (1) as a hole transfer material, and is driven at a low voltage.
It has extremely good performance such as high emission intensity and high durability and is extremely valuable in practical use.

[0021]

The present invention will be described in more detail with reference to the following examples. Example 1 A 10 cm × 4 cm alkali-free borosilicate glass substrate having a thickness of 1.2 mm was washed with nitric acid, washed with distilled water, and dried.
A cathode was provided from the TO thin film.

Next, the following compound (2) was vacuum-deposited on this anode to form a hole transport layer having a thickness of 900Å.

[0023]

[Chemical 4]

Next, a compound (3) shown below was vapor-deposited on the hole transport layer to a thickness of 1000 Å to form a light emitting layer,

[0025]

[Chemical 5]

Further, the following oxadiazole compound (4) was vapor-deposited on the light emitting layer to a thickness of 1000 Å to provide an electron transport layer.

[0027]

[Chemical 6]

Finally, about 10 magnesium is deposited on the light emitting layer.
By vapor-depositing to a thickness of 00Å and forming a cathode, an electroluminescent device having a structure as shown in the drawing was produced. Then, a lead wire was drawn out from the cathode and connected to a DC power source by applying a voltage of 5 V or more, and bright blue light emission was observed. In addition,
The driving current at that time was 0.2 to 8 mA / cm ² .

Further, it was found that the continuous operation time until the emission intensity reached 80% of the initial value was 2250 hours and the element had good durability.

Examples 2 to 15 The same procedure as in Example 1 was carried out except that the compounds shown in Table 1 were used instead of the hole transport compound (2) and the light emitting compound (3) in Example 1. The electroluminescent elements of Examples 2 to 15 were obtained.

The characteristics of these electroluminescent devices are also shown in Table 1. In Table 1, the numbers 5 to 21 represent the following compounds.

[0032]

[Chemical 7]

[0033]

[Chemical 8]

[0034]

[Table 1]

Comparative Example 1 A device was manufactured in the same manner as in Example 1 except that the compound (22) was used in place of the hole transport material (2) in Example 1, and the characteristics such as emission intensity were found. It was almost the same as that of Example 1, but the durability was short at 450 hours and was poor.

[0036]

[Chemical 9]

Comparative Example 2 A device was prepared in the same manner as in Example 1 except that the compound (23) was used in place of the hole transfer material (2) in Example 1, and the characteristics such as emission intensity were Although it was almost the same as that of Example 1, the durability was short as 400 hours and was poor.

[0038]

[Chemical 10]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a typical electroluminescent device according to the present invention.

[Explanation of symbols]

 1 Substrate 2 Anode 3 Cathode 4 Power Supply 5 Light Emitting Layer 6 Hole Transport Layer 7 Electron Transport Layer

Claims (1)

[Claims] 1. Organizing one or more layers between two electrodes
In organic electroluminescent devices composed of
One layer of the following general formula (1) [In the formula, R¹Represents an alkyl group or an aralkyl group,
R², R³, R^FourAnd R ^FiveIs a hydrogen atom, alkyl group,
Indicates a coxy group or a halogen atom. ] Compound represented by
Organic electroluminescent element characterized by being a layer containing a substance
Child.