JP3065125B2 - Organic electroluminescent device - Google Patents

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 converting electric energy into light energy.

[0002]

2. Description of the Related Art As an electroluminescent device, a device having a structure in which inorganic compound thin films are laminated has been known, and a part thereof has already been put to practical use. Although these inorganic thin film laminated type electroluminescent elements have the advantage of high emission luminance, the driving voltage is as high as 100 V to 200 V, and the high voltage endurance driving I
It has disadvantages such as the necessity of C, the low degree of freedom in hue selection due to the emission line emission, and the large power consumption.

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.I. Saito, JP
n. J. Appl. Phys. , 27 volumes, 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. Such an organic thin-film laminated electroluminescent element has a wider range of choices of emission wavelengths because there are many types of light-emitting materials than an inorganic thin-film laminated electroluminescent element. It has attracted a great deal of attention because sufficient luminance can be obtained and the area can be easily increased. However, at present, there is a problem in durability performance that the light emission luminance gradually decreases when used for a long time.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electroluminescent device having good light fastness and high luminance driven at a low voltage.

[0005]

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

That is, the present invention provides an organic electroluminescent device comprising one or more layers of an organic compound between two electrodes, wherein at least one layer is a hole transport agent represented by the following general formula (1):

[0007]

Embedded image

[In the formula, R ¹ represents an alkyl group or an aralkyl group, and R ² , R ³ , R ⁴ and R ⁵ represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. Resistance, characterized in that] a layer containing a compound represented by
It is an organic electroluminescent device with excellent durability .

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

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 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 supply, 5 is a light emitting layer,
6 is a hole transport layer, and 7 is an electron transport layer.

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

The anode 2 is paired with the cathode 3 and applies an electric field to each of the layers constituting the organic electroluminescent device. The anode 2 is made of nickel, gold, platinum, palladium tin oxide, indium tin oxide (ITO) or the like. Are preferred. The film thickness is 50 to 1000 °, but in the case of an opaque electrode, it needs to be 300 ° 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 to set the thickness of the thin film to not more than 00 °, especially 300 to 1000 °. On the other hand, as a material used for the electron transport layer 7, an oxadiazole compound or a perinone derivative shown below (Chemical Formula 2) is used, and has a thickness of 500 to 3000, preferably 700 to 1500.

[0014]

Embedded image

The material used for the light-emitting layer 5 is a dye exhibiting strong fluorescence in a solid state, and includes compounds having various structures. Representative examples are shown below.

[0016]

Embedded image

The thickness of the thin film of the luminous body is 500-4000.
{, Preferably 1000 to 2000}.

The hole transporting layer and the electron transporting layer are for transporting holes and electrons injected from the electrode to the light emitting layer, and the holes and electrons injected in the light emitting layer are recombined and generated. The energy is used to generate the excited singlet state of the fluorescent molecule, and emits fluorescence from this excited singlet state. When a material into which electrons are easily injected is selected as the material of the light emitting layer 5, the electron transport layer 7 can be omitted.

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

[0020]

According to 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 transporting agent,
It has extremely good performance such as high luminous 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 An alkali-free borosilicate glass substrate having a thickness of 1.2 mm and a size of 10 cm × 4 cm was washed with nitric acid, washed with distilled water, dried, and then dried on the glass substrate by electron beam evaporation to a thickness of 500 mm.
A cathode was provided from a TO thin film.

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

[0023]

Embedded image

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

[0025]

Embedded image

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

[0027]

Embedded image

Finally, about 10 mg of magnesium was formed on the light emitting layer.
The cathode was formed by vapor deposition to a thickness of 00 ° to produce an electroluminescent device having a structure as shown in the figure. Then, when the anode was connected to a DC power supply by drawing a lead wire from the cathode and applying a voltage of 5 V or more, bright blue light emission was observed. In addition,
The driving current at that time was 0.2 to 8 mA / cm ² .

Further, the continuous operation time until the luminous intensity became 80% of the initial value was 2250 hours, which proved that the device had good durability.

Examples 2 to 15 The same procedures as in Example 1 were carried out except that the compounds shown in Table 1 were used in place of the hole transport compound (2) and the luminescent compound (3). The electroluminescent devices of Examples 2 to 15 were obtained.

The characteristics of these electroluminescent devices are also shown in Table 1. In addition, the number of 5-21 in Table 1 shows the following compounds.

[0032]

Embedded image

[0033]

Embedded image

[0034]

[Table 1]

Comparative Example 1 A device was produced in the same manner as in Example 1 except that the compound (22) was used in place of the hole transporting agent (2). Although almost the same as Example 1, the durability was as short as 450 hours, and was poor.

[0036]

Embedded image

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 transporting agent (2) in Example 1. Although almost the same as Example 1, the durability was as short as 400 hours.

[0038]

Embedded image

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Cathode 4 Power supply 5 Light emitting layer 6 Hole transport layer 7 Electron transport layer

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 33/00-33/28 CAPLUS (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. An organic electroluminescent device comprising one or more layers of an organic compound between two electrodes, wherein at least one layer is a hole transporting agent, represented by the following general formula (1): Wherein R ¹ represents an alkyl group or an aralkyl group;
R ² , R ³ , R ⁴ and R ⁵ represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. An organic electroluminescent device having excellent durability , characterized in that it is a layer containing the compound represented by the following formula: