JP2997021B2 - Organic electroluminescence device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electroluminescence device, and more particularly, to an organic electroluminescence device including an organic compound as a phosphor.

BACKGROUND ART As this kind of organic electroluminescent element,
As shown in FIG. 2, an organic phosphor thin film 3 and an organic hole transport layer 4 which are made of an organic compound and stacked on each other are disposed between a metal electrode 1 as a cathode and a transparent electrode 2 as an anode. A layered structure, or as shown in FIG. 3, an organic electron transport layer 5, an organic phosphor thin film 3, and an organic hole transport layer 4 which are laminated between a metal electrode 1 and a transparent electrode 2 are arranged. A three-layer structure is known. Here, the organic hole transport layer 4 has a function of facilitating the injection of holes from the anode and a function of blocking electrons, and the organic electron transport layer 5 has a function of facilitating the injection of electrons from the cathode. I have.

In these organic electroluminescent devices,
A glass substrate 6 is disposed outside the transparent electrode 2, and excitons are generated by recombination of electrons injected from the metal electrode 1 and holes injected from the transparent electrode 2, and the excitons are radiated. Light is emitted in the process of deactivation, and this light is emitted outside via the transparent electrode 2 and the glass substrate 6.

However, in the conventional organic electroluminescence device having the above-described configuration, for example, a device having a tetraphenylbutadiene compound phosphor layer having only a phenyl group as a substituent and emitting a high-luminance light with a low applied voltage is used. However, since the phosphor is rapidly crystallized and has a short life, there is a problem in device fabrication.

SUMMARY OF THE INVENTION [Object of the Invention] The present invention has been made in order to satisfy the above-mentioned conventional needs, and provides an organic electroluminescent device which can efficiently emit an organic phosphor with high luminance and has a long life. The purpose is to provide.

[Structure of the Invention] In the organic electroluminescence device according to the present invention, the organic electroluminescence device has a structure in which an electron transport layer, a phosphor light emitting layer, and a hole transport layer, which are made of an organic compound and are laminated, are arranged between a cathode and an anode. In the device, the phosphor layer is a tetraphenylbutadiene compound represented by the following formula (A1): In the above formula (A1), R ₁ to R ₁₂ are hydrogen (excluding the case where R _{1 to} R ₁₂ are simultaneously hydrogen), an alkyl group, an alkoxyl group, and a phenyl which may have a substituent. R ₁₃ and R ₁₄ are hydrogen, an alkyl group, an alkoxyl group, a phenyl group which may have a substituent or a halogen.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the structure of an embodiment of the present invention, in which the same reference numerals are given to the same parts as in FIG. 2 and FIG.

In the figure, a metal having a small work function, for example, aluminum, magnesium, indium, silver, or an alloy thereof having a thickness of about 500 ° or more can be used for a metal electrode 1 serving as a cathode.

The transparent electrode 2 serving as the anode is made of a conductive material having a large work function, for example, indium tin oxide (ITO) having a thickness of about 1000 to 3000 °, tin oxide, or 800 to 15000 °.
A degree of gold can be used. When gold is used as the electrode material, the electrode 2 is in a translucent state.

Between the metal electrode 1 and the transparent electrode 2, an organic electron transport layer 5, an organic phosphor thin film 7, and an organic hole transport layer 4, which are sequentially stacked from the top of the figure, are arranged.

The organic hole transport layer 4 includes a triphenylamine derivative,
For example, a thin film of the compound of the following formula (I) is used.

The organic hole transport layer 4 further includes the following formulas (II) to (II).
A compound known as CTM (Carrier Transmitting Materials) of (XII) may be used.

As the organic phosphor thin film 7, a phosphor thin film containing a tetraphenylbutadiene compound is used. The thickness of the organic phosphor thin film 7 is set to 1 μm or less.

As the organic phosphor thin film 7, a tetraphenylbutadiene compound represented by the following structural formula (A1) is used.

Here, in the above (A1), R _{1 to} R ₁₂ are hydrogen (however, R _{1 to} R
Except when ₁₂ is simultaneously hydrogen. ), An alkyl group, an alkoxyl group, a phenyl group or a dialkylamino group which may have a substituent, and R ₁₃ and R ₁₄ may have a hydrogen, an alkyl group, an alkoxyl group, or a substituent Represents a phenyl group or a halogen. The tetraphenylbutadiene compound represented by the formula (A1) is represented by R _{1 to} R ₁₄ shown in Table _1.
The one having any of the set of substituents No. 1 to No. 25 is preferable.

As the electron transport layer 5, a Bu-PBD of the following formula (XIII)
[2- (4'-tert-Butylphenyl) -5- (bipheny
l) -1,3,4-oxadiazole] are preferably used, and compounds of the following formulas (XIV) to (XXIII) can also be used.

Effect of the Invention As described above, in the organic electroluminescence device according to the present invention, a configuration in which the electron transport layer, the phosphor light emitting layer, and the hole transport layer, which are made of an organic compound and are stacked on each other, is disposed between the cathode and the anode. The organic electroluminescence device of the above, wherein the phosphor phosphor layer is the above (A1)
Since the phosphor emitting layer is made of a thin film containing the tetraphenylbutadiene compound of the formula, the phosphor emitting layer can emit light efficiently and with high luminance over a long period of time in an amorphous state.

Example An organic electroluminescence device according to an example of the present invention was prepared and emitted light.

First, as Example 1, a glass substrate was prepared in which a transparent electrode of ITO, which is an anode, was formed in a thin film of 2000 mm. Aluminum or an alloy of magnesium and silver was used for the metal electrode serving as the cathode. For the electron transporting layer 5, Bu-PBD of the above formula (XIII) was used, and for the organic hole transporting layer 4, the triphenylamine derivative of the above formula (I) was used.

As the organic phosphor thin film 7, the above tetraphenylbutadiene compound is represented by the following formula (A2): The compound shown by was used.

In Example 2, the organic phosphor 7 is the above-mentioned tetraphenylbutadiene compound, and has the following formula (A3): A compound having the same structure as in Example 1 except for the above-mentioned compound was prepared.

In Example 3, the above-mentioned tetraphenylbutadiene compound was used as the organic phosphor 7 and represented by the following formula (A4): A compound having the same structure as in Example 1 except for the above-mentioned compound was prepared.

In Example 4, the organic phosphor 7 is the above-mentioned tetraphenylbutadiene compound, and has the following formula (A5): A compound having the same structure as in Example 1 except for the above-mentioned compound was prepared.

Regarding Examples 1 to 4, the film forming conditions such as the degree of vacuum, the deposition rate and the film thickness when forming the hole transport layer, the phosphor thin film and the cathode are as shown in Table 1. Voltage applied to the organic electroluminescent devices of
The emission characteristics obtained by applying 20 V are also shown.

Further, as a result of comparing both phosphor surfaces of the organic electroluminescent device of the phosphor layer in the third embodiment and the conventional tetraphenylbutadiene compound phosphor layer having only a phenyl group as a substituent, by electron micrographs, No. 3 shows that the crystallization does not progress and the surface (interface) is smoother, and the device of Example 3 maintains a uniform light emitting state, whereas the conventional device emits light of the crystallized portion. Was short-lived.

[Brief description of the drawings]

FIG. 1 is a structural view showing an embodiment of the present invention, FIG. 2 and FIG.
FIG. 1 is a structural view showing a conventional example. Description of Signs of Main Parts 1 ... Metal electrode (cathode) 2 ... Transparent electrode (anode) 4 ... Organic hole transport layer 6 ... Glass substrate 7 ... Organic phosphor thin film 5 ... Organic electron transport layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshikazu Sato 3-26-8 Shimo, Kita-ku, Tokyo (72) Inventor Masaharu Nomura 3-26-8 Shimo, Kita-ku, Tokyo (56) References JP Hei 4-88079 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09K 11/06 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (6)

(57) [Claims] 1. An organic electroluminescent device comprising an organic compound, wherein an electron transport layer, a phosphor layer and a hole transport layer, which are laminated on each other, are arranged between a cathode and an anode. Tetraphenylbutadiene compound represented by the formula (A1) Wherein, in the above formula (A1), R ₁ to R _{12 each} have a hydrogen (except when R _{1 to} R ₁₂ are simultaneously hydrogen), an alkyl group, an alkoxyl group, and a substituent. R ₁₃ and R ₁₄ are hydrogen, an alkyl group, an alkoxyl group, an optionally substituted phenyl group or halogen (provided that both R ₁₃ and R ₁₄ are An organic electroluminescent device characterized by the fact that hydrogen does not have two phenyl nuclei having no alkoxyoxyl group among the four phenyl nuclei). 2. The method according to claim 1, wherein the tetraphenylbutadiene compound is represented by the following formula (A2): The organic electroluminescence device according to claim 1, wherein the compound is a compound represented by the following formula: 3. The compound according to claim 1, wherein the tetraphenylbutadiene compound is represented by the following formula (A3): The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is a compound represented by the following formula: 4. The method of claim 1, wherein the tetraphenylbutadiene compound has the following formula (A4): The organic electroluminescence device according to claim 1, wherein the compound is a compound represented by the following formula: 5. The method according to claim 1, wherein the tetraphenylbutadiene compound is represented by the following formula (A5): The organic electroluminescence device according to claim 1, wherein the compound is a compound represented by the following formula: 6. The compound according to claim 1, wherein the tetraphenylbutadiene compound is represented by the following formula (A6): The organic electroluminescence device according to claim 1, wherein the compound is a compound represented by the following formula: